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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..6833f05 --- /dev/null +++ b/.gitattributes @@ -0,0 +1,3 @@ +* text=auto +*.txt text +*.md text diff --git a/33936-8.txt b/33936-8.txt new file mode 100644 index 0000000..72f9443 --- /dev/null +++ b/33936-8.txt @@ -0,0 +1,8723 @@ +The Project Gutenberg EBook of Clever Hans, by Oskar Pfungst + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Clever Hans + (The horse of Mr. Von Osten): A contribution to experimental + animal and human psychology + +Author: Oskar Pfungst + +Translator: Carl L. Rahn + +Release Date: October 11, 2010 [EBook #33936] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK CLEVER HANS *** + + + + +Produced by Audrey Longhurst, Linda Hamilton and the Online +Distributed Proofreading Team at http://www.pgdp.net + + + + + + + + + + [Illustration: CLEVER HANS] + + + + + CLEVER HANS + + (THE HORSE OF MR. VON OSTEN) + + _A CONTRIBUTION TO EXPERIMENTAL + ANIMAL AND HUMAN + PSYCHOLOGY_ + + BY + OSKAR PFUNGST + + WITH AN INTRODUCTION BY PROF. C. STUMPF, + AND ONE ILLUSTRATION AND FIFTEEN FIGURES + + TRANSLATED FROM THE GERMAN + BY + CARL L. RAHN + _Fellow in Psychology in the University of Chicago_ + + WITH A PREFATORY NOTE BY + JAMES R. ANGELL + _Professor of Psychology in the University of Chicago_ + + [Illustration] + + NEW YORK + HENRY HOLT AND COMPANY + 1911 + + + + + COPYRIGHT, 1911, + BY + HENRY HOLT AND COMPANY + + + + +PREFATORY NOTE + +[BY JAMES R. ANGELL] + +_The University of Chicago_ + + +It gives me great pleasure to accept the invitation of the publishers to +write a word of introduction for Mr. Rahn's excellent translation of +"Der Kluge Hans", a book which in the original has been but little known +to American readers. The present wave of interest in animal life and +behavior renders its appearance peculiarly appropriate. + +No more remarkable tale of credulity founded on unconscious deceit was +ever told, and were it offered as fiction, it would take high rank as a +work of imagination. Being in reality a record of sober fact, it verges +on the miraculous. After reading Mr. Pfungst's story one can quite +understand how sedate and sober Germany was for months thrown into a +turmoil of newspaper debate, which for intensity and range of feeling +finds its only parallel in a heated political campaign. That the subject +of the controversy was the alleged ability of a trained horse to solve +complex arithmetical problems may excite gaiety and even derision, until +one hears the details. Scientists and scholars of the highest eminence +were drawn into the conflict, which has not yet wholly subsided, +although the present report must be regarded as quite final in its +verdict. + +As for Hans himself, he has become the prototype of a host of less +distinguished imitators representing every level of animal life, and +when last heard from he was still entertaining mystified audiences by +his accomplishments. + +But the permanent worth of the book is not to be found in its record of +popular excitement, interesting as that is. It is a document of the very +first consequence in its revelation of the workings of the animal mind +as disclosed in the horse. Animal lovers of all kinds, whether +scientists or laymen, will find in it material of greatest value for the +correct apprehension of animal behavior. Moreover, it affords an +illuminating insight into the technique of experimental psychology in +its study both of human and animal consciousness. Finally, it contains a +number of highly suggestive observations bearing on certain aspects of +telepathy and muscle-reading. All things considered, it may fairly be +said that few scientific books appeal to so various a range of interests +in so vital a way. + +Readers who wish to inform themselves of all the personal circumstances +in the case may best read the text just as it stands. Those who desire +to get at the pith of the matter without reference to its historical +settings, may be advised to omit the Introduction by Professor Stumpf of +the University of Berlin, together with supplements II, III and IV. + + + + +CONTENTS + + + PAGE + PREFATORY NOTE (By JAMES R. ANGELL) v + + INTRODUCTION (By C. STUMPF) 1 + + + CHAPTER + I. THE PROBLEM OF ANIMAL CONSCIOUSNESS AND "CLEVER HANS" 15 + + II. EXPERIMENTS AND OBSERVATIONS 30 + + III. THE AUTHOR'S INTROSPECTIONS 88 + + IV. LABORATORY TESTS 102 + + V. EXPLANATION OF THE OBSERVATIONS 141 + + VI. GENESIS OF THE REACTION OF THE HORSE 212 + + CONCLUSION 240 + + + SUPPLEMENTS: + + I. MR. VON OSTEN'S METHOD OF INSTRUCTION (By C. STUMPF) 245 + + II. THE REPORT OF SEPTEMBER 12th, 1904 253 + + III. AN ABSTRACT FROM THE RECORDS OF THE + SEPTEMBER-COMMISSION 255 + + IV. THE REPORT OF DECEMBER 9th, 1904 261 + + + TABLE OF REFERENCES 267 + + + + +INTRODUCTION + +[BY C. STUMPF] + + +A horse that solves correctly problems in multiplication and division by +means of tapping. Persons of unimpeachable honor, who in the master's +absence have received responses, and assure us that in the process they +have not made even the slightest sign. Thousands of spectators, +horse-fanciers, trick-trainers of first rank, and not one of them during +the course of many months' observations are able to discover any kind of +regular signal. + +That was the riddle. And its solution was found in the unintentional +minimal movements of the horse's questioner. + +Simple though it may seem, the history of the solution is nevertheless +quite complex, and one of the important incidents in it is the +appearance of the zoölogist and African traveler, Schillings, upon the +scene, and then there is the report of the so-called Hans-Commission of +September 12, 1904. And finally there is the scientific investigation, +the results of which were published in my report of December 9, 1904. + +After a cursory inspection during the month of February, I again called +upon Mr. von Osten in July, and asked him to explain to Professor +Schumann and me just what method he had used in instructing the horse. +We hoped in this way to gain a clue to the mechanism of Hans's feats. +The most essential parts of the information thus gleaned are summarized +in Supplement I. Mr. Schillings came into the courtyard for the first +time about the middle of July. He came as skeptical as everyone else. +But after he, himself, had received correct responses, he too became +convinced, and devoted much of his time to exhibiting the horse, and +daily brought new guests. To be perfectly frank, at the time this seemed +to us a disturbing factor in the investigation, but now we see that his +intervention was a link in the chain of events which finally led to an +explanation. For it was through him that the fact was established beyond +cavil, that the horse was able to respond to strangers in the master's +absence. Heretofore, this had been noted only in isolated cases. Since +it could not be assumed that a well-known investigator should take it +upon himself to mislead the public by intentionally giving signs, the +case necessarily from that time on appeared in the eyes of others in a +light quite different from that in which ordinary circus-tricks would +appear, to which it bore such a striking external resemblance. No matter +how this state of affairs may have arisen in the course of years, no +matter how it might eventually be explained,--the quality of the +extraordinary would necessarily attach itself to this particular case, +as it did. + +Of course, to many persons in the interested public the result was +merely that Schillings, also, was placed in the category of deceivers. +On the other hand there were reputable scientists who could not dispose +of the matter in that fashion, and these now openly took their stand +with Schillings and declared that they believed in the horse's ability +to think. Zoölogists especially, saw in von Osten's results evidence of +the essential similarity between the human and the animal mind, which +doctrine has been coming more and more into favor since the time of +Darwin. Educators were disposed to be convinced, on account of the +clever systematic method of instruction which had been used and which +had not, till then, been applied in the education of a horse. In +addition, there were many details which, it seemed, could not be +explained in any other way. So far as I myself was concerned, I was +ready to change my views with regard to the nature of animal +consciousness, as soon as a careful examination would show that nothing +else would explain the facts, except the assumption of the presence of +conceptual thinking. I had thought out the process hypothetically, i. e., +how one might conceive of the rise of number concepts and arithmetical +calculation along the peculiar lines which had been followed in Hans's +education, and on the basis of the assumption that the beginnings of +conceptual thinking are present in animals. Also, I had too much faith +in human nature to fear lest nothing peculiarly human should remain +after the art of handling numbers should be shown to be common property +with the lower forms. But under no circumstances would I have undertaken +to make a public statement in favor of any particular view in this +extraordinary case, before a thorough investigation, in accordance with +scientific principles, had been made. I expressed this sentiment at the +time, and recommended the appointment of an investigating commission (in +the "Tag" of September 3, 1904). + +The purpose of this commission was misunderstood, and therefore many +were disappointed with the report which it published, (Supplement II). +Some had been expecting a positive conclusive explanation; the +commission recommended further investigation. Some had asked for a +solution of the question whether or not the horse was able to think; the +commission maintained neither the one, nor the other. Some had indicated +as the main condition of a satisfactory investigation, that both Mr. von +Osten and Mr. Schillings be excluded from the tests; this was not done. + +But the commission--which, by the way, did not give itself this name, +since it had been delegated by no one--undoubtedly had the right to +formulate its problem as it saw fit, and this was carefully expressed at +the beginning of its report as follows: "The undersigned came together +for the purpose of investigating the question whether or not there is +involved in the feats of the horse of Mr. von Osten anything of the +nature of tricks, that is, intentional influence or aid on the part of +the questioner." It was this preliminary question, and not whether or +not the horse could think, which the commission intended to answer. They +proposed to act as a sort of court of honor for the two gentlemen who +had been attacked. It is only in this light that even the _raison +d'être_ of this body can be understood; for a scientific commission +composed of thirteen men, possessed of varying degrees of scientific +preparation, would have been an absurd travesty, and it will readily be +seen why the two men, who had been attacked, should not be excluded, +since it was they, and primarily Mr. von Osten, upon whom the +observations were to be made. + +To be sure the commission did go one step beyond that which it had +proposed to itself, since it added that it believed that unintentional +signs of the kind which are at present familiar, were also excluded. +This led many to the unwarranted conclusion that the commission had +declared that Hans was able to think. Whereas the thing which might have +been logically suggested was that instead of the assumption of the +presence of independent thinking, the commission may have had in mind +unintentional signs of a kind hitherto unknown. I explained this to a +reporter of the "Frankfurter Zeitung" (Mr. A. Gold), who had come to me +for information, and in his article he made this hypothesis appear as +the most probable one.[A] Certain statements of the circus-manager +Busch, who speaks of a 'connection' of some sort, go to show that other +members of the commission held to the view just stated. + + [Footnote A: "Frankfurter Zeitung" of September 22, 1904: + "Concerning the question whether the horse was given some sort of + aid, Professor Stumpf expressed himself freely. He said: 'We were + careful to state in our report that the intentional use of the + (actual) means of training, on the part of the horse's teacher, is + out of the question, ... nor are there involved any of the known + kinds of unconscious, involuntary aids. Our task was completed after + we had ascertained that no tricks or aids of the traditional sort + were being employed'." After some remarks on unconscious habituation + and self-training on the part of animals, the writer arrives at the + conclusion that "the horse of Mr. von Osten has been educated by its + master in the most round-about way, in accordance with a method + suited for the development of human reasoning powers, hence in all + good faith, to give correct responses by means of tapping with the + foot. But what the horse really learned by this wearisome process + was something quite different, something that was more in accord + with his natural capacities,--he learned to discover by purely + sensory aids which are so near the threshold that they are + imperceptible for us and even for the teacher, when he is expected + to tap with his foot and when he is to come to rest."] + +But how did it come to pass that the commission should deny completely +the presence of intentional signals, while, as regards the unintended, +it excluded only those which were of the known sort? The report clearly +shows that the decision as to the absence of voluntary signals was +based not merely upon the fact that no such signals had been detected by +the most expert observers, but also upon the character of the two men +who exhibited the horse, upon their behavior during the entire period, +and upon the method of instruction which Mr. von Osten had employed. In +the case of unintentional signs, on the other hand, one had to deal with +the fact with which physiologists and experimental psychologists are +especially familiar, viz., that our conscious states, without our +willing it--indeed, even in spite of us--are accompanied by bodily +changes which very often can be detected only by the use of extremely +fine graphic methods. The following is a more general instance: every +mother, who detects the lie or divines the wish in the eyes of the +child, knows that there are characteristic changes of facial expression, +which are, nevertheless, very difficult of definition.[B] + + [Footnote B: "From the productions of the 'thought-readers' we see + how slight and seemingly insignificant the unconscious movements may + be, which serve as signs for a sensitive re-agent. But in this case + no contact is necessary. There would have to be some sort of visible + or audible expression on the part of the questioner. No proof for + this has as yet been advanced." + + How any one possessing the power of logical thought could possibly + infer from these words of mine (published in the above-mentioned + article in the "Tag"), that I denied the possibility of the + occurrence of visual signs, is to me incomprehensible. What I did + deny, and still deny, is that up to that time any had been proven to + occur.] + +The commission did not even maintain or believe that unintentional signs +within the realm of the senses known to us, were to be excluded. +Professor Nagel and I would never have subscribed to any such +conclusion. The sentence in question, therefore, could only be +interpreted as follows: that signals of the kind that are used +intentionally in the training of horses, could not have occurred even +as unintended signs, for otherwise Mr. Busch would have detected them. +And in order to be observed by him it was immaterial whether they were +given purposely or not. The same signs, therefore, which as a result of +his observations were declared not to be present, could not be assumed +to be involved as unintentional. + +For my part I am ready to confess that at this time I did not expect to +find the involuntary signals, if any such were involved, in the form of +movements. I had in mind rather some sort of nasal whisper such as had +been invoked by the Danish psychologist A. Lehmann, in order to explain +certain cases of so-called telepathy. I could not believe that a horse +could perceive movements which escaped the sharp eyes of the +circus-manager. To be sure, extremely slight movements may still be +perceived after objects at rest have become imperceptible. But one would +hardly expect this feat on the part of an animal, who was so deficient +in keenness of vision, as we have been led, by those of presumably +expert knowledge, to believe of the horse,--one would expect it all the +less because Mr. von Osten and Mr. Schillings would move hither and +thither in most irregular fashion while the horse was going through his +tapping, and would therefore make the perception of minute movements all +the more difficult. + +Nor was there anything in the exhibitions given at the same time in a +Berlin vaudeville by the mare "Rosa," which might have shattered this +belief. For, in the case of this rival of Hans, the movements involved +were comparatively coarse. The closing signal consisted in bending +forward on the part of the one exhibiting the mare, while up to that +point he had stood bolt upright. Most persons were not aware of this, +because this change in posture cannot be noticed from the front. I +happened to sit to the side and caught the movement every time. It was +the same that was noted by Dr. Miessner, another member of the +commission, (see page 256), but concerning which he did not give me a +more complete account. Later I learned through Professor Th. W. +Engelmann that the very same movement was employed not long ago, for +giving signals to a dog exhibited at Utrecht. This particular movement +is very well adapted to commercial purposes, since the spectator always +tries to view the performance from a point as nearly in front of the +animal and its master as possible, thus making the detection of the +trick all the more difficult. + +The details of the various experiments made by this commission are given +in an excerpt from the records kept by Dr. von Hornbostel, which I +showed to a small group of persons a few days after the 12th of +September (Supplement III). At that time none of the particulars was +published, because the commission wished to wait until some positive +statement might be made. The public was merely to be assured that a +group of reputable men, from different spheres of life, who could have +no purpose in hazarding their reputation, believed that the case was one +worthy of careful investigation. + +I left Berlin on September 17th and did not return until October 3d. In +the meantime Mr. Schillings continued the investigation, and was +assisted in part by Mr. Oskar Pfungst, one of my co-workers at the +Psychological Institute. For the first time a number of tests were now +made in which neither the questioner, nor any of those present knew the +answer to the problem. Such tests naturally were the first steps toward +a positive investigation. The results were such that Mr. Schillings was +led to replace his hypothesis of independent conceptual thinking by one +of some kind of suggestion. In this he was strengthened somewhat by +having noted the fact that in his questions which he put to the horse, +he might proceed as far as to ask the impossible. He has always been +ready to offer himself in the tests which have been undertaken since +then. + +On October 13, 1904, together with the two gentlemen mentioned in the +beginning of my report, I began my more detailed investigation, and +finished on November 29. We worked for several hours on the average of +four times each week. I take this opportunity of giving expression of +the recognition which is due to the two gentlemen. They were ready to go +to the courtyard in all kinds of weather, at times they went without me, +and they always patiently discussed the order and method of the +experiments and the results. Dr. von Hornbostel had the important task +of keeping the records, and Mr. Pfungst undertook the conduct of the +experiments. It was he, who, soon after the blinder-tests disclosed the +necessary presence of visual signs, discovered the nature of these +signs. Without him we might have shown the horse to be dependent upon +visual stimuli in general, but we never would have been able to gain +that mass of detail, which makes the case valuable for human psychology. +But I am tempted to praise not merely his patience and skill, but also +his courage. For we must not believe that Mr. von Osten's horse was a +"perfectly gentle" animal. If he stood untied and happened to be excited +by some sudden occurrence, he would make that courtyard an unsafe place, +and both Mr. Schillings and Mr. Pfungst suffered from more than one +bite. In this connection I would also express my obligations to Count +Otto zu Castell-Rüdenhausen, for his frequent intercession on our behalf +with the owner of the horse, and for his many evidences of good-will and +helpfulness. + +After the publication of this report (Supplement IV), there was still +some further discussion of the case in societies of various kinds and in +the press, but no important objections were raised. A hippologist +thought that men of his calling should have been consulted, a +telepathist believed that telepathists should have been called in. There +was also some further talk of suggestion, will-transference, +thought-reading and the occult, but no attempt was made to elucidate +these vague terms with reference to their application to the case in +hand. Others adhered to the old cry of "fraud," for a share of which Mr. +Pfungst now fell heir. There were a few who felt it incumbent upon +themselves to preserve their 'priority,' and therefore stated with a +show of satisfaction that I had finally 'confessed' myself to hold their +respective points of view. As if there were anything like "confessions" +in science! As if mere affirmations, even though sealed and deposited in +treasure vaults, had any value with reference to a case in which every +manner of supposition had been advanced in lieu of explanation. Why did +they wait so long, if they had convincing proof for their position? + +And finally there were disappointed Darwinists who expressed fear lest +ecclesiastical and reactionary points of view should derive favorable +material from the conclusions arrived at in my report. Needless fear. +For lovers of truth it must always remain a matter of inconsequence +whether anyone is pleased or displeased with the truth, and whether it +is enunciated by Aristotle or Haeckel. + +Mr. von Osten, however, continued to exhibit Hans, and is probably doing +so still, but in what frame of mind, I dare not judge. The spectators +continue to look on, they are doubly alert to catch movements, and many +of them have learned from Mr. Schillings what kind of movements they are +to expect. But these "initiated" ones regularly return and declare that +there is nothing in the movements and that they simply could not +discover any aids given to the horse. Nothing can so well show how +difficult the case is, and how great the need of a thorough exposition +of the whole matter, than the account given in the following pages of +Mr. Pfungst. Its publication has been delayed on account of the +additional tests made in the laboratory, but we have reason to suppose +that through these additional tests the work has gained in permanent +value. Experimental psychologists will perhaps be greatly interested in +the graphic registration of the minute involuntary movements which +accompany the thought process, and in the artificial association of a +given involuntary movement with a given idea. Likewise the tests on +sense-perception in horses, which have led to essential changes in +hitherto current views, and the critical review of the comprehensive +literature on similar achievements of other animals, will be welcomed by +many. + +Before closing these introductory remarks, I would make one more +statement concerning Mr. von Osten. The reader will notice that the +judgment passed upon him in this treatise is placed at the end, whereas +in the report of the commission it came first. This was brought about by +the change that was made in the way of stating the problem. Then the +question discussed was whether 'tricks' were involved; now the question +is: What is the mechanism of the process? The question of the good faith +of the master was taken up once more only because the facts that were +brought to light by the later experimentation seemingly brought forward +new grounds for distrust. But by placing this discussion toward the end +of our report we wished to indicate that everything that is said of the +present status of facts, is quite independent of the view taken +concerning Mr. von Osten. Even assuming that the horse had been +purposely trained by him to respond to this kind of signal, the case +would still deserve a place in the annals of science. For visual signs, +planned and practiced so that they could not only be more readily +perceived by the animal than by man, but could be transferred from their +inventor to others without any betrayal of the secret,--this would be an +extraordinary invention, and Mr. von Osten would then be a fraud, but +also a genius of first rank. + +In truth he probably was neither, but I was brief in my report, for +otherwise I would have been obliged to go into more detail than the case +warranted. And a judgment passed upon a human personality is quite a +different matter from a judgment upon a horse. If it is unscientific to +make unqualified statements concerning a horse after the performance of +only a few experimental tests, it is certainly an unwarranted thing to +pass a moral judgment upon a man upon the basis of meagre material. +Anyone who would assume the rôle of judge should bear in mind that here +too we have more than a hundredfold the material which they could bring +forward, and among it some which, if taken alone, would be more +unfavorable than any that they had. But here all things should be +weighed together, and not in isolation. A former instructor of +mathematics in a German gymnasium, a passionate horseman and hunter, +extremely patient and at the same time highly irrascible, liberal in +permitting the use of the horse for days at a time and again tyrannical +in the insistence upon foolish conditions, clever in his method of +instruction and yet at the same time possessing not even the slightest +notion of the most elementary conditions of scientific procedure,--all +this, and more, goes to make up the man. He is fanatic in his +conviction, he has an eccentric mind which is crammed full of theories +from the phrenology of Gall to the belief that the horse is capable of +inner speech and thereby enunciates inwardly the number as it proceeds +with the tapping. From theories such as these, and on the basis of all +sorts of imagined emotional tendencies in the horse, he also managed to +formulate an explanation for the failure of the tests in which none of +the persons present knew the answer to the problem given the horse, and +also for the failure of those tests in which the large blinders were +applied. And he would often interfere with or hinder other tests which, +according to his point of view, were likely to lead us astray. And yet, +when the first tests with the blinders did turn out as unmistakably +sheer failures, there was such genuine surprise, such tragi-comic rage +directed against the horse, that we finally believed that his views in +the matter would be changed beyond a doubt. "The gentlemen must admit," +he said at the time, "that after seeing the objective success of my +efforts at instruction, I was warranted in my belief in the horse's +power of independent thought." Nevertheless, upon the following day he +was as ardent an exponent of the belief in the horse's intelligence as +he ever had been. + +And finally, after I could no longer keep from him the results of our +investigation, I received a letter from him in which he forbade further +experimentation with the horse. The purpose of our inquiries, he said, +had been to corroborate his theories. On account of his withdrawal of +the horse a few experimental series unfortunately could not be +completed, but happily the major portion of our task had been +accomplished. + + + + +THE HORSE OF MR. VON OSTEN + +CHAPTER I + +THE PROBLEM OF ANIMAL CONSCIOUSNESS AND "CLEVER HANS" + + +If we would appreciate the interest that has been aroused everywhere by +the wonderful horse solving arithmetical problems, we must first +consider briefly the present state of the problem of animal +consciousness.[C] Animal consciousness cannot be directly gotten at, and +the psychologist must therefore seek to appreciate it on the basis of +the animal's behavior and with the assistance of conceptions borrowed +from human psychology. Hence it is that animal psychology rests upon +uncertain foundations with the result that the fundamental principles +have been repeatedly questioned and agreement has not yet been attained. +The most important of these questions is, "Does the animal possess +consciousness, and is it like the human consciousness?" Comparative +psychologists divide into three groups on this question. + + [Footnote C: Since the present treatise is intended for the larger + public, this brief resumé will probably be welcome to many.] + +The one group allows consciousness to the lower forms, but emphasizes +the assertion that between the animal and the human consciousness there +is an impassable gap. The animal may have sensations and memory-images +of sensations which may become associated in manifold combinations. Both +sensations and memory images are believed to be accompanied by +conditions of pleasure and of pain (so-called sensuous feelings), and +these in turn, become the mainsprings of desire. The possession of +memory gives the power of learning through experience. But with this, +the inventory of the content of animal consciousness is exhausted. The +ability to form concepts[D] and with their aid to make judgments and +draw conclusions is denied the lower forms. All the higher intellectual, +ĉsthetic and moral feelings, as well as volition guided by motives, are +also denied. Among the ancients this view was held by Aristotle and the +Stoics; and following them it was taught by the Christian Church. It +pervaded all mediĉval philosophy, which grew out of the teachings of +Aristotle and the Church. It is this philosophy, in the form of +Neo-Thomism, which still obtains in the Catholic world. + + [Footnote D: Ideas are copies of former sensations, feelings and + other psychic experiences and retain also the accidental signs which + belonged to those earlier experiences. They are images in the + concrete, such as the memory of a certain horse in a certain + definite situation ... say a well fed, long-tailed one standing at a + manger. A concept, on the other hand, is a mental construct which + has its rise in ideas, or memory-images, in that their essential + characteristics are abstracted. For this reason the concept has not + a definite image-content. (Thus the thought of "horse" in general, + is a concept. Not so the thought of a certain individual + horse,----that is an idea, with a definite image-content.)] + +During the 17th century, even though temporarily, another conception of +the consciousness of lower forms came to prevail and was introduced by +Descartes, the "Father" of modern philosophy. Far more radical than the +earlier conception, it denied to animals not only the power of abstract +thought, but every form of psychic life whatever, and reduced the lower +form to a machine, which automatically reacted upon external stimuli. +This daring view, however, prevailed for only a comparatively short +period; but owing to the opposition which it aroused, it gave a +tremendous impetus to the study of animal consciousness. Most of the +great philosophers following Descartes, such as Locke, Leibniz, Kant, +and Schopenhauer, however greatly they may have differed in other +points, in this one returned to the Aristotelian point of view. + +A third belief avers that animal and human consciousness do not differ +in essentials, but only in degree. This conclusion is regularly arrived +at by those who regard so-called abstract thought itself, as simply a +play of individual sensations and sensation-images, as did the French +and British associationists (Condillac and the Mills). The superiority +of man accordingly consisted in his ability to form more intricate +ideational complexes. Again, this conception of the essential similarity +of the human and the animal psyche has also always been arrived at by +the materialists (from Epicurus to C. Vogt and Büchner) who impute +reason to the animal form as well as to man. The same position is, +furthermore, taken by the evolutionists, including those who do not +subscribe to the doctrines of materialism. It has almost become dogma +with them that there exists an unbroken chain of psychic life from the +lowest protozoa to man. Haeckel, preëminently, though not always +convincingly, sought to establish such a graded series and thus to +bridge the chasm between the human and the animal consciousness. + +Two tendencies, therefore, are discernible in animal psychology. The +one seeks to remove the animal psyche farther away from the human, the +other tries to bring the two closer together. It is undoubtedly true +that many acts of the lower forms reveal nothing of the nature of +conceptual thinking. But that others might thus be interpreted cannot be +denied. But need they be thus interpreted?--There lies the dispute. A +single incontrovertible fact which would fulfil this demand, [i.e., +proof of conceptual thinking], would, at a stroke, decide the question +in favor of those who ascribe the power of thought to the lower forms. + +At last the thing so long sought for, was apparently found: A horse that +could solve arithmetical problems--an animal which, thanks to long +training, mastered not merely rudiments, but seemingly arrived at a +power of abstract thought and which surpassed, by far, the highest +expectations of the greatest enthusiast. + +And now what was it that this wonderful horse could do? The reader may +accompany us to an exhibition which was given daily before a select +company at about the noon hour in a paved courtyard surrounded by high +apartment houses in the northern part of Berlin. No fee was ever taken. +The visitor might walk about freely and if he wished, might closely +approach the horse and its master, a man between sixty and seventy years +of age. His white head was covered with a black, slouch hat. To his left +the stately animal, a Russian trotting horse, stood like a docile pupil, +managed not by means of the whip, but by gentle encouragement and +frequent reward of bread or carrots. He would answer correctly, nearly +all of the questions which were put to him in German. If he understood a +question, he immediately indicated this by a nod of the head; if he +failed to grasp its import, he communicated the fact by a shake of the +head. We were told that the questioner had to confine himself to a +certain vocabulary, but this was comparatively rich and the horse +widened its scope daily without special instruction, but by simple +contact with his environment. His master, to be sure, was usually +present whenever questions were put to the horse by others, but in the +course of time, he gradually responded to a greater and greater number +of persons. Even though Hans did not appear as willing and reliable in +the case of strangers as in the case of his own master, this might +easily be explained by the lack of authoritativeness on their part and +of affection on the part of Hans, who for the last four years had had +intercourse only with his master. + +Our intelligent horse was unable to speak, to be sure. His chief mode of +expression was tapping with his right forefoot. A good deal was also +expressed by means of movements of the head. Thus "yes" was expressed by +a nod, "no" by a deliberate movement from side to side; and "upward," +"upper," "downward," "right," "left," were indicated by turning the head +in these directions. In this he showed an astonishing ability to put +himself in the place of his visitors. Upon being asked which arm was +raised by a certain gentleman opposite him, Hans promptly answered by a +movement to the right, even though seen from his own side, it would +appear to be the left. Hans would also walk toward the persons or things +that he was asked to point out, and he would bring from a row of colored +cloths, the piece of the particular color demanded. Taking into account +his limited means of expression, his master had translated a large +number of concepts into numbers; e. g.:--the letters of the alphabet, +the tones of the scale, and the names of the playing cards were +indicated by taps. In the case of playing cards one tap meant "ace," two +taps "king," three "queen," etc. + +Let us turn now to some of his specific accomplishments. He had, +apparently, completely mastered the cardinal numbers from 1 to 100 and +the ordinals to 10, at least. Upon request he would count objects of all +sorts, the persons present, even to distinctions of sex. Then hats, +umbrellas, and eyeglasses. Even the mechanical activity of tapping +seemed to reveal a measure of intelligence. Small numbers were given +with a slow tapping of the right foot. With larger numbers he would +increase his speed, and would often tap very rapidly right from the +start, so that one might have gained the impression that knowing that he +had a large number to tap, he desired to hasten the monotonous activity. +After the final tap, he would return his right foot--which he used in +his counting--to its original position, or he would make the final count +with a very energetic tap of the left foot,--to underscore it, as it +were. "Zero" was expressed by a shake of the head. + +But Hans could not only count, he could also solve problems in +arithmetic. The four fundamental processes were entirely familiar to +him. Common fractions he changed to decimals, and _vice versa_; he could +solve problems in mensuration--and all with such ease that it was +difficult to follow him if one had become somewhat rusty in these +branches. The following problems are illustrations of the kind he +solved.[E] "How much is 2/5 plus 1/2?" Answer: 9/10. (In the case of all +fractions Hans would first tap the numerator, then the denominator; in +this case, therefore, first 9, then 10). Or again: "I have a number in +mind. I subtract 9, and have 3 as a remainder. What is the number I had +in mind?"--12. "What are the factors of 28?"--Thereupon Hans tapped +consecutively 2, 4, 7, 14, 28. "In the number 365287149 I place a +decimal point after the 8. How many are there now in the hundreds +place?"--5. "How many in the ten thousandths place?"--9. It will be +noticed, therefore, that he was able to operate with numbers far +exceeding 100, indeed he could manipulate those of six places. We were +told that this, however, was no longer arithmetical computation in the +true sense of the term; Hans merely knew after the analogy of 10 and 100 +that the thousands take the fourth place, the ten-thousands the fifth, +etc. If an error entered into Hans' answer, he could nearly always +correct it immediately upon being asked: "By how many units did you go +wrong?" + + [Footnote E: All examples mentioned are cited from extant works of + various observers.] + +Hans, furthermore, was able to read the German readily, whether written +or printed. Mr. von Osten, however, taught him only the small letters, +not the capitals. If a series of placards with written words were placed +before the horse, he could step up and point with his nose to any of the +words required of him. He could even spell some of the words. This was +done by the aid of a table devised by Mr. von Osten, in which every +letter of the alphabet, as well as a number of diphthongs had an +appropriate place which the horse could designate by means of a pair of +numbers. Thus in the fifth horizontal row "s" had first place; "sch" +second, "ss," third, etc.; so that the horse would indicate the letter +"s" by treading first 5, then 1, "sch," by 5 and 2, "ss" by 5 and 3. +Upon being asked "What is this woman holding in her hand?" Hans spelled +without hesitation: 3, 2; 4, 6; 3, 7; i. e., "Schirm" (parasol). At +another time a picture of a horse standing at a manger was shown him and +he was asked, "What does this represent?" He promptly spelled "Pferd" +(horse) and then "Krippe" (manger). + +He, moreover, gave evidence of an excellent memory. In passing we might +also mention that he knew the value of all the German coins. But most +astonishing of all was the following: Hans carried the entire yearly +calendar in his head; he could give you not only the date for each day +without having been previously taught anew, but he could give you the +date of any day you might mention. He could also answer such inquiries +as this: "If the eighth day of a month comes on Tuesday, what is the +date for the following Friday?" He could tell the time to the minute by +a watch and could answer off-hand the question, "Between what figures is +the small hand of a watch at 5 minutes after half-past seven?" or, "How +many minutes has the large hand to travel between seven minutes after a +quarter past the hour, and three quarters past?" Tasks that were given +him but once would be repeated correctly upon request. The sentence: +"Brücke und Weg sind vom Feinde besetzt" (The bridge and the road are +held by the enemy), was given to Hans one day and upon the following day +he tapped consecutively the 58 numbers which were necessary for a +correct response. He recognized persons after having seen them but +once--yes, even their photographs taken in previous years and bearing +but slight resemblance. + +A corresponding high degree of sensory activity seemed to accompany +these astonishing feats of memory and reason. Although the horse is not +usually credited with a very keen sense of vision, Hans was able to +count the windows of distant houses and the street urchins climbing +about on neighboring roofs. He had an ear for the most subtle nuances of +the voice. He caught every word,--no matter how softly it was spoken--so +that we were not allowed to whisper the answer to a problem, even when +standing at a distance of several yards, since it would be +equivalent--so Mr. von Osten declared--to giving the result to the +horse. + +Musical ability also comes into the category of Hans' accomplishments. +He possessed, not only an absolute tone consciousness--a gift granted to +few of us in the human world--which enabled him to recognize a note +sounded or sung to him as c, d, etc. (within the once accented scale of +c-major), but also an infallible feeling for intervals, and could +therefore determine whether two tones, sounded simultaneously, composed +a third or fifth, etc. Without difficulty he analyzed compound clangs +into their components; he indicated their agreeableness or +disagreeableness and could inform us which tones must be eliminated to +make consonance out of dissonance. C, d and e were given simultaneously +and Hans was asked: "Does that sound pleasant?" He shook his head. "What +tone must be omitted to make it pleasant?" Hans trod twice--indicating +tone "d." When the seventh chord, d-f-a-c, was sounded, he shook his +head disapprovingly. He evidently was old-fashioned in his musical +tastes and not agreeably disposed toward modern music, so he indicated +by tapping that the seventh, c, would have to be eliminated; thus +changing the seventh chord to a minor chord in order to obtain harmony. +When asked what tones might not be given simultaneously with the fourth +and sixth, Hans indicated consecutively the third, fifth and seventh; +that the first might be added, he was ready to admit. Finally, he was +familiar with not less than thirteen melodies and their time. + +Not only in the high degree of development of the senses and the +intellect, but also in that of the feeling and the will, did Hans +possess a decided individuality. Being of a high-strung and nervous +temperament and governed by moods, he evinced strong likes and dislikes, +and frequently displayed an annoying stubbornness,--a fact often dwelt +upon by Mr. von Osten. He had never felt the whip, and therefore often +persisted in wilfully answering the simplest questions incorrectly and a +moment later would solve, with the greatest ease, some of the most +difficult problems. Whenever any one asked a question without himself +knowing the answer, Hans would indulge in all sorts of sport at the +questioner's expense. We were told that the sensitive animal could +easily perceive the questioner's ignorance and would therefore lose +confidence in, and respect for, him. It was felt to be desirable, +however, to have just such cases with correct responses. Often, too, +Hans would persist in giving what seemed an incorrect reply, but which +was later discovered to be correct. On the other hand it was useless to +try to get answers upon topics of which he knew nothing. Thus he ignored +questions put in French or Latin and became fidgety, thereby showing the +genuineness of his achievements; but upon topics with which he was +familiar he could not be led astray. Indeed, there was nothing but +language lacking to make him almost human and the intelligent animal was +declared by experienced educators to be at about the stage of +development of a child of 13 or 14 years. + +This wonderful horse, which in the opinion of its friends was the means +of deciding in the affirmative the old, old, question of the +rationality of the lower forms and thus changing radically the existing +Weltanschauung, aroused world-wide interest. A flood of articles +appeared in the newspapers and magazines, two monograph[1, 2] attempts at +explanation were devoted to him.[F] He was made the subject of popular +couplets, and his name was sung on the vaudeville stage. He appeared +upon picture post-cards and upon liquor labels, and his popularity was +shown by his reincarnation in the form of children's playthings. Many +personages of note who had seen the horse's exhibitions, declared, some +of them in public statements, that they were now convinced. Among these, +besides Mr. Schillings, were naturalists of note; e. g.: the African +explorer Prof. G. Schweinfurth, Dr. Heinroth and Dr. Schäff, the +director of the zoological garden in Hanover; there were likewise +horse-fanciers of first-rank, such as General Zobel, and the well-known +hippological writer Major R. Schoenbeck. Again, the well-known +zoölogist, K. Möbius, writing in the "National-zeitung" declared he was +convinced of the horse's power to count and to solve arithmetical +problems. He also said that he believed the horse's memory and acute +power of sense-discrimination to be at the root of the matter. Those who +gleaned all their knowledge of the horse from newspaper reading were +satisfied to arrest judgment, or, on the other hand, became indignant at +the supposed imposition on the part of the gentleman of leisure and at +the gullibility of the public. Some would of course attempt explanations +on the basis of older facts. Here we have two points of view. + + [Footnote F: The works referred to in the text are to be found listed + on pages 267 ff.] + +Some tried to explain the whole thing on the basis of purely mechanical +memory and would thus allow the title "learned" but not "intelligent" +Hans. If, for instance, he was able to indicate the component of a clang +of three tones, it was not because he had the power to analyze the +tone-complex, but because he was able to see the stops of the harmonica +and was accustomed to give one tap for every stop which was closed. If +he was able to tell time by the watch, it was not because he read it, +but because he was always asked at the same hour of the day (which, of +course, was contrary to fact) and because he had learned by heart the +necessary number of taps. They also said that his manifold arithmetical +achievements were merely the expression of a remarkable memory; that in +the animal brain, lying fallow for centuries, there was stored up a +tremendous amount of energy, which here had been suddenly released. They +justified their point by calling to mind, in this connection, the +wonderful memory of primitive races. The authors of the two monographs +already mentioned, Zell and Freund, adopted this 'mnemotechnic' +interpretation, and the latter considered that he had disposed +definitely of the problem in designating the horse--a "four-legged +computing machine." + +Another group would not even allow Hans the glory of a wonderful memory. +He knew nothing. Rather was he to be regarded as a stupid Hans, and +totally dependent upon signs or helps given by his master. Only a very +few believed, however, that such signs--the nature of which was quite +unknown or regarding which only vague unsubstantiated suppositions were +advanced--were given unintentionally. Most of the critics openly averred +that we here had to do with intentional control, in other words, with +tricks. But not only did stupid orthodoxy dispose of the matter in this +way, but also the enlightened, who believe everything unusual to be +contrary to reason. They put the Hans problem on a level with +spiritualism, and were convinced that if the veil were removed a crass +imposition would be revealed. Professional trainers who regarded +themselves as well informed did not hesitate to give expression to this +same view, even though they had observed Hans inadequately or not at +all. + +The defenders of this second point of view were not at a loss to point +out the signs supposed to be given to Hans. One of these believed he had +discovered the primary means for giving these signs in the slouch hat of +Mr. von Osten. It was no accident, they said, that Mr. Schillings wore a +slouch hat when he experimented with the horse. It is sufficient to note +that Mr. Schillings was usually bare-headed or wore only a cap when he +tested the horse. Another accused, in like fashion, the long coat of the +experimenter; a third, who "had had opportunity to observe Hans on +several occasions," declared with equal certainty that the cue lay in +the movements of the hand as it was thrust into the pocket filled with +carrots. One circus-star declared, that the trick lay in eye movements, +another such star declared it lay in the movements of the hand. A sixth +discovered that the signs were "manifold" and adds, "to be sure, the +trainer must have a fund of such signs in order to prevent +embarrassment." Such a hypothesis is itself, it would seem, one of +embarrassment. On the other hand, there were many first-class observers +who vainly tried to discover regularly recurring signs; among them the +only professional trainer,--who had devoted any satisfactory length of +time to the horse and had also sought diligently for the signs in +question--said, "I was fully convinced that I would be able to explain +the problem in this way, but I was mistaken." The president of the +"Internationale Artisten Genossenschaft," a person who knew all the +usual means of control in trick performances, went over to the other +side as a result of his observations. + +There were others who sought for auditory signs. The opinion was +expressed that "Hans was unable to answer the simplest question such as +'What is two plus three?' whenever the questioner's tone of voice +differed from that of the master's." Another put chief stress upon the +changing inflection; furthermore, a "high degree of auditory +sensitivity" was often offered in explanation. + +The sense of smell was also made to bear some burdens. With its help, +for instance, Hans was believed to be able to recognize the photograph +of some one present, supposing, of course, that the person had carried +the picture about with him, thus allowing it to be impregnated with his +peculiar personal odor. One even suggested that the heat radiating from +the questioner's body and the electric stimulus conducted underground to +Hans's foot were sufficient explanation for his remarkable feats. + +Even the so-called N-rays, of one-day fame, which were supposed to +radiate from the human brain when in activity, were offered as a +solution. A similar thing may have been in the mind of the "natural +philosopher" who even after the publication of the December report, +wrote as follows in one of the journals: "On the basis of most careful +control, I have come to the conclusion, that the brain of the horse +receives the thought-waves which radiate from the brain of his master; +for mental work is, according to the judgment of science, physical +work." Of the same character are the explanations of two others, one of +whom declares that Hans was acting "under the magnetic influence of +man", while the other declared that "hypnotic suggestion is involved", +and, ignoring attested facts, tells us that, "The horse can execute the +commands of another only when the master, with whom it is 'en rapport', +wills that it shall obey." We may close the catalogue of explanations +with one more, which, in spite of its vagueness, found many defenders, +viz: suggestion. Without defining this conception more specifically and +without the slightest notion of the peculiar difficulties which it +involves (L. Loewenfeld in his "Handbuch des Hypnotismus" [Wiesbaden, +1901, pp. 35ff.] cites twenty different definitions of the term given by +as many authors) a critic writes: "The astounding phenomenon of an +animal apparently possessing human reason is to be attributed solely to +suggestion". Having referred to a dog trained for the vaudeville-stage, +the gentleman concludes that, "our intelligent horse, as well as the +dog, is simply of fine nervous organization and hence highly susceptible +to suggestions". + +What was to be done, with this mass of conflicting explanations? +Everyone considered his own opinion the only correct one, without, +however, being able to convince anyone else. The need here was not +simple affirmation, but proof. + + + + +CHAPTER II + +EXPERIMENTS AND OBSERVATIONS + + +A. EXPERIMENTAL CONDITIONS + +The observations on the horse under ordinary conditions would have been +quite insufficient for arriving at a decision as to the tenability of +the several possible explanations. For this purpose experimentation with +controlled conditions was necessary. + +It was necessary, first, that the place in which the experiments were +performed should be guarded against sources of error and interruptions. +Several difficulties stood in the way of the removal of the horse to a +more convenient place. Therefore, a large canvas tent was erected within +the courtyard of Mr. von Osten. This afforded the necessary isolation +without hindering the free movements of the horse. After the essential +part of the experiment had been completed and the problem had been +practically solved, experimentation was sometimes conducted in the open +courtyard. A number of the experiments were also performed in the +horse's stall. + +The choice of proper persons to experiment with the horse required +careful consideration. In so far as observations were to be made upon +the questioner, Mr. von Osten was of course indispensable. But to +obviate every objection he, as well as Mr. Schillings, had to be +excluded from the greater part of the experiments, and other persons +had to be selected who could learn to handle the horse. Now one would +have thought that the horse would respond to any moderately efficient +examiner. But as a matter of fact it was found that the horse would not +react at all in the case of the greater number of persons. Again, in the +case of others he would respond once or twice, but would then cease. All +told, Hans responded more or less readily to forty persons, but it was +only when he worked with Mr. von Osten or with Mr. Schillings, that his +responses were at all dependable. For this reason I undertook to +befriend the horse, and by happy chance it came to pass in a short time +he responded as readily to my questions as to those of the two +gentlemen. In a few of these experiments the Count zu Castell, Count R. +von Matuschka and Mr. Schillings undertook the rôle of questioner. Where +these are not mentioned in the results here published, I myself did the +questioning. + +With regard to the number of experiments and their performance, the +following precautions were observed. A sufficiently large number of +tests was made in each series in order to obviate the possibility of the +contention that the horse's errors were due to chance. The conditions of +experimentation were such that the further contention that he happened +to be tired or otherwise indisposed, whenever the reactions seemed to be +inadequate, could not be offered. The possibility of confusing the horse +by means of unwonted conditions also had to be avoided. For this reason +it was necessary to alternate the trial in which procedure was with the +knowledge of the answer on the part of the questioner, with the trial in +which the procedure was without such knowledge. Such precautions had +hitherto been neglected, and therefore those negative results which had +been occasionally obtained in single trials, could not claim objective +validity, even though the persons making the tests were subjectively +convinced. + +The course of the experiments was determined by the nature of the +problem itself. By means of a very simple test it was possible to +discover whether or not Hans was able to think independently. He was +confronted with problems in which the procedure was without knowledge of +the answer on the part of the questioner. If under these conditions he +could respond with the correct answer--which could be the result of a +rational process only--then the conclusion that he could think +independently, was warranted. The examination would be closed and Mr. +von Osten would be justified in all he claimed for the horse. If, +however, Hans should fail in this test, then the conclusion that he +could think was by no means warranted, but rather the inference that he +was dependent upon certain stimuli received from the questioner or the +environment. Further investigation would be for the purpose of +discovering the nature of these stimuli. + +To ascertain by means of which sense organ or organs the horse might +receive these necessary stimuli, the method of elimination was employed. +We began by excluding visual stimuli by means of a pair of very large +blinders. Should this investigation be without results, then we would +proceed to test the sense of hearing. The elimination of auditory +stimulations would be more difficult, because ear-caps or the closing of +the passage by means of cotton would not give sufficient assurance that +the sound-waves were being interrupted, even if the horse were docile +enough to suffer these appliances. Thereupon would follow the testing of +the sense of smell and of the skin-senses. And finally there might be +involved another still unknown sense, such as seems to exist in the +lower animal-forms. The reader therefore can readily see that the +investigation might possibly have become very complex, and that the +investigator had to be prepared for all of these possibilities. + +The results of the experiments and the essential circumstances under +which they were conducted, were in every case recorded immediately. + +It goes without saying that in the final formulation of the results, all +values--including those which were not consonant with the majority--were +to be used. + + +B. EXPERIMENTAL RESULTS + +During the course of these experiments Hans wore his accustomed +trappings, i. e., a girdle, light headgear and snaffle, and he either +stood alone, untied, or was held loosely by the bridle either by the +questioner or (though only in a few instances) by his attendant. The +questioner always stood to the right of the horse, as Mr. von Osten had +been accustomed to do. As reward for correct responses Hans received +from the questioner[G]--and from him only--a bit of bread or carrot, and +at times also a square of sugar. Never was a whip applied. From time to +time the horse was led about the courtyard or was allowed to run loose +in order to secure the needful respite. Besides myself there was usually +present Prof. Stumpf and Dr. von Hornbostel, who kept the records, and +frequently also Mr. von Osten. Several times I worked alone with the +horse. The results obtained in the horse's stall were in no respect +different from those got in the course of the experiments carried on in +the courtyard. Whenever a doubt arose as to the number of taps made by +the horse (though this did not frequently occur), then the series in +question was immediately repeated. + + [Footnote G: The expressions _questioner_ and _experimenter_ are used + interchangeably in this treatise.] + +In this report of the results of our experiments, the reader must bear +in mind that it was impossible to adhere to that order and distribution +of tests which we are wont to require in the case of psychophysical +experiments conducted under regular laboratory conditions. All sorts of +difficulties had to be overcome: unfavorable weather, the crowds of +curious ones, certain peculiarities of the horse--such as shying +whenever the wind rippled the canvas of the tent--and last but not +least, the idiosyncrasies of Mr. von Osten who repeatedly attempted to +interrupt the progress of the experiments. + +Since it was evident that different kinds of processes were involved in +solving the problems and since the solutions would be indicated by +tapping, or by movements of the head, or by walking over to the object +to be designated, the results of these three sets of experiments have +been grouped under three corresponding heads. + + +_I. Problems solved by tapping_ + +The following tests were made in which the method was such that when the +problem was presented to the horse, the correct solution was known to +none of those present, least of all to the questioner. This method we +shall designate in the following report as "procedure without knowledge" +whereas we shall call the method in which the answer was known to the +questioner, "procedure with knowledge". + +In order to discover if the horse could read numbers, a series of cards +on which numerals were blazoned, were exposed to the horse's view in +such a way that none of those present was able to see them, and the +horse was asked to tap the numbers as they were shown. This experiment +was repeated at different times and in all there were 49 tests in which +procedure was without knowledge, and 42 in which procedure was with +knowledge. In the case of the former there were 8% correct responses, +whereas in the case of the latter 98% of the answers were right. As an +example of the course which the series tended to take, we insert the +following, in which Mr. von Osten himself acted as questioner. + + Method. No. exposed. No. tapped. + + Without knowledge 8 14 + With " 8 8 + Without " 4 8 + With " 4 4 + Without " 7 9 + With " 7 7 + Without " 10 17 + With " 10 10 + Without " 3 9 + With " 3 3 etc. + +Whenever the questioner knew the solution, nearly all of the horse's +answers were correct; but when the answers were unknown to the +questioner, the horse's responses were, with only a few exceptions, +quite unsuccessful. Since the few exceptional cases must be regarded as +fortuitous, the conclusion is warranted that the horse was unable to +read numerals without assistance. + +In order to discover whether the horse could read words such as "Hans" +or "Stall" or the names of colors, they were written upon placards and +hung up in a row before the horse in such a way that the questioner +could see the individual word but could not immediately recognize the +particular place that each one occupied in the series. The horse was +then asked: "Upon which placard is the word 'Hans'?", "On which is the +word 'Stall'?", etc. In order to make sure, he was required to repeat +each answer. + +Then the experimenter would determine for himself the place of the word +in the series and would ask the question again. Fourteen such tests, in +which the procedure was with knowledge on the part of the questioner, +were interspersed with twelve in which the procedure was without such +knowledge. With the latter there were no correct responses, whereas in +the cases of procedure with knowledge 100% of the answers were correct. +Evidently the horse could not read words. + +Three words were thereupon whispered in his ear, which he was asked to +spell in accordance with the method described on page 21. Since he had +to indicate first the row, and then the place in the row occupied by the +letter, it took two answers to indicate the position of each letter. I +acted as questioner. The ordering of the table of letters was unknown to +me, except the position of the letter "a", which naturally came first, +and the place of the letter "s", concerning whose position I had +purposely inquired. The words chosen for this experiment were "Arm", +"Rom" (Rome) and "Hans". The horse responded incorrectly in the case of +every letter which was unknown to the questioner. "A" and "s" alone were +given correctly. Thus in spelling the word "Rom" the horse responded +with the series 3, 4; 3, 4; 5, 4; 5, 4; i. e. "jjst", instead of the +correct series: 4, 6; 4, 2; 3, 7. I later selected three other words, +the spelling of which involved the tapping of thirty-two numbers on the +part of Hans, and whose position I had carefully ascertained beforehand. +When these were given to the horse to spell, he responded promptly +without a single error. Evidently Hans was unable to spell without +assistance of some sort from the questioner. + +The horse's reputed aptitude in computation was tested in the following +way. Mr. von Osten whispered a number in the horse's ear so that none of +the persons present could hear. Thereupon I did likewise. Hans was asked +to add the two. Since each of the experimenters knew only his own +number, the sum, if known to anyone, could be known to Hans alone. Every +such test was immediately repeated with the result known to the +experimenters. In 31 tests in which the method was procedure without +knowledge, 3 of the horse's answers were correct, whereas in the 31 +tests in which the method was procedure with knowledge, 29 of his +responses were correct. Since the three correct answers in the cases in +which procedure was without knowledge evidently were accidental, the +results of this series of experiments show that Hans was unable to solve +arithmetical problems. + +For the purpose of discovering whether the horse could at least count, +the Russian kindergarten device, which Mr. von Osten had used in +training, was utilized. The machine was placed before the horse, but the +experimenter turned his back upon it. Before each test, a number of +balls were pushed to one side and Hans's problem was to indicate the +number thus separated. Each test was repeated with procedure with +knowledge. Of eight such experiments Hans responded successfully every +time procedure was with knowledge but failed every time procedure was +without knowledge. Thus 7 balls were at one time designated as 9 and +later as 14, while 6 were at first designated as 12, and later as 10. +Since all these errors could not be accounted for on the ground of +miscounts on the part of the horse, it was evident that Hans is quite +unable to count. + +The memory-test was conducted in the following manner. In the absence of +the questioner a number or the name of some day of the week was spoken +to the horse. The experimenter would then return and question him. Of 10 +responses 2 were correct, 8 incorrect. Among the correct answers were +the number 3, a number which, as we shall see, Hans was prone to give +under all sorts of conditions, and which therefore meant very little +when given as a correct response. The number 2, on the other hand, was +consecutively indicated by 7, 9, 5, and 3, 8 was given as 5, 6, 4, and +6, consecutively; and finally Wednesday was indicated as the fourteenth +day of the week. After this we undertook the test the horse's far-famed +knowledge of the calendar. Dates, such as Feb. 29, Nov. 12, etc., were +given to Hans and he was asked to indicate on which day of the week they +fell. Sunday was to be indicated by 1, Monday by 2, etc. Of 14 such +tests, 10 were unsuccessful, 4 successful. But in the case of these 4 +something very interesting occurred. It happened that during this series +the keeper of the horse was present, and he happened to know the days on +which these dates fell,--as he himself testified. The dates in question +were also little more than a week or so from the day of the experiment, +so they could easily be determined. But as soon as we took more remote +dates both man and beast were hopelessly lost. It was certain that Hans +had no knowledge of the calendar. It is needless to say anything of his +supposed knowledge of cards and coins. Hans plainly was incapable of +the astonishing feats of memory which had been claimed for him. + +Finally we investigated Hans' musical ability. In a room adjoining the +horse's stall there was a small harmonica, which spanned the once +accented octave. On this one or more tones were played. The horse was +required to indicate the tone played, the number of tones played and +their relation to one another. For testing his general hearing 20 tests +were given in which the method was procedure without knowledge. Of the +responses only one was correct, and that one was the tone e, for which +the proper response was three taps, but we must bear in mind what has +already been said of the number 3. The tone b was indicated by 11 taps, +although Hans had only learned a scale of one octave and therefore could +respond to only seven tones. In the tests in which the method was +procedure with knowledge, he again, without exception, was successful. +Similar results were obtained in the analysis of compound clangs. In the +cases of procedure without knowledge (although the experimenter here +knew the correct responses, he purposely refrained from thinking of +them) not a single response was correct; while in the cases of procedure +with knowledge, all but one were correct. The following were typical +responses: Three tones were played and the question was asked, "How many +tones were played?" Hans responded first with 4 taps and then with 1. +The tones c, e, g, a, (1, 3, 5, 6) were struck and the question asked, +"Which tone must be eliminated to make the complex a chord?" In the +tests in which the method had been procedure with knowledge, this +question had always been answered correctly, but when procedure was +without knowledge the responses were first 13, a tone which does not +exist for Hans, then 2, a tone which was not given in the clang to be +analyzed, and finally 3, which was not the discordant tone. Hans's +far-famed musical ability was an illusion. + +Taking the results of all the tests into consideration, we find that in +the case of procedure with knowledge, 90 to 100% of the responses of the +various series were correct, whereas, in those series of procedure +without knowledge 10%, at most, of the responses were correct. Under the +conditions prevailing during these latter tests, even these 10% must be +regarded as due to chance. To be sure Mr. Grabow, a member of the school +board and an enthusiastic follower of Mr. von Osten (Zeitschrift für +Pädagogische Psychologie, Pathologie und Hygiene, Berlin, 1904, Jahrg. +6, Heft. 6, S. 470), mentions a large number of successful tests, which +were supposedly made in accordance with the method of procedure without +knowledge. A thorough analysis of his experiments was not possible, +because the conditions under which they were conducted were not +adequately specified. But I have no doubt that the successful responses +of the horse were due solely to the absence of precautionary measures. +I, too, could cite a number of seemingly correct responses which +demonstrably were due to the absence of adequate precautionary measures. +I therefore repeat: Hans can neither read, count nor make calculations. +He knows nothing of coins or cards, calendars or clocks, nor can he +respond, by tapping or otherwise, to a number spoken to him but a moment +before. Finally, he has not a trace of musical ability. + +After all this experimentation it was evident that the horse was unable +to work alone, but was dependent upon certain stimuli from its +environment. The question therefore arose: does the horse get these +stimuli while the question is being put, or during his responses, i. e., +during the process of tapping. + +If Mr. von Osten's opinion was correct, then the process of questioning +played an important part in the success of the experiment. Of course, as +he said, it was not necessary to ask the question aloud; it was +sufficient--curiously enough--that it be inwardly spoken, thanks to the +horse's extraordinary auditory sensitivity. If, however, conditions were +made such that the auditory sense was eliminated, then the animal would +be unable to respond. Such a theory is not quite as absurd as it might +seem at first blush. For Hansen and Lehmann have shown that an acute +auditory organ is able to respond to such delicate stimulation as is +involved in the softest whisper, or even in the so-called nasal whisper +in which the lips are tightly closed.[3] They have attempted thus to +explain any modes of supposed "thought-transference", (cf. page 7). +Since experts on horses agree that the horse has acute auditory +sensitivity, Mr. von Osten seized upon this fact and tried to establish +his theory in the following manner. No response was successfully made on +the part of the horse, he said, when the sound waves caused by his (Mr. +von Osten's) inner speech were deflected from the ear of the horse. This +was the case when he closed nose and mouth while inwardly putting the +question, or deflected the waves from the horse's ear by means of a +placard held before his mouth while speaking, or finally by applying +lined ear-muffs to the horse's ears. If, on the other hand, he closed +only his nose and not his mouth while thus inwardly putting the +question, or if he held the placard so that there was a possibility of +deflecting the sounds to the horse's ear, or if the ear-muffs were of +too sheer a material, then Hans could hear and answer the questions +which for human ears were inaudible. He demonstrated all this by means +of experiments and of 20 tests of the first kind, in which auditory +sensations were supposedly eliminated, 95% of the responses were +incorrect (Hans would always tap too great a number); whereas of 28 +tests of the second kind, not a single answer was wrong, just as had +been predicted. Now I have repeated both kinds of tests, but have always +found some correct responses in those cases in which the horse, +supposedly, was unable to hear, a thing which greatly astonished Mr. von +Osten. In fact, the responses of the horse were quite as correct when I +did not even whisper the question inwardly. It was quite clear that +putting the question in any form whatever was wholly unnecessary. Mr. +von Osten's demonstrations to the contrary, which were based upon +erroneous physical principles, are to be explained as cases of vivid +autosuggestions, (but of this, more in Chapter V). After all this +experimentation, it was manifest that the cue was not given to the horse +while the question was being put; it occurred, therefore, at some time +during the process of tapping. But by means of which sense organ was it +received by the horse? + +We began by examining the sense of vision, and in the following manner. +Blinders were applied, and it is worthy of mention that Hans made no +attempt to resist. The questioner stood to the right of the horse, so +that the animal knew him to be present and could hear, but not see him. +Hans was requested to tap a certain number. Then the experimenter would +step forward into the horse's field of vision and would put the same +problem again. Since, in the tests of the first kind, Hans would always +make the most strenuous efforts to get a view of the questioner, and +since he would rave and tear at the lines whenever the attempt was made +to tie him,--a thing which he had never done hitherto,--it was +impossible to determine in some cases whether or not he had seen the +questioner during the process of tapping. I am using, therefore, in the +following exposition, besides the two categories of "not seen" and +"seen", a third which I have called "undecided". A total of 102 tests +were made in which large blinders were used. In 35 of these, the +experimenter certainly was "not seen" in 56 cases he was "seen" and the +remaining 11 are "undecided". Under the first of these categories 6% of +Hans's answers were correct (i. e. only two), under the second head 89% +were correct and under the third 18% were right. In other words, the +horse was at a loss the moment he was prevented from seeing the +questioner; whereas his responses were nearly always correct when the +experimenter was in sight, certain proof that the horse's failures are +to be attributed to the elimination of visual stimuli and not to the +general inconvenience occasioned by the blinders. It is evident +therefore, that the horse required certain visual stimuli or signs in +order to make a correct response.[H] + + [Footnote H: Throughout this treatise I am using the word "sign," or + "signal," whereas all other writers who have touched upon the + Hans-problem, have always spoken of "aids." Following von Sanden,[4] + however, I would distinguish clearly between the two. I would + designate as aids all immediate stimulations of the horse's body (i. + e. by means of contact), which have been designed with reference to + the animal's physiological movement-mechanism in such a way that + they truly 'aid' him in the production of the required movements. I + would regard as signs on the other hand, all stimulations (whether + mediate or immediate) which are selected without especial regard to + the anatomy or physiology of the horse, and bear no inseparable + relation to the thing to be done but are associated with it at the + will of the trainer. The rider's use of reins, and control by means + of leg-pressure and manner of sitting in the saddle, and the + driver's use of the lines,----all these, then are aids. A simple + pull at the reins, however, is not an aid, but a sign. The whip may + be used for giving signs as well as aids,----the latter, when it + does the work of the spur or of the pressure with the knees, as is + the case with ladies' riding-horses and in lunging. All calls and + all movements of the hand or head merely, on the part of the + trainer, are to be regarded as signs.] + +Such unequivocal results, however, were only obtained after we had +provided blinders of sufficient size (15 × 15 centimeters). Mr. von +Osten believing that the horse would not suffer these to be applied, had +at first proposed other measures. He held a slate before his face. Some +of the horse's responses were right, others wrong. The tests were +repeated and were successful as long as I, myself, held the slate before +my face, but not a single one of the responses was correct when another +would attempt to hold the slate before me. Mr. von Osten then brought +forth a kind of bolster which he fastened on the right side of the +horse's face,--the side which was turned toward the questioner. But this +also gave uncertain results. Finally he agreed to apply blinders. But +these were much too small and projected at a great angle from the head +(Mr. von Osten had cut the straps, for he thought they worried the +animal). The result was that only the posterior part of the horse's +normal field of vision was obstructed. Therefore, one could never be +quite sure whether Hans, who--it will be borne in mind--made every +attempt to see the questioner, had not perhaps after all been able to +peer over the edge of the blinder. The number of "undecided" tests, +therefore, became very great. Of 108 tests, only 25 could be placed in +the category of "not seen", 44 in the "seen", and 39, i. e., a third of +the total, in the "undecided." The percentage of correct answers for +these three categories were, respectively: 24%, 82% and 72%. Here we +have once more approximately the same ratio between the categories of +"seen" and "not seen" as in the case of the tests with the smaller +blinders. If we were to count the cases which we had put under the head +of "undecided," in the same category as those in which vision had been +excluded--as Mr. von Osten had done--then one would have been led to the +conclusion that the horse did not need visual signs. Several observers +had thus been led astray: e. g., General Zobel writes in the +"National-Zeitung" (Aug. 28, 1904), that upon request Mr. von Osten had +covered Hans's right eye "by means of some sort of blinder, so that he +was unable to see his instructor", and that Hans did not fail to respond +correctly. We evidently have here to do with the unreliable bolster +mentioned above. Furthermore, Mr. Schillings made a number of tests with +the small blinders, in which 50% of the answers were correct, and +probably in the same manner were obtained the results published in one +of the daily papers (the "Berliner Tageblatt", Dec. 12, 1904), several +days after the publication of the December report, and reading as +follows: "Tests have been made upon Hans with blinders over his eyes and +it is to be noted that, in spite of these, he still responds correctly." +Mention is also made of the experiments noted in Supplement III (page +257), in which Mr. von Osten hid behind the questioner and merely +encouraged the animal by occasional exhortations, but it is not possible +to say with any degree of certainty in how far he was really hidden from +the horse's view. + +I would add that the horse--in so far as it was at all possible to +decide--never looked at the persons or the objects which he was to +count, or at the words which he was to read, yet he nevertheless gave +the proper responses. But he would always make the most strenuous +efforts to see the questioner. (See page 43). I would furthermore add +that several experiments, in which Mr. von Osten and the horse were +separated from each other by means of the canvas tent, failed +completely, and that, on the other hand, all tests were successful in +which the questioner was present in the feed-room and the door between +this and the horse's stall was opened wide enough for him to be seen by +the horse. I would also mention that toward evening the responses became +less and less accurate. The conclusion that visual stimuli were here +operative cannot be gainsaid. + +It was possible, to be sure, that other senses might also be involved, +but it was certain that auditory sensations did not enter it. This is +shown by the fact that one might remain just as silent while the horse +was tapping his answer as during the putting of the question and yet +obtain a correct response. Hans, furthermore, could scarcely be +distracted by auditory stimulations. If either the experimenter or +anyone else present sought, at a given moment, to interrupt him by such +calls as "Halt", "Wrong", etc., while he was going through the process +of tapping, they very seldom succeeded in their attempt. Even though +such interruption did succeed in seven out of the twenty-one cases in +which it was tried, the assumption is well grounded that the success was +due entirely or almost entirely to minimal movements involuntarily +executed by those attempting the interruption. It is to such minimal +movements that the horse, as we shall see later, promptly reacted. When +the experimenter (Pfungst), himself, made the interjections, which +certainly should have been more effective, we found that the horse was +actually disturbed in only two of the fourteen cases; and finally in ten +consecutive cases of attempted interruption not a single one was +successful. There was almost a complete absence of any ear movements on +the part of the horse, a fact in which I have been borne out by Mr. +Henry Suermondt, the distinguished horseback rider. Indeed, I cannot +recall that Hans ever turned his ears toward me, a fact which is +strikingly curious in the case of a horse so attentive and so spirited +in temper. + +Finally, I might also mention that the breathing of the experimenter in +no wise influenced the outcome of the experiment. Whether he held his +breath or breathed on the leg or body of the horse, made no difference. + +Investigations of the other senses became needless, for I had, in the +meantime, succeeded in discovering the essential and effective signs in +the course of my observations of Mr. von Osten. These signs are minimal +movements of the head on the part of the experimenter. As soon as the +experimenter had given a problem to the horse, he, involuntarily, bent +his head and trunk slightly forward and the horse would then put the +right foot forward and begin to tap, without, however, returning it each +time to its original position. As soon as the desired number of taps was +given, the questioner would make a slight upward jerk of the head. +Thereupon the horse would immediately swing his foot in a wide circle, +bringing it back to its original position. (This movement, which in the +following exposition we shall designate as "the back step", was never +included in the count.) Now after Hans had ceased tapping, the +questioner would raise his head and trunk to their normal position. This +second, far coarser movement was not the signal for the back-step, but +always followed it. But whenever this second movement was omitted, Hans, +who had already brought back his foot to the original position and had +thereby put it out of commission, as it were, would give one more tap +with his left foot. + +If it was true that these movements of the questioner guided the horse +in his tapping, then the following must be shown: First, that the same +movements were observed in Mr. von Osten in every case of successful +response; secondly, that they recurred in the same order or with only +slight individual changes in the case of all who were able to obtain +successful responses from the horse, and that they were absent or +occurred at the wrong time in all cases of unsuccessful response. +Furthermore, it was observed that it was possible to bring about +unsuccessful reactions on the part of the horse as soon as the movements +were voluntarily suppressed, and conversely, that by voluntarily giving +the necessary signs the horse might be made to respond at pleasure; so +that anyone who possessed the knowledge of the proper signs could +thereby gain control over the process of response on the part of the +horse. These requirements have all been fulfilled, as we shall see in +the following pages. + +With regard to the regular recurrence of the movements noticed in the +case of Mr. von Osten, I was, after some practice, able to note +carefully their peculiar characteristics. This was rather difficult, not +only on account of their extreme minuteness, but also because that very +vivacious gentleman made sundry accompanying movements and was +constantly moving back and forth. To abstract from these the essential +and really effective movements was truly difficult. It was much easier +to observe these movements in the case of Mr. Schillings, probably on +account of the fewer accompanying movements and perhaps on account of +their greater distinctness. Usually he would raise the entire trunk a +trifle, so that the movements could be noticed from behind. Besides +these, I had an opportunity to observe the Count zu Castell, Mr. Hahn +and the Count Matuschka. All three made the same movements, though +somewhat more minutely than Mr. Schillings, yet none was as slight as +those of Mr. von Osten.[I] I further noticed that Count Matuschka and +Mr. Schillings often showed a tendency to accompany every tap of the +horse with a slight nod of the head, the last being accompanied by a +more pronounced nod and then followed by the upward jerk of the head, in +other words, they beat time with the horse. In the case of the last +three mentioned, for whom the horse responded far less effectively than +for Mr. von Osten or Mr. Schillings, belated or precipitate jerks would +frequently occur. This was found to be true in the case of all other +persons who had failed to elicit adequate responses from the horse. +Often, in both cases, a complete absence of any kind of minimal movement +had been noted. The accuracy of these observations in the case of Mr. +von Osten is attested by Mr. Stumpf and Mr. von Hornbostel, and by these +same gentlemen and Prof. F. Schumann in the case of Mr. Schillings and +myself. They also found these movements to be most minute in the case of +Mr. von Osten. In my case also they pronounced them "minimal, and often +quite imperceptible". All other persons who have seen me work with the +horse, but who were not familiar with the nature of these movements, +never perceived them, no matter how closely they observed me. + + [Footnote I: During the tests Mr. von Osten nearly always wore a + slouch hat with a wide rim. The rim, of course, always moved with + the head, and made the movements appear on a larger scale, (in the + ratio of about 3:2, as I was able to ascertain later by graphic + methods). But observation was successful, even at a distance of a + meter and a half, when he worked with head uncovered. And even if + head and forehead were covered entirely, it was still possible to + note the movements by watching the eye-brows. When Mr. Schillings + and the rest of us worked with the horse, we either went bare-headed + or wore only a very small cap.] + +Since the doubt was expressed that these movements did not precede but +followed closely upon the back-step of the horse (i. e., that an error +with regard to the time-element was involved), it became important that +time measurements be taken. This was done in the following manner: The +questioner asked the horse to tap numbers from 5 to 20, seldom higher. +He purposely refrained from pronouncing the number, but recorded it +after each test had been completed. This was a matter of indifference to +the horse (see page 42), and had the advantage that the measurement was +not influenced by knowledge on the part of the time-keeper. Two +observers were required, one watching the horse, the other the +questioner. Both observers had fifth-second stop-watches. The larger +face of this watch shows the fifth-second and a hand on the smaller face +indicates the minute. By pressing upon the stem the watch may be set in +motion at any moment desired, and by pressing it once more it may be +instantly stopped, and the time elapsing between the setting in motion +and the stopping may be read on the face. By pressing upon the stem a +third time the hands are brought back to zero, and the watch is ready +for another test. At a moment agreed upon beforehand--usually the third +tap of the horse--both observers started their watches. Practice tests +had shown that this could be done with all the accuracy necessary in +this case. As soon as the observer of the questioner noticed the +latter's head movement he stopped his watch, and as soon as the observer +of the horse noticed the latter's back-step he stopped his watch. Since +the movement of the horse's foot does not occur as a jerk, but is of +greater extent than a jerk would be, it was agreed that the observer was +to stop the watch as soon as he recognized the back-step as such, not +when the foot was being raised from the ground, because it was not then +evident whether the horse would bring it back to the original position +or whether he was preparing to give another tap, nor when he had brought +his foot completely back, but at the moment in which it was evident that +the horse intended to make the back-step. Experimentation had shown that +an agreement as to this moment was possible. A tap with the left foot, +which might possibly follow upon the back-step, could be left out of +account. The difference in time between the two watches would show the +time between the head-jerk of the questioner and the back-step of the +horse,[J] and if the back-step was indeed a reaction upon the +head-jerk, then the watches would have to show a later time for the +back-step than for the head-jerk. + + [Footnote J: For the benefit of those who are familiar with + reaction-time experiments of this kind, I would state the following: + The reaction to the head-jerk, on account of the minuteness of the + latter, was sensory throughout, and therefore all precipitate + reactions are entirely wanting. The reaction to the back-step was, + like the preceding one, a reaction to a visual cue. (Hans's tapping + was almost quite inaudible). Both stop-watches were carefully + regulated. In order to eliminate also the constant error which might + possibly arise as a result of some difference in the functioning of + their pressure-mechanism, the two watches were always exchanged in + the different series of tests, by the observer of the man and the + observer of the horse. The two time-measurements obtained by the two + observers contained, of course, the reaction-times of the observers + themselves. In order to equalize the constant error which thereby + arose, it was arranged that each observer should react alternately + now to the man, now to the horse. In order to be perfectly safe, the + reaction-times of those concerned, (von Hornbostel, Pfungst, + Schumann and Stumpf), were later determined in the laboratory by + means of the carefully regulated Hipp chronoscope. Separate + determinations were made of the reactions to the head-jerk and to an + imitation of the horse's back-step. Then the time which one observer + took to react upon a head-jerk, was compared with the reaction-times + of the other observers to the back-step. Since the greatest + difference which was found in this comparison, did not exceed + one-tenth second, the results obtained in the courtyard required no + correction.] + +Measurements of this kind were taken for Mr. von Osten, Mr. Schillings +and myself. In the case of the first two it was taken without any +knowledge on their part. They did not even know that they were being +observed, having been told that the measurements were for the sake of +determining the horse's rate. In my case, to be sure, the time could not +be taken without my knowledge. I succeeded, however, in eliminating the +effect of this knowledge on my part. (Cf. pages 88 and 145.) Since the +results obtained in the case of Mr. Schillings quite agree with those +obtained in my case, it is evident they may be considered as being of +equal value. + +With regard to the number of tests the following table may be referred +to. The first vertical column gives the name of the questioner, i. e. +the person operating with the horse. The four other columns give the +number of tests made upon each of these. The name of the person who made +the observation in each series is indicated at the head of the column. +It is unnecessary to give the name of the observer of the horse, for the +only difficulty lay in the observation of the questioner. The numerals I +and II indicate two series taken at different times. + + -----------------+----------+----------+----------+---------- + | v. H. | Pf. | Schu. | St. + -----------------+----------+----------+----------+---------- + Questioner. | I II | I II | I II | I II + -----------------+----------+----------+----------+---------- + v. Osten | 9 15 | 34 17 | - -- | 8 27 + -----------------+----------+----------+----------+---------- + Schillings | - -- | 19 17 | 6 16 | - -- + -----------------+----------+----------+----------+---------- + Pfungst | 6 13 | -- -- | - -- | 9 -- + -----------------+----------+----------+----------+---------- + +We have omitted from this table several tests in which the observer of +the questioner noticed no head jerks whatever, and therefore could not +arrest his stop-watch, although the horse responded correctly. Four +tests of this kind were made by Mr. von Hornbostel, two by Mr. Pfungst, +two by Mr. Schumann and five by Mr. Stumpf. In the case of Mr. Pfungst +the horse gave the unusually high number of fifty taps. The attention of +the observer had been taxed too long and had failed him (two seconds is +the most favorable time). The head-jerk of Mr. von Osten evidently +occurred during a lapse in Mr. Pfungst's attention and therefore +remained unnoticed. + + -----------------+----------+----------+----------+---------- + | v. H. | Pf. | Schu. | St. + -----------------+----------+----------+----------+---------- + Questioner. | I II | I II | I II | I II + -----------------+----------+----------+----------+---------- + R. | 44% 60% | 62% 88% | -- -- | 0% 48% + V. Osten. | | | | + W. | 56% 20% | 12% 0% | -- -- |100% 22% + -----------------+----------+----------+----------+---------- + R. |100% 92% | -- -- | -- -- |100% -- + Pfungst. | | | | + W. | 0% 0% | -- -- | -- -- | 0% -- + -----------------+----------+----------+----------+---------- + R. | -- -- | 74% 100% | 83% 100% | -- -- + Schillings. | | | | + W. | -- -- | 5% 0% | 17% 0% | -- -- + -----------------+----------+----------+----------+---------- + +The results of the experiments are given in the second table. The +general arrangement corresponds to that of the first table. Even though +the absolute number of tests was small, yet for the sake of giving a +better general view, all values are given in percentages. The tests in +which the movement of the questioner had preceded that of the horse--as +had been anticipated--are recorded under "R" (right); under "W" (wrong), +we have recorded those cases in which the testimony of the +stop-watches--contrary to our expectation--indicated that the reverse +order prevailed. Finally, those cases which would complete the 100%, i. +e. those in which the watches indicate simultaneity of the movements in +question, are not recorded. + +From this table we may note the following: The time-measurements for Mr. +Schillings and Mr. Pfungst are quite in agreement and go to show that +the order in time of the head movement of the questioner and the +back-step of the horse was exactly what had been expected. The few +contradictory cases which occur in Series I of the observations upon Mr. +Schillings are to be accounted for by the fact that he was here for the +first time the subject of observation, whereas the recorded +time-measurements in the case of Mr. Pfungst had been preceded by a +number of practice tests. The results of the measurements taken in the +case of Mr. von Osten were far less satisfactory. Even if one were to +allow a series containing barely more than 50% of "right" cases as +sufficient proof of the correctness of our expectation regarding the +order of the movements of the questioner and the horse, only three of +the six series obtained with Mr. von Osten as subject, would satisfy +this expectation. However, since four of the six series show a greater +number of cases of simultaneity (their percentage may be easily deduced +by referring to the per cent of "right" and "wrong" cases), the proposed +method would give a distorted view, and therefore it appears that the +more correct method would be to consider simply the numerical ratio of +the "right" and "wrong" cases. Since, furthermore, Series II shows, in +every case, a decided change which is similar for all observers (note +especially Pfungst), there can be no doubt but that practice is here +involved, and that Series II is to be regarded as the true standard. +Throughout this series we find a preponderance of "right" cases. +Therefore, the table unmistakably confirms the expected order in time. +That there were more "wrong" cases with Mr. von Osten as subject than +with the other questioners is to be explained by the fact that the +decisive movements were far less easily observed in this case, than in +that of the other questioners. (See page 49.) We expect that Series III +would show the same results, or approximately the same results in the +case of Mr. von Osten that it did for Mr. Pfungst and Mr. Schillings, +but unfortunately he declined to act as subject. In the meantime, +however, new and decisive proof presented itself which destroyed all +possible doubt. + +Before adverting to it, let us consider in a few words the reaction-time +of the horse,--the time elapsing between the final sign of the +questioner and the reaction of the horse (i. e., the back-step). +Unfortunately this time cannot be directly determined. All that can be +ascertained from our time-measurements, is the time intervening between +the moment of the head-jerk and the moment in which the reaction of the +horse is noted. (See page 51). This time averaged, for the 127 +measurements, .45 seconds. If we stated the unavoidable error, (obtained +on the basis of extended supplementary measurements which it is not +necessary to consider here) as .15 seconds, and apply it to the value +found above, we obtain .3 seconds as the probable reaction-time of the +horse.[K] + + [Footnote K: See page 126 on the corresponding reaction-time in the + case of man. Similar tests have been made in the case of animals in + only one instance, and that for dogs, by E. W. Weyer.[5] But, as + might have been expected, they did not yield any satisfactory + results.] + +That the tapping--as well as all other movements of the horse--was +nothing other than a reaction upon certain visual stimuli, was proved +beyond a doubt by the fact that the voluntary execution of the head-jerk +and of other movements--which we will describe in more detail later +on,--brought about all the proper responses on the part of the horse. +Thus, artificial synthesis became the test of the correctness of +analytical observation. + +To elucidate; if the questioner retained the erect position he elicited +no response from the horse, say what he would. If, however, he stooped +over slightly, Hans would immediately begin to tap, whether or not he +had been asked a question. It seems almost ridiculous that this should +never have been noticed before, but it is easily understood, for as soon +as the questioner gave the problem he bent forward--be it ever so +slightly--in order to observe the horse's foot the more closely, for the +foot was the horse's organ of speech. Hans would invariably begin to tap +when I stooped to jot down some note I wished to make. Even to lower the +head a little was sufficient to elicit a response, even though the body +itself might remain completely erect. Of thirty tests made in this +position, twenty-nine were successful. Hans would continue to tap until +the questioner again resumed a completely erect posture. If, for +instance, I stooped forward after having told the horse to tap 13, and +if I purposely remained in this position until I had counted 20, he +would, without any hesitation, tap 20. If I asked him to add 3 and 4, +but did not move until 14 was reached, he would tap 14. Twenty-six such +tests gave similar results. + +The reaction of the horse upon such a signal for stopping showed slight +modifications according to the time which elapsed between the last tap +and the signal for stopping. These modifications, which had hitherto +been paraded as expressions of the horse's psychical power may be +illustrated by the following schematic figures (Figures 1-4). In all of +them the dotted line _c-d_ represents the ground level; _d_ shows where +the horse's right forefoot was located before he began tapping; _a_ and +_c_, respectively, indicate the place to which the foot is lowered +during the process of tapping. The unbroken line gives the direction of +the back-step. + +If Hans, having raised his foot from _a_ to _b_--preparatory to +tapping,--receives the signal at or just before the moment he lowers the +foot, he immediately swings it in a wide circle from _c_ back to its +original position at _d_, (Fig. 1). As a matter of fact _a_ and _c_ +coincide, but are juxtaposed in the diagram for the sake of schematic +utility. This was the usual form of the back-step. + +[Illustration: FIG. 1.] + +If the signal for stopping is given a little after the last tap (Fig. +2), i. e., at the time that the foot is already being raised for another +tap, then the back-step occurs as _a-b-d_. The horse thus gives, at the +moment it receives the signal for stopping, a changed impulse to the +moving foot. The curve, therefore, has a kink at _b_, and the back-step +occurs with seeming hesitancy,--Hans appears not quite certain of his +result. + +[Illustration: FIG. 2.] + +If the signal be given somewhat later still (Fig. 3), i. e., when the +foot is being lowered to complete a tap, Hans is still able to put on +the brakes--as it were--and draw back his foot before it reaches the +ground. The whole process gives the impression that the horse was just +about to make a "mistake" of one unit, but at the last moment had +bethought himself of the correct answer. + +[Illustration: FIG. 3.] + +Finally, if the signal be deferred still longer, it becomes impossible +to prevent the extra tap. The back-step again has the same form as in +figure 1; Hans has made a "mistake" in his answer by one unit too many. + +Conversely, if the head-jerk of the questioner occurs too soon; i. e., +at the moment the horse has raised his foot for the final tap to the +height _b_, (Fig. 4), then the tap is not completed,--but the foot, +without touching the ground, makes the curve _b c_{2} d_, back to its +original position. Hans has again made a "mistake" in his answer,--this +time by one unit too few. + +[Illustration: FIG. 4.] + +All these variations go to show one thing: Hans never knows in advance +which tap is to be the final one. These variations in his reactions +occurred often without having been intended by the questioner. But to +bring them about at will required skill, on account of the shortness of +the time involved in the reaction. + +Whenever the signal for stopping--which we have just discussed--was +followed by the complete erection of the head and trunk, Hans would +definitely cease tapping. If, however, the questioner failed to assume a +completely erect position, or if he stooped forward ever so slightly, +the horse would follow the back-step of the right foot with an extra tap +of the left foot. Besides occurring in tests in which Mr. von Osten +assumed the rôle of questioner, this fact was also noted when the Count +zu Castell and Mr. Schillings acted as subjects. Since the extra tap +just mentioned was not given like the others with the right foot +forward, but with the left foot upon the spot, it was possible for the +horse to execute it with a greater show of energy. This simulated a high +degree of mental certainty on the part of the horse, as if he wished to +indicate that this was the correct solution of the problem and it would +have to stand. In spite of all this, many errors would creep in. It was +possible to prolong this extra tap and thus make it appear more +dilatory. We need hardly add that henceforth it was within the power of +the experimenter to have the tapping executed entirely with the right +foot or with the final extra tap of the left foot. Hitherto the view had +been current that this lay solely within the pleasure of the horse. + +If the questioner still inclined forward, still remained in the bent +posture after Hans had given the final tap with his left foot, the horse +would immediately begin to tap once more with his right foot, which had, +in the meantime, become ready for further action. If the head jerk was +then made, Hans would bring his right foot back, give the extra tap with +his left foot, then resume tapping with the right and thus continue +until the questioner once more resumed the erect posture. Thus the horse +on one occasion when I wished him to tap 100, gave--contrary to my +desire--the following response; 39 with the right foot, 1 with the left, +24 with the right, 1 with the left, 35 with the right, and 1 with the +left. Later it became possible for me to cause him to tap 1 right, 1 +left, 1 right, 1 left, etc. I could even get him to tap exclusively with +the left foot by standing at his left rather than at his right as had +been customary with his questioners. These taps with the left foot were +executed in a far less elegant fashion than those with the right foot, +and with a great waste of energy. Hans had become a right-handed +individual--as it were--as a result of long habit. + +With regard to the distance at which the experimenter directed the +horse, the following may be said: The usual distance was one-quarter to +one-half meter. This holds for all tests hitherto described. Seventy +tests which were made for the purpose of discovering the influence of +change in distance showed that the reaction of the horse upon the +customary signal of the head-jerk was accurate up to a distance of three +and one-half meters. At a distance of three and one-half to four meters +there suddenly occurred a fall of 60-70% in the number of correct +responses. At a distance of four to four and one-half meters only +one-third of the responses were correct, and at a distance beyond four +and one-half meters there were no correct responses. The greater number +of these tests were made in our presence by Mr. von Osten, who was under +the impression that we were testing the accuracy of the horse's hearing, +whereas we were really testing the accuracy of his perception of +movements. + +With regard to the different positions which the experimenter might +assume with reference to the horse, the following may be noted: The +normal position was to the right of the horse. If the experimenter stood +immediately in front of Hans, the latter's reaction would be just as +accurate, though he would always turn his head and make desperate +efforts to see the questioner, even though he was held in short by the +reins. When a position immediately behind the horse was taken--a +somewhat dangerous proceeding, since Hans would at once begin to +kick--no response could be obtained until he succeeded in turning far +enough around to get the questioner within view. If he was restrained +from turning completely around, he would at least turn his head,--and +always to the right. One might even turn his back upon Hans during the +tests, for the signal for stopping was not obtained from the face of the +questioner, but from a movement of the head. The following incident will +show to what extent the horse had become accustomed to seeing the +questioner in a certain definite position. For a long time I had been +in the habit--without exception--of standing close to the horse's +shoulder. Mr. von Osten, on the other hand, would stand farther back. +When, on a certain day, I assumed the latter position, the horse would +not suffer it, but would move backward until he had his accustomed view +of me. + +Finally we sought to discover by what movements the horse could be made +to cease tapping. We discovered that upward movements served as signals +for stopping. The raising of the head was the most effective, though the +raising of the eyebrows, or the dilation of the nostrils--as in a +sneer--seemed also to be efficacious. However, it was impossible for me +to discover whether or not these latter movements were accompanied by +some slight, involuntary upward movement of the head. The upward +movement of the head was ineffective only when it did not occur as a +jerk, but was executed in a circuitous form,--first upward and then back +again. Such a movement was occasionally observed in the case of Mr. von +Osten. The elevation of the arms or of the elbow nearest the horse, or +the elevation of the entire body was also effective. Even if a placard, +with which the experimenter tried to cover his face, were raised at a +given moment, the horse would make the back-step. On the other hand, +head movements to the right and to the left or forward and back, in +fine, all horizontal movements, remained ineffective. We also found that +all hand movements, including the "wonderfully effective thrust of the +hand into the pocket filled with carrots", brought no response. I might +also change my position and walk forward and then backward some distance +behind the horse, but the back-step would only occur in response to the +characteristic stimulus. After what has been said it is easy to +understand how vain were Mr. Schillings' attempts to disturb the horse +and how naturally he might conclude that Hans was not influenced by +visual signs. Mr. Schillings simply did not know which signs were +effective. + +While the horse could thus be interrupted in the process of tapping by +movements which were executed at the level of the questioner's head, yet +movements below this level had the opposite effect. If Hans showed that +he was about to cease tapping before it was desired, it was possible to +cause him to continue by simply bending forward a trifle more. The +greater angle at which the questioner's trunk was now inclined caused +the horse to increase the rate of tapping. The rule may be stated thus: +The greater the angle at which the body inclined forward, the greater +the horse's rate of tapping, and _vice versa_. It was noticeable that +whenever Mr. von Osten asked for a relatively large number--in which +case he always bent farther forward than in the case of smaller +numbers--Hans would immediately begin to tap very swiftly. Not being +entirely satisfied with these observations, the following more exact +measurements were taken. I asked the horse to tap 20. From 1 to 10 I +held my body at a certain constant angle, at 10 I suddenly bent farther +forward and retained this posture until 20 had been reached. If there +existed a relationship between the angle of inclination and the rate of +tapping, then the time for the last ten taps ought to be less than for +the first ten. Of 34 such tests 31 were sucessful. The following are two +specimen series. + +The first series consisted of ten tests of 15 taps each. In all cases my +head was bent at an angle of 30° to the axis of the trunk, but I +constantly changed the angle of inclination of the trunk. It was not +possible to measure this angle accurately on account of the rapidity +with which the whole test had to be made. I was able, however, to +differentiate between them with enough accuracy to designate the +smallest angle (about 20°) as belonging to Grade I, and the greatest +angle (about 100°) as belonging to Grade VII. By fixing certain points +in the environment, it was possible to get approximately the same angle +repeatedly. The time from the third to the thirteenth tap was, in all +cases, taken by Prof. Stumpf by means of a stop-watch. The tests were +taken in the following order: + + Grade of inclination: I VI II II IV V VI VII + Time for 10 taps: 5.2 4.6 5.0 5.0 4.8 4.8 4.6 4.4 sec. + +From this series it will be seen that in the case of the same angle of +inclination (II and VI were repeated and III was omitted) the same rate +obtained in the tapping. In two other tests I constantly increased the +angle of inclination during the 15 taps, and Hans gradually increased +the rate of tapping accordingly. + +In a second series I had the horse tap 14, five times. I myself took the +time of the taps up to 7 by means of the stop-watch, while Prof. Stumpf +took the time of the taps from 8 to 13. At 8 I suddenly bent forward a +little more and retained this position until tap 13. The results were as +follows: + + Taps 2 to 7 (Pf.): 3.2 2.2-2.4 2.4 2.2-2.4 2.4 seconds. + " 8 to 13 (St.): 2.6 2.0 2.0 2.2 2.2 seconds. + +Such good results, however, were possible only after a number of +preliminary practice tests had been made. The experiment was especially +difficult because the horse was often on the point of stopping in the +midst of a test. This was probably due to some unintentional movement +on my part. In such cases I could induce him to continue tapping only by +bending forward still more, but this effected also, as we have seen, an +increase in his rate of tapping. Such tests, of course, could not give +unambiguous results. + +The rate of tapping was quite independent of my rate of counting. Thus, +if I counted aloud rapidly, but bent forward only very slightly, the +horse's tapping was slow and lagged behind my count. If I counted slowly +but bent far forward, Hans would tap rapidly and advance beyond my +count. Thus we see that his rate of tapping was in accordance with the +degree of inclination of my body and never in accordance with the rate +of my counting, i. e., it was quite independent of every sort of +auditory stimulation. + +Direct observation and a comparison of the records of the time Hans +required in giving to his master responses involving small, medium and +large numbers, with the records of the time which he required to respond +to my questions when I bent only slightly, moderately or very far +forward, proved that the increased rapidity in tapping in the case of +large numbers, which many regarded as an evidence of high intelligence, +(see page 20), was, as a matter of fact, brought about in the way +described. The two series (in each of which the time measured was for 10 +taps) are quite in accord. The horse did not tap faster because he had +been given a large number by Mr. von Osten, but because the latter had +bent farther forward. + +From all this it readily appears why it was possible to cause Hans to +increase his rate of tapping but not to decrease it. To do the latter +would involve a decrease in the angle of inclination of the body. This +would necessitate the erection of the body. As we have seen, this was +the signal to which Hans reacted by ceasing to tap. And as a matter of +fact we never knew the horse to decrease his rate of tapping in the +course of any single test, except in the case of very large numbers, and +then it was probably due to fatigue. Mr. von Osten insisted that Hans +often slowed down toward the end of a test, "in order to obviate +mistakes", but all the tests in which he tried to demonstrate this to +us, were unsuccessful. In spite of all exhortation, Hans would tap +either uniformly or somewhat more rapidly as soon as his master--in all +probability unconsciously--bent somewhat lower. Only once was such a +test successful. Mr. von Osten--upon our request--asked the horse to +give a certain large number. In this instance the decrease in the rate +of tapping was due to fatigue and had nothing whatever to do with the +desire on the part of the horse to avoid error. Furthermore, Mr. Hahn, +who had visited Hans twenty times and had made careful notes of his +observations, corroborated my statement when he said that he himself +never noted the decrease in rate mentioned. Contrary statements may +perhaps be due to the fact that the tense state of expectancy on the +part of the observer made the interval between the last taps appear +subjectively somewhat longer. + +So much for the technique of the tapping. Now a word about the numbers +which Hans tapped. (I refer only to the results obtained in series which +involved no volitional control). The number 1 was very difficult to get. +Hans usually tapped 2 instead. Thus even in the case of Mr. von Osten he +responded five times with 2, and only in the sixth test did he react +correctly. As far as other questioners were concerned, 1 was seldom +ever obtained, except in the case of Mr. Schillings and myself. The +numbers 2, 3 and 4, on the other hand, were very easily obtained and, +above all, 3 seldom failed. 3 seemed to be the horse's favorite number +and was very frequently given instead of other numbers. Thus, one-sixth +of all the horse's incorrect responses which were given to me were in +terms of the number 3. The numbers 5 and 6 were a little more difficult +to obtain and above 10 the difficulty increased rapidly. Indeed, I never +saw Hans respond with a number exceeding 20 to any questioner, Mr. +Schillings and Mr. von Osten excepted. I saw the nine vain attempts of +Count zu Castell to get the number 15, and Count Matuschka's eight +unsuccessful attempts to obtain the number 16 as a response. But even +with Mr. von Osten and Mr. Schillings such failures were not infrequent. +Thus, Mr. von Osten tried five consecutive times to obtain the number +24. I myself did not fare any better at first. But the following table +shows what practice can do. If we compare the percentage of correct +responses (involving the numbers 1 to 7--for which alone I have +sufficient material, viz., 80 to 100 cases), obtained in the first half +of our tests, with that of the second half, we get the following: + + For number: 1 2 3 4 5 6 7 + In first half of tests: 49, 92, 89, 86, 74, 62, 53% + " second " " " : 92, 95, 92, 98, 97, 86, 96% + +From this we see how hard it was at first to get the number 1 and that +failure was as frequent as success, and how much easier it was on the +other hand to get the numbers 2 and 3 (and which, therefore, do not show +any great improvement in the second half of the tests). Beyond the 3 the +percentage of correct responses decreased and the number 7 stood at the +same level as the number 1. In the second half of the tests, all these +differences disappeared and errors were infrequent and seldom exceeded ++1 or -1. These results of practice are not to be accredited to the +horse, but to the experimenter, who was at first quite unskilled. This +difference in results does not appear in the case of Mr. von Osten, for +his initial practice had been had many years previous. The values +obtained in his case were very constant throughout our experimentation +and generally showed something like 90% of correct responses. To be +sure, in his case also, the number 1 was somewhat unfavorable, (79% were +correct responses). But the percentages obtained in his case showed no +improvement whatever throughout our experimentation. We need scarcely +add that with the voluntary control of the giving of the signs, in the +case at least of such small numbers as are here discussed, no errors, +whatever, occurred. + +We have discussed the influence of the experimenter, i. e., the one who +asked the horse to tap; now let us consider the influence of others +present upon the horse. + +As a general rule, other persons had no effect upon the horse's +responses. This appears from the failure of nearly all tests in which +all of those present--with the exception of the questioner himself--knew +the number which the horse was to tap. Even when the others concentrated +their whole attention upon the number, it profited little as a close +analysis of the 136 cases, which belong under this head in our records, +go to prove. Thus, in the presence of a group of twenty interested +persons--during the absence of Mr. von Osten--twenty-one problems were +given to the horse, the solutions of which were known to everyone but +myself, the questioner. Result: only two correct responses. Only when +there was among the spectators someone to whom the horse was accustomed +to respond or one from whom he regularly received his food, would such +an influence be effective.[L] But such cases were few. The most +important were the following: I at one time whispered a number to Hans +(on the occasion of the tests mentioned on page 37), and Mr. von Osten +asked for it the moment I stepped aside. Hans answered incorrectly even +though I stood close beside Mr. von Osten; I did not, however, think +intently of the number. As soon as I concentrated my attention upon the +number he promptly responded correctly. Further cases are those +mentioned on page 38, in which the keeper of the horse unintentionally +aided in giving four dates which were unknown to all others present, +including the questioner. This single instance shows the necessity of +the rule that during tests in which the method is that of procedure +without knowledge the solutions should be known to no one of those +present. Finally the tests made by the September-Commission and reported +in Supplement III (page 255) may possibly belong under this head. Since +they were not followed out any further, I am unable to render a definite +judgment upon them. In most of these tests the question itself, as put +by Mr. von Osten, was not adequately answered, but curiously enough, +however, the number which had been given to Hans in von Osten's absence +and which formed the initial number of some mathematical operation, was +tapped correctly. This may possibly be explained by the assumption that +this initial number had been retained in the memory of some of those +present, (see page 149, on the "perseverative tendency"), and that the +horse, since he had been working with some of them, responded to one of +those present. Chance may have played some part also. + + [Footnote L: Mr. Schillings, however, did succeed in making a number + of tests with the co-operation of others who had never before worked + with the horse. These tests were made under the following + conditions: The horse was standing in his stall, when Mr. Schillings + and another gentleman approached him. There was no one else present. + Mr. Schillings, who tried to remain as passive inwardly, as + possible, asked his partner to think consecutively of different + numbers between one and 20, which thus were known to him alone. Hans + was then commanded by Mr. Schillings to tap the numbers, which he + did, to the great astonishment of the men, and especially of Mr. + Schillings. In like manner Mr. Sander, a staff physician in the + marine, received--so he writes me--three correct responses to four + questions which he put to the horse. It happened also in the case of + two scientific men and finally, too, in my own case when I first + came in contact with the horse, (see page 88). The horse's reaction + was brought about in the same way in every one of these instances. + Mr. Schillings, in bending forward slightly, thereby started the + horse a-tapping, and his companion--just as innocently--interrupted + the process by means of a movement of his head, when the right + number of taps was reached. + + I later tried similar experiments together with Mr. Hahn. I was + aware of the answer to the riddle at the time, but he was not. Mr. + Hahn stepped in front of the horse and thought intently of certain + numbers. I did the questioning, that is, I got the horse to tap. In + twelve tests Hans responded correctly in only two instances. In the + ten others he always tapped beyond the number Mr. Hahn had in mind, + e.g., 21 instead of 2, and was evidently awaiting a movement on my + part. When we exchanged rôles, Mr. Hahn doing the questioning and I + doing the "thinking," the horse would not respond at all, although + as a rule Mr. Hahn had been fairly successful in working with him + alone. I had gradually gained so much influence over the horse, that + he would scarcely attend to any one else when I was about--Mr. von + Osten hardly excepted. + + In this connection I would prefer to avoid the term "rapport," which + may rise in the minds of many, since it has been used so much in + connection with the phenomena of hypnotism, for I would not obscure + a fact that is clear by giving it a name that is vague.] + +If the questioner knew the number of taps desired, (which was not the +case with the tests hitherto discussed), then the environment had still +less influence upon the horse--except that it caused occasional +interruption. The horse's responses, therefore, did not tend to become +more successful just because a number of persons were simultaneously +concentrating upon the result desired. This was proven by the +experiments which we repeatedly made for this purpose. Only one person +at a time had any influence upon Hans. If two questioners tried to +influence the horse at the same time,--other conditions being the +same,--success would be for the one who had the greater control over the +animal when working alone with him. Prof. Stumpf and I made the +following experiment. Both of us stood to the right of the horse, each +thinking of a number. In ten such tests Hans always tapped my number. +When Stumpf concentrated upon 5 and I upon 8, the horse responded with +8, i. e., the larger number. When Stumpf had 7 in mind, and I had 4, the +response would be 4, i. e., the smaller number. When Stumpf thought of +number 6, and I had fixed upon none, Hans tapped 35. He was evidently +awaiting my signal. When I went away Stumpf again demanded the number 6, +and the horse responded properly. When I returned, Stumpf's attempts +again failed. On another occasion Count Matuschka put a number of +questions, while Mr. von Osten stood behind him. All of the horse's +responses were correct, even the one answering the question: "How much +is 7 times 7?", which was difficult on account of the great number of +taps required. I was able to note from the direction of the horse's eyes +that he was attending only to his master and not to the Count. On still +another occasion Mr. Grabow sang two tones--the second being the fourth +of the first--and asked Hans: "How many intervals lie between?" I was +standing erect before the horse, and was thinking intently of the +number 2, but without giving any voluntary sign of any sort. Hans tapped +2, whereupon Mr. Grabow put a number of similar questions; but I no +longer thought of the answers, and all of Hans's responses went wrong. + +Although Hans was not influenced by others so long as a suitable +experimenter was present, yet he might be disturbed and under certain +conditions might be led to make the back-step in response to certain +movements in his environment. The person to whom he responded would have +to be close to the experimenter and would necessarily have to execute a +movement greater in extent than the experimenter's. In such instances +the raising of the head, arm or trunk, was a sufficient stimulus. Thus +we made the following two series of tests. Mr. Stumpf stood with trunk +bent forward before the horse, and at a moment decided upon beforehand, +assumed an erect position. I myself stood beside Hans and asked him to +tap. When I stood at the horse's neck, then Mr. Stumpfs interruption was +effective. When I stood at the horse's flank, the interruption effected +only a seeming hesitation, and when I moved still farther back, the +horse continued to tap despite any attempted disturbance. In the second +series the questioner remained constantly at the right shoulder of the +horse, while the one who attempted to distract him, changed positions. +When the latter stood to the right immediately in front of or beside the +questioner, the disturbance was effective in 10 out of 13 cases. But +when he stood back of, and to the right of, the questioner, the attempts +at disturbance were seldom successful. If he chose a place before and to +the left of the horse, there was hardly any distraction (in 4 cases +only, out of 13), and if he stood to the left and behind the animal, he +exerted no influence whatever. Hans manifestly turned his attention, +almost exclusively, to the side at which the questioner stood. + +That knowledge of this _modus operandi_ made it possible for those +persons to get responses from the horse, who hitherto had been +unsuccessful, is shown in the case of Mr. Stumpf when he began to +control his movements voluntarily on the basis of observations which had +been made. + + +_II. Problems which Hans solved by movements of the head._ + +We are here concerned with the horse's head movements upward, downward, +to the right and to the left, and also with nodding and shaking of the +head to signify "yes" and "no". We soon discovered that these +experiments, also, were successful without an oral statement of the +problem,--in other words, the auditory stimulus was quite superfluous. +The tests with the blinders showed that Hans was lost as soon as his +questioner was out of his view, but responded adequately the moment the +questioner was in sight. Hans, therefore, had established no idea of any +sort in connection with the terms "up", "down", etc., but in these +cases, likewise, he reacted in response to certain visual stimuli. The +nature of these stimuli I discovered at first in my observations of Mr. +von Osten and also of myself, when working with the horse. + +Above all things it was necessary that the questioner, during these +tests, should stand perfectly erect. If he stooped ever so slightly, the +test was unsuccessful. If he carefully refrained from any movement +whatsoever, and looking straight before him asked the horse, "Which +direction is right?" or "Which way is upward?", Hans would execute all +sorts of head movements without rhyme or reason. It was evident that he +noted that a head movement of some kind was expected of him, but did not +know the particular one that was wanted. But if the questioner now +raised his head, Hans would begin to nod and would continue doing so +until the questioner lowered his head. This reaction was interpreted as +signifying "yes". Mr. von Osten had always asked Hans before each of the +more difficult tests whether he had comprehended the meaning of the +problem, and was reassured only upon seeing the horse's affirmative +response. But contrary to Mr. von Osten's expectation, Hans also +responded in this manner after a pair of ear-caps had been drawn over +his ears. In the case of the tests described at the beginning of the +chapter, in which the method was that of "procedure without knowledge", +Mr. von Osten had always insisted that we await Hans's nod of +comprehension before proceeding. We complied; Hans nodded and--regularly +disgraced himself! + +When the questioner raised his head somewhat higher than normal, Hans +would throw his own upward, which was supposed to signify "upward". A +lowering of the head on the part of the questioner was followed by a +lowering on the part of Hans, which was his form of response for "down". +For some time I was in a quandary as to the difference between the +questioner's signal for this latter response and the one which was the +signal for the horse to begin tapping, although I had often given both +kinds unwittingly. Further experiments showed that Hans responded with a +nod of the head whenever the questioner, while bending forward, chanced +to stand in front of, or to the side of the horse's head, but that he +would begin to tap in response to the same signal, as soon as the +experimenter stood farther back. The difference in the two signals, +therefore, was very slight, and I repeatedly noted that instead of +tapping, as he had been requested, Hans would respond to the Count zu +Castell's and Mr. Schillings' questions by a nod of the head. + +If, while standing in the customary position to the right of and facing +the horse, the questioner would turn his head a little to the right--a +movement which, when seen from the horse's position, would appear to be +to the left,--Hans would turn his head to his left. But if on the other +hand the questioner would turn slightly to the left,--i. e. seen from +the horse's position, to the right,--then Hans would turn his head to +his right. And finally, whenever the questioner turned his head first to +the right, then to the left, Hans would respond by turning first to his +left, then to his right. This, according to Mr. von Osten, signified +"zero" or "no". Since this movement could not be executed by the +experimenter while in a stooping position, it can now readily be seen +why it was that Hans, instead of shaking his head, always began to tap +whenever a placard with "O" upon it, was shown to him in the course of +the experiments in which the method was procedure without knowledge on +the part of the questioner. The latter expected the horse to tap, and +therefore bent forward. Like all of the horse's other forms of response, +this, too, was always unsuccessful whenever the questioner stepped +behind the animal. Although Hans had always responded to Mr. von Osten +and Mr. Schillings, and at first also to me, by means of the stereotyped +movement of the head to the right and then to the left to signify "zero" +or "no", I later succeeded in controlling my signals so as to get the +inverted order in the horse's response. In the case of Mr. Schillings +and of Mr. von Osten all of the movements just described were very +minute, and long after the movements, which were effective stimuli for +releasing the process of tapping, were recognized, it was still +exceedingly difficult to discover them in these two gentlemen. The +signal for "zero" and "no" was relatively the most pronounced of the +group in the case of Mr. von Osten, while with Mr. Schillings it was the +least pronounced, in comparison with his very strong "jerk". Yet in both +cases Hans responded with absolute certainty. + +It is now readily conceivable how it was possible to make the horse +respond to all sorts of foolish questions, both by involuntary signs--i. +e., expressions following upon the bare imaging of the response +expected,--as well as by means of controlled signs. One could thus +obtain consecutively the answers "yes" and "no" to the same question. Or +one might ask: "Hans, where is your head?", and Hans would bend to the +earth. "And where are your legs?" He would look at the skies. Etc. + +Let us examine for a moment the directives which the horse required for +the various positions. If one called him, while he was running about the +courtyard, he paid no attention whatever, but if one beckoned to him, he +came immediately. A raising of the hand brought him to a standstill. If +one now stepped forward or pointed one's hand in that direction, he +would step forward, or _vice versa_, he would step backward. By means of +minimal movements of the head, of the arm nearest the horse, or of the +whole body, Hans could be induced to assume the position one desired, +without touching him or speaking a word. I noticed this quite early in +the course of the investigation. Once, when intending to ask the horse +to step backward to the right, I inadvertently said "Step backward to +the left!", whereupon he stepped backward to the right. In spite of my +verbal error, I had involuntarily given him the proper directives. + +Finally we may note that Mr. von Osten had occasionally asked the horse +to jump or to rear. The command in this case was: "Jump", or the +question was: "What do the horses do in the circus?". Since these tests +were just as effective when the command was given silently, it was an +indication that these, too, depended upon visual stimuli. What was +necessary to cause the horse to step backward and then jump forward was +to step backward oneself, or make a slight movement of the hand in that +direction. If one wished to make him rear, it might be effected by +throwing the arm or head slightly upward. + + +_III. Problems which Hans solved by approaching the objects to be +designated._ + +The method pursued in these tests was the following: From five to eight +pieces of colored cloth 1/2 × 1/4 meters in size were arranged in +changing series upon the ground, the interval between them being equal +to the width of one piece, or else they were hung upon a string a man's +height above the ground. This method was also employed when placards of +like size with written symbols were used. The horse stood ten paces away +and opposite the middle of the series, while Mr. von Osten stood at his +right. Hans was asked to go and point out the cloth of a certain color +or the placard with a certain word upon it. If the cloth lay upon the +ground, Hans picked it up with his mouth and carried it to the +questioner. If the cloth, like the placards, hung from the cord, he +approached, pointed it out with his nose and then backed up to his +original position. Before approaching the objects, Hans was required to +indicate, by tapping, the number of the place in the series (counting +from left to right), which the cloth or placard occupied. Mr. von Osten +never omitted this requirement. Then the command "Go!" was given, and +Hans obeyed. (As a matter of fact, a slight directive movement of the +head or hand was just as effective as the spoken command). + +The following cases, chosen in a haphazard fashion, show that the +horse's indication of the object's place in the series, by means of +tapping, was by no means a guarantee that he would point it out +correctly. Five placards hung from the cord. Mr. von Osten asked: "What +is the position, counting from left to right, of the placard which has +the word 'aber' inscribed upon it?". Hans answered: 3. (It was indeed +the middle placard.) Then he was commanded: "Go!". Thereupon Hans went +straight to the fourth placard. On another occasion Hans happened to +drop a brown cloth upon a black one. His master asked him: "In which +place are there two cloths?". Hans responded correctly, "In the second +place". To the question "Which of the two is the black one?" he also +answered rightly: "The lower one". Upon being asked to get it, he +brought the white cloth. + +The large number and the irregularities of the errors showed that there +was no manner of intelligence involved in the pointing out process. Thus +during the two months of our experimentation Hans was asked twenty-five +times by Mr. von Osten to bring the green cloth. Only six times did he +succeed in the first attempt, while in five instances he selected an +orange-colored cloth, four times a blue, three times a white one. + +The fact that the errors were equally distributed over the tests with +the colored cloths and those with the placards is strong evidence that +the horse's response involved no intellectual process, for if that were +the case, then the responses in the tests with the placards would have +been very much more difficult, for they would have involved the ability +to read, whereas the tests with the colored cloths demanded only that a +few names be remembered. Nevertheless, the horse was as unsuccessful in +tests of one kind as he was in those of the other,--even when Mr. von +Osten acted as questioner. (50% failures in 78 placard tests; 46% +failures in 103 color tests.) + +The fact that commands which were purposely enunciated poorly, or else +not spoken at all, were executed with just as much accuracy as those +given aloud, strengthened us in our supposition. On one occasion I +placed a blank placard with the others. When I ordered him to approach +_tabula rasa_, he invariably went to the right one. The following +illustrates how he fulfilled quite nonsensical commands. A series of +blue and green cloths lay upon the ground. Being asked where the black, +the orange, and the yellow cloths lay, Hans shook his head +energetically, i. e. they were not there. And yet, upon being asked to +bring them in the order named, he regularly brought one of the blue +ones. + +All this goes to show that Hans did not know the names of the colors (to +say nothing of the symbols on the placards). It was plain that here +also, as in all the other cases, he was controlled by signs made by the +questioner, the nature of which I soon discovered. Standing erect, Mr. +von Osten always turned head and trunk in the direction of the cloth or +placard desired. Hans, keeping his eye on his master, would proceed in +that direction. Even after he had already started out, thanks to his +large visual field one could control his direction by turning slightly +more to the right or to the left. If, however, he had already arrived at +the row of placards or cloths, this method ceased to be effective, for +then he could no longer see the experimenter. It made no difference +whether the cloths lay on the ground, or were suspended, like the +placards. + +The following fact justifies the conclusion that the bodily attitude of +the questioner was the effective signal. The more numerous the cloths, +or the nearer they were placed together, the more difficult one would +expect it to be for the horse to select the one indicated by the +experimenter. Such was indeed the case, for the number of errors +increased with the number of cloths presented. + +But no matter how many cloths there might be, or how closely they might +be placed, it was always possible to indicate either end of the row, for +in that case one had merely to turn to the extreme left or the extreme +right, and might even turn beyond the row. Hans seldom failed in these +cases, whereas he made many errors when cloths or placards within the +series were wanted. + +To turn from the nature and number of Hans's errors, to their +distribution,--observation proved the hypothesis that the nearer two +cloths lay together, the greater was the chance of their being mistaken +one for the other. If we designate as "error 1" all those cases in which +Hans went to cloth II instead of to cloth I, cloth III instead of cloth +II, to V instead of IV, etc., and as "error 2" when he mistook III for +I, IV for II, in fine, whenever he went two places too far to the right +or left, and as "error 3" whenever he went three places too far to +either side of the cloth desired, we find the following grouping of +errors: + + With Mr. von Osten, a total of 63 errors: + 73% "error 1" + 21% "error 2" + 4% "error 3" + 1% "error 4" + 1% "error 5" + + With Mr. Pfungst, a total of 64 errors: + 68% "error 1" + 20% "error 2" + 11% "error 3" + 1% "error 4" + 0% "error 5". + +The most frequently recurring error, therefore, was the one in which the +horse, instead of going to the cloth desired, approached the one +immediately adjacent. On page 79 I said that Hans's errors were without +system, but only in so far as it was impossible to explain them on a +basis of the colors which seemingly were mistaken one for the other. A +part of a series in which Mr. von Osten acted as questioner may serve as +an illustration. The order given is that of the experimental series as +it occurred. Five colored cloths were used. + + Color of the cloth + asked for: blue, brown, brown, brown, brown, brown, green, green. + | | | | | | | | + brought: orange, orange, green, green, yellow, green, blue, orange. + + Place of cloth + asked for: V II II II II II III III + | | | | | | | | + brought: IV IV III III I III V IV + +The interpretation of this series which it would be hard to explain by a +reference to the colors which were mistaken, is simply this: Cloths +lying near together were regularly mistaken on the part of the horse. + +Experimental control of the questioner's movements decided the question. +If the questioner at first indicated the proper direction and then +turned about after the horse had already started forward, he was as a +rule misled. When the questioner did not face the cloths at all, but +turned away at right angles, or when he turned his back upon them, Hans +was completely at sea. If, on the other hand, the cloths were arranged, +not in a row, but in several heaps, so that one might turn to a +particular heap, but could not indicate a particular cloth, then Hans +would regularly go to the proper heap, but would always bring forth the +wrong cloth. After much persuasion Mr. von Osten consented to make a +series of these tests himself. Hans's failures were deplorable. He would +take up first one cloth then another, turn again to the first, etc. We +would mention, however, that this apparent searching was not done +spontaneously, but in response to Mr. von Osten's calls, such as "See +there!", "The blue!", etc. Every time Mr. von Osten called, Hans would +drop the cloth he was holding in his mouth, or he would turn away from +the one he was about to grasp, and would then try another one. + +In addition to these visual signs, the horse received auditory signals +in these tests, (as in all others in which he was required to bring +objects). As soon as the questioner noticed that Hans was about to take +up the wrong cloth, all that was necessary to make him correct his error +was to give some sort of an exclamation, such as "Wrong!", "Look, you!", +"Blue!", etc. Hans would pass on as long as the calling continued. If +he was picking up, or about to pick up, a cloth when the exclamation was +made, he would go on to the next; but if, at the time he was on his way +to a certain cloth, he would change his direction in response to the +call. If he stood before one of the pieces at the time, but had not +lowered his head, he would pass on to the next. In all this he would +adhere to a certain routine of procedure. If he was approaching a series +from the right, then a call would cause him to turn to the left, if he +was coming from the left, he would turn to the right. If he had +approached the row of cloths near the center, he would turn, in response +to the questioner's calls, to the left,--seldom, very seldom, to the +right. Mr. von Osten did not seem to be able to control the responses of +the horse, entirely. As a rule, but not always, one call sufficed to +make Hans pass on to the next cloth. If too many calls were given, he +would often go too far. Loud exclamations were superfluous. + +These statements are not mere assertions, but are founded upon the +records of the results. The tests in which calls were made show a larger +percentage of correct responses than do those without calls. Of a total +of 103 tests with colored cloths, which Mr. von Osten performed for us, +only 37% brought forth successful responses on the part of the horse +when visual signs were the only directives and when there were no +directions by means of calls, whereas the total percentage of successful +responses was 54%, if we add to the above those in which the vocal +exclamations helped to bring about success. The corresponding +percentages for the total of 78 tests with the placards were 23% and +50%. In a total of 110 color tests I myself obtained 31% correct +responses under the first head, and 56% under the second head. In a +total of 59 tests with placards I succeeded in getting 31% correct +responses under the first head and 46% under the second head. We must +note that without verbal admonition only one-third of the tests brought +forth correct responses, whereas one-half succeeded when those in which +calls were used, are added. Still, this is a relatively poor showing. In +the most favorable series that Mr. von Osten ever obtained in our +presence--and there was only one such--50% of the responses 'without +admonition' were correct, and 90% when all the correct reactions, both +with and without admonition, were taken into account. + +Not all the places in the row required the same amount of assistance by +means of calls. Those positions which needed the most help, were those +which it was most difficult to indicate to the horse by the visual sign, +i. e., the attitude of the questioner's body. We noted above (page 81) +that the cloths at either end of the row were less difficult to point +out than those nearer the middle. If our hypothesis holds true, we would +expect that the end cloths would involve fewer auditory signals in the +process of pointing out, and those within the row a greater number of +such signs. By way of illustration, I will cite one series of tests in +which Mr. von Osten was questioner, chosen not because it is most +conformable to my hypothesis but because it is the longest (48 +consecutive tests with five cloths) which I have. In the upper row I am +placing the successful responses without auditory signs, in the lower +those involving both auditory and visual signs. + + Place of the cloth : I II III IV V + No. of sucessful } visual signs only : 5 2 1 2 4 + responses. } visual and auditory signs : 5 5 8 5 5 + +We see that without verbal admonition the first and last places are most +favorable for success, the second and fourth far less, and the middle +least favorable. These differences disappear when admonitions are +introduced, for all of the places then have the same number of correct +responses with the exception of the middle, which now has even more than +the others. + +One more experiment which I made will close the discussion. The +following colors were placed from right to left: orange, blue, red, +yellow, black, green. I turned my back upon them, and therefore could +guide the horse by verbal commands only. I asked him to bring the +orange. Hans approached the yellow. I now called three times, allowing a +short interval between the calls. At the first "Go!" he passed from the +yellow to the red, at the second from the red to the blue, and at the +third from the blue to the orange, which he then proceeded to pick up +and bring to me. I had noted this same thing in Mr. von Osten's tests, +although there, there were often other factors entering in. By +exercising the utmost precision in facing the cloths, and by using, in +addition, suitable oral signs, I succeeded in getting Hans to bring, +successively, each one of the six cloths in the row, and without a +single error,--and all this in the presence of Mr. Schillings who did +not have the slightest notion of the secret of my success. + +We need hardly say, in passing, that all that was true of the tests with +colored cloths, was also true of the tests in which the placards were +used. It was all the same to the horse whichever was placed before him. + +We have thus tested all of the horse's supposed achievements. None of +them stood the critical test. It would have been gratifying to have +repeated some of the experiments and to have made Hans the object of +further psychological investigations, but unfortunately he was no longer +at my disposal after the publication of the report of the +December-Commission. Some may say that we have had almost enough of a +good thing, but we must bear in mind that many of the tests which were +carried out,--such as those in which the method was that of "procedure +without knowledge", those in which the ear-muffs were used, those in +which distractions were introduced,--had previously been made by other +persons (see pages 41f, 45, 63), and with other results, than ours. A +more thorough test, therefore, would have been doubly desirable. + + + + +CHAPTER III + +THE AUTHOR'S INTROSPECTIONS + + +In the preceding chapter we asked: What is it that determines the +horse's movements? Independent thinking, or external signs?--We found +that it was solely external signs, which we described as certain +postures and movements of the questioner. Beyond a doubt these necessary +signs were given involuntarily by all the persons involved and without +any knowledge on their part that they were giving any such signs. This +is to be seen from their statements, which cannot be cavilled at, as +well as from the fact that several of them even to-day still doubt the +correctness of the explanation which we are here offering. I myself for +some time made these involuntary movements quite unwittingly and even +after I had discovered the nature of these movements and had thus become +enabled to call forth at will all the various responses on the part of +the horse, I still succeeded in giving the signs in the earlier naïve +involuntary manner. It is not easy, to be sure, to eliminate at once the +influence of knowledge and to focus attention with the greatest amount +of concentration on the number desired, rather than upon the movement +which leads to a successful reaction on the part of the horse. To some +this may appear impossible, but those who are accustomed to do work in +psychological experimentation, will not deny the possibility of such +exclusive concentration upon certain ideas. + +If we now ask: "What occurred in the mind of the questioners, while they +were giving the signs?", the answer can be found only by way of the +process which in psychology is technically called "introspection", i. e. +observation of self. In the following we will give the most important +results of this process of self-observation, which took place in the +same period in which the observations recorded in the preceding chapter +were made. + +My first experiments were made while the horse was counting or solving +arithmetical problems and were as follows: Mr. Schillings, who was alone +with me in the horse's barn, asked me to think of several numbers, +maintaining that the horse would be able to indicate them correctly upon +being asked. He stood to the right of the horse, I stood erect and at +the side of Mr. Schillings. There was no one else present. Somewhat +skeptical in attitude, I concentrated my mind consecutively on five +small numbers. Hans tapped one of them incorrectly, one correctly and +three by one unit too many. At the time I considered these attempts as +unsuccessful and credited some curious chance with the answers which +were correct, or nearly so. This was a mistake, for often during the +following days, and in the absence of Mr. von Osten, the horse would +give correct answers. Others, of course, would be incorrect, and usually +the mistakes would be by one unit,--so that I soon saw that even in the +horse's errors there lay some system. It will be seen that Hans +responded to me from the very beginning, undoubtedly because I had had +the opportunity of watching Mr. von Osten and Mr. Schillings and had +thus patterned my behavior after theirs. I was not at first successful +in getting the horse to respond correctly in the case of large numbers. +For in order to get complete control over the horse, and, what was, as +I later discovered, more to the point, control of myself, some practice +was needed. But I was able to work with the horse quite successfully, +while I was still in the dark as to my own behavior. + +From the very beginning Hans responded as promptly to those questions +which I articulated merely inwardly, as to those which were spoken +aloud. That all formulation of the question was unnecessary, however, +was shown by the following experiments. If, for example, I did not think +of any particular number until after the horse had begun to tap, and +then fixed upon 5, he would tap 5. If, however, I told him to count to +6, but gave no further thought to the command after he had begun +tapping, I would get an entirely wrong response. It was easy to obtain +any answer one wished to a question, simply by focussing consciousness, +with a great degree of intensity, upon the answer desired. Thus Hans +answered my question: "How many angles has a hexagon?", first by 6, then +2, then 27, in accordance with the numbers that came into my mind. The +animal always followed the ideas which were in the questioner's mind, +and never his words, for it was with the former that the movements upon +which the horse depended were bound up. + +It was not enough, however, simply to imagine the number desired. It was +furthermore necessary that the questioner be conscious of the moment +when the horse reached that number. Larger numbers (above 6) were +therefore, successful only when every single tap was inwardly counted to +the end. The manner of counting was indifferent. Thus I counted 6 as +follows: 1, 2, 3, 4, 5, 6, and later: 6, 5, 4, 3, 2, 1, and then again: +6, 6, 6, 6, 6, 6. Finally I used the Greek letters and also nonsense +syllables. And in all cases I obtained six taps, the correct response. +If, however, I simply counted the taps without knowing when the desired +number was reached, the responses were always incorrect, e. g., I +counted + + For No. 10: 10, 10, 10 continuously, Hans tapped 13, + " " 10: 1, 2, 3 to 10 " " 10, + " " 12: 12, 12, 12 continuously, " " 15, + " " 12: 1, 2, 3 to 12 " " 12. + +In the case of smaller numbers, on the other hand, one often obtained +correct results without counting. In this I am borne out by Mr. +Schillings. It was merely necessary to image vividly the number 3, or 4, +or even the name of a week-day or of a month without the number which +would indicate it. In the last of these cases the number corresponding +to the day or the month (e. g. 3 for Tuesday, 5 for May, etc.), though +not consciously presented, still evidently lay at hand in the +subconscious. To use a popular expression, I usually had a "feeling" +when Hans had arrived at the right number. + +It was furthermore found that it was not only necessary to count to, or +to think of, the number desired, but that this must take place with a +high degree of tension of expectancy--that is, a strong affective +element must enter in. The state required for a successful response was +not the mere passive expectation that the horse would tap the number +demanded of him nor the wish that he might tap it, but rather the +determination that he should do it. An inward "Thou shalt", as it were, +was spoken to the horse. This affective state was registered in +consciousness in terms of sensation of tension in the musculature of the +head and neck, by intraorganic sensations, and finally by a steadily +rising feeling of unpleasantness. When the final number was reached, the +tension would suddenly be released, and a curious feeling of relaxation +would ensue. I have made a series of tests to determine the most +favorable degree of tension in expectation. It was possible to +distinguish with certainty, three degrees of tension besides the state +of utter relaxation,--all of which I measured by means of the +differences in the sensations of tension. In cases of tension of the +first degree (greatest concentration) the responses were usually +correct, a few, however, were lacking by one unit. There was therefore +in the latter instance a premature release of inner tension. In cases of +tension of the second degree all answers were correct except a very few +which were too great by one unit. In cases of tension of the third +degree, many answers were wrong, and usually by several units too many. +I wished to have the horse tap 10, with the lowest degree of +concentration. He tapped 13, then in a repetition of the test, 12. I +thereupon increased the tension, Hans then tapped 8. I decreased the +tension once more, but so that it was somewhat greater than at first. +Hans tapped 10 correctly. At another time I tried to have him tap the +number 5, with a low degree of tension. He tapped 6. I intensified +expectation and Hans tapped 4. I again decreased it, and he tapped 5, +_comme il faut_. Apparently, therefore, the most favorable degree of +tension was one between the first and second,--the latter being the +least favorable. After some practice a lesser degree than was used in +the beginning sufficed to evoke adequate reactions. The flow of nervous +energy to the motor centers of the brain evidently became facilitated +through practice. It will be easy to understand why the first days of +experimentation caused intense headaches, which later never occurred. + +Whenever, in the foregoing, we spoke of a certain degree of +concentration which had to be attained, it is not to be understood that +the same tension had to be maintained throughout the test, from the +horse's first tap to his last. But rather, that it began with a low +degree, and gradually increased as the final unit of the count was being +approached. It may best be represented by a curve whose maximum +represents that degree of tension which we have been discussing. The +rise to this maximum which, when attained, was followed by a sudden +fall, did not always occur in the same manner. Three types of curve may +be distinguished, which were first discovered in purely empirical +fashion, and later reproduced voluntarily for purposes of +experimentation by diagramming before each test the intricate curve of +the varying degrees which the intensity of concentration was to assume. +The types may be described as follows: + +I. Here the tension curve rises steadily from beginning to end. This +type preponderates in the case of small numbers. Thus, when I asked the +horse: "How much is 2 plus 4?", the tension increased slowly with every +tap from the moment I began counting, until the final tap was reached, +when it was again relaxed. Externally this relaxation is noticeable as a +slight jerk. + +II. In this case the curve does not rise at an equal rate, but rather +more slowly at the beginning and later undergoes a sudden increase, or +the tension increases immediately at the beginning, remains constant for +some time and then ascends to the maximum. This curve is the rule in the +case of large numbers and evidently means economy of physical energy, +for experience soon taught that a steady increase in tension from the +very beginning soon brought it to a level which cannot be long +maintained and usually leads to a premature relaxation. In the case of +very large numbers the alternation of the slight and the sudden increase +may be repeated several times, and at times it may even sink below a +level which has already been attained, thus making a wave-like curve. + +III. The third type of curve shows a sudden jump between two units at a +certain point in its course. This may occur in the case of both small +and large numbers but only when the highest or first degree of +concentration is employed (see page 91). Such a jump frequently occurs +in the transition from the tap preceding the last to the last one which +is being eagerly expected. Relaxation--with the upward jerk and raising +of the head--here occurs at the normal time; Hans taps to the end with +his right foot. Oftener still the "jump" described occurs while passing +over to the number just before the last. The goal seems within reach and +the mental tension relaxes, and with it the physical tension,--the head +gives a slight jerk and Hans makes the back-step. Since, however, +another tap is still awaited with some degree of tenseness and, since +complete erection of the head does not follow immediately upon the jerk +of the head, the horse gives another tap with the left foot. Thereupon +occurs the complete relaxation of attention, and the assumption of the +erect posture on the part of the questioner. That this is +psychologically the clue which leads to the final tap, will readily +appear from the following remarkable fact: I was able to bring about at +will either the back-step with the right foot, or the additional extra +tap with the left foot by concentrating the mind either upon the last +unit or upon the one just preceding it. In either case the movement +which served as stimulus to the horse followed naturally upon +concentration on the number. I could of course also control the response +by direct voluntary control of the movements involved. Hans thus solved +for me the same ten problems first with the back-step, then with the +extra final tap. + +Finally we will indicate the one true inner cause of the difficulty in +getting the number 1 as a response. It is not easy to relax attention +immediately after having just begun to concentrate. Relaxation, +therefore, often occurs with a certain retardation, and the result is a +belated jerk of the head. + +Briefly, I would also mention a few of the more interesting +introspective observations which were made in situations in which the +horse responded with movements of the head for answers such as "yes" and +"no", "up" and "down", etc. From the very beginning I put questions to +Hans which would have to be answered by a shake of the head. It often +happened that instead of indicating "0", Hans would begin tapping some +number. But the wonder of it was that, in many cases, he responded +properly. I knew only that I inwardly pronounced the word "null" (zero), +and that I looked expectantly at the horse's head. In the case of +questions to which I expected the answer "yes" or "no", I imagined +myself enunciating the answer, i. e., I used motor imagery. The tests +failed, the moment I employed only visual or auditory imagery, whereas, +motor imagery was always effective in calling forth correct +reactions.[M] When the proper response was "up" and "down" I would +think of those directions in space, and likewise with "left" and "right" +in which case also I would put myself in the horse's place. + + [Footnote M: Thus it is possible to think of the word "no" in three + different ways. I may get a visual image of the written or printed + word, or the auditory image of the word as spoken by another person, + or finally I might think of it in terms of images of the sensations + of movement which would arise if I myself were to enunciate or write + the word. And so, in like manner, I could think of any other word in + terms of either visual or auditory or motor imagery. In all + probability the auditory and motor always occur together,[6] but + still it is possible to make the one or the other predominate. + + It appears that the imagery of most persons is a mixture of + auditory-motor and visual elements, with a predominance of one or + the other kind. Individuals who utilize almost exclusively the + visual (as does the author, as a rule), are rare. But rarer still is + the pronounced motor type.] + +While I was still ignorant of the nature of the necessary movements, the +tests were successful only when I had put the question aloud or in a +whisper, but never when I failed to enunciate, i. e., when I merely had +the question in mind ("in idea"). But this also became possible after a +little practice, although I could not then give an explanation for my +success. Except in one instance, we could discern no difference between +problems spoken and those merely conceived by Mr. von Osten who had had +the advantage of long practice. But the one exception deserves mention. +The old gentleman commissioned Hans, presumably without uttering a word, +to step backward to the left. Hans thereupon responded by giving his +entire repertoire, as follows: He moved his head to the right, then to +the left. Then he leaped forward and repeated the same movement of the +head. Hereupon he stepped backward and signified a "yes" by a movement +of the head. He then lowered his head and made two leaps forward. After +this performance Mr. von Osten repeated the same command aloud, and in +every case Hans responded properly. Again the silent command was given +and again the horse responded with the series of reactions described +above, lowering his head leaping forward, etc. In this experiment, +without exception, the spoken command evoked adequate reactions,--the +silent command, an incorrect response. Evidently the impulse to movement +was not so great with the mere conceiving of "right", "left", etc., as +when the words were enunciated. It, therefore, required some practice on +my part before a sufficiently strong movement-impulse became associated +with the idea. All this is in no wise at variance with the fact that +tests involving counting and computation were as successful when the +problem was given in silence, as when it was spoken. The signs for +tapping, viz.: inclination and erection of the head and body, followed +the question. The question therefore became superfluous. On the other +hand the signs for head-movements on the part of the horse, were given +while the question was being put. I ask, which way is "upward", and at +the same time I look upward. In this case therefore the question itself +is not entirely insignificant.--I experienced greater difficulty in +getting Hans to respond with the head-movement to the left. After much +practice I was able to evoke this movement by means of giving the +command aloud, but never by means of the "silent" command. Accidentally +I hit upon a device by means of which I attained this end also. I asked +the horse aloud "Which direction is left?",--whereupon he reacted +properly; then I immediately repeated the question silently, and was +successful every time. My mental attitude here was still the same as +when I put the question aloud. What sort of an attitude this was, I +could not, of course, have stated explicitly at the time. I could not, +therefore, awaken it at will,--and if I allowed but a minute to elapse +between the spoken and the silent question, the vivid after-effect (the +so-called "primary memory image") soon disappeared and the test was +wholly unsuccessful. Practice, however, soon helped me to overcome this +last difficulty also. I believe that my inability to evoke this specific +reaction on the part of the horse, lay in the unfavorable position which +I assumed, for it did not allow the horse to perceive my movements +easily. For the same reason, Hans would at first indicate "no" and +"zero" by turning to the right, seldom to the left. + +As in the case of counting, a high degree of concentration was also +necessary here, but with this difference, that here attention was +directed to ideas present to the mind, ("yes", "no", etc.), whereas in +the counting process attention was directed toward expected sensory +impressions (i. e., the taps of the horse). + +All that has been said thus far is readily understood psychologically. +The following curious fact, however, is noteworthy. Hans used the +head-movement to indicate two such different concepts as "zero" and +"no"; it appeared therefore that in both cases he was receiving the same +kind of directive. Observation proved that such was the case and the +directive in question was none other than an imitation in miniature, or +rather a movement anticipatory of the expected head-movement of the +horse. Now, whereas the signs for "up", "down", "right", and "left" were +natural expressive movements which are normally associated with the +corresponding concepts, this cannot be said to be true of "no" and +"zero". My laboratory observations (see page 107) lead me to conclude +that the movements, by means of which the concepts "no" and "zero" are +naturally expressed, are quite different; and neither of these +corresponds to the signs for "zero" and "no" which the questioner +involuntarily gave to Hans. What was the genesis of these unnatural +forms of expression? If we might assume that the questioner always had +in mind the movement he awaited on the part of the horse, and never +thought of "zero" or "no", then the contradiction would solve itself. +But I must deny decidedly that I ever thought of the movements of the +horse's head, and Mr. Schillings, whom I questioned on this point, +agreed with me in this, in so far as his own mental processes were +concerned. I can see nothing for it but that in this instance the +expressive movements normally connected with the concepts "zero" and +"no" have been replaced by other forms, without the questioner becoming +aware of it. That such displacements may occur, has been shown by the +tests described on pages 107 to 112. That they did occur in this +instance may be concluded from the following observation. In responding +to me, as well as to Mr. Schillings, Hans always moved his head first to +the left, then to the right, never in the opposite order. That this was +_not_ a peculiarity of the horse, but must be ascribed to the signs +which were given him, is shown by the possibility of inverting the order +under experimental control (page 77). Frequently Mr. Schillings and I +had seen the horse respond to his master by means of such +head-movements, and the order was always, without exception, the one +mentioned. It must be assumed therefore that the horse's movement, which +we so often noticed, made such an impression upon us, that afterwards it +was regularly reproduced on our part quite unconsciously, so that Mr. +Schillings never, and I only after a long time, became aware of the +whole process. + +In closing, just a word as to the discovery of our own movements. I soon +noticed that every pronounced raising of the head or trunk brought about +an interruption in the horse's response. But only by observing the +final movement in the case of Mr. von Osten did I discover that I, too, +performed a slight erection of the head. Observation of others was less +difficult than the observation of one's own movements. As in the case of +all other signs given to the horse, these movements were so slight that +they were prone to escape notice even though one's whole attention were +concentrated upon their detection. I also questioned whether in my +attempts to disturb the horse by means of loud calls, it were really the +call or some simultaneous involuntary movement which was the true cause +of the interruption. The doubt was justified, for when I finally learned +to cry out vehemently without making the slightest move, all my crying +was in vain. Also it had seemed to me at first as if I were able to +induce the horse to rear, not only by means of the proper sign or +movement, but also by a mere command, but I found later that in every +case there was always some movement, were it ever so slight. Finally I +tried to simulate voluntarily the oft-mentioned involuntary jerks of the +head. Although it is not very difficult to execute them at will with +almost the same minuteness as when they were performed involuntarily, I +still did not succeed in getting a series of such jerks of equal +fineness throughout. In spite of (and partly on account of) the most +concentrated attention, there would be from time to time a jerk of +somewhat greater extent and energy. As soon as the movement had been +executed, I was able to form a good judgment as to its relative extent, +but I was unable to regulate the impulse beforehand. + +With the following comment the chapter will be concluded. Introspections +are necessarily subjective in character. If they are to possess general +validity, they must be borne out by evidence furnished by others--and +this to a greater extent than is necessary for other forms of +observation. It was hardly possible to get corroboration from the other +persons who had worked with Hans, for, although some of them were +excellent observers of external natural phenomena, few of them had had +the necessary amount of practice in introspection. The necessary +confirmation, however, was had in laboratory tests, which we shall +presently describe. + + + + +CHAPTER IV + +LABORATORY TESTS + + +The tests which are to be briefly reported here, were begun in November, +1904, and were carried out at the Psychological Institute of the +University of Berlin. The purpose was twofold: first, to discover +whether the expressive movements noted in Mr. von Osten, Mr. Schillings, +and others, were to be regarded as typical and to be found in the +majority of individuals,--and secondly, to ascertain in how far the +psychical processes which I had noted in my own case and which I +believed to lie at bottom of these movements, were paralleled in, and +confirmed by, the introspections of others. The effort was made to make +the experimental conditions as nearly as possible like those under which +the horse had worked. The affective atmosphere which colored the +situations in which the horse took part, could not, of course, be +transferred, but this was in some respects an advantage. One person +undertook the rôle of questioner, another--myself--that of the horse. +The experiments fall into three groups, corresponding to the types of +the horse's reactions: 1, tests in counting and computation; 2, tests in +space reactions; 3, tests in fetching or designating objects. + +In the experiments in counting and computation, the questioner, standing +at my right, thought with a high degree of concentration of some number +(usually between 1 and 10, but sometimes also as high as 100), or of +some simple problem in addition. Then I would begin to tap,--but in +human fashion with my right hand, rather than with my foot--and +continued until I believed that I had perceived a final signal. I thus +tested, all in all, twenty-five persons, of every age and sex (including +children of five and six years), differing also in nationality and +occupation. None of them was aware of the purpose of the experiments. It +could not escape them, to be sure, that they were being watched. It was +also evident to them that the things noted were certain tensions and +movements; but none of my subjects discovered what the particular +phenomena were that I was looking for. Only in a few isolated instances +did they report that they were conscious of any movements on their part. +With the exception of two persons, they all made the same involuntary +movements which were described in chapter II, the most important of +which was the sudden slight upward jerk of the head when the final +number was reached. It was at once evident that the direction of this +jerk depended upon the position which one had asked the subject to +assume at the beginning of the test, the direction changing whenever the +position was changed. Thus, if the subject stood with head bowed--the +body either being held erect or likewise bowed,--then release of tension +would be expressed physically by an upward jerk. (Occasionally the +entire trunk is slightly raised, so that it was possible to observe this +physical reaction when standing behind the subject). If the subject had +bent his head backward, the "psychological moment" was marked by a +forward movement, (although under certain conditions the head was, in +such a case, observed to bend still farther backward). If during the +tests the head was bent slightly to the right, then the reaction was +expressed in a movement toward the left, and _vice versa_, if it had +been on the left, it was bent to the right. If the subject had been +bending his head forward and to the right, he then raised it upward and +to the left, etc. In all of these changes of position I noticed an +intermediate posture which, to be sure, it was not always an easy matter +to discover,--viz.: an upright position in which there was discernible +no manner of head-movement or only a slight tremor. If the subject was +lying on his back with his head supported, then there was noticeable a +very slight movement to one side. In this same way a number of other +positions were tested in order to discover for each the characteristic +movement expressive of release of tension. It would therefore appear +that the raising of the questioner's head, which served as the signal +for stopping for Mr. von Osten's horse, was but one instance of a +general law which may perhaps be stated thus: The release of muscular +tension which occurs with the cessation of psychic tension, tends to +bring about that position of the head (and body) which, at the time, +represents the slightest amount of muscular strain.--These movements +seldom were pronounced enough to be compared to motion through a +distance of one millimeter, in a very few cases only did they attain to +the magnitude of one or two millimeters: I failed to note them entirely, +however, in only two individuals, two scientific men whose mode of +thought was always the most abstract, and one of these was, in spite of +repeated attempts, unable to elicit any response whatever on the part of +the horse. + +In the cases of the more suitable subjects I was able to indicate not +only the number they had in mind, but also the divisions in which the +number was thought, thus 12 as 5 and 5 and 2, or the same number as 2 +and 5 and 5, and I was also able to determine the addends in the +addition--i. e., whether the problem had been conceived as 3+2=5 or as +2+3=5. It frequently happened that in the beginning I would sometimes +mistake these subdivisions, which were recognizable by the less +pronounced jerks, for the final number. Thus I would often respond with +4 instead of 8, or 3 instead of 9, or with 3 when the problem was 3+2, +just as Hans had so often done. In these tests, too, the difficulty of +getting the number 1, as well as the larger numbers, came to light. Thus +three times in succession 17 was indicated as 4, as 9, and as 17. But +after some practice I was able to give numbers as high as 58 and 96. The +frequency of the errors of one unit too many and of one unit too few is +also noticeable in these tests. + +We also found desirable corroboration, by trustworthy subjects, of the +introspective observations of the author, which were reported in Chapter +III, with regard to the significance of concentration and the curve of +attention. It is hardly necessary to mention that no attempts were made +to influence the subjects in their accounts by asking suggestive +questions. The most valuable feature about these tests was that the mute +horse had now been replaced, as it were, by an animal capable of speech, +and that it was now possible to follow the same process both from within +and from without. Two illustrations may be welcome. The one who took the +part of the horse gave three taps and made the following entry: "At 3 I +saw a slight upward jerk of the head on the part of the questioner". The +questioner however had thought of 4, and made the following note, +without knowledge of the other's entry: "I was aware of extreme tension, +so that it was impossible for me to get beyond 3". Or again, the +'horse', reacting to a movement on the part of the questioner, stopped +at 3, but the latter, having intended to obtain 2, made the following +entry: "I noted clearly that I ceased thinking of the number too late, +and did not put on the brakes, as it were, until I had arrived at 3". We +see that errors here were entirely the fault of the questioner, just as +had been the case in the tests with Hans. (See page 151f.). + +In a second group of experiments I asked a subject to fix his mind upon +certain concepts, such as "up", or "down", "right" or "left", "yes" or +"no", and others, in any order he pleased, but with the greatest +possible degree of concentration. The subject each time had the choice +of four or six concepts, and he was told to think of one of them at the +signal "Now!". How he was to 'think' the concept was left entirely to +him. He was also told to interpolate the series with a 'blank', that is, +to think of nothing at all. Standing opposite the subject, I tried to +guess at the mental content of the person's mind, on the basis of +expressive movements. Sometimes I reacted by shaking or nodding the +head, etc., just as Hans had done, but as a rule I was content to say +the word which I thought the subject had in mind. With twelve subjects +(a total of 350 tests) I made an average of 73% correct responses, and +in the more favorable cases I attained even 90 to 100% correct +responses. Very slight involuntary movements of the head and eyes, which +showed but little individual variation, and always occurred when the +subject began to fix upon the concept, were the signs which I used as +cues. As in the case of the movements expressive of the release of +tension, which I discussed above, these movements, too, occurred without +the subject being aware of them, (except in those rare cases in which +they had once or twice been especially pronounced). Indeed, it was very +difficult and in some cases almost impossible for those persons whom I +had initiated into the secret, to inhibit them voluntarily. "Up" and +"down", "right" and "left", were expressed by movements of head or eye +in those directions, "forward" by a forward movement of the head, "back" +by a corresponding movement. "Yes" was accompanied by a slight nod of +the head; "no" by two to four rapid turnings of the head to either +side.[N] "Zero" was expressed by a movement of the head describing an +oval in the air. Indeed, it was even possible to discover whether the +subject had conceived of a printed or a written zero, for the +characteristics of both were revealed in the head-movements. I was able +later to verify this graphically. With Ch. as subject, I made 70% +correct interpretations in a total of 20 tests; with von A. as subject, +72% in a total of 25 tests. And finally I was able to interpret the +signs without any errors at all. It was not absolutely necessary to look +directly at the subject's face. Even though I focussed a point quite to +one side, so that the image of the subject's face would fall upon a +peripheral portion of my retina, I still was able to make 89% correct +interpretations in a total of 20 tests.--This is not astonishing after +all, when we recall that the periphery of the retina possesses a +relatively high sensitivity for movement impressions, although its +chromatic sensitivity is very low.[O] + + [Footnote N: It was Charles Darwin[7] who first pointed out that the + expressive movements (of the coarser sort) to be noted in nearly + every race and people show a great, though by no means complete, + similarity. The similarity is most pronounced in the shaking of the + head to signify negation and nodding to denote affirmation. It will + be noted that the former is essentially of the nature of a turning + toward, and the latter a turning away.[8] These same movements have + been reported in the case of the blind and deaf Laura Bridgman,[9] + and we have been explicitly assured that they were a spontaneous + development, and not acquired by imitation. For it is by imitation + and never before the completion of the first year, that our children + acquire these movements. On account of his unreliability, we can put + but little stock in the statement of Garner,[10] a writer on the + speech of monkeys, that these same gestures have been observed in + the case of those animals. My experiments show that the same + movements, greatly diminished in scope, as a rule accompany the mere + thought of "yes," "no," etc. I cannot, however, regard the assertion + as an established fact that every thought process whatsoever is + connected with some form of muscular movement, as has been + generalized by the French physiologist Féré,[11] and the American + psychologist Wm. James.[12]] + + [Footnote O: The productions of mind-readers, so-called, also, are + based upon the perception of involuntary movements, insofar as they + are not based upon pre-arranged schemes and trickery. But there we + have to do principally with tactual perception, since the reader + touches the hand of the subject and is guided by its tremor. Some of + the expert mind-readers, however, conduct tests without touching the + subject. They depend chiefly upon auditory impressions: the sound of + footsteps,[13] involuntary whisperings[14] and the changes in the + subject's respiration[15] and the murmuring of the spectators. To a + less degree visual signs also are involved: posture and facial + expression of the subject, and movements of eyes and lips.[16] Even + the heat radiating from the person's body is supposed to have some + influence.[17] And my own experience has taught me that surprising + results may be obtained by the utilization of the movements + described in the preceding chapter. + + It may be that these truly microscopic movements also play some part + in bringing about the success of some of the experiments in + telepathy, so-called, (transference of thought from one person to + another, ostensibly without any mediation of the senses known to + us.) In spite of the huge mass of "experimental evidence" which has + been collected, chiefly in England and in America, it appears to me + that telepathy is nothing but an unproven hypothesis based upon + experimental errors.] + +It was assumed, as indicated on page 99, that in the case of Mr. +Schillings and myself the movements naturally expressive of "zero" and +"no" had been displaced--without our being aware of the fact--by +others, viz.: those which the horse required as directives for his +reactions. Since this was the case, we tried to discover if a similar +displacement could be brought about experimentally. The attempt was +successful and we discovered that under suitable conditions we could +cause the subject--quite without knowledge on his part,--to establish an +"association" between any given concept and any given expressive +movement. The following experimental series will serve to illustrate +this fact. + +I had one of the subjects (von A.) think of "left" and "right" in any +order he chose. (The command was purposely given only in a general way: +"Think of 'right' or 'left'".). We had agreed that I was to try to guess +the mental content of the subject's mind, but I was not to utter a word. +Instead, I was to indicate "right" in every case by an arm movement +downward, and "left" by a movement upward. To the subject I gave a +fictitious but plausible reason for all this. The behavior of the +subject took the following course: In the first three tests he moved his +eyes to the right when he thought of "right", and to the left when he +thought of "left". This was the normal expressive movement. In the +fourth test, however, the thought "left" was accompanied by an upward +movement of the eyes. Two further tests again showed eye-movements to +the right and left. In the seventh test with the idea "left" the eyes +moved first to the left and then immediately upward. In the following +ten tests the eyes were turned regularly upward at the thought of +"left", and downward at the thought of "right", with only one exception +which was a normal movement to the left. The normal expressive +movements, therefore, were displaced by the artificial, after the +seventh test. + +In the case of another subject (B.) in whom normally the thought of "up" +was accompanied by a slight raising of the head, and "down" by a +downward movement, these natural forms of expression disappeared +entirely as a result of my arm movements to the right to indicate that I +inferred his having in mind the thought of "up", and to the left when I +inferred that he was thinking of "down". Instead, there appeared not +merely the desired movements to the right and left, but rather movements +upward to the right and downward to the left. That is, instead of a +complete displacement of the old by the new, there occurred a +combination of the two. + +A third type of result appeared in still another subject (Ch.), who +normally expressed the concepts "right" and "left" by eye or head +movements (never both kinds at the same time) to the right and left. +Here my arm movements up and down caused the eye and head movements to +be made simultaneously, so that the thought of "right" found expression +in an upward movement of the head and an eye movement to the right, and +the idea of "left" in a downward head movement and a movement of the eye +to the left. The subject had no knowledge of this process, and it took +six tests to bring about the new reaction. From that point onward the +new movements were so well established that, depending upon them for my +cue, I was able to make 32 correct inferences in a total of 40 tests. +During the latter part of this series I blindfolded the subject, so that +I could not see the movements of his eyes, and therefore had to base my +inference entirely upon his head movements.--After removing the bandage, +at the end of the series, I told the subject that I would go through +another series, in which I intended to indicate his thought of "right" +by an arm movement downward (instead of upward as heretofore), and his +thought of "left" by a movement upward. (This he regarded as an idle +whim of mine). It was only after the twelfth test that the former +"association" which I myself had caused to be established, was +completely displaced by the new. The thought of "right" was now +accompanied by an eye movement to the right and instead of a raising +there was a lowering of the head. A corresponding change occurred in the +head movement expressive of the thought of "left". These responses were +occasionally varied by some in which only the head movement or only the +eye movement occurred. But these movements were always to the right, or +downward and to the right, at the thought of "right",--and to the left, +or upward and to the left, at the thought of "left". In ten tests I made +ten correct inferences. After the new association appeared firmly +established, I ceased responding by means of arm movements, and +indicated my 'guesses' by word of mouth. At first the newly acquired +movements continued to appear promptly in the subjects. But gradually +they tended to become more uncertain and finally disappeared, as readily +as they had appeared, and the normal conditions were once more +established. Nor was there any tendency to reappear on the following day +in another series of tests. (Those just described had been made on one +day in the course of an hour or two). But as soon as I again used the +earlier method of arm movement to indicate my inferences (raising the +arm for "right", lowering it for "left"), the former artificial +association was again established, although not until some 14 tests had +been made,--during which the normal movements to the right and left were +often inhibited and during which the conditions were, on the whole, +chaotic. The new association, thus re-established, remained constant +during the ten tests of the remainder of the series, but has very +probably again disappeared long ere this. In the case of this subject it +appears therefore that the new associations were superimposed upon, but +in no sense displaced, the normal expressive movements. Nor did the two +coalesce (except in a few exceptional cases), but tended as a rule to +occur independently of one another. + +I would emphasize once more that none of the subjects had any knowledge +of the purpose or meaning of the experiments. Also, I was convinced by +questioning the subjects afterwards that none of them--and this is the +essential point--had merely conceived of the arm movement which they +were expecting me to make, instead of concentrating thought upon the +idea of "right" or "left". On the contrary, all of them considered my +particular movements mere vagaries and without purpose, and they felt +perfectly certain that they were in no wise influenced by these +movements. Also, none of the subjects was conscious of any movements on +their part, except one, who was at times aware of her eye movements to +the right, but never of those to the left, (see page 111), nor of the +head movements which for us constituted the phenomena of prime interest. +When I asked my subjects what they believed to be the cue upon which I +based my inferences, they invariably responded with probable +explanations which were always wide of the mark, and those to whom I +disclosed the cue--(after the experiments were completed), were +thoroughly astonished. + +In the tests just described we had to do only with such ideas or +concepts as normally were associated with some stereotyped form of +expressive movement (see page 106). I now chose a group of ideas which +are not normally associated with a particular form of motor expression +peculiarly characteristic of them, and sought to establish artificially +such a connection with some arbitrary movement, without consciousness of +the process on the part of the subject. Thus I asked one subject (Miss +St.), who had no intimation of the aim of the tests, to think of the +following words in any order she might choose: "Ibis" (ibis), "Irbis" +(panther), "Kiebitz" (plover) and "Kürbis" (pumpkin). I said that I +would react to her thoughts by means of arm movements forward and +backward to the right and to the left, respectively. 15 out of 20 tests +were successful, without the slightest suspicion on the part of the +subject (whose whole attention was concentrated on the word-content), +that she was giving me the necessary directives in the form of very +minute movements of the head and eyes to the right and left, etc. She +was greatly astonished that I should be able to guess words so much +alike,--(she did not know that the element of likeness was productive of +no difficulty). When, during one of the tests, the subject happened to +think spontaneously of the movement she was expecting me to make, she +became confused, and as a result the number of my sucessful reactions +suddenly fell. I never would have discovered the cause, had not the +subject enlightened me without my asking. + +I repeated this series with three other persons, who had had some +psychological training. I did not use the same movement for each word in +all three cases, but indicated the word "Kiebitz", for instance, by +means of an upward movement in one case, by turning the head to the +right in another, etc. In one of the three cases the tests were almost +wholly unsuccessful. The cause for this came to light later, but it +would involve too much exposition to discuss it at this point. In the +case of the other two persons, the tests were successful beyond +expectation. I had made my various arm movements only a few times when +they presently began to raise their heads slightly when thinking of +"Irbis", and to move it to the right at the thought of "Kürbis", etc. In +the two series of 35 tests I did not have a single error. In a number of +instances I succeeded in guessing the word upon which the subject had +decided, even before the test proper was entered upon--i. e., before the +signal for concentration had been given. Nothing surprised a subject +more than the remark: "You are intending to think of the word 'Kürbis'", +or "You had thought of concentrating your mind upon 'Ibis' but later +decided in favor of 'Kiebitz'", yet nothing could be more simple. Before +every test the subject would consider what word he would fix upon, and +while he was saying to himself "I will choose 'Ibis'", the proper +movement would accompany his decision, although it was only very slight, +because attention had not yet attained the degree of concentration which +was employed in the test proper. + +In these experiments also, the subjects, whom I know to be absolutely +trustworthy, declared that they never thought of the arm movements which +I was to make. They regarded them as being quite irrelevant. Also--with +but one exception--they thought of the objects, in so far as they imaged +them visually, as being directly before them, and not off in the +direction indicated by my arm movements. Thus they did not image the +plover ("Kiebitz") as being on the wing, when I raised my arm, or as +resting on the ground, when I pointed downward, etc. One of the subjects +had done this occasionally, but by no means regularly. He was therefore +asked to localize all objects in the same place, i. e., directly in +front of him at the level of the eye. He complied with this request, but +no change, whatever, was observed to occur in his expressive movements. + +In order to overcome the difficulty just mentioned, I selected another +subject (Miss von L.), whose power of visualizing was very slight, and +requested her to fix her mind upon four words which I had selected +because they were not, necessarily, associated with a particular image. +The order in which the words were to be thought of, was entirely +optional on her part. The words were "Form", "Inhalt", "Mass", and +"Zahl", (form, content, measure, and number), and each of them I +accompanied, with a certain definite arm movement. The subject always +pronounced the word inwardly as emphatically as possible, but without +ever imaging the corresponding arm movement. Often, it must be noted, +she did not know whether or not the movement which I made was the proper +one. And yet she, too, soon fell into line in the matter of executing +unconsciously the characteristic head movements. In a total of 50 tests, +I was able to make 10 correct guesses in the course of the first 20 +tests, 8 in the next 10 tests, and 19 in the last 20 tests. Miss von L. +noted only a few of her upward head-movements, viz.: those that were +especially pronounced (movements through about 2 millimeters), but of +the others she knew nothing. The same experiment was repeated with a +psychologist, well-trained in introspection, as a subject. Success was +even greater here. But no matter how closely the subject observed +himself, he was unable to solve the puzzle. + +Variations which were introduced in these tests, I will only mention in +passing. Thus, instead of making an arm movement, I, in some cases, +would tap with my foot, for "Ibis" once, for "Kiebitz" twice. The +subject could not see my feet. The involuntary movement-expression which +became associated with "Ibis" was one nod of the head, with "Kiebitz" +two nods, etc. Here our only concern was to show that unconscious change +in natural expressive movements and the acquisition of artificial ones +are possible in the case of psychically normal subjects trained in +introspection. + +I was not satisfied with convincing myself subjectively of the facts +indicated, but sought to fix them objectively, by means of a graphic +method. For this purpose I used the device mentioned by Prof. R. Sommer +for the analysis of expressive movements.[18] The purpose for which +Prof. Sommer's apparatus had been constructed, was to record the +involuntary tremor and movement of the hand. These movements, of course, +take place in the three dimensions of space. By means of three levers it +is possible to record the movements upon the flat surface of a smoked +paper fastened to the revolving drum of the kymograph, the movements in +each direction being recorded by a separate lever, in such a way that +the three curves thus made represent the analysis of a single movement +into its three dimensional components. By making slight changes, which +tended to complicate the experiment somewhat, I adapted the apparatus to +the measurement of movements of the head. The method of experimentation +was the following. The subject whose movements were to be registered, +was placed in the device in such a way that his trunk and head were bent +slightly forward, the latter a little more than the former. This, it +will be remembered, was the usual position of the questioner when +working with the horse. Three levers were attached to his head in such a +way that every movement backward or forward would act upon the first +lever, every movement to the right or left would move the second, and +every movement of the head upward or downward would be recorded by the +third. With regard to the sensitivity of the machine, micrometric +determination showed that when the subject was properly installed, +movements through so small a distance as 1/10 millimeter could be +accurately ascertained. The subject was carefully instructed to remain +as quiet as possible, but without constraint. Voluntary movements were +thus obviated. But the question arose: were not the involuntary +movements thus suffering a loss?--And it was upon them that we were +experimenting. The question cannot be put aside summarily, but +experience taught us that the movements in question, nevertheless, did +appear quite effectually, if one could have the right kind of subjects +at one's command. We need hardly mention that besides the two persons +immediately concerned--I, myself, attended to the apparatus--there was +no one else present, and that the subject was not allowed to see the +curves produced on the kymograph. Besides the registration of the +head-movements, I also undertook to register the respiratory-movements +of the subject. This was done by means of the so-called pneumograph, +attached to which was a lever recording the thoracic expansion and +contraction. This was for the purpose of ascertaining the relationship, +which might eventually be found to exist, between the release of psychic +tension, on the one hand, and respiration, on the other. + +The subject was now told to think of some number, which, of course, was +unknown to me. At a given moment I was to tap upon one of a series of +keys arranged like those of a piano, with the middle finger of my right +hand--corresponding to the right forefoot of the horse. The questioner +observed my key, I, his head,--just what had happened in the experiments +with Hans,--and as soon as I perceived the involuntary closing signal I +reacted upon it by releasing, suddenly, another key upon the same +keyboard, which I had in the meantime been pressing down with my second +finger, thus marking what with Hans had been called the backstep. Each +key was connected with a separate electro-magnet, and these in turn with +markers, in such a manner that pressure upon the keys closed two +electric circuits and, releasing the keys, opened them, and both the +closing and the opening were recorded upon the smoked paper by means of +the markers. And, finally, in order to ascertain the time relations of +all these processes, a time-marker indicated the time in fifth-seconds +upon the revolving kymograph record. The time-curve was recorded just +below the other curves. + +Of the curves[P] thus obtained under the most equable conditions +possible, we publish seven which show the great general uniformity of +the tests made upon the horse with those made in the laboratory. The +rôle of questioner was undertaken at different times by Mr. Schillings +and the students of philosophy, Messrs. von Allesch, Chaym and K. Zoege +von Manteuffel. To all of them I am greatly indebted for their unselfish +services in these laborious tests. The experiments with von Allesch and +Chaym, who were among the most suitable of my subjects, were conducted +absolutely without knowledge on their part of the nature of the +phenomena which I was observing. Neither of them knew anything about the +expressive movements in which they were unconsciously indulging, and +furthermore, since they kept their heads bowed during the entire course +of these experiments, they did not perceive what it was that I was +observing. It is interesting to note that Chaym on the occasion of his +only visit to the horse, immediately received a number of correct +responses. Without a doubt von Allesch would have met with equal +success. The other two subjects (von M. and Sch.) went through this +series of tests, possessing some knowledge of the nature of the +movements involved. Conditions were such that they (and especially Mr. +Schillings) could not be prevented from obtaining some knowledge of the +essentials, at least. However, it would be wrong to suppose that for +this reason the results were more favorable, owing, mayhap, to voluntary +efforts on the part of the subject. The contrary was true. The two +subjects who had no knowledge of the character of the reactions upon +which my responses depended, retained their normal habits, unchanged, +throughout the series,--whereas the last-named two, afraid lest their +knowledge vitiate the result, lost more and more of their power of +concentration and within a short time were in a condition of tense +inhibition, which is all the more conceivable, since they had had no +psychological training whatever.[Q] + + [Footnote P: For registering the curves a Hering kymograph was used, + with a loop 2-1/2 metres long. The kymograph rested on felt. With + the aid of the Marey model a pneumographic record was taken now of + the thoracic, now of the abdominal, breathing, never both + simultaneously, since this was extrinsic to my purpose, and it would + have made the whole experiment too complex. The time was recorded by + means of the Jacquet chronograph. For purposes of making more exact + measurements the acoustic current interrupter of Bernstein was used, + attuned to 100 vibrations per second. But this necessitated such + rapid revolution of the drum of the kymograph that the curves were + not compact enough for purposes of demonstration. The levers were + all fitted with micrometer adjustments. They wrote tangentially and, + except the one registering the breathing curve, all points lay in + one vertical line. The error of deflection and that due to the + rondure of the writing-surface were both very slight on account of + the comparative length of the levers and the small extent of the + excursions, and for that reason synchronous points lie practically + in one perpendicular. Only the breathing curve has been moved + somewhat to the left, 7.5 millimeters in figures 6 and 7, 2 + millimeters in figure 8, 4.5 millimeters in figure 9. (When the + breathing was very profound, as occasionally happened, the error of + deflection would, of course, have to be taken into account.) The + curves here used as illustrations have been reproduced in the exact + size of the originals by the zinco-graphic method, though somewhat + compressed vertically in order to economize space.] + + [Footnote Q: My own expressive movements, on the other hand, are as + pronounced as ever. I still find the attempt to suppress them as + difficult now as when I was working with the horse (page 57). I + could not, of course, procure a curve of these movements of my own.] + +Their movements, which at first were quite profuse, decreased more and +more, so that in the case of von Manteuffel the percentage of my +successful responses sank from 73% correct responses in 90 tests to 20% +in a total of 20 tests,--and in the case of Schillings from 75-100% to +23% in a series of 35 tests. The curves obtained with von Manteuffel as +subject, which I am here publishing (figures 8 and 15), are, however, +true to his normal habits. The same is true of the two first curves of +Schillings (figures 10 and 11), whereas the third (figure 12) shows +distinctly the traces of the state of inhibition into which he fell, and +represents the same condition as when Mr. Schillings, while preoccupied, +tried to work with Hans. All the finer details of the phenomena in +question, were likewise unknown to these two subjects. + +For purposes of a clearer understanding of the various curves, figure 5 +is inserted to give the general scheme of their arrangement. + +[Illustration: FIG. 5.] + +All curves are to be read like script from left to right. The first is +the breathing curve of the questioner, the second, third and fourth +curves represent his head movements,--all translated through the +workings of the levers into up-and-down movements. The objective +direction of these head movements is indicated by the arrows. It will be +noted that (because the lever in question was one with two arms, and +therefore reverses all movements made) each lowering of the head is +indicated by a rise in the fourth curve, and each raising of the head is +recorded by a sinking in the same curve. The records of the head +movements forward and backward and to the left and right (curves 2 and +3) are two and one-half times the size of the actual movements; while +the curve of the movements up and down (curve 4)--which is of especial +interest to us--is five times its actual size. The fifth and sixth +curves, which record my own responses, represent the taps of the +horse,--the fifth indicating the number of taps and the sixth the +back-step, which was Hans's reaction when he noted the head-jerk of the +questioner. The seventh, the lowest line, indicates the time in +fifth-seconds. Since the rate at which the drum revolved was not uniform +for all the tests, the fifth-second marks do not appear the same +distance apart in all the records, but are farther apart the greater the +rapidity with which the drum revolved. For the experiment itself this is +quite immaterial. Figures 6 to 9 correspond in detail with the diagram +just described. Figures 10 to 12 differ only in that the breathing and +back-step curves (the first and sixth in the diagram) are lacking. In +these there is no response on my part to the head-jerk of the subject, +but tapping was continued _ad libitum_ (in the case of the illustrations +here given I tapped to 5). When these latter curves were taken the +ordering and the technique of the experiments had not yet been +perfected. When this was finally done, Mr. Schillings, who acted as +subject in those tests, had to be eliminated from the ranks of +appropriate subjects on account of the increasing inhibitions, which +gradually developed as described on page 120. + +Analysis of such curves is rather difficult, and those of different +subjects cannot be directly compared. It is necessary to make a study of +the normal curve of each subject taken when his affective state could be +described as "indifferent". The influences of the purely physiological +processes, such as pulse[R] and respiration, must also be determined. +And even so, an interpretation of the curve becomes possible only when a +large mass of material is at hand, and when the introspections of the +subject are taken into consideration. The following remarks, therefore, +are not based solely upon the illustrations given, but upon the mass +total of my results. + + [Footnote R: Slight head movements accompanying the pulse-beat were + until recently regarded as the symptom of certain diseases of the + vascular system (the so-called symptom of Nusset), but H. Frenkel + has now shown them to exist also in normal individuals.[19] I myself + discovered such movements (lateral as well as sagittal) more or less + pronounced in all the curves obtained from my subjects. The most + striking case was that of a young physician whose circulatory system + was perfectly healthy. In most instances I was able to note these + oscillatory movements directly and to count them without much + difficulty. For purposes of control the radial pulse was always + determined at the same time. The observation of the phenomenon + appears to be especially easy in the case of somewhat full-blooded + individuals.] + +In beginning our analysis, let us take first the breathing curve. Our +results here were quite in accord with the view taken by Zoneff and +Meumann,[20] who believe that in the respiration is to be found a good +index of the affective tone of the subject's mental state. In the +greater number of cases it was possible to conclude as to the degree of +concentration of attention,--and when this was very great, it was even +possible to get a clue as to the number thought of. Since the high +degree of tension, under which a subject labored during a test, would be +accompanied by strong affective coloring, we cannot regard as normal any +of the curves here reproduced (with the exception of the two high points +in figure 9). Although breathing was always deep and regular before and +after a test, during the test it was less deep and irregular. Very often +it was suspended altogether (figures 7, 8 and 9). In ordinary life we +often notice that highly concentrated attention is usually accompanied +by non-voluntary inhibition of movements in the musculature which, for +the moment, is not directly involved; the man lost in thought slackens +his pace and finally stands still, the intent listener or looker-on +holds his breath. + +Of the three curves registering the movements of the head, we find that +nothing peculiarly characteristic is revealed by the two upper ones, +giving the movements up and down, and to the right and left, +respectively. They are the ordinary tremor-like movements and indicate +nothing beyond the fact that the subject is unable to hold his head +absolutely quiet for even one second. It is the third line that is of +interest to us, for it is here that the oft-mentioned head-jerk (which +indicates arrival--in the counting--at the number expected) registers +itself. The moment of the head-jerk corresponds, almost without +exception, with the moment of the first deep inhalation,--just as one +would be led to expect from common experience. But we are not to regard +the head-jerk as a result of the inhalation, for it also occurs when the +subject complies with the request that he hold his breath during the +test. The actual height of the jerks recorded in figures 6 to 12 was +1/4 to 1-1/2 millimeters and the average height obtained from the forty +curves of these four subjects was 1 millimeter. There is great +individual variation: the greatest height that was obtained from the +records was 2-3/10 millimeters, the lowest 1/10 millimeter. The +variations within the records of the several individuals are +comparatively slight and are evidently dependent, in the main, upon the +degree of concentration of attention. Thus in the case of von Allesch, +where in 75 tests the average height of the jerk is 1 millimeter, the +mean variation is 4/10 millimeter. If, in order to obtain some idea of +the size of Mr. von Osten's movements,[S] we compared the values gained +in the laboratory with those which would probably obtain in his case, we +would say that his head movements were more minute than almost any of +those of which we obtained records. At the most they could not have been +more than 1/5 millimeter (when measured in terms of the distance through +which the brim of his broad hat moved, they would appear to be about +1-1/2 times as large. See page 49.) The movements of Mr. Schillings, on +the other hand, were certainly four or five times as great as those of +Mr. von Osten, and occasionally even greater than that. When we turn to +consider the time-interval elapsing between the subject's final +head-jerk and my reaction (as recorded in the sixth curve), we find +that the reaction-time averages 3/10 seconds, a value which agrees very +favorably with that estimated for the horse (page 56). Thus it appears +that man and beast have the same reaction-time--though we must bear in +mind that I worked under some difficulty, since I had to care for the +apparatus. + + [Footnote S: In a special series of experiments a subject was + instructed to execute rapid head movements as minute and as evenly + as possible. These were registered objectively and at the same time + I made judgments concerning them. The results showed that my + judgments were most exact in the case of the most minute jerks. The + thing that made it especially easy to judge the movements of Mr. von + Osten under normal conditions, (page 220), was their extraordinary + evenness, such as I have not met with in any other individual.] + +Let us now turn to a discussion of the several figures. + +Figure 6 (von Allesch) gives a typical view of the great, and at the +same time economic concentration of attention characteristic of the +subject. Respiration (first curve) is not so profound as usual, yet is +changed very little. The head-jerk (fourth curve) is of medium height. +It occurs just at the proper moment,--the subject had thought of 2, and +had directed his attention economically. This attention was of the kind +described as type I on page 93. The lowering of the head, (recorded in +the figure by a rise in the curve), immediately following upon the +head-jerk upward, is irrelevant. + +In figure 7 (Chaym) we have a record of a different nature. Respiration +was inhibited throughout the test,--(the small waves are due to the +pulsating of the heart); immediately after the test deep breathing takes +place. Tension steadily increased till 3, the number expected, was +reached. The head, accordingly, gradually sank a little forward. The +head-jerk ensued during an interval beginning just before the reaching +of the goal and ended immediately after. The movement was predominantly +backward, its upward direction being only through a distance of 1/4 +millimeter. (This subject was not so strongly motor as the preceding +one.) The reaction followed promptly as seen in curve 6. It was the +decided raising of the head which follows the head-jerk, that prevented +the usual back-step with the left foot, when the subject was working +with Hans. + +[Illustration: FIG. 6.] + +[Illustration: FIG. 7.] + +Figure 8 (von Manteuffel) is typical of strong and at the same time +economical concentration. Respiration, normally deep and very regular, +is for a time completely inhibited. Tension rises steadily and the head +gradually inclines forward. In the interval between the number before +the final one and the final one the subject makes a sudden bend forward +and immediately upon reaching the final number gives a violent jerk of +the head, upward. The attention here would be characterized as being of +type III, described on page 94. (Owing to lack of space it is impossible +to give an example of type II, which is only to be found in the case of +very large numbers.) + +Figure 9 (von Allesch) is expressive of great, but--according to the +subject's introspection--not economical concentration. Respiration, +which before and after the test was quite regular, during the test +itself shows a pause. (The tiny waves are due to the heart-beat.) The +subject had thought of 5, and this number is accompanied by a decided +head-jerk. But we note that even before the final jerk a number of less +pronounced jerks occur--the result of poorly regulated psychic tension. + +[Illustration: FIG. 8.] + +[Illustration: FIG. 9.] + +Figure 10 (Schillings) depicts a very high degree of uneconomical +concentration. There was sudden concentration at the beginning of the +test, and a steady increase throughout its course. Accordingly Mr. +Schillings bent forward at the start, and inclined still farther +forward at the second--and just before the third--tap. But at 3 there is +a sudden upward jerk. The number thought of had been 4, tension +therefore had exploded, as it were, too soon. + +[Illustration: FIG. 10.] + +Figure 11 (again of Schillings) gives indications, on the other hand, of +a medium and economic concentration of attention, which is more normal +in character. The number thought of was 4. + +[Illustration: FIG. 11.] + +Figure 12 (Schillings again) is indicative of a low degree of psychic +tension. With the very first tap the head begins to rise and continues +to do so throughout the test. A true final jerk does not occur, we note +rather in all three curves registering the head movements, slight +time-marking movements, especially in the second curve. In the third +curve they are at first minute, but increase steadily in size until the +fourth tap, after which they suddenly disappear. The subject had, as a +matter of fact, thought of the number 4, but it is hardly probable that +Hans would have reacted properly upon these stimuli. + +[Illustration: FIG. 12.] + +Mr. Schillings had thought of the same number in all three tests given +in figures 10, 11 and 12. The probabilities are that if he had been +working with the horse at the time, in the first case Hans would have +reacted with three taps with the right foot and a final tap with the +left, as a result of the questioner's bending forward again after the +premature head-jerk at 3. In the second instance the horse would +probably have given four taps with the right foot, and in the third, the +chances are that he would have continued to tap beyond the 4. + +These curves give, on the whole, a fair idea of the intensity and of the +course of attention of the various subjects. + +Let us now consider a number of records which illustrate the expressive +movements involved in the process of thinking of such concepts as "up", +"down", etc. Their arrangement is identical with the scheme given in +figure 5, with the exception that the tapping curves (the sixth and +seventh) do not appear. The subject was asked to think of any of the +words "up", "down", "right", "left", "yes", "no", etc. He was to begin +to conceive them vividly when the command "Now!" was given. This moment +is recorded in figures 13 to 15 on the fifth curve. What has been said +on page 123 with regard to respiration, holds also in these instances: +only the first rise recorded in figure 14 can be regarded as normal. +The magnitude of these movements varies between 1/2 and 3 millimeters. +The records of the subject whose movements were most extensive, show an +average of 1-7/10 millimeter (based on 50 tests), with a mean variation +of 6/10 millimeter. Lack of space precludes the reproduction of more +than three records. + +Figure 13 (von Allesch) shows the movement accompanying the thought of +"up", a slight raise of the head, recorded in the fourth curve. (The +thought of "down" is accompanied by a corresponding downward movement.) + +[Illustration: FIG. 13.] + +Figures 14 (von Allesch) and 15 (von Manteuffel) illustrate the nod +which is associated with the thought of "yes" in the case of two +subjects. It is essentially the same in both: the head is lowered and +then raised. The first of the two subjects is more decidedly motor, and +his movements therefore were somewhat the more extensive. In the case of +the second subject the nod proper is followed by another which is +somewhat less extensive. + +[Illustration: FIG. 14.] + +[Illustration: FIG. 15.] + +A number of other experiments were carried out which corresponded with +the color-selecting tests made upon Hans. (Page 78.) Five sheets of +white paper, 1/2 meter long and 1/4 meter wide, were arranged in a +series upon the floor, 1/4 meter apart. A dot marked the middle of each. +The experimenter stood at a distance of 7-1/2 meters and directly +opposite the middle sheet. At about 1/2 meter to the right or left of +him stood the subject who took the part of the "horse". The problem of +the experimenter was to indicate to the "horse" a certain one of the +five sheets, but without the use of word or gesture. I at first +undertook the rôle of "horse", whereas the others consecutively played +the part of questioner. All of them looked fixedly at the sheet which +they had in mind. Besides, it usually happened that they would turn at +least their heads, and often their bodies, more or less in the direction +of the particular sheet--and this without purpose or knowledge on their +part, but purely as a result of concentration upon the sheet they wished +me to point out. One of the experimenters remarked, quite casually, +that he had noted that I always made a better judgment, the more +intently he thought of the sheet. Others often admitted that, when I had +made an error, they had not imagined the sheet vividly, or had been +debating whether or not to decide to think of the neighboring sheet--the +one I had designated. This indecision could be noticed by the direction +of the eyes. But the following table shows how uniform, on the whole, +was the behavior of the various persons when under the guidance of the +same impulse. The number of tests was 200 in each case. All errors were +of the same character. Neighboring sheets were mistaken for each other, +and the errors were never of more than one position to either side. +Their number can easily be obtained by subtracting the percentage of +correct inferences from the total, 100%. + + Experimenter: v. A. B. C. Mrs. v. H. K. Miss v. L. + Correct inferences: 88% 88% 77% 81% 77% 82% + +It will be seen that the number of correct interpretations is quite high +and in none of the cases does it deviate far from the mean average of +82%. + +I based my judgment as to the direction of the subject's eyes, upon an +imaginary line perpendicular to the center of the cornea. (This +perpendicular does not always coincide with the subject's line of +vision, which was the thing I was after, but this cannot be directly +obtained. This, of course, was what made the judgment a rather difficult +matter.) My judgment as to the direction of the head I based largely on +the direction of the nose, (to express it more accurately: upon the +direction of the median plane.) I purposely noted only the position of +the experimenter and not the movement which led up to it. When I tried +to do the latter, the results were not always satisfactory, because the +head and eyes of the person would frequently, in the process of +adjustment, move beyond the goal and thus lead me into error. An attempt +was made to make each judgment as independent as possible of the +preceding one. But usually, after a few tests, an unintentional +association became established between certain attitudes and the +different places in the series of papers. Often all that was necessary +was to observe the experimenter in order to know which of the places he +had in mind, it was not necessary to look at the papers at all. Every +change in the position of the person would, of course, make the +association thus established, useless. + +Later, the subjects and I changed rôles, I took the part of the +experimenter and they the part of the "horse". The number of tests in +each case was 200 as before. Here, too, errors were, with but one +exception, never more than of one place to either side. Whether the +error was one place to the right or one place to the left appeared to +depend upon the position of the person making the judgment, i. e., it +depended on whether he stood at my right or at my left. The following +results were obtained: + + Subject ("horse"): v. A. B. C. Mrs. v. H. K. Miss v. L. + Correct inferences: 76% 79% 75% 81% 77% 74% + +A certain agreement can be seen in these results. The average of correct +inferences is somewhat lower than that which was obtained by me (page +135), 77% as over against 82%. This is probably due to the fact that the +subjects had had so little practice compared with me. + +With one of these subjects, Mr. Koffka, a student of philosophy, I +carried these tests somewhat further, varying them partly by increasing +the number of sheets of paper, partly by decreasing the distance between +them. The increase in the number of sheets made only a slight difference +in the results. With 200 tests in each case I obtained the following +results: + + No. of sheets : 5 6 7 8 9 10 + Correct inferences: 77% 72% 72% 69% 73% 68% + +With but few exceptions, the errors were, as a rule, of one place. The +series with an odd number of sheets (5, 7, 9) gave better results than +those with an even number (6, 8, 10). In the tests with the odd number +of sheets the experimenter (K.) stood in front of the middle sheet, so +that it was at the apex of a right angle made by the series of papers +and the median plane of the subject's body; whereas in the case of the +even number of papers the subject stood opposite the space between the +two middle sheets, thus making the position of the sheets less +favorable. + +In the preceding tests the distance between the centers of the +neighboring sheets was always 50 centimeters, so that the angle through +which the median plane of the experimenter's body would have to turn in +order to pass from one sheet to the next, was about 3-3/4 degrees. In +the following tests these distances were gradually decreased. The +sheets, always five in number, were replaced by ever narrower white +strips of paper mounted on dark cardboard and illumined by a Nernst +lamp. The following table shows the decrease in correct inferences +running parallel with the decrease of the angle through which the +subject would have to turn in order to be in line with the several +pieces of a series successively. The percentage in each case is based +upon at least 100 tests. + + Angle: 3-3/4° 3° 2-1/2° 2° 1-1/2° 1° + Distance between the + centres of two neighboring + papers: 50cm. 39cm. 33cm. 26cm. 20cm. 13cm. + No. of correct inferences: 77% 73% 71% 68% 66% 61% + +A curious and unexpected change was here noted in the subject, Mr. +Koffka, who, while concentrating his attention to the uttermost, began +unawares to develop a new system of expressive movements of the head. +When the distance between the sheets was relatively great, he had been +in the habit of turning his head and eyes in the direction of the sheet +intended, and as the distances became less he had reacted only by a +turning of the eyes. But now, as the distances were still further +decreased, he began again to react by means of head movements, and these +were of exaggerated magnitude, for which he would compensate, as it +were, by an eye-movement in the opposite direction. Although the head +movements decreased in scope as the distances between the sheets were +steadily decreased, they still were always decidedly greater than the +eye movements, which I was now normally led to expect and which could be +judged without much difficulty. This form of reaction was much more +satisfactory as a cue, and therefore it came to pass that, whereas in +the preceding series I had made only 60% correct inferences when the +angle was 1 degree, I now found that--the angle remaining the same--80% +of my inferences were correct. (My final judgment I continued to base, +as before, upon the position, and not upon the movement, of head and +eye). The number of correct inferences continued relatively high, even +after the distance between the papers was decreased tenfold,--as will be +seen from the following table: + + Angle: 1° 30' 15' 9' 7' 6' 5' 3' 2' + Distance between the + centres of two neighboring + papers: 131 65 33 20 15 13 11 6-1/2 4mm. + Percentage of correct + inferences: 80 79 78 81 84 80 77 68 68% + +Beginning with an angle of 1' (distance between the centers of two +neighboring papers = 2 mm.), the subject was unable to focus, with +sufficient steadiness of vision, upon one paper alone, and the +movements, for that reason, ceased to manifest themselves. Comparing the +results obtained in the case of this subject with those obtained from +two others, whose reactions had remained normal, B. and Miss St., we +find that with them there were only 53% correct inferences in both cases +(based each upon 200 tests), when the angle was 5'. In my errors, too, I +often shot wider of the mark. In another series of 200 tests, in which +Miss St. "merely thought of the places", I had a percentage of 56% +correct inferences, and my errors did not become any coarser. Miss St. +believed this a case of true telepathy, but I had been guided in my +judgments entirely by her unwittingly made movements--or rather the +direction--of her eyes. The magnitude of these movements bore a constant +relationship to the distance between papers as it was conceived by the +subject. + +Reviewing the experiments discussed in this chapter, we find that the +same kind of movements and postures, which had been noted in persons +experimenting with the horse, tended to recur in the laboratory, in so +far as the mental attitude of the subjects, given in their introspective +accounts, corresponded with that of the questioners of the horse. + + + + +CHAPTER V + +EXPLANATION OF THE OBSERVATIONS + + +The author having described the observations made upon the horse, and +having discussed the activities of the questioner upon the basis of +observations made objectively and upon his own introspections, and +having verified the results thus obtained, by means of laboratory +tests,--we are now in a position to solve satisfactorily all the +problems which this interesting case has presented. + +That which is least difficult to understand is the horse's seeming +knowledge of language and particularly his ability to answer questions, +no matter by whom, or in what dialect, they were put. As a matter of +fact, it made no difference who desired an answer, for the only person +upon whom the experiment depended was the questioner, that is, the one +who asked the horse to tap. We have everywhere designated this person as +the experimenter or questioner. It was he who gave the directions, and +since all that were involved were visual signs, the drama in which Hans +appeared as the hero, was nothing but a pantomime. All speech was +superfluous and, except in so far as the tone of voice in which it was +spoken was soothing or reprimanding, it was quite unintelligible to the +horse. + +From the foregoing, the reader understands without further explanation +Hans's ability to count and to make computations. If the number of taps +had depended solely upon the length of time and the angle at which the +questioner bent forward, the horse would have been able to tap any +number desired. Since, however, only the right foot was employed, the +left one being used at most for making a final tap, the number of taps +had an upper limit which was due to the fatigue of the animal. This +limit was about 100. That it was possible to ask such questions as: "How +many times is 100,000 contained in 654321?", and thus to give problems +involving millions, is perfectly clear. + +All wonderful feats of counting and computation which were accomplished +while thus experimenting with the horse are to be accredited, not to the +horse, but to the questioner. If such is the case, they certainly cannot +be considered astonishing. Thus, when to the question, "How many of the +gentlemen present are wearing straw hats?" the horse answers correctly +in accordance with the wording of the question and omits the straw hat +of a lady, then Mr. von Osten is the guide. It is no wonder that Hans +never showed the slightest excitement when confronted with difficult +problems, nor that it apparently took no time whatever to solve them. + +Hans, however, was also a faithful mirror of all the errors of the +questioner. Aside from mistakes due to occasional interruptions on the +part of visitors, these errors had two sources: faulty computation and +inadequate concentration--i. e., aside from arithmetical errors on the +part of the questioner, were his premature or belated movements. Since +both of these factors might be operative, the following three +possibilities arise. + +(_a_) The questioner computes correctly but does not move at the proper +moment. Nearly all the errors which had been accredited to the horse, +were of this kind. + +A part of these errors had the appearance of being significant, that +is, they might be interpreted as a misapprehension of the question. If, +for instance, instead of a sum only one of the quantities was given, or, +if instead of a product only one of the factors was given, it might be +interpreted that the horse simply wished to repeat the problem. Thus, +Mr. von Osten in response to the question: "How much is 3 times 5?", +twice in succession received the answer, "3", and upon my question, "How +much is 3 plus 4?" he answered, "3", and to "How much is 2 times 6?" he +tapped 6, and to "What is one-fourth of 36?" 4. In part (certainly in +the second and third example cited) an individual quantity or factor had +been emphasized in the consciousness of the questioner (cf. page 105) +and in part the reactions were due to chance. Thus, when Mr. Hahn asked +the question: "What is one-half of 10?", he received the following +responses: 2 and 10, and then 17 and 3. To this class belong also, the +tests made by the Commission of September and reported in Supplement +III. (See page 255). + +Other errors, even though they may not have appeared to be significant, +might yet have been characterized as mistakes due to speed; as when, e. +g., Hans made an error of one unit--and sometimes, though less +frequently, of two units--too much or too little in his response. One +might be led to believe that Hans had not made an error of calculation +but merely of counting in the process of giving his result, which always +had to be done by the cumbersome method of tapping. As a matter of fact, +the trouble lay in the wrong degree of concentration on the part of the +questioner: In errors of +1, tension was too slight, in those of -1, it +was too great (see page 91). This comes out clearly in a comparison of +the two more extensive series which I took in the case of Mr. +Schillings. During the first series, he was well disposed, and was able +to concentrate effectively, while during the second, he was nervous and +easily diverted. This difference in intensity of concentration in the +case of the two series is attested, not only subjectively by Mr. +Schillings's introspective statement, but may be measured objectively by +means of the number of final taps which the horse gave with his left +foot during these two series. We saw (page 94) that these final taps +were always a sign of intense concentration and, as a matter of fact, +one-half of the horse's responses to Mr. Schillings during the first +series were made in this way; whereas, in the second series, only +one-third were of this sort. (I, myself, was never able to get, without +conscious control, a greater number of this type of response.) We may +therefore say that, in the first series we had a high degree of tension, +or concentration, whereas, in the second series, we had a low degree. +The errors distribute themselves over the two series as follows: + + +1 +2 -1 -2 + Series I (31 tests) + Correct responses: 87% + Incorrect " : 0% 0% 13% 0% + Series II (40 tests) + Correct responses: 40%. + Incorrect " : 40% 8% 2.5% 0% (and 9.5% + other kinds of errors.) + +We find in Series I no "+1" errors, but only "-1" errors; in series II, +on the other hand, the errors are almost exclusively of the "+1" +category, equaling the number of correct responses, and there is only +one "-1" error. A series obtained in the case of Mr. von Osten is almost +as satisfactory an illustration. When he first began to take part in +tests in which the procedure was the one we characterized as "without +knowledge" and had to note their complete failure, he was thrown into +such confusion that the responses in the case of procedure with +knowledge were also incorrect. The errors there were always +1, (whereas +those in the case of procedure with knowledge, which were due to quite +different causes, were very great and inconstant.) The number of +1 +errors obtained on this occasion comprises one-fourth of all the plus +errors which were ever obtained in the case of Mr. von Osten during the +entire course of these experiments. Finally, I would mention two +examples of my own. In the course of my very first attempts with Hans I +obtained, as I said on page 89, three responses in a total of five which +exceeded the correct result by 1. This I would explain by the fact that +although I employed a high degree of concentration, I nevertheless was +somewhat skeptical. The result was a certain deficiency in the degree of +concentration. A second example which I would cite is taken from the +period in which I had already discovered the cue to Hans's reactions and +goes to show that I was then still able to eliminate the influence of +this knowledge and to work ingenuously. To the question, "How much is 9 +less 1?" I, momentarily indisposed, received the answer 10, and then six +times in succession the answer "9", and finally the correct response, +"8". + +Errors of another kind--the not infrequent offenses against the very +elements of counting and the fundamental arithmetical processes--were +regarded in part as intentional jokes and by an authority in pedagogy as +a "sign of independence and stubbornness which might also be called +humor". Hans emphatically asserted that 2+2 was 3 or he would answer +questions given in immediate succession as follows: "How many eyes have +you?"--2. "How many ears?"--2. "How many tails?"--2. These errors, as a +matter of fact, evince neither wit nor humor, but prove incontrovertibly +that Hans had not even mastered the fundamentals. + +Many of the errors baffle every charitable attempt at interpretation. +These gave the horse the reputation of capriciousness and unreliability. +If Hans designated the tone "e" as the seventeenth, or "g" as the +eleventh, or when he called Friday the 35th day of the week or believed +50 pfennige to be worth only 48, the cause for these responses lay +either in the insufficient degree of tension on the part of the +questioner (as in the first three examples) or in the extravagant +expenditure of the same (as in the last case). If, therefore, the horse +at times would "hopelessly flounder" which would seem to be indicated by +tapping now with the right and now with the left foot, then as a matter +of fact, this form of reaction came about as was described on page 61, +with this difference that there we had to do with voluntary controlled +movements on the part of the questioner, whereas here, they are the +result of an unsuitable degree of tension which expressed itself in +frequent and disconcerting jerks. Besides the answer 3, this so-called +floundering was the only reaction the average person could obtain from +the horse in the absence of Mr. von Osten and Mr. Schillings. It would +however occur also in the case of these gentlemen and would be received +by them with resentment when in truth it was Hans's greatest feat, for +he showed his extremely keen reaction upon every movement of the +questioner. To this group belong also the errors in the case of higher +numbers, the sole cause of which lay in the difficulty with which +tension could be maintained and the body kept motionless for so long a +period. These errors occurred in accordance with a certain law. If, for +instance, a certain test repeatedly evoked incorrect responses, the +questioner would gradually increase the duration of tension and would +thus come a little nearer to the desired goal with every test. In this +way, Mr. von Osten desiring 30 as an answer obtained consecutively the +responses, 25, 28, 30; and I, myself, for the answer 20, received +consecutively the responses 10, 18, 20 (see also the laboratory tests, +page 105). Sometimes too, the questioner would flag in his efforts +before the goal was reached. Thus in one of my first tests, I received +for the answer 11 the following responses: 1, 4, 5, 7, 4. I was unable +to get beyond 7. In other instances, the horse responded first with too +few and then with too many taps. The correct response therefore could +only be obtained after an appreciable amount of gauging of tension, as +in target practice there must be a gauging of distance. (See page 92). +In this way Mr. von Osten obtained for 10 the responses 8, 8, 11, 10, +and Mr. Schillings for 17, received 9, 16, 19, 18, 18, 14, 9, 9, and +finally, after some efforts, 17 taps. Thus there was a rise from 9 to +19, then a fall back to 9 and after eight tests the correct response. As +long as we attempt to explain this fact as error on the part of the +horse, so long will it remain inexplicable, but the moment we regard it +from the point of view of the psychology of the tension of expectation, +it becomes perfectly plain. + +The same holds true for the curious predilection which Hans appeared to +have for the numbers from 2 to 4, especially for 3 (see page 68). As a +matter of fact the cause of this lies in nothing other than the +inadequate concentration of attention on the part of the questioner and +less often in an extravagant expenditure of concentration, which +explodes immediately after the first tap on the part of Hans (as in the +case of my first tests); but usually the cause lay in a complete lack of +concentration, though the same result may be produced by various causes. +It is usually after 2 to 4 taps of the horse's foot that the questioner, +who does not concentrate, makes his first move which naturally puts an +end to the tapping on the part of the horse. As a rule this jerk follows +immediately upon the second tap. (On the other hand, relaxation of +attention is very difficult upon the first tap. See page 95). The +questioner, however, would expect further tapping and therefore would +not bring his body back to a completely erect position and the result +would be a 3, the last unit of which would be given by the final tap +with the left foot. Here we also obtained light as to the answers which +Hans gave in those tests in which the method was that of "procedure +without knowledge". These responses had nothing to do with the problem, +for neither the horse nor any one else knew the solution. But in the +horse's responses the degree of tension of the questioner's +concentration was faithfully mirrored. An experimenter who was as +skillful in concentrating as Mr. von Osten, obtained--almost without +exception--very high numbers, whereas one whose concentration was slight +would receive in response to nearly all questions the answers 2, 3 or 4. +Thus, the Count zu Castell received in response to seventeen questions +the answer 2, three times, the answer 3, six times, and the answer 4, +four times, two answers being accidentally correct. + +Another group of errors was characterized as stubbornness on the part of +Hans, such as his persistence in repeating an incorrect response, or his +repetition of a former correct answer in response to later questions +where it was perfectly senseless. During a demonstration before a large +number of persons, I held a slate with the number 13 upon it within the +horse's view and also within view of the spectators. I, myself, did not +know what number was written on the slate. Having been asked to tap the +number, Hans responded by tapping 5. The grand-stand shouted "Wrong!" I +asked Hans to try again. Four times in succession he answered 5. At +another time Mr. von Osten and I each whispered a number (7 and 1, +respectively,) into the horse's ear and asked him to add the two. Three +times in succession he tapped 11. After the test had been repeated in +accordance with "procedure with knowledge" and a correct response had +been received, we tried once more a test of "procedure without +knowledge". Again, he responded with an 11. On a third occasion, I asked +Hans to tap 5. He responded with a 4 and then, correctly, with a 5. +Thereupon, I asked him to tap 6. Again, he responded with a 4. Then I +asked him to tap 7. Once more he responded with a 4, and only when I +proceeded to count aloud did he tap 7 correctly. I had him repeat the 7 +and then went over to 9. Promptly he responded with another 7. In these +cases, which by-the-way were not very frequent, we have to do, not with +stubbornness on the part of Hans, but with the persistence of that +number in the consciousness of the questioner. Modern psychology has +recognized this tendency of ideas, which have once been in +consciousness, to reappear on other occasions even though they are +wholly inappropriate. It has been termed "perseverative tendency." +(Perseverationstendenz).[21] + +While the errors thus far discussed appeared sporadically in long series +of correct responses, there still might be observed at times a massing +of errors, usually at the beginning of a day of experimentation or at +the beginning of a new series. We were regularly told that Hans always +had to have time to adjust himself to new circumstances. The records +often showed comments such as these: "After a number of practice tests +the horse appears particularly well disposed", or "Hans, at first +inattentive, does not respond. Suddenly he gets the hang of things". +Different questioners who worked with the horse required different +lengths of time to obtain proper responses. Some needed a quarter of an +hour, others scarcely half a minute. I, myself, found that in the degree +in which I learned to control my attention, in that degree did this +phenomenon tend to disappear, but would reappear the moment I became +indisposed. From this we see that, instead of attributing all sorts of +mental characteristics, such as stubbornness, etc., to the horse, we +should lay them to the account of the questioner. As a matter of fact we +find that this "getting into the sweep of things", i. e. the overcoming +of psycho-physical inertia, has long been known in the case of man and +has been experimentally determined and called "Anregung" (excitation) by +the psychiatrist, Kraepelin,[22] and his pupil, Amberg.[23] A massing of +errors toward the end of a long series occurred only when the questioner +was fatigued. There was nothing which had to be interpreted as fatigue +or as indisposition on the part of the horse, (except in the few cases +of very large numbers, cf. page 67). To be sure, Mr. von Osten always +offered these two excuses. That they were without warrant is shown by +the fact that Hans, after appearing indisposed or fatigued while working +with one questioner, would nevertheless react promptly and correctly a +moment later for some other experimenter, and furthermore, when working +with me, the number of his correct responses would rise or fall with my +own mental disposition. + +Finally, I would here note a rather interesting observation for which I +am indebted to Mr. Schillings and the Count zu Castell. They had +noticed, independently of each other, that the horse would often fail to +react when for any length of time he was given problems dealing with +abstract numbers, even though they were of the simplest kind; but that +he would immediately improve whenever the questions had to do with +concrete objects. They believed that Hans found applied mathematics more +interesting, and that abstract problems, or those which were altogether +too elementary, bored him. The Count zu Castell furthermore noticed that +the responses tended to be more correct as soon as he had the horse +count objects which he, himself, (Castell) could see during the test. +Quite in accord with this is the statement to be found in the report of +the September-Commission, in which we find this note in a discussion of +the arithmetical problems (not involving visible objects), which the +gentlemen already mentioned had given the horse. "The horse responded +with less and less attentiveness and appeared to play with the +questioner." Here again, that was looked for in the animal which should +have been sought in the man. Mr. Schillings was capable of intense, but +not continued concentration and it was he who was bored, and not the +horse. And it was the Count zu Castell and not the horse that found it +necessary to invoke the aid of perceptual objects to bring his +attention to the proper height of concentration. + +The reader will see that thus far I have supposed the horse to be a +never-failing mechanism and that I have placed all errors to the account +of the questioner. The horse never failed to note the signal for +stopping and therefore never was the immediate cause of an error. It is +not to be denied that now and then he would cease tapping spontaneously +and in this way would become the cause of an error. We have no data on +this point, but undoubtedly the horse's share in the total number of +errors was very slight. + +(_b._) Another source of error was faulty computation on the part of the +questioner. The questioner made the signal for stopping when the +expected number of taps had been reached. The horse faithfully mirrored +the miscalculation of the questioner. I have knowledge of only one such +case. The journals report that once Mr. von Osten, when someone called +to his attention that Hans had indicated the wrong day of the week, +replied: "Yes, you are right, it was not Thursday, but Friday," +whereupon Hans being asked again, promptly responded correctly. This +appeared to the reporter in question as proof of the subjective +influence of Mr. von Osten upon the horse. + +(_c._) When errors in calculation and failures in proper concentration +combine, i. e. when the questioner makes a mistake in calculation +because he is excited or inattentive and for the same reason does not +make the movement, which is the signal for stopping, in accordance with +the number which he deems to be the correct answer, then the result is +usually wrong, but it may be correct in the few cases in which the two +errors exactly compensate each other. Nothing has been so effective in +establishing Hans's reputation, nothing has brought him so many +followers, as these cases in which he, rather than his mentor, has been +in the right. Compared with the mass of cases in which Hans was wrong +these latter cases are diminishingly few in number, yet these few made +such an impression upon the observers that their number tended to be +overestimated. As a matter of fact, I have been able to discover records +of only seven such cases. Two of these were reported by the Count zu +Castell. On the 8th of September, he entered the horse's stall, alone, +and believing it to be the seventh day of the month, he asked Hans the +date. The horse responded correctly with 8 taps. At another time he held +up before Hans a slate on which were written the numbers 5, 8 and 3 and +asked the horse to indicate their sum which in the momentary excitement, +vaguely appeared to Castell to be 10. To his chagrin he noticed that +Hans continued to tap. Thereupon he intentionally remained motionless +until the horse had stopped tapping spontaneously--as he thought--at 16. +(The newspapers reported that the numbers to be added had been 5, 3, and +2; that the questioner had expected the answer 11, but that Hans had in +three tests always ceased tapping at 10.) In both cases the questioner +regarded the answers of the horse as wrong and recognized his mistake +when his attention was called to it. I, myself, had the same experience. +One time I received in response to the question, "What day of the week +is Monday?", the answer 2, although I had expected the answer 1; at +another time I asked, "How much is 16 less 9?", and the horse responded +with 7 taps, although I had erroneously expected 5. I noticed my mistake +only when my attention was called to it by one of those present. Another +example is related by Mr. Schillings. A row of colored cloths lay +before Hans. Beside them stood an army officer. Pointing to the latter's +red coat Mr. Schillings asked the horse to indicate, by means of +tapping, the place in the row where a piece of the same color lay. Hans +tapped eight times, but Mr. Schillings reprimanded him because the red +piece was, as a matter of fact, second in the row. Upon a repetition of +the test, Hans again tapped 8. (By some, the facts are recounted as +having been the other way round; viz.: Hans tapped 2 instead of 8. This +of course would call for a different explanation.) It was noticed that +at the place which would be indicated by eight taps there was not a red +piece but a carmine colored piece of cloth. A newspaper reports, +somewhat vaguely, a sixth case as follows: Hans was asked to spell the +name "Dönhoff" and began correctly: "Dö". Mr. von Osten, who somehow +began to think of another name, "Dohna", interrupted him and wished to +correct him by suggesting o instead of ö (i. e., 2 taps instead of 3). +Hans, however, continued to spell the entire word with the greatest +equanimity. He had not erred. A similar experience is reported by Mr. H. +von Tepper-Laski, the well known hippologist. Although the details have +slipped from his memory, he reports that in the case in question the +correct answer was thrice refused by the questioner who thought that the +horse's answer was incorrect. Hans, upon being severely reprimanded in a +loud and harsh tone of voice, turned about as if disgusted with the +injustice of the man and made straight for his stall.--It is clear that +in the cases described we are not dealing with accidentally correct +responses, for in nearly every case the test was repeated a number of +times and the same responses were received each time. As a matter of +fact, my own introspection convinced me that the third and fourth cases +were surely, and the first and sixth were very probably, due to +insufficient concentration on the part of the questioner. Accordingly +there is everywhere in these cases a difference of +1 or +2 between the +number thought of and the number tapped (see page 92 f.). The data in +the second and fifth and still more in the seventh case were too meager +to warrant an attempt at explanation, for it is not even known whether +Hans responded with more or fewer taps than was expected by the +questioner. It is unfortunate that a more complete record was not made. + +The frequent and intentional attempts of Mr. von Osten to induce the +horse to give an incorrect response,--which, by-the-way, were regularly +unsuccessful--belong only apparently to this group. Thus he asked, e. +g., "2 times 2 is 5, is it not?" "3 times 3 is 8?", etc., but Hans +refused to be misled, and responded correctly. This was from the very +beginning one of the main arguments for independent thinking on the part +of the horse. The actual procedure was as follows, even though the +questioner had said "2 times 2 is 5", there still was present in his +consciousness the number 4. I, myself, would think either of the first +member of the equation, i. e., 2 times 2, in which case Hans would +respond with 4 taps or I would have in mind the second member, i. e., 5, +in which case he would respond with 5 taps. Never did I succeed in +thinking of both at the same time. The association between the thought +"2 times 2" and the concept "4" is so close and supported by so many +other associations that the attempt to form a new one, that is at +complete variance with all these, is futile. One may say "2 times 2 +equals 5" but it is impossible to conceive it. + +Let us turn now, from the tests in counting and computation to those in +reading. We have seen that Hans manifested his seeming knowledge of +language symbols in a threefold manner: he might approach a slate on +which was written the symbol asked for, or he would indicate its +location in a series of slates by means of tapping, or finally by means +of so-called spelling of the word which was written upon a slate or +placard. The responses by means of approaching a placard were very often +unsuccessful, while indications by means of tapping were scarcely ever +unsuccessful. If it were true that higher intellectual processes[T] were +here involved, then the converse would have been expected, for tapping +required not only the ability to read, but also the ability to count. +If, on the other hand, we assume that the horse simply followed the +directions given by the questioner's movements, this seeming difficulty +resolves itself, for it would be more difficult for Hans to perceive the +signs which he receives while moving than those which he receives while +tapping. When we recall that it was easier to direct the horse to a +placard near the end of a row than one nearer the center (see page 81), +we can readily understand how it was that during the experimentation +carried on by the September-Commission (Supplement III; page 255), Hans +was able to point out immediately the placards on which were written the +names "Castell" and "Stumpf", for they were at the two extreme ends, but +was unsuccessful in locating the one on which was written the name +"Miessner" which was not a bit more difficult to read, but was located +at the fourth place in the row. He first approached the fifth card, then +upon repetition of the test he pointed out the other neighboring tablet, +viz., the third. + + [Footnote T: Professor Shaler[24], a well-known American savant, + mentions a three-year old pig belonging to a Virginian farmer, that + was able to read and had some understanding of language. From + numerals which were written upon cards and spread out before it, + this pig could compose dates. It could also select from among + certain cards one upon which was written a given name, asked for by + the master. Supposedly no signs of any kind were given. (Shaler + thought to exclude effectively the sense of smell, which is so + highly developed in the pig, in that he, Shaler, himself smelled at + the cards, since he also "possessed an acute olfactory sense!") + Since we are told that the farmer in question made a business of + supplying trained pigs for exhibition purposes, the case appears + suspicious. We hear of a pig exhibited in London, that was able to + read and spell, and could also tell the time by the watch[25]. We + cannot tell, however, whether the two pigs, which beyond a doubt + were mechanically trained to respond to signals, are identical or + not.] + +In spelling, Hans was quite indifferent whether his table with the +eighty-four number signs upon it stood before him, for he had no +knowledge of letters. Neither Mr. von Osten nor Mr. Schillings required +it, for the former knew the table by heart and Mr. Schillings told me +that before every test he made a note of the numbers which were +necessary to indicate the required letters, trusting in this way to +control the responses of the horse and never guessing that by so doing +he was making it possible for the horse to answer correctly. The +newspaper reports aroused much interest at the time by stating that Hans +was able to spell such proper names as "Plüskow" and "Bethmann-Hollweg", +even to putting in the difficult "w" and "th". The friends of Mr. von +Osten at the same time called attention to the exquisite auditory +acuteness of the horse which enabled him to perceive the aspirated "w" +and to discriminate between the "th" and "t", (the "th" is softer than +the "t" in German.--_Translator_). This explanation, of course, must +have appeared somewhat daring even at that time. + +Hans was quite guiltless of the many limitations imputed to him +concerning his knowledge of symbols. That he was unable to read capitals +or Latin script was merely a vagary of the master, like the belief that +it was necessary to confine one's self in one's questions to a certain +vocabulary and to a certain form. Mr. von Osten's apparent failure to +elicit responses from the horse on topics of which it was ignorant is a +beautiful illustration of the power of imagination. Mr. von Osten was +convinced from the very first that Hans could not answer such questions. +When the belief in success was lacking, of course there was not the +requisite amount of concentration which, alone, leads to perceptible +expressive movements and thus elicits a successful reaction on the part +of the horse. + +Mr. Schillings, owing to his great impressionability, remained long +under the spell of Mr. von Osten's point of view. Thus I find in the +record of the September-Commission that the question "How much is 3 plus +2?" was answered incorrectly by Hans, but he responded correctly the +moment Mr. Schillings replaced the word "plus" which was "tabooed", by +the word "and". For a long time also he could receive no response to +questions put in French until one day he made the discovery that, +curiously enough, the animal never responded adequately unless he +himself firmly believed in the possibility of success. It is noteworthy +that the Count zu Castell, independently of Mr. Schillings, made the +same discovery. Mr. Schillings made his curious discovery--which he was +unable to interpret, but which aroused some suspicion--on the following +occasion. One day--whether accidentally or because his prejudice was +temporarily overcome--he commanded; "Dis deux!". Hans responded promptly +with 2 taps. He was greatly surprised and believed that Hans had gotten +hold of the French by hearing it spoken in his environment. Possibly he +understood also "trois" and "quatre"? He put the questions and received +correct responses. He asked again, "dix", "vingt", and so on to +"soixante". At "soixante-six" he became doubtful. Indeed, Hans failed +him. At "quatre-vingt", the game began again. "Cent", again, succeeded. +The old saying that "Faith will move mountains" was verified once +more.[U] + + [Footnote U: It has been scientifically proven that a number of + supposed mystical phenomena, table-moving, table-rapping, and + divination by means of the rod, all are the result of involuntary + movements made unawares by those concerned, just as in the case of + this work with Hans. (We must of course except those not infrequent + instances in which the phenomena in question are purposely and + fraudulently simulated.) There is this difference, however, that + there the thing affected is a lifeless object,--the table or the + rod,--here it is a living organism, the horse; hence there the + immediate effect of the movement is physical work in the form of + energy expended in moving the table, here the movement becomes a + visual stimulus. A number of observations which I find in the + relevant literature, and which I shall introduce into this chapter, + may serve to show how close is the similarity between the two cases, + how much depends upon the questioner, and how little really upon the + instrument--whether table or horse--which is acted upon. + + Two examples will suffice to illustrate the significance of belief + and of the concentrated attention that results from it. The first is + taken from the letters of Father P. Lebrun on the divining rod[26], + which appeared in 1696. An old woman once told a treasure-seeker + that she had always heard that a treasure was buried at a certain + place in the fields. The man, who was known as an expert in the art + of using the divining rod, immediately set out to locate the gold. + Lo, and behold, the moment he set foot on the spot described by the + old woman, the branch turns downward, and from its movements the man + gathers that twelve feet below ground there lies buried some copper, + silver and gold. He calls a peasant to dig a pit eleven feet deep, + then he sends him away so that no other should get into the secret. + He himself digs a foot deeper, but all in vain, for he finds + nothing. Standing in the pit, he again takes up the branch. Again it + moves, but this time it points upward, as if to indicate that the + treasure had disappeared from the earth. Dismayed, he climbs out of + the pit and questions the branch a third time. This time it points + downward once more. He climbs back into the pit. Presently he feels + the prick of conscience (for in the 17th century many regarded the + dipping of the divining rod as the work of the Devil). Terrified, he + exclaims: "O God, if the thing I am doing here is wrong, then I + renounce the Evil One and his rod (s'il y a du mal, je renonce au + démon et à la baguette)". Having spoken, he once more takes the rod + in hand to test it. It does not move. Horrified, for now there was + no longer any doubt that Satan was the cause of its movements, the + man makes the sign of the cross and runs away. But he had hardly + gone more than two or three hundred paces when the thought strikes + him: Is it really true that the branch will no longer move for him? + He throws a coin to the ground, cuts a branch from a bush nearby, + and is overjoyed when he notes how it dips down toward the money. + + Another example is to be found in a report of the well-known + physicist, Ritter[27], of Munich, which appeared during the early + part of the 19th century. Ritter, a man with a bent for natural + philosophy and metaphysics, describes an instrument which was to + replace the divining rod, and which he called "balancier." It was + simple enough, consisting of a metal strip that was balanced + horizontally upon a pivot, and was supposed to be put into motion in + the presence of metals. Ritter used this instrument in his numerous + experiments with the Italian Campetti, a man who had achieved a + measure of fame in Europe for his ability to discover springs and + metals by the use of the divining rod. Carrying the "balancier" on + the tip of the middle finger of his left hand, Campetti--whose + integrity one cannot cavil at--had to touch repeatedly a plate of + zinc or pewter, and had to count aloud the number of touches he + made. The following curious law was found to obtain (that was + probably suggested to the subject by Ritter without his being aware + of it): with the first contact the "balancier" turns to the left, + with the second to the right, and with the third it remains at rest. + At 4 it turns once more to the left, at 5 to the right, at 6 it + remains at rest, etc. It remained immovable only at the so-called + trigonal numbers (3, 6, 9, 15, 21, etc.). Ritter tells us that when + Campetti did not really count or did not think of the number, then + it would not have any influence whatever upon the action of the + instrument. This Ritter ascribes to the agency of electricity (which + in the 18th and 19th centuries was made to play very much the same + rôle that Satan had played in the 16th and 17th centuries). + + The similarity of these two cases and that of Mr. Schillings is + evident. When the questioner of the horse and the bearers of the + "balancier" and of the divining rod are confident of success, they + succeed. When they do not expect success, they fail.] + +Hans's seeming knowledge of the value of coins and cards, of the +calendar and the time of day, as well as his ability to recognize +persons or their photographs, can now be readily understood. In all of +these cases, we had to deal, in so far as knowledge is concerned, only +with that of the questioner,--the horse simply tapped the number the +questioner had in mind. The meaning which was supposed to be expressed +by the tapping never existed as far as Hans was concerned; it was only +in the mind of the questioner that the concepts: ace, gold, Sunday, +January, were associated with "1", etc. The same was true with regard to +all other wonderful feats of memory. The sentence: "Brücke und Weg sind +vom Feinde besetzt", (The road and the bridge are held by the enemy), +which was given to the horse one day and correctly repeated by him on +the following day, was not an answer elicited from the horse by means of +a question, but rather a system of automatic reactions which were +induced by certain involuntary movements of the questioner as stimuli. +Far from showing a wonderful memory in these feats--as is claimed for +him by the very non-critical compiler, Zell[28]--Hans, on the contrary, +has at his service a remarkably small number of associations. For, +besides possessing the powers of any ordinary horse, he recognizes only +a few meager visual signs. To be sure, we find in the literature a horse +that was said to have recognized 1500 signals,[29] but all proof is +lacking and the report is so meager that we cannot discover whether +these signs were auditory or visual.[V] + + [Footnote V: The French investigators Vaschide and Rousseau make a + reference to this case, and mistakenly state the number of signals + as 1500 instead of 115[30]. Ettlinger[31] takes over this wrong + figure and makes the additional mistake of assuming that the + reference is to an original investigation made by the two + Frenchmen.] + +Having thus disposed of all questions concerning the horse's apparent +feats of reason and memory, let us turn to those in the field of +sensation. We shall begin with vision. That Hans was unable to select +colored pieces of cloth merely upon the basis of color quality, without +reference to their order, was shown in Chapter II. It would, however, be +somewhat hasty to infer color-blindness from this fact, as did +Romanes[32] on the basis of similar unsucessful responses on the part of +a chimpanzee ("Sally" of the London Zoölogical Garden). It is much +easier to explain the failure of the horse than that of the monkey on +the basis of intellectual poverty, a poverty of associative activity. It +presumably can discriminate between the various colors, but it cannot +associate with these their names. The existence of chromatic vision in +the lower forms is by no means as unquestionable as is assumed by +popular thought. Even teleological considerations which are often +brought forward (especially that of the ornamental and protective +coloring of so many animals) can never do more than establish a certain +probability. For definite proof, we need data given by observation (we +have none in this case), or experimental evidence. Such evidence we +have, but it is insufficient in quantity and unfortunately most of it +was obtained under inadequate experimental conditions.[W] We know +nothing regarding chromatic vision in the horse, though we have often +had trained horses which apparently possessed color discrimination. The +earliest report of this kind I find in a work published in the year +1573.[36] Here we read that a number of Germans exhibited two horses in +Rome which could, upon request of their masters, point out those persons +among the spectators who were wearing stockings of any designated color. +The passage, "conoscevano i colori", (they recognized the colors,) +proves nothing and no one has ever heard, even in modern times, of a +horse that actually knew colors. + + [Footnote W: All told, there are hardly more than half dozen + experimental investigations of the color-sense in mammals,--to speak + only of these. Three of them deserve especial mention. One, the work + of the American, Kinnaman,[33] on two Rhesus monkeys. Then a brief + but careful piece of work by Himstedt and Nagel.[34] These two + investigators were able to determine that their trained poodle could + distinguish red of any tone or shade from the other colors, and from + Professor Nagel I learned that later the tests were extended and the + same was shown to be true concerning the blue and the green. And + finally there is an investigation which hitherto has been known only + from a reference which Professor Dahl,[35] the investigator, himself + makes. The work is on a monkey, Cercopithecus (Chlorocebus) + griseoviridis Desm. (Professor Dahl has kindly allowed me to look + over the records of the experiments. He intends to publish the + monograph at an early date.) + + All of these investigators arrive at the conclusion that the animals + tested by them possess color-sense. The monkey last-mentioned shows + one peculiarity: it was unable to distinguish a saturated blue from + the black. It will require further tests to clear this up.] + +Nor did Hans possess anything like that high degree of visual acuity +which had been attributed to him. He was supposed to be able to read +easily at a distance small, almost illegible script, which we ourselves +could decipher only with the greatest difficulty close at hand. It was +also supposed that he could distinguish ten-and fifty-pfennig pieces +whose faces had become worn beyond recognition for us. None of these +accomplishments have stood the test. We have no reason to believe that +Hans can see the objects about him more clearly than other horses, +regarding whom one usually assumes that they receive only vague visual +impressions. Horses do not as a rule seem to be near-sighted as is often +asserted by the layman, but rather somewhat far-sighted, or if we may +believe Riegel,[37] who tested some six hundred horses, they probably +have normal vision. But we are told that many horses--and according to +some authors all--have an innate imperfection which detracts +considerably from the clarity of vision. This imperfection consists in +an irregular formation of the sclerotic coat and of the lens of the +eye.[38] The two organs do not have the same refraction in all parts. As +a result, objective points are not imaged as points upon the retina. +(Hence the name: astigmatism, i. e., "without points", for this +disorder.) The retinal image of the object is not only vague, but also +distorted.[X] + + [Footnote X: There is no justification for the wide-spread belief + that the horse which on account of the greater size of his eye (more + correctly, on account of the greater focal distance) receives larger + retinal images of objects than does the human eye, for that reason + also sees objects, larger than we do. Horses' shying is often + explained in this way. But the conclusion just mentioned is + erroneous. The retinal image is not the perceptual image. It + undergoes many transformations within the nervous system itself.] + +Many will doubt whether with such imperfect images an animal can react +to directives so minute, as we have asserted to be true in the case of +Hans. In considering this question we must distinguish between the +directives for pointing out colors and the directives for tapping and +for head movements on the part of the horse. In pointing out and +bringing forth pieces of colored cloth there is involved the perception +of an object at rest, viz.: the direction of the questioner who is +standing quietly; whereas in the case of responses by means of tapping +the stimulus is the horse's perception of the questioner's movements. +Now, the construction of the horse's eye, as described above, is not +favorable for the perception of objects (so-called acuity of vision). +This may partly account for the slight success of the horse in those +tests in which he was required to select a piece of cloth of a +designated color, in so far as these commands were not accompanied by +calls or exhortations. Where human observers averaged eighty per cent +correct responses (page 135), Hans, under similar conditions was +successful in only one-third of the tests. In his errors he was also +wider of the mark than were the human observers (page 82). The object +perceived, to be sure, is a large one, viz.: the questioner, and he at +close range. We must therefore consider more specifically what are the +determining factors that make for success or failure of the response. +First of all, the innocent questioner very often did not designate the +direction with sufficient clearness. Furthermore, Hans presumably was +not able to discriminate sufficiently between the direction of the +experimenter's eye and that of his head, which two directions did not +always coincide. Finally the horse's attention was often diverted, while +he was running toward the piece indicated, by the other pieces lying to +the right and to the left, and for this reason the addition of a single +piece to the otherwise unchanged row of five pieces tended to decrease +greatly the chances of success. + +The case is different with the perception of the directive signs for +tapping, for nodding and shaking the head, etc., all of which require +the perception of movements. This is not necessarily more difficult on +account of the imperfect constitution of the tissues that serve for the +refraction of light. Some authors even aver that this facilitates the +perception of moving objects. This view was first advanced by the +excellent ophthalmologist, R. Berlin[39] of Stuttgart. In arriving at +this view he was guided by the following considerations. The peculiar +form of astigmatism of the lens of the horse's eye, which Berlin has +described as "butzenscheibenförmig",[Y] because it appears in the form +of a series of glossy concentric circles around the lens nucleus, has +the property of enlarging the pathway (and with it the rapidity) of +moving retinal images. If we take a speculum by means of which a view +may be had of the interior of the eye, and fixate a definite point on +the retina of the horse, and then make a slight movement of the head +horizontally, we find that the point fixated moves--apparently at +least--toward the border of the pupil. In a normally constructed eye +this seeming movement will be in a straight line, while in the eye of +the horse, (according to Berlin), its path is curved, and therefore +longer. Berlin believes that the same thing which here occurs in the +case of this merely apparent movement, must also happen when an external +moving object is imaged on the horse's retina. Its pathway, too, will be +curved, and therefore longer, so that if the head of Mr. von Osten moves +past the animal's eye, then the image on the horse's retina will take a +longer, more circuitous route than it would if the eye were not +astigmatic. We cannot, however, immediately conclude from the fact that +an objective movement is imaged as being greater in extent on the +retina, that it will therefore be more readily perceived by much less +that it will appear greater to, the horse, than would be the case if the +lens were normally constructed. The visual percept is not immediately +dependent upon the retinal processes, for between the two are +interpolated complex, inaccessible nervous processes. Still, Berlin +believes that he is justified in drawing this conclusion from a number +of relevant considerations. Accepting it, he believes that it would be +possible for the horse to perceive movements, that for the human eye, +which is not subject to this form of astigmatism, would lie below the +threshold. + + [Footnote Y: "Butzenscheiben" are the small circular panes of green + glass, used in leaded windows in early days. They are high in the + middle (hence the name: "Butze," a protuberance) with a number of + concentric circles around the central elevation.--Translator.] + +This theory, the simplicity of which certainly must make a strong +appeal, has been adopted by a number of well-known investigators +(Schleich[40], Königshöfer[41]). If we also could accept it, then Hans's +phenomenal power of perceiving the movements of objects would be +explained. But doubts arise which restrain us. Even if we were to accept +Berlin's view in general, we should still come upon the following +difficulties. In the first place, it is questionable whether the +peculiar form of astigmatism mentioned is indeed as common as he +supposes.[Z] The references in the literature are exceedingly meager on +this point. In order to make a few tests at least, I undertook to +examine nine horses with the aid of Dr. R. Simon, oculist, to whom I am +greatly beholden for the assistance given in these and other tests to be +mentioned presently. In not one of the nine cases did we discover +anything like the curved deflection which is supposed to be the sign of +the form of astigmatism in question. But in order to test objectively +whether Berlin's assumption were justified, we examined in the +laboratory fresh specimens taken from two horses. The eyes were fastened +in a frame in what corresponded to their normal position. Their +posterior spherical wall (i. e., their respective retinal surface) was +replaced by a piece of ground glass. On a spherical surface linear +movements of a point of light are always imaged as curves, no matter +what the shape of the lens forming the image may be. (For a more +detailed statement see page 170, at close of note.) Since, however, our +investigation had to do only with those curves which were due to the +qualities peculiar to the lens, we had to replace the spherical by a +plane projection surface. In front of the eye thus modified a strong +light was placed at such a distance that the image of it, produced on +the improvised back of the eye by the cornea and the lens, was a sharply +defined point of light. Now, when the source of light was moved, the +point of light would also move on the glass plate. Sitting at some +distance behind the eye, we observed the movements of this point through +a telescope. Thus we became witnesses of what happens upon the horse's +retina when a moving object passes in front of his eye. Although we saw +the point of light move through relatively long distances both +horizontally and vertically, no sort of deflection in its pathway could +be noted. Berlin's exposition does not hold true for the eyes of the +horses, either living or dead, which were examined by us. + + [Footnote Z: Since no opportunity was given us to examine Hans's + eyes we do not know what their condition is in this respect. Though + it would have been interesting to know, it would hardly make any + difference in the views presented. If Hans should prove to be either + far or near-sighted, then, if we are to make any supposition at all, + it would be that the defect could not be very great, since near + sightedness exceeding 2 or 3 diopters and far-sightedness exceeding + one diopter is seldom found in the case of the horse. According to + Mr. von Osten, Hans at one time manifested a tendency to shy easily. + Be this as it may, for little could be concluded from it, since in + many extremely shy horses, no kind of visual imperfection can be + discovered.] + +But in the case of some of the horses in whom Berlin had seen the +phenomenon for which we sought in vain, he himself tells us, the +deflection was very slight. In that case, it would appear, no great +advantage would be gained along the lines indicated. But even assuming +the degree of deflection to be very great, his theory goes to pieces on +the very point it was supposed to explain. A concrete example will make +this clear. If Mr. von Osten, standing two feet away from the horse, +raised his head 1/5 millimeter (which figure by no means represents the +extreme values that were obtained), then in the horse's retinal image +every point of the man's head would move through a distance of 0.0025 +millimeter--assuming the horse's eye to be free from astigmatism and +assuming its focal distance to be 25.5 millimeters. If, however, other +conditions remaining the same, we presuppose an extreme form of +astigmatism, one in which the path of the retinal image is not a +straight line, but is deflected into a semicircle, then each point would +pass through a distance of nearly 0.004 millimeter. If the sensitive +retinal elements have a diameter of 0.002 millimeter (as Berlin, +somewhat inexactly, states), then from two to four elements would be +stimulated in case there were no astigmatic deflection. But in case the +deflection did take place, it would not necessarily involve more +elements, as can be seen by making a simple graph; indeed we can imagine +cases in which the circuitous path would involve even fewer elements +than the straight one. And finally, when the movement which the horse is +to perceive, does not occur in a straight line but in the form of a +curve, (which will generally be the rule), then the astigmatism will +tend in many cases to decrease the curvature of the image's path on the +retina, and sometimes even obviate it entirely. In all these cases, on +Berlin's own theory, the perception of the movements would be hindered +rather than aided.[AA] + + [Footnote AA: For the benefit of specialists I would say the + following in addition to the more general remarks just made. For the + most part, the determinations of refraction made on the eye of the + horse are still rather unreliable. In sciascopy there is a dispute + among investigators concerning ambiguous shadows, and in the use of + the refraction-ophthalmoscope no definite region of the eye's + background has been adhered to by the various investigators. It + appears that Riegel, whose diligent researches mentioned on page 164 + were published in 1904, knew nothing concerning the round area in + the horse's eye, discovered by I. Zürn[42] in 1902. Also, if so + great a degree of astigmatism is really the rule as is emphasized + especially by Hirschberg[43] and Berlin,[44] then the simple + refractive index usually given--sometimes within a half + diopter--would be meaningless. Berlin[45] and Bayer[46] believe the + vagueness of the retinal image resulting from the astigmatism, is + offset by this: that the oval pupil functions as a stenopaic slit. + In view of the width of the horse's pupil this appears to me to be + rather hypothetical. + + Concerning Berlin's theory of deflecting astigmatism I would say the + following: Of the two ophthalmoscopic signs mentioned as being + characteristic of this form of astigmatism,--the concentric circles + and the arcuate deflection of the pathway of the fixated + points,--when there is a movement of the eye of the observer (or of + the eye observed), according to Berlin the former is not so constant + as the latter. So far as I know, the concentric ring formation is + mentioned only by Bayer[47] and Riegel,[48] and is said to occur + principally in horses with myopic vision--and hence, relatively, in + a minority of cases. Judging from the particulars, we are inclined + to believe that a case of "Butzenscheiben"-lens reported by + Schwendimann[48_a_] is in reality a case of senile sclerosis. + Berlin repeatedly warns us against mistaking the one for the + other.[48_b_] The arcuate deflection, on the other hand, has not + been mentioned elsewhere as a personal observation. In Berlin's + calculation[49] of the increase in the extent of the retinal pathway + an ambiguity has crept in. He says that "in the astigmatic eye there + are stimulated 207 times as many nervous elements as would be + stimulated in the ideally normal eye." It ought to read "207 more" + instead of "207 times as many." And this number holds only for the + one case computed by Berlin, and under the specific assumption that + exactly [Greek: pi]/2 times the normal number of elements were + stimulated (571 instead of 364). Therefore the general statement + which Bayer[50] makes in his text-book, that according to Berlin's + evaluation "207 times more nervous elements" are stimulated in the + astigmatic eye than in the non-astigmatic one, does not hold true. + + Closing this note, a few remarks concerning the experiments made by + Dr. Simon and myself. All of the nine horses were tested for the + vertical image by means of the ophthalmoscope. In most cases Wolff's + electric speculum was used. Atropine was not employed.--For the + laboratory tests the adipose and the muscular tissues were removed + from the eye-ball and the rear part of the bulb cut away. The front + part, containing the cornea and the lens, was fastened over one + opening of a metal cylinder which was closed at the other end by + means of a disc of ground glass. The whole, approximately as long as + a horse's eye, was filled with a normal salt solution whose + refractive index (1.336) corresponds quite closely with that of the + vitreous humor of the horse's eye. The pressure from within was + regulated so that on the one hand it was not dimmed and yet on the + other there were no wrinkles in the cornea. The source of light--the + filament of a Nernst lamp--was moved about in a plane 120 cm. + distant from the eye and perpendicular to the optic axis. It was + moved through the point of intersection as well as at various + distances from it. Movement in horizontal and vertical directions + was in each case along lines 150 centimeters in length, which would + correspond to an angle of vision of not less than 64°. The pathway + of the imaged point was controlled by means of the cross-hairs of + the telescope. If in the same way we observe through the sclerotic + of an intact eye-bulb a point of light falling upon the retina and + shining through the sclerotic and choroid (which is not difficult + when we use an intense light), then to the observer its pathway + will, of course, appear to be deflected convexly toward the + periphery,--and the deflection will appear the greater, the farther + the point of light is removed from the optic axis.] + +But to come now to the most pertinent objection. We saw that Berlin's +whole train of thought rested upon the assertion that it made no +difference whether we regarded by means of the speculum the seeming +movement of a fixed retinal point, or whether the image of an external +moving object is passing over the horse's retina. As a matter of fact, +however, these two processes are very different from one another. In +moving the mirror, with its small opening we are looking through ever +changing portions of the horse's lens,--testing it out, as it were. The +horse, on the other hand, sees with all parts of the lens +simultaneously, in so far as the lens is not covered by the iris. The +arcuate deflection, which is nothing but a registration of the +difference in the indices of refraction of the different parts of the +lens used consecutively, might thus be formed for the observer using the +mirror, but never for the horse. For these reasons we cannot conclude +that the kind of astigmatism described can really increase the horse's +acuity in the perception of movements. + +Since the light-refracting apparatus of the horse's eye does not offer a +satisfactory explanation for the extraordinary keenness of visual +perception possessed by the Osten horse, we must go a step further and +ask whether it may not perhaps be found in the part immediately +sensitive to light, the retina. That portion really would seem to be +adapted to the perception of movements of minimal extent, and for this +reason: it is more than three times as great in extent as the human +retina, and the horse's retinal images are likewise larger owing to the +position of the nodal point. The cells of the retina that are sensitive +to light, the rods and cones, might therefore be correspondingly larger +than those of the human eye, without thereby making the whole organ less +efficient than the human eye. But the most recent measurements[51] have +shown that the rods and cones of the horse's eye are more minute than +ours. Assuming that, in the case of the horse, as is presumably the case +in human vision, the transition of a stimulus from one retinal cell to +the next already in itself induces a sensation of movement, then the +horse ought indeed be extraordinarily keen in the perception of moving +objects (provided that the horse's more minute cells are packed just as +closely as in the human retina). And besides, there are two specially +adapted areas within the retina of the horse. The "band" +("streifenförmige Area") which was discovered fifteen years ago by +Chievitz,[52] is a strip of 1 to 1-1/2 millimeters in width, traversing +the entire retina horizontally, and is noteworthy on account of its +structure and probably, too, on account of its greater efficiency. It +may have something to do with the accomplishments of the Osten horse; +but in how far it would be hard to say. The other noteworthy portion of +the horse's retina is the "round area" discovered some four years ago, +located at the rear outer end of the "band", and it is the best-equipped +part of the horse's retina and corresponds to the area of clearest +vision, the yellow spot, in the human eye. But this round area need not +come in for consideration by us, for its location would indicate that it +is used in binocular vision, that is, seeing with both eyes.[53] But in +all our experiments the Osten horse observed only with one eye. That +does not mean, however, that under other circumstances the round area +may not be of very great importance. + +In the present state of our knowledge, all attempts at explanation are, +of course, of the nature of hypotheses. If further investigations should +disclose this explanation to be untenable, then we would either have to +suppose some unknown power in the eye of the horse,[AB] or else seek a +cause in the animal's brain. Further experiments on other horses would +be necessary in order to discover whether the species as a whole +possesses this ability or whether only certain ones are thus endowed. +The former is of course more probable. In this particular case +conditions were unusually favorable for the development of this +ability. We must bear in mind that in all probability Mr. von Osten's +movements very gradually became as minute as they are now, and that +therefore Hans at first learned to react to such as were relatively +coarse. Furthermore, his practice extended throughout four years and +during this time it was his sole occupation. Without specific +predisposition, however, all this practice would have been utterly +futile. We can also readily appreciate how indispensable in the struggle +for existence a well-developed power of perceiving moving objects must +be to horses (and most other animals) living in their natural condition +and habitat, in order to be aware of the approach of enemies, or, in the +case of carnivora, the presence of prey. In view of all these +considerations we can readily see how it was possible that the horse, +perhaps in spite of rather defective vision, could react with precision +to movement-stimuli which escaped observation by human eyes. + + [Footnote AB: Königshöfer, who as we have already said, seconds the + explanation given by the ophthalmologist Berlin (and who confounds + "Butzenscheiben" astigmatism with the common, so-called regular + form), believes[54] that not only astigmatism but also the shape of + the blind-spot of the eye must be taken into consideration. This + portion of the retina, where the fibres of the optic nerve enter the + eye (and called "blind-spot" because there are no cells there that + are sensitive to light) is very nearly circular in man, but differs + in shape in the different species of animals. Königshöfer thought he + had discovered that a relatively elongated blind spot was favorable + to keenness of vision. If we place the mammalia in series on the + basis of their relative keenness of vision, he says, we would find + that this series is identical with the one in which they are grouped + with reference to the form of the blind-spot from the circular up to + the most elongated. (In such a series the marmot takes the place of + honor.) + + This exposition is not very satisfactory, however. We cannot be sure + what he means by "keenness of vision" ("scharfäugigkeit"). Is it + visual acuity in the usual sense of the term (as is said in one of + his passages), or keenness in the perception of the movements of + objects, (this would appear to be his real meaning), or both at the + same time. But whatever the significance he may put into the term, + any such attempt at grouping the lower forms must prove + unsatisfactory from the very start on account of the scant data + which we possess on visual perception in animals. The experiences of + the hunt upon which Königshöfer partly bases his view, are entirely + inadequate for such a purpose. This much is certain, that the Osten + horse, in spite of a blind-spot which, though somewhat oval, is by + no means very elongated, possesses an extraordinary acuity in the + perception of movements. Even if the parallelism mentioned by + Königshöfer were really shown to exist, it would not explain the + matter until it were also shown in what way keenness of vision is + dependent upon the shape of the blind-spot,--a portion of the eye + which is not immediately operative in the visual sensation at all.] + +We can understand also the horse's never-flagging attentiveness when we +recall that self-preservation prompts eternal vigilance over against all +that is going on in the animal's environment. (In the case of Hans, +hunger was at first the motive; later, habit did the work.) Furthermore, +the lower form is not hindered in giving itself over to its +sense-impressions by the play of abstract thought which tends so +strongly to direct inward our psychic energy,--at least, in the case of +the cultured. + +Nevertheless, Hans still remains a phenomenon not only in excelling all +his critics in the power of observation, but also in that he is the +first of his species, in fact the first animal, in which this +extraordinary perceptual power has been proven experimentally to be +present. It has long been known[55] that horses could be trained to +respond to cues in the form of slight movements, which remained +unnoticed by the layman, and this fact has been made use of by circus +trainers to its fullest extent. But such signs, I have discovered, are +without exception, of a far coarser sort than those we have here +described, and they can be instantly detected by the practised observer. +Nor was it known to professional trainers that it was possible for the +master to direct a horse to any point of the compass simply by means of +the quiet posture of the body. For this reason it was believed that no +signs could possibly be involved in the color-selecting-tests (cf. +Supplement III, page 255). In this we have the support of some of our +experts, as is witnessed by the following extract from a letter of his +Excellency Count G. Lehndorff, one of our best hippological authorities, +who at one time carefully examined the Osten horse. (The letter was +addressed to Mr. Schillings, and I have permission of both gentlemen to +use it). In it he says: "If the author's statements, in which you also +have concurred, are correct, and if, as a matter of fact, the horse +really does react to such minute movements as are absolutely +imperceptible to the human observer, then we have indeed something quite +new, for hitherto no one would have believed that horses can perceive +movements which man cannot. But I am even more surprised by the +explanation of the color-selecting feats.--This too, is something +absolutely new. One would not have deemed it possible that a horse could +do anything of the kind simply by using the posture of a man's body as a +cue to which it could react with such precision." + +And yet, even though both facts were new concerning the horse and had +not hitherto been proven experimentally regarding any other species, +nevertheless something of this sort has been known concerning the dog +for some time. His ability to single out an object upon which his master +had intently fixed his gaze, was made the basis of a special form of +training, called "eye-training,"[56] nearly one hundred years ago. The +dog was taught to focus constantly upon his master's eyes and then upon +command to select the object which he, the master, had been fixating. +Such a dog has been described by the naturalists A. and K. Müller.[57] +But the master of the dog, unlike Mr. von Osten, would not permit anyone +else to work with the animal, and the two brothers, recognizing the +trick, were justified in adding that "the whole affair aimed at +deceiving the public, and the dog's reputation was but a means of making +money". The success of such exhibitions appeared furthermore, to depend +upon the close proximity of the trainer and the dog, whereas the +direction of the head (and even of the body) could very probably be +perceived at greater distances also. At least we learn from a reputable +source that in the hunt, dogs can perceive from the mere posture of +their master, what direction he intends to take.[58] + +But a still more curious fact is this, that dogs, too, learn--evidently +spontaneously--to react to the minimal involuntary expressive movements +of their master. The first example mentioned in the literature on the +subject is that of an English bull-dog called Kepler, belonging to the +English astrophysicist, Sir William Huggins.[59] We are told that this +dog seemingly could solve the most difficult problems, such as +extracting square roots and the like. The numbers were indicated by +barking,--thus one bark was for one, two barks for two, etc. Every +correct solution was rewarded with a piece of cake. Huggins states +explicitly that he gave no signals voluntarily, but that he was +convinced that the dog could see from the questioner's face, when he +must cease barking, for he would never for an instant divert his gaze +during the process. Huggins was unable, however, to discover the nature +of the effective signs. This satisfactory, though still unproven, +explanation has been accepted by specialists, among them Sir John +Lubbock.[60] I, too, regard this dog as a predecessor of our Hans. + +A similar case is reported by Mr. Hugo Kretschmer, a writer of Breslau, +in the "Schlesische Zeitung" of August 21, 1904. To him I am beholden +for a detailed written statement, which he has kindly permitted me to +use in this connection. The gentleman named, first trained his dog to +ring the table-bell, and this, by pressing the dog's paw upon the +bell-button. When the dog had learned to do this independently, his +master tried to teach him the rudiments of numbers, in such a way that +the animal was to give one ring of the bell for the number 1, two for 2, +etc. But these attempts failed utterly and had to be abandoned. But Mr. +Kretschmer had noticed that he was able to get the dog to ring any +number which he, Mr. Kretchmer, might decide upon. (Success was always +rewarded by a bit of bread and butter.) At first Mr. Kretschmer tried to +imagine vividly only the final number, but failed thereby to elicit +correct responses from the dog. But he did succeed when he tried making +a series of separate volitions. Thus for the number 5, he would "will" +each separate push of the button on the part of the dog. Even so, +however, he never got beyond 9, for then the dog would become impatient +and would ring the bell continuously. Anything that diverted the dog's +attention, such as noises, etc., also entailed failure. In these tests +master and dog had faced each other, each gazing steadfastly at the +other. Mr. Kretchmer was convinced, however, that the dog was not guided +by any sort of sign, but rather by suggestion. He based his belief on +the following two observations. After some practice, he says, the tests +were also successful when he did not look at the dog, but stood back to +back with it, or when he screened himself from the dog's view by +stepping to one side behind a curtain. The tests were unsuccessful, on +the other hand, whenever he was mentally fatigued or had taken some +alcoholic drink. The arguments do not appear to me to be adequate. If he +turned his back upon the dog and no other observer was present, he had +no means of knowing whether the dog did not, after all, peer around to +get a peep at him. If others who knew the desired number, were present, +the dog might have gotten his cues from them. And there may be some +doubt whether the curtain adequately served the purpose for which it was +intended. At any rate, it was added that all attempts to influence the +dog from an adjoining room--which would thus exclude effectively all +visual signs--were utter failures. I am also strengthened rather than +weakened in my belief, by the second argument which Mr. Kretschmer +makes, viz.: that mental fatigue or the use of alcohol on the part of +the questioner tends to make the result unsatisfactory. We noted a +similar effect in the case of the horse (page 150), where a disturbance +of the "rapport" between the questioner and the horse was invoked by +some by way of explanation. The facts were explained by us much more +simply. We attributed the result to the close correlation between the +type of mental concentration and the nature of the expressive +movements--a correlation which we have shown experimentally to exist. I +cannot, therefore, subscribe to the view that this dog did not require +either visual or other sensory signs. The tests which were made for the +purpose of strengthening that view, are on a par, I believe, with those +mentioned on page 45. And since auditory, olfactory, and other stimuli, +though not impossible, still are improbable, I believe that our Hans, +Huggins's dog, and the one belonging to Mr. Kretschmer, differ from one +another only in this, that the first taps, the second barks, and the +third presses a bell-button. + +And finally I have access to a letter from the Rhine Province in which +there is a brief account of a dog that would promptly obey any command +that was given without a sound and supposedly without the accompaniment +of the slightest kind of gesture. It is specially mentioned that the +animal steadily watched its master during these tests. The perception of +the slightest involuntary expressive movements is in all probability the +secret in this case also. Here, too, suggestion has been invoked by way +of explanation, but there was not the slightest attempt made to find for +it a more specific foundation, and we cannot suppress an objection based +on the matter of principle. It is incumbent upon anyone who uses a term +so ambiguous, to define what content he desires to have put into it. If +he does not do this, he is giving us, instead of a concept, a bare word, +instead of bread, a stone. + +While we must reject the explanation based on suggestion,[AC] we +believe, on the other hand, that we have here again, evidence of the +presence of visual signs, given unwittingly and involuntarily, just as I +am sure that they were involved in the two preceding cases, and +similarly in the case of the Huggins dog. Since the effective signs were +discoverable in none of these canine predecessors of Hans, an +investigation would be desirable, based upon the insight gained as a +result of these experiments upon Mr. von Osten's horse. Unfortunately +this is impossible, since the dogs in question are dead. But others like +them undoubtedly exist in many places. We might mention that when Hans +first came under the limelight of public attention, there was also +frequent reference to the Huggins dog, but he soon dropped out of the +discussion again.[63] And this for two reasons. The dog never took his +gaze from his master and appeared to be entirely dependent upon him in +his reactions. Hans, on the other hand, seemed to give evidence of a +high degree of independence and never appeared to look at the +questioner. But we know now that, though he was never dependent upon the +will of his master, he, too, abjectly hung upon the man's involuntary +movements and never for a moment lost him from view. But since the horse +is able to observe with one eye alone, and needed to direct only it and +not the entire head toward the questioner, in order to focus +comfortably, one could not conclude as to his line of vision from the +direction of the head. Since, furthermore, in the horse the pupil is +hardly distinguishable from the darkly pigmented iris and since the +white sclerotic is hidden by the eyelids, except when the eye is turned +very much, it is difficult to determine what direction the eye is +taking. I once purposely stepped backward to the horse's flank, so that +he had to turn his eye far back and thus the outer border of the iris +and the white sclerotic coat became visible and all doubt concerning the +line of vision was removed. This doubt could never arise in the case of +the dog, the median plane of whose head is always directed toward the +object fixated, and Zborzill is justified in saying, as he does, in his +discussion of training of the kind mentioned on page 177, "But any +careful observer can immediately guess the manner in which such a dog +has been trained."[64] If Hans had chanced to possess so-called +"glass-eyes"--in which the dark pigment is wholly or partly lacking, so +that the black pupil is clearly defined against the lighter +background,--then no doubt could ever have arisen concerning the +direction of the eye, and Hans never would have come to be regarded as +the "clever" Hans. + + [Footnote AC: I can find examples of supposed suggestion in the case + of animals given only by Rouhet.[61] He says that by means of + suggestion he taught a half-year old half-blooded mare-colt which he + had raised himself, to fetch and carry, and this in a very short + time. In order to indicate to the colt what was wanted, Rouhet would + concentrate with his whole mind upon the object intended (a watch), + and at the same time he would bend forward slightly. In the third + test, that is at the end of fifteen minutes, he had accomplished his + purpose, and in the tenth lesson, no more mistakes occurred. The + colt would fail to respond, however, as soon as he refrained from + making any gestures, or was in a laissez faire frame of mind, or + when he thought of other things. He therefore believes that there + must have been some kind of immediate, though inexplicable, + connection between the brain of the trainer and that of the horse. I + think the explanation is evident: the connection was not as he + thought, an immediate one, but arising through the mediation of the + man's attitude ("attitude un peu baissée"), and of his movements + ("gestes"), both resulting from his intense concentration ("tension + de la pensée"). + + In general we may say that, no matter what content we may wish to + put into the term "suggestion," not a single fact has since come to + light which would justify, and much less demand, the application of + the term to lower forms, unless we would expand the definition of + the term to the extent of comprising every kind of command, every + arousal of ideas, whatsoever. But it would then be nothing but a new + name for old knowledge[62] and would lose all explanatory value. + (Hypnotism, so-called, in the case of horses, I shall discuss + elsewhere in another connection.)] + +After the publication of the December report, Hans acquired a reputation +for excellence in thought-reading and thus the discussion of +thought-reading among animals in general became once more the order of +the day. That is to say that many of our domestic animals are--like the +human mind-reader (à la Cumberland),--supposed to have the ability to +infer the thoughts of their masters from slight, involuntary movements. +They are thus aware when the feeding hour approaches, when they may go +out in the open, etc. They also appear to be aware that their welfare +lies in our hands, and therefore would seem to have a vital interest in +divining our intentions and our wishes. Not only our spoken words, but +also numberless movements--usually without our knowing it and often +contrary to our desire--speak a clear language. As is well said by the +American neuropathologist, Beard,[65] (who first explained the +phenomenon of thought-reading, on the basis of the perception of very +minute muscular jerks, and therefore called it "muscle-reading" or +"body-reading"): "Every horse that is good for anything is a +muscle-reader; he reads the mind of his driver through the pressure on +the bit,--though not a word of command is uttered." We know that in the +case of perfectly trained horses the rider's mere thought of the +movement which he expects the horse to make, is seemingly sufficient to +cause the animal to execute it.[AD] Such cases are of course very much +like that of our Hans, excepting that instead of visual signs they +involve aids of a mechanical nature, which, however, does not alter the +general principle, since both of them are of the nature of sensory +stimulation. But we must not overlook the essential difference between +this so-called thought-reading on the part of animals and that which is +done by man. The human thought-reader can interpret movements, for he is +familiar with the ideas which are their source. Thus when at the second +tap, I notice a very slight jerk of the subject's head, and a stronger +one at the fifth tap, I infer that he thought of the problem 2+3=5. +While the experimenter thus cannot be said to read thoughts, he still +infers them. The animal, on the other hand, we may be reasonably sure, +draws no such inferences. In its conscious life it remains ever on the +sensory level. If we could ask Hans about it, he would probably answer: +"As soon as my master stoops forward, I begin to tap; as soon as he +moves, I stop. The thing which induces me to act thus is the carrot +which is given me; what it is that induces my master to make his +movements, I do not know."--It is therefore erroneous to believe that +animals require the power of abstract thinking in order to utilize the +signs which are consciously or unconsciously given them, as is argued by +Goldbeck[68] when he says with reference to the training for visual +signs, which we have already mentioned before: "There the dog has +consciously interpreted the visual impression in terms of the conclusion +that he is expected to bring forth the leaf indicated." Nor was there +any justification for the critic who thought he could put the essence of +the report of December, given in Supplement IV, into the following +words: "He (Hans) showed that he has the power of attention, can draw +logical conclusions, and can communicate the result of his +thinking,--and all this independently." Yet none of this had been +asserted. The whole thing may be explained satisfactorily by means of a +process of simple association established between the signs observed in +the master and certain reactions on the part of the horse. The fact that +the movements made were so exquisitely minute does not change the matter +in the least. Such signs call for a high degree of sensory keenness and +great concentration of attention, but by no means an "extremely high +intelligence." + + [Footnote AD: An illustration is given by Babinet[66] concerning the + horse of an English lord. Mr. Burkhardt-Foottit, also, that + excellent trainer, who has been master for more than forty of the + most highly-trained horses, tells us that while sitting on a + well-managed horse it sometimes happened that he had merely thought + of making a certain turn, when the horse immediately executed it, + before he, the rider, had to his knowledge given any sign or aid. An + observation belonging under this head is also made in Tolstoi's + "Anna Karenina"[67], this perfect mine of acute psychological + observation. In the famous description of the race we are told + concerning Count Wronskij riding his Frou-Frou just behind Machotin + mounted upon Gladiator, who was leading the race: "At the very + moment when Wronskij thought that it was time to overtake Machotin, + Frou-Frou, divining her master's thought, increased her pace + considerably and this without any incitement on his part. She began + to come nearer to Gladiator from the more favorable, the near side. + But Machotin would not give it up. Wronskij was just considering + that he might get past by making the larger circuit on the off-side, + when Frou-Frou was already changing direction and began to pass + Gladiator on that side." Similar experiences might be gathered + elsewhere. Not infrequently the reflection of the rider that his + horse had not for a long time indulged in some trick peculiar to + him, will immediately call it forth; or doubts on the part of the + rider concerning the possibility of crossing some barrier, are often + the cause of the horse's fall or of his refusal to leap and of his + running away.] + +Let us turn now from the consideration of visual perception to that of +auditory perception in the horse. We saw that the fact that Hans was +able to respond to commands which were only inwardly enunciated, that +is, commands which were merely thought of but not spoken, was not proof +of great acuity of hearing, but rather that hearing was not at all +involved. If Hans had been deaf he would, none the less, have promptly +obeyed the commands. Blind and near-sighted horses try to overcome their +deficiency by means of the sense of hearing, and hence show a pronounced +play of ears. In the case of the Osten horse, however, attention has +been diverted from auditory stimuli in the process of habituation to +visual signs, and as a result ear-movements are almost completely +wanting. One is not of course permitted to deny _a priori_ that perhaps +some associations might have been formed between objects and the vocal +signs belonging to them, e. g., between the colored cloths and the names +of the colors if both had been presented together oftener than was the +case. + +But there is a dearth of reliable observation as to how far auditory +associations of this sort may be established in horses. Usually the +following is cited. Horses learn to start off, to stop, and to turn +about in response to calls. They are able to distinguish properly +between the expressions "right" and "left", or equivalent terms. Upon +command they will start to walk, to trot or to run. And they also know +the name by which they are usually called. All authors agree that +cavalry horses understand the common military commands; one writer even +avers that they excel the recruits in this respect.[69] Some believe +that in riding schools the horses pay closer heed to the calls of the +riding-master than to the control of unpractised riders, even when the +two are at variance with one another.[70] My experience with the Osten +horse and a number of other pertinent observations aroused in me the +suspicion that much that is called or spoken in the process of managing +a horse may possibly be just so much labor lost. In consequence I made a +series of relevant experiments. I have thus far tested twenty-five +horses of different kinds, from the imported Arabian and English +full-blood, down to the heavy draft-horse. The experiments were made +partly in the courtyard of military barracks, partly in the circus, and +partly in a riding-school or in private stalls. I am specially indebted +for kind assistance to Messrs. von Lucanus, Busch, and to H. H. +Burkhardt-Foottit and E. Schumann, the two excellent trainers connected +with the Busch Circus. During these tests, the horses were always amid +circumstances familiar to them, whether free or bridled, under a rider +or hitched to a wagon. All aids or signals, except the calls, were +eliminated in so far as it was possible. + +The results of those tests were in substance as follows: Many horses +react to a smack of the lips by a rather fast trot. Many stop on the cry +"Hola" or "Brr". This last was nicely illustrated in the case of two +carriage horses supplied with large blinders and held with a loose rein, +and hitched to a landau. One of them regularly stopped when the "brr" +was given by the driver, whereas the other, which had not been +habituated to this signal, kept serenely on the trot, so that the +vehicle regularly veered off the track--a sure sign that no +unintentional aid was being given by means of the reins. Other horses, +again, were accustomed to halt in response to a long-drawn-out "hola", +but it was the cadence of melody rather than the word that was +effective, since any other word, or even a series of inarticulate +sounds, would produce the same result, provided they were given with the +proper inflection. When this was changed, then the response would fail. + +The result was not so apparent when it came to controlling the kinds of +gait. One riding-school horse, when lunged and in a gallop, could be +induced by a friendly call--the word again was a matter of +inconsequence--to slacken his pace into a trot and from a trot into a +walk. But this reaction was by no means very precise. Another, a +full-blood, contrary to the trainer's expectation and to his great +astonishment, failed to respond to any kind of spoken command as soon as +the one who carried the reins refrained from making any movements which +might indicate what was wanted. (To refrain from all expressive +movements of this kind is by no means an easy matter). The slightest +move, apart from any help by means of the reins or the whip-handle, was +sufficient to evoke a response. The results in the case of the military +horses, differed in many particulars. Thanks to the courtesy of Captain +von Lucanus I had the opportunity of testing three cavalry horses, two +geldings and one mare, aged nine, thirteen, and nineteen years +respectively, and all of them in the regiment ever since their fourth +year. They had been selected as the "most intelligent" in the squadron, +and we were assured that they would obey punctiliously all the usual +commands. They were ranged behind one another, with the customary +distance of two horses' lengths between, and were ridden each by his +accustomed rider. Both starting and stopping upon command were tested. +The horses were held by the reins, but the riders were cautioned to +refrain from giving any aid that might cause the horse to start when +starting was to be tested, or that might restrain him when stopping in +response to the spoken command was to be tested. If a suspicion arose--a +thing which happened only twice, however--that a rider had actively +aided in his horse's reaction, then an officer would mount into the +saddle. If it appeared that one of the horses was simply imitating the +others, then the others were purposely restrained by their respective +riders. The commands were given by the corporal who usually had charge +of the horses. In a few cases the sergeant of the squadron gave the +commands, but this made no difference in the success of the experiment. +Now as to the results. Whenever the horses were trotting or walking, all +commands, without exception, were in vain. They effected neither an +increase nor a decrease in the pace. A result was obtained only when the +horses were standing when the test began; and this result was simple +enough,--upon certain calls the animals would respond by beginning to +walk. This was the only reaction that was obtained. The most effective +of the commands appeared to be "Squadron,--march!" But the command +"Squadron!" or "March!" alone, were quite as effective; yet none of +these commands was obeyed without exception. Reactions were occasionally +obtained in response to "trot!", "gallop!" "retreat!", (the usual +introductory "squadron" was purposely omitted here, because it alone +sufficed to start the horses). But the reactions were always the same, +viz., to start on a walk. Another series of commands (such as those +which are addressed to the rider alone, e. g., "Lances down!") had no +effect whatever; a certain amount of selection therefore did seem to +take place. In all these tests the order of the horses with reference to +each other's position was repeatedly changed. One of the horses, the +youngest, and reputed to be the most "intelligent", (he was as a matter +of fact the most spirited), gave evidence of a gregarious instinct, +intensified by habit, which, if it had been overlooked, might have +become a source of serious error. Not being accustomed to go at the +head, when so placed it started properly in only 18% of all such cases. +When, however, (other conditions remaining the same,) he was put in +second or third place, he started properly in 67% of the tests, and if +we take into account only those cases in which the three most effective +commands were used ("Squadron!", "March!", and "Squadron--march!") he +reacted correctly in 91% of the cases. (The number of tests was 17, 36 +and 22 respectively for the three groups mentioned.) The horse, +therefore, almost always began to step properly when he stood behind one +of his companions, but seldom when he stood at the head. And when he +stood at the head and began to walk at the proper moment, it was plain +that it was a case of imitation and not initiative, for the horse was +still able to see the others, owing to the extent of his field of vision +backward, and he was always the last to move, whereas otherwise he was +always the first to move, and always difficult to restrain. So when the +horses to the rear were restrained or when the intervening distance of +two horses' lengths was lessened, so that this gelding could not see the +one in the rear, he failed completely to respond. Accordingly these +three horses did little to justify the faith which their squadron had +placed in them. + +Now a few words on the manner in which horses react upon the call of +their names. We are not concerned with those that are seldom or never +called by name (such as those in the cavalry). I have not discovered one +horse that constantly and unequivocally reacted upon the mention of its +name (though I would not assert that there are none that would do so.) I +was nearly always able to convince the owners or grooms, who at first +had maintained a contrary opinion, that any inarticulate sound was +capable of producing the same effect as the calling of the name. What +the significance of inflection may be, I am not at all certain. When a +certain one of a number of horses standing in the same stable was +called, all of them responded by pricking their ears, raising their +heads, or else turning about. For this reason the reaction of the horse +specifically called lost all significance. Likewise the call which is +ordinarily used in lunging when the man in the center of the circle +wishes the horse to change its gait, or to advance toward him, also +proved ineffectual as soon as the man inhibited every sort of movement. +A slight nod, on the other hand, was always effective. Several times I +have tried to call horses to me, when they were free and running about +in the arena, but was unsuccessful. After I had given them some sugar, +however, they would always come to me--whether I had called or not--and +would then refuse to leave my side. But this is a matter of common +observation. + +I would, however, regard all of these tests as merely provisional. In +spite of the greatest effort, it was not always possible to control all +the conditions of the experiment, and furthermore, the number of tests +would have to be materially increased in order to yield an appreciation +of the difference due to race, age, and the individual variation and +training of horses. But we may, even now, be sure of one thing. Over +against the certainty with which horses react to visual stimuli (in the +form of movements perceived), it does not appear that the formation of +auditory associations is greatly favored by nature in these +animals,--indeed, auditory associations are far less common than is +generally supposed.[AE] Horses compare very unfavorably with dogs in +this respect. The latter easily learn to react with a high degree of +precision to auditory signs,--as I learned from a series of experiments +which I was enabled to perform. The Osten horse, therefore, does not +stand alone among his kind in his inferior auditory equipment, as one +might be tempted to believe at first blush. + + [Footnote AE: All the authors who have given practical suggestions + for the training of horses, whether free or with lunging reins, have + great faith in the efficacy of calls, but usually recommend a + mingling of calls and movements in the way of signs, (thus + Loiset,[71] Baucher,[72] von Arnim[73]). It therefore cannot be + stated just in how far the calls really effect anything. In other + cases I am inclined to doubt outright the influence which is + ascribed to the auditory signs. Meehan[74] gives an account of a + horse that was exhibited in London in the early 90's of the last + century. Pawing with his hoof, this horse apparently was able to + count and answer questions in arithmetic, and among other + accomplishments he was supposed also to be able to understand + something of language. In reality, however, he merely responded to + cues which were disclosed to the reporter by the trainer. In pawing, + the horse was guided by movements of the trainer, and in nodding or + shaking the head he reputedly got his cue from the inflections of + the man's voice. Is it not probable that in this latter case it was + the movements which accompanied speech that were alone effective in + inducing the nod or the shake of the head, so that the exhibiter was + deceiving not merely the public, but also himself? Perhaps we may + also doubt the exposition made by the well-known hippologist, + Colonel Spohr.[75] He tells us that it is easy to train horses to + raise the left foot or the right foot in response to the commands + "Left--foot!" or "Right--foot!" and that it will be the fore foot + when one is standing in front of the horse, and the hind foot if one + stands near the rear. It cannot be so very difficult, he thinks, + even to get the horse to understand the commands "Left (or + right)--fore foot!" and "Left (or right)--hind foot!"--and all + without any other aids but the spoken words. Should this really be + possible without even the slightest kind of designating + movement?----The following case, again, I believe is undoubtedly + based upon a misinterpretation. Redding[76] relates concerning his + nineteen-year old horse that he himself had owned for thirteen + years, and had always kept in single harness,----that this horse not + only understood the meaning of a long list of words, such as: + bureau, post-office, school, churchyard, apple, grass, etc., but he + also knew a number of persons by name, as well as their places of + residence. If he were told in advance to halt at a certain + residence, he would do it without any further aid from the driver. + For this reason the happy owner felt certain that the animal + possessed a high order of intelligence and "that this horse does + reason." What sources of error were here operative, whether signs + were given by means of reins, or head or arm movements, could be + determined only by a careful examination of the case. + + And finally we would exercise some reserve in entertaining the + suggestions for the acoustic education of horses which have come + from various sources. Colonel Spohr[77] whom we have just been + mentioning, thinks that it would not be a difficult matter to get a + horse to respond with a walk to one smack of the lips, with a trot + to two smacks, and with a galop to three, and then he could be made + to slacken his pace once more into a trot in response to one + long-drawn "Pst!" and to stop in response to two. Others have gone + even further. Decroix,[78] at one time leader in veterinary affairs + in France, conceived the idea of working out a universal language as + regards the commands that are given to horses, in the humane purpose + of sparing them the whip. He called it "Volapük hippique." For the + commands "go," "right," "left," and "halt," he suggests these: "Hi!" + "Ha!" "Hé!" and "Ho!" respectively. From these it was possible to + make eight combinations, such as "Hi! Hi!" for "Trot!" "Hé! Hé!" for + "Left about" (while the single "Hé" was to mean "Forward, to the + left!") "Ho! Ho!" for "Back!" etc. Decroix thought that the whole + system could be inculcated in a very few lessons. He even had a + medal struck which was to be awarded to the driver or rider who + should first exhibit a horse, thus instructed, to the Société + Nationale d'Acclimatation de France (of which Decroix was + president). Eight years have elapsed since then, but we have heard + of no one who has earned the medal mentioned. In the future greater + care will probably be exercised in the putting forth of such + suggestions, and two sources of error may be guarded against, viz.: + involuntary movements on the part of the rider or driver, and + imitation of the horses amongst themselves. (One horse, guarded by + an experienced rider, may serve as copy for ten others with + inexperienced men in the saddle.)] + +It is easy to explain the musical accomplishments. The tones which were +played for the horse, were known to Mr. von Osten, since he himself +played the harmonica, or when someone else played it, he, Mr. von Osten, +could see the stoppers. He then thought of the number which indicated +the tone in question, and Hans would tap it. Thus arose the tale of the +horse's absolute tonal memory. This tale gained much support at the +time, from an experience which has been recounted to me by the +well-known composer, Professor Max Schillings. It shows more clearly +than any other report how very confused were the threads that had been +spun in the whole matter. In order to test the horse's musical ability +Prof. Schillings played, let us say, three tones upon the accustomed +instrument. Complying with Mr. von Osten's wish, Prof. Schillings always +indicated which three he was about to play. The horse always tapped them +correctly. In order to make a decisive test, Prof. Schillings then +played, without anyone's knowledge, a note that was in reality a third +below the one he had indicated to Mr. von Osten. Curiously enough, Hans +tapped, as a matter of fact, the number indicating the note that was +actually struck, and it was only in the third repetition and after many +exhortations on the part of the master "to have a care", that the horse +finally tapped the number indicating the note Mr. von Osten had in mind +and which in truth was the wrong one. This curious experiment seemed to +those to whom Professor Schillings communicated it, to yield conclusive +evidence of the horse's absolute hearing. As a matter of fact, however, +Prof. Schillings had unwittingly, and, contrary to any intention on his +part, inspired the horse. Standing, as he did, just behind the right +shoulder of the horse, he was able to interrupt Hans (who had begun to +tap in response to a move on the part of Mr. von Osten,) by means of an +involuntary movement which did the work of a closing signal. At the same +time Mr. von Osten, likewise standing to the right of the horse and +expecting more taps, remained perfectly quiet. (This is as it was in +the tests, mentioned on page 71, in which, of two experimenters, one +started the horse tapping, and the other stopped him.) Mr. von Osten +very probably lost patience after Hans had seemingly given the wrong +response twice, and thereupon came nearer to the horse and thus by +monopolizing its attention--so as to exclude Prof. Schillings--he was +able to get the response so ardently desired.[AF] When, in tests such as +these, two stoppers were opened and thus two notes sounded, Mr. von +Osten would count the number of stoppers intervening between the two, +and Hans would tap the number. And so arose the tale of Hans's knowledge +of musical intervals. Whenever the two notes were sung or whistled, in +which case there would be no stoppers that could be counted, then Mr. +von Osten, who was quite destitute of musical knowledge, was at a loss, +and also Hans. If, however, the intervening notes were sung, then +everything went smoothly once more. Major and minor chords were +regularly characterized as "beautiful", all others as "bad", (but even +here errors occurred). A musician had taught Mr. von Osten these +distinctions. The old man also knew the melodies that were played on the +hand-organ. Each one had a number assigned to it, and Hans was required +to tap the number of the melody in token of recognition.--Hans was as +ignorant of musical time, as he was of melody, and all attempts to get +him to march in regular step were utterly futile. A number of musical +tests were made in the absence of Mr. von Osten. In these Mr. Hahn +undertook the questioner's rôle, and since he had had musical training, +he was aware of what the numbers should be, even when he could not see +the stoppers of the harmonica, and, therefore, we readily understand why +it was that the horse responded so wonderfully in his case. + + [Footnote AF: General Noizet[79] has left us a story of the middle + of the last century, which in essential detail corresponds closely + with the one just given. The scene is a French chateau and the hero + is--a rapping table, highly prized on account of the intelligent + answers it could give. Seated about it were a number of ladies and + at the other end of the room sat a French savant, a member of the + Academy. The ladies requested him to put a simple mathematical + question to the table, and complying with their request, he asked + for the cube root of 4. None of the ladies who sat about the table + knew the solution; the table unhesitatingly gave 6 raps. This answer + was refused as incorrect. The table was asked to try again, and + again it wrapped 6. For this it was bitterly reproached. Hereupon + the questioner, who during the whole time had remained in his place + at the other end of the room, came forward with the confession that + the table was innocent, that he had made a mistake. He had asked for + the cube root of 4, but had really meant to ask for the cube of that + number, viz., 64, and the table had as a matter of fact given the + first numeral of that number. + + One is immediately struck by the analogy between this case and that + of Professor Schillings. In both cases those immediately concerned + (the women in the one, Mr. von Osten in the other) believe that a + wrong answer is being given repeatedly. The cause of the error lies + in a person who seemingly is not concerned with the response. (The + Frenchman asked the question, but did not sit at the table. + Professor Schillings sounded the notes, but it was Mr. von Osten who + got the horse to tap.) In both instances the questioner asks one + thing, but had something else in mind. (With the Frenchman it was a + slip of the tongue; Mr. Schillings did it purposely.) And finally, + in both cases the response corresponds not to the question that has + been asked, but to that which has been thought, so that, though + seemingly wrong, the responses of both table and horse were really + correct. By way of explanation, Noizet believes that he has a case + of true thought-transference or "telepathy" (page 108). The + questioner watched with utmost attentiveness the rapping of the + table, and the women in turn regarded the man. And thus, Noizet + believes, the man's thought was transferred to the minds of the + others without the mediation of eye or ear, etc., and hence + unvitiated by the words that had been spoken. I myself prefer + another explanation. At that moment in which the rapping arrived at + the expected number, the Frenchman executed a movement + characteristic of release of tension and to this the women of the + circle reacted. It was not necessary that they should be able to + account for this afterward, (just as sometimes occurs in the case of + thought-readers[80]). It is very probable, too, that they were not + of a very reflective turn of mind anyway. We are warranted, I think, + in regarding the two cases as identical in kind.] + +The so-called musical ability of horses appears, from all that is known, +to be confined within very narrow bounds. Only one fact is universally +accepted, viz., horses of the military are believed to possess a +knowledge of the significance of trumpet signals, and are often said to +interpret them more readily than the recruits.[81] Since no experiments +had been made along these lines, I undertook to make a brief test of the +cavalry horses mentioned on page 188. As in the preceding tests, the +three animals were arranged behind one another with the customary +distance of two horses' lengths between, and each was ridden by his +accustomed rider. They were held by the reins, but received no aid of +any kind, either to start them or to restrain them. A bugle then sounded +the various signals at the other end of the barrack's courtyard. We had +been previously assured that the horses would certainly react without +fail. But, as a matter of fact, the result was quite the contrary. Two +of the horses did not move at all, and the third, a thirteen-year old +gelding, was startled nearly every time and would tear off in a +gallop--even though a trot had been sounded. I would not, however, +venture to draw any conclusions from results such as these. Many more +tests would have to be made, and some of them upon the whole squadron, +before a judgment could be given.[AG] + + [Footnote AG: Professor Flügel,[82] basing his statements on an + article appearing in "Schorer's Familienblatt" (Berlin, 1890, No. 8, + p. 128), gives an account of similar experiments which were supposed + to have been conducted by the Zoological Society for Westphalia and + Lippe, and presumably showed that "the horses of the military do not + understand the bugle calls." No matter how well trained a horse may + have been, it would not respond to a signal. This report, however, + is due to a mistake. Such experiments have never been made by the + society mentioned, so I am told by its director, Dr. Reeker. Nor do + I know of any one else who has made experiments of this kind. + However, Professor Landois,[83] the eminent zoologist, now deceased + (founder of the scientific society mentioned), tested four + circus-horses for their musical ability and specifically for their + sense of musical time. He arrives at the conclusion that horses + "have no feeling for time, whatsoever." With but few + exceptions,[84, 85] all experts to-day are of the same opinion. + Horse-trainers, especially, are universally agreed on this point. It + is easy to see in any circus performance that it is not the horses + that accommodate themselves to the music, but that the music + accommodates itself to them, and that the trained horses[86] are + induced to do their artistic stepping only by the aids given by + their riders. Furthermore, all these horses are trained without the + use of music.----It would therefore appear that the time had arrived + when the tales of the dancing horses of the Sybarites ought no + longer to gain credence. Two Greek writers, Athenaeus[87] and + Ĉlian,[88] tell us that the inhabitants of Sybaris, far-famed for + their luxurious habits, had trained their horses to dance to the + music of flutes during their banquets. Building upon this, the men + of Crotona, in one of their campaigns against the Sybarites, ordered + the flute-players to play the tunes familiar to the Sybarite horses. + Immediately the well-trained steeds began to dance, thus throwing + the whole Sybarite army into confusion, and the men of Crotona won + the day. (The same story is told in more detail concerning the + horses of the inhabitants of Cardia. Both accounts, somewhat mixed, + are to be found in Julius Africanus,[89] a writer of the third + century of the Christian era.)--In recent years a French veterinary + surgeon, Guénon,[90] experimented on the effect of music upon the + horses of the military. He entered their stalls, playing upon a + flute, and noted their behavior. Four-fifths of the animals, he + says, were deeply moved, yes, delighted, even, ("charmés." One + interpreter[91] calls it a case of hypnosis!). This emotional + excitement was expressed--somewhat unaesthetically--by the dropping + of excrementa. Guénon characterizes the feeling-state of these + animals as being a mixture of pleasure and astonishment, of + satisfaction and excitement ("mélange de plaisir et d'étonnement, de + satisfaction et de trouble.") He also asserts that the horse's + musical taste is similar to our own. But I can find nothing in his + whole exposition which might prove this. Indeed there is nothing + that could be interpreted as anything other than a purely sensuous + effect upon the horses. I may go a step farther and say that thus + far the sense of music, i. e., understanding of melody, harmony and + rhythm, has not been shown to exist in any animal. Some animals may, + however, be susceptible to the sensuous pleasantness of the tones + themselves.] + +I shall now turn to peculiarities of character, highly humanized, which +have been attributed to Hans. His "sympathies" and "antipathies", +so-called, were nothing but erroneous appellations for the success or +failure on the part of the respective individuals to elicit responses. +He who could procure answers frequently, apparently stood high in the +horse's favor. That Hans shook his head violently when asked by Mr. von +Osten: "Do you like Mr. Stumpf?", and answered in the affirmative the +further question: "Do you like Mr. Busch?", was nothing but a +confession--unwilling, to be sure--on the part of the master himself. In +the first case the master thought "no", in the second instance, "yes", +and the two thoughts were accompanied by the corresponding head +movements, to which Hans responded mechanically. Hans appeared to be +well-disposed toward me, but evidently because I always rewarded him +liberally when he answered correctly, and I did not scold him when his +responses were wrong, as did Mr. von Osten and Mr. Schillings, who +instead of seeking the cause within themselves, were always ready to +rebuke Hans for his contrariety and fickleness. The horse did not show, +in so far as can be judged at all, any real affection for his master. On +the other hand it would be unwarranted to say that, in spite of all +rewards, he developed a grudge against all those who bothered him with +instruction and examination. Shortly after the close of our +experimentation it happened that Hans severely injured his groom by a +blow in the face. Yet this man had always been very gentle with the +horse and had been forbidden by Mr. von Osten to make Hans solve any +problems for him. Experts assure me that we have here to deal, not with +a case of "moral insanity", but with a very common experience,--although +this view will probably be cavilled at by enthusiastic lovers of horses. +The work of so excellent an expert as Fillis,[92] for instance, bears us +out in this respect. + +The horse's supposed fickleness was nothing but a token of the fact that +even those who were accustomed to working with him, did not have him +completely in hand. (They simply did not understand how to obtain +correct responses from the horse.) It often happened that in the +evening, when it had become so dark that the movements of Mr. von Osten +could no longer be seen, Hans had to suffer bitter reproaches because he +made so many errors. That, in truth, he never was stubborn and that the +cause of failure really lay in the questioner, is shown by the fact that +the mood, for which he was reproved, would disappear the moment the +questioner voluntarily controlled the signals. We may add that there was +no basis for the assumption that "he had an uncommon, finely constituted +nervous system" or was possessed of a "high degree of nervousness". Both +these phrases were often mentioned by way of explanation. Hans was +restive, as horses usually are. And besides, he lived a life so secluded +(he was never allowed to leave the courtyard) that as a result he was +easily disturbed by strange sights and sounds. There was not the +slightest trace of the clinical symptoms of neurasthenia--on the +contrary he gave the impression of perfect health,--which was curious +enough when we remember his rather unnatural mode of life. + +Hans's stubbornness was a myth. He was suspected of it whenever the same +error occurred a number of times in succession, i. e., when the +questioner did not properly regulate his attention (page 146) or when he +was being controlled by "perseverative tendency", mentioned on page 149. +Mr. Schillings, who has provided me with material here as elsewhere, +relates the following episode which occurred on one such occasion. To +one and the same question put alternately by Mr. von Osten and Mr. +Schillings, Hans responded correctly, with two taps, to the former, and +just as persistently incorrectly, with three taps, to the latter. After +Mr. Schillings had suffered this to occur three times he accosted the +horse peremptorily: "And now are you going to answer correctly?". +Hereupon Hans promptly shook his head, to the great merriment of all +those present. (Mr. Schillings had, with no accounted reason, expected a +"no".) Hans was called willful whenever the same question was +successively answered by different responses, as frequently happened +with the increasing tension that characterized the high numbers (page +145). He was also regarded as stubborn when no reply at all was +forthcoming, as in the tests with the blinders. + +Hans's supposed distrust of the questioner, when the latter did not know +the answer to the problem, is nothing but a poor attempt to account for +the failure of those tests. Hans's distrust of the correctness of his +own responses was supposed to be evident from his tendency to begin to +tap once more if, after the completion of a task, the questioner did not +immediately give expression to some form of approval or +disapproval--just as a schoolboy begins to doubt his answer if the +teacher remains silent for a short time. In terms of the results of our +experimentation this would mean that whenever the questioner did not +resume the erect posture, after Hans had given the final tap with the +left foot, then the horse would immediately begin once more to tap with +the other foot (page 61). + +As the evil characteristics, so, too, the good. Thus, his precipitancy, +which was supposedly evidenced by his beginning to tap before the +questioner had enunciated the question, was nothing but a reflection of +the questioner's own precipitancy in bending forward (page 57). Never +did Hans evince the slightest trace of spontaneity. He never spelled, of +his own accord, anything like "Hans is hungry," for instance. He was +rather like a machine that must be started and kept going by a certain +amount of fuel (in the form of bread and carrots). The desire for food +did not have to be operative in every case. The tapping might ensue +mechanically as a matter of habit--for horses are to a large extent +creatures of habit. This lack of spontaneity could hardly be reconciled +with the horse's reputation for cleverness. It would not be necessary to +touch upon the signs that were supposed to betoken genius: the +intelligent eye, the high forehead, the carriage of the head, which +clearly showed that "a real thought process was going on inside",--all +these, we said, would not need mentioning, if they had not been taken +seriously by sober-minded folk. If there is a report that Hans turned +appreciatively toward visitors who made some remark in praise of his +accomplishments,--it is evidence only of the observer's imaginativeness. + +Turning from a consideration of the horse to that of the persons +experimenting with him,[AH] the first and most important question that +arises is this: How was it possible that so many persons (there were +about forty) were able to receive responses from the horse, and many of +them on the very first occasion? The answer is not hard to find. All of +these persons came to the horse in very much the same frame of +mind--which found a similar expression in all, in both posture and +movements. And it was these motor expressions of the questioner (aside +from the signs for "yes" and "no", which I believe I have adequately +explained on page 98), that the horse needed as stimuli for his +activity. + + [Footnote AH: I cannot enter upon a discussion of the latest + psychological problems, here involved, partly because that would + take us beyond the purpose of this monograph, and partly because + they are still moot questions and hence not suited to popular + treatment. Briefly though, they are these: What is the nature of the + relationship between cognitive and affective states on the one hand + and involuntary, (so-called expressive) movements on the other? Is + this connection an external thing, as it were, an association + arising as a habit formation, or does every idea partake essentially + of a motor character? Do purely cognitive states give rise to such + movements, or does the movement impulse depend more particularly + upon the affective consciousness accompanying the cognitive states? + And in how far do given kinds of expressive movements depend upon + certain ideational types (c.f. page 95)? Thus, what is the + influence of the visual image upon the gestures for "up," "down," + etc.? And then, are these involuntary movements, when not noted, + truly unconscious, or merely not attended to,----in other words, are + they beyond the pale of consciousness or merely "at the fringe?" The + various writers speak almost without exception of unconscious + movements in the strict sense of the term. My own introspections, + however, have led me to doubt whether they are quite unconscious. + Since I have attained some practice I am able to describe in detail + (under conditions of objective control) my involuntary movements, no + matter how slight, even down to mere muscular tensions. None of my + subjects, however, has as yet succeeded in this. It is no very easy + matter to be on the lookout for some unknown movements which might + eventually occur, while attempting to concentrate attention to the + utmost upon a certain definite ideational content, for this very + dividing of attention effects a decrease in the force of the + movement, and thus makes it all the more difficult to discover. From + my own experience, however, I am inclined to believe that these + movements are not unconscious, but merely unattended to, in other + words, we have a narrowing down of the apperceived content within + certain limits, but not a narrowing down of consciousness, (much + less a "splitting" of consciousness or of personality as the thing + unfortunately has sometimes been called). In order, however, not to + be guilty of premature judgment, I have avoided the terms + "unconscious" and "unattended to," and chose expressions which leave + these finer distinctions untouched.] + +The next question that arises is: why did only a few persons receive +responses regularly from Hans, whereas the greater number were favored +only occasionally? What was the selective principle involved? The answer +is, that the successful person had to belong to a certain type, which +embodied the following essential characteristics. + +1. A certain measure of ability and tact in dealing with the horse. As +in the case of dealing with wild animals, such as the lion, etc., Hans +must not be made uneasy by timidity in the questioner, but must be +approached with an air of quiet authority. + +2. The power of intense concentration, whether in expectation of a +certain sensory impression (the final tap), or in fixing attention upon +some idea-content ("yes", "no", etc.). It is only when expectancy and +volition are very forceful, that a sufficient release of tension can +ensue. This release of tension is accompanied by a change in innervation +and results in a perceptible movement. And it was only when the thought +of "yes", or "up", etc., was very vivid, that the nervous energy would +spread to the motor areas and thence to the efferent fibers, and thus +result in the head-movement of the questioner. From infancy we are +trained to keep all of our voluntary muscles under a certain measure of +control. During the state of concentration just described, this control +is relaxed, and our whole musculature becomes the instrument for the +play of non-voluntary impulses. The stronger the customary control, the +stronger must the stimuli be which can overcome it. The steady +unremitting fixation, which resulted in the horse's selection of the +cloths, also involves a high degree of concentration. + +3. Facility of motor discharge. Great concentration was necessary of +course, but not sufficient. Persons in whom the flow of nervous energy +tended to drain off over the nerves leading to the glands and the +vascular system might betray great tension, not so much by movements as +by a flow of perspiration (we have many excellent examples of this given +by Manouvrier)[93] or by a violent beating of the heart, blushing and +the like,--in short, by secretory and vasomotor effects. Or it is not +inconceivable that long dealing with very abstract thoughts might have +weakened the tendency of overflow to other parts of the brain, and that +therefore the entire discharge is used up in those portions of the brain +which are the basis of the intellectual processes. But if expressive +movements occur, the motor pathways must be particularly unresisting in +order to take up the overflow of psychophysic energy. This is the +necessary condition for obtaining the tapping and the head movements on +the part of the horse, although for the tapping there is still one other +circumstance necessary: viz., + +4. The power to distribute tension economically--i. e., the ability to +sustain it long enough, and to release it at the right moment (after the +manner of the curves described on page 93), and to control properly the +unavoidable variations which will occur.[AI] + + [Footnote AI: The mental state just described is probably + essentially the same as that of the spiritualistic "mediums" when + they are occupied with table-rapping and table-moving. In both cases + concentration is very intense,----in other words, the field of + attention is limited. We saw that this state not only favors the + tendency toward involuntary movement, but on account of the + absorption of the individual's attention by a certain limited + content, the person will be unaware of the voluntary movements as + they occur. And we are not necessarily here dealing with + neurasthenic, hysteric, or other diseased nervous conditions. In the + case of table-rapping there are movements of the hands, in our case + there are those of the head. Our head, balanced as it is upon the + cervical vertebral column, is continually in a state of unstable + equilibrium and therefore peculiarly susceptible to + movement-impulses of every kind. But I could induce not only + movements of the head, but also of the arms and legs, and this by + having the subject assume a posture which enabled him to hold arms + or legs in as unstable a position as possible. He might stretch out + his legs horizontally before him, or he could raise them vertically + upward as in the hand-stand in gymnastic work. An extract from a + treatise by Count A. de Gasparin,[94] which appeared about the + middle of the last century, may serve to show how close the + correspondence between the two processes, that of getting the table + to rap and that of causing Hans to respond, really is. The report of + this writer, based upon the detailed record of his tests in + table-moving and table-rapping, closely parallels in many minute + details the observations which were made in the course of our + experimentation with Hans. The case is all the more remarkable when + we bear in mind that this writer did not seek the cause of the + phenomena, as we did, in involuntary movements, but thrusting aside + this explanation, he posited the cause in the agency of some + mysterious fluid. It may not be amiss to say that this as well as + most other references were consulted after the present experiments + and introspections had been completed. Of the page references + preceding the following citations, the first always refers to the + page in the French original, and the other, enclosed in brackets, to + the parallel passage in the present monograph. + + P. 49 [31]. Some questioners are especially suitable + ("experimentateurs hors ligne"), but in their absence, other persons + may also operate successfully ("le succès, quoique moins brillant + alors, n'est pas impossible.") + + P. 25 [229]. But even the most suitable questioners do not always + succeed equally well ("les plus sûrs d'eux-mêmes ne réussissaient + pas également tous les jours.") + + P. 42 [151]. When the questioner is in any way indisposed, the + measure of success is also less. + + P. 91 & 87 [150]. The Questioner must first get into the sweep of + things ("en train"), and once he has done so, all interruption + whatsoever must be avoided. + + P. 91 [93]. Unless there is sufficient tension on the part of the + questioner, the test will fail. ("La volonté est-elle absente, rien + ne bouge.") + + P. 210 [93]. When there is too low a degree of tension, then too + great a number will be tapped ("si votre volonté ne les [les tables] + arrête pas au moment où se termine le chiffre pensé, elles + continueront indéfiniment.") + + P. 31 [93]. But too great concentration of attention will also + produce failure ("s'il n'arrivait ... de désirer trop fortement le + succès et de m'impatienter en cas de retard, je n'avais plus aucune + action sur la table.") + + P. 36 [151]. If the proper mood ("entrain habituel") is wanting and + the tests are unsuccessful, it is best not to attempt some new and + difficult experiment, but to turn to some that are simpler and more + entertaining ("La table obéissait mal; les coups étaient frappés + mollement et comme à regret.... Alors nous avons pris un parti dont + nous nous sommes bien trouvés; nous avons persévéré, et persévéré + gaiement; ... nous avons écarté la pensée des tentatives nouvelles, + et insisté sur les opérations aisées et amusantes. Après un certain + temps les dispositions étaient changées, la table bondissait et + attendait à peine nos commandements.") + + P. 199 [41, 90]. It is not necessary to enunciate the questions + aloud ("On est convenu que celui qui commanderait ne prononcerait + pas à haute voix le nombre de coups, mais se contenterait de les + penser, après les avoir communiqués à l'oreille de son voisin. Eh + bien! la table a obéi. Il n'y a jamais eu la moindre erreur.") + + P. 199 [64 ff.]. The large numbers are tapped more rapidly than the + small ones ("la table a indiqué notre âge tel qu'il était dans notre + esprit, se hâtant même de la manière la plus comique lorsque le + nombre des coups à frapper était un peu considérable.") + + P. 210 [35 ff.]. Tests in which "procedure was without knowledge" + failed completely ("Les tables ne révèlent pas ce qui n'est pas dans + la pensée et dans la volonté de l'expérimentateur; quand on veut les + charger d'autre chose que d'obéir comme des membres, on arrive à des + erreurs continuelles.") + + P. 28, 29, 217 [72]. When of two experimenters each tries to get the + horse to tap a different number, then that one who is the better + able to compel the animal's attention, will be the successful one. + ("L'un veut faire prévaloire un chiffre pensé plus considérable, + l'autre un chiffre pensé moins considérable.... Eh bien: l'opérateur + le plus puissant l'emporte." "Ainsi A est chargé secrètement de + faire frapper 25 coups, B est chargé secrètement de l'arrêter à 18; + A l'emporte, et les 25 coups s'achèvent.... On fait maintenant + l'inverse: B est chargé secrètement de faire frapper 13 coups; A est + chargé secrètement de l'arrêter à 7; A l'emporte encore et le + chiffre 7 ne peut être dépassé.")] + +The experience of a number of practical men, who have had much to do +with horses and yet achieved but very modest success with Hans, goes to +show that it is not always the lack of sufficient authoritativeness, +mentioned under heading 1 that is the sole cause of failure, as has been +claimed so often. That the horse was, to a certain degree, influenced by +this element of authority is shown, however, by the following incident. +A certain gentleman, when alone in the courtyard with Hans, received +responses only so long as I (concealed in the barn) kept the barn-door +open just a little, so that my presence could be known to the horse. As +soon as I closed the door, Hans refused to respond to the gentleman. +Those who possessed sufficient power of concentration and the requisite +motor tendency--the two characteristics mentioned under 1 and 2 +above,--were able to obtain responses from the horse without any +previous practice. Practice merely effected a more economic distribution +of attention, so that the larger numbers especially were more successful +as a result (pages 68 and 89). Those who were lacking in either of the +characteristics mentioned under 2 and 3 would not be aided even by the +greatest amount of practice, as is shown by the case mentioned in +Supplement III (page 255).--That many individuals were at first +successful but were later unable to get any successful responses, is to +be accounted for by the fact that the power of concentration, at first +present, later rapidly disappeared. This temporary increase in the power +of doing mental work was first investigated experimentally by Rivers and +Kraepelin,[95] and was called by them "Antrieb" and aptly likened to the +first pull of a team of horses in starting off. This, too, explains an +experience which befell a number of the horse's visitors, who later +described it to me. Wishing to utilize a momentary absence of Mr. von +Osten, they excitedly put a hasty question to Hans, and with amazing +regularity received correct responses.--Besides Mr. von Osten, Mr. +Schillings and myself, not many were always able to induce Hans to bring +the colored cloths or to execute the head movements. It was easy, on the +other hand, to get him to nod. Therefore there was some truth in Mr. von +Osten's assertion, that Hans would be unable to answer a difficult +question if he had not previously indicated by means of a nod that he +had grasped its import. Those who were not concentrating sufficiently, +would not look into Hans's face, when he was expected to nod, and would +not bend over, when Hans ought to begin tapping--such persons could not, +therefore, since they did not induce Hans to nod, elicit the tapping. I, +myself saw the "no" successfully elicited only in the case of Mr. von +Osten, Mr. Schillings and Mr. Hahn; the "right" and "left" only in the +case of the former two. It must remain uncertain whether this failure on +the part of otherwise suitable persons to elicit the responses for +"right" and "left" was due to their accompanying these ideas by +movements of the eyes instead of by movements of the head, (page 106). +For unfortunately it was not possible to make special tests to discover +whether Hans reacted to isolated eye movements. There is, however, more +than one reason why I would doubt this. Taken all in all, there were but +few persons who were entirely representative of the type described (c. +f. page 31)--they were those who are commonly characterized as being of +a lively temperament and strongly impulsive. Thus Hans acquired a +reputation for "Einkennigkeit", that is, he would accustom himself only +to certain persons. Such a reputation was hard to reconcile with his +much praised intelligence. + +In closing, just a word on the influence of the public that was present. +As was shown on page 69, the public in general did not influence the +horse in his reactions. The effect upon the questioner, however, was +unmistakable, and worked in a twofold manner. On the one hand the +questioner's zeal was increased and with it the tension of +concentration. On the other hand, it introduced an element of diversion, +and attention was divided between the horse and the spectators, and thus +concentration suffered. If the disturbing effect was slight, as in the +case of Mr. von Osten, then the favorable influence exercised by the +presence of the public outweighed the unfavorable. Mr. von Osten was, +for that reason, often particularly successful when working in the +presence of a large body of spectators. This was noted by many and was +ascribed to the ambition of the horse. When, however, a person was +easily diverted, as was Mr. Schillings, then the presence of the public +had a less fortunate effect. + +This, then, completes my explanation of the facts gleaned from +observation and experimentation. It accomplishes all, I hope, that may +be expected of an explanation. All the known achievements of the horse, +all the successes and failures of the questioner, have been reduced to a +single principle; no secondary hypothesis has been invoked, and but +slight place has been given to the element of chance. Nevertheless, it +may not be out of place to forestall two objections which might possibly +be raised. First, some may assert that it was through our +experimentation that the horse became mechanized and incapacitated as +regards conceptual thinking; that formerly he really could solve +arithmetical problems, and only later developed the very bad habit of +depending upon the signs which I gave him. This objection is to be +refuted in that I did not originate these signs, but first noted them in +Mr. von Osten, himself, and in that Hans still works as faithfully as +ever for Mr. von Osten. I have learned from many trustworthy witnesses +that the horse still continues to give brilliant exhibitions of his +"ability". If, on the other hand, anyone should assert that it was only +with us that Hans reacted to movements, but that with his master he +really thought and still thinks, then I must ask for proof. This latter +argument is by no means very original. When Faraday in 1853 proved +experimentally that "table-rapping" is the result of involuntary +movements on the part of the participants standing about the table, the +spiritualists asserted that his experiments had nothing in common with +their own proceedings, because his subjects (who by the way, had been up +to that time firm believers in table-rapping) probably did move the +table, they said, while they (the spiritualists) do no such thing.[96] + + + + +CHAPTER VI + +GENESIS OF THE REACTION OF THE HORSE + + +In the preceding discussion we have regarded the achievements of the +horse as well as Mr. von Osten's explanation of them, as matters of +fact. Let us now consider the question: How did the horse come by these +achievements, and how did its master arrive at his curious theory in +explanation of them? Did he indeed seek to instill in the horse's mind +the rudiments of human culture through long years of painstaking +instruction in accordance with the method described in Supplement I +(page 245)? If that is the case, then, of course his hoped-for success +was only seeming, not real. Or did he, as so many critics aver, +systematically train the horse to respond automatically to certain cues, +and propound his theory merely for the purpose of misleading the public? +There might possibly be another alternative, viz.: was there a mixture +of instruction and of training to respond to cues? + +The production of the horse's achievements would not require a great +deal of explanation, if it were a case of mere training for the purpose +of establishing certain responses to certain cues. It might be +desirable, however, before deciding in favor of one of these +possibilities, to indicate briefly the process of development, as it +might occur, if the point of view is taken that _bona fide_ instruction +was given. + +This development would probably be as follows:--Mr. von Osten, as the +result of theoretical speculation or of a misinterpretation of the facts +of experience, having arrived at the conclusion that the horse possessed +extraordinary capacity, finally undertook to instruct a certain horse +for a period covering three years. This one having died, he, nothing +daunted, undertook the education of another one. What it was that +influenced this old teacher of mathematics to deprive humankind of the +benefit of his extraordinary pedagogical ability and love of teaching, +we do not know. It may be that he had had bitter experience in that +line, or again, mayhap the newness and tremendousness of this other task +stimulated him. His first problem must have been to arouse the interest +of the animal in this process of education. It was hardly to be believed +that Hans would eagerly coöperate in a process which promised to yield +him no immediate benefit. The teacher sought to overcome this lack of +immediate interest by the means of rewards. To Hans the sweet carrot was +as toothsome a bite as candy is to the child. And since the horse was +furthermore kept on low rations on account of the relatively low amount +of physical exercise he took, the anticipation of the carrots was doubly +enticing. + +The first thing that Mr. von Osten sought to teach the horse, according +to his own statement, was the significance of the names of colors and of +the spatial directions such as "up", "down", etc. In the case of +children there is a simple test by means of which we may discover if +they have put any content into these words. The test is: Do they, +themselves, use them correctly? Do they call the blue, blue, and the +red, red? Since the horse could not speak, his instructor had to give +him some means by which he could make himself understood. He taught +Hans to approach the colors and select the cloth of the color wanted. He +also taught him to make those movements of the head or body which +correspond with the expressions: "up", "down", etc. + +First of all, Hans had to be taught to bring the cloths. Then began the +pointing out of the different colors, accompanied each time by their +proper names. It is very probable that at first Hans had to be led each +time to each separate colored cloth and taught to raise it or to touch +it with his nose. Later, Mr. von Osten, after having pronounced the name +of the color, remained at his place, with his head and body directed to +the cloth in question and gazing intently at it, in order to see whether +or not the horse was pointing out the right one. Naturally Hans would, +at first, fail a hundred times where he would succeed but once, but +since the horse would receive the anticipated reward in case of success, +he gradually became conscious that this reward was attached to +executions which had some special mark. This special mark would be +expressed in human speech by the statement that the horse would go in +the direction indicated by the position of the instructor's body. For +Hans, of course, this would not take the form of an abstract statement, +but simply of a definite way of seeing and of going and a correlation of +the two in a certain definite manner,--the whole being a process, the +elements of which remained unanalyzed and unaccounted for by Hans. Owing +to the position of the eye, it was possible for him to keep his master +within his field of vision, while he was approaching the cloths. And +only when he had correlated his approach in a certain definite manner +with his visual perception of the master, i. e., only when he had felt +his way, as it were, along the latter's line of vision, did he receive +his reward. A sufficient number of repetitions was all that was +necessary to establish an association in the psychological sense of the +term. In the same manner, dogs will learn, as was indicated on page 177, +to bring an object upon which the master has fixed his gaze, it +mattering little whether or not the name of the object be enunciated. +There is only this difference, that, in the case of the dog it is not +possible to keep the image of the master within the field of vision; but +neither is it necessary, for he has recognized the object before he has +started for it. We must remember, however, that it does not simplify an +attempt at explanation to assume that Mr. von Osten consciously trained +the animal to respond to certain bodily positions of the questioner. +For, even in this case, it would be necessary to explain how it was +possible for him to train the horse to heed the cues.--In the course of +time, the instructor may have noticed that whenever he moved during the +course of a test the horse invariably failed. But he may have regarded +this merely as an incidental distraction and afterward was careful to +remain quiet. As soon as he increased the number of cloths upon the +floor, it was no longer possible for him to give the horse such accurate +directive signs, and the number of errors consequently increased. +Ascribing them to the inattentiveness of his pupil, he sought to +encourage him by such calls as "look out", "look there", "see there", +believing that, thus, he was directing the horse's attention to the +desired color. Without understanding the meaning of the calls, Hans +learned, however, to keep moving just as long as the calling continued, +for if he did this he was regularly rewarded. An association was +established between the call and the impulse to move on. And with these +two associations established, Hans gave the impression of having grasped +the meaning of the color terms. + +The origin of the proper movements in response to the terms "up" and +"down" may be explained by the fact that the movements themselves were +practised in a purely external fashion. Thus, whenever the word "left" +was pronounced, the horse's head was pulled to the left by means of the +bridle or the reward was held off to that side. Later, Mr. von Osten, +who looked expectantly at the horse's head, whenever he pronounced the +word would unconsciously move his own head in the direction in which he +desired the horse to turn. This is quite in accord with the words of +Darwin to the effect that whenever we wish an object to move in a +certain direction it is well-nigh impossible for us to inhibit an +unconscious, involuntary movement in that direction. Proof for this may +be found on all sides, in daily experience.[97] Imagine, for instance, +the strain sensations of the bowler or billiard player as he follows the +moving ball. It is impossible to decide whether Mr. von Osten, +consciously continued to image the head movements which he expected the +horse to make or whether these anticipatory images later remained below +the threshold as was always the case with Mr. Schillings and myself (see +page 100). But this question is of little significance, for even +assuming that he always thought of the movement he expected on the part +of the horse, this by no means implies that he was conscious of the +movements on his part, which were associated with the thought process. + +Everything up to this point might be explained as the working of simple +memory association, but when we come to problems in counting and +arithmetical calculation, we are in the field of conceptual thought. +Here, again, it was necessary for Mr. von Osten to invent a suitable +means of expression for the horse, and once more this had to be borrowed +from the treasury of gesture-language. Tapping with the hoof was +naturally hit upon as one of the normal, expressive movements of the +horse. This has long been used by trainers, in preparing horses for show +purposes. The method used in training the horse to make this response is +of no import, whether it was by touching his foot with the hand, or +tapping his leg, or by any other means. + +It is possible that many will declare, as being nonsensical, any attempt +to introduce number-concepts[AJ] into an animal's mind, because the +necessary motor basis is lacking. We will not, just at this point, stop +to discuss whether or not it was not possible to develop number-concepts +from purely auditory or visual representations. It is evident, however, +that Mr. von Osten believed that a motor basis of some sort was +essential. In the case of man this basis is found in the enunciation of +the number names (or in the manipulation of the fingers). Mr. von Osten +seemed to think that he was justified in assuming that, even in the case +of the horse, some form of inner articulation of the word-sounds was +possible;--at the same time, in so doing, he did not blink at the +psychological difficulty of this hypothesis. The tapping of the foot was +to be regarded merely as the expression of the process of inner +counting, but not as the motor basis of the process. For this latter +purpose tapping would be quite inadequate, for the number complexes +which arise in the summation process of counting, could not be +differentiated by mere tapping with the foot, any more than a child +could learn to count by employing only one finger. Mr. von Osten +evidently imagined the process was somewhat like this: Whenever Hans was +about to count 5, he would enunciate inwardly the numbers from 1 to 5, +and would accompany each word with a tap of the foot. Since, +furthermore, wooden pins and balls could be used--as in the case of +children--for giving visual content in learning the significance of the +number-terms, it seemed as if all the conditions necessary for the +formation of number-concepts were supplied. However, the most essential +thing had to be presupposed, viz.: that the horse virtually possessed +the general power of forming concepts,[AK] and that all that had been +lacking was the suitable conditions for its development. Mr. von Osten +held tenaciously to this conviction, and it was this conviction that was +the basis for the infinite patience with which the tests had been +pursued. + + [Footnote AJ: The author intends to take up the problem of counting, + so-called, on the part of animals and of the principle involved, in + another work soon to be forthcoming.] + + [Footnote AK: There are some who believe they are warranted in + concluding the opposite from the structure of the animal's brain + alone. We may say that the brain of the horse, compared with that of + the ape, or even that of the dog, represents a relatively low type + of development. But owing to the rapid changes in the views, often + contradictory, concerning the nature of the nervous structures and + processes underlying the thought process, any conclusion based on + such views would be premature. For this reason we cannot agree with + the French physiologist who was dissecting the brain of a horse and, + struck by its smallness of size, exclaimed: "When I saw your proud + look and beautiful neck, I hesitated a moment before mounting upon + your back. But now that I have seen how small is your brain, I no + longer have any qualm about using you."[98]] + +To come now to the learning process itself;--we may assume that, at +first, whenever the horse began to tap in response to commands, he would +receive a reward for this purely mechanical feat. Wooden pins were then +planted on the ground and designated as: one, one two, etc., and each +time someone would raise the horse's foot as many times as the count +demanded (see Supplement I). Then Mr. von Osten would take his stand at +the horse's side and would command him, let us say, to tap 3. Hans +noting merely (from his master's position) that he was expected to tap, +would begin. The instructor, who had bent forward in order to watch the +horse tapping,[AL] would involuntarily straighten up again at the third +tap, without being conscious of it and quite unaware that he was thus +giving a signal. The horse would be startled, and sometimes he would +immediately cease tapping and sometimes not. But it was only in the +first case that he would receive a reward. Thus, unknown to the +instructor, an association became established between the sight of the +upward jerk of the instructor and the act of ceasing to tap. To be sure, +the animal would receive sundry visual impressions from the wooden pins +set up before him and the auditory stimulations of the spoken number +names, on the basis of which, the concepts were to be formed in his +mind. But in this chaos of visual impressions (at times there were two +wooden pins, then three, then four, sometimes there were the pins, at +others, the balls of the counting-machine)--and in the babel of +word-sounds--which evidently meant nothing but noise to him--amidst all +this there was but one constant element: the final movement of the +instructor's body. The moment the horse reacted to this, he would +receive the tidbit at the hands of his overjoyed master, and thus he +became more and more accustomed to attend to this jerk, even after it +had gradually decreased in scope. And the reason again, why this jerk +tended to become less pronounced was that the tests were gradually +becoming more and more successful. For, corresponding to the degree in +which the horse began to react properly, the instructor's tenseness and +excitement tended to decrease, and with this decrease of the emotional +element in the man's consciousness, the accompanying non-voluntary, +expressive movement gradually became less pronounced until it attained +that extraordinary refinement which it possesses to-day. We noticed +also, that whenever the horse, for any reason, had to be trained anew, +Mr. von Osten's movements would, on the whole, become somewhat more +gross, as for instance after the tests with the blinders. There is not a +shadow of a doubt that this increase in the movement's extent was +entirely unintentional, since the horse could not see his master at all +on account of the blinders which had been attached to the trappings. + + [Footnote AL: This natural and close connection between the process + of attention and the movement toward the object attended to is + clearly expressed in our English and French terms, derived from the + Latin "tendere ad--," to reach toward--.] + +In the same way it is possible to explain the details. Mr. von Osten +himself said that at first Hans had tapped at times with his left foot, +at times with his right, just as he pleased. But later his master taught +him to tap only with the right. Whenever he began with the left, Mr. von +Osten would immediately interrupt him, and he was allowed to add only a +final tap with his left foot. Thus, this additional tap which was +sometimes made with the left foot was but the vestige of an earlier +rudimentary habit. The signal for it was the stooping posture in which +the master remained after the head-jerk had been made. Whenever Mr. von +Osten had given Hans a small number to tap, he would bend forward only a +little. But when he expected a larger number he would bend forward +somewhat more, owing to the desire to observe the tapping more +carefully. From the slight inclination of the master's body the horse +would get the cue that he was expected to tap for a short time only, by +the greater degree of inclination he would know that he was to tap for a +longer period. In the second case he tapped rapidly and did not raise +his foot as high from the ground--evincing a regard for the saving of +energy, which may well be attributed to a horse. And thus arose the +connection between the degree of inclination of the instructor's body +and the horse's rate of tapping. + +So, now that the ability to count and solve problems had become +fixed--as the old gentleman thought--he began to instruct the horse in +other branches. Since everything had been translated into terms which +were to be expressed by means of tapping with the foot, and thus really +put into terms of number--which was perhaps natural for an old teacher +of mathematics--the same mechanism was involved in these accomplishments +as in those of counting, etc. Mr. von Osten saw the animal's +intelligence steadily increase, without having the slightest notion that +between his words and the responsive movements of the horse, there were +interpolated his own unconscious movements--and that thus instead of the +much desired intellectual feats on the part of the horse, there was +merely a motor reaction to a purely sensory stimulus. It has been a +common custom of man to posit some extraneous cause for movements +resulting from certain involuntary motions of his own, of which he is +not aware, (witness the divining-rod).[AM] And furthermore, when these +results appear to be rational, the tendency is to seek their cause in +some extraneous intelligence, not his own. Just as the spiritualists +ascribe the "messages" which are revealed to them through table-rapping, +to certain rational spirits, so Mr. von Osten credited the intelligence +of the horse with the result produced by his own involuntary signs--i. +e., with the proper solution of problems. + + [Footnote AM: G. Franzius,[99] privy counselor of the admiralty, + master of the dry-dock at Kiel, is responsible for the undeserved + revival of the ancient belief, long buried by science, that the + divining branch is put into motion solely as the result of the + influence of hidden springs or treasures, and without any agency in + the person who is holding it. The untenability of this theory comes + home to us most forcibly when we recall how various are the kinds of + things which have been discovered by means of the branch. First + there is gold and water, which are the only ones mentioned by Mr. + Franzius. The water can be thus discovered only when it flows below + ground, say that which is passing through the mains of a city, + whereas the water of the Rhine or the Elbe would have no effect on + the branch. Besides gold, every other kind of metal has been + supposedly located by the branch,--as well as coal, gypsum, ochre, + red-chalk sulphur and petroleum,--according to the desire of the one + searching. Thus, the very same branch that just a moment ago was + influenced by the least bit of underground water, may remain + unaffected by the presence of a large body of water, if in the + meantime I have changed my plan and decide to search for coal or for + gold. But that is not all. The branch will point out a murderer or + the place where a murder has been committed, it will discover the + thief or his trail, as well as the things stolen or merely touched + by him. It will indicate where the boundary-stone that has been + moved, ought to stand. The branch further discloses the sins of the + persons concerning whom it is consulted, as well as their talents + and abilities, the journeys they have made and the wounds they have + received. It will indicate whether or not a person has money and how + much. It can announce what absent persons are doing and what apparel + they are wearing, and of what color it is. It will give information + on theological, medical, zoological, and botanical questions. In + fine, no matter what the question, it will never fail of an + answer.[100, 101] + + The impossibility of explaining the phenomena in a purely physical + way was recognized at a very early date. For a long time the + activity of the users of the divining rod seems to have been + restricted to the search for metals. The first (or one of the first) + to raise his voice against it was the learned G. Agricola[102] + (1556), and after him there were many who all wrote more or less + independently of one another. Aside from swindle and chance, it was + usually believed that sorcery of the agency of Beelzebub was + involved, and for that reason the Church has repeatedly forbidden + the use of the divining-rod. But even in the 17th century we find + some who believed that it was imagination alone that moved the + person's hand, and with it the rod,[103, 104] ("fortassis etiam + phantasia manum in motum concitante"); and that points out the + essentials of the solution of the phenomenon, and we will not go + into the matter here in detail. A number of complex psychological + problems arising in connection with it are still waiting to be + solved, but this much appears certain; the staff or branch plays no + other part in the whole process than that which is served by the + three levers in the tests described in Chapter IV (pages 116 + ff.),--they simply magnify the expressive movements of the diviner. + And so we can understand why the instruments serving as rod might be + so varied. Hay-forks, pickets, clock-springs and pendulums, scissors + and pliers have been used. A knife and fork or two pipes, fastened + together, an open book, and even a sausage, grasped at both ends and + thus bent together somewhat,--all have served the purpose equally + well. We can understand, too, how some adepts are able to achieve + the same degree of success--for they do succeed beyond a + doubt--without any rod whatever, but simply by placing the index + fingers end to end and bending them somewhat, and even by merely + groping about with hands outstretched or folded before them.[106]] + +Two other phenomena may have tended to strengthen Mr. von Osten's belief +in Hans's intelligence. One was the misleading similarity with which the +horse's supposed errors in computation and the poorly adjusted +concentration of the questioner, were expressed. We recall the +difficulty in the case of very high numbers. This might easily be +considered as being due to the horse's ability to work more readily with +small, rather than with large numbers, whereas, as a matter of fact, it +was due solely to the difficulty of the questioner to keep his attention +concentrated upon the number for so long a time. We recall also the +frequency of errors of one unit too few and one unit too many. These +were easily interpreted as miscounts on the part of Hans, but in truth +were the result of the poorly concentrated attention of the questioner. +Added to this was the seeming independence and self-sufficiency of the +horse. Often the number given by him was other than that desired by his +master. Usually Hans was in the wrong in such cases, but sometimes, too, +he was right. At any rate, this served to give the impression of +independence of thought which his master so thoroughly believed he +possessed, and which was the goal of his endeavors--though as a matter +of fact he was farther removed than ever from that goal. + +Some may ask: Does not this whole process partake of the essentials of +all training, (though cumbersome and misunderstood, to be sure), and is +there any need of investigating whether or not the actual development +was of the sort here outlined, or whether it actually took the course +common to all training? + +In order to answer this question we must determine more specifically +what we mean by the term "training". Usually we take it to mean the +establishment in the animal, of definite habits of motor reaction in +response to certain stimuli purposely selected by the trainer, and +without involving any process of animal consciousness other than +association. Such a conception may be applied also to man, if we assume +that the higher thought processes can be eliminated. If that were the +case, the above definition would not have to be changed, not even with +regard to the word "animal", for we must take it in the antique sense of +"zoon", a signification readopted by modern zoology. The concept may be +widened, however, by omitting the differentia of "purpose", or even +more, by including the habitual association of ideas or images (instead +of movements) with certain sensory stimuli. But in so doing, we must +bear in mind that we are going beyond the usual content which in +everyday practice is put into the term "training". Especially, when we +cease to regard the presence of purpose in the trainer's mind (both in +giving the stimulus as well as in the habituation of the animal to them) +as essential. When this is done, the conception of training really +resolves itself into the much wider conception of habit-building, and +the whole discussion becomes merely a quarrel over words. In order to +obviate this, let us bear in mind that in the following, the word +"training" is always taken in the usual and narrower sense. The term +then is still ambiguous only in so far as it has not merely its original +significance of the _act_ of purposely habituating (a person or an +animal) to perform certain definite movements, but by transference is +also used to denote the _effect_, i. e., the occurrence of the movements +in question. But this does not really detract from the clearness of the +concept itself. + +Having cleared up the question of definition, let us return to our +original problem: Does the hypothetical account of the probable +development of the horse's reactions, which is given on pages 213 to +220, represent a case of training? This must be denied decidedly with +regard to the tapping of numbers and the solution of arithmetical +problems. For here the sensory stimuli which were purposely given, i. +e., the wooden pins, the balls, and the spoken words, were intended to +subserve the function of arousing not movement, but thought processes in +the horse; whereas the function of the horse's movements was to give +expression to these thought processes. Of the really effective +stimuli--the slight movements on his part--the master was never +conscious, much less were they purposely made. The same holds true for +the "up" and "down", "yes" and "no", etc., for here also Mr. von Osten +counted upon the rise of the corresponding concepts, and not merely upon +a purely external, mechanical association of meaningless sounds with +certain movement-responses on the part of the horse. This might also +explain the genesis of Mr. von Osten's belief that Hans was able +mentally to put himself in the place of the questioner, (page 19). At +any rate it is very improbable that he, Mr. von Osten himself, clearly +distinguished between the concept: "up" and the sound of the word "up". +When we come to consider the horse's selection of the colored cloths, +and even more his leaping and rearing, we find that the distinction +between "training" and "instruction" vanishes. If we had to deal only +with this class of achievements, we might perhaps say, without fear of +going very far wrong, that the only difference between this and the +ordinary form of training was that Mr. von Osten had intended to train +the horse to respond to auditory signs (words), but had unintentionally +trained him to respond to visual signs instead. But it is not this type +of performance that has become the bone of contention. Just as it would +be misleading to maintain that Mr. von Osten's effort was nothing other +than a case of training, so it also would be unjustifiable to designate +the results of his effort by that name, since the really effective +stimuli were not, as has been pointed out just now, given intentionally. + +As far as the horse is concerned, it is a matter of indifference whether +or not really effective stimuli were given intentionally by the +questioner. The animal knows nothing of human purposes and if he were +transferred to a circus, he would find nothing new in the method +employed there, except the use of the whip. We, however, define our +concepts from the human and not from the horse's point of view. We may +definitely say, therefore, that the method described cannot be regarded +as that of training, neither in its application nor in the effect +produced, though in the latter it closely simulates the effects of the +training method. + +Having thus differentiated between the methods of instruction and +training, let us now attempt to decide on the basis of such indications +as we may possess, which of the two was actually represented by the +development of the horse's attainments. Surveying the facts which we +have at hand, we may say that there are hosts of reasons why we cannot +assume that it was a case of training. Everything that we know from our +own observation and from the well-attested statements of others, with +regard to the actual process of instruction, weighs against the +assumption. Another evidence of this is the long period of time which +Mr. von Osten required (both in the case of Hans, as well as with his +predecessor), whereas the same end would have been much more speedily +attained if it had been a case of training. A further argument is the +fact that a large horse was selected for the purpose, whereas a small +mare would have been far more suitable, (c. f., "Clever Rosa", page 7). +Again, the whip, that sorcerer's rod of all professional trainers, was +here absent. And finally, many traits of character of Mr. von Osten, as +well as his conduct during the whole course of events, militate against +such an assumption. He generously turned the horse over to us, as he had +given it over to Count zu Castell, Count Matuschka and Mr. Schillings. +He eagerly besought a scientific investigation. He had made several +reports to different ministries. All of these acts could only hasten the +denouément. What could have been his motive? Some thought they detected +an effort at pecuniary speculation, and an advertisement of June, 1902, +in the "Militärwochenblatt", in which Hans was offered for sale, seemed +to confirm the conjecture. Mr. von Osten says that this occurred at a +time when he himself was sick and had become tired of the job. And why +should he not be willing to sell even a thinking horse, since he had +become convinced that any other could be instructed in the same way? +Besides, I have it on good authority that after the publication of the +September report he received several exorbitant offers; to mention only +one of them: a local vaudeville company was ready to pay him 30,000 to +60,000 marks per month. He refused every one of these offers. Some may +say that perhaps he wanted still more. But if he knew that the day of +judgment was close at hand, he also knew that before then, if ever, was +the sunshiny day on which to make his hay. A more auspicious time he +could never hope to see again.--Let us add, once more, that he never +charged admission to any of Hans's performances, although there were +many who were anxious to see the horse, and many enthusiasts had come +from a great distance. And finally, he was an old man, unmarried and +entirely alone, a property owner, but a man whose wants were few and +very simple--and his Hans was almost his sole companion. Is it possible +that such a man, one who had all the pride of gentle birth, would become +a trickster in his old age, all for the love of money? + +The unreliability of Mr. von Osten's signs is good proof of their +involuntary nature. Anyone who had seen him work with the horse could +not have helped noticing that he certainly did not have complete control +over the animal, and was not able, at a given moment, to make Hans +perform a certain feat, as would have been the case if the process had +been one of "training". Again and again Hans failed to make the right +count. Before a large audience, one time, it took four tests to get him +to tap properly up to 20, and in all four I could note clearly that it +was Mr. von Osten who, by his involuntary premature movements, was the +innocent cause of the failure. On another occasion, after Hans had done +some beautiful work in fractions, in the presence of a large number of +spectators, the master asked him the simple question: "Where is the +numerator in a fraction?"--The answer was first: "to the left", and +then, after a severe reprimand: "down" (below), and finally: "up" +(above). He often made just such incorrect movements of the head. In the +color-selecting tests the average of error was quite unpredictable. With +an equal number of tests, on one day, half would be successful, on +another, four fifths, on a third, one-tenth. Often Hans appeared to be +"indisposed" for days at a time. The color tests would often end in +expressions of rage on the part of Mr. von Osten and in consequence Hans +would become startled and would then storm about the courtyard so that +it was dangerous to try to approach him. Some may object that all this +was mere comedy and that possibly Mr. von Osten prevented some of the +tests from turning out successfully. But this objection is to be met by +the statement that very often failure would occur just when it was +particularly desirable to have the tests appear in a favorable light +before a large and enthusiastic assemblage of visitors. After such +failures he would be downcast on account of Hans's contrariness. It is +also significant that Mr. von Osten's percentage of error, corresponds +very closely with my percentage of error in the "non-voluntary" tests, +(page 84f.), whereas he never was able to obtain the errorless results +which I obtained in my "voluntary" experiments. + +But we must be careful not to confuse non-voluntary movement and lack of +knowledge of the movement. And again we must distinguish between +knowledge of the grosser and the finer signals. Mr. von Osten was aware +of the grosser movements, and talked quite freely concerning them, but +in so doing, showed that he was quite unaware of their true function. He +undertook to show us what we already knew--that, when he remained +standing perfectly erect, he could elicit no sort of response from Hans. +Furthermore, that whenever he continued to bend forward, Hans would +always respond incorrectly and with very high numbers. He knew, also, +that Hans was distracted in his operations every time the questioner +resumed the erect posture while the tapping was in progress. This he +demonstrated to us on one occasion in the following manner. He said to +Hans: "You are to count to 7; I will stand erect at 5". He repeated the +test five times, and each time Hans stopped tapping when the master +raised his body. Several such tests resulted in the same way. Mr. von +Osten, however, believed this to be a caprice of the horse and at first +declared that he would yet be able to eliminate it, but later became +resigned to it as an irremediable evil. Mr. von Osten was also aware +that the questioner ought not move while the horse was approaching a +colored cloth, and cautioned me in regard to it, though I had already +noted as much. And finally, he also knew what influence his calls had +while the horse was selecting the cloth, and he told me that it was of +great assistance to Hans to be admonished frequently, since thus his +attention was brought to bear upon the proper cloth. Yet, when we +requested Mr. von Osten to desist calling, since he was thereby +influencing the horse in the choice of the cloth, he answered: "Why +that's just what I wish to do!"--But though the statement that he was +aware of the nature of these grosser signs is thus seen to be true, it +by no means necessarily implies that he had purposely trained the animal +to respond to them. In these observations of his he had builded better +than he knew--he evidently had no notion of their scientific +significance. But the same thing might happen to those who were supposed +to be somewhat less naïve, as is shown by the experience of Mr. +Schillings, who quite unconsciously, for many months had been giving not +only the finer, but also the grosser signs, and never guessed the true +nature of affairs until I explained it to him. Nor was it an easy matter +for me to get at the facts involved in the process, although it now all +appears so very simple. + +On the other hand, it is also true that Mr. von Osten knew nothing +whatever of the finer, more minute signals, such as the final jerk, the +head-movement upward, downward, etc., and it is difficult to conceive +how he might have gained any knowledge of them. We might perhaps +conceive of four possible sources. He might have come upon them by +chance. But it is extremely improbable that in the million of possible +forms of signaling he should have hit upon those that at the same time +represent the natural expressive movements. Or he might have derived a +knowledge of them through a study of the pertinent literature. I have +searched diligently for such a source, in both the old and the modern +literature, but in vain. From the sixteenth century on, there is a +series of accounts of horses that were able to spell and to solve +problems in arithmetic, and the reports on learned dogs go back even to +the time of Justinian, in the middle of the sixth century.[107] All of +these animals were kept for purpose of speculation and were exhibited +for pecuniary reasons only. Nor does one read that any person could work +with these animals off-hand, which was the characteristic feature of the +Osten horse.[AN] In many cases we find mention made of the signs to +which the animals reacted. Thus for the beginning or stopping of the +animal's scraping or tapping, the signals were respectively raising and +lowering of the eyes on the part of the trainer,[113] lowering and +raising of the whip[114] or of the arm, stepping forward and +backward,[115] and as a closing signal a slight bending forward.[116] +The signals for beginning and ceasing to bark in the case of dogs, were +the trainer's commands to "speak", and, at the same time, his looking at +the dog, and then looking away for a closing sign;[117] or a +mouth-movement on the part of the trainer and then a withdrawing of the +left hand which had been resting on the hip.[118] Among the signals for +nodding and shaking the head we find the following mentioned: raising +and lowering the hand or arm[119] or the whip;[120] a movement of the +hand toward the horse's nose, as a signal for nodding, and an +arm-movement as a signal for shaking the head.[121] For this last, we +find recommended also a slight breathing upon the animal,[122] and--in +the case of dogs--a mouth-movement simulating blowing, or a turn of the +fingers.[123] (We will not dwell upon the many signals for selecting +objects, which are mentioned, since we have already discussed this point +on page 230f). In all these instances it is plain that we have to do +with purely voluntary and "artificial" signals. The only example of +involuntary signs which Mr. von Osten could have found in literature, +was that of Huggins's dog, which need not be considered here, since, as +was said on page 177, the really effective signs in that case were not +discovered. A third means by which Mr. von Osten might have gained a +knowledge of the involuntary, natural expressive signs, would have been +by observing others. If he had had opportunity of observing another von +Osten and another Hans, he might have gotten at the secret. But since +this was not the case, this possibility vanishes. A fourth possibility +is self-observation. We would then have to assume that Mr. von Osten at +first really tried to educate the horse to think, but soon recognized +the fruitlessness of such an attempt. At the same time, he then would +have noticed his own involuntary movements and their effect upon the +horse, and having noted them, voluntarily reduced their extent and +utilized them in the training process. But here also there is much that +militates against this assumption when we consider how great is the +difficulty of consciously refining movements which at first were rather +coarse, unless it be by the adjustment of the proper degree of +concentration of attention, a subtlety of method of which we could +hardly believed Mr. von Osten capable. We must remember, also, that in +the first publication regarding Hans which, by the way, marks the +beginning of his career, ("Das lesende und rechnende Pferd," by +Major-General E. Zobel, in the "Weltspiegel" of July 7, 1904), we may +read the following: "He (Mr. von Osten) is always willing to have the +horse undergo an examination on the part of a stranger, and promises +that after Hans has become fairly well acquainted he will display the +same degree of efficiency as he displays with the master, himself." +This occurred at a time when Mr. Schillings, the man who was destined to +prove the truth of the statement, had not yet appeared on the scene. How +was Mr. von Osten to know beforehand that every questioner, who might +appear, would execute the same movements that he himself had used? We +would recall also that not one in the great multitude of persons who +worked successfully with the horse in the absence of Mr. von Osten, had +noticed, even in the slightest measure, any of these movements in +themselves. The position and repute of these persons vouches for their +veracity,--among them were the writer of the article just mentioned, the +Count zu Castell, Count Matuschka, Count von Eickstedt-Peterswaldt, +General Köring, Dr. Sander, Mr. H. Suermondt and Mr. H. von +Tepper-Laski. Some of these gentlemen were quite unwilling to believe +that they executed such movements. This happened in the case of Mr. von +Tepper-Laski, who had visited Hans ten times and who had, during the +course of these visits, frequently worked alone with the horse and had +received correct responses. Count Eickstedt, too, although he was one of +those who had been made acquainted with the nature of the movements +involved before being allowed to visit the horse, was unable to note +them either in his observation of Mr. von Osten, or of himself, when, in +compliance with his own wish, he was left alone with Hans. Nor did any +of the laboratory subjects, some of whom were well trained in +introspection, discover the true nature of affairs. They were thoroughly +astonished when the facts of the case were explained to them. And I, +also, as was mentioned on page 100, did not become aware of my own +movements, until I had noted those of Mr. von Osten. In fine, everything +would indicate that we have here not an intention to deceive the +public, but a case of pure self-deception.[AO] + + [Footnote AN: There is only one, and I believe it is only a seeming + exception to be found in the literature on the subject. We are told + that about the year 1840 a French revenue official named Léonard had + two hunting dogs that, besides other things, were able to play at + dominoes, and this not only with their master, but with anyone and + without the master's assistance. The owner had educated them simply + for the fun of it, and not for pecuniary gain. This statement is + made by both writers who, apparently independently of one another, + have discussed the case, Youatt[108] and de Tarade.[109] De Tarade + himself played with them, and gives directions how to teach dogs to + play the game. But his exposition is so naïve, and even ridiculous, + for those who know anything about the subject, that we do not + believe it necessary to attempt a detailed refutation. Youatt never + saw the animals. But he tells us that not only the dog's partner, + but also the master, sat at the game. Youatt's assertion, however, + that "not the slightest intimation could have been given by Mr. + Leonard to the dog," but that the animal carried on the game by + means of its own observation and calculation, appears to me a rather + bold statement. After my own experience with dogs, I firmly believe + this to have been impossible. Hachet-Souplet,[110] who shares my + conviction, explains the matter as follows: the dog would simply + place a domino having the number of eyes named by his partner, thus + the 6 adjacent to the 6, the 3 to the 3, etc. But even so a great + deal would have to be attributed to the dog, (although in that case + real counting would by no means be absolutely necessary, for an + association between the number term and the total picture of the + corresponding group of eyes would suffice.) But we must note that + neither of the writers mentions that the numbers were always called + aloud by the partner. After the failure of the experiments of Sir + John Lubbock,[111] we must doubt very much if a dog is able to match + one domino with another having the same number of eyes. We are + therefore inclined to believe that this dog continually received + signs from its master. These signs probably were visual, perhaps + also auditory, and they were by no means involuntary. For in a book + on the training of animals, which Léonard, the owner of the dogs, + has published, and in which he describes minutely the method by + which they had been trained in their various accomplishments, he + does not mention with so much as a syllable the game of dominoes, a + thing which he certainly would have dwelt upon, if he had believed + in the animals' power of independent thought. He would not have + remained silent concerning this greatest--though only + apparent--achievement of his educational endeavors. But his whole + book is evidence that he was too wise to have thus deceived himself, + and our only alternative is to believe that he was playing a joke on + his credulous admirers.] + + [Footnote AO: P. Wasmann, S. J. in the third edition of his book, + "Instinkt und Intelligenz im Tierreich" (Freiburg, Herder, 1905), + discusses the case of Hans and quotes from a letter I wrote him + concerning the matter. In the quotation an error has crept in, which + I would here correct. The statement is ascribed to me that "Hans + differs from other horses only in his extraordinary power of + observation, an unintentional by-product of intentional training," + whereas in my letter I said: "unintentional by-product of + intentional education."] + +This self-deception is easily understood when we consider the two +predominent characteristics of the man: the pedantry of the pedagogue, +and his proneness to be possessed by a single idea, which is a +peculiarity of those of an inventive turn of mind. Adhering closely to a +preformed plan, he carefully and narrowly circumscribed the scope and +order of instruction. He would not go on to the number 5 if he were not +thoroughly convinced that the 4 had been completely mastered, nor would +he go on to a more difficult problem in multiplication, until he felt +certain that Hans was entirely proficient in the problems of the simpler +sort. If he had ever put a question to Hans before its regular order, he +would have discovered, to his amazement, that there really existed no +difficulties for Hans, and also that the horse really required no +appreciable time to acquire new material. Mr. von Osten would have had a +like experience if he had asked Hans concerning the value of Chinese +coins or the logarithm of 1000. However, he never did anything of the +kind, but always adhered closely to his plan. He required the questioner +to say: "2 and 2", and never "2 plus 2". Nor were capitals or Latin +script to be used in the written material. And if upon request he did +so, he did it, without faith in the result, and hence there was +failure. And so he declared that "if you use Latin script Hans becomes +confused and will be out of sorts for several weeks thereafter." Mr. von +Osten is, and ever will remain, the schoolmaster, and will never become +the psychologist, the "soul-vivisectionist". Who would work a child with +such puzzling questions? and Hans was to him like a child. Thus the old +man believed himself to be a witness of a continuous, organic +development of the animal soul--a development which in reality had no +other existence than in his own imagination. + +Added to this pedantry was an extraordinary uncritical attitude of mind, +induced by his obsession by one favorite idea, which blinded him to all +objections. He met objectionable observations on the part of others in +one of two ways. One method was by attributing to Hans certain +remarkable qualities, such as an extraordinary keenness of hearing and a +wonderful power of memory, or again, certain defects, such as moodiness +and stubbornness,--which as a matter of fact, were only so many +back-doors by which he might escape from the necessity of offering +adequate explanations. When Hans was able to give off-hand a gentleman's +name which he had heard years before, it was called a case of +extraordinary memory. When the horse insisted that 2 times 2 was 5, he +maintained that it was an example of animal stubbornness. There was +still a simpler method of overcoming inconvenient objections and that +was by ignoring them altogether. The number 1, the simplest and most +fundamental in the system of numbers, was one of the most difficult for +Hans. (Page 67f.). Mr. von Osten was aware of this, but thought little +of it. During the very first visit of Professor Stumpf, Mr. von Osten +asked the horse: "By how much must you increase the numerator of the +fraction 7/8, in order to get a whole number?" Hans repeatedly answered +incorrectly and always tapped numbers that were too great. The same +question was then asked concerning the fraction 5/8, and immediately +there was a correct response, (the favorite number 3). Mr. von Osten +said very naïvely: "In the case of the difference of 1, he always goes +wrong. It was just what I expected." Mr. von Osten still relates that +the distinction between right and left created far greater difficulty +for Hans than all of the work in fractions, and that even to-day it is +not thoroughly established; also, that the selection of colored cloths +is often a failure still, although it was one of the first things in +which he was given instruction. It appears never to have dawned upon Mr. +von Osten that the arts in which Hans seemed to excel, also formed the +standing repertoire of so many trained horses, regarding whom it was +well-known that they owed all of their cleverness to the training given +them by their masters. This fact alone should have induced him to make +some form of critical investigation. + +When Hans suddenly became a celebrity, and he, himself, the object of an +enthusiastic following, the whole affair evidently took Mr. von Osten +off his feet. Strangers took the further instruction of the horse in +charge, and the rate and degree of Hans's progress became disconcerting. +One day it came to pass that the horse even understood French, and the +old gentleman, whose apostolic exterior had always exerted a high degree +of suggestion upon his admirers, in turn fell captive to the spell of +retroactive mass-suggestion. He no longer was uneasy concerning the most +glaring kinds of failure. On one occasion he even insisted upon the +completion of a series of tests in which procedure was "without +knowledge", which promised no results whatever. "The animal's +stubbornness must be broken," he commented. On the other hand, he +regarded every criticism as a form of personal insult. And once he +showed a member of the committee of the Society for the Protection of +Animals the door, because the man, without having looked at his watch, +wanted to show it to Hans and ask him the time. Many other critics had +similar experiences. + +Summarizing the remarks of this chapter, our judgment must be as +follows: It is in the highest degree improbable that Mr. von Osten +purposely trained the horse to respond to certain cues. It is also +improbable that he knew that in every test he was giving signals, +(although I can form no judgment concerning what happened after the +publication of the latest report). To assume the contrary would land us +in the midst of insoluble contradictions of the many ascertained facts +in the case. The explanation here essayed, however, should prevent that. +To be sure, we, must then reckon with curious inner contradictions in +Mr. von Osten's character. But such contradictions are to be found, upon +earnest analysis, in nearly every human character. And Mr. von Osten may +say with the poet: "Ich bin kein ausgeklügelt Buch. Ich bin ein Mensch +mit seinem Widerspruch." + + + + +CONCLUSION + + +If we would make a brief summary of the status of Mr. von Osten's horse +in the light of these investigations and try to understand what is the +bearing upon the question of animal psychology in general, we may make +the following statements. + +Hans's accomplishments are founded first upon a one-sided development of +the power of perceiving the slightest movements of the questioner, +secondly upon the intense and continued, but equally one-sided, power of +attention, and lastly upon a rather limited memory, by means of which +the animal is able to associate perceptions of movement with a small +number of movements of its own which have become thoroughly habitual. + +The horse's ability to perceive movements greatly exceeds that of the +average man. This superiority is probably due to a different +constitution of the retina, and perhaps also of the brain. + +Only a diminishingly small number of auditory stimuli are involved. + +All conclusions with regard to the presence of emotional reactions, such +as stubbornness, etc., have been shown to be without warrant. With +regard to the emotional life we are justified in concluding from the +behavior of the horse, that the desire for food is the only effective +spring to action. + +The gradual formation of the associations mentioned above, between the +perception of movement and the movements of the horse himself, is in all +probability not to be regarded as the result of a training-process, but +as an unintentional by-product of an unsuccessful attempt at real +education, which, though in no sense a training-process, still produced +results equivalent to those of such a process. + +All higher psychic processes which find expression in the horse's +behavior, are those of the questioner. His relationship to the horse is +brought about almost wholly by involuntary movements of the most minute +kind. The interrelation existing between ideas having a high degree of +affective coloring and the musculature of the body, (which is brought to +light in this process), is by no means a novel fact for us. +Nevertheless, it is possible that this case may be of no small value, on +account of the great difficulties which are usually met in the attempt +to establish experimentally the more delicate details in this field. + +And, returning to the considerations of the first chapter, if we ask +what contributions does this case make toward a solution of the problem +of animal consciousness, we may state the following: The proof which was +expected by so many, that animals possess the power of thought, was not +furnished by Hans. He has served to weaken, rather than strengthen, the +position of these enthusiasts. But we must generalize this negative +conclusion of ours with care,--for Hans cannot without further +qualification be regarded as normal. Hans is a domesticated animal. It +is possible (though the opposite is usually assumed), that our animals +have suffered in the development of their mental life, as a result of +the process of domestication. To be sure, in some respects they have +become more specialized than their wild kin, (e. g., our hunting dogs), +and in their habits they have become adapted largely to suit our needs. +This latter is shown by all the anecdotes concerning "clever" dogs, +horses, etc. But with the loss of their freedom they have also gradually +been deprived of the urgent need of self-preservation and of the +preservation of their species, and thus lack one of the greatest forces +that make for psychic development. And often their artificial selection +and culture has been with a view to the development of muscle and sinew, +fat and wool, all at the expense of brain development.[AP] Our horses +are, as a rule, sentenced to an especially dull mode of life. Chained in +stalls (and usually dark stalls at that,) during three-fourths of their +lives, and more than any other domestic animal, enslaved for thousands +of years by reins and whip, they have become estranged from their +natural impulses, and owing to continued confinement they may perhaps +have suffered even in their sensory life. A gregarious animal, yet kept +constantly in isolation, intended by nature to range over vast areas, +yet confined to his narrow courtyard, and deprived of opportunity for +sexual activity,--he has been forced by a process of education to +develop along lines quite opposite to his native characteristics. +Nevertheless, I believe that it is very doubtful if it would have been +possible by other methods, even, to call forth in the horse the ability +to think. Presumably, however, it might be possible, under conditions +and with methods of instruction more in accord with the life-needs of +the horse, to awaken in a fuller measure those mental activities which +would be called into play to meet those needs. + + [Footnote AP: Buffon,[124] the great naturalist, expresses himself + not less pessimistically in his own brilliant manner: "Un animal + domestique est un esclave dont on s'amuse, dont on se sert, dont on + abuse, qu'on altère, qu'on dépaïse et que l'on dénature."] + +Though our investigations do not give support to the fantastic accounts +of animal intelligence given by Brehms, they by no means warrant a +return to Descartes and his theory of the animal-machine (as is +advocated by a number of over-critical investigators). We cannot deny +the validity of conclusions from analogy without denying at the same +time the possibility of an animal psychology--indeed of all psychology. +And all such conclusions indicate that the lower forms possess the power +of sense-perception, that they, like us, presumably have at their +disposal certain images, and that their psychic life is to a large +extent also constituted of mere image-associations, and that they too, +learn by experience. Also that they are susceptible to feelings of +pleasure and of pain and also to emotions, as jealousy, fear, etc., +though these may be only of the kind which have a direct relation to +their life-needs. We are in no position to deny _a priori_ the +possibility of traces of conceptual thought in those forms nearest man +in the scale--whether living in their natural manner or under artificial +conditions. And even less so since the final word has not yet been +spoken regarding the nature of conceptual thinking itself. All that is +certain is that nothing of the kind has been proven to occur in the +lower forms, and that as yet not even a suitable method of discovering +its existence has been suggested. But the community of those elementary +processes of mental life which we have mentioned above is in itself +enough to connect the life of the lower forms with ours, and imposes +upon us the duty of regarding them not as objects for exploitation and +mistreatment, but as worthy of rational care and affection. + + + + +SUPPLEMENTS + + + + +SUPPLEMENT I + +MR. VON OSTEN'S METHOD OF INSTRUCTION + +[BY C. STUMPF] + + +The following is a report of the account, which Mr. von Osten gave +Professor Schumann and me, of the method which he had used in the +instruction of the horse, and which was illustrated by actual +demonstrations. I cannot testify, of course, that Mr. von Osten really +did adhere to this method throughout the four years in which he tutored +the horse, but I will say that I have several good reasons for believing +that it was impossible for him to have trumped up this make-believe +scheme afterward, merely to mislead us. Among the reasons are the +following: He was always ready to give a detailed explanation of any +question which we might interpose; the written statements of Major von +Keller, who has known Mr. von Osten for a period of fifteen years; the +testimony of General Zobel, who became acquainted with the whole process +fully a year before any public exhibitions were given; the accounts +given by the tenants in Mr. von Osten's house, who for years saw the +process of instruction going on in the courtyard of the apartment +building,--according to their account his intercourse with the horse +was like that with a child at school,--he made much use of the apparatus +and never did they notice anything like an habituation to respond to +certain signals; and finally the appearance of the apparatus +itself--some of which could not be bought at second hand--was most +convincing. + +The apparatus used for the work in arithmetic consisted mainly of a set +of large wooden pins, a set of smaller ones (such as are to be had in +toy-shops), a counting-machine, such as is commonly used in the schools, +a chart upon which were pasted the numbers from 1 to 100, and finally +the digits, cut large and in brass and suspended from a string. For the +work in reading Mr. von Osten used the chart shown in the frontispiece +of this book. Here we have the letters of the alphabet in small German +script with numbers written below which serve to indicate the row, and +what place in that row, the letters occupy. For tones, a small, child's +organ was used with the diatonic scale C^1 to C^2, and for instruction +in colors, a number of colored cloths were used. + +The work in arithmetic began by placing a single wooden pin in front of +Hans and then commanding him: "Raise the foot!--One!" Here we must +assume that the horse had learned to respond to the command to raise the +foot during the preceding period, when tapping in general had been +taught. In order to get the horse to learn that he was to give only one +tap, Mr. von Osten tried to control the tapping by means of holding the +animal's foot, just as a teacher tries to aid a pupil in learning to +write by guiding his hand. He repeated this exercise so often that +finally the single tap was made. And always the right foot was insisted +upon. Bread and carrots were the constant rewards. + +Two of the pins were now set up and the command given: "Raise the +foot!--One, two!" Mr. von Osten again aided the establishment of the +proper association by using his hand as before. At the same time the two +pins were pointed out, and the order was always without exception from +left to right. Gradually it became unnecessary to touch the foot or to +point to the pins, and instead the question was introduced: "How many +are there?", in order that the horse should become accustomed to these +words as an invitation to give the taps when he saw the wooden pins +before him. + +Then three pins were taken and the words "one, two, three" were spoken, +and so on. In naming a number the preceding ones were always named along +with it, in order that the normal order might thus be learned at the +same time. Later the number alone, without the preceding ones, sufficed +to elicit the proper number of taps. The last word of the series thus +becomes characteristic of the series as a whole. It differs from all the +others, and thus becomes the sign for the whole series of numbers thus +named, each of which arises as a memory image at the proper place in the +series and is accompanied by a tap of the foot. Thus, Mr. von Osten at +any rate had accounted to himself for his success. + +But Hans was not to acquire merely this relatively mechanical process of +counting (hardly to be called counting), but he was to acquire also some +meaning content for the number terms. For this purpose everything +depended upon the concept "and". Only he who can grasp its meaning will +be able to understand a number. 2 is 1 _and_ 1, 3 is 2 _and_ 1. Mr. von +Osten had someone hold a large cloth before the horse, where the wooden +pins usually were placed. He then had the cloth taken up and he would +pronounce emphatically the word "and". After this had been done a number +of times, he put up two of the pins and obscured them by the cloth. The +cloth was again raised and the word "and" pronounced. Then Hans, as a +result of his previous instruction (so Mr. von Osten thought) would give +two taps at sight of the pins. The thing was repeated with three pins, +then with one, and so on, and the horse would always execute the proper +number of taps. + +Now, five pins were set up, the three to the right being covered by the +cloth. The horse tapped twice and Mr. von Osten said "two". Then the +cloth was raised, Hans gave three further taps, and Mr. von Osten said +"and three" with emphasis. + +In this simple manner he tried to get the horse to understand that the +three belongs to the two, and that both together make five. The image of +the five pins as it was known from previous experience, was to be +associated with the combined groups of two and three, and conversely, it +was to be reproduced when these groups were presented. Later the cloth +and pins were omitted and the question was asked: "How much is two and +three?". The horse tapped five times. It had learned how to add. Still +this could be regarded only as a mechanical process, if the horse were +able to add only those numbers which had been presented together one or +more times in the manner just described. And so long as we remained +within the first decade, we could get twenty-five binary combinations +whose sum does not exceed 10 (counting inverted orders we would have +forty-five binary permutations),--all of which might have been practised +separately. But as a matter of fact, Mr. von Osten did not take this +course, for as he himself says, he allowed Hans to discover a great +deal for himself. "Hans had to develop the multiplication table for +himself."--With larger numbers and more addends, the number of +combinations becomes so great that there can be no doubt they were not +practised separately. + +Since, after all this preliminary instruction, Hans really began to give +solutions of new problems, the master believed that this was proof that +he had succeeded in inculcating the inner meaning of the number +concepts, and not merely an external association of memory images with +certain movement responses. But he always remained within the sphere of +the ideas thus developed, and adhered closely to the customary +vocabulary and its usage. Every new concept, each additional word was +explained anew. + +It would not be legitimate to condemn the whole procedure from the very +beginning on the ground of the horse's lack of knowledge of language or +of its use. It was Mr. von Osten's aim to convey to the horse an +understanding of the language, by means of sense-presentations, adequate +to give rise to the proper sense-perceptions. Helen Keller and other +blind deaf-mutes have been educated to an understanding of the language +without the aid of vision and hearing. They have come to it through the +sense of touch alone. Everything depends upon whether or not the +predisposition for it is present. And it was quite rational that Mr. von +Osten should have chosen counting and arithmetical calculation as the +processes by which to make his attack upon the animal mind, for as a +matter of fact, nowhere else is it so easy to bridge the gap between +perception and conception and nowhere else can the sign of success or +failure be perceived so readily as in the handling of numbers. It is +unfortunate, however, that he did not utilize these same signs for +purposes of counter-testing also, as, for instance, by inquiring for the +cube root of 729. But he was prevented from doing this by his close +adherence to his pedagogical principle and by his unquestioning faith in +the soundness of the entire procedure. + +In teaching multiplication the counting machine was used. Two of the ten +balls on one of the rods were pushed far to the left, thus: 00. "How +many are there?" Two taps. "Very well. That is once two." Another group +of two was pushed to the left, at a short interval from the first group, +thus: 00 00. "How many times two balls are there?" was asked, with a +decided movement of the hand toward the two groups. Two taps. "How many, +therefore, are two times two?" Four taps. + +The horse was supposed to learn the meaning of the word "times" by means +of the spatial separation of the groups; he was to be taught to notice +and to count the groups, and also the number of units in a single group. +Three times two then meant three groups with two units in each group. +The horse was supposedly aided by the following factors: the relative +nearness of the units belonging to one group, as over against the space +interval between the groups themselves; also that the groups were +pointed out as wholes in connection with the emphatic enunciation of the +words 'once, twice,' etc.; and finally the touching and raising of the +horse's foot by means of the hand until all the desired associations of +the ideas with one another and with the corresponding tapping movements +were quite perfect. + +Subtraction was taught in the following manner. Five pins were set up; +the horse tapped five times. Mr. von Osten then removed two of them and +said emphatically: "I take away,--minus. How many are still standing?" +The horse tapped three times. Here, too, there was at first some +assistance by means of the hand to get the tapping. + +In division four balls were first pushed to the left end of the rod, +thus: 0000. "How many balls are there to the left?" Four taps. They were +now divided into two pairs, thus: 00 00. Pointing to the units of one +group, the teacher asks: "There are always how many in the group?" Two +taps. Three groups were formed, thus: 00 00 00. "There are now how many +balls to the left?" Six taps. "And there are always how many in each +group?", (pointing at them). Two taps. "And how often is two contained +in six?", (pointing to the groups consecutively). Three taps, etc. + +The ideas of 'part', of 'whole', and of 'being contained' were +illustrated by means of a chalk line which was interrupted in one or +more places by erasure. + +In all these operations Mr. von Osten adhered strictly to the rule, and +required others to do so too, that the number upon which the operation +was performed, must be mentioned first. Thus, one was not to say, "take +3 away from 7", but "from 7 take away 3." Otherwise, he believed, Hans +would become easily confused. Also one was not allowed to say "to +multiply", but to "take" a certain number so many "times". He, himself, +never departed from this practice. + +We will not go into the details of the method by which Hans was taught +the meaning of the number signs, of the signs of operation, of the +numbers above 10, or the significance of "digits", "tens", etc. Only +this,--when in problems in addition the sum was greater than 10, the 10 +was first tapped and then the remainder of the number added to the 10. +Thus: "You are to add 9 and 5. How much must you add to the 9 to have +10?" One tap. "But now, you were to add not merely 1, but 5; how much +have you still to add to the 10?"--Four taps. In like manner, whenever +the addends were below 20 or 30 and the sum above 20 or 30, Mr. von +Osten would ask for the 20 or 30 taps first. He thought that he was thus +giving his pupil an ever firmer grasp upon the principle of the +structure of our number system, in which all higher numbers are +constituted of tens and digits. For the same reason he used at first, +instead of the words 'eleven' and 'twelve' ('elf' and 'zwölf' in the +German), expressions which in English might be rendered as 'one-teen' +and 'two-teen' ('einzehn' and 'zweizehn' in the German); and only later, +after the animal had seemingly mastered the meaning in question, did Mr. +von Osten replace them by the usual forms. + +All this was beautifully conceived and might perhaps form the basis for +the instruction of primitive races. But it is of immediate interest for +us only because it enables us to better understand the origin of the +conviction under which Mr. von Osten and his followers labored. + + + + +SUPPLEMENT II + +THE REPORT OF SEPTEMBER 12, 1904 + + +"The undersigned came together for the purpose of investigating the +question whether or not there is involved in the feats of the horse of +Mr. von Osten anything of the nature of tricks, that is, intentional +influence or aid, on the part of the questioner. After a careful +investigation they are unanimously agreed that such signs are out of the +question under the conditions which were maintained during this +investigation. This decision in no wise takes into account the character +of the men exhibiting the horse, and who are known to most of the +undersigned: In spite of the most attentive observation, nothing in the +way of movements or other forms of expression which might have served as +a sign, could be discovered. In order to obviate involuntary movements +on the part of those present, one series of tests was made with only Mr. +Busch present. Among these tests were some in which, according to his +professional judgment, the possibility of tricks of the sort commonly +used in training, was excluded. Another series of tests was made in such +a way that the correct answers to the questions which Mr. von Osten put +to the horse, were unknown to the questioner. From previous observation +the greater number of the undersigned also know of a large number of +cases in which, during the absence of Mr. von Osten and Mr. Schillings, +other persons were likewise able to obtain correct responses from the +horse. Among these were some cases in which the questioner did not know +the correct solution of the problem or was mistaken about it. And +lastly, several of the undersigned have become acquainted with the +method which Mr. von Osten used, which has little in common with methods +of training, and is patterned after the instruction given in the +elementary schools. As a result of these observations the undersigned +are of the opinion that unintentional signs of the kind which are at +present familiar, are likewise excluded. They are unanimously agreed +that this much is certain: This is a case which appears in principle to +differ from any hitherto discovered, and has nothing in common with +training, in the usual sense of that word, and therefore is worthy of a +serious and incisive investigation. + +BERLIN, September 12, 1904. + + PAUL BUSCH, Circus-manager. + OTTO, COUNT ZU CASTELL-RÜDENHAUSEN. + DR. A. GRABOW, member of the schoolboard, retired. + ROBERT HAHN, Teacher, Municipal schools. + DR. LUDWIG HECK, Director of the Zoölogical Garden. + DR. OSCAR HEINROTH, Assistant in the Berlin Zoölogical Garden. + DR. RICHARD KANDT. + MAJOR F. W. VON KELLER, retired. + MAJOR-GENERAL TH. KÖRING, retired. + DR. MIESSNER, Assistant in the Royal Veterinary College. + PROF. NAGEL, Head of the department of sense-physiology in the + Physiological Institute of the University of Berlin. + PROF. C. STUMPF, Director of the Psychological Institute, Member of + the Academy of Sciences. + HENRY SUERMONDT." + + + + +SUPPLEMENT III + +AN ABSTRACT FROM THE RECORDS OF THE SEPTEMBER-COMMISSION[AQ] + + [Footnote AQ: A few days after the 12th of September I made the + present abstract from the original records of the Commission, which + I have here abbreviated somewhat. (See page 8). Referring once more + to the misunderstanding mentioned on page 3, I would say that the + closing sentence of the report is here re-given literally as it then + appeared. C. St.] + + +The important meetings occurred on the 11th and 12th of September and +both of them extended over four hours. The greatest difficulty was +occasioned by the condition laid down by Mr. von Osten: that we were to +work without him from the very beginning. In a certain sense this +condition had been met once before when Mr. Schillings appeared upon the +scene, a man whose fairness ought to be doubted by none. He came utterly +skeptical, and yet in the course of a week he learned to handle the +horse and received responses regularly. However, since the public had +begun to doubt Mr. Schillings also, another person had to attempt the +rôle of questioner. Count zu Castell tried to do this and practised for +some days before the meetings, but his success--although of no small +moment--was not great enough to be convincing. + +In apprising Mr. von Osten of this fact we caused a veritable +catastrophe. He declared in a most decisive manner that he would have to +insist upon the condition he had imposed, since the public demanded it, +and he could never assist in any tests, until he had been cleared of the +suspicion of having descended to the use of tricks. If it should take +weeks to accustom the horse to a new questioner, there would be no +alternative but to wait that length of time. + +A happy circumstance helped us out of our difficulty. We had chanced in +our discussion to mention the experience of Dr. Miessner, a member of +the commission, who on the day before had gone to witness an exhibition +of the mare "Clever Rosa", and who believed that he had succeeded in +discovering the tricks involved. There was a sudden change in Mr. von +Osten's attitude. He expressed his willingness to undergo the most +stringent examination and agreed to anything in the way of conditions of +control, challenging even the proven ability of Dr. Miessner. "I have +neither whip nor rod, as had the man in the exhibition, and agree to any +precautionary measures you may care to take." + +After he had gone, the commission decided to ask him to have the horse +perform one of the more common, simple, feats. They were going to watch +him very closely. Different members were assigned the task of attending +to different parts of his body (head, eyes, right hand, left hand, etc.) +while Mr. Busch, since he was the most proficient in the detection of +tricks, was to regard the total behavior of the man. + +The exhibitions included the indication of the day of the week by means +of taps, the day just past, the day ahead, its date, arithmetical +problems, and the counting of rings strung upon a rod. Messrs. Grabow +and Hahn interpolated a few tests themselves, in which they did the +questioning. All tests were successful. + +Mr. von Osten withdrew, and in comparison of notes which followed, Mr. +Busch, as well as all the others, declared that they had discovered +nothing of the nature of a visible sign. Mr. Busch said that he had also +kept an eye on the spectators and had noticed nothing there. +Nevertheless, he desired to see Mr. von Osten go through one series with +no one else but himself (Busch) present. + +This was done, and on this occasion a number of tests were made in the +recognition of colored cloths. The horse was required to indicate, by +tapping, the place in the series which the cloth occupied and was then +asked to bring the green or the red, as the case might be, in his mouth. +Furthermore, he was asked to approach that one of the five gentlemen +standing at a distance, whose photograph had been shown him. Then he was +requested to spell the words "Rat" and "Busch" according to the method +which he had been taught. Nearly all of these tests were likewise +successful. + +In the conference which followed, Mr. Busch again declared that he had +noticed no trace of a sign; he maintained that, in the selecting of +colored cloths (especially when they were placed so closely together) +and in the approach toward a person, there was no possibility whatever +that some trick was being used. + +During the session of September 12th, Mr. von Osten agreed to two sets +of experiments. + +1. Another man was to put the question to the horse. Mr. von Osten +himself was to stand, back to back to the questioner and to bend +forward, so that he was effectually hidden from the horse's view, yet +could, by means of occasional calls, make his presence known to the +animal. The assumption was that it would be conducive to success if the +horse knew that the master was present and was awaiting the answer, and +yet at the same time the possibility of receiving a sign was obviated. + +2. Another man in Mr. von Osten's absence was to ask the horse to tap a +certain number. Then the questioner was to leave, and Mr. von Osten, +returning, was to ask the horse to perform some arithmetical process +with the number which was thus unknown to the master. Mr. von Osten said +that he thought that this method was somewhat risky, since the horse +would be aware that he, Mr. von Osten, did not know the number, and +might therefore be in a humor to play some prank. + +The questions of the first sort were answered with but very few errors. +Mr. Hahn and Count zu Castell asked simple questions in arithmetic. When +Mr. von Osten withdrew into the stable, the count put several other +problems, among them the counting of persons and of windows, all of +which were solved correctly. + +Between the first and second series of tests the following experiments +were interpolated. The names of six members of the commission were +written upon six slates respectively, which were then suspended from a +string. Mr. von Osten pointed to one of the men and asked: "On which of +the slates is this gentleman's name to be found?" The correct number was +tapped in every case. The command to approach the slate in question was +also obeyed as a rule, although this was not as uniformly successful as +tapping. + +In the conference which followed, Mr. Busch declared that the feats +appeared inconceivable to him; and again none of the men had noted +anything in the way of signs. + +Now followed the second series of tests mentioned above. In order to be +sure to get the correct responses, Mr. Schillings, who up to this point +had not been present at any of the experiments, was asked to put the +questions to the horse. Mr. von Osten went into the house, accompanied +by a member of the commission. And again, Mr. Schillings would go out +before the second part of the test, without having met Mr. von Osten. + +Five tests were made in this way. They were not attended by such amazing +success as were the preceding ones, but nevertheless the results were +surprising. The horse nearly always repeated the number itself, instead +of performing the operation required. Since, however, Mr. Schillings, +owing to a misunderstanding, had, in the first two cases, said to the +horse: "You are to repeat this number for Mr. von Osten", the errors +might appear to be a result of this request. + +At the final discussion, the result of which was the unanimous +declaration which was given for publication, not only the data obtained +during these two sessions, but also the earlier experiences of some of +the members of the commission were taken into consideration. None of the +tests witnessed could be referred to chance or to the use of tricks. +Count zu Castell pointed out that in the course of eight days he had +elicited forty correct responses from the horse, among them some in +regard to which he himself had been momentarily in error. Other members +recalled the many instances in previous exhibitions, during which both +Mr. Schillings and Mr. von Osten were absent, when questions were put to +the horse by others. The commission also had access to a detailed +account written by Professor Stumpf on Mr. von Osten's method of +instruction, based on the explanations and demonstrations which Mr. von +Osten had himself given. As a result of these considerations the +commission felt under obligations to give public expression to its +conviction. In the report it limited itself, however, to the purely +negative side--principally in denying the use of tricks,--and expressed +no opinion with regard to the actual genesis of the horse's +accomplishments, since it believed that there was great possibility that +other factors were involved which ought to be carefully investigated. + + + + +SUPPLEMENT IV + +THE REPORT OF DECEMBER 9TH, 1904 + + +Together with Dr. E. von Hornbostel and Mr. O. Pfungst, I have tried +during the past few weeks to find an explanation of the accomplishments +of the horse 'Hans' by the experimental method. We had access to the +horse in the absence of the master and groom. The results are as +follows: + +The horse failed in his responses whenever the solution of the problem +that was given him was unknown to any of those present. For instance, +when a written number or the objects to be counted were placed before +the horse, but were invisible to everyone else, and especially to the +questioner, he failed to respond properly. Therefore he can neither +count, nor read, nor solve problems in arithmetic. + +The horse failed again whenever he was prevented by means of +sufficiently large blinders from seeing the persons, and especially the +questioner, to whom the solution was known. He therefore required some +sort of visual aid. + +These aids need not, however,--and this is the peculiarly interesting +feature in the case,--be given intentionally. The proof for this is +found in the fact that in the absence of Mr. von Osten the horse gave +correct replies to a large number of persons; and to be more specific, +Mr. Schillings and later Mr. Pfungst, after working with the horse for +a short time, regularly received correct answers, without their being in +any way conscious of having given any kind of signal. + +So far as I can see, the following explanation is the only one that will +comport with these facts. The horse must have learned, in the course of +the long period of problem-solving, to attend ever more closely, while +tapping, to the slight changes in bodily posture with which the master +unconsciously accompanied the steps in his own thought-processes, and to +use these as closing signals. The motive for this direction and +straining of attention was the regular reward in the form of carrots and +bread, which attended it. This unexpected kind of independent activity +and the certainty and precision of the perception of minimal movements +thus attained, are astounding in the highest degree. + +The movements which call forth the horse's reaction, are so extremely +slight in the case of Mr. von Osten, that it is easily comprehensible +how it was possible that they should escape the notice even of practised +observers. Mr. Pfungst, however, whose previous laboratory experience +had made him keen in the perception of visual stimuli of slightest +duration and extent, succeeded in recognizing in Mr. von Osten the +different kinds of movements which were the basis of the various +accomplishments of the horse. Furthermore, he succeeded in controlling +his own movements, (of which he had hitherto been unconscious), in the +presence of the horse, and finally became so proficient that he could +replace these unintentional movements by intentional ones. He can now +call forth at will all the various reactions of the horse by making the +proper kind of voluntary movements, without asking the relevant question +or giving any sort of command. But Mr. Pfungst meets with the same +success when he does not attend to the movements to be made, but rather +focuses, as intently as possible, upon the number desired, since in that +case the necessary movement occurs whether he wills it or not. In the +near future he will give a special detailed report of his observations, +which gives promise of becoming a valuable contribution to the study of +involuntary movements. Also he will give an account of our tests and of +the mechanism of the various accomplishments of the horse. We must also +defer, till then, the disproof of certain seemingly relevant arguments +in favor of the horse's power of independent thought. + +Some defenders of the view which maintains the horse's rationality may +urge that it was only through our experiments that the animal became +trained and spoiled in so far as the ability to think is concerned. They +are refuted in this, however, by the fact that the horse still continues +to solve problems involving decimal fractions and to determine calendar +dates for Mr. von Osten, as brilliantly as ever, as is shown by his +recent demonstration before a large group of spectators. That these +results are now being achieved in a manner essentially different from +formerly is nothing but a bare assertion. + +On the other hand, now that the possibility has been established that +these wonderful results may be obtained in all their complexity by means +of intentional signs, many will question whether Mr. von Osten did not +himself train the horse from the very beginning to respond to these +signs. No one has the right, however, to charge an old man, who has +never had a blemish on his reputation, with having invented a most +refined network of lies, if the facts can be explained in a +satisfactory manner in some other rational way. And this can be done in +this case. For we have seen that there is another alternative, other +than the theory that the horse can think or the assumption that tricks +have been employed. + +And now, aside from the specific results obtained, what is the +scientific and philosophic import of the whole affair?--For one thing, +the revolution in our conception of the animal mind, which had been +hoped for by some, and feared by others, has not taken place. But a +conclusion of an opposite character is justified. If such unexampled +patience and high pedagogical excellence as was daily brought to bear by +Mr. von Osten during the course of four long years, could not bring to +light the slightest trace of conceptual thinking, then the old assertion +of the philosophers that the lower forms are incapable of such thinking, +finds corroboration in the results of these experiments so far as the +animal scale up to and including the ungulates is concerned. For this +reason the tremendous effort put forth by Mr. von Osten, is not, in +spite of the self-deception under which he labors, lost to science. If +anyone has the courage to try the experiment with the dog or the ape, +the insight which we have now gained will enable him to beware of one +source of error which hitherto has not been noticed. + +In the face of much misapprehension which has arisen, I wish once more +to say emphatically that the committee of September 12th in no wise +declared itself to be convinced that the horse had the power of rational +thinking. The committee restricted itself entirely to the question +whether or not tricks were involved, and, intentionally and rightly +referred the positive investigation to a purely scientific court. I +would also report that for some time Mr. Schillings has been convinced, +by his own observations, of the horse's lack of reason, and when he was +apprised of our conclusion in the matter, he embraced it without +wavering. I have no intention of taking part in any discussion which may +arise in the press as a result of the present report. Unless they wish +to confine themselves to mere guesswork, the defenders of other views +will not shrink from the task of basing their criticism upon careful +methodical experimentation, and they will keep a detailed record of +their results day by day; for statements based solely upon memory, +without specific report of experimental conditions, prove nothing. + +PROF. CARL STUMPF. + +December 9th, 1904. + + + + +TABLE OF REFERENCES + + +(The names of the authors of anonymous works are placed in parenthesis.) + +1. ZELL, TH. Das rechnende Pferd. Ein Gutachten über den "Klugen Hans" +auf Grund eigener Beobachtungen. Berlin, R. Dietze, 1904. + +2. FREUND, F. Der "kluge" Hans? Ein Beitrag zur Aufklärung. Berlin, Boll +and Pickardt, 1904. + +3. HANSEN, F. C. C. and A. Lehmann. Über unwillkürliches Flüstern. +Philosophische Studien, edited by W. 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Paris, Typographia Regia, 1693, P. 293. + +90. GUÉNON, A. Influence de la musique sur les animaux et en particulier +sur le cheval. (Châlons-sur-Marne), 1898, pp. 83 ff. + +91. LÉPINAY. L'hypnotisme chez le cheval. Revue de l'hypnotisme, Paris, +1903, Eighteenth Year, No. 5, pp. 152 f. + +92. FILLIS, J. Grundsätze der Dressur und Reitkunst. Translated from the +French by G. Goebel. 3rd Edition, Stuttgart, Schickhardt und Ebner, +1905, pp. 10 f. + +93. MANOUVRIER, L. Mouvements divers et sueur palmaire consécutifs à des +images mentales. Revue philosophique, Paris, 1886, Vol. 22, pp. 204 ff. + +94. GASPARIN, CTE A. DE. Des tables tournantes, du surnaturel en général +et des esprits. 2nd Edition, Paris, E. Dentu, 1855, Vol. 1, Part 1. + +95. RIVERS, W. H. R. and E. KRAEPELIN. Über Ermüdung and Erholung. +Psychologische Arbeiten, edited by E. Kraepelin, Leipsic, 1895, Vol. 1, +pp. 636f. + +96. (CARPENTER, W. B.). Spiritualism and its Recent Converts. Quarterly +Review, London, 1871, Vol. 131, No. 262, p. 312. + +97. DARWIN, CHAS. See 7, p. 48. + +98. SAINT-ANGE, DE. Cours d'hippologie. 2nd Edition, Paris, chez Dumaine +et chez Leneveu and Saumur, chez Mlle. Niverlet et chez Mlle. Dubosse, +1854, Vol. 1, p. 101. + +99. FRANZIUS, G. Die Wünschelrute. Zentralblatt der Bauverwaltung, +Berlin, 1905, Jahrg. 25, No. 74, pp. 461 f. + +100. MÉNESTRIER, CL. FR. La philosophie des images énigmatiques. Lyon, +J. Guerrier, 1694, pp. 483 f. + +101. (LEBRUN, P.). Histoire critique des pratiques superstitieuses, qui +ont séduit les peuples et embarassé les sçavans. Paris (et Amsterdam), +1702, p. 42. + +102. AGRICOLA, G. De re metallica libri XII, eiusdem de animantibus +subterraneis liber. Basel, Froben, 1556, Book 2, pp. 27 f. + +103. SCHOTT, C. Magia universalis naturĉ et artis. Würzburg, J. G. +Schönwetters Erben, 1659, Part 4, Book 4, p. 430. + +104. THE SAME. Physica curiosa, sive mirabilia naturae et artis. +Würzburg, 1662, Part 2, Book 12, p. 1532. + +105. ZEIDLER, J. G. Pantomysterium, oder das Neue vom Jahre in der +Wünschelruthe, etc. Hall in Magdeburg (Halle a. S.), Renger, 1700, +Chap. 2. p. 47. + +106. BARRETT, W. F. On the so-called Divining Rod, or Virgula Divina. +Proceedings of the Society for Psychical Research, London, 1897, Vol. +13, pp. 177 f. + +107. THEOPHANES. Chronographia. Paris, Typographia Regia, 1655, pp. +189 f. + +108. YOUATT, W. The Dog. London, Ch. Knight and Co., 1845, pp. 108 ff. + +109. TARADE, E. DE. Traité de l'élevage et de l'éducation du chien. +Paris, E. Lacroix (1866), pp. 113 ff. + +110. HACHET-SOUPLET, P. Die Dressur der Tiere. Translated from the +French by O. Marschall v. Bieberstein, Leipsic, O. Klemm, 1898, pp. +36 f. + +111. LUBBOCK, SIR J. See 59, pp. 280 f. + +112. LÉONARD, A. Essai sur l'éducation des animaux, le chien pris pour +type. Lille, Leleux, 1842, pp. 81-185. + +113. MEEHAN, J. See 74, p. 602. + +114. FRANCONI (GÄRTNER). Die Dressur der Kunstpferde. Jahrbuch fur +Pferdezucht, Pferdekenntnis, Pferdehandel usw. auf das Jahr 1835, Weimar +und Ilmenau, 1835, Jahrg. 11, p. 329. + +115. LOISET, B. See 71, p. 130. + +116. HACHET-SOUPLET, P. See 110, p. 91. + +117. KNICKENBERG, F. Der Hund und sein "Verstand." Cöthen (Anhalt), P. +Schettlers Erben, 1905, pp. 129 f. + +118. LANG, R. Geheimnisse zur künstlichen Abrichtung der Hunde, revised +edition. Augsburg and Leipsic, A. Bäumer, pp. 46 f. + +119. FRANCONI (GÄRTNER). See 114, pp. 326 f. + +120. TENNECKER, S. V. Erinnerungen aus meinem Leben. Altona, I. F. +Hammerich, 1838, Vol. 1, pp. 21 f. (The name of the author is +erroneously given on the title page as F. v. Tennecker.) + +121. LOISET, B. See 71, p. 132. + +122. D----. Über die Abrichtung der kleinen Kunstpferde zu dem Zählen +mit dem Fusse, Kopfschütteln und dgl. Zeitung für die Pferdezucht, den +Pferdehandel, die Pferdekenntnis usw., Tübingen, 1804, Vol. 4, p. 51. + +123. LANG, R. See 118, pp. 52 f. + +124. BUFFON, CTE DE, et L. DAUBENTON. Histoire naturelle, générale et +particulière. Paris, Imprimerie royale, 1753, Vol. 4, p. 169. + + + + +Angell's Text-book of General Psychology. + +New Edition. By JAMES ROWLAND ANGELL, Professor and Head of the +Department of Psychology in the University of Chicago. Fourth Edition, +Revised and Enlarged. ix+468 pp. 8vo. $1.60. + +The fourth edition contains a large amount of new material, chiefly +empirical in character. To offset this addition, many of the more +strictly theoretical discussions have been condensed. The old material +has been rearranged and many new drawings have been supplied. + +CHARLES H. JUDD, University of Chicago:--I regard it as a most excellent +text. Its clear and thoroly interesting style will, I am sure, make it +very attractive to students. It is complete and compact. Indeed it is a +capital presentation of modern psychology. + + +Seashore's Elementary Experiments in Psychology. + +By CARL EMIL SEASHORE, Head of the Department of Philosophy and +Psychology in the State University of Iowa. ix+281 pp. 12mo. $1.00. + +A supplement to a regular text-book in elementary psychology. It +provides experiments for one laboratory period a week for one semester. + +FRANK DREW, State Normal School, Worcester, Mass.:--The range of +experiments and the simplicity of their presentation are admirable. +They will deepen insight. + + +Jones's Logic, Inductive and Deductive. + +By ADAM L. JONES, Professor in Columbia University. ix+304 pp. 12mo. +$1.00. + +The aim of this text-book is to present, in as concrete a form as is +possible, the rudiments of Logic, considered as method. + + +Jastrow's Psychology of Stereoscopic Vision. + +By JOSEPH JASTROW, Professor in the University of Wisconsin. [_In +press._] + + +Bode's Logic. + +By W. H. BODE, Professor in the University of Illinois. $1.00. + + + HENRY HOLT AND COMPANY + NEW YORK + + + + +LATEST VOLUMES IN THE AMERICAN NATURE SERIES + +(Prospectus of entire Series on request) + + +INSECTS AND DISEASE + +By R. W. DOANE, of Stanford University. Illustrated. $1.50 net; by mail, +$1.62. + +"Describes lucidly and entertainingly, in language that all may +understand, the discoveries in the disease-bearing qualities of insects, +the successful fights that have been made in consequence against yellow +fever, malaria and plague, and the present state of the +investigations."--_New York Sun._ + + +THE CARE OF TREES IN LAWN, STREET, AND PARK + +By B. E. FERNOW, of the University of Toronto. Illustrated. $2.00 net; +by mail, $2.17. + +Written for amateurs by a forester, this volume furnishes information +such as the owner of trees or the "tree warden" may need. + +"Truly admirable ... eminently practical.... 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With colored plates and +many illustrations from photographs. $1.75 net; by mail, $1.87. + +"A delightful miscellany, telling about fish of the strangest kind. +Nearly everything that is entertaining in the fish world is touched upon +and science and fishing are made very readable."--_New York Sun._ + + +INSECT STORIES + +By VERNON L. KELLOGG. Illustrated. $1.50 net; by mail, $1.62. + +"The author is among a few scientific writers of distinction who can +interest the popular mind. No intelligent youth can fail to read it with +delight and profit."--_The Nation._ + + + HENRY HOLT AND COMPANY + PUBLISHERS NEW YORK + + + + +American Science Series + + + Physics. + By A. L. KIMBALL, Professor in Amherst College. + + Physics. + By GEORGE F. BARKER. + + Chemistry. + By IRA REMSEN, President of the Johns Hopkins University. + + Astronomy. + By SIMON NEWCOMB and EDWARD S. HOLDEN. + + Geology. + By THOMAS C. CHAMBERLIN and ROLLIN D. SALISBURY, + Professors in the University of Chicago. + + Physiography. + By ROLLIN D. SALISBURY, Professor in the University of Chicago. + + General Biology. + By WILLIAM T. SEDGWICK, Professor in the Mass. Institute, + and EDMUND B. WILSON, Professor in Columbia University. + + Botany. + By CHARLES E. BESSEY, Professor in the University of Nebraska. + + Zoology. + By A. S. PACKARD, Professor in Brown University. + + The Human Body. + By H. NEWELL MARTIN. + + Psychology. + By WILLIAM JAMES, Professor in Harvard University. + + Ethics. + By JOHN DEWEY, Professor in Columbia University and + JAMES H. TUFTS, Professor in the University of Chicago. + + Political Economy. + By FRANCIS A. WALKER. + + Finance. + By HENRY C. ADAMS, Professor in the University of Michigan. + + +For full descriptions of the Advanced, Briefer, and Elementary Courses +published under each topic, see the publishers' Educational Catalog. + + + HENRY HOLT & CO. + 34 West 33d Street, N. Y. + 378 Wabash Ave., Chicago + + + + +Transcriber's Notes + + +Illustrations have been moved near the relevant section of the text. + +Inconsistent use of spacing has been retained for page numbers followed +by "f" or "ff", and for "i.e." / "i. e.", "e.g." / "e. g.", and +"c.f." / "c. f." Inconsistent use of commas following "i.e.", "e.g.", +and "c.f." has also been retained. Inconsistent use of single and +double quotes around words and the placing of punctuation either +within or external to quotes has been left as-is. Capitalization +inconsistencies and grammatical errors relating to subject/verb +agreement were also retained. + +Inconsistent hyphenation, accents, and use of separate words have been +retained for "any one" / "anyone", "arm movement" / "arm-movement", +"backstep" / "back-step", "blind spot" / "blind-spot", "by the way" / +"by-the-way", "counting machine" / "counting-machine", "divining rod" / +"divining-rod", "ear movements" / "ear-movements", "eye movement(s)" / +"eye-movement(s)", "eyebrows" / "eye-brows", "first rank" / "first-rank", +"four fifths" / "four-fifths", "Hans problem" / "Hans-problem", "head +jerk" / "head-jerk", "head movement(s)" / "head-movement(s)", +"hoped for" / "hoped-for", "memory images" / "memory-images", +"movement impulse" / "movement-impulse", "movement responses" / +"movement-responses", "number concepts" / "number-concepts", "number +terms" / "number-terms", "psychophysical" / "psycho-physical", "some +one" / "someone", "sound waves" / "sound-waves", "thought processes" / +"thought-processes", "tieraugen" / "tier-augen", "time measurements" / +"time-measurements", "training process" / "training-process", "vaudeville +stage" / "vaudeville-stage", "well disposed" / "well-disposed", "well +known" / "well-known", "well trained" / "well-trained" "zoologist" / +"zoölogist", "Zoological" / "Zoölogical". + +There is no direct reference to Table of Reference item 105 or 112 +within this book. + +Here is a list of the minor typographical corrections made: + + - Bracket removed following "1904" on Page vii + - "VI" changed to "IV" on Page vii + - Hyphen added between "September" and "Commission" on Page vii + - "vice versa" italicized on Page 20 + - Double quote added after "'Hans'?" on Page 36 + - "elasping" changed to "elapsing" on Page 50 + - Bracket removed following "utility." on Page 58 + - "Futhermore" changed to "Furthermore" on Page 67 + - "wtih" changed to "with" on Page 77 + - Comma removed after "Problems" on Page 78 + - Comma removed after "errors" on Page 82 + - Comma removed after "errors" on Page 82 + - "reponse" changed to "response" on Page 83 + - Comma changed to period after "one" on Page 83 + - Period added after "Mr" on Page 89 + - Comma added after "continuously" on Page 91 + - "preceive" changed to "perceive" on Page 98 + - Double quote added before "Inhalt" on Page 115 + - "concrn" changed to "concern" on Page 116 + - "of" changed to "is" on Page 122 + - "is" changed to "of" on Page 122 + - Period removed after "I" on Page 127 + - "to to" replaced by "to" on Pages 135 and 136 + - Period added after "50cm" on Page 138 + - Double quote added after "you?" on Page 146 + - Double quote removed after "Perseverationstendenz" on Page 150 + - Comma removed from before "continued" on Page 154 + - "proceesses" changed to "processes" on Page 156 + - em-dash changed to hyphen between "soixante" and "six" on Page 159 + - "baguette")" changed to "baguette)"" on Page 160 + - "role" changed to "rôle" on Page 161 + - "asociate" changed to "associate" on Page 162 + - "taks" changed to "takes" on Page 162 + - em-dash changed to hyphen before "lens" on Page 170 + - Double quote added before "streifenförmige" on Page 173 + - "satisfactury" changed to "satisfactory" on Page 174 + - "thought" changed to "though" on Page 174 + - "explantion" changed to "explanation" on Page 179 + - Comma added after "Another" on Page 188 + - "53" changed to "73" on Page 192 + - Apostrophe changed to comma between "84" and "85" on Page 198 + - "detail" changed to "details" on Page 206 + - "Ostens'" changed to "Osten's" on Page 209 + - "expectpectantly" changed to "expectantly" on Page 216 + - Comma changed to period after "stimuli" on Page 224 + - "suppossed" changed to "supposed" on Page 231 + - Double quote added after "himself" on Page 235 + - "diminshingly" changed to "diminishingly" on Page 240 + - "acounts" changed to "accounts" on Page 243 + - Single quote moved from before "twice," to after it on Page 250 + - Double quote removed from before "How" on Page 251 + - "af" changed to "of" on Page 255 + - Period removed after "found?" on Page 258 + - "Von" changed to "von" on Page 263 + - Period removed after "Stuttgart" on Page 272 + - Comma changed to period after "Botany" on Page 279 + + + + + +End of the Project Gutenberg EBook of Clever Hans, by Oskar Pfungst + +*** END OF THIS PROJECT GUTENBERG EBOOK CLEVER HANS *** + +***** This file should be named 33936-8.txt or 33936-8.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/3/3/9/3/33936/ + +Produced by Audrey Longhurst, Linda Hamilton and the Online +Distributed Proofreading Team at http://www.pgdp.net + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Clever Hans + (The horse of Mr. Von Osten): A contribution to experimental + animal and human psychology + +Author: Oskar Pfungst + +Translator: Carl L. Rahn + +Release Date: October 11, 2010 [EBook #33936] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK CLEVER HANS *** + + + + +Produced by Audrey Longhurst, Linda Hamilton and the Online +Distributed Proofreading Team at http://www.pgdp.net + + + + + + +</pre> + +<span class="pagenum"><a name="Page_ii" id="Page_ii"></a>[Pg ii]</span> +<a name="frontispiece"></a><div class="figcenter" style="width:700px;padding-bottom:2em;padding-top:2em;"> +<img src="images/frontispiece.jpg" border="0" alt="" title="" width="700" height="493"> +<p class="caption">CLEVER HANS</p></div> + + +<span class="pagenum"><a name="Page_iii" id="Page_iii"></a>[Pg iii]</span> +<div class="linearound newpg"> + + +<h1 style="letter-spacing:.2em;word-spacing:.2em;padding-top:1em;">CLEVER HANS</h1> + +<p class="center" style="font-weight:bold;font-size: 1em;padding-top:.2em;">(THE HORSE OF MR. VON OSTEN)</p> +<p class="center" style="font-weight:normal;font-size: 1.25em;padding-top:1em;margin-right:10%;margin-left:10%;"><i>A CONTRIBUTION TO EXPERIMENTAL +<br>ANIMAL AND HUMAN +<br>PSYCHOLOGY</i></p> + +<div class="center" style="padding-top:1.5em;padding-bottom:2em;margin-right:10%;margin-left:10%;"> +<span style="font-weight: bold;font-size: .9em;display:block;padding-bottom:.3em;">BY<br></span> +<span style="font-weight: bold;font-size: 1.4em;">OSKAR PFUNGST</span> +</div> + +<p class="center" style="font-weight:bold;font-size:.9em;padding-top:.5em;margin-right:15%;margin-left:15%;line-height:1.5;">WITH AN INTRODUCTION BY PROF. C. STUMPF, +AND ONE ILLUSTRATION AND FIFTEEN FIGURES</p> + +<div class="center" style="padding-top:1.5em;padding-bottom:.5em;margin-right:10%;margin-left:10%;line-height:1.4;"> +<span style="font-weight: bold;font-size: .7em;display:block;">TRANSLATED FROM THE GERMAN<br></span> +<span style="font-weight: bold;font-size: .7em;">BY<br></span> +<span style="font-weight: bold;font-size: 1em;">CARL L. RAHN<br></span> +<span style="font-weight: normal;font-size: .7em;"><i>Fellow in Psychology in the University of Chicago</i></span> +</div> + +<div class="center" style="padding-top:.5em;padding-bottom:2em;margin-right:10%;margin-left:10%;line-height:1.4;"> +<span style="font-weight: bold;font-size: .7em;display:block;">WITH A PREFATORY NOTE BY<br></span> +<span style="font-weight: bold;font-size: 1em;">JAMES R. ANGELL<br></span> +<span style="font-weight: normal;font-size: .7em;"><i>Professor of Psychology in the University of Chicago</i></span> +</div> +<div class="figcenter" style="padding-top:1.25em;"><img src="images/mark.png" border="0" alt="Publisher's Mark" title="" width="77" height="100"></div> + +<div class="center" style="padding-top:.8em;padding-bottom:2em;margin-right:10%;margin-left:10%;line-height:1.4;"> +<span style="font-weight: bold;font-size: 1em;display:block;">NEW YORK<br></span> +<span style="font-weight: bold;font-size: 1.4em;">HENRY HOLT AND COMPANY<br></span> +<span style="font-weight: bold;font-size: 1em;">1911</span> +</div> +</div> +<span class="pagenum"><a name="Page_iv" id="Page_iv"></a>[Pg iv]</span> + + + +<div class="center newpg" style="padding-top:1.25em;word-spacing:.5em;padding-bottom:.25em;margin-right:10%;margin-left:10%;line-height:1.4;"> +<span class="smcap" style="font-weight: bold;font-size: 1em;display:block;">Copyright, 1911<br></span> +<span style="font-weight: bold;font-size: .75em;display:block;">BY<br></span> +<span style="font-weight: bold;font-size: 1em;">HENRY HOLT AND COMPANY</span> +</div> + + + + +<hr class="newpg" style="width: 65%;"><span class="pagenum"><a name="Page_v" id="Page_v"></a>[Pg v]</span> + +<h2><a name="PREFATORY_NOTE" id="PREFATORY_NOTE"></a>PREFATORY NOTE</h2> +<p class="chapterhead2 smcap">[By James R. Angell]</p> + +<p class="subchapterhead"><i>The University of Chicago</i></p> + +<p><span class="firstwords">It</span> gives me great pleasure to accept the invitation of +the publishers to write a word of introduction for Mr. +Rahn's excellent translation of "Der Kluge Hans", a +book which in the original has been but little known to +American readers. The present wave of interest in animal +life and behavior renders its appearance peculiarly appropriate.</p> + +<p>No more remarkable tale of credulity founded on unconscious +deceit was ever told, and were it offered as +fiction, it would take high rank as a work of imagination. +Being in reality a record of sober fact, it verges on the +miraculous. After reading Mr. Pfungst's story one can +quite understand how sedate and sober Germany was for +months thrown into a turmoil of newspaper debate, which +for intensity and range of feeling finds its only parallel +in a heated political campaign. That the subject of the +controversy was the alleged ability of a trained horse to +solve complex arithmetical problems may excite gaiety +and even derision, until one hears the details. Scientists +and scholars of the highest eminence were drawn into the +conflict, which has not yet wholly subsided, although the +present report must be regarded as quite final in its verdict.</p> +<span class="pagenum"><a name="Page_vi" id="Page_vi"></a>[Pg vi]</span> + + +<p>As for Hans himself, he has become the prototype of a +host of less distinguished imitators representing every +level of animal life, and when last heard from he was still +entertaining mystified audiences by his accomplishments.</p> + +<p>But the permanent worth of the book is not to be found +in its record of popular excitement, interesting as that is. +It is a document of the very first consequence in its revelation +of the workings of the animal mind as disclosed in the +horse. Animal lovers of all kinds, whether scientists or +laymen, will find in it material of greatest value for the +correct apprehension of animal behavior. Moreover, it +affords an illuminating insight into the technique of experimental +psychology in its study both of human and animal +consciousness. Finally, it contains a number of +highly suggestive observations bearing on certain aspects +of telepathy and muscle-reading. All things considered, it +may fairly be said that few scientific books appeal to so +various a range of interests in so vital a way.</p> + +<p>Readers who wish to inform themselves of all the personal +circumstances in the case may best read the text +just as it stands. Those who desire to get at the pith of +the matter without reference to its historical settings, may +be advised to omit the <a href="#INTRODUCTION">Introduction</a> by Professor Stumpf +of the University of Berlin, together with supplements +<a href="#SUPPLEMENT_II">II</a>, <a href="#SUPPLEMENT_III">III</a> and <a href="#SUPPLEMENT_IV">IV</a>.</p> + + + + + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_vii" id="Page_vii"></a>[Pg vii]</span> +<h2><a name="CONTENTS" id="CONTENTS"></a>CONTENTS</h2> + +<table border="0" width="80%" cellpadding="2" cellspacing="2" summary="Contents" align="center"> +<tr> +<td colspan="2" align="left" width="90%"> </td> +<td align="right" style="width: 10%; padding-bottom: 0em;" valign="bottom"> <span class="smaller">PAGE</span></td> +</tr> +<tr valign="top"> +<td colspan="2" align="left" style="width: 90%; padding-bottom: .5em;"><span class="toctext2"><span class="smcap">Prefatory Note</span> (By <span class="smcap">James R. Angell</span>)</span></td> +<td align="right" width="10%"> <a href="#PREFATORY_NOTE">v</a></td> +</tr> +<tr valign="top"> +<td colspan="2" align="left" style="width: 90%; padding-bottom: .5em;"> +<span class="toctext2"><span class="smcap">Introduction</span> (By <span class="smcap">C. Stumpf</span>)</span></td> +<td align="right" width="10%"> <a href="#INTRODUCTION">1</a></td> +</tr> +<tr> +<td colspan="3" align="left" valign="bottom" style="padding-bottom: 0em;"><span class="smaller">CHAPTER</span></td> +</tr> +<tr valign="top"> +<td width="10%" align="left">I. </td> +<td align="left" style="width: 80%; padding-bottom: .5em;"> +<span class="toctext smcap">The Problem of Animal Consciousness and "Clever Hans"</span></td> +<td align="right" width="10%"> <a href="#CHAPTER_I">15</a></td> +</tr> +<tr valign="top"> +<td width="10%" align="left">II. </td> +<td align="left" style="width: 80%; padding-bottom: .5em;"> +<span class="toctext smcap">Experiments and Observations</span></td> +<td align="right" width="10%"> <a href="#CHAPTER_II">30</a></td> +</tr> +<tr valign="top"> +<td width="10%" align="left">III. </td> +<td align="left" style="width: 80%; padding-bottom: .5em;"> +<span class="toctext smcap">The Author's Introspections</span></td> +<td align="right" width="10%"> <a href="#CHAPTER_III">88</a></td> +</tr> +<tr valign="top"> +<td width="10%" align="left">IV. </td> +<td align="left" style="width: 80%; padding-bottom: .5em;"> +<span class="toctext smcap">Laboratory Tests</span></td> +<td align="right" width="10%"> <a href="#CHAPTER_IV">102</a></td> +</tr> +<tr valign="top"> +<td width="10%" align="left">V. </td> +<td align="left" style="width: 80%; padding-bottom: .5em;"> +<span class="toctext smcap">Explanation of the Observations</span></td> +<td align="right" width="10%"> <a href="#CHAPTER_V">141</a></td> +</tr> +<tr valign="top"> +<td width="10%" align="left">VI. </td> +<td align="left" style="width: 80%; padding-bottom: .5em;"> +<span class="toctext smcap">Genesis of the Reaction of the Horse</span></td> +<td align="right" width="10%"> <a href="#CHAPTER_VI">212</a></td> +</tr> + +<tr valign="top"> +<td colspan="2" align="left" style="width: 90%; padding-bottom: .5em;"> +<span class="toctext2 smcap">Conclusion</span></td> +<td align="right" width="10%"> <a href="#CONCLUSION">240</a></td> +</tr> + +<tr valign="top"> +<td colspan="3" align="left" style="padding-bottom: .5em;"><span class="toctext2 smcap">Supplements:</span></td> +</tr> +<tr valign="top"> +<td width="10%" align="left">I. </td> +<td align="left" style="width: 80%; padding-bottom: .5em;"> +<span class="toctext"><span class="smcap">Mr. von Osten's Method of Instruction</span> (By <span class="smcap">C. Stumpf</span>)</span></td> +<td align="right" width="10%"> <a href="#SUPPLEMENT_I">245</a></td> +</tr> +<tr valign="top"> +<td width="10%" align="left">II. </td> +<td align="left" style="width: 80%; padding-bottom: .5em;"> +<span class="toctext"><span class="smcap">The Report of September</span> 12th, <a name="tn_png_6"></a><!--TN: Bracket removed following "1904"-->1904</span></td> +<td align="right" width="10%"> <a href="#SUPPLEMENT_II">253</a></td> +</tr> +<tr valign="top"> +<td width="10%" align="left">III. </td> +<td align="left" style="width: 80%; padding-bottom: .5em;"> +<span class="toctext smcap">An Abstract from the Records of the <a name="tn_png_6b"></a><!--TN: Hyphen added between "September" and "Commission"-->September-Commission</span></td> +<td align="right" width="10%"> <a href="#SUPPLEMENT_III">255</a></td> +</tr> +<tr valign="top"> +<td width="10%" align="left"><a name="tn_png_6a"></a><!--TN: "VI" changed to "IV"-->IV. </td> +<td align="left" style="width: 80%; padding-bottom: .5em;"> +<span class="toctext"><span class="smcap">The Report of December</span> 9th, 1904</span></td> +<td align="right" width="10%"> <a href="#SUPPLEMENT_IV">261</a></td> +</tr> +<tr valign="top"> +<td colspan="2" align="left" style="width: 90%; padding-bottom: .5em;"> +<span class="toctext2 smcap">Table of References</span></td> +<td align="right" width="10%"> <a href="#TABLE_OF_REFERENCES">267</a></td> +</tr> + +</table> + + + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_1" id="Page_1"></a>[Pg 1]</span> +<h2><a name="INTRODUCTION" id="INTRODUCTION"></a>INTRODUCTION</h2> + +<p class="chapterhead2 smcap">[By C. Stumpf]</p> + +<p><span class="firstwords">A horse</span> that solves correctly problems in multiplication +and division by means of tapping. Persons of unimpeachable +honor, who in the master's absence have received +responses, and assure us that in the process they +have not made even the slightest sign. Thousands of +spectators, horse-fanciers, trick-trainers of first rank, +and not one of them during the course of many months' +observations are able to discover any kind of regular +signal.</p> + +<p>That was the riddle. And its solution was found in +the unintentional minimal movements of the horse's questioner.</p> + +<p>Simple though it may seem, the history of the solution +is nevertheless quite complex, and one of the important +incidents in it is the appearance of the zoölogist +and African traveler, Schillings, upon the scene, and +then there is the report of the so-called Hans-Commission +of September 12, 1904. And finally there is the +scientific investigation, the results of which were published +in my report of December 9, 1904.</p> + +<p>After a cursory inspection during the month of +February, I again called upon Mr. von Osten in July, +and asked him to explain to Professor Schumann and +me just what method he had used in instructing the +horse. We hoped in this way to gain a clue to the<span class="pagenum"><a name="Page_2" id="Page_2"></a>[Pg 2]</span> +mechanism of Hans's feats. The most essential parts of +the information thus gleaned are summarized in <a href="#SUPPLEMENT_I">Supplement +I</a>. Mr. Schillings came into the courtyard for +the first time about the middle of July. He came as +skeptical as everyone else. But after he, himself, had +received correct responses, he too became convinced, and +devoted much of his time to exhibiting the horse, and +daily brought new guests. To be perfectly frank, at the +time this seemed to us a disturbing factor in the investigation, +but now we see that his intervention was a link in +the chain of events which finally led to an explanation. +For it was through him that the fact was established beyond +cavil, that the horse was able to respond to strangers +in the master's absence. Heretofore, this had been noted +only in isolated cases. Since it could not be assumed +that a well-known investigator should take it upon himself +to mislead the public by intentionally giving signs, +the case necessarily from that time on appeared in the +eyes of others in a light quite different from that in +which ordinary circus-tricks would appear, to which it +bore such a striking external resemblance. No matter +how this state of affairs may have arisen in the course of +years, no matter how it might eventually be explained,—the +quality of the extraordinary would necessarily attach +itself to this particular case, as it did.</p> + +<p>Of course, to many persons in the interested public +the result was merely that Schillings, also, was placed in +the category of deceivers. On the other hand there were +reputable scientists who could not dispose of the matter in +that fashion, and these now openly took their stand with +Schillings and declared that they believed in the horse's +ability to think. Zoölogists especially, saw in von Osten's +results evidence of the essential similarity between the<span class="pagenum"><a name="Page_3" id="Page_3"></a>[Pg 3]</span> +human and the animal mind, which doctrine has been +coming more and more into favor since the time of +Darwin. Educators were disposed to be convinced, on +account of the clever systematic method of instruction +which had been used and which had not, till then, been +applied in the education of a horse. In addition, there +were many details which, it seemed, could not be explained +in any other way. So far as I myself was concerned, +I was ready to change my views with regard to +the nature of animal consciousness, as soon as a careful +examination would show that nothing else would explain +the facts, except the assumption of the presence of conceptual +thinking. I had thought out the process hypothetically, +i. e., how one might conceive of the rise of +number concepts and arithmetical calculation along the +peculiar lines which had been followed in Hans's education, +and on the basis of the assumption that the beginnings +of conceptual thinking are present in animals. +Also, I had too much faith in human nature to fear lest +nothing peculiarly human should remain after the art +of handling numbers should be shown to be common +property with the lower forms. But under no circumstances +would I have undertaken to make a public statement +in favor of any particular view in this extraordinary +case, before a thorough investigation, in accordance +with scientific principles, had been made. I expressed +this sentiment at the time, and recommended +the appointment of an investigating commission (in the +"Tag" of September 3, 1904).</p> + +<p>The purpose of this commission was misunderstood, +and therefore many were disappointed with the report +which it published, (<a href="#SUPPLEMENT_II">Supplement II</a>). Some had been +expecting a positive conclusive explanation; the commis<span class="pagenum"><a name="Page_4" id="Page_4"></a>[Pg 4]</span>sion +recommended further investigation. Some had +asked for a solution of the question whether or not the +horse was able to think; the commission maintained +neither the one, nor the other. Some had indicated as +the main condition of a satisfactory investigation, that +both Mr. von Osten and Mr. Schillings be excluded from +the tests; this was not done.</p> + +<p>But the commission—which, by the way, did not give +itself this name, since it had been delegated by no one—undoubtedly +had the right to formulate its problem as +it saw fit, and this was carefully expressed at the beginning +of its report as follows: "The undersigned came +together for the purpose of investigating the question +whether or not there is involved in the feats of the horse +of Mr. von Osten anything of the nature of tricks, that +is, intentional influence or aid on the part of the questioner." +It was this preliminary question, and not +whether or not the horse could think, which the commission +intended to answer. They proposed to act as a +sort of court of honor for the two gentlemen who had +been attacked. It is only in this light that even the +<i>raison d'être</i> of this body can be understood; for a +scientific commission composed of thirteen men, possessed +of varying degrees of scientific preparation, would +have been an absurd travesty, and it will readily be seen +why the two men, who had been attacked, should not be +excluded, since it was they, and primarily Mr. von Osten, +upon whom the observations were to be made.</p> + +<p>To be sure the commission did go one step beyond +that which it had proposed to itself, since it added that +it believed that unintentional signs of the kind which are +at present familiar, were also excluded. This led many to +the unwarranted conclusion that the commission had<span class="pagenum"><a name="Page_5" id="Page_5"></a>[Pg 5]</span> +declared that Hans was able to think. Whereas the thing +which might have been logically suggested was that +instead of the assumption of the presence of independent +thinking, the commission may have had in mind unintentional +signs of a kind hitherto unknown. I explained +this to a reporter of the "Frankfurter Zeitung" (Mr. +A. Gold), who had come to me for information, and in +his article he made this hypothesis appear as the most +probable one.<a name="FNanchor_A_1" id="FNanchor_A_1"></a><a href="#Footnote_A_1" class="fnanchor">[A]</a> Certain statements of the circus-manager +Busch, who speaks of a 'connection' of some sort, go to +show that other members of the commission held to the +view just stated.</p> + +<p>But how did it come to pass that the commission should +deny completely the presence of intentional signals, while, +as regards the unintended, it excluded only those which +were of the known sort? The report clearly shows that +the decision as to the absence of voluntary signals was<span class="pagenum"><a name="Page_6" id="Page_6"></a>[Pg 6]</span> +based not merely upon the fact that no such signals had +been detected by the most expert observers, but also +upon the character of the two men who exhibited the +horse, upon their behavior during the entire period, and +upon the method of instruction which Mr. von Osten +had employed. In the case of unintentional signs, on the +other hand, one had to deal with the fact with which +physiologists and experimental psychologists are especially +familiar, viz., that our conscious states, without +our willing it—indeed, even in spite of us—are accompanied +by bodily changes which very often can be detected +only by the use of extremely fine graphic methods. +The following is a more general instance: every mother, +who detects the lie or divines the wish in the eyes of the +child, knows that there are characteristic changes of +facial expression, which are, nevertheless, very difficult +of definition.<a name="FNanchor_B_2" id="FNanchor_B_2"></a><a href="#Footnote_B_2" class="fnanchor">[B]</a></p> + +<p>The commission did not even maintain or believe that +unintentional signs within the realm of the senses known +to us, were to be excluded. Professor Nagel and I +would never have subscribed to any such conclusion. The +sentence in question, therefore, could only be interpreted +as follows: that signals of the kind that are used in<span class="pagenum"><a name="Page_7" id="Page_7"></a>[Pg 7]</span>tentionally +in the training of horses, could not have occurred +even as unintended signs, for otherwise Mr. +Busch would have detected them. And in order to be +observed by him it was immaterial whether they were +given purposely or not. The same signs, therefore, +which as a result of his observations were declared not to +be present, could not be assumed to be involved as unintentional.</p> + +<p>For my part I am ready to confess that at this time I +did not expect to find the involuntary signals, if any such +were involved, in the form of movements. I had in mind +rather some sort of nasal whisper such as had been invoked +by the Danish psychologist A. Lehmann, in order +to explain certain cases of so-called telepathy. I could +not believe that a horse could perceive movements which +escaped the sharp eyes of the circus-manager. To be +sure, extremely slight movements may still be perceived +after objects at rest have become imperceptible. But one +would hardly expect this feat on the part of an animal, +who was so deficient in keenness of vision, as we have +been led, by those of presumably expert knowledge, to +believe of the horse,—one would expect it all the less +because Mr. von Osten and Mr. Schillings would move +hither and thither in most irregular fashion while the +horse was going through his tapping, and would therefore +make the perception of minute movements all the +more difficult.</p> + +<p>Nor was there anything in the exhibitions given at the +same time in a Berlin vaudeville by the mare "Rosa," +which might have shattered this belief. For, in the case +of this rival of Hans, the movements involved were comparatively +coarse. The closing signal consisted in bending +forward on the part of the one exhibiting the mare,<span class="pagenum"><a name="Page_8" id="Page_8"></a>[Pg 8]</span> +while up to that point he had stood bolt upright. Most +persons were not aware of this, because this change in +posture cannot be noticed from the front. I happened +to sit to the side and caught the movement every time. +It was the same that was noted by Dr. Miessner, another +member of the commission, (see <a href="#Page_256">page 256</a>), but +concerning which he did not give me a more complete +account. Later I learned through Professor Th. W. +Engelmann that the very same movement was employed +not long ago, for giving signals to a dog exhibited at +Utrecht. This particular movement is very well adapted +to commercial purposes, since the spectator always tries to +view the performance from a point as nearly in front of +the animal and its master as possible, thus making the +detection of the trick all the more difficult.</p> + +<p>The details of the various experiments made by this +commission are given in an excerpt from the records +kept by Dr. von Hornbostel, which I showed to a small +group of persons a few days after the 12th of September +(<a href="#SUPPLEMENT_III">Supplement III</a>). At that time none of the particulars +was published, because the commission wished to wait +until some positive statement might be made. The public +was merely to be assured that a group of reputable men, +from different spheres of life, who could have no purpose +in hazarding their reputation, believed that the case +was one worthy of careful investigation.</p> + +<p>I left Berlin on September 17th and did not return +until October 3d. In the meantime Mr. Schillings continued +the investigation, and was assisted in part by Mr. +Oskar Pfungst, one of my co-workers at the Psychological +Institute. For the first time a number of tests +were now made in which neither the questioner, nor any +of those present knew the answer to the problem. Such<span class="pagenum"><a name="Page_9" id="Page_9"></a>[Pg 9]</span> +tests naturally were the first steps toward a positive investigation. +The results were such that Mr. Schillings +was led to replace his hypothesis of independent conceptual +thinking by one of some kind of suggestion. In +this he was strengthened somewhat by having noted +the fact that in his questions which he put to the horse, +he might proceed as far as to ask the impossible. He +has always been ready to offer himself in the tests which +have been undertaken since then.</p> + +<p>On October 13, 1904, together with the two gentlemen +mentioned in the beginning of my report, I began my +more detailed investigation, and finished on November +29. We worked for several hours on the average of +four times each week. I take this opportunity of giving +expression of the recognition which is due to the two +gentlemen. They were ready to go to the courtyard in +all kinds of weather, at times they went without me, and +they always patiently discussed the order and method +of the experiments and the results. Dr. von Hornbostel +had the important task of keeping the records, and Mr. +Pfungst undertook the conduct of the experiments. It +was he, who, soon after the blinder-tests disclosed the +necessary presence of visual signs, discovered the nature +of these signs. Without him we might have shown the +horse to be dependent upon visual stimuli in general, +but we never would have been able to gain that mass of +detail, which makes the case valuable for human psychology. +But I am tempted to praise not merely his patience +and skill, but also his courage. For we must not believe +that Mr. von Osten's horse was a "perfectly gentle" +animal. If he stood untied and happened to be excited +by some sudden occurrence, he would make that courtyard +an unsafe place, and both Mr. Schillings and Mr.<span class="pagenum"><a name="Page_10" id="Page_10"></a>[Pg 10]</span> +Pfungst suffered from more than one bite. In this connection +I would also express my obligations to Count +Otto zu Castell-Rüdenhausen, for his frequent intercession +on our behalf with the owner of the horse, and for +his many evidences of good-will and helpfulness.</p> + +<p>After the publication of this report (<a href="#SUPPLEMENT_IV">Supplement IV</a>), +there was still some further discussion of the case in +societies of various kinds and in the press, but no important +objections were raised. A hippologist thought +that men of his calling should have been consulted, a +telepathist believed that telepathists should have been +called in. There was also some further talk of suggestion, +will-transference, thought-reading and the occult, +but no attempt was made to elucidate these vague terms +with reference to their application to the case in hand. +Others adhered to the old cry of "fraud," for a share of +which Mr. Pfungst now fell heir. There were a few who +felt it incumbent upon themselves to preserve their +'priority,' and therefore stated with a show of satisfaction +that I had finally 'confessed' myself to hold their +respective points of view. As if there were anything +like "confessions" in science! As if mere affirmations, +even though sealed and deposited in treasure vaults, had +any value with reference to a case in which every manner +of supposition had been advanced in lieu of explanation. +Why did they wait so long, if they had convincing proof +for their position?</p> + +<p>And finally there were disappointed Darwinists who +expressed fear lest ecclesiastical and reactionary points +of view should derive favorable material from the conclusions +arrived at in my report. Needless fear. For +lovers of truth it must always remain a matter of inconsequence +whether anyone is pleased or displeased with<span class="pagenum"><a name="Page_11" id="Page_11"></a>[Pg 11]</span> +the truth, and whether it is enunciated by Aristotle or +Haeckel.</p> + +<p>Mr. von Osten, however, continued to exhibit Hans, +and is probably doing so still, but in what frame of mind, +I dare not judge. The spectators continue to look on, +they are doubly alert to catch movements, and many of +them have learned from Mr. Schillings what kind of +movements they are to expect. But these "initiated" +ones regularly return and declare that there is nothing in +the movements and that they simply could not discover +any aids given to the horse. Nothing can so well show +how difficult the case is, and how great the need of a +thorough exposition of the whole matter, than the account +given in the following pages of Mr. Pfungst. Its +publication has been delayed on account of the additional +tests made in the laboratory, but we have reason to suppose +that through these additional tests the work has +gained in permanent value. Experimental psychologists +will perhaps be greatly interested in the graphic registration +of the minute involuntary movements which accompany +the thought process, and in the artificial association +of a given involuntary movement with a given +idea. Likewise the tests on sense-perception in horses, +which have led to essential changes in hitherto current +views, and the critical review of the comprehensive literature +on similar achievements of other animals, will be +welcomed by many.</p> + +<p>Before closing these introductory remarks, I would +make one more statement concerning Mr. von Osten. +The reader will notice that the judgment passed upon him +in this treatise is placed at the end, whereas in the report +of the commission it came first. This was brought about +by the change that was made in the way of stating the<span class="pagenum"><a name="Page_12" id="Page_12"></a>[Pg 12]</span> +problem. Then the question discussed was whether +'tricks' were involved; now the question is: What is the +mechanism of the process? The question of the good +faith of the master was taken up once more only because +the facts that were brought to light by the later experimentation +seemingly brought forward new grounds for +distrust. But by placing this discussion toward the end +of our report we wished to indicate that everything that +is said of the present status of facts, is quite independent +of the view taken concerning Mr. von Osten. Even assuming +that the horse had been purposely trained by him +to respond to this kind of signal, the case would still +deserve a place in the annals of science. For visual signs, +planned and practiced so that they could not only be +more readily perceived by the animal than by man, but +could be transferred from their inventor to others without +any betrayal of the secret,—this would be an extraordinary +invention, and Mr. von Osten would then be a +fraud, but also a genius of first rank.</p> + +<p>In truth he probably was neither, but I was brief +in my report, for otherwise I would have been obliged +to go into more detail than the case warranted. And a +judgment passed upon a human personality is quite a +different matter from a judgment upon a horse. If it is +unscientific to make unqualified statements concerning +a horse after the performance of only a few experimental +tests, it is certainly an unwarranted thing to pass a moral +judgment upon a man upon the basis of meagre material. +Anyone who would assume the rôle of judge should bear +in mind that here too we have more than a hundredfold +the material which they could bring forward, and among +it some which, if taken alone, would be more unfavorable +than any that they had. But here all things should be<span class="pagenum"><a name="Page_13" id="Page_13"></a>[Pg 13]</span> +weighed together, and not in isolation. A former instructor +of mathematics in a German gymnasium, a passionate +horseman and hunter, extremely patient and at +the same time highly irrascible, liberal in permitting the +use of the horse for days at a time and again tyrannical +in the insistence upon foolish conditions, clever in his +method of instruction and yet at the same time possessing +not even the slightest notion of the most elementary conditions +of scientific procedure,—all this, and more, goes +to make up the man. He is fanatic in his conviction, he +has an eccentric mind which is crammed full of theories +from the phrenology of Gall to the belief that the horse +is capable of inner speech and thereby enunciates inwardly +the number as it proceeds with the tapping. From +theories such as these, and on the basis of all sorts of +imagined emotional tendencies in the horse, he also +managed to formulate an explanation for the failure of +the tests in which none of the persons present knew the +answer to the problem given the horse, and also for the +failure of those tests in which the large blinders were +applied. And he would often interfere with or hinder +other tests which, according to his point of view, were +likely to lead us astray. And yet, when the first tests +with the blinders did turn out as unmistakably sheer +failures, there was such genuine surprise, such tragi-comic +rage directed against the horse, that we finally +believed that his views in the matter would be changed +beyond a doubt. "The gentlemen must admit," he said +at the time, "that after seeing the objective success of +my efforts at instruction, I was warranted in my belief +in the horse's power of independent thought." Nevertheless, +upon the following day he was as ardent an ex<span class="pagenum"><a name="Page_14" id="Page_14"></a>[Pg 14]</span>ponent +of the belief in the horse's intelligence as he ever +had been.</p> + +<p>And finally, after I could no longer keep from him the +results of our investigation, I received a letter from him +in which he forbade further experimentation with the +horse. The purpose of our inquiries, he said, had been to +corroborate his theories. On account of his withdrawal +of the horse a few experimental series unfortunately +could not be completed, but happily the major portion of +our task had been accomplished.</p> + + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_15" id="Page_15"></a>[Pg 15]</span> + +<h1>THE HORSE OF MR. VON OSTEN</h1> +<hr style="width: 10%;"> +<h2 style="padding-bottom:1em;padding-top:.25em;"><a name="CHAPTER_I"></a>CHAPTER I</h2> +<h2 style="padding-bottom:1em;">THE PROBLEM OF ANIMAL CONSCIOUSNESS AND "CLEVER HANS"</h2> + + +<p><span class="firstwords">If</span> we would appreciate the interest that has been +aroused everywhere by the wonderful horse solving +arithmetical problems, we must first consider briefly the +present state of the problem of animal consciousness.<a name="FNanchor_C_3" id="FNanchor_C_3"></a><a href="#Footnote_C_3" class="fnanchor">[C]</a> +Animal consciousness cannot be directly gotten at, and +the psychologist must therefore seek to appreciate it on +the basis of the animal's behavior and with the assistance +of conceptions borrowed from human psychology. +Hence it is that animal psychology rests upon uncertain +foundations with the result that the fundamental principles +have been repeatedly questioned and agreement +has not yet been attained. The most important of these +questions is, "Does the animal possess consciousness, +and is it like the human consciousness?" Comparative +psychologists divide into three groups on this question.</p> + +<p>The one group allows consciousness to the lower +forms, but emphasizes the assertion that between the +animal and the human consciousness there is an impassable<span class="pagenum"><a name="Page_16" id="Page_16"></a>[Pg 16]</span> +gap. The animal may have sensations and memory-images +of sensations which may become associated in +manifold combinations. Both sensations and memory +images are believed to be accompanied by conditions of +pleasure and of pain (so-called sensuous feelings), and +these in turn, become the mainsprings of desire. The +possession of memory gives the power of learning +through experience. But with this, the inventory of the +content of animal consciousness is exhausted. The +ability to form concepts<a name="FNanchor_D_4" id="FNanchor_D_4"></a><a href="#Footnote_D_4" class="fnanchor">[D]</a> and with their aid to make +judgments and draw conclusions is denied the lower +forms. All the higher intellectual, æsthetic and moral +feelings, as well as volition guided by motives, are also +denied. Among the ancients this view was held by Aristotle +and the Stoics; and following them it was taught +by the Christian Church. It pervaded all mediæval +philosophy, which grew out of the teachings of Aristotle +and the Church. It is this philosophy, in the form of +Neo-Thomism, which still obtains in the Catholic world.</p> + +<p>During the 17th century, even though temporarily, another +conception of the consciousness of lower forms +came to prevail and was introduced by Descartes, the +"Father" of modern philosophy. Far more radical than +the earlier conception, it denied to animals not only the<span class="pagenum"><a name="Page_17" id="Page_17"></a>[Pg 17]</span> +power of abstract thought, but every form of psychic +life whatever, and reduced the lower form to a machine, +which automatically reacted upon external stimuli. This +daring view, however, prevailed for only a comparatively +short period; but owing to the opposition which it +aroused, it gave a tremendous impetus to the study of +animal consciousness. Most of the great philosophers +following Descartes, such as Locke, Leibniz, Kant, and +Schopenhauer, however greatly they may have differed +in other points, in this one returned to the Aristotelian +point of view.</p> + +<p>A third belief avers that animal and human consciousness +do not differ in essentials, but only in degree. This +conclusion is regularly arrived at by those who regard +so-called abstract thought itself, as simply a play of individual +sensations and sensation-images, as did the +French and British associationists (Condillac and the +Mills). The superiority of man accordingly consisted +in his ability to form more intricate ideational complexes. +Again, this conception of the essential similarity of the +human and the animal psyche has also always been arrived +at by the materialists (from Epicurus to C. Vogt +and Büchner) who impute reason to the animal form as +well as to man. The same position is, furthermore, taken +by the evolutionists, including those who do not subscribe +to the doctrines of materialism. It has almost become +dogma with them that there exists an unbroken chain +of psychic life from the lowest protozoa to man. +Haeckel, preëminently, though not always convincingly, +sought to establish such a graded series and thus to +bridge the chasm between the human and the animal +consciousness.</p> + +<p>Two tendencies, therefore, are discernible in animal<span class="pagenum"><a name="Page_18" id="Page_18"></a>[Pg 18]</span> +psychology. The one seeks to remove the animal psyche +farther away from the human, the other tries to bring +the two closer together. It is undoubtedly true that many +acts of the lower forms reveal nothing of the nature of +conceptual thinking. But that others might thus be +interpreted cannot be denied. But need they be thus interpreted?—There +lies the dispute. A single incontrovertible +fact which would fulfil this demand, [i.e., proof of +conceptual thinking], would, at a stroke, decide the question +in favor of those who ascribe the power of thought +to the lower forms.</p> + +<p>At last the thing so long sought for, was apparently +found: A horse that could solve arithmetical problems—an +animal which, thanks to long training, mastered not +merely rudiments, but seemingly arrived at a power of +abstract thought and which surpassed, by far, the highest +expectations of the greatest enthusiast.</p> + +<p>And now what was it that this wonderful horse could +do? The reader may accompany us to an exhibition +which was given daily before a select company at about +the noon hour in a paved courtyard surrounded by high +apartment houses in the northern part of Berlin. No +fee was ever taken. The visitor might walk about freely +and if he wished, might closely approach the horse and +its master, a man between sixty and seventy years of age. +His white head was covered with a black, slouch hat. +To his left the stately animal, a Russian trotting horse, +stood like a docile pupil, managed not by means of the +whip, but by gentle encouragement and frequent reward +of bread or carrots. He would answer correctly, nearly +all of the questions which were put to him in German. +If he understood a question, he immediately indicated +this by a nod of the head; if he failed to grasp its im<span class="pagenum"><a name="Page_19" id="Page_19"></a>[Pg 19]</span>port, +he communicated the fact by a shake of the head. +We were told that the questioner had to confine himself +to a certain vocabulary, but this was comparatively rich +and the horse widened its scope daily without special +instruction, but by simple contact with his environment. +His master, to be sure, was usually present whenever +questions were put to the horse by others, but in the +course of time, he gradually responded to a greater and +greater number of persons. Even though Hans did not +appear as willing and reliable in the case of strangers +as in the case of his own master, this might easily be +explained by the lack of authoritativeness on their part +and of affection on the part of Hans, who for the last +four years had had intercourse only with his master.</p> + +<p>Our intelligent horse was unable to speak, to be sure. +His chief mode of expression was tapping with his right +forefoot. A good deal was also expressed by means of +movements of the head. Thus "yes" was expressed by +a nod, "no" by a deliberate movement from side to +side; and "upward," "upper," "downward," "right," +"left," were indicated by turning the head in these directions. +In this he showed an astonishing ability to +put himself in the place of his visitors. Upon being +asked which arm was raised by a certain gentleman opposite +him, Hans promptly answered by a movement to +the right, even though seen from his own side, it would +appear to be the left. Hans would also walk toward the +persons or things that he was asked to point out, and he +would bring from a row of colored cloths, the piece of the +particular color demanded. Taking into account his +limited means of expression, his master had translated a +large number of concepts into numbers; e. g.:—the letters +of the alphabet, the tones of the scale, and the names of<span class="pagenum"><a name="Page_20" id="Page_20"></a>[Pg 20]</span> +the playing cards were indicated by taps. In the case of +playing cards one tap meant "ace," two taps "king," +three "queen," etc.</p> + +<p>Let us turn now to some of his specific accomplishments. +He had, apparently, completely mastered the +cardinal numbers from 1 to 100 and the ordinals to 10, at +least. Upon request he would count objects of all sorts, +the persons present, even to distinctions of sex. Then +hats, umbrellas, and eyeglasses. Even the mechanical +activity of tapping seemed to reveal a measure of intelligence. +Small numbers were given with a slow +tapping of the right foot. With larger numbers he +would increase his speed, and would often tap very +rapidly right from the start, so that one might have +gained the impression that knowing that he had a large +number to tap, he desired to hasten the monotonous +activity. After the final tap, he would return his right +foot—which he used in his counting—to its original +position, or he would make the final count with a very +energetic tap of the left foot,—to underscore it, as it +were. "Zero" was expressed by a shake of the head.</p> + +<p>But Hans could not only count, he could also solve +problems in arithmetic. The four fundamental processes +were entirely familiar to him. Common fractions +he changed to decimals, and <a name="tn_png_27"></a><!--TN: "vice versa" italicized--><i>vice versa</i>; he could solve +problems in mensuration—and all with such ease that it +was difficult to follow him if one had become somewhat +rusty in these branches. The following problems are +illustrations of the kind he solved.<a name="FNanchor_E_5" id="FNanchor_E_5"></a><a href="#Footnote_E_5" class="fnanchor">[E]</a> "How much is 2/5 +plus ½?" Answer: 9/10. (In the case of all fractions Hans +would first tap the numerator, then the denominator; in<span class="pagenum"><a name="Page_21" id="Page_21"></a>[Pg 21]</span> +this case, therefore, first 9, then 10). Or again: "I have +a number in mind. I subtract 9, and have 3 as a remainder. +What is the number I had in mind?"—12. +"What are the factors of 28?"—Thereupon Hans tapped +consecutively 2, 4, 7, 14, 28. "In the number 365287149 +I place a decimal point after the 8. How many are there +now in the hundreds place?"—5. "How many in the +ten thousandths place?"—9. It will be noticed, therefore, +that he was able to operate with numbers far exceeding +100, indeed he could manipulate those of six +places. We were told that this, however, was no longer +arithmetical computation in the true sense of the term; +Hans merely knew after the analogy of 10 and 100 that +the thousands take the fourth place, the ten-thousands +the fifth, etc. If an error entered into Hans' answer, he +could nearly always correct it immediately upon being +asked: "By how many units did you go wrong?"</p> + +<p>Hans, furthermore, was able to read the German readily, +whether written or printed. Mr. von Osten, however, +taught him only the small letters, not the capitals. +If a series of placards with written words were placed +before the horse, he could step up and point with his +nose to any of the words required of him. He could +even spell some of the words. This was done by the aid +of a table devised by Mr. von Osten, in which every +letter of the alphabet, as well as a number of diphthongs +had an appropriate place which the horse could designate +by means of a pair of numbers. Thus in the fifth horizontal +row "s" had first place; "sch" second, "ss," +third, etc.; so that the horse would indicate the letter +"s" by treading first 5, then 1, "sch," by 5 and 2, +"ss" by 5 and 3. Upon being asked "What is this +woman holding in her hand?" Hans spelled without<span class="pagenum"><a name="Page_22" id="Page_22"></a>[Pg 22]</span> +hesitation: 3, 2; 4, 6; 3, 7; i. e., "Schirm" (parasol). +At another time a picture of a horse standing at a manger +was shown him and he was asked, "What does this +represent?" He promptly spelled "Pferd" (horse) +and then "Krippe" (manger).</p> + +<p>He, moreover, gave evidence of an excellent memory. +In passing we might also mention that he knew the value +of all the German coins. But most astonishing of all was +the following: Hans carried the entire yearly calendar +in his head; he could give you not only the date for each +day without having been previously taught anew, but +he could give you the date of any day you might mention. +He could also answer such inquiries as this: "If the +eighth day of a month comes on Tuesday, what is the +date for the following Friday?" He could tell the time +to the minute by a watch and could answer off-hand the +question, "Between what figures is the small hand of a +watch at 5 minutes after half-past seven?" or, "How +many minutes has the large hand to travel between seven +minutes after a quarter past the hour, and three quarters +past?" Tasks that were given him but once would +be repeated correctly upon request. The sentence: +"Brücke und Weg sind vom Feinde besetzt" (The +bridge and the road are held by the enemy), was given +to Hans one day and upon the following day he tapped +consecutively the 58 numbers which were necessary for a +correct response. He recognized persons after having +seen them but once—yes, even their photographs taken +in previous years and bearing but slight resemblance.</p> + +<p>A corresponding high degree of sensory activity +seemed to accompany these astonishing feats of memory +and reason. Although the horse is not usually credited +with a very keen sense of vision, Hans was able to count<span class="pagenum"><a name="Page_23" id="Page_23"></a>[Pg 23]</span> +the windows of distant houses and the street urchins +climbing about on neighboring roofs. He had an ear +for the most subtle nuances of the voice. He caught +every word,—no matter how softly it was spoken—so +that we were not allowed to whisper the answer to a +problem, even when standing at a distance of several +yards, since it would be equivalent—so Mr. von Osten +declared—to giving the result to the horse.</p> + +<p>Musical ability also comes into the category of Hans' +accomplishments. He possessed, not only an absolute +tone consciousness—a gift granted to few of us in the +human world—which enabled him to recognize a note +sounded or sung to him as c, d, etc. (within the once +accented scale of c-major), but also an infallible feeling +for intervals, and could therefore determine whether two +tones, sounded simultaneously, composed a third or fifth, +etc. Without difficulty he analyzed compound clangs into +their components; he indicated their agreeableness or +disagreeableness and could inform us which tones must be +eliminated to make consonance out of dissonance. C, d +and e were given simultaneously and Hans was asked: +"Does that sound pleasant?" He shook his head. +"What tone must be omitted to make it pleasant?" Hans +trod twice—indicating tone "d." When the seventh +chord, d-f-a-c, was sounded, he shook his head disapprovingly. +He evidently was old-fashioned in his musical +tastes and not agreeably disposed toward modern music, +so he indicated by tapping that the seventh, c, would +have to be eliminated; thus changing the seventh chord +to a minor chord in order to obtain harmony. When +asked what tones might not be given simultaneously +with the fourth and sixth, Hans indicated consecutively +the third, fifth and seventh; that the first might be added,<span class="pagenum"><a name="Page_24" id="Page_24"></a>[Pg 24]</span> +he was ready to admit. Finally, he was familiar with not +less than thirteen melodies and their time.</p> + +<p>Not only in the high degree of development of the +senses and the intellect, but also in that of the feeling and +the will, did Hans possess a decided individuality. Being +of a high-strung and nervous temperament and governed +by moods, he evinced strong likes and dislikes, and frequently +displayed an annoying stubbornness,—a fact often +dwelt upon by Mr. von Osten. He had never felt the +whip, and therefore often persisted in wilfully answering +the simplest questions incorrectly and a moment later +would solve, with the greatest ease, some of the most +difficult problems. Whenever any one asked a question +without himself knowing the answer, Hans would indulge +in all sorts of sport at the questioner's expense. +We were told that the sensitive animal could easily perceive +the questioner's ignorance and would therefore +lose confidence in, and respect for, him. It was felt to +be desirable, however, to have just such cases with correct +responses. Often, too, Hans would persist in giving +what seemed an incorrect reply, but which was later discovered +to be correct. On the other hand it was useless +to try to get answers upon topics of which he knew +nothing. Thus he ignored questions put in French or +Latin and became fidgety, thereby showing the genuineness +of his achievements; but upon topics with which +he was familiar he could not be led astray. Indeed, +there was nothing but language lacking to make him +almost human and the intelligent animal was declared +by experienced educators to be at about the stage of +development of a child of 13 or 14 years.</p> + +<p>This wonderful horse, which in the opinion of its +friends was the means of deciding in the affirmative the<span class="pagenum"><a name="Page_25" id="Page_25"></a>[Pg 25]</span> +old, old, question of the rationality of the lower forms +and thus changing radically the existing Weltanschauung, +aroused world-wide interest. A flood of articles +appeared in the newspapers and magazines, two +monograph<a name="refanchor1"></a><a href="#ref_1" class="fnanchor">[1,</a> <a name="refanchor2"></a><a href="#ref_2" class="fnanchor">2]</a> attempts at explanation were devoted to +him.<a name="FNanchor_F_6" id="FNanchor_F_6"></a><a href="#Footnote_F_6" class="fnanchor">[F]</a> He was made the subject of popular couplets, and +his name was sung on the vaudeville stage. He appeared +upon picture post-cards and upon liquor labels, and his +popularity was shown by his reincarnation in the form +of children's playthings. Many personages of note who +had seen the horse's exhibitions, declared, some of them +in public statements, that they were now convinced. +Among these, besides Mr. Schillings, were naturalists +of note; e. g.: the African explorer Prof. G. Schweinfurth, +Dr. Heinroth and Dr. Schäff, the director of the +zoological garden in Hanover; there were likewise +horse-fanciers of first-rank, such as General Zobel, and +the well-known hippological writer Major R. Schoenbeck. +Again, the well-known zoölogist, K. Möbius, +writing in the "National-zeitung" declared he was +convinced of the horse's power to count and to solve +arithmetical problems. He also said that he believed +the horse's memory and acute power of sense-discrimination +to be at the root of the matter. Those +who gleaned all their knowledge of the horse from newspaper +reading were satisfied to arrest judgment, or, on +the other hand, became indignant at the supposed imposition +on the part of the gentleman of leisure and at the +gullibility of the public. Some would of course attempt +explanations on the basis of older facts. Here we have +two points of view.</p> +<span class="pagenum"><a name="Page_26" id="Page_26"></a>[Pg 26]</span> + +<p>Some tried to explain the whole thing on the basis of +purely mechanical memory and would thus allow the +title "learned" but not "intelligent" Hans. If, for instance, +he was able to indicate the component of a clang +of three tones, it was not because he had the power to +analyze the tone-complex, but because he was able to +see the stops of the harmonica and was accustomed to +give one tap for every stop which was closed. If he +was able to tell time by the watch, it was not because +he read it, but because he was always asked at the same +hour of the day (which, of course, was contrary to fact) +and because he had learned by heart the necessary +number of taps. They also said that his manifold arithmetical +achievements were merely the expression of a +remarkable memory; that in the animal brain, lying +fallow for centuries, there was stored up a tremendous +amount of energy, which here had been suddenly +released. They justified their point by calling to mind, +in this connection, the wonderful memory of primitive +races. The authors of the two monographs already +mentioned, Zell and Freund, adopted this 'mnemotechnic' +interpretation, and the latter considered that he +had disposed definitely of the problem in designating the +horse—a "four-legged computing machine."</p> + +<p>Another group would not even allow Hans the glory +of a wonderful memory. He knew nothing. Rather +was he to be regarded as a stupid Hans, and totally +dependent upon signs or helps given by his master. +Only a very few believed, however, that such signs—the +nature of which was quite unknown or regarding which +only vague unsubstantiated suppositions were advanced—were +given unintentionally. Most of the critics openly +averred that we here had to do with intentional control,<span class="pagenum"><a name="Page_27" id="Page_27"></a>[Pg 27]</span> +in other words, with tricks. But not only did stupid +orthodoxy dispose of the matter in this way, but also the +enlightened, who believe everything unusual to be contrary +to reason. They put the Hans problem on a level +with spiritualism, and were convinced that if the veil +were removed a crass imposition would be revealed. +Professional trainers who regarded themselves as well +informed did not hesitate to give expression to this same +view, even though they had observed Hans inadequately +or not at all.</p> + +<p>The defenders of this second point of view were not +at a loss to point out the signs supposed to be given to +Hans. One of these believed he had discovered the +primary means for giving these signs in the slouch hat +of Mr. von Osten. It was no accident, they said, that +Mr. Schillings wore a slouch hat when he experimented +with the horse. It is sufficient to note that Mr. Schillings +was usually bare-headed or wore only a cap when +he tested the horse. Another accused, in like fashion, +the long coat of the experimenter; a third, who "had +had opportunity to observe Hans on several occasions," +declared with equal certainty that the cue lay in the +movements of the hand as it was thrust into the pocket +filled with carrots. One circus-star declared, that the +trick lay in eye movements, another such star declared it +lay in the movements of the hand. A sixth discovered +that the signs were "manifold" and adds, "to be sure, the +trainer must have a fund of such signs in order to prevent +embarrassment." Such a hypothesis is itself, it would +seem, one of embarrassment. On the other hand, there +were many first-class observers who vainly tried to discover +regularly recurring signs; among them the only +professional trainer,—who had devoted any satisfactory<span class="pagenum"><a name="Page_28" id="Page_28"></a>[Pg 28]</span> +length of time to the horse and had also sought diligently +for the signs in question—said, "I was fully convinced +that I would be able to explain the problem in this way, +but I was mistaken." The president of the "Internationale +Artisten Genossenschaft," a person who knew +all the usual means of control in trick performances, went +over to the other side as a result of his observations.</p> + +<p>There were others who sought for auditory signs. The +opinion was expressed that "Hans was unable to answer +the simplest question such as 'What is two plus three?' +whenever the questioner's tone of voice differed from +that of the master's." Another put chief stress upon the +changing inflection; furthermore, a "high degree of +auditory sensitivity" was often offered in explanation.</p> + +<p>The sense of smell was also made to bear some burdens. +With its help, for instance, Hans was believed to +be able to recognize the photograph of some one present, +supposing, of course, that the person had carried the +picture about with him, thus allowing it to be impregnated +with his peculiar personal odor. One even suggested +that the heat radiating from the questioner's body +and the electric stimulus conducted underground to +Hans's foot were sufficient explanation for his remarkable +feats.</p> + +<p>Even the so-called N-rays, of one-day fame, which +were supposed to radiate from the human brain when in +activity, were offered as a solution. A similar thing may +have been in the mind of the "natural philosopher" who +even after the publication of the December report, wrote +as follows in one of the journals: "On the basis of most +careful control, I have come to the conclusion, that the +brain of the horse receives the thought-waves which radiate +from the brain of his master; for mental work is,<span class="pagenum"><a name="Page_29" id="Page_29"></a>[Pg 29]</span> +according to the judgment of science, physical work." +Of the same character are the explanations of two others, +one of whom declares that Hans was acting "under the +magnetic influence of man", while the other declared that +"hypnotic suggestion is involved", and, ignoring attested +facts, tells us that, "The horse can execute the commands +of another only when the master, with whom it is +'en rapport', wills that it shall obey." We may close +the catalogue of explanations with one more, which, in +spite of its vagueness, found many defenders, viz: suggestion. +Without defining this conception more specifically +and without the slightest notion of the peculiar difficulties +which it involves (L. Loewenfeld in his "Handbuch +des Hypnotismus" [Wiesbaden, 1901, pp. 35ff.] +cites twenty different definitions of the term given by as +many authors) a critic writes: "The astounding phenomenon +of an animal apparently possessing human reason +is to be attributed solely to suggestion". Having referred +to a dog trained for the vaudeville-stage, the gentleman +concludes that, "our intelligent horse, as well as +the dog, is simply of fine nervous organization and hence +highly susceptible to suggestions".</p> + +<p>What was to be done, with this mass of conflicting explanations? +Everyone considered his own opinion the +only correct one, without, however, being able to convince +anyone else. The need here was not simple affirmation, +but proof. + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_A_1" id="Footnote_A_1"></a><a href="#FNanchor_A_1"><span class="label">[A]</span></a> "Frankfurter Zeitung" of September 22, 1904: "Concerning the +question whether the horse was given some sort of aid, Professor +Stumpf expressed himself freely. He said: 'We were careful to state +in our report that the intentional use of the (actual) means of training, +on the part of the horse's teacher, is out of the question, ... nor are +there involved any of the known kinds of unconscious, involuntary aids. +Our task was completed after we had ascertained that no tricks or aids +of the traditional sort were being employed'." After some remarks on +unconscious habituation and self-training on the part of animals, the +writer arrives at the conclusion that "the horse of Mr. von Osten has +been educated by its master in the most round-about way, in accordance +with a method suited for the development of human reasoning +powers, hence in all good faith, to give correct responses by means of +tapping with the foot. But what the horse really learned by this wearisome +process was something quite different, something that was more +in accord with his natural capacities,—he learned to discover by purely +sensory aids which are so near the threshold that they are imperceptible +for us and even for the teacher, when he is expected to tap with his +foot and when he is to come to rest."</p></div> + +<div class="footnote"><p><a name="Footnote_B_2" id="Footnote_B_2"></a><a href="#FNanchor_B_2"><span class="label">[B]</span></a> "From the productions of the 'thought-readers' we see how slight +and seemingly insignificant the unconscious movements may be, which +serve as signs for a sensitive re-agent. But in this case no contact is +necessary. There would have to be some sort of visible or audible expression +on the part of the questioner. No proof for this has as yet +been advanced." +</p><p> +How any one possessing the power of logical thought could possibly +infer from these words of mine (published in the above-mentioned article +in the "Tag"), that I denied the possibility of the occurrence of +visual signs, is to me incomprehensible. What I did deny, and still +deny, is that up to that time any had been proven to occur.</p></div> + +<div class="footnote"><p><a name="Footnote_C_3" id="Footnote_C_3"></a><a href="#FNanchor_C_3"><span class="label">[C]</span></a> Since the present treatise is intended for the larger public, this +brief resumé will probably be welcome to many.</p></div> + +<div class="footnote"><p><a name="Footnote_D_4" id="Footnote_D_4"></a><a href="#FNanchor_D_4"><span class="label">[D]</span></a> Ideas are copies of former sensations, feelings and other psychic +experiences and retain also the accidental signs which belonged to those +earlier experiences. They are images in the concrete, such as the +memory of a certain horse in a certain definite situation ... say a +well fed, long-tailed one standing at a manger. A concept, on the other +hand, is a mental construct which has its rise in ideas, or memory-images, +in that their essential characteristics are abstracted. For this +reason the concept has not a definite image-content. (Thus the thought +of "horse" in general, is a concept. Not so the thought of a certain +individual horse,——that is an idea, with a definite image-content.)</p></div> + +<div class="footnote"><p><a name="Footnote_E_5" id="Footnote_E_5"></a><a href="#FNanchor_E_5"><span class="label">[E]</span></a> All examples mentioned are cited from extant works of various +observers.</p></div> + +<div class="footnote"><p><a name="Footnote_F_6" id="Footnote_F_6"></a><a href="#FNanchor_F_6"><span class="label">[F]</span></a> The +works referred to in the text are to be found listed on +<a href="#Page_267">pages 267 ff.</a></p></div> +</div> + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_30" id="Page_30"></a>[Pg 30]</span> +<h2 style="padding-bottom:1em;"><a name="CHAPTER_II" id="CHAPTER_II"></a>CHAPTER II</h2> +<h2 style="padding-bottom:1em;">EXPERIMENTS AND OBSERVATIONS</h2> + + +<h3 class="smcap">A. Experimental Conditions</h3> + +<p><span class="firstwords">The</span> observations on the horse under ordinary conditions +would have been quite insufficient for arriving at a +decision as to the tenability of the several possible explanations. +For this purpose experimentation with controlled +conditions was necessary.</p> + +<p>It was necessary, first, that the place in which the +experiments were performed should be guarded against +sources of error and interruptions. Several difficulties +stood in the way of the removal of the horse to a +more convenient place. Therefore, a large canvas tent +was erected within the courtyard of Mr. von Osten. This +afforded the necessary isolation without hindering the +free movements of the horse. After the essential part of +the experiment had been completed and the problem had +been practically solved, experimentation was sometimes +conducted in the open courtyard. A number of the experiments +were also performed in the horse's stall.</p> + +<p>The choice of proper persons to experiment with the +horse required careful consideration. In so far as observations +were to be made upon the questioner, Mr. +von Osten was of course indispensable. But to obviate +every objection he, as well as Mr. Schillings, had to be +excluded from the greater part of the experiments, and<span class="pagenum"><a name="Page_31" id="Page_31"></a>[Pg 31]</span> +other persons had to be selected who could learn to handle +the horse. Now one would have thought that the horse +would respond to any moderately efficient examiner. But +as a matter of fact it was found that the horse would not +react at all in the case of the greater number of persons. +Again, in the case of others he would respond once or +twice, but would then cease. All told, Hans responded +more or less readily to forty persons, but it was only when +he worked with Mr. von Osten or with Mr. Schillings, +that his responses were at all dependable. For this reason +I undertook to befriend the horse, and by happy chance it +came to pass in a short time he responded as readily to +my questions as to those of the two gentlemen. In a few +of these experiments the Count zu Castell, Count R. von +Matuschka and Mr. Schillings undertook the rôle of +questioner. Where these are not mentioned in the results +here published, I myself did the questioning.</p> + +<p>With regard to the number of experiments and their +performance, the following precautions were observed. +A sufficiently large number of tests was made in each +series in order to obviate the possibility of the contention +that the horse's errors were due to chance. The conditions +of experimentation were such that the further contention +that he happened to be tired or otherwise indisposed, +whenever the reactions seemed to be inadequate, +could not be offered. The possibility of confusing the +horse by means of unwonted conditions also had to be +avoided. For this reason it was necessary to alternate the +trial in which procedure was with the knowledge of the +answer on the part of the questioner, with the trial in +which the procedure was without such knowledge. Such +precautions had hitherto been neglected, and therefore +those negative results which had been occasionally ob<span class="pagenum"><a name="Page_32" id="Page_32"></a>[Pg 32]</span>tained +in single trials, could not claim objective validity, +even though the persons making the tests were subjectively +convinced.</p> + +<p>The course of the experiments was determined by the +nature of the problem itself. By means of a very simple +test it was possible to discover whether or not Hans was +able to think independently. He was confronted with +problems in which the procedure was without knowledge +of the answer on the part of the questioner. If under +these conditions he could respond with the correct answer—which +could be the result of a rational process +only—then the conclusion that he could think independently, +was warranted. The examination would be closed +and Mr. von Osten would be justified in all he claimed +for the horse. If, however, Hans should fail in this test, +then the conclusion that he could think was by no means +warranted, but rather the inference that he was dependent +upon certain stimuli received from the questioner or the +environment. Further investigation would be for the purpose +of discovering the nature of these stimuli.</p> + +<p>To ascertain by means of which sense organ or organs +the horse might receive these necessary stimuli, the +method of elimination was employed. We began by excluding +visual stimuli by means of a pair of very large +blinders. Should this investigation be without results, +then we would proceed to test the sense of hearing. The +elimination of auditory stimulations would be more difficult, +because ear-caps or the closing of the passage by +means of cotton would not give sufficient assurance that +the sound-waves were being interrupted, even if the horse +were docile enough to suffer these appliances. Thereupon +would follow the testing of the sense of smell and +of the skin-senses. And finally there might be involved<span class="pagenum"><a name="Page_33" id="Page_33"></a>[Pg 33]</span> +another still unknown sense, such as seems to exist in the +lower animal-forms. The reader therefore can readily see +that the investigation might possibly have become very +complex, and that the investigator had to be prepared for +all of these possibilities.</p> + +<p>The results of the experiments and the essential circumstances +under which they were conducted, were in +every case recorded immediately.</p> + +<p>It goes without saying that in the final formulation of +the results, all values—including those which were not +consonant with the majority—were to be used.</p> + + +<h3 class="smcap">B. Experimental Results</h3> + +<p>During the course of these experiments Hans wore +his accustomed trappings, i. e., a girdle, light headgear +and snaffle, and he either stood alone, untied, or was held +loosely by the bridle either by the questioner or (though +only in a few instances) by his attendant. The questioner +always stood to the right of the horse, as Mr. von +Osten had been accustomed to do. As reward for correct +responses Hans received from the questioner<a name="FNanchor_G_7" id="FNanchor_G_7"></a><a href="#Footnote_G_7" class="fnanchor">[G]</a>—and from +him only—a bit of bread or carrot, and at times also a +square of sugar. Never was a whip applied. From time +to time the horse was led about the courtyard or was allowed +to run loose in order to secure the needful respite. +Besides myself there was usually present Prof. Stumpf +and Dr. von Hornbostel, who kept the records, and frequently +also Mr. von Osten. Several times I worked +alone with the horse. The results obtained in the horse's +stall were in no respect different from those got in the<span class="pagenum"><a name="Page_34" id="Page_34"></a>[Pg 34]</span> +course of the experiments carried on in the courtyard. +Whenever a doubt arose as to the number of taps made +by the horse (though this did not frequently occur), then +the series in question was immediately repeated.</p> + +<p>In this report of the results of our experiments, the +reader must bear in mind that it was impossible to adhere +to that order and distribution of tests which we are wont +to require in the case of psychophysical experiments conducted +under regular laboratory conditions. All sorts of +difficulties had to be overcome: unfavorable weather, the +crowds of curious ones, certain peculiarities of the horse—such +as shying whenever the wind rippled the canvas +of the tent—and last but not least, the idiosyncrasies of +Mr. von Osten who repeatedly attempted to interrupt the +progress of the experiments.</p> + +<p>Since it was evident that different kinds of processes +were involved in solving the problems and since the solutions +would be indicated by tapping, or by movements of +the head, or by walking over to the object to be designated, +the results of these three sets of experiments have +been grouped under three corresponding heads.</p> + + +<h4><i>I. Problems solved by tapping</i></h4> + +<p>The following tests were made in which the method +was such that when the problem was presented to the +horse, the correct solution was known to none of those +present, least of all to the questioner. This method we +shall designate in the following report as "procedure +without knowledge" whereas we shall call the method in +which the answer was known to the questioner, "procedure +with knowledge".</p> + +<p>In order to discover if the horse could read numbers,<span class="pagenum"><a name="Page_35" id="Page_35"></a>[Pg 35]</span> +a series of cards on which numerals were blazoned, were +exposed to the horse's view in such a way that none of +those present was able to see them, and the horse was +asked to tap the numbers as they were shown. This experiment +was repeated at different times and in all there +were 49 tests in which procedure was without knowledge, +and 42 in which procedure was with knowledge. In the +case of the former there were 8% correct responses, +whereas in the case of the latter 98% of the answers were +right. As an example of the course which the series +tended to take, we insert the following, in which Mr. von +Osten himself acted as questioner.</p> + +<div style="font-size:.8em;"> +<table border="0" width="70%" cellpadding="1" cellspacing="0" summary="Test Result Table 1" align="center"> +<tr valign="top"> +<th colspan="2" align="center" width="40%" style="font-weight:normal;">Method.</th> +<th> </th> +<th align="center" width="22%" style="font-weight:normal;" colspan="3">No. exposed.</th> +<th align="center" width="28%" colspan="3" style="font-weight:normal;">No. tapped.</th> +</tr> + +<tr valign="top"> +<td align="left" width="15%">Without</td> +<td align="center" width="15%">knowledge</td> +<td width="20%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">8</td> +<td width="8%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">14</td> +<td width="8%"> </td> +</tr> + +<tr valign="top"> +<td align="left" width="15%">With</td> +<td align="center" width="15%">"</td> +<td width="20%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">8</td> +<td width="8%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">8</td> +<td width="8%"> </td> +</tr> + +<tr valign="top"> +<td align="left" width="15%">Without</td> +<td align="center" width="15%">"</td> +<td width="20%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">4</td> +<td width="8%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">8</td> +<td width="8%"> </td> +</tr> + +<tr valign="top"> +<td align="left" width="15%">With</td> +<td align="center" width="15%">"</td> +<td width="20%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">4</td> +<td width="8%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">4</td> +<td width="8%"> </td> +</tr> + +<tr valign="top"> +<td align="left" width="15%">Without</td> +<td align="center" width="15%">"</td> +<td width="20%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">7</td> +<td width="8%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">9</td> +<td width="8%"> </td> +</tr> + +<tr valign="top"> +<td align="left" width="15%">With</td> +<td align="center" width="15%">"</td> +<td width="20%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">7</td> +<td width="8%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">7</td> +<td width="8%"> </td> +</tr> + +<tr valign="top"> +<td align="left" width="15%">Without</td> +<td align="center" width="15%">"</td> +<td width="20%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">10</td> +<td width="8%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">17</td> +<td width="8%"> </td> +</tr> + +<tr valign="top"> +<td align="left" width="15%">With</td> +<td align="center" width="15%">"</td> +<td width="20%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">10</td> +<td width="8%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">10</td> +<td width="8%"> </td> +</tr> + +<tr valign="top"> +<td align="left" width="15%">Without</td> +<td align="center" width="15%">"</td> +<td width="20%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">3</td> +<td width="8%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">9</td> +<td width="8%"> </td> +</tr> + +<tr valign="top"> +<td align="left" width="15%">With</td> +<td align="center" width="15%">"</td> +<td width="20%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">3</td> +<td width="8%"> </td> +<td width="8%"> </td> +<td align="right" width="9%">3</td> +<td width="8%"> etc.</td> +</tr> + +</table> +</div> +<p>Whenever the questioner knew the solution, nearly all +of the horse's answers were correct; but when the answers +were unknown to the questioner, the horse's responses +were, with only a few exceptions, quite unsuccessful. +Since the few exceptional cases must be regarded +as fortuitous, the conclusion is warranted that the +horse was unable to read numerals without assistance.</p> + +<p>In order to discover whether the horse could read +words such as "Hans" or "Stall" or the names +of colors, they were written upon placards and hung<span class="pagenum"><a name="Page_36" id="Page_36"></a>[Pg 36]</span> +up in a row before the horse in such a way that the +questioner could see the individual word but could not +immediately recognize the particular place that each one +occupied in the series. The horse was then asked: +"Upon which placard is the word <a name="tn_png_43"></a><!--TN: Double quote added after "'Hans'?"-->'Hans'?", "On which +is the word 'Stall'?", etc. In order to make sure, he +was required to repeat each answer.</p> + +<p>Then the experimenter would determine for himself +the place of the word in the series and would ask the +question again. Fourteen such tests, in which the procedure +was with knowledge on the part of the questioner, +were interspersed with twelve in which the procedure +was without such knowledge. With the latter +there were no correct responses, whereas in the cases of +procedure with knowledge 100% of the answers were +correct. Evidently the horse could not read words.</p> + +<p>Three words were thereupon whispered in his ear, +which he was asked to spell in accordance with the method +described on <a href="#Page_21">page 21</a>. Since he had to indicate first the +row, and then the place in the row occupied by the letter, +it took two answers to indicate the position of each letter. +I acted as questioner. The ordering of the table of letters +was unknown to me, except the position of the letter +"a", which naturally came first, and the place of the +letter "s", concerning whose position I had purposely +inquired. The words chosen for this experiment were +"Arm", "Rom" (Rome) and "Hans". The horse responded +incorrectly in the case of every letter which was +unknown to the questioner. "A" and "s" alone were +given correctly. Thus in spelling the word "Rom" the +horse responded with the series 3, 4; 3, 4; 5, 4; 5, 4; i. e. +"jjst", instead of the correct series: 4, 6; 4, 2; 3, 7. I +later selected three other words, the spelling of which in<span class="pagenum"><a name="Page_37" id="Page_37"></a>[Pg 37]</span>volved +the tapping of thirty-two numbers on the part of +Hans, and whose position I had carefully ascertained beforehand. +When these were given to the horse to spell, +he responded promptly without a single error. Evidently +Hans was unable to spell without assistance of some sort +from the questioner.</p> + +<p>The horse's reputed aptitude in computation was tested +in the following way. Mr. von Osten whispered a number +in the horse's ear so that none of the persons present +could hear. Thereupon I did likewise. Hans was asked +to add the two. Since each of the experimenters knew +only his own number, the sum, if known to anyone, could +be known to Hans alone. Every such test was immediately +repeated with the result known to the experimenters. +In 31 tests in which the method was procedure +without knowledge, 3 of the horse's answers were correct, +whereas in the 31 tests in which the method was procedure +with knowledge, 29 of his responses were correct. +Since the three correct answers in the cases in which procedure +was without knowledge evidently were accidental, +the results of this series of experiments show that Hans +was unable to solve arithmetical problems.</p> + +<p>For the purpose of discovering whether the horse could +at least count, the Russian kindergarten device, which Mr. +von Osten had used in training, was utilized. The machine +was placed before the horse, but the experimenter +turned his back upon it. Before each test, a number of +balls were pushed to one side and Hans's problem was to +indicate the number thus separated. Each test was repeated +with procedure with knowledge. Of eight such +experiments Hans responded successfully every time procedure +was with knowledge but failed every time procedure +was without knowledge. Thus 7 balls were at one<span class="pagenum"><a name="Page_38" id="Page_38"></a>[Pg 38]</span> +time designated as 9 and later as 14, while 6 were at first +designated as 12, and later as 10. Since all these errors +could not be accounted for on the ground of miscounts +on the part of the horse, it was evident that Hans is quite +unable to count.</p> + +<p>The memory-test was conducted in the following manner. +In the absence of the questioner a number or the +name of some day of the week was spoken to the horse. +The experimenter would then return and question him. +Of 10 responses 2 were correct, 8 incorrect. Among the +correct answers were the number 3, a number which, as +we shall see, Hans was prone to give under all sorts of +conditions, and which therefore meant very little when +given as a correct response. The number 2, on the other +hand, was consecutively indicated by 7, 9, 5, and 3, 8 was +given as 5, 6, 4, and 6, consecutively; and finally Wednesday +was indicated as the fourteenth day of the week. +After this we undertook the test the horse's far-famed +knowledge of the calendar. Dates, such as Feb. 29, +Nov. 12, etc., were given to Hans and he was asked +to indicate on which day of the week they fell. Sunday +was to be indicated by 1, Monday by 2, etc. Of 14 such +tests, 10 were unsuccessful, 4 successful. But in the case +of these 4 something very interesting occurred. It happened +that during this series the keeper of the horse was +present, and he happened to know the days on which +these dates fell,—as he himself testified. The dates in +question were also little more than a week or so from the +day of the experiment, so they could easily be determined. +But as soon as we took more remote dates both +man and beast were hopelessly lost. It was certain that +Hans had no knowledge of the calendar. It is needless +to say anything of his supposed knowledge of cards and<span class="pagenum"><a name="Page_39" id="Page_39"></a>[Pg 39]</span> +coins. Hans plainly was incapable of the astonishing +feats of memory which had been claimed for him.</p> + +<p>Finally we investigated Hans' musical ability. In a +room adjoining the horse's stall there was a small harmonica, +which spanned the once accented octave. On this +one or more tones were played. The horse was required +to indicate the tone played, the number of tones played +and their relation to one another. For testing his general +hearing 20 tests were given in which the method was procedure +without knowledge. Of the responses only one +was correct, and that one was the tone e, for which the +proper response was three taps, but we must bear in mind +what has already been said of the number 3. The tone +b was indicated by 11 taps, although Hans had only +learned a scale of one octave and therefore could respond +to only seven tones. In the tests in which the method +was procedure with knowledge, he again, without exception, +was successful. Similar results were obtained in the +analysis of compound clangs. In the cases of procedure +without knowledge (although the experimenter here +knew the correct responses, he purposely refrained from +thinking of them) not a single response was correct; +while in the cases of procedure with knowledge, all but +one were correct. The following were typical responses: +Three tones were played and the question was +asked, "How many tones were played?" Hans responded +first with 4 taps and then with 1. The tones +c, e, g, a, (1, 3, 5, 6) were struck and the question asked, +"Which tone must be eliminated to make the complex a +chord?" In the tests in which the method had been +procedure with knowledge, this question had always been +answered correctly, but when procedure was without +knowledge the responses were first 13, a tone which does<span class="pagenum"><a name="Page_40" id="Page_40"></a>[Pg 40]</span> +not exist for Hans, then 2, a tone which was not given +in the clang to be analyzed, and finally 3, which was not +the discordant tone. Hans's far-famed musical ability +was an illusion.</p> + +<p>Taking the results of all the tests into consideration, +we find that in the case of procedure with knowledge, +90 to 100% of the responses of the various series were +correct, whereas, in those series of procedure without +knowledge 10%, at most, of the responses were correct. +Under the conditions prevailing during these latter tests, +even these 10% must be regarded as due to chance. To +be sure Mr. Grabow, a member of the school board and +an enthusiastic follower of Mr. von Osten (Zeitschrift +für Pädagogische Psychologie, Pathologie und Hygiene, +Berlin, 1904, Jahrg. 6, Heft. 6, S. 470), mentions a large +number of successful tests, which were supposedly made +in accordance with the method of procedure without +knowledge. A thorough analysis of his experiments was +not possible, because the conditions under which they +were conducted were not adequately specified. But I +have no doubt that the successful responses of the horse +were due solely to the absence of precautionary measures. +I, too, could cite a number of seemingly correct +responses which demonstrably were due to the absence +of adequate precautionary measures. I therefore repeat: +Hans can neither read, count nor make calculations. He +knows nothing of coins or cards, calendars or clocks, nor +can he respond, by tapping or otherwise, to a number +spoken to him but a moment before. Finally, he has not +a trace of musical ability.</p> + +<p>After all this experimentation it was evident that the +horse was unable to work alone, but was dependent upon +certain stimuli from its environment. The question<span class="pagenum"><a name="Page_41" id="Page_41"></a>[Pg 41]</span> +therefore arose: does the horse get these stimuli while +the question is being put, or during his responses, i. e., +during the process of tapping.</p> + +<p>If Mr. von Osten's opinion was correct, then the +process of questioning played an important part in the +success of the experiment. Of course, as he said, it was +not necessary to ask the question aloud; it was sufficient—curiously +enough—that it be inwardly spoken, thanks +to the horse's extraordinary auditory sensitivity. If, however, +conditions were made such that the auditory sense +was eliminated, then the animal would be unable to respond. +Such a theory is not quite as absurd as it might +seem at first blush. For Hansen and Lehmann have shown +that an acute auditory organ is able to respond to such +delicate stimulation as is involved in the softest whisper, +or even in the so-called nasal whisper in which the lips +are tightly closed.<a name="refanchor3"></a><a href="#ref_3" class="fnanchor">[3]</a> They have attempted thus to explain +any modes of supposed "thought-transference", +(cf. <a href="#Page_7">page 7</a>). Since experts on horses agree that the +horse has acute auditory sensitivity, Mr. von Osten +seized upon this fact and tried to establish his theory in +the following manner. No response was successfully +made on the part of the horse, he said, when the sound +waves caused by his (Mr. von Osten's) inner speech were +deflected from the ear of the horse. This was the case +when he closed nose and mouth while inwardly putting +the question, or deflected the waves from the horse's ear +by means of a placard held before his mouth while speaking, +or finally by applying lined ear-muffs to the horse's +ears. If, on the other hand, he closed only his nose and +not his mouth while thus inwardly putting the question, +or if he held the placard so that there was a possibility of +deflecting the sounds to the horse's ear, or if the ear-<span class="pagenum"><a name="Page_42" id="Page_42"></a>[Pg 42]</span>muffs +were of too sheer a material, then Hans could hear +and answer the questions which for human ears were +inaudible. He demonstrated all this by means of experiments +and of 20 tests of the first kind, in which auditory +sensations were supposedly eliminated, 95% of the responses +were incorrect (Hans would always tap too great +a number); whereas of 28 tests of the second kind, not +a single answer was wrong, just as had been predicted. +Now I have repeated both kinds of tests, but have always +found some correct responses in those cases in +which the horse, supposedly, was unable to hear, a thing +which greatly astonished Mr. von Osten. In fact, the +responses of the horse were quite as correct when I did +not even whisper the question inwardly. It was quite +clear that putting the question in any form whatever was +wholly unnecessary. Mr. von Osten's demonstrations to +the contrary, which were based upon erroneous physical +principles, are to be explained as cases of vivid autosuggestions, +(but of this, more in <a href="#CHAPTER_V">Chapter V</a>). After +all this experimentation, it was manifest that the cue was +not given to the horse while the question was being put; +it occurred, therefore, at some time during the process of +tapping. But by means of which sense organ was it +received by the horse?</p> + +<p>We began by examining the sense of vision, and in the +following manner. Blinders were applied, and it is +worthy of mention that Hans made no attempt to resist. +The questioner stood to the right of the horse, so that +the animal knew him to be present and could hear, but +not see him. Hans was requested to tap a certain number. +Then the experimenter would step forward into the +horse's field of vision and would put the same problem +again. Since, in the tests of the first kind, Hans would<span class="pagenum"><a name="Page_43" id="Page_43"></a>[Pg 43]</span> +always make the most strenuous efforts to get a view of +the questioner, and since he would rave and tear at the +lines whenever the attempt was made to tie him,—a thing +which he had never done hitherto,—it was impossible to +determine in some cases whether or not he had seen the +questioner during the process of tapping. I am using, +therefore, in the following exposition, besides the two +categories of "not seen" and "seen", a third which I +have called "undecided". A total of 102 tests were made +in which large blinders were used. In 35 of these, the +experimenter certainly was "not seen" in 56 cases he +was "seen" and the remaining 11 are "undecided". +Under the first of these categories 6% of Hans's answers +were correct (i. e. only two), under the second head 89% +were correct and under the third 18% were right. In +other words, the horse was at a loss the moment he was +prevented from seeing the questioner; whereas his responses +were nearly always correct when the experimenter +was in sight, certain proof that the horse's failures +are to be attributed to the elimination of visual stimuli +and not to the general inconvenience occasioned by the +blinders. It is evident therefore, that the horse required +certain visual stimuli or signs in order to make a correct +response.<a name="FNanchor_H_8" id="FNanchor_H_8"></a><a href="#Footnote_H_8" class="fnanchor">[H]</a></p> +<span class="pagenum"><a name="Page_44" id="Page_44"></a>[Pg 44]</span> +<p>Such unequivocal results, however, were only obtained +after we had provided blinders of sufficient size (15 × 15 +centimeters). Mr. von Osten believing that the horse +would not suffer these to be applied, had at first proposed +other measures. He held a slate before his face. Some +of the horse's responses were right, others wrong. The +tests were repeated and were successful as long as I, myself, +held the slate before my face, but not a single one +of the responses was correct when another would attempt +to hold the slate before me. Mr. von Osten then brought +forth a kind of bolster which he fastened on the right +side of the horse's face,—the side which was turned toward +the questioner. But this also gave uncertain results. +Finally he agreed to apply blinders. But these +were much too small and projected at a great angle from +the head (Mr. von Osten had cut the straps, for he +thought they worried the animal). The result was that +only the posterior part of the horse's normal field of vision +was obstructed. Therefore, one could never be quite +sure whether Hans, who—it will be borne in mind—made +every attempt to see the questioner, had not perhaps after +all been able to peer over the edge of the blinder. The +number of "undecided" tests, therefore, became very +great. Of 108 tests, only 25 could be placed in the<span class="pagenum"><a name="Page_45" id="Page_45"></a>[Pg 45]</span> +category of "not seen", 44 in the "seen", and 39, i. e., +a third of the total, in the "undecided." The percentage +of correct answers for these three categories were, respectively: +24%, 82% and 72%. Here we have once more +approximately the same ratio between the categories of +"seen" and "not seen" as in the case of the tests with +the smaller blinders. If we were to count the cases +which we had put under the head of "undecided," in the +same category as those in which vision had been excluded—as +Mr. von Osten had done—then one would +have been led to the conclusion that the horse did not +need visual signs. Several observers had thus been led +astray: e. g., General Zobel writes in the "National-Zeitung" +(Aug. 28, 1904), that upon request Mr. von +Osten had covered Hans's right eye "by means of some +sort of blinder, so that he was unable to see his instructor", +and that Hans did not fail to respond correctly. +We evidently have here to do with the unreliable +bolster mentioned above. Furthermore, Mr. Schillings +made a number of tests with the small blinders, in which +50% of the answers were correct, and probably in the +same manner were obtained the results published in one +of the daily papers (the "Berliner Tageblatt", Dec. 12, +1904), several days after the publication of the December +report, and reading as follows: "Tests have been made +upon Hans with blinders over his eyes and it is to be +noted that, in spite of these, he still responds correctly." +Mention is also made of the experiments noted in <a href="#SUPPLEMENT_III">Supplement +III (page 257)</a>, in which Mr. von Osten hid behind +the questioner and merely encouraged the animal +by occasional exhortations, but it is not possible to say +with any degree of certainty in how far he was really +hidden from the horse's view.</p><span class="pagenum"><a name="Page_46" id="Page_46"></a>[Pg 46]</span> + +<p>I would add that the horse—in so far as it was at all +possible to decide—never looked at the persons or the objects +which he was to count, or at the words which he +was to read, yet he nevertheless gave the proper responses. +But he would always make the most strenuous efforts to +see the questioner. (See <a href="#Page_43">page 43</a>). I would furthermore +add that several experiments, in which Mr. von +Osten and the horse were separated from each other by +means of the canvas tent, failed completely, and that, on +the other hand, all tests were successful in which the questioner +was present in the feed-room and the door between +this and the horse's stall was opened wide enough for him +to be seen by the horse. I would also mention that toward +evening the responses became less and less accurate. +The conclusion that visual stimuli were here operative +cannot be gainsaid.</p> + +<p>It was possible, to be sure, that other senses might also +be involved, but it was certain that auditory sensations +did not enter it. This is shown by the fact that one might +remain just as silent while the horse was tapping his +answer as during the putting of the question and yet +obtain a correct response. Hans, furthermore, could +scarcely be distracted by auditory stimulations. If either +the experimenter or anyone else present sought, at a given +moment, to interrupt him by such calls as "Halt", +"Wrong", etc., while he was going through the process +of tapping, they very seldom succeeded in their attempt. +Even though such interruption did succeed in seven out +of the twenty-one cases in which it was tried, the assumption +is well grounded that the success was due entirely +or almost entirely to minimal movements involuntarily +executed by those attempting the interruption. It is to +such minimal movements that the horse, as we shall<span class="pagenum"><a name="Page_47" id="Page_47"></a>[Pg 47]</span> +see later, promptly reacted. When the experimenter +(Pfungst), himself, made the interjections, which certainly +should have been more effective, we found that the +horse was actually disturbed in only two of the fourteen +cases; and finally in ten consecutive cases of attempted +interruption not a single one was successful. There was +almost a complete absence of any ear movements on the +part of the horse, a fact in which I have been borne out +by Mr. Henry Suermondt, the distinguished horseback +rider. Indeed, I cannot recall that Hans ever turned his +ears toward me, a fact which is strikingly curious in the +case of a horse so attentive and so spirited in temper.</p> + +<p>Finally, I might also mention that the breathing of the +experimenter in no wise influenced the outcome of the +experiment. Whether he held his breath or breathed on +the leg or body of the horse, made no difference.</p> + +<p>Investigations of the other senses became needless, for +I had, in the meantime, succeeded in discovering the essential +and effective signs in the course of my observations +of Mr. von Osten. These signs are minimal movements +of the head on the part of the experimenter. As +soon as the experimenter had given a problem to the +horse, he, involuntarily, bent his head and trunk slightly +forward and the horse would then put the right foot forward +and begin to tap, without, however, returning it +each time to its original position. As soon as the desired +number of taps was given, the questioner would make a +slight upward jerk of the head. Thereupon the horse +would immediately swing his foot in a wide circle, bringing +it back to its original position. (This movement, +which in the following exposition we shall designate as +"the back step", was never included in the count.)<span class="pagenum"><a name="Page_48" id="Page_48"></a>[Pg 48]</span> +Now after Hans had ceased tapping, the questioner would +raise his head and trunk to their normal position. This +second, far coarser movement was not the signal for the +back-step, but always followed it. But whenever this +second movement was omitted, Hans, who had already +brought back his foot to the original position and had +thereby put it out of commission, as it were, would give +one more tap with his left foot.</p> + +<p>If it was true that these movements of the questioner +guided the horse in his tapping, then the following must +be shown: First, that the same movements were observed +in Mr. von Osten in every case of successful response; +secondly, that they recurred in the same order or with +only slight individual changes in the case of all who were +able to obtain successful responses from the horse, and +that they were absent or occurred at the wrong time in +all cases of unsuccessful response. Furthermore, it was +observed that it was possible to bring about unsuccessful +reactions on the part of the horse as soon as the movements +were voluntarily suppressed, and conversely, that +by voluntarily giving the necessary signs the horse might +be made to respond at pleasure; so that anyone who possessed +the knowledge of the proper signs could thereby +gain control over the process of response on the part of +the horse. These requirements have all been fulfilled, as +we shall see in the following pages.</p> + +<p>With regard to the regular recurrence of the movements +noticed in the case of Mr. von Osten, I was, after +some practice, able to note carefully their peculiar characteristics. +This was rather difficult, not only on account +of their extreme minuteness, but also because that very +vivacious gentleman made sundry accompanying move<span class="pagenum"><a name="Page_49" id="Page_49"></a>[Pg 49]</span>ments +and was constantly moving back and forth. To +abstract from these the essential and really effective +movements was truly difficult. It was much easier to +observe these movements in the case of Mr. Schillings, +probably on account of the fewer accompanying movements +and perhaps on account of their greater distinctness. +Usually he would raise the entire trunk a trifle, so +that the movements could be noticed from behind. Besides +these, I had an opportunity to observe the Count +zu Castell, Mr. Hahn and the Count Matuschka. All +three made the same movements, though somewhat more +minutely than Mr. Schillings, yet none was as slight as +those of Mr. von Osten.<a name="FNanchor_I_9" id="FNanchor_I_9"></a><a href="#Footnote_I_9" class="fnanchor">[I]</a> I further noticed that Count +Matuschka and Mr. Schillings often showed a tendency +to accompany every tap of the horse with a slight nod +of the head, the last being accompanied by a more pronounced +nod and then followed by the upward jerk of the +head, in other words, they beat time with the horse. In +the case of the last three mentioned, for whom the horse +responded far less effectively than for Mr. von Osten or +Mr. Schillings, belated or precipitate jerks would frequently +occur. This was found to be true in the case of +all other persons who had failed to elicit adequate re<span class="pagenum"><a name="Page_50" id="Page_50"></a>[Pg 50]</span>sponses +from the horse. Often, in both cases, a complete +absence of any kind of minimal movement had been +noted. The accuracy of these observations in the case +of Mr. von Osten is attested by Mr. Stumpf and Mr. von +Hornbostel, and by these same gentlemen and Prof. F. +Schumann in the case of Mr. Schillings and myself. +They also found these movements to be most minute in +the case of Mr. von Osten. In my case also they pronounced +them "minimal, and often quite imperceptible". +All other persons who have seen me work with the horse, +but who were not familiar with the nature of these movements, +never perceived them, no matter how closely they +observed me.</p> + +<p>Since the doubt was expressed that these movements +did not precede but followed closely upon the back-step of +the horse (i. e., that an error with regard to the time-element +was involved), it became important that time +measurements be taken. This was done in the following +manner: The questioner asked the horse to tap numbers +from 5 to 20, seldom higher. He purposely refrained +from pronouncing the number, but recorded it after each +test had been completed. This was a matter of indifference +to the horse (see <a href="#Page_42">page 42</a>), and had the advantage +that the measurement was not influenced by knowledge +on the part of the time-keeper. Two observers were +required, one watching the horse, the other the questioner. +Both observers had fifth-second stop-watches. The larger +face of this watch shows the fifth-second and a hand +on the smaller face indicates the minute. By pressing +upon the stem the watch may be set in motion at any +moment desired, and by pressing it once more it may +be instantly stopped, and the time <a name="tn_png_57"></a><!--TN: "elasping" changed to "elapsing"-->elapsing between<span class="pagenum"><a name="Page_51" id="Page_51"></a>[Pg 51]</span> +the setting in motion and the stopping may be read on the +face. By pressing upon the stem a third time the hands +are brought back to zero, and the watch is ready for +another test. At a moment agreed upon beforehand—usually +the third tap of the horse—both observers started +their watches. Practice tests had shown that this could +be done with all the accuracy necessary in this case. As +soon as the observer of the questioner noticed the latter's +head movement he stopped his watch, and as soon as the +observer of the horse noticed the latter's back-step he +stopped his watch. Since the movement of the horse's +foot does not occur as a jerk, but is of greater extent than +a jerk would be, it was agreed that the observer was to +stop the watch as soon as he recognized the back-step as +such, not when the foot was being raised from the +ground, because it was not then evident whether the horse +would bring it back to the original position or whether +he was preparing to give another tap, nor when he had +brought his foot completely back, but at the moment in +which it was evident that the horse intended to make the +back-step. Experimentation had shown that an agreement +as to this moment was possible. A tap with the +left foot, which might possibly follow upon the back-step, +could be left out of account. The difference in time between +the two watches would show the time between the +head-jerk of the questioner and the back-step of the +horse,<a name="FNanchor_J_10" id="FNanchor_J_10"></a><a href="#Footnote_J_10" class="fnanchor">[J]</a> and if the back-step was indeed a reaction upon<span class="pagenum"><a name="Page_52" id="Page_52"></a>[Pg 52]</span> +the head-jerk, then the watches would have to show a later +time for the back-step than for the head-jerk.</p> + +<p>Measurements of this kind were taken for Mr. von +Osten, Mr. Schillings and myself. In the case of the +first two it was taken without any knowledge on their +part. They did not even know that they were being observed, +having been told that the measurements were for +the sake of determining the horse's rate. In my case, to +be sure, the time could not be taken without my knowledge. +I succeeded, however, in eliminating the effect of +this knowledge on my part. (Cf. pages <a href="#Page_88">88</a> and <a href="#Page_145">145</a>.) +Since the results obtained in the case of Mr. Schillings +quite agree with those obtained in my case, it is evident +they may be considered as being of equal value.</p> + +<p>With regard to the number of tests the following table +may be referred to. The first vertical column gives the<span class="pagenum"><a name="Page_53" id="Page_53"></a>[Pg 53]</span> +name of the questioner, i. e. the person operating with +the horse. The four other columns give the number of +tests made upon each of these. The name of the person +who made the observation in each series is indicated at +the head of the column. It is unnecessary to give the +name of the observer of the horse, for the only difficulty +lay in the observation of the questioner. The numerals +I and II indicate two series taken at different times.</p> + + +<div style="font-size:.8em;"> +<table border="0" width="100%" cellpadding="15" cellspacing="4" summary="Test Result Table 2" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;border-top:1px solid;border-bottom:1px solid; +border-collapse:collapse;"> +<tr valign="top"> +<td width="36%" style="border-bottom:1px solid;"> </td> +<td width="16%" align="center" colspan="2" style="border-bottom:1px solid;border-left:1px solid;">v. H.</td> +<td width="16%" align="center" colspan="2" style="border-bottom:1px solid;border-left:1px solid;">Pf.</td> +<td width="16%" align="center" colspan="2" style="border-bottom:1px solid;border-left:1px solid;">Schu.</td> +<td width="16%" align="center" colspan="2" style="border-bottom:1px solid;border-left:1px solid;">St.</td> +</tr> +<tr valign="top" style="border-bottom:1px solid;"> +<td width="36%" align="center" style="border-bottom:1px solid;">Questioner.</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">I</td> +<td width="8%" align="center" style="border-bottom:1px solid;">II</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">I</td> +<td width="8%" align="center" style="border-bottom:1px solid;">II</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">I</td> +<td width="8%" align="center" style="border-bottom:1px solid;">II</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">I</td> +<td width="8%" align="center" style="border-bottom:1px solid;">II</td> +</tr> +<tr valign="top"> +<td width="36%" align="left" style="border-bottom:1px solid;">v. Osten</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">9</td> +<td width="8%" align="center" style="border-bottom:1px solid;">15</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">34</td> +<td width="8%" align="center" style="border-bottom:1px solid;">17</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">-</td> +<td width="8%" align="center" style="border-bottom:1px solid;">—</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">8</td> +<td width="8%" align="center" style="border-bottom:1px solid;">27</td> +</tr> +<tr valign="top"> +<td width="36%" align="left" style="border-bottom:1px solid;">Schillings</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">-</td> +<td width="8%" align="center" style="border-bottom:1px solid;">—</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">19</td> +<td width="8%" align="center" style="border-bottom:1px solid;">17</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">6</td> +<td width="8%" align="center" style="border-bottom:1px solid;">16</td> +<td width="8%" align="center" style="border-bottom:1px solid;border-left:1px solid;">-</td> +<td width="8%" align="center" style="border-bottom:1px solid;">—</td> +</tr> +<tr valign="top"> +<td width="36%" align="left">Pfungst</td> +<td width="8%" align="center" style="border-left:1px solid;">6</td> +<td width="8%" align="center">13</td> +<td width="8%" align="center" style="border-left:1px solid;">—</td> +<td width="8%" align="center">—</td> +<td width="8%" align="center" style="border-left:1px solid;">-</td> +<td width="8%" align="center">—</td> +<td width="8%" align="center" style="border-left:1px solid;">9</td> +<td width="8%" align="center">—</td> +</tr> +</table> +</div> + + +<p>We have omitted from this table several tests in which +the observer of the questioner noticed no head jerks +whatever, and therefore could not arrest his stop-watch, +although the horse responded correctly. Four tests of +this kind were made by Mr. von Hornbostel, two by Mr. +Pfungst, two by Mr. Schumann and five by Mr. Stumpf. +In the case of Mr. Pfungst the horse gave the unusually +high number of fifty taps. The attention of the observer +had been taxed too long and had failed him (two seconds +is the most favorable time). The head-jerk of Mr. von +Osten evidently occurred during a lapse in Mr. Pfungst's +attention and therefore remained unnoticed.</p><span class="pagenum"><a name="Page_54" id="Page_54"></a>[Pg 54]</span> + +<div style="font-size:.8em;"> +<table border="0" width="100%" cellpadding="10" cellspacing="2" summary="Test Result Table 2" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;border-top:1px solid;border-bottom:1px solid; +border-collapse:collapse;"> +<tr valign="top"> +<td width="20%" style="border-bottom:1px solid;"> </td> +<td width="20%" align="center" colspan="2" style="border-bottom:1px solid;border-left:1px solid;">v. H.</td> +<td width="20%" align="center" colspan="2" style="border-bottom:1px solid;border-left:1px solid;">Pf.</td> +<td width="20%" align="center" colspan="2" style="border-bottom:1px solid;border-left:1px solid;">Schu.</td> +<td width="20%" align="center" colspan="2" style="border-bottom:1px solid;border-left:1px solid;">St.</td> +</tr> +<tr valign="top" style="border-bottom:1px solid;"> +<td width="20%" align="left" style="border-bottom:1px solid;">Questioner.</td> +<td width="10%" align="center" style="border-bottom:1px solid;border-left:1px solid;">I</td> +<td width="10%" align="center" style="border-bottom:1px solid;">II</td> +<td width="10%" align="center" style="border-bottom:1px solid;border-left:1px solid;">I</td> +<td width="10%" align="center" style="border-bottom:1px solid;">II</td> +<td width="10%" align="center" style="border-bottom:1px solid;border-left:1px solid;">I</td> +<td width="10%" align="center" style="border-bottom:1px solid;">II</td> +<td width="10%" align="center" style="border-bottom:1px solid;border-left:1px solid;">I</td> +<td width="10%" align="center" style="border-bottom:1px solid;">II</td> +</tr> + +<tr valign="bottom"> +<td align="right">R.</td> +<td align="right" style="border-left:1px solid;">44%</td> +<td align="right">60%</td> +<td align="right" style="border-left:1px solid;">62%</td> +<td align="right">88%</td> +<td align="center" style="border-left:1px solid;">—</td> +<td align="center">——</td> +<td align="right" style="border-left:1px solid;">0%</td> +<td align="right">48%</td> +</tr> +<tr valign="middle"> +<td align="left">V. Osten.</td> +<td align="right" style="border-left:1px solid;"> </td> +<td align="right"> </td> +<td align="right" style="border-left:1px solid;"> </td> +<td align="right"> </td> +<td align="center" style="border-left:1px solid;"> </td> +<td align="center"> </td> +<td align="right" style="border-left:1px solid;"> </td> +<td align="right"> </td> +</tr> +<tr valign="Top"> +<td align="right" style="border-bottom:1px solid;">W.</td> +<td align="right" style="border-bottom:1px solid;border-left:1px solid;">56%</td> +<td align="right" style="border-bottom:1px solid;">20%</td> +<td align="right" style="border-bottom:1px solid;border-left:1px solid;">12%</td> +<td align="right" style="border-bottom:1px solid;">0%</td> +<td align="center" style="border-bottom:1px solid;border-left:1px solid;">—</td> +<td align="center" style="border-bottom:1px solid;">——</td> +<td align="right" style="border-bottom:1px solid;border-left:1px solid;">100%</td> +<td align="right" style="border-bottom:1px solid;">22%</td> +</tr> + +<tr valign="bottom"> +<td align="right">R.</td> +<td align="right" style="border-left:1px solid;">100%</td> +<td align="right">92%</td> +<td align="right" style="border-left:1px solid;">—</td> +<td align="right">——</td> +<td align="center" style="border-left:1px solid;">—</td> +<td align="center">——</td> +<td align="right" style="border-left:1px solid;">100%</td> +<td align="right">—</td> +</tr> +<tr valign="middle"> +<td align="left">Pfungst.</td> +<td align="right" style="border-left:1px solid;"> </td> +<td align="right"> </td> +<td align="right" style="border-left:1px solid;"> </td> +<td align="right"> </td> +<td align="center" style="border-left:1px solid;"> </td> +<td align="center"> </td> +<td align="right" style="border-left:1px solid;"> </td> +<td align="right"> </td> +</tr> +<tr valign="Top"> +<td align="right" style="border-bottom:1px solid;">W.</td> +<td align="right" style="border-bottom:1px solid;border-left:1px solid;">0%</td> +<td align="right" style="border-bottom:1px solid;">0%</td> +<td align="right" style="border-bottom:1px solid;border-left:1px solid;">—</td> +<td align="right" style="border-bottom:1px solid;">——</td> +<td align="center" style="border-bottom:1px solid;border-left:1px solid;">—</td> +<td align="center" style="border-bottom:1px solid;">——</td> +<td align="right" style="border-bottom:1px solid;border-left:1px solid;">0%</td> +<td align="right" style="border-bottom:1px solid;">—</td> +</tr> + +<tr valign="bottom"> +<td align="right">R.</td> +<td align="right" style="border-left:1px solid;">——</td> +<td align="right">—</td> +<td align="right" style="border-left:1px solid;">74%</td> +<td align="right">100%</td> +<td align="center" style="border-left:1px solid;">83%</td> +<td align="center">100%</td> +<td align="right" style="border-left:1px solid;">——</td> +<td align="right">—</td> +</tr> +<tr valign="middle"> +<td align="left">Schillings.</td> +<td align="right" style="border-left:1px solid;"> </td> +<td align="right"> </td> +<td align="right" style="border-left:1px solid;"> </td> +<td align="right"> </td> +<td align="center" style="border-left:1px solid;"> </td> +<td align="center"> </td> +<td align="right" style="border-left:1px solid;"> </td> +<td align="right"> </td> +</tr> +<tr valign="Top"> +<td align="right" style="border-bottom:1px solid;">W.</td> +<td align="right" style="border-bottom:1px solid;border-left:1px solid;">——</td> +<td align="right" style="border-bottom:1px solid;">—</td> +<td align="right" style="border-bottom:1px solid;border-left:1px solid;">5%</td> +<td align="right" style="border-bottom:1px solid;">0%</td> +<td align="center" style="border-bottom:1px solid;border-left:1px solid;">17%</td> +<td align="center" style="border-bottom:1px solid;">0%</td> +<td align="right" style="border-bottom:1px solid;border-left:1px solid;">——</td> +<td align="right" style="border-bottom:1px solid;">—</td> +</tr> +</table> +</div> + + +<p>The results of the experiments are given in the second +table. The general arrangement corresponds to that of +the first table. Even though the absolute number of tests +was small, yet for the sake of giving a better general +view, all values are given in percentages. The tests in +which the movement of the questioner had preceded that +of the horse—as had been anticipated—are recorded +under "R" (right); under "W" (wrong), we have +recorded those cases in which the testimony of the stop-watches—contrary +to our expectation—indicated that the +reverse order prevailed. Finally, those cases which would +complete the 100%, i. e. those in which the watches indicate +simultaneity of the movements in question, are not +recorded.</p> + +<p>From this table we may note the following: The time-measurements +for Mr. Schillings and Mr. Pfungst are +quite in agreement and go to show that the order in time +of the head movement of the questioner and the back-<span class="pagenum"><a name="Page_55" id="Page_55"></a>[Pg 55]</span>step +of the horse was exactly what had been expected. +The few contradictory cases which occur in Series I of +the observations upon Mr. Schillings are to be accounted +for by the fact that he was here for the first time the +subject of observation, whereas the recorded time-measurements +in the case of Mr. Pfungst had been preceded +by a number of practice tests. The results of the measurements +taken in the case of Mr. von Osten were far +less satisfactory. Even if one were to allow a series containing +barely more than 50% of "right" cases as sufficient +proof of the correctness of our expectation regarding +the order of the movements of the questioner and the +horse, only three of the six series obtained with Mr. von +Osten as subject, would satisfy this expectation. However, +since four of the six series show a greater number +of cases of simultaneity (their percentage may be easily +deduced by referring to the per cent of "right" and +"wrong" cases), the proposed method would give a distorted +view, and therefore it appears that the more correct +method would be to consider simply the numerical +ratio of the "right" and "wrong" cases. Since, furthermore, +Series II shows, in every case, a decided change +which is similar for all observers (note especially +Pfungst), there can be no doubt but that practice is here +involved, and that Series II is to be regarded as the true +standard. Throughout this series we find a preponderance +of "right" cases. Therefore, the table unmistakably +confirms the expected order in time. That there were +more "wrong" cases with Mr. von Osten as subject than +with the other questioners is to be explained by the fact +that the decisive movements were far less easily observed +in this case, than in that of the other questioners. (See +<a href="#Page_49">page 49</a>.) We expect that Series III would show the<span class="pagenum"><a name="Page_56" id="Page_56"></a>[Pg 56]</span> +same results, or approximately the same results in the +case of Mr. von Osten that it did for Mr. Pfungst and +Mr. Schillings, but unfortunately he declined to act as +subject. In the meantime, however, new and decisive +proof presented itself which destroyed all possible doubt.</p> + +<p>Before adverting to it, let us consider in a few words +the reaction-time of the horse,—the time elapsing between +the final sign of the questioner and the reaction of the +horse (i. e., the back-step). Unfortunately this time cannot +be directly determined. All that can be ascertained +from our time-measurements, is the time intervening +between the moment of the head-jerk and the moment in +which the reaction of the horse is noted. (See <a href="#Page_51">page 51</a>). +This time averaged, for the 127 measurements, .45 seconds. +If we stated the unavoidable error, (obtained on +the basis of extended supplementary measurements which +it is not necessary to consider here) as .15 seconds, and +apply it to the value found above, we obtain .3 seconds +as the probable reaction-time of the horse.<a name="FNanchor_K_11" id="FNanchor_K_11"></a><a href="#Footnote_K_11" class="fnanchor">[K]</a></p> + +<p>That the tapping—as well as all other movements of the +horse—was nothing other than a reaction upon certain +visual stimuli, was proved beyond a doubt by the fact that +the voluntary execution of the head-jerk and of other +movements—which we will describe in more detail later +on,—brought about all the proper responses on the part of +the horse. Thus, artificial synthesis became the test +of the correctness of analytical observation.</p> + +<p>To elucidate; if the questioner retained the erect position +he elicited no response from the horse, say what he<span class="pagenum"><a name="Page_57" id="Page_57"></a>[Pg 57]</span> +would. If, however, he stooped over slightly, Hans would +immediately begin to tap, whether or not he had been +asked a question. It seems almost ridiculous that this +should never have been noticed before, but it is easily +understood, for as soon as the questioner gave the problem +he bent forward—be it ever so slightly—in order to +observe the horse's foot the more closely, for the foot was +the horse's organ of speech. Hans would invariably +begin to tap when I stooped to jot down some note I +wished to make. Even to lower the head a little was +sufficient to elicit a response, even though the body itself +might remain completely erect. Of thirty tests made in +this position, twenty-nine were successful. Hans would +continue to tap until the questioner again resumed a completely +erect posture. If, for instance, I stooped forward +after having told the horse to tap 13, and if I purposely +remained in this position until I had counted 20, he would, +without any hesitation, tap 20. If I asked him to add 3 +and 4, but did not move until 14 was reached, he would +tap 14. Twenty-six such tests gave similar results.</p> + +<p>The reaction of the horse upon such a signal for +stopping showed slight modifications according to the<span class="pagenum"><a name="Page_58" id="Page_58"></a>[Pg 58]</span> +time which elapsed between the last tap and the signal +for stopping. These modifications, which had hitherto +been paraded as expressions of the horse's psychical power +may be illustrated by the following schematic figures +(Figures <a href="#fig1">1</a>-<a href="#fig4">4</a>). In all of them the dotted line <i>c-d</i> represents +the ground level; <i>d</i> shows where the horse's right +forefoot was located before he began tapping; <i>a</i> and <i>c</i>, +respectively, indicate the place to which the foot is lowered +during the process of tapping. The unbroken line gives +the direction of the back-step.</p> + +<p>If Hans, having raised his foot from <i>a</i> to <i>b</i>—preparatory +to tapping,—receives the signal at or just before the +moment he lowers the foot, he immediately swings it in a +wide circle from <i>c</i> back to its original position at <i>d</i>, +(<a href="#fig1">Fig. 1</a>). As a matter of fact <i>a</i> and <i>c</i> coincide, but are +juxtaposed in the diagram for the sake of schematic +<a name="tn_png_65"></a><!--TN: Bracket removed following "utility."-->utility. This was the usual form of the back-step.</p> + +<div class="figcenter"><img src="images/figure_1.png" border="0" alt="" title="" width="700" height="311"><a name="fig1"></a> +<p class="caption smcap">Fig. 1.</p></div> + +<p>If the signal for stopping is given a little after the +last tap (<a href="#fig2">Fig. 2</a>), i. e., at the time that the foot is already +being raised for another tap, then the back-step occurs +as <i>a-b-d</i>. The horse thus gives, at the moment it receives +the signal for stopping, a changed impulse to the moving<span class="pagenum"><a name="Page_59" id="Page_59"></a>[Pg 59]</span> +foot. The curve, therefore, has a kink at <i>b</i>, and the back-step +occurs with seeming hesitancy,—Hans appears not +quite certain of his result.</p> + +<div class="figcenter"><img src="images/figure_2.png" border="0" alt="" title="" width="700" height="333"><a name="fig2"></a> +<p class="caption smcap">Fig. 2.</p></div> + +<p>If the signal be given somewhat later still (<a href="#fig3">Fig. 3</a>), i. e., +when the foot is being lowered to complete a tap, Hans is +still able to put on the brakes—as it were—and draw back +his foot before it reaches the ground. The whole process +gives the impression that the horse was just about to make +a "mistake" of one unit, but at the last moment had +bethought himself of the correct answer.</p> + +<div class="figcenter"><img src="images/figure_3.png" border="0" alt="" title="" width="700" height="333"><a name="fig3"></a> +<p class="caption smcap">Fig. 3.</p></div> + +<p>Finally, if the signal be deferred still longer, it becomes +impossible to prevent the extra tap. The back-step again +has the same form as in <a href="#fig1">figure 1</a>; Hans has made a +"mistake" in his answer by one unit too many.</p> + +<p>Conversely, if the head-jerk of the questioner occurs too +soon; i. e., at the moment the horse has raised his foot for +the final tap to the height <i>b</i>, (<a href="#fig4">Fig. 4</a>), then the tap is not +completed,—but the foot, without touching the ground, +makes the curve <i>b c<sub>2</sub> d</i>, back to its original position. +Hans has again made a "mistake" in his answer,—this +time by one unit too few.</p> + +<div class="figcenter"><img src="images/figure_4.png" border="0" alt="" title="" width="700" height="332"><a name="fig4"></a> +<p class="caption smcap">Fig. 4.</p></div> + +<p>All these variations go to show one thing: Hans never<span class="pagenum"><a name="Page_60" id="Page_60"></a>[Pg 60]</span> +knows in advance which tap is to be the final one. These +variations in his reactions occurred often without having +been intended by the questioner. But to bring them +about at will required skill, on account of the shortness of +the time involved in the reaction.</p> + +<p>Whenever the signal for stopping—which we have +just discussed—was followed by the complete erection of +the head and trunk, Hans would definitely cease tapping. +If, however, the questioner failed to assume a completely +erect position, or if he stooped forward ever so slightly, +the horse would follow the back-step of the right foot +with an extra tap of the left foot. Besides occurring in +tests in which Mr. von Osten assumed the rôle of questioner, +this fact was also noted when the Count zu Castell +and Mr. Schillings acted as subjects. Since the extra +tap just mentioned was not given like the others with the +right foot forward, but with the left foot upon the spot, +it was possible for the horse to execute it with a greater +show of energy. This simulated a high degree of mental +certainty on the part of the horse, as if he wished to +indicate that this was the correct solution of the problem +and it would have to stand. In spite of all this, many<span class="pagenum"><a name="Page_61" id="Page_61"></a>[Pg 61]</span> +errors would creep in. It was possible to prolong this +extra tap and thus make it appear more dilatory. We +need hardly add that henceforth it was within the power +of the experimenter to have the tapping executed entirely +with the right foot or with the final extra tap of the left +foot. Hitherto the view had been current that this lay +solely within the pleasure of the horse.</p> + +<p>If the questioner still inclined forward, still remained +in the bent posture after Hans had given the final tap +with his left foot, the horse would immediately begin to +tap once more with his right foot, which had, in the meantime, +become ready for further action. If the head jerk +was then made, Hans would bring his right foot back, +give the extra tap with his left foot, then resume tapping +with the right and thus continue until the questioner once +more resumed the erect posture. Thus the horse on one +occasion when I wished him to tap 100, gave—contrary +to my desire—the following response; 39 with the right +foot, 1 with the left, 24 with the right, 1 with the left, 35 +with the right, and 1 with the left. Later it became +possible for me to cause him to tap 1 right, 1 left, 1 right, +1 left, etc. I could even get him to tap exclusively with +the left foot by standing at his left rather than at his right +as had been customary with his questioners. These taps +with the left foot were executed in a far less elegant +fashion than those with the right foot, and with a great +waste of energy. Hans had become a right-handed +individual—as it were—as a result of long habit.</p> + +<p>With regard to the distance at which the experimenter +directed the horse, the following may be said: The usual +distance was one-quarter to one-half meter. This holds +for all tests hitherto described. Seventy tests which were +made for the purpose of discovering the influence of<span class="pagenum"><a name="Page_62" id="Page_62"></a>[Pg 62]</span> +change in distance showed that the reaction of the horse +upon the customary signal of the head-jerk was accurate +up to a distance of three and one-half meters. At a +distance of three and one-half to four meters there suddenly +occurred a fall of 60-70% in the number of correct +responses. At a distance of four to four and one-half +meters only one-third of the responses were correct, and +at a distance beyond four and one-half meters there were +no correct responses. The greater number of these tests +were made in our presence by Mr. von Osten, who was +under the impression that we were testing the accuracy of +the horse's hearing, whereas we were really testing the +accuracy of his perception of movements.</p> + +<p>With regard to the different positions which the experimenter +might assume with reference to the horse, the +following may be noted: The normal position was to the +right of the horse. If the experimenter stood immediately +in front of Hans, the latter's reaction would be just as +accurate, though he would always turn his head and +make desperate efforts to see the questioner, even though +he was held in short by the reins. When a position immediately +behind the horse was taken—a somewhat +dangerous proceeding, since Hans would at once begin +to kick—no response could be obtained until he succeeded +in turning far enough around to get the questioner within +view. If he was restrained from turning completely +around, he would at least turn his head,—and always to +the right. One might even turn his back upon Hans +during the tests, for the signal for stopping was not +obtained from the face of the questioner, but from a movement +of the head. The following incident will show to +what extent the horse had become accustomed to seeing +the questioner in a certain definite position. For a long<span class="pagenum"><a name="Page_63" id="Page_63"></a>[Pg 63]</span> +time I had been in the habit—without exception—of +standing close to the horse's shoulder. Mr. von Osten, +on the other hand, would stand farther back. When, on a +certain day, I assumed the latter position, the horse would +not suffer it, but would move backward until he had his +accustomed view of me.</p> + +<p>Finally we sought to discover by what movements the +horse could be made to cease tapping. We discovered +that upward movements served as signals for stopping. +The raising of the head was the most effective, though +the raising of the eyebrows, or the dilation of the nostrils—as +in a sneer—seemed also to be efficacious. However, +it was impossible for me to discover whether or not these +latter movements were accompanied by some slight, +involuntary upward movement of the head. The upward +movement of the head was ineffective only when it did not +occur as a jerk, but was executed in a circuitous form,—first +upward and then back again. Such a movement was +occasionally observed in the case of Mr. von Osten. The +elevation of the arms or of the elbow nearest the horse, or +the elevation of the entire body was also effective. Even +if a placard, with which the experimenter tried to cover +his face, were raised at a given moment, the horse would +make the back-step. On the other hand, head movements +to the right and to the left or forward and back, in fine, +all horizontal movements, remained ineffective. We also +found that all hand movements, including the "wonderfully +effective thrust of the hand into the pocket filled with +carrots", brought no response. I might also change my +position and walk forward and then backward some distance +behind the horse, but the back-step would only occur +in response to the characteristic stimulus. After what +has been said it is easy to understand how vain were Mr.<span class="pagenum"><a name="Page_64" id="Page_64"></a>[Pg 64]</span> +Schillings' attempts to disturb the horse and how naturally +he might conclude that Hans was not influenced by visual +signs. Mr. Schillings simply did not know which signs +were effective.</p> + +<p>While the horse could thus be interrupted in the process +of tapping by movements which were executed at the +level of the questioner's head, yet movements below this +level had the opposite effect. If Hans showed that he +was about to cease tapping before it was desired, it was +possible to cause him to continue by simply bending forward +a trifle more. The greater angle at which the +questioner's trunk was now inclined caused the horse to +increase the rate of tapping. The rule may be stated +thus: The greater the angle at which the body inclined +forward, the greater the horse's rate of tapping, and <i>vice +versa</i>. It was noticeable that whenever Mr. von Osten +asked for a relatively large number—in which case he +always bent farther forward than in the case of smaller +numbers—Hans would immediately begin to tap very +swiftly. Not being entirely satisfied with these observations, +the following more exact measurements were taken. +I asked the horse to tap 20. From 1 to 10 I held my body +at a certain constant angle, at 10 I suddenly bent farther +forward and retained this posture until 20 had been +reached. If there existed a relationship between the angle +of inclination and the rate of tapping, then the time for +the last ten taps ought to be less than for the first ten. +Of 34 such tests 31 were sucessful. The following are +two specimen series.</p> + +<p>The first series consisted of ten tests of 15 taps each. +In all cases my head was bent at an angle of 30° to the +axis of the trunk, but I constantly changed the angle of +inclination of the trunk. It was not possible to measure<span class="pagenum"><a name="Page_65" id="Page_65"></a>[Pg 65]</span> +this angle accurately on account of the rapidity with +which the whole test had to be made. I was able, however, +to differentiate between them with enough accuracy +to designate the smallest angle (about 20°) as belonging +to Grade I, and the greatest angle (about 100°) as belonging +to Grade VII. By fixing certain points in the environment, +it was possible to get approximately the same angle +repeatedly. The time from the third to the thirteenth tap +was, in all cases, taken by Prof. Stumpf by means of a +stop-watch. The tests were taken in the following +order:</p> + + +<div style="font-size:.8em;"> +<table border="0" width="80%" cellpadding="2" cellspacing="0" summary="Test Result Table 3" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> +<tr valign="top"> +<td align="left" width="37%">Grade of inclination:</td> +<td align="center" width="7%">I</td> +<td align="center" width="7%">VI</td> +<td align="center" width="7%">II</td> +<td align="center" width="7%">II</td> +<td align="center" width="7%">IV</td> +<td align="center" width="7%">V</td> +<td align="center" width="7%">VI</td> +<td align="center" width="7%">VII</td> +<td align="center" width="7%"> </td> +</tr> +<tr valign="top"> +<td align="left" width="37%">Time for 10 taps:</td> +<td align="center" width="7%">5.2</td> +<td align="center" width="7%">4.6</td> +<td align="center" width="7%">5.0</td> +<td align="center" width="7%">5.0</td> +<td align="center" width="7%">4.8</td> +<td align="center" width="7%">4.8</td> +<td align="center" width="7%">4.6</td> +<td align="center" width="7%">4.4</td> +<td align="left" width="7%">sec</td> +</tr> +</table> +</div> + + +<p>From this series it will be seen that in the case of the +same angle of inclination (II and VI were repeated and +III was omitted) the same rate obtained in the tapping. +In two other tests I constantly increased the angle of +inclination during the 15 taps, and Hans gradually +increased the rate of tapping accordingly.</p> + +<p>In a second series I had the horse tap 14, five times. +I myself took the time of the taps up to 7 by means of the +stop-watch, while Prof. Stumpf took the time of the taps +from 8 to 13. At 8 I suddenly bent forward a little more +and retained this position until tap 13. The results were +as follows:</p> + +<div style="font-size:.8em;"> +<table border="0" width="65%" cellpadding="2" cellspacing="0" summary="Test Result Table 4" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> +<tr valign="top"> +<td align="center" width="10%">Taps</td> +<td align="left" width="10%">2 to 7</td> +<td align="right" width="10%">(Pf.):</td> +<td align="center" width="10%">3.2</td> +<td align="center" width="10%">2.2-2.4</td> +<td align="center" width="10%">2.4</td> +<td align="center" width="10%">2.2-2.4</td> +<td align="center" width="10%">2.4</td> +<td align="center" width="10%">seconds</td> +</tr> +<tr valign="top"> +<td align="center" width="10%">"</td> +<td align="left" width="10%">8 to 13</td> +<td align="right" width="10%">(St.):</td> +<td align="center" width="10%">2.6</td> +<td align="center" width="10%">2.0</td> +<td align="center" width="10%">2.0</td> +<td align="center" width="10%">2.2</td> +<td align="center" width="10%">2.2</td> +<td align="center" width="10%">seconds</td> +</tr> +</table> +</div> + +<p>Such good results, however, were possible only after +a number of preliminary practice tests had been made. +The experiment was especially difficult because the horse +was often on the point of stopping in the midst of a test. +This was probably due to some unintentional movement<span class="pagenum"><a name="Page_66" id="Page_66"></a>[Pg 66]</span> +on my part. In such cases I could induce him to continue +tapping only by bending forward still more, but this +effected also, as we have seen, an increase in his rate +of tapping. Such tests, of course, could not give +unambiguous results.</p> + +<p>The rate of tapping was quite independent of my rate +of counting. Thus, if I counted aloud rapidly, but bent +forward only very slightly, the horse's tapping was slow +and lagged behind my count. If I counted slowly but +bent far forward, Hans would tap rapidly and advance +beyond my count. Thus we see that his rate of tapping +was in accordance with the degree of inclination of my +body and never in accordance with the rate of my counting, +i. e., it was quite independent of every sort of auditory +stimulation.</p> + +<p>Direct observation and a comparison of the records of +the time Hans required in giving to his master responses +involving small, medium and large numbers, with the +records of the time which he required to respond to my +questions when I bent only slightly, moderately or very +far forward, proved that the increased rapidity in tapping +in the case of large numbers, which many regarded as an +evidence of high intelligence, (see <a href="#Page_20">page 20</a>), was, as a +matter of fact, brought about in the way described. The +two series (in each of which the time measured was for +10 taps) are quite in accord. The horse did not tap +faster because he had been given a large number by Mr. +von Osten, but because the latter had bent farther forward.</p> + +<p>From all this it readily appears why it was possible to +cause Hans to increase his rate of tapping but not to +decrease it. To do the latter would involve a decrease in +the angle of inclination of the body. This would neces<span class="pagenum"><a name="Page_67" id="Page_67"></a>[Pg 67]</span>sitate +the erection of the body. As we have seen, this +was the signal to which Hans reacted by ceasing to tap. +And as a matter of fact we never knew the horse to +decrease his rate of tapping in the course of any single +test, except in the case of very large numbers, and then +it was probably due to fatigue. Mr. von Osten insisted +that Hans often slowed down toward the end of a test, +"in order to obviate mistakes", but all the tests in which +he tried to demonstrate this to us, were unsuccessful. In +spite of all exhortation, Hans would tap either uniformly +or somewhat more rapidly as soon as his master—in all +probability unconsciously—bent somewhat lower. Only +once was such a test successful. Mr. von Osten—upon +our request—asked the horse to give a certain large +number. In this instance the decrease in the rate of +tapping was due to fatigue and had nothing whatever +to do with the desire on the part of the horse to avoid +error. <a name="tn_png_74"></a><!--TN: "Futhermore" changed to "Furthermore"-->Furthermore, Mr. Hahn, who had visited Hans +twenty times and had made careful notes of his observations, +corroborated my statement when he said that he +himself never noted the decrease in rate mentioned. Contrary +statements may perhaps be due to the fact that the +tense state of expectancy on the part of the observer made +the interval between the last taps appear subjectively +somewhat longer.</p> + +<p>So much for the technique of the tapping. Now a +word about the numbers which Hans tapped. (I refer +only to the results obtained in series which involved no +volitional control). The number 1 was very difficult to +get. Hans usually tapped 2 instead. Thus even in the +case of Mr. von Osten he responded five times with 2, +and only in the sixth test did he react correctly. As far +as other questioners were concerned, 1 was seldom ever<span class="pagenum"><a name="Page_68" id="Page_68"></a>[Pg 68]</span> +obtained, except in the case of Mr. Schillings and myself. +The numbers 2, 3 and 4, on the other hand, were very +easily obtained and, above all, 3 seldom failed. 3 seemed +to be the horse's favorite number and was very frequently +given instead of other numbers. Thus, one-sixth of all +the horse's incorrect responses which were given to me +were in terms of the number 3. The numbers 5 and 6 were +a little more difficult to obtain and above 10 the difficulty +increased rapidly. Indeed, I never saw Hans respond +with a number exceeding 20 to any questioner, Mr. +Schillings and Mr. von Osten excepted. I saw the nine +vain attempts of Count zu Castell to get the number 15, +and Count Matuschka's eight unsuccessful attempts to +obtain the number 16 as a response. But even with Mr. +von Osten and Mr. Schillings such failures were not +infrequent. Thus, Mr. von Osten tried five consecutive +times to obtain the number 24. I myself did not fare +any better at first. But the following table shows what +practice can do. If we compare the percentage of correct +responses (involving the numbers 1 to 7—for which alone +I have sufficient material, viz., 80 to 100 cases), obtained +in the first half of our tests, with that of the second half, +we get the following:</p> + +<div style="font-size:.8em;"> +<table border="0" width="70%" cellpadding="2" cellspacing="0" summary="Test Result Table 5" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> +<tr valign="top"> +<td align="left" width="37%">For Number:</td> +<td align="center" width="9%">1</td> +<td align="center" width="9%">2</td> +<td align="center" width="9%">3</td> +<td align="center" width="9%">4</td> +<td align="center" width="9%">5</td> +<td align="center" width="9%">6</td> +<td align="center" width="9%">7</td> +</tr> +<tr valign="top"> +<td align="left" width="37%">In first half of tests:</td> +<td align="center" width="9%">49,</td> +<td align="center" width="9%">92,</td> +<td align="center" width="9%">89,</td> +<td align="center" width="9%">86,</td> +<td align="center" width="9%">74,</td> +<td align="center" width="9%">62,</td> +<td align="center" width="9%">53%</td> +</tr> +<tr valign="top"> +<td align="left" width="37%"> " second " " :</td> +<td align="center" width="9%">92,</td> +<td align="center" width="9%">95,</td> +<td align="center" width="9%">92,</td> +<td align="center" width="9%">98,</td> +<td align="center" width="9%">97,</td> +<td align="center" width="9%">86,</td> +<td align="center" width="9%">96%</td> +</tr> +</table> +</div> + +<p>From this we see how hard it was at first to get the +number 1 and that failure was as frequent as success, and +how much easier it was on the other hand to get the +numbers 2 and 3 (and which, therefore, do not show any +great improvement in the second half of the tests). +Beyond the 3 the percentage of correct responses decreased +and the number 7 stood at the same level as the<span class="pagenum"><a name="Page_69" id="Page_69"></a>[Pg 69]</span> +number 1. In the second half of the tests, all these +differences disappeared and errors were infrequent and +seldom exceeded +1 or -1. These results of practice are +not to be accredited to the horse, but to the experimenter, +who was at first quite unskilled. This difference in results +does not appear in the case of Mr. von Osten, for his +initial practice had been had many years previous. The +values obtained in his case were very constant throughout +our experimentation and generally showed something like +90% of correct responses. To be sure, in his case also, +the number 1 was somewhat unfavorable, (79% were +correct responses). But the percentages obtained in his +case showed no improvement whatever throughout our +experimentation. We need scarcely add that with the +voluntary control of the giving of the signs, in the case at +least of such small numbers as are here discussed, no +errors, whatever, occurred.</p> + +<p>We have discussed the influence of the experimenter, +i. e., the one who asked the horse to tap; now let us consider +the influence of others present upon the horse.</p> + +<p>As a general rule, other persons had no effect upon the +horse's responses. This appears from the failure of nearly +all tests in which all of those present—with the exception +of the questioner himself—knew the number which the +horse was to tap. Even when the others concentrated +their whole attention upon the number, it profited little as +a close analysis of the 136 cases, which belong under this +head in our records, go to prove. Thus, in the presence +of a group of twenty interested persons—during the +absence of Mr. von Osten—twenty-one problems were +given to the horse, the solutions of which were known to +everyone but myself, the questioner. Result: only two +correct responses. Only when there was among the<span class="pagenum"><a name="Page_70" id="Page_70"></a>[Pg 70]</span> +spectators someone to whom the horse was accustomed to +respond or one from whom he regularly received his food, +would such an influence be effective.<a name="FNanchor_L_12" id="FNanchor_L_12"></a><a href="#Footnote_L_12" class="fnanchor">[L]</a> But such cases<span class="pagenum"><a name="Page_71" id="Page_71"></a>[Pg 71]</span> +were few. The most important were the following: +I at one time whispered a number to Hans (on the occasion +of the tests mentioned on <a href="#Page_37">page 37</a>), and Mr. von +Osten asked for it the moment I stepped aside. Hans +answered incorrectly even though I stood close beside +Mr. von Osten; I did not, however, think intently of the +number. As soon as I concentrated my attention upon +the number he promptly responded correctly. Further +cases are those mentioned on <a href="#Page_38">page 38</a>, in which the +keeper of the horse unintentionally aided in giving four +dates which were unknown to all others present, including +the questioner. This single instance shows the necessity +of the rule that during tests in which the method is that +of procedure without knowledge the solutions should be +known to no one of those present. Finally the tests made +by the September-Commission and reported in <a href="#SUPPLEMENT_III">Supplement +III (page 255)</a> may possibly belong under this head. +Since they were not followed out any further, I am unable +to render a definite judgment upon them. In most of +these tests the question itself, as put by Mr. von Osten, +was not adequately answered, but curiously enough, however, +the number which had been given to Hans in von +Osten's absence and which formed the initial number of +some mathematical operation, was tapped correctly. This +may possibly be explained by the assumption that this +initial number had been retained in the memory of some +of those present, (see <a href="#Page_149">page 149</a>, on the "perseverative +tendency"), and that the horse, since he had been working +with some of them, responded to one of those present. +Chance may have played some part also.</p> + +<p>If the questioner knew the number of taps desired, +(which was not the case with the tests hitherto discussed), +then the environment had still less influence upon the<span class="pagenum"><a name="Page_72" id="Page_72"></a>[Pg 72]</span> +horse—except that it caused occasional interruption. The +horse's responses, therefore, did not tend to become more +successful just because a number of persons were +simultaneously concentrating upon the result desired. +This was proven by the experiments which we repeatedly +made for this purpose. Only one person at a time had +any influence upon Hans. If two questioners tried to influence +the horse at the same time,—other conditions being +the same,—success would be for the one who had the +greater control over the animal when working alone with +him. Prof. Stumpf and I made the following experiment. +Both of us stood to the right of the horse, each thinking +of a number. In ten such tests Hans always tapped my +number. When Stumpf concentrated upon 5 and I upon +8, the horse responded with 8, i. e., the larger number. +When Stumpf had 7 in mind, and I had 4, the response +would be 4, i. e., the smaller number. When Stumpf +thought of number 6, and I had fixed upon none, Hans +tapped 35. He was evidently awaiting my signal. When +I went away Stumpf again demanded the number 6, and +the horse responded properly. When I returned, Stumpf's +attempts again failed. On another occasion Count +Matuschka put a number of questions, while Mr. von +Osten stood behind him. All of the horse's responses +were correct, even the one answering the question: +"How much is 7 times 7?", which was difficult on +account of the great number of taps required. I was +able to note from the direction of the horse's eyes that he +was attending only to his master and not to the Count. +On still another occasion Mr. Grabow sang two tones—the +second being the fourth of the first—and asked Hans: +"How many intervals lie between?" I was standing +erect before the horse, and was thinking intently of the<span class="pagenum"><a name="Page_73" id="Page_73"></a>[Pg 73]</span> +number 2, but without giving any voluntary sign of any +sort. Hans tapped 2, whereupon Mr. Grabow put a +number of similar questions; but I no longer thought of +the answers, and all of Hans's responses went wrong.</p> + +<p>Although Hans was not influenced by others so long as +a suitable experimenter was present, yet he might be +disturbed and under certain conditions might be led to +make the back-step in response to certain movements in +his environment. The person to whom he responded +would have to be close to the experimenter and would +necessarily have to execute a movement greater in extent +than the experimenter's. In such instances the raising of +the head, arm or trunk, was a sufficient stimulus. Thus +we made the following two series of tests. Mr. Stumpf +stood with trunk bent forward before the horse, and at +a moment decided upon beforehand, assumed an erect +position. I myself stood beside Hans and asked him to +tap. When I stood at the horse's neck, then Mr. Stumpfs +interruption was effective. When I stood at the horse's +flank, the interruption effected only a seeming hesitation, +and when I moved still farther back, the horse continued +to tap despite any attempted disturbance. In the second +series the questioner remained constantly at the right +shoulder of the horse, while the one who attempted to distract +him, changed positions. When the latter stood to +the right immediately in front of or beside the questioner, +the disturbance was effective in 10 out of 13 cases. But +when he stood back of, and to the right of, the questioner, +the attempts at disturbance were seldom successful. If +he chose a place before and to the left of the horse, there +was hardly any distraction (in 4 cases only, out of 13), +and if he stood to the left and behind the animal, he +exerted no influence whatever. Hans manifestly turned<span class="pagenum"><a name="Page_74" id="Page_74"></a>[Pg 74]</span> +his attention, almost exclusively, to the side at which the +questioner stood.</p> + +<p>That knowledge of this <i>modus operandi</i> made it +possible for those persons to get responses from the +horse, who hitherto had been unsuccessful, is shown in +the case of Mr. Stumpf when he began to control his +movements voluntarily on the basis of observations which +had been made.</p> + + +<h4><i>II. Problems which Hans solved by movements of the +head.</i></h4> + +<p>We are here concerned with the horse's head movements +upward, downward, to the right and to the left, +and also with nodding and shaking of the head to signify +"yes" and "no". We soon discovered that these experiments, +also, were successful without an oral statement +of the problem,—in other words, the auditory +stimulus was quite superfluous. The tests with the +blinders showed that Hans was lost as soon as his questioner +was out of his view, but responded adequately the +moment the questioner was in sight. Hans, therefore, +had established no idea of any sort in connection with +the terms "up", "down", etc., but in these cases, likewise, +he reacted in response to certain visual stimuli. The +nature of these stimuli I discovered at first in my observations +of Mr. von Osten and also of myself, when working +with the horse.</p> + +<p>Above all things it was necessary that the questioner, +during these tests, should stand perfectly erect. If he +stooped ever so slightly, the test was unsuccessful. If he +carefully refrained from any movement whatsoever, and +looking straight before him asked the horse, "Which<span class="pagenum"><a name="Page_75" id="Page_75"></a>[Pg 75]</span> +direction is right?" or "Which way is upward?", Hans +would execute all sorts of head movements without rhyme +or reason. It was evident that he noted that a head movement +of some kind was expected of him, but did not know +the particular one that was wanted. But if the questioner +now raised his head, Hans would begin to nod and would +continue doing so until the questioner lowered his head. +This reaction was interpreted as signifying "yes". Mr. +von Osten had always asked Hans before each of the +more difficult tests whether he had comprehended the +meaning of the problem, and was reassured only upon +seeing the horse's affirmative response. But contrary to +Mr. von Osten's expectation, Hans also responded in this +manner after a pair of ear-caps had been drawn over his +ears. In the case of the tests described at the beginning +of the chapter, in which the method was that of "procedure +without knowledge", Mr. von Osten had always +insisted that we await Hans's nod of comprehension +before proceeding. We complied; Hans nodded and—regularly +disgraced himself!</p> + +<p>When the questioner raised his head somewhat higher +than normal, Hans would throw his own upward, which +was supposed to signify "upward". A lowering of the +head on the part of the questioner was followed by a +lowering on the part of Hans, which was his form of response +for "down". For some time I was in a quandary +as to the difference between the questioner's signal for +this latter response and the one which was the signal for +the horse to begin tapping, although I had often given +both kinds unwittingly. Further experiments showed +that Hans responded with a nod of the head whenever +the questioner, while bending forward, chanced to stand +in front of, or to the side of the horse's head, but that<span class="pagenum"><a name="Page_76" id="Page_76"></a>[Pg 76]</span> +he would begin to tap in response to the same signal, +as soon as the experimenter stood farther back. The +difference in the two signals, therefore, was very slight, +and I repeatedly noted that instead of tapping, as he had +been requested, Hans would respond to the Count zu +Castell's and Mr. Schillings' questions by a nod of the +head.</p> + +<p>If, while standing in the customary position to the +right of and facing the horse, the questioner would turn +his head a little to the right—a movement which, when +seen from the horse's position, would appear to be to the +left,—Hans would turn his head to his left. But if on +the other hand the questioner would turn slightly to the +left,—i. e. seen from the horse's position, to the right,—then +Hans would turn his head to his right. And finally, +whenever the questioner turned his head first to the right, +then to the left, Hans would respond by turning first to +his left, then to his right. This, according to Mr. von +Osten, signified "zero" or "no". Since this movement +could not be executed by the experimenter while in a +stooping position, it can now readily be seen why it was +that Hans, instead of shaking his head, always began to +tap whenever a placard with "O" upon it, was shown to +him in the course of the experiments in which the +method was procedure without knowledge on the part of +the questioner. The latter expected the horse to tap, and +therefore bent forward. Like all of the horse's other forms +of response, this, too, was always unsuccessful whenever +the questioner stepped behind the animal. Although +Hans had always responded to Mr. von Osten and Mr. +Schillings, and at first also to me, by means of the +stereotyped movement of the head to the right and then +to the left to signify "zero" or "no", I later succeeded<span class="pagenum"><a name="Page_77" id="Page_77"></a>[Pg 77]</span> +in controlling my signals so as to get the inverted order +in the horse's response. In the case of Mr. Schillings and +of Mr. von Osten all of the movements just described +were very minute, and long after the movements, which +were effective stimuli for releasing the process of tapping, +were recognized, it was still exceedingly difficult to discover +them in these two gentlemen. The signal for +"zero" and "no" was relatively the most pronounced of +the group in the case of Mr. von Osten, while with Mr. +Schillings it was the least pronounced, in comparison with +his very strong "jerk". Yet in both cases Hans responded +<a name="tn_png_84"></a><!--TN: "wtih" changed to "with"-->with absolute certainty.</p> + +<p>It is now readily conceivable how it was possible to +make the horse respond to all sorts of foolish questions, +both by involuntary signs—i. e., expressions following +upon the bare imaging of the response expected,—as well +as by means of controlled signs. One could thus obtain +consecutively the answers "yes" and "no" to the same +question. Or one might ask: "Hans, where is your +head?", and Hans would bend to the earth. "And +where are your legs?" He would look at the skies. Etc.</p> + +<p>Let us examine for a moment the directives which the +horse required for the various positions. If one called +him, while he was running about the courtyard, he paid +no attention whatever, but if one beckoned to him, he +came immediately. A raising of the hand brought him +to a standstill. If one now stepped forward or pointed +one's hand in that direction, he would step forward, or +<i>vice versa</i>, he would step backward. By means of minimal +movements of the head, of the arm nearest the +horse, or of the whole body, Hans could be induced to +assume the position one desired, without touching him or +speaking a word. I noticed this quite early in the course<span class="pagenum"><a name="Page_78" id="Page_78"></a>[Pg 78]</span> +of the investigation. Once, when intending to ask the +horse to step backward to the right, I inadvertently said +"Step backward to the left!", whereupon he stepped +backward to the right. In spite of my verbal error, I had +involuntarily given him the proper directives.</p> + +<p>Finally we may note that Mr. von Osten had occasionally +asked the horse to jump or to rear. The command +in this case was: "Jump", or the question was: +"What do the horses do in the circus?". Since these +tests were just as effective when the command was given +silently, it was an indication that these, too, depended +upon visual stimuli. What was necessary to cause the +horse to step backward and then jump forward was to +step backward oneself, or make a slight movement of the +hand in that direction. If one wished to make him rear, +it might be effected by throwing the arm or head slightly +upward.</p> + + +<h4><i>III. <a name="tn_png_85"></a><!--TN: Comma removed after "Problems"-->Problems which Hans solved by approaching the +objects to be designated.</i></h4> + +<p>The method pursued in these tests was the following: +From five to eight pieces of colored cloth ½ × ¼ meters in +size were arranged in changing series upon the ground, +the interval between them being equal to the width of +one piece, or else they were hung upon a string a man's +height above the ground. This method was also employed +when placards of like size with written symbols were +used. The horse stood ten paces away and opposite the +middle of the series, while Mr. von Osten stood at his +right. Hans was asked to go and point out the cloth of +a certain color or the placard with a certain word upon it. +If the cloth lay upon the ground, Hans picked it up with<span class="pagenum"><a name="Page_79" id="Page_79"></a>[Pg 79]</span> +his mouth and carried it to the questioner. If the cloth, +like the placards, hung from the cord, he approached, +pointed it out with his nose and then backed up to his +original position. Before approaching the objects, Hans +was required to indicate, by tapping, the number of the +place in the series (counting from left to right), which +the cloth or placard occupied. Mr. von Osten never +omitted this requirement. Then the command "Go!" +was given, and Hans obeyed. (As a matter of fact, a +slight directive movement of the head or hand was just +as effective as the spoken command).</p> + +<p>The following cases, chosen in a haphazard fashion, +show that the horse's indication of the object's place in +the series, by means of tapping, was by no means a +guarantee that he would point it out correctly. Five +placards hung from the cord. Mr. von Osten asked: +"What is the position, counting from left to right, of the +placard which has the word 'aber' inscribed upon it?". +Hans answered: 3. (It was indeed the middle placard.) +Then he was commanded: "Go!". Thereupon Hans +went straight to the fourth placard. On another occasion +Hans happened to drop a brown cloth upon a black +one. His master asked him: "In which place are there +two cloths?". Hans responded correctly, "In the second +place". To the question "Which of the two is the black +one?" he also answered rightly: "The lower one". +Upon being asked to get it, he brought the white cloth.</p> + +<p>The large number and the irregularities of the errors +showed that there was no manner of intelligence involved +in the pointing out process. Thus during the two months +of our experimentation Hans was asked twenty-five times +by Mr. von Osten to bring the green cloth. Only six +times did he succeed in the first attempt, while in five<span class="pagenum"><a name="Page_80" id="Page_80"></a>[Pg 80]</span> +instances he selected an orange-colored cloth, four times +a blue, three times a white one.</p> + +<p>The fact that the errors were equally distributed over +the tests with the colored cloths and those with the +placards is strong evidence that the horse's response +involved no intellectual process, for if that were the case, +then the responses in the tests with the placards would +have been very much more difficult, for they would have +involved the ability to read, whereas the tests with the +colored cloths demanded only that a few names be +remembered. Nevertheless, the horse was as unsuccessful +in tests of one kind as he was in those of the other,—even +when Mr. von Osten acted as questioner. (50% +failures in 78 placard tests; 46% failures in 103 color +tests.)</p> + +<p>The fact that commands which were purposely +enunciated poorly, or else not spoken at all, were executed +with just as much accuracy as those given aloud, +strengthened us in our supposition. On one occasion +I placed a blank placard with the others. When I +ordered him to approach <i>tabula rasa</i>, he invariably +went to the right one. The following illustrates how he +fulfilled quite nonsensical commands. A series of blue +and green cloths lay upon the ground. Being asked +where the black, the orange, and the yellow cloths lay, +Hans shook his head energetically, i. e. they were not +there. And yet, upon being asked to bring them in the +order named, he regularly brought one of the blue ones.</p> + +<p>All this goes to show that Hans did not know the +names of the colors (to say nothing of the symbols on the +placards). It was plain that here also, as in all the +other cases, he was controlled by signs made by the +questioner, the nature of which I soon discovered. Stand<span class="pagenum"><a name="Page_81" id="Page_81"></a>[Pg 81]</span>ing +erect, Mr. von Osten always turned head and trunk +in the direction of the cloth or placard desired. Hans, +keeping his eye on his master, would proceed in that +direction. Even after he had already started out, thanks +to his large visual field one could control his direction by +turning slightly more to the right or to the left. If, +however, he had already arrived at the row of placards or +cloths, this method ceased to be effective, for then he +could no longer see the experimenter. It made no difference +whether the cloths lay on the ground, or were +suspended, like the placards.</p> + +<p>The following fact justifies the conclusion that the +bodily attitude of the questioner was the effective signal. +The more numerous the cloths, or the nearer they were +placed together, the more difficult one would expect it to +be for the horse to select the one indicated by the experimenter. +Such was indeed the case, for the number of +errors increased with the number of cloths presented.</p> + +<p>But no matter how many cloths there might be, or how +closely they might be placed, it was always possible to +indicate either end of the row, for in that case one had +merely to turn to the extreme left or the extreme right, +and might even turn beyond the row. Hans seldom +failed in these cases, whereas he made many errors when +cloths or placards within the series were wanted.</p> + +<p>To turn from the nature and number of Hans's errors, +to their distribution,—observation proved the hypothesis +that the nearer two cloths lay together, the greater was +the chance of their being mistaken one for the other. +If we designate as "error 1" all those cases in which +Hans went to cloth II instead of to cloth I, cloth III +instead of cloth II, to V instead of IV, etc., and as "error +2" when he mistook III for I, IV for II, in fine, when<span class="pagenum"><a name="Page_82" id="Page_82"></a>[Pg 82]</span>ever +he went two places too far to the right or left, and as +"error 3" whenever he went three places too far to +either side of the cloth desired, we find the following +grouping of errors:</p> + +<div style="font-size:.8em;"> +<table border="0" width="50%" cellpadding="2" cellspacing="0" summary="Test Result Table 6" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> +<tr valign="top"> +<td align="left" colspan="2">With Mr. von Osten, a total of 63 <a name="tn_png_89"></a><!--TN: Comma removed after "errors"-->errors:</td> +</tr> +<tr valign="top"> +<td align="center" width="50%">73%</td> +<td align="center" width="50%">"error 1"</td> +</tr> +<tr valign="top"> +<td align="center" width="50%">21%</td> +<td align="center" width="50%">"error 2"</td> +</tr> +<tr valign="top"> +<td align="center" width="50%">4%</td> +<td align="center" width="50%">"error 3"</td> +</tr> +<tr valign="top"> +<td align="center" width="50%">1%</td> +<td align="center" width="50%">"error 4"</td> +</tr> +<tr valign="top"> +<td align="center" width="50%">1%</td> +<td align="center" width="50%">"error 5"</td> +</tr> + +<tr valign="top"> +<td align="left" colspan="2">With Mr. Pfungst, a total of 64 <a name="tn_png_89a"></a><!--TN: Comma removed after "errors"-->errors:</td> +</tr> +<tr valign="top"> +<td align="center" width="50%">68%</td> +<td align="center" width="50%">"error 1"</td> +</tr> +<tr valign="top"> +<td align="center" width="50%">20%</td> +<td align="center" width="50%">"error 2"</td> +</tr> +<tr valign="top"> +<td align="center" width="50%">11%</td> +<td align="center" width="50%">"error 3"</td> +</tr> +<tr valign="top"> +<td align="center" width="50%">1%</td> +<td align="center" width="50%">"error 4"</td> +</tr> +<tr valign="top"> +<td align="center" width="50%">0%</td> +<td align="center" width="50%">"error 5".</td> +</tr> +</table> +</div> + + +<p>The most frequently recurring error, therefore, was the +one in which the horse, instead of going to the cloth +desired, approached the one immediately adjacent. On +<a href="#Page_79">page 79</a> I said that Hans's errors were without system, +but only in so far as it was impossible to explain them on +a basis of the colors which seemingly were mistaken one +for the other. A part of a series in which Mr. von Osten +acted as questioner may serve as an illustration. The +order given is that of the experimental series as it +occurred. Five colored cloths were used.</p> + +<div style="font-size:.8em;"> +<table border="0" width="100%" cellpadding="2" cellspacing="0" summary="Test Result Table 7" align="center" +style="margin-top:1.25em;margin-bottom:.35em;"> +<tr valign="top"> +<td colspan="3" align="center" width="34%">Color of the cloth</td> +<td colspan="6" width="66%"> </td> +</tr> +<tr valign="top"> +<td align="left" width="12%">asked for:</td> +<td align="center" width="11%">blue</td> +<td align="center" width="11%">brown</td> +<td align="center" width="11%">brown</td> +<td align="center" width="11%">brown</td> +<td align="center" width="11%">brown</td> +<td align="center" width="11%">brown</td> +<td align="center" width="11%">green</td> +<td align="center" width="11%">green</td> +</tr> +<tr valign="top"> +<td align="left" width="12%"> </td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +</tr> +<tr valign="top"> +<td align="left" width="12%">brought:</td> +<td align="center" width="11%">orange</td> +<td align="center" width="11%">orange</td> +<td align="center" width="11%">green</td> +<td align="center" width="11%">green</td> +<td align="center" width="11%">yellow</td> +<td align="center" width="11%">green</td> +<td align="center" width="11%">blue</td> +<td align="center" width="11%">orange</td> +</tr> +</table> + +<table border="0" width="100%" cellpadding="2" cellspacing="0" summary="Test Result Table 8" align="center" +style="margin-top:.35em;margin-bottom:1.25em;"> +<tr valign="top"> +<td colspan="3" align="center" width="34%">Place of cloth</td> +<td colspan="6" width="66%"> </td> +</tr> +<tr valign="top"> +<td align="left" width="12%">asked for:</td> +<td align="center" width="11%">V</td> +<td align="center" width="11%">II</td> +<td align="center" width="11%">II</td> +<td align="center" width="11%">II</td> +<td align="center" width="11%">II</td> +<td align="center" width="11%">II</td> +<td align="center" width="11%">III</td> +<td align="center" width="11%">III</td> +</tr> +<tr valign="top"> +<td align="left" width="12%"> </td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +<td align="center" width="11%">|</td> +</tr> +<tr valign="top"> +<td align="left" width="12%">brought:</td> +<td align="center" width="11%">IV</td> +<td align="center" width="11%">IV</td> +<td align="center" width="11%">III</td> +<td align="center" width="11%">III</td> +<td align="center" width="11%">I</td> +<td align="center" width="11%">III</td> +<td align="center" width="11%">V</td> +<td align="center" width="11%">IV</td> +</tr> +</table> +</div> + +<span class="pagenum"><a name="Page_83" id="Page_83"></a>[Pg 83]</span> + +<p>The interpretation of this series which it would be hard +to explain by a reference to the colors which were mistaken, +is simply this: Cloths lying near together were +regularly mistaken on the part of the horse.</p> + +<p>Experimental control of the questioner's movements +decided the question. If the questioner at first indicated +the proper direction and then turned about after the +horse had already started forward, he was as a rule misled. +When the questioner did not face the cloths at all, +but turned away at right angles, or when he turned his +back upon them, Hans was completely at sea. If, on +the other hand, the cloths were arranged, not in a row, +but in several heaps, so that one might turn to a particular +heap, but could not indicate a particular cloth, then Hans +would regularly go to the proper heap, but would always +bring forth the wrong cloth. After much persuasion Mr. +von Osten consented to make a series of these tests himself. +Hans's failures were deplorable. He would take +up first one cloth then another, turn again to the first, etc. +We would mention, however, that this apparent searching +was not done spontaneously, but in <a name="tn_png_90"></a><!--TN: "reponse" changed to "response"-->response to Mr. von +Osten's calls, such as "See there!", "The blue!", etc. +Every time Mr. von Osten called, Hans would drop the +cloth he was holding in his mouth, or he would turn away +from the one he was about to grasp, and would then try +another <a name="tn_png_90a"></a><!--TN: Comma changed to period after "one"-->one.</p> + +<p>In addition to these visual signs, the horse received +auditory signals in these tests, (as in all others in which +he was required to bring objects). As soon as the questioner +noticed that Hans was about to take up the wrong +cloth, all that was necessary to make him correct his error +was to give some sort of an exclamation, such as +"Wrong!", "Look, you!", "Blue!", etc. Hans would<span class="pagenum"><a name="Page_84" id="Page_84"></a>[Pg 84]</span> +pass on as long as the calling continued. If he was picking +up, or about to pick up, a cloth when the exclamation +was made, he would go on to the next; but if, at the time +he was on his way to a certain cloth, he would change his +direction in response to the call. If he stood before one +of the pieces at the time, but had not lowered his head, he +would pass on to the next. In all this he would adhere +to a certain routine of procedure. If he was approaching +a series from the right, then a call would cause him to +turn to the left, if he was coming from the left, he would +turn to the right. If he had approached the row of +cloths near the center, he would turn, in response to the +questioner's calls, to the left,—seldom, very seldom, to the +right. Mr. von Osten did not seem to be able to control +the responses of the horse, entirely. As a rule, but not +always, one call sufficed to make Hans pass on to the next +cloth. If too many calls were given, he would often go +too far. Loud exclamations were superfluous.</p> + +<p>These statements are not mere assertions, but are +founded upon the records of the results. The tests in +which calls were made show a larger percentage of correct +responses than do those without calls. Of a total of 103 +tests with colored cloths, which Mr. von Osten performed +for us, only 37% brought forth successful responses on +the part of the horse when visual signs were the only +directives and when there were no directions by means +of calls, whereas the total percentage of successful responses +was 54%, if we add to the above those in which +the vocal exclamations helped to bring about success. +The corresponding percentages for the total of 78 tests +with the placards were 23% and 50%. In a total of 110 +color tests I myself obtained 31% correct responses under +the first head, and 56% under the second head. In a<span class="pagenum"><a name="Page_85" id="Page_85"></a>[Pg 85]</span> +total of 59 tests with placards I succeeded in getting 31% +correct responses under the first head and 46% under the +second head. We must note that without verbal admonition +only one-third of the tests brought forth correct +responses, whereas one-half succeeded when those in +which calls were used, are added. Still, this is a relatively +poor showing. In the most favorable series that Mr. von +Osten ever obtained in our presence—and there was only +one such—50% of the responses 'without admonition' +were correct, and 90% when all the correct reactions, both +with and without admonition, were taken into account.</p> + +<p>Not all the places in the row required the same amount +of assistance by means of calls. Those positions which +needed the most help, were those which it was most +difficult to indicate to the horse by the visual sign, i. e., +the attitude of the questioner's body. We noted above +(<a href="#Page_81">page 81</a>) that the cloths at either end of the row were +less difficult to point out than those nearer the middle. +If our hypothesis holds true, we would expect that the +end cloths would involve fewer auditory signals in the +process of pointing out, and those within the row a +greater number of such signs. By way of illustration, I +will cite one series of tests in which Mr. von Osten was +questioner, chosen not because it is most conformable to +my hypothesis but because it is the longest (48 consecutive +tests with five cloths) which I have. In the upper row I +am placing the successful responses without auditory +signs, in the lower those involving both auditory and +visual signs.</p> +<div style="font-size:.8em;"> +<table border="0" width="100%" cellpadding="2" cellspacing="0" summary="Test Result Table 9" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> + +<tr valign="top"> +<td align="center" width="60%" colspan="3">Place of the cloth</td> +<td align="center" width="8%">I</td> +<td align="center" width="8%">II</td> +<td align="center" width="8%">II</td> +<td align="center" width="8%">IV</td> +<td align="center" width="8%">V</td> +</tr> +<tr valign="top"> +<td align="center" width="28%" rowspan="2">No. of sucessful<br>responses</td> +<td align="center" width="4%">}</td> +<td align="center" width="28%">visual signs only</td> +<td align="center" width="8%">5</td> +<td align="center" width="8%">2</td> +<td align="center" width="8%">1</td> +<td align="center" width="8%">2</td> +<td align="center" width="8%">4</td> +</tr> +<tr valign="top"> +<td align="center" width="4%">}</td> +<td align="center" width="28%">visual and auditory signs</td> +<td align="center" width="8%">5</td> +<td align="center" width="8%">5</td> +<td align="center" width="8%">8</td> +<td align="center" width="8%">5</td> +<td align="center" width="8%">5</td> +</tr> +</table> +</div> + +<span class="pagenum"><a name="Page_86" id="Page_86"></a>[Pg 86]</span> + +<p>We see that without verbal admonition the first and last +places are most favorable for success, the second and +fourth far less, and the middle least favorable. These +differences disappear when admonitions are introduced, +for all of the places then have the same number of correct +responses with the exception of the middle, which now has +even more than the others.</p> + +<p>One more experiment which I made will close the +discussion. The following colors were placed from right +to left: orange, blue, red, yellow, black, green. I turned +my back upon them, and therefore could guide the horse +by verbal commands only. I asked him to bring the +orange. Hans approached the yellow. I now called three +times, allowing a short interval between the calls. At the +first "Go!" he passed from the yellow to the red, at the +second from the red to the blue, and at the third from the +blue to the orange, which he then proceeded to pick up +and bring to me. I had noted this same thing in Mr. von +Osten's tests, although there, there were often other +factors entering in. By exercising the utmost precision +in facing the cloths, and by using, in addition, suitable +oral signs, I succeeded in getting Hans to bring, successively, +each one of the six cloths in the row, and without +a single error,—and all this in the presence of Mr. Schillings +who did not have the slightest notion of the secret of +my success.</p> + +<p>We need hardly say, in passing, that all that was true +of the tests with colored cloths, was also true of the tests +in which the placards were used. It was all the same to +the horse whichever was placed before him.</p> + +<p>We have thus tested all of the horse's supposed achievements. +None of them stood the critical test. It would +have been gratifying to have repeated some of the experi<span class="pagenum"><a name="Page_87" id="Page_87"></a>[Pg 87]</span>ments +and to have made Hans the object of further +psychological investigations, but unfortunately he was no +longer at my disposal after the publication of the report +of the December-Commission. Some may say that we +have had almost enough of a good thing, but we must bear +in mind that many of the tests which were carried out,—such +as those in which the method was that of "procedure +without knowledge", those in which the ear-muffs were +used, those in which distractions were introduced,—had +previously been made by other persons (see pages <a href="#Page_41">41f</a>, +<a href="#Page_45">45</a>, <a href="#Page_63">63</a>), and with other results, than ours. A more thorough +test, therefore, would have been doubly desirable.</p> + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_G_7" id="Footnote_G_7"></a><a href="#FNanchor_G_7"><span class="label">[G]</span></a> The expressions <i>questioner</i> and <i>experimenter</i> are used interchangeably +in this treatise.</p></div> + +<div class="footnote"><p><a name="Footnote_H_8" id="Footnote_H_8"></a><a href="#FNanchor_H_8"><span class="label">[H]</span></a> Throughout this treatise I am using the word "sign," or "signal," +whereas all other writers who have touched upon the Hans-problem, +have always spoken of "aids." Following von Sanden,<a name="refanchor4"></a><a href="#ref_4" class="fnanchor">[4]</a> however, I +would distinguish clearly between the two. I would designate as aids +all immediate stimulations of the horse's body (i. e. by means of contact), +which have been designed with reference to the animal's physiological +movement-mechanism in such a way that they truly 'aid' him +in the production of the required movements. I would regard as signs +on the other hand, all stimulations (whether mediate or immediate) +which are selected without especial regard to the anatomy or physiology +of the horse, and bear no inseparable relation to the thing to be done +but are associated with it at the will of the trainer. The rider's use +of reins, and control by means of leg-pressure and manner of sitting +in the saddle, and the driver's use of the lines,——all these, then +are aids. A simple pull at the reins, however, is not an aid, but a sign. +The whip may be used for giving signs as well as aids,——the latter, +when it does the work of the spur or of the pressure with the +knees, as is the case with ladies' riding-horses and in lunging. All calls +and all movements of the hand or head merely, on the part of the +trainer, are to be regarded as signs.</p></div> + +<div class="footnote"><p><a name="Footnote_I_9" id="Footnote_I_9"></a><a href="#FNanchor_I_9"><span class="label">[I]</span></a> During the tests Mr. von Osten nearly always wore a slouch hat +with a wide rim. The rim, of course, always moved with the head, and +made the movements appear on a larger scale, (in the ratio of about +3:2, as I was able to ascertain later by graphic methods). But observation +was successful, even at a distance of a meter and a half, when he +worked with head uncovered. And even if head and forehead were +covered entirely, it was still possible to note the movements by watching +the eye-brows. When Mr. Schillings and the rest of us worked +with the horse, we either went bare-headed or wore only a very small +cap.</p></div> + +<div class="footnote"><p><a name="Footnote_J_10" id="Footnote_J_10"></a><a href="#FNanchor_J_10"><span class="label">[J]</span></a> For the benefit of those who are familiar with reaction-time experiments +of this kind, I would state the following: The reaction to the +head-jerk, on account of the minuteness of the latter, was sensory +throughout, and therefore all precipitate reactions are entirely wanting. +The reaction to the back-step was, like the preceding one, a reaction +to a visual cue. (Hans's tapping was almost quite inaudible). Both +stop-watches were carefully regulated. In order to eliminate also the +constant error which might possibly arise as a result of some difference +in the functioning of their pressure-mechanism, the two watches were +always exchanged in the different series of tests, by the observer of the +man and the observer of the horse. The two time-measurements obtained +by the two observers contained, of course, the reaction-times of +the observers themselves. In order to equalize the constant error which +thereby arose, it was arranged that each observer should react alternately +now to the man, now to the horse. In order to be perfectly safe, the +reaction-times of those concerned, (von Hornbostel, Pfungst, Schumann +and Stumpf), were later determined in the laboratory by means of the +carefully regulated Hipp chronoscope. Separate determinations were +made of the reactions to the head-jerk and to an imitation of the horse's +back-step. Then the time which one observer took to react upon a +head-jerk, was compared with the reaction-times of the other observers +to the back-step. Since the greatest difference which was found in this +comparison, did not exceed one-tenth second, the results obtained in the +courtyard required no correction.</p></div> + +<div class="footnote"><p><a name="Footnote_K_11" id="Footnote_K_11"></a><a href="#FNanchor_K_11"><span class="label">[K]</span></a> See <a href="#Page_126">page 126</a> on the corresponding reaction-time in the case of man. +Similar tests have been made in the case of animals in only one instance, +and that for dogs, by E. W. Weyer.<a name="refanchor5"></a><a href="#ref_5" class="fnanchor">[5]</a> But, as might have been expected, +they did not yield any satisfactory results.</p></div> + +<div class="footnote"><p><a name="Footnote_L_12" id="Footnote_L_12"></a><a href="#FNanchor_L_12"><span class="label">[L]</span></a> Mr. Schillings, however, did succeed in making a number of tests +with the co-operation of others who had never before worked with the +horse. These tests were made under the following conditions: The +horse was standing in his stall, when Mr. Schillings and another gentleman +approached him. There was no one else present. Mr. Schillings, who +tried to remain as passive inwardly, as possible, asked his partner to +think consecutively of different numbers between one and 20, which thus +were known to him alone. Hans was then commanded by Mr. Schillings +to tap the numbers, which he did, to the great astonishment of the men, +and especially of Mr. Schillings. In like manner Mr. Sander, a staff +physician in the marine, received—so he writes me—three correct +responses to four questions which he put to the horse. It happened +also in the case of two scientific men and finally, too, in my own case +when I first came in contact with the horse, (see <a href="#Page_88">page 88</a>). The horse's +reaction was brought about in the same way in every one of these +instances. Mr. Schillings, in bending forward slightly, thereby started +the horse a-tapping, and his companion—just as innocently—interrupted +the process by means of a movement of his head, when the right number +of taps was reached. +</p><p> +I later tried similar experiments together with Mr. Hahn. I was +aware of the answer to the riddle at the time, but he was not. Mr. +Hahn stepped in front of the horse and thought intently of certain +numbers. I did the questioning, that is, I got the horse to tap. In +twelve tests Hans responded correctly in only two instances. In the +ten others he always tapped beyond the number Mr. Hahn had in +mind, e.g., 21 instead of 2, and was evidently awaiting a movement on +my part. When we exchanged rôles, Mr. Hahn doing the questioning +and I doing the "thinking," the horse would not respond at all, although +as a rule Mr. Hahn had been fairly successful in working with him +alone. I had gradually gained so much influence over the horse, that +he would scarcely attend to any one else when I was about—Mr. von +Osten hardly excepted. +</p><p> +In this connection I would prefer to avoid the term "rapport," which +may rise in the minds of many, since it has been used so much in connection +with the phenomena of hypnotism, for I would not obscure a +fact that is clear by giving it a name that is vague.</p></div> +</div> + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_88" id="Page_88"></a>[Pg 88]</span> +<h2 style="padding-bottom:1em;"><a name="CHAPTER_III" id="CHAPTER_III"></a>CHAPTER III</h2> + +<h2 style="padding-bottom:1em;">THE AUTHOR'S INTROSPECTIONS</h2> + + +<p><span class="firstwords">In</span> the preceding chapter we asked: What is it that +determines the horse's movements? Independent thinking, +or external signs?—We found that it was solely external +signs, which we described as certain postures and +movements of the questioner. Beyond a doubt these necessary +signs were given involuntarily by all the persons +involved and without any knowledge on their part that +they were giving any such signs. This is to be seen +from their statements, which cannot be cavilled at, as +well as from the fact that several of them even to-day +still doubt the correctness of the explanation which we are +here offering. I myself for some time made these involuntary +movements quite unwittingly and even after I had +discovered the nature of these movements and had thus +become enabled to call forth at will all the various responses +on the part of the horse, I still succeeded in +giving the signs in the earlier naïve involuntary manner. +It is not easy, to be sure, to eliminate at once the influence +of knowledge and to focus attention with the greatest +amount of concentration on the number desired, +rather than upon the movement which leads to a successful +reaction on the part of the horse. To some this may +appear impossible, but those who are accustomed to do +work in psychological experimentation, will not deny +the possibility of such exclusive concentration upon certain +ideas.</p><span class="pagenum"><a name="Page_89" id="Page_89"></a>[Pg 89]</span> + +<p>If we now ask: "What occurred in the mind of the +questioners, while they were giving the signs?", the answer +can be found only by way of the process which in +psychology is technically called "introspection", i. e. +observation of self. In the following we will give the +most important results of this process of self-observation, +which took place in the same period in which the observations +recorded in the preceding chapter were made.</p> + +<p>My first experiments were made while the horse was +counting or solving arithmetical problems and were as +follows: Mr. Schillings, who was alone with me in the +horse's barn, asked me to think of several numbers, maintaining +that the horse would be able to indicate them correctly +upon being asked. He stood to the right of the +horse, I stood erect and at the side of Mr. Schillings. +There was no one else present. Somewhat skeptical in +attitude, I concentrated my mind consecutively on five +small numbers. Hans tapped one of them incorrectly, +one correctly and three by one unit too many. At the +time I considered these attempts as unsuccessful and credited +some curious chance with the answers which were +correct, or nearly so. This was a mistake, for often +during the following days, and in the absence of Mr. von +Osten, the horse would give correct answers. Others, of +course, would be incorrect, and usually the mistakes +would be by one unit,—so that I soon saw that even in +the horse's errors there lay some system. It will be seen +that Hans responded to me from the very beginning, undoubtedly +because I had had the opportunity of watching +<a name="tn_png_96"></a><!--TN: Period added after "Mr"-->Mr. von Osten and Mr. Schillings and had thus patterned +my behavior after theirs. I was not at first successful in +getting the horse to respond correctly in the case of large +numbers. For in order to get complete control over the<span class="pagenum"><a name="Page_90" id="Page_90"></a>[Pg 90]</span> +horse, and, what was, as I later discovered, more to the +point, control of myself, some practice was needed. But +I was able to work with the horse quite successfully, +while I was still in the dark as to my own behavior.</p> + +<p>From the very beginning Hans responded as promptly +to those questions which I articulated merely inwardly, +as to those which were spoken aloud. That all formulation +of the question was unnecessary, however, was shown +by the following experiments. If, for example, I did not +think of any particular number until after the horse had +begun to tap, and then fixed upon 5, he would tap 5. If, +however, I told him to count to 6, but gave no further +thought to the command after he had begun tapping, I +would get an entirely wrong response. It was easy to +obtain any answer one wished to a question, simply by +focussing consciousness, with a great degree of intensity, +upon the answer desired. Thus Hans answered my question: +"How many angles has a hexagon?", first by 6, +then 2, then 27, in accordance with the numbers that came +into my mind. The animal always followed the ideas +which were in the questioner's mind, and never his words, +for it was with the former that the movements upon which +the horse depended were bound up.</p> + +<p>It was not enough, however, simply to imagine the +number desired. It was furthermore necessary that the +questioner be conscious of the moment when the horse +reached that number. Larger numbers (above 6) were +therefore, successful only when every single tap was inwardly +counted to the end. The manner of counting was +indifferent. Thus I counted 6 as follows: 1, 2, 3, 4, 5, 6, +and later: 6, 5, 4, 3, 2, 1, and then again: 6, 6, 6, 6, 6, 6. +Finally I used the Greek letters and also nonsense syllables. +And in all cases I obtained six taps, the correct<span class="pagenum"><a name="Page_91" id="Page_91"></a>[Pg 91]</span> +response. If, however, I simply counted the taps without +knowing when the desired number was reached, the responses +were always incorrect, e. g., I counted</p> + +<div style="font-size:.8em;"> +<table border="0" width="70%" cellpadding="1" cellspacing="0" summary="Test Result Table 10" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> + +<tr valign="top"> +<td align="center" width="8%">For</td> +<td align="center" width="8%">No</td> +<td align="center" width="8%">10:</td> +<td align="right" width="8%">10,</td> +<td align="right" width="8%">10,</td> +<td align="right" width="8%">10</td> +<td align="center" width="8%"> </td> +<td align="center" width="20%">continuously,</td> +<td align="center" width="8%">Hans</td> +<td align="center" width="8%">tapped</td> +<td align="center" width="8%">13,</td> +</tr> +<tr valign="top"> +<td align="center" width="8%">"</td> +<td align="center" width="8%">"</td> +<td align="center" width="8%">10:</td> +<td align="right" width="8%">1,</td> +<td align="right" width="8%">2,</td> +<td align="right" width="8%">3</td> +<td align="center" width="8%">to</td> +<td align="left" width="20%">10</td> +<td align="center" width="8%">"</td> +<td align="center" width="8%">"</td> +<td align="center" width="8%">10,</td> +</tr> +<tr valign="top"> +<td align="center" width="8%">"</td> +<td align="center" width="8%">"</td> +<td align="center" width="8%">12:</td> +<td align="right" width="8%">12,</td> +<td align="right" width="8%">12,</td> +<td align="right" width="8%">12</td> +<td align="center" width="8%"> </td> +<td align="center" width="20%"><a name="tn_png_98"></a><!--TN: Comma added after "continuously"-->continuously,</td> +<td align="center" width="8%">"</td> +<td align="center" width="8%">"</td> +<td align="center" width="8%">15,</td> +</tr> +<tr valign="top"> +<td align="center" width="8%">"</td> +<td align="center" width="8%">"</td> +<td align="center" width="8%">12:</td> +<td align="right" width="8%">1,</td> +<td align="right" width="8%">2,</td> +<td align="right" width="8%">3</td> +<td align="center" width="8%">to</td> +<td align="left" width="20%">12</td> +<td align="center" width="8%">"</td> +<td align="center" width="8%">"</td> +<td align="center" width="8%">12.</td> +</tr> +</table> +</div> + + +<p>In the case of smaller numbers, on the other hand, one +often obtained correct results without counting. In this +I am borne out by Mr. Schillings. It was merely necessary +to image vividly the number 3, or 4, or even the +name of a week-day or of a month without the number +which would indicate it. In the last of these cases the +number corresponding to the day or the month (e. g. 3 for +Tuesday, 5 for May, etc.), though not consciously presented, +still evidently lay at hand in the subconscious. +To use a popular expression, I usually had a "feeling" +when Hans had arrived at the right number.</p> + +<p>It was furthermore found that it was not only necessary +to count to, or to think of, the number desired, but +that this must take place with a high degree of tension of +expectancy—that is, a strong affective element must +enter in. The state required for a successful response +was not the mere passive expectation that the horse would +tap the number demanded of him nor the wish that he +might tap it, but rather the determination that he should +do it. An inward "Thou shalt", as it were, was spoken +to the horse. This affective state was registered in consciousness +in terms of sensation of tension in the musculature +of the head and neck, by intraorganic sensations, +and finally by a steadily rising feeling of unpleasantness. +When the final number was reached, the tension would<span class="pagenum"><a name="Page_92" id="Page_92"></a>[Pg 92]</span> +suddenly be released, and a curious feeling of relaxation +would ensue. I have made a series of tests to determine +the most favorable degree of tension in expectation. It +was possible to distinguish with certainty, three degrees +of tension besides the state of utter relaxation,—all of +which I measured by means of the differences in the sensations +of tension. In cases of tension of the first degree +(greatest concentration) the responses were usually correct, +a few, however, were lacking by one unit. There +was therefore in the latter instance a premature release +of inner tension. In cases of tension of the second degree +all answers were correct except a very few which +were too great by one unit. In cases of tension of the +third degree, many answers were wrong, and usually by +several units too many. I wished to have the horse tap +10, with the lowest degree of concentration. He tapped +13, then in a repetition of the test, 12. I thereupon increased +the tension, Hans then tapped 8. I decreased the +tension once more, but so that it was somewhat greater +than at first. Hans tapped 10 correctly. At another time +I tried to have him tap the number 5, with a low degree +of tension. He tapped 6. I intensified expectation and +Hans tapped 4. I again decreased it, and he tapped 5, +<i>comme il faut</i>. Apparently, therefore, the most favorable +degree of tension was one between the first and second,—the +latter being the least favorable. After some practice +a lesser degree than was used in the beginning sufficed +to evoke adequate reactions. The flow of nervous +energy to the motor centers of the brain evidently became +facilitated through practice. It will be easy to understand +why the first days of experimentation caused intense +headaches, which later never occurred.</p> + +<p>Whenever, in the foregoing, we spoke of a certain de<span class="pagenum"><a name="Page_93" id="Page_93"></a>[Pg 93]</span>gree +of concentration which had to be attained, it is not +to be understood that the same tension had to be maintained +throughout the test, from the horse's first tap to +his last. But rather, that it began with a low degree, and +gradually increased as the final unit of the count was being +approached. It may best be represented by a curve whose +maximum represents that degree of tension which we +have been discussing. The rise to this maximum which, +when attained, was followed by a sudden fall, did not +always occur in the same manner. Three types of curve +may be distinguished, which were first discovered in +purely empirical fashion, and later reproduced voluntarily +for purposes of experimentation by diagramming +before each test the intricate curve of the varying degrees +which the intensity of concentration was to assume. The +types may be described as follows:</p> + +<p>I. Here the tension curve rises steadily from beginning +to end. This type preponderates in the case of small +numbers. Thus, when I asked the horse: "How much is +2 plus 4?", the tension increased slowly with every tap +from the moment I began counting, until the final tap +was reached, when it was again relaxed. Externally this +relaxation is noticeable as a slight jerk.</p> + +<p>II. In this case the curve does not rise at an equal rate, +but rather more slowly at the beginning and later undergoes +a sudden increase, or the tension increases immediately +at the beginning, remains constant for some time +and then ascends to the maximum. This curve is the +rule in the case of large numbers and evidently means +economy of physical energy, for experience soon taught +that a steady increase in tension from the very beginning +soon brought it to a level which cannot be long maintained +and usually leads to a premature relaxation. In<span class="pagenum"><a name="Page_94" id="Page_94"></a>[Pg 94]</span> +the case of very large numbers the alternation of the slight +and the sudden increase may be repeated several times, +and at times it may even sink below a level which has already +been attained, thus making a wave-like curve.</p> + +<p>III. The third type of curve shows a sudden jump between +two units at a certain point in its course. This +may occur in the case of both small and large numbers +but only when the highest or first degree of concentration +is employed (see <a href="#Page_91">page 91</a>). Such a jump frequently +occurs in the transition from the tap preceding the last to +the last one which is being eagerly expected. Relaxation—with +the upward jerk and raising of the head—here +occurs at the normal time; Hans taps to the end with +his right foot. Oftener still the "jump" described occurs +while passing over to the number just before the +last. The goal seems within reach and the mental tension +relaxes, and with it the physical tension,—the head gives +a slight jerk and Hans makes the back-step. Since, however, +another tap is still awaited with some degree of +tenseness and, since complete erection of the head does +not follow immediately upon the jerk of the head, the +horse gives another tap with the left foot. Thereupon +occurs the complete relaxation of attention, and the assumption +of the erect posture on the part of the questioner. +That this is psychologically the clue which leads +to the final tap, will readily appear from the following +remarkable fact: I was able to bring about at will either +the back-step with the right foot, or the additional extra +tap with the left foot by concentrating the mind either +upon the last unit or upon the one just preceding it. In +either case the movement which served as stimulus to the +horse followed naturally upon concentration on the number. +I could of course also control the response by direct<span class="pagenum"><a name="Page_95" id="Page_95"></a>[Pg 95]</span> +voluntary control of the movements involved. Hans +thus solved for me the same ten problems first with the +back-step, then with the extra final tap.</p> + +<p>Finally we will indicate the one true inner cause of the +difficulty in getting the number 1 as a response. It is not +easy to relax attention immediately after having just +begun to concentrate. Relaxation, therefore, often occurs +with a certain retardation, and the result is a belated +jerk of the head.</p> + +<p>Briefly, I would also mention a few of the more interesting +introspective observations which were made in +situations in which the horse responded with movements +of the head for answers such as "yes" and "no", "up" +and "down", etc. From the very beginning I put questions +to Hans which would have to be answered by a +shake of the head. It often happened that instead of indicating +"0", Hans would begin tapping some number. +But the wonder of it was that, in many cases, he responded +properly. I knew only that I inwardly pronounced +the word "null" (zero), and that I looked expectantly +at the horse's head. In the case of questions to +which I expected the answer "yes" or "no", I imagined +myself enunciating the answer, i. e., I used motor imagery. +The tests failed, the moment I employed only +visual or auditory imagery, whereas, motor imagery was +always effective in calling forth correct reactions.<a name="FNanchor_M_13" id="FNanchor_M_13"></a><a href="#Footnote_M_13" class="fnanchor">[M]</a> When<span class="pagenum"><a name="Page_96" id="Page_96"></a>[Pg 96]</span> +the proper response was "up" and "down" I would +think of those directions in space, and likewise with +"left" and "right" in which case also I would put myself +in the horse's place.</p> + +<p>While I was still ignorant of the nature of the necessary +movements, the tests were successful only when I +had put the question aloud or in a whisper, but never +when I failed to enunciate, i. e., when I merely had the +question in mind ("in idea"). But this also became +possible after a little practice, although I could not then +give an explanation for my success. Except in one instance, +we could discern no difference between problems +spoken and those merely conceived by Mr. von Osten +who had had the advantage of long practice. But the one +exception deserves mention. The old gentleman commissioned +Hans, presumably without uttering a word, to +step backward to the left. Hans thereupon responded by +giving his entire repertoire, as follows: He moved his +head to the right, then to the left. Then he leaped forward +and repeated the same movement of the head. Hereupon +he stepped backward and signified a "yes" by a +movement of the head. He then lowered his head and +made two leaps forward. After this performance Mr. +von Osten repeated the same command aloud, and in every +case Hans responded properly. Again the silent command +was given and again the horse responded with the +series of reactions described above, lowering his head<span class="pagenum"><a name="Page_97" id="Page_97"></a>[Pg 97]</span> +leaping forward, etc. In this experiment, without exception, +the spoken command evoked adequate reactions,—the +silent command, an incorrect response. Evidently +the impulse to movement was not so great with the mere +conceiving of "right", "left", etc., as when the words +were enunciated. It, therefore, required some practice +on my part before a sufficiently strong movement-impulse +became associated with the idea. All this is in no wise +at variance with the fact that tests involving counting and +computation were as successful when the problem was +given in silence, as when it was spoken. The signs for +tapping, viz.: inclination and erection of the head and +body, followed the question. The question therefore became +superfluous. On the other hand the signs for head-movements +on the part of the horse, were given while the +question was being put. I ask, which way is "upward", +and at the same time I look upward. In this case therefore +the question itself is not entirely insignificant.—I experienced +greater difficulty in getting Hans to respond +with the head-movement to the left. After much practice +I was able to evoke this movement by means of +giving the command aloud, but never by means of the +"silent" command. Accidentally I hit upon a device by +means of which I attained this end also. I asked the horse +aloud "Which direction is left?",—whereupon he reacted +properly; then I immediately repeated the question +silently, and was successful every time. My mental attitude +here was still the same as when I put the question +aloud. What sort of an attitude this was, I could not, of +course, have stated explicitly at the time. I could not, +therefore, awaken it at will,—and if I allowed but a +minute to elapse between the spoken and the silent question, +the vivid after-effect (the so-called "primary mem<span class="pagenum"><a name="Page_98" id="Page_98"></a>[Pg 98]</span>ory +image") soon disappeared and the test was wholly +unsuccessful. Practice, however, soon helped me to overcome +this last difficulty also. I believe that my inability +to evoke this specific reaction on the part of the horse, +lay in the unfavorable position which I assumed, for it +did not allow the horse to <a name="tn_png_105"></a><!--TN: "preceive" changed to "perceive"-->perceive my movements easily. +For the same reason, Hans would at first indicate "no" +and "zero" by turning to the right, seldom to the left.</p> + +<p>As in the case of counting, a high degree of concentration +was also necessary here, but with this difference, +that here attention was directed to ideas present to the +mind, ("yes", "no", etc.), whereas in the counting +process attention was directed toward expected sensory +impressions (i. e., the taps of the horse).</p> + +<p>All that has been said thus far is readily understood +psychologically. The following curious fact, however, is +noteworthy. Hans used the head-movement to indicate +two such different concepts as "zero" and "no"; it appeared +therefore that in both cases he was receiving the +same kind of directive. Observation proved that such +was the case and the directive in question was none other +than an imitation in miniature, or rather a movement +anticipatory of the expected head-movement of the horse. +Now, whereas the signs for "up", "down", "right", +and "left" were natural expressive movements which are +normally associated with the corresponding concepts, this +cannot be said to be true of "no" and "zero". My +laboratory observations (see <a href="#Page_107">page 107</a>) lead me to conclude +that the movements, by means of which the concepts +"no" and "zero" are naturally expressed, are quite different; +and neither of these corresponds to the signs for +"zero" and "no" which the questioner involuntarily +gave to Hans. What was the genesis of these unnatural<span class="pagenum"><a name="Page_99" id="Page_99"></a>[Pg 99]</span> +forms of expression? If we might assume that the questioner +always had in mind the movement he awaited on +the part of the horse, and never thought of "zero" or +"no", then the contradiction would solve itself. But I +must deny decidedly that I ever thought of the movements +of the horse's head, and Mr. Schillings, whom I questioned +on this point, agreed with me in this, in so far as his +own mental processes were concerned. I can see nothing +for it but that in this instance the expressive movements +normally connected with the concepts "zero" and "no" +have been replaced by other forms, without the questioner +becoming aware of it. That such displacements may +occur, has been shown by the tests described on pages <a href="#Page_107">107</a> +to <a href="#Page_112">112</a>. That they did occur in this instance may be +concluded from the following observation. In responding +to me, as well as to Mr. Schillings, Hans always +moved his head first to the left, then to the right, never +in the opposite order. That this was <i>not</i> a peculiarity of +the horse, but must be ascribed to the signs which were +given him, is shown by the possibility of inverting the +order under experimental control (<a href="#Page_77">page 77</a>). Frequently +Mr. Schillings and I had seen the horse respond to his +master by means of such head-movements, and the order +was always, without exception, the one mentioned. It +must be assumed therefore that the horse's movement, +which we so often noticed, made such an impression upon +us, that afterwards it was regularly reproduced on our +part quite unconsciously, so that Mr. Schillings never, and +I only after a long time, became aware of the whole +process.</p> + +<p>In closing, just a word as to the discovery of our own +movements. I soon noticed that every pronounced raising +of the head or trunk brought about an interruption<span class="pagenum"><a name="Page_100" id="Page_100"></a>[Pg 100]</span> +in the horse's response. But only by observing the final +movement in the case of Mr. von Osten did I discover +that I, too, performed a slight erection of the head. Observation +of others was less difficult than the observation +of one's own movements. As in the case of all other signs +given to the horse, these movements were so slight that +they were prone to escape notice even though one's whole +attention were concentrated upon their detection. I also +questioned whether in my attempts to disturb the horse by +means of loud calls, it were really the call or some simultaneous +involuntary movement which was the true cause +of the interruption. The doubt was justified, for when +I finally learned to cry out vehemently without making +the slightest move, all my crying was in vain. Also it +had seemed to me at first as if I were able to induce the +horse to rear, not only by means of the proper sign or +movement, but also by a mere command, but I found +later that in every case there was always some movement, +were it ever so slight. Finally I tried to simulate voluntarily +the oft-mentioned involuntary jerks of the head. +Although it is not very difficult to execute them at will +with almost the same minuteness as when they were performed +involuntarily, I still did not succeed in getting a +series of such jerks of equal fineness throughout. In +spite of (and partly on account of) the most concentrated +attention, there would be from time to time a jerk of +somewhat greater extent and energy. As soon as the +movement had been executed, I was able to form a good +judgment as to its relative extent, but I was unable to +regulate the impulse beforehand.</p> + +<p>With the following comment the chapter will be concluded. +Introspections are necessarily subjective in character. +If they are to possess general validity, they must<span class="pagenum"><a name="Page_101" id="Page_101"></a>[Pg 101]</span> +be borne out by evidence furnished by others—and this +to a greater extent than is necessary for other forms of +observation. It was hardly possible to get corroboration +from the other persons who had worked with Hans, for, +although some of them were excellent observers of external +natural phenomena, few of them had had the necessary +amount of practice in introspection. The necessary +confirmation, however, was had in laboratory tests, +which we shall presently describe.</p> + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_M_13" id="Footnote_M_13"></a><a href="#FNanchor_M_13"><span class="label">[M]</span></a> Thus it is possible to think of the word "no" in three different +ways. I may get a visual image of the written or printed word, +or the auditory image of the word as spoken by another person, or +finally I might think of it in terms of images of the sensations of movement +which would arise if I myself were to enunciate or write the word. +And so, in like manner, I could think of any other word in terms of +either visual or auditory or motor imagery. In all probability the +auditory and motor always occur together,<a name="refanchor6"></a><a href="#ref_6" class="fnanchor">[6]</a> but still it is possible to make +the one or the other predominate. +</p><p> +It appears that the imagery of most persons is a mixture of auditory-motor +and visual elements, with a predominance of one or the other +kind. Individuals who utilize almost exclusively the visual (as does the +author, as a rule), are rare. But rarer still is the pronounced motor type.</p></div> +</div> + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_102" id="Page_102"></a>[Pg 102]</span> +<h2 style="padding-bottom:1em;"><a name="CHAPTER_IV" id="CHAPTER_IV"></a>CHAPTER IV</h2> + +<h2 style="padding-bottom:1em;">LABORATORY TESTS</h2> + + +<p><span class="firstwords">The</span> tests which are to be briefly reported here, were +begun in November, 1904, and were carried out at the +Psychological Institute of the University of Berlin. +The purpose was twofold: first, to discover whether the +expressive movements noted in Mr. von Osten, Mr. Schillings, +and others, were to be regarded as typical and to +be found in the majority of individuals,—and secondly, +to ascertain in how far the psychical processes which I +had noted in my own case and which I believed to lie at +bottom of these movements, were paralleled in, and confirmed +by, the introspections of others. The effort was +made to make the experimental conditions as nearly as +possible like those under which the horse had worked. +The affective atmosphere which colored the situations in +which the horse took part, could not, of course, be transferred, +but this was in some respects an advantage. One +person undertook the rôle of questioner, another—myself—that +of the horse. The experiments fall into three +groups, corresponding to the types of the horse's reactions: +1, tests in counting and computation; 2, tests in +space reactions; 3, tests in fetching or designating objects.</p> + +<p>In the experiments in counting and computation, the +questioner, standing at my right, thought with a high +degree of concentration of some number (usually between +1 and 10, but sometimes also as high as 100), or<span class="pagenum"><a name="Page_103" id="Page_103"></a>[Pg 103]</span> +of some simple problem in addition. Then I would +begin to tap,—but in human fashion with my right hand, +rather than with my foot—and continued until I believed +that I had perceived a final signal. I thus tested, +all in all, twenty-five persons, of every age and sex (including +children of five and six years), differing also in +nationality and occupation. None of them was aware +of the purpose of the experiments. It could not escape +them, to be sure, that they were being watched. It was +also evident to them that the things noted were certain +tensions and movements; but none of my subjects discovered +what the particular phenomena were that I was +looking for. Only in a few isolated instances did they +report that they were conscious of any movements on +their part. With the exception of two persons, they all +made the same involuntary movements which were described +in <a href="#CHAPTER_II">chapter II</a>, the most important of which was +the sudden slight upward jerk of the head when the final +number was reached. It was at once evident that the direction +of this jerk depended upon the position which one +had asked the subject to assume at the beginning of the +test, the direction changing whenever the position was +changed. Thus, if the subject stood with head bowed—the +body either being held erect or likewise bowed,—then +release of tension would be expressed physically by an +upward jerk. (Occasionally the entire trunk is slightly +raised, so that it was possible to observe this physical +reaction when standing behind the subject). If the subject +had bent his head backward, the "psychological moment" +was marked by a forward movement, (although +under certain conditions the head was, in such a case, +observed to bend still farther backward). If during the +tests the head was bent slightly to the right, then the re<span class="pagenum"><a name="Page_104" id="Page_104"></a>[Pg 104]</span>action +was expressed in a movement toward the left, and +<i>vice versa</i>, if it had been on the left, it was bent to the +right. If the subject had been bending his head forward +and to the right, he then raised it upward and to the left, +etc. In all of these changes of position I noticed an intermediate +posture which, to be sure, it was not always an +easy matter to discover,—viz.: an upright position in +which there was discernible no manner of head-movement +or only a slight tremor. If the subject was lying on his +back with his head supported, then there was noticeable a +very slight movement to one side. In this same way a +number of other positions were tested in order to discover +for each the characteristic movement expressive of +release of tension. It would therefore appear that the +raising of the questioner's head, which served as the +signal for stopping for Mr. von Osten's horse, was but +one instance of a general law which may perhaps be stated +thus: The release of muscular tension which occurs with +the cessation of psychic tension, tends to bring about that +position of the head (and body) which, at the time, represents +the slightest amount of muscular strain.—These +movements seldom were pronounced enough to be compared +to motion through a distance of one millimeter, in +a very few cases only did they attain to the magnitude of +one or two millimeters: I failed to note them entirely, +however, in only two individuals, two scientific men whose +mode of thought was always the most abstract, and one +of these was, in spite of repeated attempts, unable to elicit +any response whatever on the part of the horse.</p> + +<p>In the cases of the more suitable subjects I was able +to indicate not only the number they had in mind, but +also the divisions in which the number was thought, thus +12 as 5 and 5 and 2, or the same number as 2 and 5 and 5,<span class="pagenum"><a name="Page_105" id="Page_105"></a>[Pg 105]</span> +and I was also able to determine the addends in the +addition—i. e., whether the problem had been conceived +as 3+2=5 or as 2+3=5. It frequently happened that +in the beginning I would sometimes mistake these subdivisions, +which were recognizable by the less pronounced +jerks, for the final number. Thus I would often respond +with 4 instead of 8, or 3 instead of 9, or with 3 when the +problem was 3+2, just as Hans had so often done. In +these tests, too, the difficulty of getting the number 1, as +well as the larger numbers, came to light. Thus three +times in succession 17 was indicated as 4, as 9, and as 17. +But after some practice I was able to give numbers as +high as 58 and 96. The frequency of the errors of one +unit too many and of one unit too few is also noticeable +in these tests.</p> + +<p>We also found desirable corroboration, by trustworthy +subjects, of the introspective observations of the author, +which were reported in <a href="#CHAPTER_III">Chapter III</a>, with regard to the +significance of concentration and the curve of attention. +It is hardly necessary to mention that no attempts were +made to influence the subjects in their accounts by asking +suggestive questions. The most valuable feature about +these tests was that the mute horse had now been replaced, +as it were, by an animal capable of speech, and +that it was now possible to follow the same process both +from within and from without. Two illustrations may be +welcome. The one who took the part of the horse gave +three taps and made the following entry: "At 3 I saw a +slight upward jerk of the head on the part of the questioner". +The questioner however had thought of 4, and +made the following note, without knowledge of the other's +entry: "I was aware of extreme tension, so that it +was impossible for me to get beyond 3". Or again, the<span class="pagenum"><a name="Page_106" id="Page_106"></a>[Pg 106]</span> +'horse', reacting to a movement on the part of the questioner, +stopped at 3, but the latter, having intended to obtain +2, made the following entry: "I noted clearly that I +ceased thinking of the number too late, and did not put +on the brakes, as it were, until I had arrived at 3". We +see that errors here were entirely the fault of the questioner, +just as had been the case in the tests with Hans. +(See <a href="#Page_151">page 151f.</a>).</p> + +<p>In a second group of experiments I asked a subject to +fix his mind upon certain concepts, such as "up", or +"down", "right" or "left", "yes" or "no", and +others, in any order he pleased, but with the greatest +possible degree of concentration. The subject each time +had the choice of four or six concepts, and he was told +to think of one of them at the signal "Now!". How he +was to 'think' the concept was left entirely to him. +He was also told to interpolate the series with a 'blank', +that is, to think of nothing at all. Standing opposite the +subject, I tried to guess at the mental content of the person's +mind, on the basis of expressive movements. Sometimes +I reacted by shaking or nodding the head, etc., just +as Hans had done, but as a rule I was content to say +the word which I thought the subject had in mind. With +twelve subjects (a total of 350 tests) I made an average +of 73% correct responses, and in the more favorable cases +I attained even 90 to 100% correct responses. Very +slight involuntary movements of the head and eyes, +which showed but little individual variation, and always +occurred when the subject began to fix upon the concept, +were the signs which I used as cues. As in the case of +the movements expressive of the release of tension, which +I discussed above, these movements, too, occurred without +the subject being aware of them, (except in those<span class="pagenum"><a name="Page_107" id="Page_107"></a>[Pg 107]</span> +rare cases in which they had once or twice been especially +pronounced). Indeed, it was very difficult and in some +cases almost impossible for those persons whom I had +initiated into the secret, to inhibit them voluntarily. +"Up" and "down", "right" and "left", were expressed +by movements of head or eye in those directions, +"forward" by a forward movement of the head, "back" +by a corresponding movement. "Yes" was accompanied +by a slight nod of the head; "no" by two to four rapid +turnings of the head to either side.<a name="FNanchor_N_14" id="FNanchor_N_14"></a><a href="#Footnote_N_14" class="fnanchor">[N]</a> "Zero" was expressed +by a movement of the head describing an oval in +the air. Indeed, it was even possible to discover whether +the subject had conceived of a printed or a written +zero, for the characteristics of both were revealed in +the head-movements. I was able later to verify this +graphically. With Ch. as subject, I made 70% correct<span class="pagenum"><a name="Page_108" id="Page_108"></a>[Pg 108]</span> +interpretations in a total of 20 tests; with von A. as subject, +72% in a total of 25 tests. And finally I was able +to interpret the signs without any errors at all. It was +not absolutely necessary to look directly at the subject's +face. Even though I focussed a point quite to one side, +so that the image of the subject's face would fall upon a +peripheral portion of my retina, I still was able to make +89% correct interpretations in a total of 20 tests.—This is +not astonishing after all, when we recall that the periphery +of the retina possesses a relatively high sensitivity for +movement impressions, although its chromatic sensitivity +is very low.<a name="FNanchor_O_15" id="FNanchor_O_15"></a><a href="#Footnote_O_15" class="fnanchor">[O]</a></p> + +<p>It was assumed, as indicated on <a href="#Page_99">page 99</a>, that in the case of Mr. +Schillings and myself the movements naturally expressive of "zero" and +"no" had been displaced<span class="pagenum"><a name="Page_109" id="Page_109"></a>[Pg 109]</span>—without our being aware of the fact—by +others, viz.: those which the horse required as directives for his +reactions. Since this was the case, we tried to discover if a similar +displacement could be brought about experimentally. The attempt was +successful and we discovered that under suitable conditions we could +cause the subject—quite without knowledge on his part,—to establish an +"association" between any given concept and any given expressive +movement. The following experimental series will serve to illustrate +this fact.</p> + +<span class="pagenum"><a name="Page_110" id="Page_110"></a>[Pg 110]</span><p>I had one of the subjects (von A.) think of "left" and "right" in any +order he chose. (The command was purposely given only in a general way: +"Think of 'right' or 'left'".). We had agreed that I was to try to guess +the mental content of the subject's mind, but I was not to utter a word. +Instead, I was to indicate "right" in every case by an arm movement +downward, and "left" by a movement upward. To the subject I gave a +fictitious but plausible reason for all this. The behavior of the +subject took the following course: In the first three tests he moved his +eyes to the right when he thought of "right", and to the left when he +thought of "left". This was the normal expressive movement. In the +fourth test, however, the thought "left" was accompanied by an upward +movement of the eyes. Two further tests again showed eye-movements to +the right and left. In the seventh test with the idea "left" the eyes +moved first to the left and then immediately upward. In the following +ten tests the eyes were turned regularly upward at the thought of +"left", and downward at the thought of "right", with only one exception +which was a normal movement to the left. The normal expressive +movements, therefore, were displaced by the artificial, after the +seventh test.</p> + +<p>In the case of another subject (B.) in whom normally +the thought of "up" was accompanied by a slight raising +of the head, and "down" by a downward movement, +these natural forms of expression disappeared entirely as +a result of my arm movements to the right to indicate +that I inferred his having in mind the thought of "up", +and to the left when I inferred that he was thinking of +"down". Instead, there appeared not merely the desired +movements to the right and left, but rather movements +upward to the right and downward to the left. +That is, instead of a complete displacement of the old by +the new, there occurred a combination of the two.</p> + +<p>A third type of result appeared in still another subject +(Ch.), who normally expressed the concepts "right" +and "left" by eye or head movements (never both kinds +at the same time) to the right and left. Here my arm +movements up and down caused the eye and head movements +to be made simultaneously, so that the thought of +"right" found expression in an upward movement of +the head and an eye movement to the right, and the idea +of "left" in a downward head movement and a movement +of the eye to the left. The subject had no knowledge +of this process, and it took six tests to bring about +the new reaction. From that point onward the new movements +were so well established that, depending upon +them for my cue, I was able to make 32 correct inferences +in a total of 40 tests. During the latter part of this +series I blindfolded the subject, so that I could not see +the movements of his eyes, and therefore had to base my +inference entirely upon his head movements.—After removing +the bandage, at the end of the series, I told the +subject that I would go through another series, in which +I intended to indicate his thought of "right" by an arm<span class="pagenum"><a name="Page_111" id="Page_111"></a>[Pg 111]</span> +movement downward (instead of upward as heretofore), +and his thought of "left" by a movement upward. +(This he regarded as an idle whim of mine). It was +only after the twelfth test that the former "association" +which I myself had caused to be established, was completely +displaced by the new. The thought of "right" +was now accompanied by an eye movement to the right +and instead of a raising there was a lowering of the head. +A corresponding change occurred in the head movement +expressive of the thought of "left". These responses +were occasionally varied by some in which only the head +movement or only the eye movement occurred. But +these movements were always to the right, or downward +and to the right, at the thought of "right",—and to the +left, or upward and to the left, at the thought of "left". +In ten tests I made ten correct inferences. After the new +association appeared firmly established, I ceased responding +by means of arm movements, and indicated my +'guesses' by word of mouth. At first the newly acquired +movements continued to appear promptly in the subjects. +But gradually they tended to become more uncertain and +finally disappeared, as readily as they had appeared, and +the normal conditions were once more established. Nor +was there any tendency to reappear on the following day +in another series of tests. (Those just described had +been made on one day in the course of an hour or two). +But as soon as I again used the earlier method of arm +movement to indicate my inferences (raising the arm for +"right", lowering it for "left"), the former artificial +association was again established, although not until +some 14 tests had been made,—during which the normal +movements to the right and left were often inhibited and +during which the conditions were, on the whole, chaotic.<span class="pagenum"><a name="Page_112" id="Page_112"></a>[Pg 112]</span> +The new association, thus re-established, remained constant +during the ten tests of the remainder of the series, +but has very probably again disappeared long ere this. +In the case of this subject it appears therefore that the +new associations were superimposed upon, but in no +sense displaced, the normal expressive movements. Nor +did the two coalesce (except in a few exceptional cases), +but tended as a rule to occur independently of one another.</p> + +<p>I would emphasize once more that none of the subjects +had any knowledge of the purpose or meaning of the experiments. +Also, I was convinced by questioning the +subjects afterwards that none of them—and this is the essential +point—had merely conceived of the arm movement +which they were expecting me to make, instead of concentrating +thought upon the idea of "right" or "left". +On the contrary, all of them considered my particular +movements mere vagaries and without purpose, and they +felt perfectly certain that they were in no wise influenced +by these movements. Also, none of the subjects was conscious +of any movements on their part, except one, who +was at times aware of her eye movements to the right, +but never of those to the left, (see <a href="#Page_111">page 111</a>), nor of the +head movements which for us constituted the phenomena +of prime interest. When I asked my subjects what they +believed to be the cue upon which I based my inferences, +they invariably responded with probable explanations +which were always wide of the mark, and those to whom +I disclosed the cue—(after the experiments were completed), +were thoroughly astonished.</p> + +<p>In the tests just described we had to do only with such +ideas or concepts as normally were associated with some +stereotyped form of expressive movement (see <a href="#Page_106">page 106</a>).<span class="pagenum"><a name="Page_113" id="Page_113"></a>[Pg 113]</span> +I now chose a group of ideas which are not normally associated +with a particular form of motor expression peculiarly +characteristic of them, and sought to establish artificially +such a connection with some arbitrary movement, +without consciousness of the process on the part of the +subject. Thus I asked one subject (Miss St.), who had +no intimation of the aim of the tests, to think of the following +words in any order she might choose: "Ibis" +(ibis), "Irbis" (panther), "Kiebitz" (plover) and +"Kürbis" (pumpkin). I said that I would react to her +thoughts by means of arm movements forward and backward +to the right and to the left, respectively. 15 out of +20 tests were successful, without the slightest suspicion +on the part of the subject (whose whole attention was +concentrated on the word-content), that she was giving +me the necessary directives in the form of very minute +movements of the head and eyes to the right and left, etc. +She was greatly astonished that I should be able to guess +words so much alike,—(she did not know that the element +of likeness was productive of no difficulty). When, +during one of the tests, the subject happened to think +spontaneously of the movement she was expecting me to +make, she became confused, and as a result the number +of my sucessful reactions suddenly fell. I never would +have discovered the cause, had not the subject enlightened +me without my asking.</p> + +<p>I repeated this series with three other persons, who +had had some psychological training. I did not use the +same movement for each word in all three cases, but indicated +the word "Kiebitz", for instance, by means of an +upward movement in one case, by turning the head to the +right in another, etc. In one of the three cases the tests +were almost wholly unsuccessful. The cause for this<span class="pagenum"><a name="Page_114" id="Page_114"></a>[Pg 114]</span> +came to light later, but it would involve too much exposition +to discuss it at this point. In the case of the +other two persons, the tests were successful beyond expectation. +I had made my various arm movements only +a few times when they presently began to raise their +heads slightly when thinking of "Irbis", and to move it +to the right at the thought of "Kürbis", etc. In the two +series of 35 tests I did not have a single error. In a number +of instances I succeeded in guessing the word upon +which the subject had decided, even before the test +proper was entered upon—i. e., before the signal for concentration +had been given. Nothing surprised a subject +more than the remark: "You are intending to think of +the word 'Kürbis'", or "You had thought of concentrating +your mind upon 'Ibis' but later decided in favor +of 'Kiebitz'", yet nothing could be more simple. Before +every test the subject would consider what word he +would fix upon, and while he was saying to himself "I +will choose 'Ibis'", the proper movement would accompany +his decision, although it was only very slight, because +attention had not yet attained the degree of concentration +which was employed in the test proper.</p> + +<p>In these experiments also, the subjects, whom I know +to be absolutely trustworthy, declared that they never +thought of the arm movements which I was to make. +They regarded them as being quite irrelevant. Also—with +but one exception—they thought of the objects, in +so far as they imaged them visually, as being directly +before them, and not off in the direction indicated by my +arm movements. Thus they did not image the plover +("Kiebitz") as being on the wing, when I raised my +arm, or as resting on the ground, when I pointed downward, +etc. One of the subjects had done this occa<span class="pagenum"><a name="Page_115" id="Page_115"></a>[Pg 115]</span>sionally, +but by no means regularly. He was therefore +asked to localize all objects in the same place, i. e., directly +in front of him at the level of the eye. He complied with +this request, but no change, whatever, was observed to +occur in his expressive movements.</p> + +<p>In order to overcome the difficulty just mentioned, I +selected another subject (Miss von L.), whose power +of visualizing was very slight, and requested her to fix +her mind upon four words which I had selected because +they were not, necessarily, associated with a particular +image. The order in which the words were to be thought +of, was entirely optional on her part. The words were +"Form", <a name="tn_png_122"></a><!--TN: Double quote added before "Inhalt"-->"Inhalt", "Mass", and "Zahl", (form, content, +measure, and number), and each of them I accompanied, +with a certain definite arm movement. The +subject always pronounced the word inwardly as emphatically +as possible, but without ever imaging the corresponding +arm movement. Often, it must be noted, +she did not know whether or not the movement which +I made was the proper one. And yet she, too, soon fell +into line in the matter of executing unconsciously the +characteristic head movements. In a total of 50 tests, I +was able to make 10 correct guesses in the course of the +first 20 tests, 8 in the next 10 tests, and 19 in the last 20 +tests. Miss von L. noted only a few of her upward head-movements, +viz.: those that were especially pronounced +(movements through about 2 millimeters), but of the +others she knew nothing. The same experiment was repeated +with a psychologist, well-trained in introspection, +as a subject. Success was even greater here. But no +matter how closely the subject observed himself, he was +unable to solve the puzzle.</p> + +<p>Variations which were introduced in these tests, I<span class="pagenum"><a name="Page_116" id="Page_116"></a>[Pg 116]</span> +will only mention in passing. Thus, instead of making +an arm movement, I, in some cases, would tap with my +foot, for "Ibis" once, for "Kiebitz" twice. The subject +could not see my feet. The involuntary movement-expression +which became associated with "Ibis" was one +nod of the head, with "Kiebitz" two nods, etc. Here +our only <a name="tn_png_123"></a><!--TN: "concrn" changed to "concern"-->concern was to show that unconscious change +in natural expressive movements and the acquisition of +artificial ones are possible in the case of psychically +normal subjects trained in introspection.</p> + +<p>I was not satisfied with convincing myself subjectively +of the facts indicated, but sought to fix them objectively, +by means of a graphic method. For this purpose I used +the device mentioned by Prof. R. Sommer for the analysis +of expressive movements.<a name="refanchor18"></a><a href="#ref_18" class="fnanchor">[18]</a> The purpose for which +Prof. Sommer's apparatus had been constructed, was to +record the involuntary tremor and movement of the +hand. These movements, of course, take place in the +three dimensions of space. By means of three levers it +is possible to record the movements upon the flat surface +of a smoked paper fastened to the revolving drum of the +kymograph, the movements in each direction being recorded +by a separate lever, in such a way that the three +curves thus made represent the analysis of a single movement +into its three dimensional components. By making +slight changes, which tended to complicate the experiment +somewhat, I adapted the apparatus to the measurement +of movements of the head. The method of experimentation +was the following. The subject whose movements +were to be registered, was placed in the device +in such a way that his trunk and head were bent slightly +forward, the latter a little more than the former. This, +it will be remembered, was the usual position of the<span class="pagenum"><a name="Page_117" id="Page_117"></a>[Pg 117]</span> +questioner when working with the horse. Three levers +were attached to his head in such a way that every movement +backward or forward would act upon the first +lever, every movement to the right or left would move +the second, and every movement of the head upward or +downward would be recorded by the third. With regard +to the sensitivity of the machine, micrometric determination +showed that when the subject was properly installed, +movements through so small a distance as 1/10 millimeter +could be accurately ascertained. The subject was carefully +instructed to remain as quiet as possible, but without +constraint. Voluntary movements were thus obviated. +But the question arose: were not the involuntary +movements thus suffering a loss?—And it was upon them +that we were experimenting. The question cannot be +put aside summarily, but experience taught us that the +movements in question, nevertheless, did appear quite +effectually, if one could have the right kind of subjects +at one's command. We need hardly mention that besides +the two persons immediately concerned—I, myself, attended +to the apparatus—there was no one else present, +and that the subject was not allowed to see the curves +produced on the kymograph. Besides the registration +of the head-movements, I also undertook to register the +respiratory-movements of the subject. This was done +by means of the so-called pneumograph, attached to +which was a lever recording the thoracic expansion and +contraction. This was for the purpose of ascertaining +the relationship, which might eventually be found to +exist, between the release of psychic tension, on the one +hand, and respiration, on the other.</p> + +<p>The subject was now told to think of some number, +which, of course, was unknown to me. At a given<span class="pagenum"><a name="Page_118" id="Page_118"></a>[Pg 118]</span> +moment I was to tap upon one of a series of keys arranged +like those of a piano, with the middle finger of +my right hand—corresponding to the right forefoot of +the horse. The questioner observed my key, I, his head,—just +what had happened in the experiments with Hans,—and +as soon as I perceived the involuntary closing signal +I reacted upon it by releasing, suddenly, another key +upon the same keyboard, which I had in the meantime +been pressing down with my second finger, thus marking +what with Hans had been called the backstep. Each key +was connected with a separate electro-magnet, and these +in turn with markers, in such a manner that pressure +upon the keys closed two electric circuits and, releasing +the keys, opened them, and both the closing and the +opening were recorded upon the smoked paper by means +of the markers. And, finally, in order to ascertain the +time relations of all these processes, a time-marker indicated +the time in fifth-seconds upon the revolving +kymograph record. The time-curve was recorded just +below the other curves.</p> + +<p>Of the curves<a name="FNanchor_P_16" id="FNanchor_P_16"></a><a href="#Footnote_P_16" class="fnanchor">[P]</a> thus obtained under the most equable<span class="pagenum"><a name="Page_119" id="Page_119"></a>[Pg 119]</span> +conditions possible, we publish seven which show the +great general uniformity of the tests made upon the horse +with those made in the laboratory. The rôle of questioner +was undertaken at different times by Mr. Schillings and +the students of philosophy, Messrs. von Allesch, Chaym +and K. Zoege von Manteuffel. To all of them I am +greatly indebted for their unselfish services in these laborious +tests. The experiments with von Allesch and Chaym, +who were among the most suitable of my subjects, were +conducted absolutely without knowledge on their part of +the nature of the phenomena which I was observing. +Neither of them knew anything about the expressive +movements in which they were unconsciously indulging, +and furthermore, since they kept their heads bowed during +the entire course of these experiments, they did not perceive +what it was that I was observing. It is interesting +to note that Chaym on the occasion of his only visit to +the horse, immediately received a number of correct +responses. Without a doubt von Allesch would have +met with equal success. The other two subjects (von M. +and Sch.) went through this series of tests, possessing +some knowledge of the nature of the movements involved. +Conditions were such that they (and especially Mr. +Schillings) could not be prevented from obtaining some<span class="pagenum"><a name="Page_120" id="Page_120"></a>[Pg 120]</span> +knowledge of the essentials, at least. However, it would +be wrong to suppose that for this reason the results were +more favorable, owing, mayhap, to voluntary efforts on +the part of the subject. The contrary was true. The two +subjects who had no knowledge of the character of the +reactions upon which my responses depended, retained +their normal habits, unchanged, throughout the series,—whereas +the last-named two, afraid lest their knowledge +vitiate the result, lost more and more of their power of +concentration and within a short time were in a condition +of tense inhibition, which is all the more conceivable, +since they had had no psychological training whatever.<a name="FNanchor_Q_17" id="FNanchor_Q_17"></a><a href="#Footnote_Q_17" class="fnanchor">[Q]</a></p> + +<p>Their movements, which at first were quite profuse, +decreased more and more, so that in the case of von +Manteuffel the percentage of my successful responses +sank from 73% correct responses in 90 tests to 20% in a +total of 20 tests,—and in the case of Schillings from +75-100% to 23% in a series of 35 tests. The curves +obtained with von Manteuffel as subject, which I am +here publishing (figures <a href="#fig8">8</a> and <a href="#fig15">15</a>), are, however, true +to his normal habits. The same is true of the two first +curves of Schillings (figures <a href="#fig10">10</a> and <a href="#fig11">11</a>), whereas the +third (<a href="#fig12">figure 12</a>) shows distinctly the traces of the state +of inhibition into which he fell, and represents the same +condition as when Mr. Schillings, while preoccupied, tried +to work with Hans. All the finer details of the phenomena +in question, were likewise unknown to these two +subjects.</p> + +<p>For purposes of a clearer understanding of the various<span class="pagenum"><a name="Page_121" id="Page_121"></a>[Pg 121]</span> +curves, <a href="#fig5">figure 5</a> is inserted to give the general scheme +of their arrangement.</p> + +<div class="figcenter"><img src="images/figure_5.png" border="0" alt="" title="" width="411" height="700"><a name="fig5"></a> +<p class="caption smcap">Fig. 5.</p></div> + +<p>All curves are to be read like script from left to right. +The first is the breathing curve of the questioner, the +second, third and fourth curves represent his head move<span class="pagenum"><a name="Page_122" id="Page_122"></a>[Pg 122]</span>ments,—all +translated through the workings of the levers +into up-and-down movements. The objective direction of +these head movements is indicated by the arrows. It will +be noted that (because the lever in question was one +with two arms, and therefore reverses all movements +made) each lowering of the head <a name="tn_png_129"></a><!--TN: "of" changed to "is"-->is indicated by a rise in +the fourth curve, and each raising <a name="tn_png_129a"></a><!--TN: "is" changed to "of"-->of the head is recorded +by a sinking in the same curve. The records of the head +movements forward and backward and to the left and +right (curves 2 and 3) are two and one-half times the +size of the actual movements; while the curve of the +movements up and down (curve 4)—which is of especial +interest to us—is five times its actual size. The fifth +and sixth curves, which record my own responses, +represent the taps of the horse,—the fifth indicating the +number of taps and the sixth the back-step, which was +Hans's reaction when he noted the head-jerk of the +questioner. The seventh, the lowest line, indicates the +time in fifth-seconds. Since the rate at which the drum +revolved was not uniform for all the tests, the fifth-second +marks do not appear the same distance apart in +all the records, but are farther apart the greater the +rapidity with which the drum revolved. For the experiment +itself this is quite immaterial. Figures <a href="#fig6">6</a> to <a href="#fig9">9</a> correspond +in detail with the diagram just described. +Figures <a href="#fig10">10</a> to <a href="#fig12">12</a> differ only in that the breathing and +back-step curves (the first and sixth in the diagram) are +lacking. In these there is no response on my part to +the head-jerk of the subject, but tapping was continued +<i>ad libitum</i> (in the case of the illustrations here given I +tapped to 5). When these latter curves were taken the +ordering and the technique of the experiments had not +yet been perfected. When this was finally done, Mr.<span class="pagenum"><a name="Page_123" id="Page_123"></a>[Pg 123]</span> +Schillings, who acted as subject in those tests, had to be +eliminated from the ranks of appropriate subjects on +account of the increasing inhibitions, which gradually +developed as described on <a href="#Page_120">page 120</a>.</p> + +<p>Analysis of such curves is rather difficult, and those +of different subjects cannot be directly compared. It is +necessary to make a study of the normal curve of each +subject taken when his affective state could be described +as "indifferent". The influences of the purely physiological +processes, such as pulse<a name="FNanchor_R_18" id="FNanchor_R_18"></a><a href="#Footnote_R_18" class="fnanchor">[R]</a> and respiration, must +also be determined. And even so, an interpretation of +the curve becomes possible only when a large mass of +material is at hand, and when the introspections of the +subject are taken into consideration. The following +remarks, therefore, are not based solely upon the illustrations +given, but upon the mass total of my results.</p> + +<p>In beginning our analysis, let us take first the breathing +curve. Our results here were quite in accord with the +view taken by Zoneff and Meumann,<a name="refanchor20"></a><a href="#ref_20" class="fnanchor">[20]</a> who believe that +in the respiration is to be found a good index of the +affective tone of the subject's mental state. In the +greater number of cases it was possible to conclude as to<span class="pagenum"><a name="Page_124" id="Page_124"></a>[Pg 124]</span> +the degree of concentration of attention,—and when this +was very great, it was even possible to get a clue as to +the number thought of. Since the high degree of tension, +under which a subject labored during a test, would +be accompanied by strong affective coloring, we cannot +regard as normal any of the curves here reproduced +(with the exception of the two high points in <a href="#fig9">figure 9</a>). +Although breathing was always deep and regular before +and after a test, during the test it was less deep and irregular. +Very often it was suspended altogether (figures +<a href="#fig7">7</a>, <a href="#fig8">8</a> and <a href="#fig9">9</a>). In ordinary life we often notice that highly +concentrated attention is usually accompanied by non-voluntary +inhibition of movements in the musculature +which, for the moment, is not directly involved; the man +lost in thought slackens his pace and finally stands still, +the intent listener or looker-on holds his breath.</p> + +<p>Of the three curves registering the movements of the +head, we find that nothing peculiarly characteristic is +revealed by the two upper ones, giving the movements +up and down, and to the right and left, respectively. +They are the ordinary tremor-like movements and indicate +nothing beyond the fact that the subject is unable +to hold his head absolutely quiet for even one second. +It is the third line that is of interest to us, for it is here +that the oft-mentioned head-jerk (which indicates arrival—in +the counting—at the number expected) registers +itself. The moment of the head-jerk corresponds, almost +without exception, with the moment of the first deep +inhalation,—just as one would be led to expect from +common experience. But we are not to regard the head-jerk +as a result of the inhalation, for it also occurs when +the subject complies with the request that he hold his +breath during the test. The actual height of the jerks<span class="pagenum"><a name="Page_125" id="Page_125"></a>[Pg 125]</span> +recorded in figures <a href="#fig6">6</a> to <a href="#fig12">12</a> was ¼ to 1½ millimeters and +the average height obtained from the forty curves of +these four subjects was 1 millimeter. There is great +individual variation: the greatest height that was obtained +from the records was 2-3/10 millimeters, the lowest +1/10 millimeter. The variations within the records of +the several individuals are comparatively slight and +are evidently dependent, in the main, upon the degree +of concentration of attention. Thus in the case of von +Allesch, where in 75 tests the average height of the jerk +is 1 millimeter, the mean variation is 4/10 millimeter. If, +in order to obtain some idea of the size of Mr. von Osten's +movements,<a name="FNanchor_S_19" id="FNanchor_S_19"></a><a href="#Footnote_S_19" class="fnanchor">[S]</a> we compared the values gained in the +laboratory with those which would probably obtain in +his case, we would say that his head movements were +more minute than almost any of those of which we +obtained records. At the most they could not have been +more than 1/5 millimeter (when measured in terms of +the distance through which the brim of his broad hat +moved, they would appear to be about 1½ times as large. +See <a href="#Page_49">page 49</a>.) The movements of Mr. Schillings, on +the other hand, were certainly four or five times as great +as those of Mr. von Osten, and occasionally even greater +than that. When we turn to consider the time-interval +elapsing between the subject's final head-jerk and my +reaction (as recorded in the sixth curve), we find that<span class="pagenum"><a name="Page_126" id="Page_126"></a>[Pg 126]</span> +the reaction-time averages 3/10 seconds, a value which +agrees very favorably with that estimated for the horse +(<a href="#Page_56">page 56</a>). Thus it appears that man and beast have +the same reaction-time—though we must bear in mind<span class="pagenum"><a name="Page_127" id="Page_127"></a>[Pg 127]</span> +that I worked under some difficulty, since I had to care +for the apparatus.</p> + +<p>Let us now turn to a discussion of the several figures.</p> + +<p><a href="#fig6">Figure 6</a> (von Allesch) gives a typical view of the +great, and at the same time economic concentration of +attention characteristic of the subject. Respiration (first +curve) is not so profound as usual, yet is changed very +little. The head-jerk (fourth curve) is of medium height. +It occurs just at the proper moment,—the subject had +thought of 2, and had directed his attention economically. +This attention was of the kind described as <a name="tn_png_134"></a><!--TN: Period removed after "I"-->type I +on <a href="#Page_93">page 93</a>. The lowering of the head, (recorded in the +figure by a rise in the curve), immediately following upon +the head-jerk upward, is irrelevant.</p> + +<p>In <a href="#fig7">figure 7</a> (Chaym) we have a record of a different +nature. Respiration was inhibited throughout the test,—(the +small waves are due to the pulsating of the heart); +immediately after the test deep breathing takes place. +Tension steadily increased till 3, the number expected, +was reached. The head, accordingly, gradually sank a +little forward. The head-jerk ensued during an interval +beginning just before the reaching of the goal and ended +immediately after. The movement was predominantly +backward, its upward direction being only through a +distance of ¼ millimeter. (This subject was not so +strongly motor as the preceding one.) The reaction +followed promptly as seen in curve 6. It was the decided +raising of the head which follows the head-jerk, that +prevented the usual back-step with the left foot, when +the subject was working with Hans.</p> + +<table border="0" width="600" cellpadding="3" cellspacing="2" summary="Figures 6 and 7" align="center"> +<tr valign="bottom"> +<td width="50%"><div class="figcenter"><img src="images/figure_6.png" border="0" alt="" title="" width="164" height="661"><a name="fig6"></a> +<p class="caption smcap">Fig. 6.</p></div> +</td> +<td width="50%"><div class="figcenter"><img src="images/figure_7.png" border="0" alt="" title="" width="313" height="700"><a name="fig7"></a> +<p class="caption smcap">Fig. 7.</p></div> +</td> +</tr> +</table> + +<p><a href="#fig8">Figure 8</a> (von Manteuffel) is typical of strong and +at the same time economical concentration. Respiration, +normally deep and very regular, is for a time completely<span class="pagenum"><a name="Page_128" id="Page_128"></a>[Pg 128]</span> +inhibited. Tension rises steadily and the head gradually +inclines forward. In the interval between the number +before the final one and the final one the subject makes a +sudden bend forward and immediately upon reaching the<span class="pagenum"><a name="Page_129" id="Page_129"></a>[Pg 129]</span> +final number gives a violent jerk of the head, upward. +The attention here would be characterized as being of type +III, described on <a href="#Page_94">page 94</a>. (Owing to lack of space it is +impossible to give an example of type II, which is only +to be found in the case of very large numbers.)</p> + +<p><a href="#fig9">Figure 9</a> (von Allesch) is expressive of great, but—according +to the subject's introspection—not economical +concentration. Respiration, which before and after the +test was quite regular, during the test itself shows a +pause. (The tiny waves are due to the heart-beat.) The +subject had thought of 5, and this number is accompanied +by a decided head-jerk. But we note that even before +the final jerk a number of less pronounced jerks occur—the +result of poorly regulated psychic tension.</p> + + +<table border="0" width="600" cellpadding="3" cellspacing="2" summary="Figures 8 and 9" align="center"> +<tr valign="bottom"> +<td width="50%"><div class="figcenter"><img src="images/figure_8.png" border="0" alt="" title="" width="144" height="690"><a name="fig8"></a> +<p class="caption smcap">Fig. 8.</p></div> +</td> +<td width="50%"><div class="figcenter"><img src="images/figure_9.png" border="0" alt="" title="" width="254" height="700"><a name="fig9"></a> +<p class="caption smcap">Fig. 9.</p></div> +</td> +</tr> +</table> + + +<p><a href="#fig10">Figure 10</a> (Schillings) depicts a very high degree of +uneconomical concentration. There was sudden concentration +at the beginning of the test, and a steady increase +throughout its course. Accordingly Mr. Schillings bent<span class="pagenum"><a name="Page_130" id="Page_130"></a>[Pg 130]</span> +forward at the start, and inclined still farther forward +at the second—and just before the third—tap. But +at 3 there is a sudden upward jerk. The number +thought of had been 4, tension therefore had exploded, as +it were, too soon.</p> + +<div class="figcenter"><img src="images/figure_10.png" border="0" alt="" title="" width="389" height="400"><a name="fig10"></a> +<p class="caption smcap">Fig. 10.</p></div> + +<p><a href="#fig11">Figure 11</a> (again of Schillings) gives indications, on +the other hand, of a medium and economic concentration +of attention, which is more normal in character. The +number thought of was 4.</p> + +<div class="figcenter"><img src="images/figure_11.png" border="0" alt="" title="" width="490" height="400"><a name="fig11"></a> +<p class="caption smcap">Fig. 11.</p></div> + + +<p><a href="#fig12">Figure 12</a> (Schillings again) is indicative of a low +degree of psychic tension. With the very first tap the +head begins to rise and continues to do so throughout +the test. A true final jerk does not occur, we note rather +in all three curves registering the head movements, slight +time-marking movements, especially in the second curve. +In the third curve they are at first minute, but increase +steadily in size until the fourth tap, after which they +suddenly disappear. The subject had, as a matter of fact,<span class="pagenum"><a name="Page_131" id="Page_131"></a>[Pg 131]</span> +thought of the number 4, but it is hardly probable that +Hans would have reacted properly upon these stimuli.</p> + +<div class="figcenter"><img src="images/figure_12.png" border="0" alt="" title="" width="388" height="400"><a name="fig12"></a> +<p class="caption smcap">Fig. 12.</p></div> + +<p>Mr. Schillings had thought of the same number in all +three tests given in figures <a href="#fig10">10</a>, <a href="#fig11">11</a> and <a href="#fig12">12</a>. The probabilities +are that if he had been working with the horse +at the time, in the first case Hans would have reacted +with three taps with the right foot and a final tap with the +left, as a result of the questioner's bending forward again +after the premature head-jerk at 3. In the second instance +the horse would probably have given four taps +with the right foot, and in the third, the chances are that +he would have continued to tap beyond the 4.</p> + +<p>These curves give, on the whole, a fair idea of the intensity +and of the course of attention of the various +subjects.</p> + +<p>Let us now consider a number of records which illustrate +the expressive movements involved in the process +of thinking of such concepts as "up", "down", etc.<span class="pagenum"><a name="Page_132" id="Page_132"></a>[Pg 132]</span> +Their arrangement is identical with the scheme given in +<a href="#fig5">figure 5</a>, with the exception that the tapping curves (the +sixth and seventh) do not appear. The subject was asked +to think of any of the words "up", "down", "right", +"left", "yes", "no", etc. He was to begin to conceive +them vividly when the command "Now!" was given. +This moment is recorded in figures <a href="#fig13">13</a> to <a href="#fig15">15</a> on the fifth +curve. What has been said on <a href="#Page_123">page 123</a> with regard to +respiration, holds also in these instances: only the first +rise recorded in <a href="#fig14">figure 14</a> can be regarded as normal.<span class="pagenum"><a name="Page_133" id="Page_133"></a>[Pg 133]</span> +The magnitude of these movements varies between ½ +and 3 millimeters. The records of the subject whose +movements were most extensive, show an average of 1-7/10 +millimeter (based on 50 tests), with a mean variation of +6/10 millimeter. Lack of space precludes the reproduction +of more than three records.</p> + +<p><a href="#fig13">Figure 13</a> (von Allesch) shows the movement accompanying +the thought of "up", a slight raise of the head, +recorded in the fourth curve. (The thought of "down" +is accompanied by a corresponding downward movement.)</p> + +<div class="figcenter"><img src="images/figure_13.png" border="0" alt="" title="" width="226" height="700"><a name="fig13"></a> +<p class="caption smcap">Fig. 13.</p></div> + +<p>Figures <a href="#fig14">14</a> (von Allesch) and <a href="#fig15">15</a> (von Manteuffel) +illustrate the nod which is associated with the thought +of "yes" in the case of two subjects. It is essentially +the same in both: the head is lowered and then raised. +The first of the two subjects is more decidedly motor, +and his movements therefore were somewhat the more +extensive. In the case of the second subject the nod +proper is followed by another which is somewhat less +extensive.</p> + +<table border="0" width="600" cellpadding="3" cellspacing="2" summary="Figures 14 and 15" align="center"> +<tr valign="bottom"> +<td width="50%"><div class="figcenter"><img src="images/figure_14.png" border="0" alt="" title="" width="231" height="700"><a name="fig14"></a> +<p class="caption smcap">Fig. 14.</p></div> +</td> +<td width="50%"><div class="figcenter"><img src="images/figure_15.png" border="0" alt="" title="" width="173" height="471"><a name="fig15"></a> +<p class="caption smcap">Fig. 15.</p></div> +</td> +</tr> +</table> + + +<p>A number of other experiments were carried out which +corresponded with the color-selecting tests made upon +Hans. (<a href="#Page_78">Page 78</a>.) Five sheets of white paper, ½ +meter long and ¼ meter wide, were arranged in a series +upon the floor, ¼ meter apart. A dot marked the middle +of each. The experimenter stood at a distance of 7½ +meters and directly opposite the middle sheet. At about +½ meter to the right or left of him stood the subject who +took the part of the "horse". The problem of the experimenter +was to indicate to the "horse" a certain one +of the five sheets, but without the use of word or gesture. +I at first undertook the rôle of "horse", whereas the +others consecutively played the part of questioner. All<span class="pagenum"><a name="Page_134" id="Page_134"></a>[Pg 134]</span> +of them looked fixedly at the sheet which they had in +mind. Besides, it usually happened that they would turn +at least their heads, and often their bodies, more or less +in the direction of the particular sheet—and this without +purpose or knowledge on their part, but purely as a +result of concentration upon the sheet they wished me +to point out. One of the experimenters remarked, quite<span class="pagenum"><a name="Page_135" id="Page_135"></a>[Pg 135]</span> +casually, that he had noted that I always made a better +judgment, the more intently he thought of the sheet. +Others often admitted that, when I had made an error, +they had not imagined the sheet vividly, or had been +debating whether or not to decide to think of the neighboring +sheet—the one I had designated. This indecision +could be noticed by the direction of the eyes. But the +following table shows how uniform, on the whole, was +the behavior of the various persons when under the +guidance of the same impulse. The number of tests was +200 in each case. All errors were of the same character. +Neighboring sheets were mistaken for each other, and +the errors were never of more than one position to either +side. Their number can easily be obtained by subtracting +the percentage of correct inferences from the total, +100%.</p> + + +<div style="font-size:.8em;"> +<table border="0" width="80%" cellpadding="1" cellspacing="0" summary="Test Result Table 11" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> + +<tr valign="top"> +<td align="left" width="34%">Experimenter:</td> +<td align="center" width="11%">v. A.</td> +<td align="center" width="11%">B.</td> +<td align="center" width="11%">C.</td> +<td align="center" width="11%">Mrs. v. H.</td> +<td align="center" width="11%">K.</td> +<td align="center" width="11%">Miss v. L.</td> +</tr> +<tr valign="top"> +<td align="left" width="34%">Correct inferences:</td> +<td align="center" width="11%">88%</td> +<td align="center" width="11%">88%</td> +<td align="center" width="11%">77%</td> +<td align="center" width="11%">81%</td> +<td align="center" width="11%">77%</td> +<td align="center" width="11%">82%</td> +</tr> +</table> +</div> + +<p>It will be seen that the number of correct interpretations +is quite high and in none of the cases does it deviate far +from the mean average of 82%.</p> + +<p>I based my judgment as to the direction of the subject's +eyes, upon an imaginary line perpendicular to the center +of the cornea. (This perpendicular does not always +coincide with the subject's line of vision, which was the +thing I was after, but this cannot be directly obtained. +This, of course, was what made the judgment a rather +difficult matter.) My judgment as to the direction of +the head I based largely on the direction of the nose, +(to express it more accurately: upon the direction of the +median plane.) I purposely noted only the position of +the experimenter and not the movement which led up <a name="tn_png_142"></a><!--TN: "to to" replaced by "to"-->to<span class="pagenum"><a name="Page_136" id="Page_136"></a>[Pg 136]</span> +it. When I tried to do the latter, the results were not +always satisfactory, because the head and eyes of the +person would frequently, in the process of adjustment, +move beyond the goal and thus lead me into error. An +attempt was made to make each judgment as independent +as possible of the preceding one. But usually, after a +few tests, an unintentional association became established +between certain attitudes and the different places in the +series of papers. Often all that was necessary was to +observe the experimenter in order to know which of the +places he had in mind, it was not necessary to look at +the papers at all. Every change in the position of the +person would, of course, make the association thus established, +useless.</p> + +<p>Later, the subjects and I changed rôles, I took the +part of the experimenter and they the part of the +"horse". The number of tests in each case was 200 +as before. Here, too, errors were, with but one exception, +never more than of one place to either side. +Whether the error was one place to the right or one place +to the left appeared to depend upon the position of the +person making the judgment, i. e., it depended on whether +he stood at my right or at my left. The following results +were obtained:</p> + + +<div style="font-size:.8em;"> +<table border="0" width="80%" cellpadding="1" cellspacing="0" summary="Test Result Table 12" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> + +<tr valign="top"> +<td align="left" width="34%">Subject ("horse"):</td> +<td align="center" width="11%">v. A.</td> +<td align="center" width="11%">B.</td> +<td align="center" width="11%">C.</td> +<td align="center" width="11%">Mrs. v. H.</td> +<td align="center" width="11%">K.</td> +<td align="center" width="11%">Miss v. L.</td> +</tr> +<tr valign="top"> +<td align="left" width="34%">Correct inferences:</td> +<td align="center" width="11%">76%</td> +<td align="center" width="11%">79%</td> +<td align="center" width="11%">75%</td> +<td align="center" width="11%">81%</td> +<td align="center" width="11%">77%</td> +<td align="center" width="11%">74%</td> +</tr> +</table> +</div> + +<p>A certain agreement can be seen in these results. The +average of correct inferences is somewhat lower than +that which was obtained by me (<a href="#Page_135">page 135</a>), 77% as over +against 82%. This is probably due to the fact that the +subjects had had so little practice compared with me.</p> + +<p>With one of these subjects, Mr. Koffka, a student of<span class="pagenum"><a name="Page_137" id="Page_137"></a>[Pg 137]</span> +philosophy, I carried these tests somewhat further, varying +them partly by increasing the number of sheets of +paper, partly by decreasing the distance between them. +The increase in the number of sheets made only a slight +difference in the results. With 200 tests in each case I +obtained the following results:</p> + + +<div style="font-size:.8em;"> +<table border="0" width="80%" cellpadding="1" cellspacing="0" summary="Test Result Table 13" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> + +<tr valign="top"> +<td align="left" width="31%">No. of sheets</td> +<td align="center" width="3%">:</td> +<td align="center" width="11%">5</td> +<td align="center" width="11%">6</td> +<td align="center" width="11%">7</td> +<td align="center" width="11%">8</td> +<td align="center" width="11%">9</td> +<td align="center" width="11%">10</td> +</tr> +<tr valign="top"> +<td align="left" width="31%">Correct inferences</td> +<td align="center" width="3%">:</td> +<td align="center" width="11%">77%</td> +<td align="center" width="11%">72%</td> +<td align="center" width="11%">72%</td> +<td align="center" width="11%">69%</td> +<td align="center" width="11%">73%</td> +<td align="center" width="11%">68%</td> +</tr> +</table> +</div> + + +<p>With but few exceptions, the errors were, as a rule, of +one place. The series with an odd number of sheets (5, +7, 9) gave better results than those with an even number +(6, 8, 10). In the tests with the odd number of sheets +the experimenter (K.) stood in front of the middle sheet, +so that it was at the apex of a right angle made by the +series of papers and the median plane of the subject's +body; whereas in the case of the even number of papers +the subject stood opposite the space between the two +middle sheets, thus making the position of the sheets less +favorable.</p> + +<p>In the preceding tests the distance between the centers +of the neighboring sheets was always 50 centimeters, so +that the angle through which the median plane of the experimenter's +body would have to turn in order to pass +from one sheet to the next, was about 3¾ degrees. In +the following tests these distances were gradually +decreased. The sheets, always five in number, were +replaced by ever narrower white strips of paper mounted +on dark cardboard and illumined by a Nernst lamp. +The following table shows the decrease in correct inferences +running parallel with the decrease of the angle +through which the subject would have to turn in order +to be in line with the several pieces of a series succes<span class="pagenum"><a name="Page_138" id="Page_138"></a>[Pg 138]</span>sively. +The percentage in each case is based upon at +least 100 tests.</p> + + +<div style="font-size:.8em;"> +<table border="0" width="80%" cellpadding="1" cellspacing="0" summary="Test Result Table 14" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> + +<tr valign="top"> +<td align="left" width="34%"><span style="display: block; padding-left: 1.8em; text-indent: -1.2em;">Angle:</span></td> +<td align="center" width="11%">3¾°</td> +<td align="center" width="11%">3°</td> +<td align="center" width="11%">2½°</td> +<td align="center" width="11%">2°</td> +<td align="center" width="11%">1½°</td> +<td align="center" width="11%">1°</td> +</tr> +<tr valign="top"> +<td align="left" width="34%"><span style="display: block; padding-left: 1.8em; text-indent: -1.2em;">Distance between the +centres of two neighboring papers:</span></td> +<td align="center" width="11%"><a name="tn_png_145"></a><!--TN: Period added after "50cm"-->50cm.</td> +<td align="center" width="11%">39cm.</td> +<td align="center" width="11%">33cm.</td> +<td align="center" width="11%">26cm.</td> +<td align="center" width="11%">20cm.</td> +<td align="center" width="11%">13cm.</td> +</tr> +<tr valign="top"> +<td align="left" width="34%"><span style="display: block; padding-left: 1.8em; text-indent: -1.2em;">No. of correct inferences:</span></td> +<td align="center" width="11%">77%</td> +<td align="center" width="11%">73%</td> +<td align="center" width="11%">71%</td> +<td align="center" width="11%">68%</td> +<td align="center" width="11%">66%</td> +<td align="center" width="11%">61%</td> +</tr> +</table> +</div> + + +<p>A curious and unexpected change was here noted in +the subject, Mr. Koffka, who, while concentrating his +attention to the uttermost, began unawares to develop +a new system of expressive movements of the head. +When the distance between the sheets was relatively +great, he had been in the habit of turning his head and +eyes in the direction of the sheet intended, and as the +distances became less he had reacted only by a turning +of the eyes. But now, as the distances were still further +decreased, he began again to react by means of head +movements, and these were of exaggerated magnitude, +for which he would compensate, as it were, by an eye-movement +in the opposite direction. Although the head +movements decreased in scope as the distances between +the sheets were steadily decreased, they still were always +decidedly greater than the eye movements, which I was +now normally led to expect and which could be judged +without much difficulty. This form of reaction was much +more satisfactory as a cue, and therefore it came to pass +that, whereas in the preceding series I had made only 60% +correct inferences when the angle was 1 degree, I now +found that—the angle remaining the same—80% of my +inferences were correct. (My final judgment I continued +to base, as before, upon the position, and not upon the<span class="pagenum"><a name="Page_139" id="Page_139"></a>[Pg 139]</span> +movement, of head and eye). The number of correct +inferences continued relatively high, even after the distance +between the papers was decreased tenfold,—as +will be seen from the following table:</p> + + +<div style="font-size:.8em;"> +<table border="0" width="80%" cellpadding="1" cellspacing="0" summary="Test Result Table 15" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> + +<tr valign="top"> +<td align="left" width="37%"><span style="display: block; padding-left: 1.8em; text-indent: -1.2em;">Angle:</span></td> +<td align="center" width="7%">1°</td> +<td align="center" width="7%">30'</td> +<td align="center" width="7%">15'</td> +<td align="center" width="7%">9'</td> +<td align="center" width="7%">7'</td> +<td align="center" width="7%">6'</td> +<td align="center" width="7%">5'</td> +<td align="center" width="7%">3'</td> +<td align="center" width="7%">2'</td> +</tr> +<tr valign="top"> +<td align="left" width="37%"><span style="display: block; padding-left: 1.8em; text-indent: -1.2em;">Distance between the +centres of two neighboring papers:</span></td> +<td align="center" width="7%">131</td> +<td align="center" width="7%">65</td> +<td align="center" width="7%">33</td> +<td align="center" width="7%">20</td> +<td align="center" width="7%">15</td> +<td align="center" width="7%">13</td> +<td align="center" width="7%">11</td> +<td align="center" width="7%">6½</td> +<td align="center" width="7%">4mm.</td> +</tr> +<tr valign="top"> +<td align="left" width="34%"><span style="display: block; padding-left: 1.8em; text-indent: -1.2em;">Percentage of correct inferences:</span></td> +<td align="center" width="7%">80</td> +<td align="center" width="7%">79</td> +<td align="center" width="7%">78</td> +<td align="center" width="7%">81</td> +<td align="center" width="7%">84</td> +<td align="center" width="7%">80</td> +<td align="center" width="7%">77</td> +<td align="center" width="7%">68</td> +<td align="center" width="7%">68%</td> +</tr> +</table> +</div> + +<p>Beginning with an angle of 1' (distance between the +centers of two neighboring papers = 2 mm.), the subject +was unable to focus, with sufficient steadiness of +vision, upon one paper alone, and the movements, for that +reason, ceased to manifest themselves. Comparing the +results obtained in the case of this subject with those +obtained from two others, whose reactions had remained +normal, B. and Miss St., we find that with them there +were only 53% correct inferences in both cases (based +each upon 200 tests), when the angle was 5'. In my +errors, too, I often shot wider of the mark. In another +series of 200 tests, in which Miss St. "merely thought +of the places", I had a percentage of 56% correct inferences, +and my errors did not become any coarser. Miss +St. believed this a case of true telepathy, but I had been +guided in my judgments entirely by her unwittingly +made movements—or rather the direction—of her eyes. +The magnitude of these movements bore a constant relationship +to the distance between papers as it was conceived +by the subject.</p> + +<p>Reviewing the experiments discussed in this chapter, +we find that the same kind of movements and postures,<span class="pagenum"><a name="Page_140" id="Page_140"></a>[Pg 140]</span> +which had been noted in persons experimenting with the +horse, tended to recur in the laboratory, in so far as the +mental attitude of the subjects, given in their introspective +accounts, corresponded with that of the questioners +of the horse.</p> + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_N_14" id="Footnote_N_14"></a><a href="#FNanchor_N_14"><span class="label">[N]</span></a> It was Charles Darwin<a name="refanchor7"></a><a href="#ref_7" class="fnanchor">[7]</a> who first pointed out that the expressive +movements (of the coarser sort) to be noted in nearly every race and +people show a great, though by no means complete, similarity. The +similarity is most pronounced in the shaking of the head to signify negation +and nodding to denote affirmation. It will be noted that the +former is essentially of the nature of a turning toward, and the latter +a turning away.<a name="refanchor8"></a><a href="#ref_8" class="fnanchor">[8]</a> These same movements have been reported in the +case of the blind and deaf Laura Bridgman,<a name="refanchor9"></a><a href="#ref_9" class="fnanchor">[9]</a> and we have been explicitly +assured that they were a spontaneous development, and not +acquired by imitation. For it is by imitation and never before the +completion of the first year, that our children acquire these movements. +On account of his unreliability, we can put but little stock in +the statement of Garner,<a name="refanchor10"></a><a href="#ref_10" class="fnanchor">[10]</a> a writer on the speech of monkeys, that +these same gestures have been observed in the case of those animals. +My experiments show that the same movements, greatly diminished in +scope, as a rule accompany the mere thought of "yes," "no," etc. I +cannot, however, regard the assertion as an established fact that every +thought process whatsoever is connected with some form of muscular +movement, as has been generalized by the French physiologist Féré,<a name="refanchor11"></a><a href="#ref_11" class="fnanchor">[11]</a> +and the American psychologist Wm. James.<a name="refanchor12"></a><a href="#ref_12" class="fnanchor">[12]</a></p></div> + +<div class="footnote"><p><a name="Footnote_O_15" id="Footnote_O_15"></a><a href="#FNanchor_O_15"><span class="label">[O]</span></a> The productions of mind-readers, so-called, also, are based upon the +perception of involuntary movements, insofar as they are not based +upon pre-arranged schemes and trickery. But there we have to do +principally with tactual perception, since the reader touches the hand of +the subject and is guided by its tremor. Some of the expert mind-readers, +however, conduct tests without touching the subject. They +depend chiefly upon auditory impressions: the sound of footsteps,<a name="refanchor13"></a><a href="#ref_13" class="fnanchor">[13]</a> +involuntary whisperings<a name="refanchor14"></a><a href="#ref_14" class="fnanchor">[14]</a> and the changes in the subject's respiration<a name="refanchor15"></a><a href="#ref_15" class="fnanchor">[15]</a> +and the murmuring of the spectators. To a less degree visual signs also +are involved: posture and facial expression of the subject, and movements +of eyes and lips.<a name="refanchor16"></a><a href="#ref_16" class="fnanchor">[16]</a> Even the heat radiating from the person's +body is supposed to have some influence.<a name="refanchor17"></a><a href="#ref_17" class="fnanchor">[17]</a> And my own experience +has taught me that surprising results may be obtained by the utilization +of the movements described in the preceding chapter. +</p><p> +It may be that these truly microscopic movements also play some +part in bringing about the success of some of the experiments in telepathy, +so-called, (transference of thought from one person to another, +ostensibly without any mediation of the senses known to us.) In spite +of the huge mass of "experimental evidence" which has been collected, +chiefly in England and in America, it appears to me that telepathy is +nothing but an unproven hypothesis based upon experimental errors.</p></div> + +<div class="footnote"><p><a name="Footnote_P_16" id="Footnote_P_16"></a><a href="#FNanchor_P_16"><span class="label">[P]</span></a> For registering the curves a Hering kymograph was used, with a +loop 2½ metres long. The kymograph rested on felt. With the aid +of the Marey model a pneumographic record was taken now of the +thoracic, now of the abdominal, breathing, never both simultaneously, +since this was extrinsic to my purpose, and it would have made the +whole experiment too complex. The time was recorded by means of +the Jacquet chronograph. For purposes of making more exact measurements +the acoustic current interrupter of Bernstein was used, attuned to +100 vibrations per second. But this necessitated such rapid revolution +of the drum of the kymograph that the curves were not compact enough +for purposes of demonstration. The levers were all fitted with micrometer +adjustments. They wrote tangentially and, except the one registering +the breathing curve, all points lay in one vertical line. The +error of deflection and that due to the rondure of the writing-surface +were both very slight on account of the comparative length of the +levers and the small extent of the excursions, and for that reason synchronous +points lie practically in one perpendicular. Only the breathing +curve has been moved somewhat to the left, 7.5 millimeters in figures <a href="#fig6">6</a> +and <a href="#fig7">7</a>, 2 millimeters in <a href="#fig8">figure 8</a>, 4.5 millimeters in <a href="#fig9">figure 9</a>. (When the +breathing was very profound, as occasionally happened, the error of deflection +would, of course, have to be taken into account.) The curves +here used as illustrations have been reproduced in the exact size of the +originals by the zinco-graphic method, though somewhat compressed +vertically in order to economize space.</p></div> + +<div class="footnote"><p><a name="Footnote_Q_17" id="Footnote_Q_17"></a><a href="#FNanchor_Q_17"><span class="label">[Q]</span></a> My own expressive movements, on the other hand, are as pronounced +as ever. I still find the attempt to suppress them as difficult now +as when I was working with the horse (<a href="#Page_57">page 57</a>). I could not, of +course, procure a curve of these movements of my own.</p></div> + +<div class="footnote"><p><a name="Footnote_R_18" id="Footnote_R_18"></a><a href="#FNanchor_R_18"><span class="label">[R]</span></a> Slight head movements accompanying the pulse-beat were until recently +regarded as the symptom of certain diseases of the vascular +system (the so-called symptom of Nusset), but H. Frenkel has now +shown them to exist also in normal individuals.<a name="refanchor19"></a><a href="#ref_19" class="fnanchor">[19]</a> I myself discovered +such movements (lateral as well as sagittal) more or less pronounced in +all the curves obtained from my subjects. The most striking case was +that of a young physician whose circulatory system was perfectly healthy. +In most instances I was able to note these oscillatory movements +directly and to count them without much difficulty. For purposes of +control the radial pulse was always determined at the same time. The +observation of the phenomenon appears to be especially easy in the +case of somewhat full-blooded individuals.</p></div> + +<div class="footnote"><p><a name="Footnote_S_19" id="Footnote_S_19"></a><a href="#FNanchor_S_19"><span class="label">[S]</span></a> In a special series of experiments a subject was instructed to execute +rapid head movements as minute and as evenly as possible. +These were registered objectively and at the same time I made judgments +concerning them. The results showed that my judgments were +most exact in the case of the most minute jerks. The thing that made +it especially easy to judge the movements of Mr. von Osten under normal +conditions, (<a href="#Page_220">page 220</a>), was their extraordinary evenness, such as I +have not met with in any other individual.</p></div> +</div> + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_141" id="Page_141"></a>[Pg 141]</span> +<h2 style="padding-bottom:1em;"><a name="CHAPTER_V" id="CHAPTER_V"></a>CHAPTER V</h2> + +<h2 style="padding-bottom:1em;">EXPLANATION OF THE OBSERVATIONS</h2> + + +<p><span class="firstwords">The</span> author having described the observations made +upon the horse, and having discussed the activities of the +questioner upon the basis of observations made objectively +and upon his own introspections, and having verified +the results thus obtained, by means of laboratory +tests,—we are now in a position to solve satisfactorily all +the problems which this interesting case has presented.</p> + +<p>That which is least difficult to understand is the +horse's seeming knowledge of language and particularly +his ability to answer questions, no matter by whom, or in +what dialect, they were put. As a matter of fact, it made +no difference who desired an answer, for the only person +upon whom the experiment depended was the questioner, +that is, the one who asked the horse to tap. We have +everywhere designated this person as the experimenter +or questioner. It was he who gave the directions, and +since all that were involved were visual signs, the drama +in which Hans appeared as the hero, was nothing but a +pantomime. All speech was superfluous and, except +in so far as the tone of voice in which it was spoken +was soothing or reprimanding, it was quite unintelligible +to the horse.</p> + +<p>From the foregoing, the reader understands without +further explanation Hans's ability to count and to make +computations. If the number of taps had depended +solely upon the length of time and the angle at which<span class="pagenum"><a name="Page_142" id="Page_142"></a>[Pg 142]</span> +the questioner bent forward, the horse would have been +able to tap any number desired. Since, however, only +the right foot was employed, the left one being used at +most for making a final tap, the number of taps had an +upper limit which was due to the fatigue of the animal. +This limit was about 100. That it was possible to ask +such questions as: "How many times is 100,000 contained +in 654321?", and thus to give problems involving +millions, is perfectly clear.</p> + +<p>All wonderful feats of counting and computation which +were accomplished while thus experimenting with the +horse are to be accredited, not to the horse, but to +the questioner. If such is the case, they certainly cannot +be considered astonishing. Thus, when to the question, +"How many of the gentlemen present are wearing straw +hats?" the horse answers correctly in accordance with +the wording of the question and omits the straw hat of +a lady, then Mr. von Osten is the guide. It is no wonder +that Hans never showed the slightest excitement when +confronted with difficult problems, nor that it apparently +took no time whatever to solve them.</p> + +<p>Hans, however, was also a faithful mirror of all the +errors of the questioner. Aside from mistakes due to +occasional interruptions on the part of visitors, these +errors had two sources: faulty computation and inadequate +concentration—i. e., aside from arithmetical errors +on the part of the questioner, were his premature or belated +movements. Since both of these factors might be +operative, the following three possibilities arise.</p> + +<p>(<i>a</i>) The questioner computes correctly but does not +move at the proper moment. Nearly all the errors which +had been accredited to the horse, were of this kind.</p> + +<p>A part of these errors had the appearance of being<span class="pagenum"><a name="Page_143" id="Page_143"></a>[Pg 143]</span> +significant, that is, they might be interpreted as a misapprehension +of the question. If, for instance, instead +of a sum only one of the quantities was given, or, if instead +of a product only one of the factors was given, it +might be interpreted that the horse simply wished to repeat +the problem. Thus, Mr. von Osten in response to the +question: "How much is 3 times 5?", twice in succession +received the answer, "3", and upon my question, "How +much is 3 plus 4?" he answered, "3", and to "How +much is 2 times 6?" he tapped 6, and to "What is one-fourth +of 36?" 4. In part (certainly in the second and +third example cited) an individual quantity or factor +had been emphasized in the consciousness of the questioner +(cf. <a href="#Page_105">page 105</a>) and in part the reactions were due +to chance. Thus, when Mr. Hahn asked the question: +"What is one-half of 10?", he received the following +responses: 2 and 10, and then 17 and 3. To this class +belong also, the tests made by the Commission of September +and reported in <a href="#SUPPLEMENT_III">Supplement III. (See page 255)</a>.</p> + +<p>Other errors, even though they may not have appeared +to be significant, might yet have been characterized as +mistakes due to speed; as when, e. g., Hans made an error +of one unit—and sometimes, though less frequently, of +two units—too much or too little in his response. One +might be led to believe that Hans had not made an error +of calculation but merely of counting in the process of +giving his result, which always had to be done by the +cumbersome method of tapping. As a matter of fact, +the trouble lay in the wrong degree of concentration on +the part of the questioner: In errors of +1, tension was +too slight, in those of -1, it was too great (see <a href="#Page_91">page 91</a>). +This comes out clearly in a comparison of the two more +extensive series which I took in the case of Mr. Schil<span class="pagenum"><a name="Page_144" id="Page_144"></a>[Pg 144]</span>lings. +During the first series, he was well disposed, and +was able to concentrate effectively, while during the +second, he was nervous and easily diverted. This difference +in intensity of concentration in the case of the +two series is attested, not only subjectively by Mr. Schillings's +introspective statement, but may be measured +objectively by means of the number of final taps which +the horse gave with his left foot during these two series. +We saw (<a href="#Page_94">page 94</a>) that these final taps were always a +sign of intense concentration and, as a matter of fact, +one-half of the horse's responses to Mr. Schillings during +the first series were made in this way; whereas, in the +second series, only one-third were of this sort. (I, myself, +was never able to get, without conscious control, a +greater number of this type of response.) We may +therefore say that, in the first series we had a high degree +of tension, or concentration, whereas, in the second +series, we had a low degree. The errors distribute themselves +over the two series as follows:</p> + +<div style="font-size:.8em;"> +<table border="0" width="85%" cellpadding="1" cellspacing="0" summary="Test Result Table 16" align="center" +style="margin-top:1.25em;margin-bottom:1.25em;"> +<tr> +<td align="left" width="15%"> </td> +<td align="left" width="25%"> </td> +<td align="left" width="10%"> </td> +<td align="center" width="10%">+1</td> +<td align="center" width="10%">+2</td> +<td align="center" width="10%">-1</td> +<td align="center" width="10%">-2</td> +<td align="center" width="10%"> </td> +</tr> +<tr valign="top"> +<td align="left" width="15%">Series I</td> +<td align="left" width="85%" colspan="7">(31 tests)</td> +</tr> +<tr> +<td align="left" width="15%"> </td> +<td align="left" width="25%">Correct responses</td> +<td align="left" width="60%" colspan="6">: 87%</td> +</tr> +<tr> +<td align="left" width="15%"> </td> +<td align="left" width="25%">Incorrect "</td> +<td align="left" width="10%">:</td> +<td align="center" width="10%">0%</td> +<td align="center" width="10%">0%</td> +<td align="center" width="10%">13%</td> +<td align="center" width="10%">0%</td> +<td align="center" width="10%"> </td> +</tr> +<tr valign="top"> +<td align="left" width="15%">Series II</td> +<td align="left" width="85%" colspan="7">(40 tests)</td> +</tr> +<tr> +<td align="left" width="15%"> </td> +<td align="left" width="25%">Correct responses</td> +<td align="left" width="60%" colspan="6">: 40%</td> +</tr> +<tr> +<td align="left" width="15%"> </td> +<td align="left" width="25%">Incorrect "</td> +<td align="left" width="10%">:</td> +<td align="center" width="10%">40%</td> +<td align="center" width="10%">8%</td> +<td align="center" width="10%">2.5%</td> +<td align="center" width="10%">0%</td> +<td align="center" width="10%">(and 9.5%</td> +</tr> +<tr> +<td align="left" width="15%"> </td> +<td align="left" width="25%"> </td> +<td align="left" width="10%"> </td> +<td align="center" width="10%"> </td> +<td align="center" width="40%" colspan="4">other kinds of errors.)</td> +</tr> +</table> +</div> + +<p>We find in Series I no "+1" errors, but only "-1" +errors; in series II, on the other hand, the errors are +almost exclusively of the "+1" category, equaling the +number of correct responses, and there is only one +"-1" error. A series obtained in the case of Mr. von +Osten is almost as satisfactory an illustration. When he<span class="pagenum"><a name="Page_145" id="Page_145"></a>[Pg 145]</span> +first began to take part in tests in which the procedure +was the one we characterized as "without knowledge" +and had to note their complete failure, he was thrown +into such confusion that the responses in the case of +procedure with knowledge were also incorrect. The +errors there were always +1, (whereas those in the case +of procedure with knowledge, which were due to quite +different causes, were very great and inconstant.) The +number of +1 errors obtained on this occasion comprises +one-fourth of all the plus errors which were ever +obtained in the case of Mr. von Osten during the entire +course of these experiments. Finally, I would mention +two examples of my own. In the course of my very first +attempts with Hans I obtained, as I said on <a href="#Page_89">page 89</a>, +three responses in a total of five which exceeded the correct +result by 1. This I would explain by the fact that +although I employed a high degree of concentration, I +nevertheless was somewhat skeptical. The result was a +certain deficiency in the degree of concentration. A +second example which I would cite is taken from the +period in which I had already discovered the cue to +Hans's reactions and goes to show that I was then still +able to eliminate the influence of this knowledge and to +work ingenuously. To the question, "How much is 9 +less 1?" I, momentarily indisposed, received the answer +10, and then six times in succession the answer "9", and +finally the correct response, "8".</p> + +<p>Errors of another kind—the not infrequent offenses +against the very elements of counting and the fundamental +arithmetical processes—were regarded in part +as intentional jokes and by an authority in pedagogy as +a "sign of independence and stubbornness which might +also be called humor". Hans emphatically asserted that<span class="pagenum"><a name="Page_146" id="Page_146"></a>[Pg 146]</span> +2+2 was 3 or he would answer questions given in immediate +succession as follows: "How many eyes have +<a name="tn_png_153"></a><!--TN: Double quote added after "you?"-->you?"—2. "How many ears?"—2. "How many tails?"—2. +These errors, as a matter of fact, evince neither +wit nor humor, but prove incontrovertibly that Hans had +not even mastered the fundamentals.</p> + +<p>Many of the errors baffle every charitable attempt at +interpretation. These gave the horse the reputation of +capriciousness and unreliability. If Hans designated the +tone "e" as the seventeenth, or "g" as the eleventh, or +when he called Friday the 35th day of the week or +believed 50 pfennige to be worth only 48, the cause for +these responses lay either in the insufficient degree of +tension on the part of the questioner (as in the first +three examples) or in the extravagant expenditure of the +same (as in the last case). If, therefore, the horse +at times would "hopelessly flounder" which would seem +to be indicated by tapping now with the right and now +with the left foot, then as a matter of fact, this form of +reaction came about as was described on <a href="#Page_61">page 61</a>, with +this difference that there we had to do with voluntary +controlled movements on the part of the questioner, +whereas here, they are the result of an unsuitable degree +of tension which expressed itself in frequent and disconcerting +jerks. Besides the answer 3, this so-called +floundering was the only reaction the average person +could obtain from the horse in the absence of Mr. von +Osten and Mr. Schillings. It would however occur +also in the case of these gentlemen and would be received +by them with resentment when in truth it was +Hans's greatest feat, for he showed his extremely keen +reaction upon every movement of the questioner. To +this group belong also the errors in the case of higher<span class="pagenum"><a name="Page_147" id="Page_147"></a>[Pg 147]</span> +numbers, the sole cause of which lay in the difficulty with +which tension could be maintained and the body kept +motionless for so long a period. These errors occurred +in accordance with a certain law. If, for instance, a certain +test repeatedly evoked incorrect responses, the +questioner would gradually increase the duration of +tension and would thus come a little nearer to the desired +goal with every test. In this way, Mr. von Osten desiring +30 as an answer obtained consecutively the responses, +25, 28, 30; and I, myself, for the answer 20, received consecutively +the responses 10, 18, 20 (see also the laboratory +tests, <a href="#Page_105">page 105</a>). Sometimes too, the questioner would +flag in his efforts before the goal was reached. Thus in +one of my first tests, I received for the answer 11 the +following responses: 1, 4, 5, 7, 4. I was unable to get +beyond 7. In other instances, the horse responded first +with too few and then with too many taps. The correct +response therefore could only be obtained after an appreciable +amount of gauging of tension, as in target +practice there must be a gauging of distance. (See +<a href="#Page_92">page 92</a>). In this way Mr. von Osten obtained for 10 +the responses 8, 8, 11, 10, and Mr. Schillings for 17, +received 9, 16, 19, 18, 18, 14, 9, 9, and finally, after some +efforts, 17 taps. Thus there was a rise from 9 to 19, +then a fall back to 9 and after eight tests the correct +response. As long as we attempt to explain this fact +as error on the part of the horse, so long will it remain +inexplicable, but the moment we regard it from the point +of view of the psychology of the tension of expectation, +it becomes perfectly plain.</p> + +<p>The same holds true for the curious predilection which +Hans appeared to have for the numbers from 2 to 4, +especially for 3 (see <a href="#Page_68">page 68</a>). As a matter of fact the<span class="pagenum"><a name="Page_148" id="Page_148"></a>[Pg 148]</span> +cause of this lies in nothing other than the inadequate concentration +of attention on the part of the questioner and +less often in an extravagant expenditure of concentration, +which explodes immediately after the first tap on the +part of Hans (as in the case of my first tests); but usually +the cause lay in a complete lack of concentration, +though the same result may be produced by various +causes. It is usually after 2 to 4 taps of the horse's foot +that the questioner, who does not concentrate, makes his +first move which naturally puts an end to the tapping +on the part of the horse. As a rule this jerk follows immediately +upon the second tap. (On the other hand, relaxation +of attention is very difficult upon the first tap. +See <a href="#Page_95">page 95</a>). The questioner, however, would expect +further tapping and therefore would not bring his body +back to a completely erect position and the result would +be a 3, the last unit of which would be given by the +final tap with the left foot. Here we also obtained light +as to the answers which Hans gave in those tests in +which the method was that of "procedure without +knowledge". These responses had nothing to do with +the problem, for neither the horse nor any one else knew +the solution. But in the horse's responses the degree of +tension of the questioner's concentration was faithfully +mirrored. An experimenter who was as skillful in concentrating +as Mr. von Osten, obtained—almost without +exception—very high numbers, whereas one whose concentration +was slight would receive in response to nearly +all questions the answers 2, 3 or 4. Thus, the Count zu +Castell received in response to seventeen questions the answer +2, three times, the answer 3, six times, and the +answer 4, four times, two answers being accidentally correct.</p><span class="pagenum"><a name="Page_149" id="Page_149"></a>[Pg 149]</span> + +<p>Another group of errors was characterized as stubbornness +on the part of Hans, such as his persistence in +repeating an incorrect response, or his repetition of a +former correct answer in response to later questions +where it was perfectly senseless. During a demonstration +before a large number of persons, I held a slate with the +number 13 upon it within the horse's view and also +within view of the spectators. I, myself, did not know +what number was written on the slate. Having been +asked to tap the number, Hans responded by tapping +5. The grand-stand shouted "Wrong!" I asked Hans +to try again. Four times in succession he answered 5. +At another time Mr. von Osten and I each whispered a +number (7 and 1, respectively,) into the horse's ear and +asked him to add the two. Three times in succession he +tapped 11. After the test had been repeated in accordance +with "procedure with knowledge" and a correct +response had been received, we tried once more a test of +"procedure without knowledge". Again, he responded +with an 11. On a third occasion, I asked Hans to tap 5. +He responded with a 4 and then, correctly, with a 5. +Thereupon, I asked him to tap 6. Again, he responded +with a 4. Then I asked him to tap 7. Once more he responded +with a 4, and only when I proceeded to count +aloud did he tap 7 correctly. I had him repeat the 7 and +then went over to 9. Promptly he responded with another +7. In these cases, which by-the-way were not very +frequent, we have to do, not with stubbornness on the +part of Hans, but with the persistence of that number +in the consciousness of the questioner. Modern psychology +has recognized this tendency of ideas, which +have once been in consciousness, to reappear on other +occasions even though they are wholly inappropriate.<span class="pagenum"><a name="Page_150" id="Page_150"></a>[Pg 150]</span> +It has been termed "perseverative tendency." (<a name="tn_png_157"></a><!--TN: Double quote removed after "Perseverationstendenz"-->Perseverationstendenz).<a name="refanchor21"></a><a href="#ref_21" class="fnanchor">[21]</a></p> + +<p>While the errors thus far discussed appeared sporadically +in long series of correct responses, there still might +be observed at times a massing of errors, usually at the +beginning of a day of experimentation or at the beginning +of a new series. We were regularly told that Hans +always had to have time to adjust himself to new circumstances. +The records often showed comments such +as these: "After a number of practice tests the horse +appears particularly well disposed", or "Hans, at first +inattentive, does not respond. Suddenly he gets the hang +of things". Different questioners who worked with the +horse required different lengths of time to obtain proper +responses. Some needed a quarter of an hour, others +scarcely half a minute. I, myself, found that in the +degree in which I learned to control my attention, in that +degree did this phenomenon tend to disappear, but would +reappear the moment I became indisposed. From this +we see that, instead of attributing all sorts of mental +characteristics, such as stubbornness, etc., to the horse, +we should lay them to the account of the questioner. As +a matter of fact we find that this "getting into the sweep +of things", i. e. the overcoming of psycho-physical +inertia, has long been known in the case of man and has +been experimentally determined and called "Anregung" +(excitation) by the psychiatrist, Kraepelin,<a name="refanchor22"></a><a href="#ref_22" class="fnanchor">[22]</a> and his +pupil, Amberg.<a name="refanchor23"></a><a href="#ref_23" class="fnanchor">[23]</a> A massing of errors toward the end +of a long series occurred only when the questioner was +fatigued. There was nothing which had to be interpreted +as fatigue or as indisposition on the part of the horse, +(except in the few cases of very large numbers, cf. +<a href="#Page_67">page 67</a>). To be sure, Mr. von Osten always offered<span class="pagenum"><a name="Page_151" id="Page_151"></a>[Pg 151]</span> +these two excuses. That they were without warrant is +shown by the fact that Hans, after appearing indisposed +or fatigued while working with one questioner, would +nevertheless react promptly and correctly a moment later +for some other experimenter, and furthermore, when +working with me, the number of his correct responses +would rise or fall with my own mental disposition.</p> + +<p>Finally, I would here note a rather interesting observation +for which I am indebted to Mr. Schillings and the +Count zu Castell. They had noticed, independently of +each other, that the horse would often fail to react +when for any length of time he was given problems dealing +with abstract numbers, even though they were of the +simplest kind; but that he would immediately improve +whenever the questions had to do with concrete objects. +They believed that Hans found applied mathematics more +interesting, and that abstract problems, or those which +were altogether too elementary, bored him. The Count +zu Castell furthermore noticed that the responses tended +to be more correct as soon as he had the horse count +objects which he, himself, (Castell) could see during the +test. Quite in accord with this is the statement to be +found in the report of the September-Commission, in +which we find this note in a discussion of the arithmetical +problems (not involving visible objects), which the gentlemen +already mentioned had given the horse. "The +horse responded with less and less attentiveness and appeared +to play with the questioner." Here again, that +was looked for in the animal which should have been +sought in the man. Mr. Schillings was capable of intense, +but not continued concentration and it was he who +was bored, and not the horse. And it was the Count zu +Castell and not the horse that found it necessary to in<span class="pagenum"><a name="Page_152" id="Page_152"></a>[Pg 152]</span>voke +the aid of perceptual objects to bring his attention +to the proper height of concentration.</p> + +<p>The reader will see that thus far I have supposed the +horse to be a never-failing mechanism and that I have +placed all errors to the account of the questioner. The +horse never failed to note the signal for stopping and +therefore never was the immediate cause of an error. It +is not to be denied that now and then he would cease +tapping spontaneously and in this way would become +the cause of an error. We have no data on this point, but +undoubtedly the horse's share in the total number of +errors was very slight.</p> + +<p>(<i>b.</i>) Another source of error was faulty computation +on the part of the questioner. The questioner made the +signal for stopping when the expected number of taps +had been reached. The horse faithfully mirrored the +miscalculation of the questioner. I have knowledge of +only one such case. The journals report that once Mr. +von Osten, when someone called to his attention that Hans +had indicated the wrong day of the week, replied: "Yes, +you are right, it was not Thursday, but Friday," whereupon +Hans being asked again, promptly responded correctly. +This appeared to the reporter in question as proof +of the subjective influence of Mr. von Osten upon the +horse.</p> + +<p>(<i>c.</i>) When errors in calculation and failures in proper +concentration combine, i. e. when the questioner makes a +mistake in calculation because he is excited or inattentive +and for the same reason does not make the movement, +which is the signal for stopping, in accordance +with the number which he deems to be the correct answer, +then the result is usually wrong, but it may be correct +in the few cases in which the two errors exactly +compensate each other. Nothing has been so effective<span class="pagenum"><a name="Page_153" id="Page_153"></a>[Pg 153]</span> +in establishing Hans's reputation, nothing has brought +him so many followers, as these cases in which he, rather +than his mentor, has been in the right. Compared with +the mass of cases in which Hans was wrong these latter +cases are diminishingly few in number, yet these few +made such an impression upon the observers that their +number tended to be overestimated. As a matter of fact, +I have been able to discover records of only seven +such cases. Two of these were reported by the Count +zu Castell. On the 8th of September, he entered the +horse's stall, alone, and believing it to be the seventh +day of the month, he asked Hans the date. The horse +responded correctly with 8 taps. At another time he +held up before Hans a slate on which were written the +numbers 5, 8 and 3 and asked the horse to indicate their +sum which in the momentary excitement, vaguely appeared +to Castell to be 10. To his chagrin he noticed +that Hans continued to tap. Thereupon he intentionally +remained motionless until the horse had stopped tapping +spontaneously—as he thought—at 16. (The newspapers +reported that the numbers to be added had been 5, 3, and +2; that the questioner had expected the answer 11, but +that Hans had in three tests always ceased tapping at +10.) In both cases the questioner regarded the answers +of the horse as wrong and recognized his mistake when +his attention was called to it. I, myself, had the same +experience. One time I received in response to the question, +"What day of the week is Monday?", the answer +2, although I had expected the answer 1; at another time +I asked, "How much is 16 less 9?", and the horse responded +with 7 taps, although I had erroneously expected +5. I noticed my mistake only when my attention was +called to it by one of those present. Another example is<span class="pagenum"><a name="Page_154" id="Page_154"></a>[Pg 154]</span> +related by Mr. Schillings. A row of colored cloths lay +before Hans. Beside them stood an army officer. Pointing +to the latter's red coat Mr. Schillings asked the horse +to indicate, by means of tapping, the place in the row +where a piece of the same color lay. Hans tapped eight +times, but Mr. Schillings reprimanded him because the +red piece was, as a matter of fact, second in the row. +Upon a repetition of the test, Hans again tapped 8. (By +some, the facts are recounted as having been the other +way round; viz.: Hans tapped 2 instead of 8. This of +course would call for a different explanation.) It was +noticed that at the place which would be indicated by +eight taps there was not a red piece but a carmine colored +piece of cloth. A newspaper reports, somewhat vaguely, +a sixth case as follows: Hans was asked to spell the name +"Dönhoff" and began correctly: "Dö". Mr. von +Osten, who somehow began to think of another name, +"Dohna", interrupted him and wished to correct him by +suggesting o instead of ö (i. e., 2 taps instead of 3). +Hans, however, <a name="tn_png_161"></a><!--TN: Comma removed from before "continued"-->continued to spell the entire word with +the greatest equanimity. He had not erred. A similar +experience is reported by Mr. H. von Tepper-Laski, the +well known hippologist. Although the details have +slipped from his memory, he reports that in the case in +question the correct answer was thrice refused by the +questioner who thought that the horse's answer was incorrect. +Hans, upon being severely reprimanded in a +loud and harsh tone of voice, turned about as if disgusted +with the injustice of the man and made straight for his +stall.—It is clear that in the cases described we are not +dealing with accidentally correct responses, for in nearly +every case the test was repeated a number of times and +the same responses were received each time. As a mat<span class="pagenum"><a name="Page_155" id="Page_155"></a>[Pg 155]</span>ter +of fact, my own introspection convinced me that the +third and fourth cases were surely, and the first and +sixth were very probably, due to insufficient concentration +on the part of the questioner. Accordingly there is +everywhere in these cases a difference of +1 or +2 between +the number thought of and the number tapped +(see <a href="#Page_92">page 92 f.</a>). The data in the second and fifth +and still more in the seventh case were too meager to +warrant an attempt at explanation, for it is not even +known whether Hans responded with more or fewer taps +than was expected by the questioner. It is unfortunate +that a more complete record was not made.</p> + +<p>The frequent and intentional attempts of Mr. von +Osten to induce the horse to give an incorrect response,—which, +by-the-way, were regularly unsuccessful—belong +only apparently to this group. Thus he asked, e. g., +"2 times 2 is 5, is it not?" "3 times 3 is 8?", etc., but +Hans refused to be misled, and responded correctly. +This was from the very beginning one of the main arguments +for independent thinking on the part of the horse. +The actual procedure was as follows, even though the +questioner had said "2 times 2 is 5", there still was present +in his consciousness the number 4. I, myself, would +think either of the first member of the equation, i. e., 2 +times 2, in which case Hans would respond with 4 taps or +I would have in mind the second member, i. e., 5, in +which case he would respond with 5 taps. Never did I +succeed in thinking of both at the same time. The association +between the thought "2 times 2" and the concept +"4" is so close and supported by so many other associations +that the attempt to form a new one, that is at complete +variance with all these, is futile. One may say +"2 times 2 equals 5" but it is impossible to conceive it.</p><span class="pagenum"><a name="Page_156" id="Page_156"></a>[Pg 156]</span> + +<p>Let us turn now, from the tests in counting and computation +to those in reading. We have seen that Hans +manifested his seeming knowledge of language symbols +in a threefold manner: he might approach a slate on +which was written the symbol asked for, or he would +indicate its location in a series of slates by means of tapping, +or finally by means of so-called spelling of the +word which was written upon a slate or placard. The +responses by means of approaching a placard were very +often unsuccessful, while indications by means of tapping +were scarcely ever unsuccessful. If it were true that +higher intellectual <a name="tn_png_163"></a><!--TN: "proceesses" changed to "processes"-->processes<a name="FNanchor_T_20" id="FNanchor_T_20"></a><a href="#Footnote_T_20" class="fnanchor">[T]</a> were here involved, then +the converse would have been expected, for tapping required +not only the ability to read, but also the ability to +count. If, on the other hand, we assume that the horse +simply followed the directions given by the questioner's +movements, this seeming difficulty resolves itself, for it +would be more difficult for Hans to perceive the signs +which he receives while moving than those which he receives +while tapping. When we recall that it was easier<span class="pagenum"><a name="Page_157" id="Page_157"></a>[Pg 157]</span> +to direct the horse to a placard near the end of a row +than one nearer the center (see <a href="#Page_81">page 81</a>), we can +readily understand how it was that during the experimentation +carried on by the September-Commission (<a href="#SUPPLEMENT_III">Supplement +III; page 255</a>), Hans was able to point out immediately +the placards on which were written the names "Castell" +and "Stumpf", for they were at the two extreme +ends, but was unsuccessful in locating the one on which +was written the name "Miessner" which was not a bit +more difficult to read, but was located at the fourth place +in the row. He first approached the fifth card, then upon +repetition of the test he pointed out the other neighboring +tablet, viz., the third.</p> + +<p>In spelling, Hans was quite indifferent whether his +table with the eighty-four number signs upon it stood +before him, for he had no knowledge of letters. Neither +Mr. von Osten nor Mr. Schillings required it, for the +former knew the table by heart and Mr. Schillings told +me that before every test he made a note of the +numbers which were necessary to indicate the required +letters, trusting in this way to control the responses +of the horse and never guessing that by so doing +he was making it possible for the horse to answer correctly. +The newspaper reports aroused much interest at +the time by stating that Hans was able to spell such +proper names as "Plüskow" and "Bethmann-Hollweg", +even to putting in the difficult "w" and "th". The +friends of Mr. von Osten at the same time called attention +to the exquisite auditory acuteness of the horse which +enabled him to perceive the aspirated "w" and to discriminate +between the "th" and "t", (the "th" is +softer than the "t" in German.—<i>Translator</i>). This ex<span class="pagenum"><a name="Page_158" id="Page_158"></a>[Pg 158]</span>planation, +of course, must have appeared somewhat +daring even at that time.</p> + +<p>Hans was quite guiltless of the many limitations imputed +to him concerning his knowledge of symbols. That +he was unable to read capitals or Latin script was merely +a vagary of the master, like the belief that it was necessary +to confine one's self in one's questions to a certain +vocabulary and to a certain form. Mr. von Osten's apparent +failure to elicit responses from the horse on topics +of which it was ignorant is a beautiful illustration of the +power of imagination. Mr. von Osten was convinced +from the very first that Hans could not answer such questions. +When the belief in success was lacking, of course +there was not the requisite amount of concentration +which, alone, leads to perceptible expressive movements +and thus elicits a successful reaction on the part of the +horse.</p> + +<p>Mr. Schillings, owing to his great impressionability, +remained long under the spell of Mr. von Osten's point +of view. Thus I find in the record of the September-Commission +that the question "How much is 3 plus 2?" +was answered incorrectly by Hans, but he responded correctly +the moment Mr. Schillings replaced the word +"plus" which was "tabooed", by the word "and". For +a long time also he could receive no response to questions +put in French until one day he made the discovery +that, curiously enough, the animal never responded adequately +unless he himself firmly believed in the possibility +of success. It is noteworthy that the Count zu +Castell, independently of Mr. Schillings, made the same +discovery. Mr. Schillings made his curious discovery—which +he was unable to interpret, but which aroused some +suspicion—on the following occasion. One day—whether<span class="pagenum"><a name="Page_159" id="Page_159"></a>[Pg 159]</span> +accidentally or because his prejudice was temporarily +overcome—he commanded; "Dis deux!". Hans responded +promptly with 2 taps. He was greatly surprised +and believed that Hans had gotten hold of the +French by hearing it spoken in his environment. Possibly +he understood also "trois" and "quatre"? He put +the questions and received correct responses. He asked +again, "dix", "vingt", and so on to "soixante". At +<a name="tn_png_166"></a><!--TN: em-dash changed to hyphen between "soixante" and "six"-->"soixante-six" he became doubtful. Indeed, Hans +failed him. At "quatre-vingt", the game began again. +"Cent", again, succeeded. The old saying that "Faith +will move mountains" was verified once more.<a name="FNanchor_U_21" id="FNanchor_U_21"></a><a href="#Footnote_U_21" class="fnanchor">[U]</a></p><span class="pagenum"><a name="Page_160" id="Page_160"></a>[Pg 160]</span> + +<p>Hans's seeming knowledge of the value of coins and +cards, of the calendar and the time of day, as well as his +ability to recognize persons or their photographs, can +now be readily understood. In all of these cases, we had +to deal, in so far as knowledge is concerned, only with +that of the questioner,—the horse simply tapped the +number the questioner had in mind. The meaning which +was supposed to be expressed by the tapping never +existed as far as Hans was concerned; it was only in the +mind of the questioner that the concepts: ace, gold, +Sunday, January, were associated with "1", etc. The +same was true with regard to all other wonderful feats +of memory. The sentence: "Brücke und Weg sind vom<span class="pagenum"><a name="Page_161" id="Page_161"></a>[Pg 161]</span> +Feinde besetzt", (The road and the bridge are held +by the enemy), which was given to the horse one day and +correctly repeated by him on the following day, was not +an answer elicited from the horse by means of a question, +but rather a system of automatic reactions which were +induced by certain involuntary movements of the questioner +as stimuli. Far from showing a wonderful +memory in these feats—as is claimed for him by the +very non-critical compiler, Zell<a name="refanchor28"></a><a href="#ref_28" class="fnanchor">[28]</a>—Hans, on the contrary, +has at his service a remarkably small number of associations. +For, besides possessing the powers of any +ordinary horse, he recognizes only a few meager visual +signs. To be sure, we find in the literature a horse that<span class="pagenum"><a name="Page_162" id="Page_162"></a>[Pg 162]</span> +was said to have recognized 1500 signals,<a name="refanchor29"></a><a href="#ref_29" class="fnanchor">[29]</a> but all proof +is lacking and the report is so meager that we cannot +discover whether these signs were auditory or visual.<a name="FNanchor_V_22" id="FNanchor_V_22"></a><a href="#Footnote_V_22" class="fnanchor">[V]</a></p> + +<p>Having thus disposed of all questions concerning the +horse's apparent feats of reason and memory, let us turn +to those in the field of sensation. We shall begin with +vision. That Hans was unable to select colored pieces +of cloth merely upon the basis of color quality, without +reference to their order, was shown in <a href="#CHAPTER_II">Chapter II</a>. It +would, however, be somewhat hasty to infer color-blindness +from this fact, as did Romanes<a name="refanchor32"></a><a href="#ref_32" class="fnanchor">[32]</a> on the basis of +similar unsucessful responses on the part of a chimpanzee +("Sally" of the London Zoölogical Garden). It +is much easier to explain the failure of the horse than +that of the monkey on the basis of intellectual poverty, +a poverty of associative activity. It presumably can +discriminate between the various colors, but it cannot +<a name="tn_png_169"></a><!--TN: "asociate" changed to "associate"-->associate with these their names. The existence of +chromatic vision in the lower forms is by no means as +unquestionable as is assumed by popular thought. Even +teleological considerations which are often brought forward +(especially that of the ornamental and protective +coloring of so many animals) can never do more than +establish a certain probability. For definite proof, we +need data given by observation (we have none in this +case), or experimental evidence. Such evidence we +have, but it is insufficient in quantity and unfortunately +most of it was obtained under inadequate experimental<span class="pagenum"><a name="Page_163" id="Page_163"></a>[Pg 163]</span> +conditions.<a name="FNanchor_W_23" id="FNanchor_W_23"></a><a href="#Footnote_W_23" class="fnanchor">[W]</a> We know nothing regarding chromatic +vision in the horse, though we have often had trained +horses which apparently possessed color discrimination. +The earliest report of this kind I find in a work published +in the year 1573.<a name="refanchor36"></a><a href="#ref_36" class="fnanchor">[36]</a> Here we read that a number of +Germans exhibited two horses in Rome which could, +upon request of their masters, point out those persons +among the spectators who were wearing stockings of +any designated color. The passage, "conoscevano i +colori", (they recognized the colors,) proves nothing and +no one has ever heard, even in modern times, of a horse +that actually knew colors.</p> + +<p>Nor did Hans possess anything like that high degree +of visual acuity which had been attributed to him. He +was supposed to be able to read easily at a distance small, +almost illegible script, which we ourselves could decipher +only with the greatest difficulty close at hand. It was +also supposed that he could distinguish ten-and fifty-<span class="pagenum"><a name="Page_164" id="Page_164"></a>[Pg 164]</span>pfennig +pieces whose faces had become worn beyond +recognition for us. None of these accomplishments have +stood the test. We have no reason to believe that Hans +can see the objects about him more clearly than other +horses, regarding whom one usually assumes that they +receive only vague visual impressions. Horses do not +as a rule seem to be near-sighted as is often asserted by +the layman, but rather somewhat far-sighted, or if we +may believe Riegel,<a name="refanchor37"></a><a href="#ref_37" class="fnanchor">[37]</a> who tested some six hundred +horses, they probably have normal vision. But we are +told that many horses—and according to some authors all—have +an innate imperfection which detracts considerably +from the clarity of vision. This imperfection +consists in an irregular formation of the sclerotic coat +and of the lens of the eye.<a name="refanchor38"></a><a href="#ref_38" class="fnanchor">[38]</a> The two organs do not have +the same refraction in all parts. As a result, objective +points are not imaged as points upon the retina. (Hence +the name: astigmatism, i. e., "without points", for this +disorder.) The retinal image of the object is not only +vague, but also distorted.<a name="FNanchor_X_24" id="FNanchor_X_24"></a><a href="#Footnote_X_24" class="fnanchor">[X]</a></p> + +<p>Many will doubt whether with such imperfect images +an animal can react to directives so minute, as we have +asserted to be true in the case of Hans. In considering +this question we must distinguish between the directives +for pointing out colors and the directives for tapping and +for head movements on the part of the horse. In point<span class="pagenum"><a name="Page_165" id="Page_165"></a>[Pg 165]</span>ing +out and bringing forth pieces of colored cloth there +is involved the perception of an object at rest, viz.: +the direction of the questioner who is standing quietly; +whereas in the case of responses by means of tapping the +stimulus is the horse's perception of the questioner's +movements. Now, the construction of the horse's eye, +as described above, is not favorable for the perception +of objects (so-called acuity of vision). This may partly +account for the slight success of the horse in those tests +in which he was required to select a piece of cloth of a +designated color, in so far as these commands were not +accompanied by calls or exhortations. Where human +observers averaged eighty per cent correct responses +(<a href="#Page_135">page 135</a>), Hans, under similar conditions was successful +in only one-third of the tests. In his errors he +was also wider of the mark than were the human observers +(<a href="#Page_82">page 82</a>). The object perceived, to be sure, is +a large one, viz.: the questioner, and he at close range. +We must therefore consider more specifically what are +the determining factors that make for success or failure +of the response. First of all, the innocent questioner +very often did not designate the direction with sufficient +clearness. Furthermore, Hans presumably was not +able to discriminate sufficiently between the direction of +the experimenter's eye and that of his head, which two +directions did not always coincide. Finally the horse's +attention was often diverted, while he was running toward +the piece indicated, by the other pieces lying to the right +and to the left, and for this reason the addition of a single +piece to the otherwise unchanged row of five pieces +tended to decrease greatly the chances of success.</p> + +<p>The case is different with the perception of the directive +signs for tapping, for nodding and shaking the head,<span class="pagenum"><a name="Page_166" id="Page_166"></a>[Pg 166]</span> +etc., all of which require the perception of movements. +This is not necessarily more difficult on account of the +imperfect constitution of the tissues that serve for the +refraction of light. Some authors even aver that this +facilitates the perception of moving objects. This view +was first advanced by the excellent ophthalmologist, R. +Berlin<a name="refanchor39"></a><a href="#ref_39" class="fnanchor">[39]</a> of Stuttgart. In arriving at this view he was +guided by the following considerations. The peculiar +form of astigmatism of the lens of the horse's eye, which +Berlin has described as "butzenscheibenförmig",<a name="FNanchor_Y_25" id="FNanchor_Y_25"></a><a href="#Footnote_Y_25" class="fnanchor">[Y]</a> because +it appears in the form of a series of glossy concentric +circles around the lens nucleus, has the property of enlarging +the pathway (and with it the rapidity) of moving +retinal images. If we take a speculum by means of which +a view may be had of the interior of the eye, and fixate +a definite point on the retina of the horse, and then +make a slight movement of the head horizontally, we +find that the point fixated moves—apparently at least—toward +the border of the pupil. In a normally constructed +eye this seeming movement will be in a straight +line, while in the eye of the horse, (according to Berlin), +its path is curved, and therefore longer. Berlin believes +that the same thing which here occurs in the case of this +merely apparent movement, must also happen when an +external moving object is imaged on the horse's retina. +Its pathway, too, will be curved, and therefore longer, so +that if the head of Mr. von Osten moves past the animal's +eye, then the image on the horse's retina will take a +longer, more circuitous route than it would if the eye<span class="pagenum"><a name="Page_167" id="Page_167"></a>[Pg 167]</span> +were not astigmatic. We cannot, however, immediately +conclude from the fact that an objective movement is +imaged as being greater in extent on the retina, that it +will therefore be more readily perceived by much less +that it will appear greater to, the horse, than would +be the case if the lens were normally constructed. The +visual percept is not immediately dependent upon the +retinal processes, for between the two are interpolated +complex, inaccessible nervous processes. Still, Berlin +believes that he is justified in drawing this conclusion +from a number of relevant considerations. Accepting +it, he believes that it would be possible for the horse to +perceive movements, that for the human eye, which is +not subject to this form of astigmatism, would lie below +the threshold.</p> + +<p>This theory, the simplicity of which certainly must +make a strong appeal, has been adopted by a number of +well-known investigators (Schleich<a name="refanchor40"></a><a href="#ref_40" class="fnanchor">[40]</a>, Königshöfer<a name="refanchor41"></a><a href="#ref_41" class="fnanchor">[41]</a>). +If we also could accept it, then Hans's phenomenal power +of perceiving the movements of objects would be explained. +But doubts arise which restrain us. Even if +we were to accept Berlin's view in general, we should +still come upon the following difficulties. In the first +place, it is questionable whether the peculiar form of +astigmatism mentioned is indeed as common as he supposes.<a name="FNanchor_Z_26" id="FNanchor_Z_26"></a><a href="#Footnote_Z_26" class="fnanchor">[Z]</a> +The references in the literature are exceedingly<span class="pagenum"><a name="Page_168" id="Page_168"></a>[Pg 168]</span> +meager on this point. In order to make a few tests at +least, I undertook to examine nine horses with the aid of +Dr. R. Simon, oculist, to whom I am greatly beholden +for the assistance given in these and other tests to be +mentioned presently. In not one of the nine cases did +we discover anything like the curved deflection which is +supposed to be the sign of the form of astigmatism in +question. But in order to test objectively whether Berlin's +assumption were justified, we examined in the +laboratory fresh specimens taken from two horses. The +eyes were fastened in a frame in what corresponded to +their normal position. Their posterior spherical wall +(i. e., their respective retinal surface) was replaced by a +piece of ground glass. On a spherical surface linear +movements of a point of light are always imaged as +curves, no matter what the shape of the lens forming +the image may be. (For a more detailed statement see +<a href="#closing">page 170, at close of note</a>.) Since, however, our investigation +had to do only with those curves which were +due to the qualities peculiar to the lens, we had to replace +the spherical by a plane projection surface. In front of +the eye thus modified a strong light was placed at such +a distance that the image of it, produced on the improvised +back of the eye by the cornea and the lens, +was a sharply defined point of light. Now, when the +source of light was moved, the point of light would also +move on the glass plate. Sitting at some distance behind +the eye, we observed the movements of this point through +a telescope. Thus we became witnesses of what happens +upon the horse's retina when a moving object passes in<span class="pagenum"><a name="Page_169" id="Page_169"></a>[Pg 169]</span> +front of his eye. Although we saw the point of light +move through relatively long distances both horizontally +and vertically, no sort of deflection in its pathway +could be noted. Berlin's exposition does not hold true +for the eyes of the horses, either living or dead, which +were examined by us.</p> + +<p>But in the case of some of the horses in whom Berlin +had seen the phenomenon for which we sought in vain, +he himself tells us, the deflection was very slight. In +that case, it would appear, no great advantage would +be gained along the lines indicated. But even assuming +the degree of deflection to be very great, his theory goes +to pieces on the very point it was supposed to explain. +A concrete example will make this clear. If Mr. von +Osten, standing two feet away from the horse, raised +his head 1/5 millimeter (which figure by no means represents +the extreme values that were obtained), then in +the horse's retinal image every point of the man's head +would move through a distance of 0.0025 millimeter—assuming +the horse's eye to be free from astigmatism +and assuming its focal distance to be 25.5 millimeters. +If, however, other conditions remaining the same, we +presuppose an extreme form of astigmatism, one in which +the path of the retinal image is not a straight line, but +is deflected into a semicircle, then each point would pass +through a distance of nearly 0.004 millimeter. If the +sensitive retinal elements have a diameter of 0.002 millimeter +(as Berlin, somewhat inexactly, states), then from +two to four elements would be stimulated in case there +were no astigmatic deflection. But in case the deflection +did take place, it would not necessarily involve more +elements, as can be seen by making a simple graph; indeed +we can imagine cases in which the circuitous path<span class="pagenum"><a name="Page_170" id="Page_170"></a>[Pg 170]</span> +would involve even fewer elements than the straight +one. And finally, when the movement which the horse is +to perceive, does not occur in a straight line but in the +form of a curve, (which will generally be the rule), +then the astigmatism will tend in many cases to decrease +the curvature of the image's path on the retina, and +sometimes even obviate it entirely. In all these cases, +on Berlin's own theory, the perception of the movements +would be hindered rather than aided.<a name="FNanchor_AA_27" id="FNanchor_AA_27"></a><a href="#Footnote_AA_27" class="fnanchor">[AA]</a></p> +<span class="pagenum"><a name="Page_171" id="Page_171"></a>[Pg 171]</span> + +<p>But to come now to the most pertinent objection. We +saw that Berlin's whole train of thought rested upon the<span class="pagenum"><a name="Page_172" id="Page_172"></a>[Pg 172]</span> +assertion that it made no difference whether we regarded +by means of the speculum the seeming movement of a +fixed retinal point, or whether the image of an external +moving object is passing over the horse's retina. As a +matter of fact, however, these two processes are very +different from one another. In moving the mirror, with +its small opening we are looking through ever changing +portions of the horse's lens,—testing it out, as it were. +The horse, on the other hand, sees with all parts of the +lens simultaneously, in so far as the lens is not covered +by the iris. The arcuate deflection, which is nothing but +a registration of the difference in the indices of refraction +of the different parts of the lens used consecutively, +might thus be formed for the observer using the mirror, +but never for the horse. For these reasons we cannot +conclude that the kind of astigmatism described can +really increase the horse's acuity in the perception of +movements.</p> + +<p>Since the light-refracting apparatus of the horse's eye +does not offer a satisfactory explanation for the extraordinary +keenness of visual perception possessed by the +Osten horse, we must go a step further and ask whether +it may not perhaps be found in the part immediately +sensitive to light, the retina. That portion really would +seem to be adapted to the perception of movements of +minimal extent, and for this reason: it is more than three +times as great in extent as the human retina, and the +horse's retinal images are likewise larger owing to the +position of the nodal point. The cells of the retina that +are sensitive to light, the rods and cones, might therefore +be correspondingly larger than those of the human eye, +without thereby making the whole organ less efficient +than the human eye. But the most recent measure<span class="pagenum"><a name="Page_173" id="Page_173"></a>[Pg 173]</span>ments<a name="refanchor51"></a><a href="#ref_51" class="fnanchor">[51]</a> +have shown that the rods and cones of the horse's +eye are more minute than ours. Assuming that, in the +case of the horse, as is presumably the case in human +vision, the transition of a stimulus from one retinal cell +to the next already in itself induces a sensation of movement, +then the horse ought indeed be extraordinarily keen +in the perception of moving objects (provided that the +horse's more minute cells are packed just as closely as in +the human retina). And besides, there are two specially +adapted areas within the retina of the horse. The +"band" <a name="tn_png_180"></a><!--TN: Double quote added before "streifenförmige"-->("streifenförmige Area") which was discovered +fifteen years ago by Chievitz,<a name="refanchor52"></a><a href="#ref_52" class="fnanchor">[52]</a> is a strip of 1 to 1½ millimeters +in width, traversing the entire retina horizontally, +and is noteworthy on account of its structure and probably, +too, on account of its greater efficiency. It may +have something to do with the accomplishments of the +Osten horse; but in how far it would be hard to say. +The other noteworthy portion of the horse's retina is the +"round area" discovered some four years ago, located +at the rear outer end of the "band", and it is the best-equipped +part of the horse's retina and corresponds to the +area of clearest vision, the yellow spot, in the human eye. +But this round area need not come in for consideration +by us, for its location would indicate that it is used in +binocular vision, that is, seeing with both eyes.<a name="refanchor53"></a><a href="#ref_53" class="fnanchor">[53]</a> But in +all our experiments the Osten horse observed only with +one eye. That does not mean, however, that under other +circumstances the round area may not be of very great +importance.</p> + +<p>In the present state of our knowledge, all attempts at +explanation are, of course, of the nature of hypotheses. +If further investigations should disclose this explanation +to be untenable, then we would either have to suppose<span class="pagenum"><a name="Page_174" id="Page_174"></a>[Pg 174]</span> +some unknown power in the eye of the horse,<a name="FNanchor_AB_28" id="FNanchor_AB_28"></a><a href="#Footnote_AB_28" class="fnanchor">[AB]</a> or else +seek a cause in the animal's brain. Further experiments +on other horses would be necessary in order to discover +whether the species as a whole possesses this ability or +whether only certain ones are thus endowed. The +former is of course more probable. In this particular +case conditions were unusually favorable for the develop<span class="pagenum"><a name="Page_175" id="Page_175"></a>[Pg 175]</span>ment +of this ability. We must bear in mind that in all +probability Mr. von Osten's movements very gradually +became as minute as they are now, and that therefore +Hans at first learned to react to such as were relatively +coarse. Furthermore, his practice extended throughout +four years and during this time it was his sole occupation. +Without specific predisposition, however, all this practice +would have been utterly futile. We can also readily +appreciate how indispensable in the struggle for existence +a well-developed power of perceiving moving objects +must be to horses (and most other animals) living in +their natural condition and habitat, in order to be aware +of the approach of enemies, or, in the case of carnivora, +the presence of prey. In view of all these considerations +we can readily see how it was possible that the horse, +perhaps in spite of rather defective vision, could react +with precision to movement-stimuli which escaped observation +by human eyes.</p> + +<p>We can understand also the horse's never-flagging +attentiveness when we recall that self-preservation +prompts eternal vigilance over against all that is going +on in the animal's environment. (In the case of Hans, +hunger was at first the motive; later, habit did the work.) +Furthermore, the lower form is not hindered in giving +itself over to its sense-impressions by the play of abstract +thought which tends so strongly to direct inward +our psychic energy,—at least, in the case of the cultured.</p> + +<p>Nevertheless, Hans still remains a phenomenon not +only in excelling all his critics in the power of observation, +but also in that he is the first of his species, in fact +the first animal, in which this extraordinary perceptual +power has been proven experimentally to be present. It +has long been known<a name="refanchor55"></a><a href="#ref_55" class="fnanchor">[55]</a> that horses could be trained to<span class="pagenum"><a name="Page_176" id="Page_176"></a>[Pg 176]</span> +respond to cues in the form of slight movements, which +remained unnoticed by the layman, and this fact has +been made use of by circus trainers to its fullest extent. +But such signs, I have discovered, are without exception, +of a far coarser sort than those we have here described, +and they can be instantly detected by the practised +observer. Nor was it known to professional trainers +that it was possible for the master to direct a horse to +any point of the compass simply by means of the quiet +posture of the body. For this reason it was believed +that no signs could possibly be involved in the color-selecting-tests +(cf. <a href="#SUPPLEMENT_III">Supplement III, page 255</a>). In this +we have the support of some of our experts, as is witnessed +by the following extract from a letter of his Excellency +Count G. Lehndorff, one of our best hippological +authorities, who at one time carefully examined the Osten +horse. (The letter was addressed to Mr. Schillings, and +I have permission of both gentlemen to use it). In it he +says: "If the author's statements, in which you also have +concurred, are correct, and if, as a matter of fact, the +horse really does react to such minute movements as are +absolutely imperceptible to the human observer, then we +have indeed something quite new, for hitherto no one +would have believed that horses can perceive movements +which man cannot. But I am even more surprised by the +explanation of the color-selecting feats.—This too, is +something absolutely new. One would not have deemed +it possible that a horse could do anything of the kind +simply by using the posture of a man's body as a cue to +which it could react with such precision."</p> + +<p>And yet, even though both facts were new concerning +the horse and had not hitherto been proven experimentally +regarding any other species, nevertheless something<span class="pagenum"><a name="Page_177" id="Page_177"></a>[Pg 177]</span> +of this sort has been known concerning the dog for some +time. His ability to single out an object upon which his +master had intently fixed his gaze, was made the basis of +a special form of training, called "eye-training,"<a name="refanchor56"></a><a href="#ref_56" class="fnanchor">[56]</a> nearly +one hundred years ago. The dog was taught to focus +constantly upon his master's eyes and then upon command +to select the object which he, the master, had been +fixating. Such a dog has been described by the naturalists +A. and K. Müller.<a name="refanchor57"></a><a href="#ref_57" class="fnanchor">[57]</a> But the master of the dog, unlike +Mr. von Osten, would not permit anyone else to work +with the animal, and the two brothers, recognizing the +trick, were justified in adding that "the whole affair +aimed at deceiving the public, and the dog's reputation +was but a means of making money". The success of +such exhibitions appeared furthermore, to depend upon +the close proximity of the trainer and the dog, whereas +the direction of the head (and even of the body) could +very probably be perceived at greater distances also. +At least we learn from a reputable source that in the +hunt, dogs can perceive from the mere posture of their +master, what direction he intends to take.<a name="refanchor58"></a><a href="#ref_58" class="fnanchor">[58]</a></p> + +<p>But a still more curious fact is this, that dogs, too, learn—evidently +spontaneously—to react to the minimal involuntary +expressive movements of their master. The +first example mentioned in the literature on the subject +is that of an English bull-dog called Kepler, belonging +to the English astrophysicist, Sir William Huggins.<a name="refanchor59"></a><a href="#ref_59" class="fnanchor">[59]</a> +We are told that this dog seemingly could solve the most +difficult problems, such as extracting square roots and +the like. The numbers were indicated by barking,—thus +one bark was for one, two barks for two, etc. Every +correct solution was rewarded with a piece of cake. +Huggins states explicitly that he gave no signals volun<span class="pagenum"><a name="Page_178" id="Page_178"></a>[Pg 178]</span>tarily, +but that he was convinced that the dog could see +from the questioner's face, when he must cease barking, +for he would never for an instant divert his gaze during +the process. Huggins was unable, however, to discover +the nature of the effective signs. This satisfactory, +though still unproven, explanation has been accepted by +specialists, among them Sir John Lubbock.<a name="refanchor60"></a><a href="#ref_60" class="fnanchor">[60]</a> I, too, +regard this dog as a predecessor of our Hans.</p> + +<p>A similar case is reported by Mr. Hugo Kretschmer, +a writer of Breslau, in the "Schlesische Zeitung" of +August 21, 1904. To him I am beholden for a detailed +written statement, which he has kindly permitted me to +use in this connection. The gentleman named, first +trained his dog to ring the table-bell, and this, by pressing +the dog's paw upon the bell-button. When the dog +had learned to do this independently, his master tried to +teach him the rudiments of numbers, in such a way that +the animal was to give one ring of the bell for the number +1, two for 2, etc. But these attempts failed utterly +and had to be abandoned. But Mr. Kretschmer had +noticed that he was able to get the dog to ring any number +which he, Mr. Kretchmer, might decide upon. +(Success was always rewarded by a bit of bread and +butter.) At first Mr. Kretschmer tried to imagine vividly +only the final number, but failed thereby to elicit correct +responses from the dog. But he did succeed when he tried +making a series of separate volitions. Thus for the number +5, he would "will" each separate push of the button +on the part of the dog. Even so, however, he never got +beyond 9, for then the dog would become impatient and +would ring the bell continuously. Anything that diverted +the dog's attention, such as noises, etc., also entailed +failure. In these tests master and dog had faced each<span class="pagenum"><a name="Page_179" id="Page_179"></a>[Pg 179]</span> +other, each gazing steadfastly at the other. Mr. Kretchmer +was convinced, however, that the dog was not +guided by any sort of sign, but rather by suggestion. +He based his belief on the following two observations. +After some practice, he says, the tests were also successful +when he did not look at the dog, but stood back to +back with it, or when he screened himself from the dog's +view by stepping to one side behind a curtain. The +tests were unsuccessful, on the other hand, whenever he +was mentally fatigued or had taken some alcoholic drink. +The arguments do not appear to me to be adequate. If +he turned his back upon the dog and no other observer +was present, he had no means of knowing whether the +dog did not, after all, peer around to get a peep at him. +If others who knew the desired number, were present, +the dog might have gotten his cues from them. And +there may be some doubt whether the curtain adequately +served the purpose for which it was intended. At any +rate, it was added that all attempts to influence the dog +from an adjoining room—which would thus exclude +effectively all visual signs—were utter failures. I am +also strengthened rather than weakened in my belief, by +the second argument which Mr. Kretschmer makes, viz.: +that mental fatigue or the use of alcohol on the part of +the questioner tends to make the result unsatisfactory. +We noted a similar effect in the case of the horse (<a href="#Page_150">page +150</a>), where a disturbance of the "rapport" between the +questioner and the horse was invoked by some by way of +<a name="tn_png_186"></a><!--TN: "explantion" changed to "explanation"-->explanation. The facts were explained by us much more +simply. We attributed the result to the close correlation +between the type of mental concentration and the nature +of the expressive movements—a correlation which we +have shown experimentally to exist. I cannot, therefore,<span class="pagenum"><a name="Page_180" id="Page_180"></a>[Pg 180]</span> +subscribe to the view that this dog did not require either +visual or other sensory signs. The tests which were +made for the purpose of strengthening that view, are on +a par, I believe, with those mentioned on <a href="#Page_45">page 45</a>. +And since auditory, olfactory, and other stimuli, though +not impossible, still are improbable, I believe that our +Hans, Huggins's dog, and the one belonging to Mr. +Kretschmer, differ from one another only in this, that +the first taps, the second barks, and the third presses a +bell-button.</p> + +<p>And finally I have access to a letter from the Rhine +Province in which there is a brief account of a dog that +would promptly obey any command that was given without +a sound and supposedly without the accompaniment +of the slightest kind of gesture. It is specially mentioned +that the animal steadily watched its master during these +tests. The perception of the slightest involuntary expressive +movements is in all probability the secret in this +case also. Here, too, suggestion has been invoked by +way of explanation, but there was not the slightest attempt +made to find for it a more specific foundation, and +we cannot suppress an objection based on the matter of +principle. It is incumbent upon anyone who uses a term +so ambiguous, to define what content he desires to have +put into it. If he does not do this, he is giving us, instead +of a concept, a bare word, instead of bread, a +stone.</p> + +<p>While we must reject the explanation based on suggestion,<a name="FNanchor_AC_29" id="FNanchor_AC_29"></a><a href="#Footnote_AC_29" class="fnanchor">[AC]</a> +we believe, on the other hand, that we have<span class="pagenum"><a name="Page_181" id="Page_181"></a>[Pg 181]</span> +here again, evidence of the presence of visual signs, +given unwittingly and involuntarily, just as I am sure +that they were involved in the two preceding cases, and +similarly in the case of the Huggins dog. Since the effective +signs were discoverable in none of these canine +predecessors of Hans, an investigation would be desirable, +based upon the insight gained as a result of these +experiments upon Mr. von Osten's horse. Unfortunately +this is impossible, since the dogs in question are dead. +But others like them undoubtedly exist in many places. +We might mention that when Hans first came under the +limelight of public attention, there was also frequent +reference to the Huggins dog, but he soon dropped out<span class="pagenum"><a name="Page_182" id="Page_182"></a>[Pg 182]</span> +of the discussion again.<a name="refanchor63"></a><a href="#ref_63" class="fnanchor">[63]</a> And this for two reasons. +The dog never took his gaze from his master and appeared +to be entirely dependent upon him in his reactions. +Hans, on the other hand, seemed to give evidence +of a high degree of independence and never appeared to +look at the questioner. But we know now that, though +he was never dependent upon the will of his master, he, +too, abjectly hung upon the man's involuntary movements +and never for a moment lost him from view. But since +the horse is able to observe with one eye alone, and +needed to direct only it and not the entire head toward +the questioner, in order to focus comfortably, one could +not conclude as to his line of vision from the direction of +the head. Since, furthermore, in the horse the pupil is +hardly distinguishable from the darkly pigmented iris +and since the white sclerotic is hidden by the eyelids, +except when the eye is turned very much, it is difficult to +determine what direction the eye is taking. I once purposely +stepped backward to the horse's flank, so that he +had to turn his eye far back and thus the outer border +of the iris and the white sclerotic coat became visible +and all doubt concerning the line of vision was removed. +This doubt could never arise in the case of the dog, the +median plane of whose head is always directed toward +the object fixated, and Zborzill is justified in saying, as +he does, in his discussion of training of the kind mentioned +on <a href="#Page_177">page 177</a>, "But any careful observer can immediately +guess the manner in which such a dog has +been trained."<a name="refanchor64"></a><a href="#ref_64" class="fnanchor">[64]</a> If Hans had chanced to possess so-called +"glass-eyes"—in which the dark pigment is +wholly or partly lacking, so that the black pupil is clearly +defined against the lighter background,—then no doubt +could ever have arisen concerning the direction of the<span class="pagenum"><a name="Page_183" id="Page_183"></a>[Pg 183]</span> +eye, and Hans never would have come to be regarded as +the "clever" Hans.</p> + +<p>After the publication of the December report, Hans +acquired a reputation for excellence in thought-reading +and thus the discussion of thought-reading among +animals in general became once more the order of the +day. That is to say that many of our domestic animals +are—like the human mind-reader (à la Cumberland),—supposed +to have the ability to infer the thoughts of +their masters from slight, involuntary movements. They +are thus aware when the feeding hour approaches, when +they may go out in the open, etc. They also appear to +be aware that their welfare lies in our hands, and therefore +would seem to have a vital interest in divining our +intentions and our wishes. Not only our spoken words, +but also numberless movements—usually without our +knowing it and often contrary to our desire—speak a +clear language. As is well said by the American neuropathologist, +Beard,<a name="refanchor65"></a><a href="#ref_65" class="fnanchor">[65]</a> (who first explained the phenomenon +of thought-reading, on the basis of the perception +of very minute muscular jerks, and therefore called it +"muscle-reading" or "body-reading"): "Every horse +that is good for anything is a muscle-reader; he reads +the mind of his driver through the pressure on the bit,—though +not a word of command is uttered." We know +that in the case of perfectly trained horses the rider's +mere thought of the movement which he expects the +horse to make, is seemingly sufficient to cause the animal +to execute it.<a name="FNanchor_AD_30" id="FNanchor_AD_30"></a><a href="#Footnote_AD_30" class="fnanchor">[AD]</a> Such cases are of course very much like<span class="pagenum"><a name="Page_184" id="Page_184"></a>[Pg 184]</span> +that of our Hans, excepting that instead of visual signs +they involve aids of a mechanical nature, which, however, +does not alter the general principle, since both of them are +of the nature of sensory stimulation. But we must not +overlook the essential difference between this so-called +thought-reading on the part of animals and that which is +done by man. The human thought-reader can interpret +movements, for he is familiar with the ideas which are +their source. Thus when at the second tap, I notice a +very slight jerk of the subject's head, and a stronger one +at the fifth tap, I infer that he thought of the problem +2+3=5. While the experimenter thus cannot be said +to read thoughts, he still infers them. The animal, on the +other hand, we may be reasonably sure, draws no such +inferences. In its conscious life it remains ever on the +sensory level. If we could ask Hans about it, he would<span class="pagenum"><a name="Page_185" id="Page_185"></a>[Pg 185]</span> +probably answer: "As soon as my master stoops forward, +I begin to tap; as soon as he moves, I stop. The thing +which induces me to act thus is the carrot which is given +me; what it is that induces my master to make his movements, +I do not know."—It is therefore erroneous to +believe that animals require the power of abstract thinking +in order to utilize the signs which are consciously +or unconsciously given them, as is argued by Goldbeck<a name="refanchor68"></a><a href="#ref_68" class="fnanchor">[68]</a> +when he says with reference to the training for visual +signs, which we have already mentioned before: +"There the dog has consciously interpreted the visual +impression in terms of the conclusion that he is expected +to bring forth the leaf indicated." Nor was there any +justification for the critic who thought he could put the +essence of the report of December, given in <a href="#SUPPLEMENT_IV">Supplement +IV</a>, into the following words: "He (Hans) showed that +he has the power of attention, can draw logical conclusions, +and can communicate the result of his thinking,—and +all this independently." Yet none of this had been +asserted. The whole thing may be explained satisfactorily +by means of a process of simple association established +between the signs observed in the master and certain reactions +on the part of the horse. The fact that the movements +made were so exquisitely minute does not change +the matter in the least. Such signs call for a high degree +of sensory keenness and great concentration of attention, +but by no means an "extremely high intelligence."</p> + +<p>Let us turn now from the consideration of visual perception +to that of auditory perception in the horse. We +saw that the fact that Hans was able to respond to commands +which were only inwardly enunciated, that is, +commands which were merely thought of but not spoken, +was not proof of great acuity of hearing, but rather that<span class="pagenum"><a name="Page_186" id="Page_186"></a>[Pg 186]</span> +hearing was not at all involved. If Hans had been deaf +he would, none the less, have promptly obeyed the commands. +Blind and near-sighted horses try to overcome +their deficiency by means of the sense of hearing, and +hence show a pronounced play of ears. In the case of +the Osten horse, however, attention has been diverted from +auditory stimuli in the process of habituation to visual +signs, and as a result ear-movements are almost completely +wanting. One is not of course permitted to deny +<i>a priori</i> that perhaps some associations might have +been formed between objects and the vocal signs belonging +to them, e. g., between the colored cloths and the +names of the colors if both had been presented together +oftener than was the case.</p> + +<p>But there is a dearth of reliable observation as to how +far auditory associations of this sort may be established +in horses. Usually the following is cited. Horses learn +to start off, to stop, and to turn about in response to calls. +They are able to distinguish properly between the expressions +"right" and "left", or equivalent terms. +Upon command they will start to walk, to trot or to run. +And they also know the name by which they are usually +called. All authors agree that cavalry horses understand +the common military commands; one writer even avers +that they excel the recruits in this respect.<a name="refanchor69"></a><a href="#ref_69" class="fnanchor">[69]</a> Some believe +that in riding schools the horses pay closer heed to +the calls of the riding-master than to the control of unpractised +riders, even when the two are at variance with +one another.<a name="refanchor70"></a><a href="#ref_70" class="fnanchor">[70]</a> My experience with the Osten horse and +a number of other pertinent observations aroused in +me the suspicion that much that is called or spoken in +the process of managing a horse may possibly be just so +much labor lost. In consequence I made a series of<span class="pagenum"><a name="Page_187" id="Page_187"></a>[Pg 187]</span> +relevant experiments. I have thus far tested twenty-five +horses of different kinds, from the imported Arabian +and English full-blood, down to the heavy draft-horse. +The experiments were made partly in the courtyard of +military barracks, partly in the circus, and partly in a +riding-school or in private stalls. I am specially indebted +for kind assistance to Messrs. von Lucanus, Busch, and +to H. H. Burkhardt-Foottit and E. Schumann, the two +excellent trainers connected with the Busch Circus. +During these tests, the horses were always amid circumstances +familiar to them, whether free or bridled, under +a rider or hitched to a wagon. All aids or signals, except +the calls, were eliminated in so far as it was possible.</p> + +<p>The results of those tests were in substance as follows: +Many horses react to a smack of the lips by a rather fast +trot. Many stop on the cry "Hola" or "Brr". This +last was nicely illustrated in the case of two carriage +horses supplied with large blinders and held with a loose +rein, and hitched to a landau. One of them regularly +stopped when the "brr" was given by the driver, +whereas the other, which had not been habituated to this +signal, kept serenely on the trot, so that the vehicle +regularly veered off the track—a sure sign that no unintentional +aid was being given by means of the reins. +Other horses, again, were accustomed to halt in response +to a long-drawn-out "hola", but it was the cadence of +melody rather than the word that was effective, since +any other word, or even a series of inarticulate sounds, +would produce the same result, provided they were given +with the proper inflection. When this was changed, then +the response would fail.</p> + +<p>The result was not so apparent when it came to controlling +the kinds of gait. One riding-school horse, when<span class="pagenum"><a name="Page_188" id="Page_188"></a>[Pg 188]</span> +lunged and in a gallop, could be induced by a friendly +call—the word again was a matter of inconsequence—to +slacken his pace into a trot and from a trot into a walk. +But this reaction was by no means very precise. <a name="tn_png_195"></a><!--TN: Comma added after "Another"-->Another, +a full-blood, contrary to the trainer's expectation and to +his great astonishment, failed to respond to any kind of +spoken command as soon as the one who carried the +reins refrained from making any movements which might +indicate what was wanted. (To refrain from all expressive +movements of this kind is by no means an easy +matter). The slightest move, apart from any help by +means of the reins or the whip-handle, was sufficient to +evoke a response. The results in the case of the military +horses, differed in many particulars. Thanks to the +courtesy of Captain von Lucanus I had the opportunity +of testing three cavalry horses, two geldings and one +mare, aged nine, thirteen, and nineteen years respectively, +and all of them in the regiment ever since their fourth +year. They had been selected as the "most intelligent" +in the squadron, and we were assured that they would +obey punctiliously all the usual commands. They were +ranged behind one another, with the customary distance +of two horses' lengths between, and were ridden each by +his accustomed rider. Both starting and stopping upon +command were tested. The horses were held by the +reins, but the riders were cautioned to refrain from giving +any aid that might cause the horse to start when starting +was to be tested, or that might restrain him when stopping +in response to the spoken command was to be tested. +If a suspicion arose—a thing which happened only twice, +however—that a rider had actively aided in his horse's +reaction, then an officer would mount into the saddle. +If it appeared that one of the horses was simply imitat<span class="pagenum"><a name="Page_189" id="Page_189"></a>[Pg 189]</span>ing +the others, then the others were purposely restrained +by their respective riders. The commands were given +by the corporal who usually had charge of the horses. In +a few cases the sergeant of the squadron gave the commands, +but this made no difference in the success of the +experiment. Now as to the results. Whenever the +horses were trotting or walking, all commands, without +exception, were in vain. They effected neither an increase +nor a decrease in the pace. A result was obtained +only when the horses were standing when the test began; +and this result was simple enough,—upon certain calls +the animals would respond by beginning to walk. This +was the only reaction that was obtained. The most effective +of the commands appeared to be "Squadron,—march!" +But the command "Squadron!" or +"March!" alone, were quite as effective; yet none of +these commands was obeyed without exception. Reactions +were occasionally obtained in response to "trot!", +"gallop!" "retreat!", (the usual introductory "squadron" +was purposely omitted here, because it alone sufficed +to start the horses). But the reactions were always +the same, viz., to start on a walk. Another series of +commands (such as those which are addressed to the +rider alone, e. g., "Lances down!") had no effect whatever; +a certain amount of selection therefore did seem +to take place. In all these tests the order of the horses +with reference to each other's position was repeatedly +changed. One of the horses, the youngest, and reputed +to be the most "intelligent", (he was as a matter of fact +the most spirited), gave evidence of a gregarious instinct, +intensified by habit, which, if it had been overlooked, +might have become a source of serious error. Not being +accustomed to go at the head, when so placed it started<span class="pagenum"><a name="Page_190" id="Page_190"></a>[Pg 190]</span> +properly in only 18% of all such cases. When, however, +(other conditions remaining the same,) he was put in +second or third place, he started properly in 67% of the +tests, and if we take into account only those cases in +which the three most effective commands were used +("Squadron!", "March!", and "Squadron—march!") +he reacted correctly in 91% of the cases. (The number +of tests was 17, 36 and 22 respectively for the three +groups mentioned.) The horse, therefore, almost always +began to step properly when he stood behind one of his +companions, but seldom when he stood at the head. And +when he stood at the head and began to walk at the +proper moment, it was plain that it was a case of imitation +and not initiative, for the horse was still able to see +the others, owing to the extent of his field of vision backward, +and he was always the last to move, whereas otherwise +he was always the first to move, and always difficult +to restrain. So when the horses to the rear were restrained +or when the intervening distance of two horses' +lengths was lessened, so that this gelding could not see +the one in the rear, he failed completely to respond. Accordingly +these three horses did little to justify the faith +which their squadron had placed in them.</p> + +<p>Now a few words on the manner in which horses react +upon the call of their names. We are not concerned +with those that are seldom or never called by name +(such as those in the cavalry). I have not discovered +one horse that constantly and unequivocally reacted upon +the mention of its name (though I would not assert that +there are none that would do so.) I was nearly always +able to convince the owners or grooms, who at first had +maintained a contrary opinion, that any inarticulate sound +was capable of producing the same effect as the calling<span class="pagenum"><a name="Page_191" id="Page_191"></a>[Pg 191]</span> +of the name. What the significance of inflection may be, +I am not at all certain. When a certain one of a number +of horses standing in the same stable was called, all of +them responded by pricking their ears, raising their +heads, or else turning about. For this reason the reaction +of the horse specifically called lost all significance. +Likewise the call which is ordinarily used in lunging +when the man in the center of the circle wishes the horse +to change its gait, or to advance toward him, also proved +ineffectual as soon as the man inhibited every sort of +movement. A slight nod, on the other hand, was always +effective. Several times I have tried to call horses to me, +when they were free and running about in the arena, but +was unsuccessful. After I had given them some sugar, +however, they would always come to me—whether I had +called or not—and would then refuse to leave my side. +But this is a matter of common observation.</p> + +<p>I would, however, regard all of these tests as merely +provisional. In spite of the greatest effort, it was not +always possible to control all the conditions of the experiment, +and furthermore, the number of tests would +have to be materially increased in order to yield an +appreciation of the difference due to race, age, and the +individual variation and training of horses. But we +may, even now, be sure of one thing. Over against the +certainty with which horses react to visual stimuli (in +the form of movements perceived), it does not appear +that the formation of auditory associations is greatly +favored by nature in these animals,—indeed, auditory +associations are far less common than is generally supposed.<a name="FNanchor_AE_31" id="FNanchor_AE_31"></a><a href="#Footnote_AE_31" class="fnanchor">[AE]</a> +Horses compare very unfavorably with dogs in<span class="pagenum"><a name="Page_192" id="Page_192"></a>[Pg 192]</span> +this respect. The latter easily learn to react with a high +degree of precision to auditory signs,—as I learned from +a series of experiments which I was enabled to perform. +The Osten horse, therefore, does not stand alone among +his kind in his inferior auditory equipment, as one might +be tempted to believe at first blush.</p><span class="pagenum"><a name="Page_193" id="Page_193"></a>[Pg 193]</span> + +<p>It is easy to explain the musical accomplishments. The +tones which were played for the horse, were known to +Mr. von Osten, since he himself played the harmonica, +or when someone else played it, he, Mr. von Osten, +could see the stoppers. He then thought of the number<span class="pagenum"><a name="Page_194" id="Page_194"></a>[Pg 194]</span> +which indicated the tone in question, and Hans would +tap it. Thus arose the tale of the horse's absolute tonal +memory. This tale gained much support at the time, +from an experience which has been recounted to me by +the well-known composer, Professor Max Schillings. +It shows more clearly than any other report how very +confused were the threads that had been spun in the whole +matter. In order to test the horse's musical ability Prof. +Schillings played, let us say, three tones upon the accustomed +instrument. Complying with Mr. von Osten's +wish, Prof. Schillings always indicated which three he +was about to play. The horse always tapped them correctly. +In order to make a decisive test, Prof. Schillings +then played, without anyone's knowledge, a note that was +in reality a third below the one he had indicated to Mr. +von Osten. Curiously enough, Hans tapped, as a matter +of fact, the number indicating the note that was actually +struck, and it was only in the third repetition and after +many exhortations on the part of the master "to have +a care", that the horse finally tapped the number indicating +the note Mr. von Osten had in mind and which +in truth was the wrong one. This curious experiment +seemed to those to whom Professor Schillings communicated +it, to yield conclusive evidence of the horse's +absolute hearing. As a matter of fact, however, Prof. +Schillings had unwittingly, and, contrary to any intention +on his part, inspired the horse. Standing, as he did, +just behind the right shoulder of the horse, he was able +to interrupt Hans (who had begun to tap in response to +a move on the part of Mr. von Osten,) by means of an +involuntary movement which did the work of a closing +signal. At the same time Mr. von Osten, likewise standing +to the right of the horse and expecting more taps,<span class="pagenum"><a name="Page_195" id="Page_195"></a>[Pg 195]</span> +remained perfectly quiet. (This is as it was in the tests, +mentioned on <a href="#Page_71">page 71</a>, in which, of two experimenters, +one started the horse tapping, and the other stopped +him.) Mr. von Osten very probably lost patience after +Hans had seemingly given the wrong response twice, +and thereupon came nearer to the horse and thus by +monopolizing its attention—so as to exclude Prof. Schillings—he +was able to get the response so ardently +desired.<a name="FNanchor_AF_32" id="FNanchor_AF_32"></a><a href="#Footnote_AF_32" class="fnanchor">[AF]</a> When, in tests such as these, two stoppers<span class="pagenum"><a name="Page_196" id="Page_196"></a>[Pg 196]</span> +were opened and thus two notes sounded, Mr. von Osten +would count the number of stoppers intervening between +the two, and Hans would tap the number. And so arose +the tale of Hans's knowledge of musical intervals. +Whenever the two notes were sung or whistled, in which +case there would be no stoppers that could be counted, +then Mr. von Osten, who was quite destitute of musical +knowledge, was at a loss, and also Hans. If, however, +the intervening notes were sung, then everything went +smoothly once more. Major and minor chords were +regularly characterized as "beautiful", all others as +"bad", (but even here errors occurred). A musician +had taught Mr. von Osten these distinctions. The old +man also knew the melodies that were played on the +hand-organ. Each one had a number assigned to it, and +Hans was required to tap the number of the melody in +token of recognition.—Hans was as ignorant of musical +time, as he was of melody, and all attempts to get him to +march in regular step were utterly futile. A number of +musical tests were made in the absence of Mr. von Osten. +In these Mr. Hahn undertook the questioner's rôle, and<span class="pagenum"><a name="Page_197" id="Page_197"></a>[Pg 197]</span> +since he had had musical training, he was aware of what +the numbers should be, even when he could not see the +stoppers of the harmonica, and, therefore, we readily understand +why it was that the horse responded so wonderfully +in his case.</p> + +<p>The so-called musical ability of horses appears, from +all that is known, to be confined within very narrow +bounds. Only one fact is universally accepted, viz., +horses of the military are believed to possess a knowledge +of the significance of trumpet signals, and are often +said to interpret them more readily than the recruits.<a name="refanchor81"></a><a href="#ref_81" class="fnanchor">[81]</a> +Since no experiments had been made along these lines, I +undertook to make a brief test of the cavalry horses mentioned +on <a href="#Page_188">page 188</a>. As in the preceding tests, the three +animals were arranged behind one another with the customary +distance of two horses' lengths between, and each +was ridden by his accustomed rider. They were held by +the reins, but received no aid of any kind, either to start +them or to restrain them. A bugle then sounded the various +signals at the other end of the barrack's courtyard. +We had been previously assured that the horses would +certainly react without fail. But, as a matter of fact, the +result was quite the contrary. Two of the horses did not +move at all, and the third, a thirteen-year old gelding, was +startled nearly every time and would tear off in a gallop—even +though a trot had been sounded. I would not, +however, venture to draw any conclusions from results +such as these. Many more tests would have to be made, +and some of them upon the whole squadron, before a +judgment could be given.<a name="FNanchor_AG_33" id="FNanchor_AG_33"></a><a href="#Footnote_AG_33" class="fnanchor">[AG]</a></p><span class="pagenum"><a name="Page_198" id="Page_198"></a>[Pg 198]</span> + +<p>I shall now turn to peculiarities of character, highly +humanized, which have been attributed to Hans. His +"sympathies" and "antipathies", so-called, were nothing +but erroneous appellations for the success or failure +on the part of the respective individuals to elicit responses. +He who could procure answers frequently, apparently +stood high in the horse's favor. That Hans shook his +head violently when asked by Mr. von Osten: "Do you +like Mr. Stumpf?", and answered in the affirmative the +further question: "Do you like Mr. Busch?", was nothing +but a confession—unwilling, to be sure—on the part +of the master himself. In the first case the master +thought "no", in the second instance, "yes", and the<span class="pagenum"><a name="Page_199" id="Page_199"></a>[Pg 199]</span> +two thoughts were accompanied by the corresponding +head movements, to which Hans responded mechanically. +Hans appeared to be well-disposed toward me, but evidently +because I always rewarded him liberally when he +answered correctly, and I did not scold him when his +responses were wrong, as did Mr. von Osten and Mr. +Schillings, who instead of seeking the cause within themselves, +were always ready to rebuke Hans for his contrariety +and fickleness. The horse did not show, in so +far as can be judged at all, any real affection for his +master. On the other hand it would be unwarranted to +say that, in spite of all rewards, he developed a grudge +against all those who bothered him with instruction and +examination. Shortly after the close of our experimenta<span class="pagenum"><a name="Page_200" id="Page_200"></a>[Pg 200]</span>tion +it happened that Hans severely injured his groom by +a blow in the face. Yet this man had always been very +gentle with the horse and had been forbidden by Mr. von +Osten to make Hans solve any problems for him. Experts +assure me that we have here to deal, not with a +case of "moral insanity", but with a very common experience,—although +this view will probably be cavilled +at by enthusiastic lovers of horses. The work of so +excellent an expert as Fillis,<a name="refanchor92"></a><a href="#ref_92" class="fnanchor">[92]</a> for instance, bears us out +in this respect.</p> + +<p>The horse's supposed fickleness was nothing but a +token of the fact that even those who were accustomed to +working with him, did not have him completely in hand. +(They simply did not understand how to obtain correct +responses from the horse.) It often happened that in the +evening, when it had become so dark that the movements +of Mr. von Osten could no longer be seen, Hans had to +suffer bitter reproaches because he made so many errors. +That, in truth, he never was stubborn and that the cause +of failure really lay in the questioner, is shown by the +fact that the mood, for which he was reproved, would disappear +the moment the questioner voluntarily controlled +the signals. We may add that there was no basis for the +assumption that "he had an uncommon, finely constituted +nervous system" or was possessed of a "high degree of +nervousness". Both these phrases were often mentioned +by way of explanation. Hans was restive, as horses usually +are. And besides, he lived a life so secluded (he +was never allowed to leave the courtyard) that as a result +he was easily disturbed by strange sights and sounds. +There was not the slightest trace of the clinical symptoms +of neurasthenia—on the contrary he gave the impression<span class="pagenum"><a name="Page_201" id="Page_201"></a>[Pg 201]</span> +of perfect health,—which was curious enough when we +remember his rather unnatural mode of life.</p> + +<p>Hans's stubbornness was a myth. He was suspected of +it whenever the same error occurred a number of times +in succession, i. e., when the questioner did not properly +regulate his attention (<a href="#Page_146">page 146</a>) or when he was being +controlled by "perseverative tendency", mentioned on +<a href="#Page_149">page 149</a>. Mr. Schillings, who has provided me with +material here as elsewhere, relates the following episode +which occurred on one such occasion. To one and the +same question put alternately by Mr. von Osten and Mr. +Schillings, Hans responded correctly, with two taps, to +the former, and just as persistently incorrectly, with three +taps, to the latter. After Mr. Schillings had suffered this +to occur three times he accosted the horse peremptorily: +"And now are you going to answer correctly?". Hereupon +Hans promptly shook his head, to the great merriment +of all those present. (Mr. Schillings had, with no +accounted reason, expected a "no".) Hans was called +willful whenever the same question was successively answered +by different responses, as frequently happened +with the increasing tension that characterized the high +numbers (<a href="#Page_145">page 145</a>). He was also regarded as stubborn +when no reply at all was forthcoming, as in the tests with +the blinders.</p> + +<p>Hans's supposed distrust of the questioner, when the +latter did not know the answer to the problem, is nothing +but a poor attempt to account for the failure of those +tests. Hans's distrust of the correctness of his own responses +was supposed to be evident from his tendency to +begin to tap once more if, after the completion of a task, +the questioner did not immediately give expression to<span class="pagenum"><a name="Page_202" id="Page_202"></a>[Pg 202]</span> +some form of approval or disapproval—just as a schoolboy +begins to doubt his answer if the teacher remains +silent for a short time. In terms of the results of our +experimentation this would mean that whenever the questioner +did not resume the erect posture, after Hans had +given the final tap with the left foot, then the horse would +immediately begin once more to tap with the other foot +(<a href="#Page_61">page 61</a>).</p> + +<p>As the evil characteristics, so, too, the good. Thus, his +precipitancy, which was supposedly evidenced by his beginning +to tap before the questioner had enunciated the +question, was nothing but a reflection of the questioner's +own precipitancy in bending forward (<a href="#Page_57">page 57</a>). Never +did Hans evince the slightest trace of spontaneity. He +never spelled, of his own accord, anything like "Hans is +hungry," for instance. He was rather like a machine +that must be started and kept going by a certain amount +of fuel (in the form of bread and carrots). The desire +for food did not have to be operative in every case. The +tapping might ensue mechanically as a matter of habit—for +horses are to a large extent creatures of habit. This +lack of spontaneity could hardly be reconciled with the +horse's reputation for cleverness. It would not be necessary +to touch upon the signs that were supposed to betoken +genius: the intelligent eye, the high forehead, the +carriage of the head, which clearly showed that "a real +thought process was going on inside",—all these, we +said, would not need mentioning, if they had not been +taken seriously by sober-minded folk. If there is a report +that Hans turned appreciatively toward visitors who +made some remark in praise of his accomplishments,—it +is evidence only of the observer's imaginativeness.</p> + +<p>Turning from a consideration of the horse to that of<span class="pagenum"><a name="Page_203" id="Page_203"></a>[Pg 203]</span> +the persons experimenting with him,<a name="FNanchor_AH_34" id="FNanchor_AH_34"></a><a href="#Footnote_AH_34" class="fnanchor">[AH]</a> the first and most +important question that arises is this: How was it possible +that so many persons (there were about forty) were<span class="pagenum"><a name="Page_204" id="Page_204"></a>[Pg 204]</span> +able to receive responses from the horse, and many of +them on the very first occasion? The answer is not hard +to find. All of these persons came to the horse in very +much the same frame of mind—which found a similar +expression in all, in both posture and movements. And +it was these motor expressions of the questioner (aside +from the signs for "yes" and "no", which I believe I +have adequately explained on <a href="#Page_98">page 98</a>), that the horse +needed as stimuli for his activity.</p> + +<p>The next question that arises is: why did only a few +persons receive responses regularly from Hans, whereas +the greater number were favored only occasionally? +What was the selective principle involved? The answer +is, that the successful person had to belong to a certain +type, which embodied the following essential characteristics.</p> + +<p>1. A certain measure of ability and tact in dealing with +the horse. As in the case of dealing with wild animals, +such as the lion, etc., Hans must not be made uneasy by +timidity in the questioner, but must be approached with +an air of quiet authority.</p> + +<p>2. The power of intense concentration, whether in expectation +of a certain sensory impression (the final tap), +or in fixing attention upon some idea-content ("yes", +"no", etc.). It is only when expectancy and volition are +very forceful, that a sufficient release of tension can ensue. +This release of tension is accompanied by a change +in innervation and results in a perceptible movement. +And it was only when the thought of "yes", or "up", +etc., was very vivid, that the nervous energy would spread +to the motor areas and thence to the efferent fibers, and +thus result in the head-movement of the questioner.<span class="pagenum"><a name="Page_205" id="Page_205"></a>[Pg 205]</span> +From infancy we are trained to keep all of our voluntary +muscles under a certain measure of control. During +the state of concentration just described, this control is +relaxed, and our whole musculature becomes the instrument +for the play of non-voluntary impulses. The +stronger the customary control, the stronger must the +stimuli be which can overcome it. The steady unremitting +fixation, which resulted in the horse's selection of +the cloths, also involves a high degree of concentration.</p> + +<p>3. Facility of motor discharge. Great concentration +was necessary of course, but not sufficient. Persons in +whom the flow of nervous energy tended to drain off +over the nerves leading to the glands and the vascular +system might betray great tension, not so much by movements +as by a flow of perspiration (we have many excellent +examples of this given by Manouvrier)<a name="refanchor93"></a><a href="#ref_93" class="fnanchor">[93]</a> or by a +violent beating of the heart, blushing and the like,—in +short, by secretory and vasomotor effects. Or it is not +inconceivable that long dealing with very abstract +thoughts might have weakened the tendency of overflow +to other parts of the brain, and that therefore the entire +discharge is used up in those portions of the brain which +are the basis of the intellectual processes. But if expressive +movements occur, the motor pathways must be particularly +unresisting in order to take up the overflow of +psychophysic energy. This is the necessary condition +for obtaining the tapping and the head movements on the +part of the horse, although for the tapping there is still +one other circumstance necessary: viz.,</p> + +<p>4. The power to distribute tension economically—i. e., +the ability to sustain it long enough, and to release it at +the right moment (after the manner of the curves de<span class="pagenum"><a name="Page_206" id="Page_206"></a>[Pg 206]</span>scribed +on <a href="#Page_93">page 93</a>), and to control properly the unavoidable +variations which will occur.<a name="FNanchor_AI_35" id="FNanchor_AI_35"></a><a href="#Footnote_AI_35" class="fnanchor">[AI]</a></p> +<span class="pagenum"><a name="Page_207" id="Page_207"></a>[Pg 207]</span> + +<p>The experience of a number of practical men, who +have had much to do with horses and yet achieved but<span class="pagenum"><a name="Page_208" id="Page_208"></a>[Pg 208]</span> +very modest success with Hans, goes to show that it is +not always the lack of sufficient authoritativeness, mentioned +under heading 1 that is the sole cause of failure, +as has been claimed so often. That the horse was, to a +certain degree, influenced by this element of authority is +shown, however, by the following incident. A certain +gentleman, when alone in the courtyard with Hans, received +responses only so long as I (concealed in the barn) +kept the barn-door open just a little, so that my presence +could be known to the horse. As soon as I closed the +door, Hans refused to respond to the gentleman. Those +who possessed sufficient power of concentration and the +requisite motor tendency—the two characteristics mentioned +under 1 and 2 above,—were able to obtain responses +from the horse without any previous practice. +Practice merely effected a more economic distribution of +attention, so that the larger numbers especially were +more successful as a result (pages <a href="#Page_68">68</a> and <a href="#Page_89">89</a>). Those +who were lacking in either of the characteristics mentioned +under 2 and 3 would not be aided even by the +greatest amount of practice, as is shown by the case men<span class="pagenum"><a name="Page_209" id="Page_209"></a>[Pg 209]</span>tioned +in <a href="#SUPPLEMENT_III">Supplement III (page 255)</a>.—That many individuals +were at first successful but were later unable +to get any successful responses, is to be accounted for by +the fact that the power of concentration, at first present, +later rapidly disappeared. This temporary increase in +the power of doing mental work was first investigated +experimentally by Rivers and Kraepelin,<a name="refanchor95"></a><a href="#ref_95" class="fnanchor">[95]</a> and was called +by them "Antrieb" and aptly likened to the first pull of +a team of horses in starting off. This, too, explains an +experience which befell a number of the horse's visitors, +who later described it to me. Wishing to utilize a momentary +absence of Mr. von Osten, they excitedly put a +hasty question to Hans, and with amazing regularity +received correct responses.—Besides Mr. von Osten, Mr. +Schillings and myself, not many were always able to induce +Hans to bring the colored cloths or to execute the +head movements. It was easy, on the other hand, to get +him to nod. Therefore there was some truth in Mr. von +<a name="tn_png_216"></a><!--TN: "Ostens'" changed to "Osten's"-->Osten's assertion, that Hans would be unable to answer +a difficult question if he had not previously indicated by +means of a nod that he had grasped its import. Those +who were not concentrating sufficiently, would not look +into Hans's face, when he was expected to nod, and +would not bend over, when Hans ought to begin tapping—such +persons could not, therefore, since they did not induce +Hans to nod, elicit the tapping. I, myself saw the +"no" successfully elicited only in the case of Mr. von +Osten, Mr. Schillings and Mr. Hahn; the "right" and +"left" only in the case of the former two. It must remain +uncertain whether this failure on the part of otherwise +suitable persons to elicit the responses for "right" +and "left" was due to their accompanying these ideas by +movements of the eyes instead of by movements of the<span class="pagenum"><a name="Page_210" id="Page_210"></a>[Pg 210]</span> +head, (<a href="#Page_106">page 106</a>). For unfortunately it was not possible +to make special tests to discover whether Hans reacted to +isolated eye movements. There is, however, more than +one reason why I would doubt this. Taken all in all, +there were but few persons who were entirely representative +of the type described (c. f. <a href="#Page_31">page 31</a>)—they were +those who are commonly characterized as being of a lively +temperament and strongly impulsive. Thus Hans +acquired a reputation for "Einkennigkeit", that is, he +would accustom himself only to certain persons. Such +a reputation was hard to reconcile with his much praised +intelligence.</p> + +<p>In closing, just a word on the influence of the public +that was present. As was shown on <a href="#Page_69">page 69</a>, the public +in general did not influence the horse in his reactions. +The effect upon the questioner, however, was unmistakable, +and worked in a twofold manner. On the one hand +the questioner's zeal was increased and with it the tension +of concentration. On the other hand, it introduced +an element of diversion, and attention was divided between +the horse and the spectators, and thus concentration +suffered. If the disturbing effect was slight, as in +the case of Mr. von Osten, then the favorable influence +exercised by the presence of the public outweighed the +unfavorable. Mr. von Osten was, for that reason, often +particularly successful when working in the presence of +a large body of spectators. This was noted by many and +was ascribed to the ambition of the horse. When, however, +a person was easily diverted, as was Mr. Schillings, +then the presence of the public had a less fortunate effect.</p> + +<p>This, then, completes my explanation of the facts +gleaned from observation and experimentation. It accomplishes +all, I hope, that may be expected of an ex<span class="pagenum"><a name="Page_211" id="Page_211"></a>[Pg 211]</span>planation. +All the known achievements of the horse, all +the successes and failures of the questioner, have been reduced +to a single principle; no secondary hypothesis has +been invoked, and but slight place has been given to the +element of chance. Nevertheless, it may not be out of +place to forestall two objections which might possibly be +raised. First, some may assert that it was through our +experimentation that the horse became mechanized and +incapacitated as regards conceptual thinking; that formerly +he really could solve arithmetical problems, and only +later developed the very bad habit of depending upon the +signs which I gave him. This objection is to be refuted +in that I did not originate these signs, but first noted them +in Mr. von Osten, himself, and in that Hans still works +as faithfully as ever for Mr. von Osten. I have learned +from many trustworthy witnesses that the horse still continues +to give brilliant exhibitions of his "ability". If, +on the other hand, anyone should assert that it was only +with us that Hans reacted to movements, but that with +his master he really thought and still thinks, then I must +ask for proof. This latter argument is by no means very +original. When Faraday in 1853 proved experimentally +that "table-rapping" is the result of involuntary movements +on the part of the participants standing about the +table, the spiritualists asserted that his experiments had +nothing in common with their own proceedings, because +his subjects (who by the way, had been up to that time +firm believers in table-rapping) probably did move the +table, they said, while they (the spiritualists) do no such +thing.<a name="refanchor96"></a><a href="#ref_96" class="fnanchor">[96]</a></p> +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_T_20" id="Footnote_T_20"></a><a href="#FNanchor_T_20"><span class="label">[T]</span></a> Professor Shaler<a name="refanchor24"></a><a href="#ref_24" class="fnanchor">[24]</a>, a well-known American savant, mentions a +three-year old pig belonging to a Virginian farmer, that was able to read +and had some understanding of language. From numerals which were +written upon cards and spread out before it, this pig could compose +dates. It could also select from among certain cards one upon which +was written a given name, asked for by the master. Supposedly no +signs of any kind were given. (Shaler thought to exclude effectively the +sense of smell, which is so highly developed in the pig, in that he, Shaler, +himself smelled at the cards, since he also "possessed an acute olfactory +sense!") Since we are told that the farmer in question made a business +of supplying trained pigs for exhibition purposes, the case appears suspicious. +We hear of a pig exhibited in London, that was able to read +and spell, and could also tell the time by the watch<a name="refanchor25"></a><a href="#ref_25" class="fnanchor">[25]</a>. We cannot +tell, however, whether the two pigs, which beyond a doubt were mechanically +trained to respond to signals, are identical or not.</p></div> + +<div class="footnote"><p><a name="Footnote_U_21" id="Footnote_U_21"></a><a href="#FNanchor_U_21"><span class="label">[U]</span></a> It has been scientifically proven that a number of supposed mystical +phenomena, table-moving, table-rapping, and divination by means +of the rod, all are the result of involuntary movements made unawares +by those concerned, just as in the case of this work with Hans. (We +must of course except those not infrequent instances in which the phenomena +in question are purposely and fraudulently simulated.) There +is this difference, however, that there the thing affected is a lifeless object,—the +table or the rod,—here it is a living organism, the horse; hence +there the immediate effect of the movement is physical work in the form +of energy expended in moving the table, here the movement becomes a +visual stimulus. A number of observations which I find in the relevant +literature, and which I shall introduce into this chapter, may serve to +show how close is the similarity between the two cases, how much +depends upon the questioner, and how little really upon the instrument—whether +table or horse—which is acted upon. +</p><p> +Two examples will suffice to illustrate the significance of belief and +of the concentrated attention that results from it. The first is taken +from the letters of Father P. Lebrun on the divining rod<a name="refanchor26"></a><a href="#ref_26" class="fnanchor">[26]</a>, which appeared +in 1696. An old woman once told a treasure-seeker that she had +always heard that a treasure was buried at a certain place in the fields. +The man, who was known as an expert in the art of using the divining +rod, immediately set out to locate the gold. Lo, and behold, the moment +he set foot on the spot described by the old woman, the branch turns +downward, and from its movements the man gathers that twelve feet +below ground there lies buried some copper, silver and gold. He calls +a peasant to dig a pit eleven feet deep, then he sends him away so that +no other should get into the secret. He himself digs a foot deeper, but +all in vain, for he finds nothing. Standing in the pit, he again takes up +the branch. Again it moves, but this time it points upward, as if to +indicate that the treasure had disappeared from the earth. Dismayed, +he climbs out of the pit and questions the branch a third time. This +time it points downward once more. He climbs back into the pit. +Presently he feels the prick of conscience (for in the 17th century many +regarded the dipping of the divining rod as the work of the Devil). +Terrified, he exclaims: "O God, if the thing I am doing here is wrong, +then I renounce the Evil One and his rod (s'il y a du mal, je renonce au +démon et à la <a name="tn_png_219"></a><!--TN: "baguette")" changed to "baguette)""-->baguette)". Having spoken, he once more takes the rod +in hand to test it. It does not move. Horrified, for now there was no +longer any doubt that Satan was the cause of its movements, the man +makes the sign of the cross and runs away. But he had hardly gone +more than two or three hundred paces when the thought strikes him: +Is it really true that the branch will no longer move for him? He +throws a coin to the ground, cuts a branch from a bush nearby, and is +overjoyed when he notes how it dips down toward the money. +</p><p> +Another example is to be found in a report of the well-known physicist, +Ritter<a name="refanchor27"></a><a href="#ref_27" class="fnanchor">[27]</a>, of Munich, which appeared during the early part of +the 19th century. Ritter, a man with a bent for natural philosophy and +metaphysics, describes an instrument which was to replace the divining +rod, and which he called "balancier." It was simple enough, consisting +of a metal strip that was balanced horizontally upon a pivot, and was +supposed to be put into motion in the presence of metals. Ritter used +this instrument in his numerous experiments with the Italian Campetti, +a man who had achieved a measure of fame in Europe for his ability to +discover springs and metals by the use of the divining rod. Carrying +the "balancier" on the tip of the middle finger of his left hand, Campetti—whose +integrity one cannot cavil at—had to touch repeatedly a +plate of zinc or pewter, and had to count aloud the number of touches +he made. The following curious law was found to obtain (that was +probably suggested to the subject by Ritter without his being aware of +it): with the first contact the "balancier" turns to the left, with the +second to the right, and with the third it remains at rest. At 4 it turns +once more to the left, at 5 to the right, at 6 it remains at rest, etc. It +remained immovable only at the so-called trigonal numbers (3, 6, +9, 15, 21, etc.). Ritter tells us that when Campetti did not really count +or did not think of the number, then it would not have any influence +whatever upon the action of the instrument. This Ritter ascribes to +the agency of electricity (which in the 18th and 19th centuries was made +to play very much the same <a name="tn_png_219a"></a><!--TN: "role" changed to "rôle"-->rôle that Satan had played in the 16th and +17th centuries). +</p><p> +The similarity of these two cases and that of Mr. Schillings is evident. +When the questioner of the horse and the bearers of the "balancier" +and of the divining rod are confident of success, they succeed. When +they do not expect success, they fail.</p></div> + +<div class="footnote"><p><a name="Footnote_V_22" id="Footnote_V_22"></a><a href="#FNanchor_V_22"><span class="label">[V]</span></a> The French investigators Vaschide and Rousseau make a reference +to this case, and mistakenly state the number of signals as 1500 instead +of 115<a name="refanchor30"></a><a href="#ref_30" class="fnanchor">[30]</a>. Ettlinger<a name="refanchor31"></a><a href="#ref_31" class="fnanchor">[31]</a> <a name="tn_png_219b"></a><!--TN: "taks" changed to "takes"-->takes over this wrong figure and makes the +additional mistake of assuming that the reference is to an original investigation +made by the two Frenchmen.</p></div> + +<div class="footnote"><p><a name="Footnote_W_23" id="Footnote_W_23"></a><a href="#FNanchor_W_23"><span class="label">[W]</span></a> All told, there are hardly more than half dozen experimental investigations +of the color-sense in mammals,—to speak only of these. +Three of them deserve especial mention. One, the work of the American, +Kinnaman,<a name="refanchor33"></a><a href="#ref_33" class="fnanchor">[33]</a> on two Rhesus monkeys. Then a brief but careful +piece of work by Himstedt and Nagel.<a name="refanchor34"></a><a href="#ref_34" class="fnanchor">[34]</a> These two investigators were +able to determine that their trained poodle could distinguish red of any +tone or shade from the other colors, and from Professor Nagel I learned +that later the tests were extended and the same was shown to be true +concerning the blue and the green. And finally there is an investigation +which hitherto has been known only from a reference which Professor +Dahl,<a name="refanchor35"></a><a href="#ref_35" class="fnanchor">[35]</a> the investigator, himself makes. The work is on a monkey, +Cercopithecus (Chlorocebus) griseoviridis Desm. (Professor +Dahl has kindly allowed me to look over the records of the experiments. +He intends to publish the monograph at an early date.) +</p><p> +All of these investigators arrive at the conclusion that the animals +tested by them possess color-sense. The monkey last-mentioned shows +one peculiarity: it was unable to distinguish a saturated blue from the +black. It will require further tests to clear this up.</p></div> + +<div class="footnote"><p><a name="Footnote_X_24" id="Footnote_X_24"></a><a href="#FNanchor_X_24"><span class="label">[X]</span></a> There is no justification for the wide-spread belief that the horse +which on account of the greater size of his eye (more correctly, on +account of the greater focal distance) receives larger retinal images of +objects than does the human eye, for that reason also sees objects, +larger than we do. Horses' shying is often explained in this way. But +the conclusion just mentioned is erroneous. The retinal image is not +the perceptual image. It undergoes many transformations within the +nervous system itself.</p></div> + +<div class="footnote"><p><a name="Footnote_Y_25" id="Footnote_Y_25"></a><a href="#FNanchor_Y_25"><span class="label">[Y]</span></a> "Butzenscheiben" are the small circular panes of green glass, used +in leaded windows in early days. They are high in the middle (hence +the name: "Butze," a protuberance) with a number of concentric circles +around the central elevation.—Translator.</p></div> + +<div class="footnote"><p><a name="Footnote_Z_26" id="Footnote_Z_26"></a><a href="#FNanchor_Z_26"><span class="label">[Z]</span></a> Since no opportunity was given us to examine Hans's eyes we do +not know what their condition is in this respect. Though it would have +been interesting to know, it would hardly make any difference in the +views presented. If Hans should prove to be either far or near-sighted, +then, if we are to make any supposition at all, it would be that the defect +could not be very great, since near sightedness exceeding 2 or 3 diopters +and far-sightedness exceeding one diopter is seldom found in the case of +the horse. According to Mr. von Osten, Hans at one time manifested +a tendency to shy easily. Be this as it may, for little could be concluded +from it, since in many extremely shy horses, no kind of visual imperfection +can be discovered.</p></div> + +<div class="footnote"><p><a name="Footnote_AA_27" id="Footnote_AA_27"></a><a href="#FNanchor_AA_27"><span class="label">[AA]</span></a> For the benefit of specialists I would say the following in addition +to the more general remarks just made. For the most part, the determinations +of refraction made on the eye of the horse are still rather +unreliable. In sciascopy there is a dispute among investigators concerning +ambiguous shadows, and in the use of the refraction-ophthalmoscope +no definite region of the eye's background has been adhered +to by the various investigators. It appears that Riegel, whose diligent +researches mentioned on <a href="#Page_164">page 164</a> were published in 1904, knew nothing +concerning the round area in the horse's eye, discovered by I. Zürn<a name="refanchor42"></a><a href="#ref_42" class="fnanchor">[42]</a> in +1902. Also, if so great a degree of astigmatism is really the rule as is +emphasized especially by Hirschberg<a name="refanchor43"></a><a href="#ref_43" class="fnanchor">[43]</a> and Berlin,<a name="refanchor44"></a><a href="#ref_44" class="fnanchor">[44]</a> then the simple +refractive index usually given—sometimes within a half diopter—would +be meaningless. Berlin<a name="refanchor45"></a><a href="#ref_45" class="fnanchor">[45]</a> and Bayer<a name="refanchor46"></a><a href="#ref_46" class="fnanchor">[46]</a> believe the vagueness of +the retinal image resulting from the astigmatism, is offset by this: that +the oval pupil functions as a stenopaic slit. In view of the width of the +horse's pupil this appears to me to be rather hypothetical. +</p><p> +Concerning Berlin's theory of deflecting astigmatism I would say the +following: Of the two ophthalmoscopic signs mentioned as being +characteristic of this form of astigmatism,—the concentric circles and +the arcuate deflection of the pathway of the fixated points,—when there +is a movement of the eye of the observer (or of the eye observed), according +to Berlin the former is not so constant as the latter. So far as +I know, the concentric ring formation is mentioned only by Bayer<a name="refanchor47"></a><a href="#ref_47" class="fnanchor">[47]</a> and +Riegel,<a name="refanchor48"></a><a href="#ref_48" class="fnanchor">[48]</a> and is said to occur principally in horses with myopic vision—and +hence, relatively, in a minority of cases. Judging from the particulars, +we are inclined to believe that a case of <a name="tn_png_219c"></a><!--TN: em-dash changed to hyphen before "lens"-->"Butzenscheiben"-lens +reported by Schwendimann<a name="refanchor48a" id="refanchor48a"></a><a href="#ref_48a" class="fnanchor">[48<i>a</i>]</a> is in reality a case of senile sclerosis. +Berlin repeatedly warns us against mistaking the one for the other.<a name="refanchor48b" id="refanchor48b"></a><a href="#ref_48b" class="fnanchor">[48<i>b</i>]</a> +The arcuate deflection, on the other hand, has not been mentioned elsewhere as a personal observation. In Berlin's calculation<a name="refanchor49"></a><a href="#ref_49" class="fnanchor">[49]</a> of the increase +in the extent of the retinal pathway an ambiguity has crept in. +He says that "in the astigmatic eye there are stimulated 207 times as +many nervous elements as would be stimulated in the ideally normal +eye." It ought to read "207 more" instead of "207 times as many." +And this number holds only for the one case computed by Berlin, and +under the specific assumption that exactly π/2 times the normal number +of elements were stimulated (571 instead of 364). Therefore the general +statement which Bayer<a name="refanchor50"></a><a href="#ref_50" class="fnanchor">[50]</a> makes in his text-book, that according to +Berlin's evaluation "207 times more nervous elements" are stimulated +in the astigmatic eye than in the non-astigmatic one, does not hold true. +</p> +<p><a name="closing"></a>Closing this note, a few remarks concerning the experiments made +by Dr. Simon and myself. All of the nine horses were tested for the +vertical image by means of the ophthalmoscope. In most cases Wolff's +electric speculum was used. Atropine was not employed.—For the +laboratory tests the adipose and the muscular tissues were removed +from the eye-ball and the rear part of the bulb cut away. The front +part, containing the cornea and the lens, was fastened over one opening +of a metal cylinder which was closed at the other end by means of a +disc of ground glass. The whole, approximately as long as a horse's +eye, was filled with a normal salt solution whose refractive index (1.336) +corresponds quite closely with that of the vitreous humor of the horse's +eye. The pressure from within was regulated so that on the one hand +it was not dimmed and yet on the other there were no wrinkles in the +cornea. The source of light—the filament of a Nernst lamp—was +moved about in a plane 120 cm. distant from the eye and perpendicular +to the optic axis. It was moved through the point of intersection as +well as at various distances from it. Movement in horizontal and vertical +directions was in each case along lines 150 centimeters in length, +which would correspond to an angle of vision of not less than 64°. The +pathway of the imaged point was controlled by means of the cross-hairs +of the telescope. If in the same way we observe through the sclerotic +of an intact eye-bulb a point of light falling upon the retina and shining +through the sclerotic and choroid (which is not difficult when we use an +intense light), then to the observer its pathway will, of course, appear to be +deflected convexly toward the periphery,—and the deflection will appear +the greater, the farther the point of light is removed from the optic axis.</p></div> + +<div class="footnote"><p><a name="Footnote_AB_28" id="Footnote_AB_28"></a><a href="#FNanchor_AB_28"><span class="label">[AB]</span></a> Königshöfer, who as we have already said, seconds the explanation +given by the ophthalmologist Berlin (and who confounds "Butzenscheiben" +astigmatism with the common, so-called regular form), believes<a name="refanchor54"></a><a href="#ref_54" class="fnanchor">[54]</a> +that not only astigmatism but also the shape of the blind-spot of +the eye must be taken into consideration. This portion of the retina, +where the fibres of the optic nerve enter the eye (and called "blind-spot" +because there are no cells there that are sensitive to light) is very nearly +circular in man, but differs in shape in the different species of animals. +Königshöfer thought he had discovered that a relatively elongated blind +spot was favorable to keenness of vision. If we place the mammalia +in series on the basis of their relative keenness of vision, he says, we +would find that this series is identical with the one in which they are +grouped with reference to the form of the blind-spot from the circular +up to the most elongated. (In such a series the marmot takes the place +of honor.) +</p><p> +This exposition is not very <a name="tn_png_219d"></a><!--TN: "satisfactury" changed to "satisfactory"-->satisfactory, however. We cannot be sure +what he means by "keenness of vision" ("scharfäugigkeit"). Is it +visual acuity in the usual sense of the term (as is said in one of his passages), +or keenness in the perception of the movements of objects, (this +would appear to be his real meaning), or both at the same time. But +whatever the significance he may put into the term, any such attempt +at grouping the lower forms must prove unsatisfactory from the very +start on account of the scant data which we possess on visual perception +in animals. The experiences of the hunt upon which Königshöfer +partly bases his view, are entirely inadequate for such a purpose. This +much is certain, that the Osten horse, in spite of a blind-spot which, +<a name="tn_png_219e"></a><!--TN: "thought" changed to "though"-->though somewhat oval, is by no means very elongated, possesses an +extraordinary acuity in the perception of movements. Even if the parallelism +mentioned by Königshöfer were really shown to exist, it would +not explain the matter until it were also shown in what way keenness of +vision is dependent upon the shape of the blind-spot,—a portion of the +eye which is not immediately operative in the visual sensation at all.</p></div> + +<div class="footnote"><p><a name="Footnote_AC_29" id="Footnote_AC_29"></a><a href="#FNanchor_AC_29"><span class="label">[AC]</span></a> I can find examples of supposed suggestion in the case of animals +given only by Rouhet.<a name="refanchor61"></a><a href="#ref_61" class="fnanchor">[61]</a> He says that by means of suggestion he taught +a half-year old half-blooded mare-colt which he had raised himself, to +fetch and carry, and this in a very short time. In order to indicate to +the colt what was wanted, Rouhet would concentrate with his whole +mind upon the object intended (a watch), and at the same time he would +bend forward slightly. In the third test, that is at the end of fifteen +minutes, he had accomplished his purpose, and in the tenth lesson, no +more mistakes occurred. The colt would fail to respond, however, as +soon as he refrained from making any gestures, or was in a laissez faire +frame of mind, or when he thought of other things. He therefore believes +that there must have been some kind of immediate, though inexplicable, +connection between the brain of the trainer and that of the +horse. I think the explanation is evident: the connection was not as +he thought, an immediate one, but arising through the mediation of the +man's attitude ("attitude un peu baissée"), and of his movements +("gestes"), both resulting from his intense concentration ("tension de +la pensée"). +</p><p> +In general we may say that, no matter what content we may wish to +put into the term "suggestion," not a single fact has since come to +light which would justify, and much less demand, the application of the +term to lower forms, unless we would expand the definition of the term +to the extent of comprising every kind of command, every arousal of +ideas, whatsoever. But it would then be nothing but a new name for +old knowledge<a name="refanchor62"></a><a href="#ref_62" class="fnanchor">[62]</a> and would lose all explanatory value. (Hypnotism, +so-called, in the case of horses, I shall discuss elsewhere in another +connection.)</p></div> + +<div class="footnote"><p><a name="Footnote_AD_30" id="Footnote_AD_30"></a><a href="#FNanchor_AD_30"><span class="label">[AD]</span></a> An illustration is given by Babinet<a name="refanchor66"></a><a href="#ref_66" class="fnanchor">[66]</a> concerning the horse of an +English lord. Mr. Burkhardt-Foottit, also, that excellent trainer, who +has been master for more than forty of the most highly-trained horses, +tells us that while sitting on a well-managed horse it sometimes happened that he had merely thought of making a certain turn, when the +horse immediately executed it, before he, the rider, had to his knowledge +given any sign or aid. An observation belonging under this head +is also made in Tolstoi's "Anna Karenina"<a name="refanchor67"></a><a href="#ref_67" class="fnanchor">[67]</a>, this perfect mine of +acute psychological observation. In the famous description of the race +we are told concerning Count Wronskij riding his Frou-Frou just behind +Machotin mounted upon Gladiator, who was leading the race: "At the +very moment when Wronskij thought that it was time to overtake +Machotin, Frou-Frou, divining her master's thought, increased her pace +considerably and this without any incitement on his part. She began +to come nearer to Gladiator from the more favorable, the near side. +But Machotin would not give it up. Wronskij was just considering +that he might get past by making the larger circuit on the off-side, +when Frou-Frou was already changing direction and began to pass +Gladiator on that side." Similar experiences might be gathered elsewhere. +Not infrequently the reflection of the rider that his horse had +not for a long time indulged in some trick peculiar to him, will immediately +call it forth; or doubts on the part of the rider concerning the +possibility of crossing some barrier, are often the cause of the horse's +fall or of his refusal to leap and of his running away.</p></div> + +<div class="footnote"><p><a name="Footnote_AE_31" id="Footnote_AE_31"></a><a href="#FNanchor_AE_31"><span class="label">[AE]</span></a> All the authors who have given practical suggestions for the training +of horses, whether free or with lunging reins, have great faith in +the efficacy of calls, but usually recommend a mingling of calls and +movements in the way of signs, (thus Loiset,<a name="refanchor71"></a><a href="#ref_71" class="fnanchor">[71]</a> Baucher,<a name="refanchor72"></a><a href="#ref_72" class="fnanchor">[72]</a> von <a name="tn_png_219f"></a><!--TN: "53" changed to "73"-->Arnim<a name="refanchor73"></a><a href="#ref_73" class="fnanchor">[73]</a>). +It therefore cannot be stated just in how far the calls really effect anything. +In other cases I am inclined to doubt outright the influence +which is ascribed to the auditory signs. Meehan<a name="refanchor74"></a><a href="#ref_74" class="fnanchor">[74]</a> gives an account of +a horse that was exhibited in London in the early 90's of the last century. +Pawing with his hoof, this horse apparently was able to count +and answer questions in arithmetic, and among other accomplishments +he was supposed also to be able to understand something of language. +In reality, however, he merely responded to cues which were disclosed +to the reporter by the trainer. In pawing, the horse was guided by +movements of the trainer, and in nodding or shaking the head he reputedly +got his cue from the inflections of the man's voice. Is it not probable +that in this latter case it was the movements which accompanied +speech that were alone effective in inducing the nod or the shake of the +head, so that the exhibiter was deceiving not merely the public, but also +himself? Perhaps we may also doubt the exposition made by the well-known +hippologist, Colonel Spohr.<a name="refanchor75"></a><a href="#ref_75" class="fnanchor">[75]</a> He tells us that it is easy to train +horses to raise the left foot or the right foot in response to the commands +"Left—foot!" or "Right—foot!" and that it will be the fore +foot when one is standing in front of the horse, and the hind foot if one +stands near the rear. It cannot be so very difficult, he thinks, even to +get the horse to understand the commands "Left (or right)—fore foot!" +and "Left (or right)—hind foot!"—and all without any other aids +but the spoken words. Should this really be possible without even +the slightest kind of designating movement?——The following case, +again, I believe is undoubtedly based upon a misinterpretation. Redding<a name="refanchor76"></a><a href="#ref_76" class="fnanchor">[76]</a> +relates concerning his nineteen-year old horse that he himself had +owned for thirteen years, and had always kept in single harness,——that +this horse not only understood the meaning of a long list of words, +such as: bureau, post-office, school, churchyard, apple, grass, etc., +but he also knew a number of persons by name, as well as their +places of residence. If he were told in advance to halt at a certain residence, he would do it without any further aid from the driver. For +this reason the happy owner felt certain that the animal possessed a +high order of intelligence and "that this horse does reason." What +sources of error were here operative, whether signs were given by means +of reins, or head or arm movements, could be determined only by a +careful examination of the case. +</p><p> +And finally we would exercise some reserve in entertaining the suggestions +for the acoustic education of horses which have come from +various sources. Colonel Spohr<a name="refanchor77"></a><a href="#ref_77" class="fnanchor">[77]</a> whom we have just been mentioning, +thinks that it would not be a difficult matter to get a horse +to respond with a walk to one smack of the lips, with a trot to two +smacks, and with a galop to three, and then he could be made to +slacken his pace once more into a trot in response to one long-drawn +"Pst!" and to stop in response to two. Others have gone even further. +Decroix,<a name="refanchor78"></a><a href="#ref_78" class="fnanchor">[78]</a> at one time leader in veterinary affairs in France, conceived the +idea of working out a universal language as regards the commands that +are given to horses, in the humane purpose of sparing them the whip. +He called it "Volapük hippique." For the commands "go," "right," +"left," and "halt," he suggests these: "Hi!" "Ha!" "Hé!" +and "Ho!" respectively. From these it was possible to make +eight combinations, such as "Hi! Hi!" for "Trot!" "Hé! Hé!" for +"Left about" (while the single "Hé" was to mean "Forward, to the +left!") "Ho! Ho!" for "Back!" etc. Decroix thought that the +whole system could be inculcated in a very few lessons. He even had +a medal struck which was to be awarded to the driver or rider who +should first exhibit a horse, thus instructed, to the Société Nationale +d'Acclimatation de France (of which Decroix was president). Eight +years have elapsed since then, but we have heard of no one who has +earned the medal mentioned. In the future greater care will probably +be exercised in the putting forth of such suggestions, and two sources +of error may be guarded against, viz.: involuntary movements on the +part of the rider or driver, and imitation of the horses amongst themselves. +(One horse, guarded by an experienced rider, may serve as +copy for ten others with inexperienced men in the saddle.)</p></div> + +<div class="footnote"><p><a name="Footnote_AF_32" id="Footnote_AF_32"></a><a href="#FNanchor_AF_32"><span class="label">[AF]</span></a> General Noizet<a name="refanchor79"></a><a href="#ref_79" class="fnanchor">[79]</a> has left us a story of the middle of the last century, +which in essential detail corresponds closely with the one just given. +The scene is a French chateau and the hero is—a rapping table, highly +prized on account of the intelligent answers it could give. Seated about +it were a number of ladies and at the other end of the room sat a French +savant, a member of the Academy. The ladies requested him to put a +simple mathematical question to the table, and complying with their +request, he asked for the cube root of 4. None of the ladies who sat +about the table knew the solution; the table unhesitatingly gave 6 raps. +This answer was refused as incorrect. The table was asked to try again, +and again it wrapped 6. For this it was bitterly reproached. Hereupon +the questioner, who during the whole time had remained in his place at +the other end of the room, came forward with the confession that the +table was innocent, that he had made a mistake. He had asked for the +cube root of 4, but had really meant to ask for the cube of that number, +viz., 64, and the table had as a matter of fact given the first numeral of +that number. +</p><p> +One is immediately struck by the analogy between this case and that +of Professor Schillings. In both cases those immediately concerned +(the women in the one, Mr. von Osten in the other) believe that a wrong +answer is being given repeatedly. The cause of the error lies in a person +who seemingly is not concerned with the response. (The Frenchman +asked the question, but did not sit at the table. Professor Schillings +sounded the notes, but it was Mr. von Osten who got the horse to tap.) +In both instances the questioner asks one thing, but had something else +in mind. (With the Frenchman it was a slip of the tongue; Mr. Schillings +did it purposely.) And finally, in both cases the response corresponds +not to the question that has been asked, but to that which has +been thought, so that, though seemingly wrong, the responses of both +table and horse were really correct. By way of explanation, Noizet +believes that he has a case of true thought-transference or "telepathy" +(<a href="#Page_108">page 108</a>). The questioner watched with utmost attentiveness the rapping +of the table, and the women in turn regarded the man. And thus, +Noizet believes, the man's thought was transferred to the minds of the +others without the mediation of eye or ear, etc., and hence unvitiated by +the words that had been spoken. I myself prefer another explanation. +At that moment in which the rapping arrived at the expected number, +the Frenchman executed a movement characteristic of release of tension +and to this the women of the circle reacted. It was not necessary that +they should be able to account for this afterward, (just as sometimes +occurs in the case of thought-readers<a name="refanchor80"></a><a href="#ref_80" class="fnanchor">[80]</a>). It is very probable, too, that +they were not of a very reflective turn of mind anyway. We are warranted, +I think, in regarding the two cases as identical in kind.</p></div> + +<div class="footnote"><p><a name="Footnote_AG_33" id="Footnote_AG_33"></a><a href="#FNanchor_AG_33"><span class="label">[AG]</span></a> Professor Flügel,<a name="refanchor82"></a><a href="#ref_82" class="fnanchor">[82]</a> basing his statements on an article appearing in +"Schorer's Familienblatt" (Berlin, 1890, No. 8, p. 128), gives an account +of similar experiments which were supposed to have been conducted by +the Zoological Society for Westphalia and Lippe, and presumably +showed that "the horses of the military do not understand the bugle +calls." No matter how well trained a horse may have been, it would +not respond to a signal. This report, however, is due to a mistake. +Such experiments have never been made by the society mentioned, so I +am told by its director, Dr. Reeker. Nor do I know of any one else +who has made experiments of this kind. However, Professor Landois,<a name="refanchor83"></a><a href="#ref_83" class="fnanchor">[83]</a> +the eminent zoologist, now deceased (founder of the scientific society +mentioned), tested four circus-horses for their musical ability and specifically +for their sense of musical time. He arrives at the conclusion that +horses "have no feeling for time, whatsoever." With but few <a name="tn_png_219g"></a><!--TN: Apostrophe changed to comma between "84" and "85"-->exceptions,<a name="refanchor84"></a><a href="#ref_84" class="fnanchor">[84,</a> <a name="refanchor85"></a><a href="#ref_85" class="fnanchor">85]</a> +all experts to-day are of the same opinion. Horse-trainers, +especially, are universally agreed on this point. It is easy to see in any +circus performance that it is not the horses that accommodate themselves +to the music, but that the music accommodates itself to them, +and that the trained horses<a name="refanchor86"></a><a href="#ref_86" class="fnanchor">[86]</a> are induced to do their artistic stepping +only by the aids given by their riders. Furthermore, all these horses are +trained without the use of music.——It would therefore appear that +the time had arrived when the tales of the dancing horses of the Sybarites +ought no longer to gain credence. Two Greek writers, Athenaeus<a name="refanchor87"></a><a href="#ref_87" class="fnanchor">[87]</a> +and Ælian,<a name="refanchor88"></a><a href="#ref_88" class="fnanchor">[88]</a> tell us that the inhabitants of Sybaris, far-famed for their +luxurious habits, had trained their horses to dance to the music of flutes +during their banquets. Building upon this, the men of Crotona, in one +of their campaigns against the Sybarites, ordered the flute-players to +play the tunes familiar to the Sybarite horses. Immediately the well-trained +steeds began to dance, thus throwing the whole Sybarite army +into confusion, and the men of Crotona won the day. (The same story +is told in more detail concerning the horses of the inhabitants of Cardia. +Both accounts, somewhat mixed, are to be found in Julius Africanus,<a name="refanchor89"></a><a href="#ref_89" class="fnanchor">[89]</a> +a writer of the third century of the Christian era.)—In recent years a +French veterinary surgeon, Guénon,<a name="refanchor90"></a><a href="#ref_90" class="fnanchor">[90]</a> experimented on the effect of +music upon the horses of the military. He entered their stalls, playing +upon a flute, and noted their behavior. Four-fifths of the animals, he +says, were deeply moved, yes, delighted, even, ("charmés." One interpreter<a name="refanchor91"></a><a href="#ref_91" class="fnanchor">[91]</a> +calls it a case of hypnosis!). This emotional excitement was +expressed—somewhat unaesthetically—by the dropping of excrementa. +Guénon characterizes the feeling-state of these animals as being a mixture +of pleasure and astonishment, of satisfaction and excitement +("mélange de plaisir et d'étonnement, de satisfaction et de trouble.") +He also asserts that the horse's musical taste is similar to our own. But +I can find nothing in his whole exposition which might prove this. Indeed +there is nothing that could be interpreted as anything other than +a purely sensuous effect upon the horses. I may go a step farther and +say that thus far the sense of music, i. e., understanding of melody, +harmony and rhythm, has not been shown to exist in any animal. Some +animals may, however, be susceptible to the sensuous pleasantness of +the tones themselves.</p></div> + +<div class="footnote"><p><a name="Footnote_AH_34" id="Footnote_AH_34"></a><a href="#FNanchor_AH_34"><span class="label">[AH]</span></a> I cannot enter upon a discussion of the latest psychological problems, +here involved, partly because that would take us beyond the purpose +of this monograph, and partly because they are still moot questions +and hence not suited to popular treatment. Briefly though, they are +these: What is the nature of the relationship between cognitive and +affective states on the one hand and involuntary, (so-called expressive) +movements on the other? Is this connection an external thing, as it +were, an association arising as a habit formation, or does every idea +partake essentially of a motor character? Do purely cognitive states +give rise to such movements, or does the movement impulse depend +more particularly upon the affective consciousness accompanying the +cognitive states? And in how far do given kinds of expressive movements +depend upon certain ideational types (c.f. <a href="#Page_95">page 95</a>)? Thus, +what is the influence of the visual image upon the gestures for "up," +"down," etc.? And then, are these involuntary movements, when not +noted, truly unconscious, or merely not attended to,——in other words, +are they beyond the pale of consciousness or merely "at the fringe?" +The various writers speak almost without exception of unconscious +movements in the strict sense of the term. My own introspections, however, +have led me to doubt whether they are quite unconscious. Since +I have attained some practice I am able to describe in detail (under +conditions of objective control) my involuntary movements, no matter +how slight, even down to mere muscular tensions. None of my subjects, +however, has as yet succeeded in this. It is no very easy matter +to be on the lookout for some unknown movements which might eventually +occur, while attempting to concentrate attention to the utmost +upon a certain definite ideational content, for this very dividing of +attention effects a decrease in the force of the movement, and thus +makes it all the more difficult to discover. From my own experience, +however, I am inclined to believe that these movements are not unconscious, +but merely unattended to, in other words, we have a narrowing +down of the apperceived content within certain limits, but not a narrowing +down of consciousness, (much less a "splitting" of consciousness +or of personality as the thing unfortunately has sometimes been called). +In order, however, not to be guilty of premature judgment, I have +avoided the terms "unconscious" and "unattended to," and chose expressions +which leave these finer distinctions untouched.</p></div> + +<div class="footnote"><p><a name="Footnote_AI_35" id="Footnote_AI_35"></a><a href="#FNanchor_AI_35"><span class="label">[AI]</span></a> The mental state just described is probably essentially the same as +that of the spiritualistic "mediums" when they are occupied with table-rapping +and table-moving. In both cases concentration is very intense,——in +other words, the field of attention is limited. We saw that this state +not only favors the tendency toward involuntary movement, but on account +of the absorption of the individual's attention by a certain limited +content, the person will be unaware of the voluntary movements as +they occur. And we are not necessarily here dealing with neurasthenic, +hysteric, or other diseased nervous conditions. In the case of table-rapping +there are movements of the hands, in our case there are those +of the head. Our head, balanced as it is upon the cervical vertebral +column, is continually in a state of unstable equilibrium and therefore +peculiarly susceptible to movement-impulses of every kind. But I could +induce not only movements of the head, but also of the arms and legs, +and this by having the subject assume a posture which enabled him to +hold arms or legs in as unstable a position as possible. He might +stretch out his legs horizontally before him, or he could raise them vertically +upward as in the hand-stand in gymnastic work. An extract +from a treatise by Count A. de Gasparin,<a name="refanchor94"></a><a href="#ref_94" class="fnanchor">[94]</a> which appeared about the +middle of the last century, may serve to show how close the correspondence +between the two processes, that of getting the table to rap +and that of causing Hans to respond, really is. The report of this +writer, based upon the detailed record of his tests in table-moving and +table-rapping, closely parallels in many minute <a name="tn_png_219i"></a><!--TN: "detail" changed to "details"-->details the observations +which were made in the course of our experimentation with Hans. The +case is all the more remarkable when we bear in mind that this writer +did not seek the cause of the phenomena, as we did, in involuntary movements, +but thrusting aside this explanation, he posited the cause in the +agency of some mysterious fluid. It may not be amiss to say that this +as well as most other references were consulted after the present experiments +and introspections had been completed. Of the page references +preceding the following citations, the first always refers to the page in +the French original, and the other, enclosed in brackets, to the parallel +passage in the present monograph. +</p><p> +P. 49 <a href="#Page_31" class="fnlargeanchor">[31]</a>. Some questioners are especially suitable ("experimentateurs +hors ligne"), but in their absence, other persons may also operate +successfully ("le succès, quoique moins brillant alors, n'est pas impossible.") +</p><p> +P. 25 <a href="#Page_229" class="fnlargeanchor">[229]</a>. But even the most suitable questioners do not always +succeed equally well ("les plus sûrs d'eux-mêmes ne réussissaient pas +également tous les jours.") +</p><p> +P. 42 <a href="#Page_151" class="fnlargeanchor">[151]</a>. When the questioner is in any way indisposed, the +measure of success is also less. +</p><p> +P. 91 & 87 <a href="#Page_150" class="fnlargeanchor">[150]</a>. The Questioner must first get into the sweep of +things ("en train"), and once he has done so, all interruption whatsoever +must be avoided. +</p><p> +P. 91 <a href="#Page_93" class="fnlargeanchor">[93]</a>. Unless there is sufficient tension on the part of the questioner, +the test will fail. ("La volonté est-elle absente, rien ne bouge.") +</p><p> +P. 210 <a href="#Page_93" class="fnlargeanchor">[93]</a>. When there is too low a degree of tension, then too +great a number will be tapped ("si votre volonté ne les [les tables] arrête +pas au moment où se termine le chiffre pensé, elles continueront +indéfiniment.") +</p><p> +P. 31 <a href="#Page_93" class="fnlargeanchor">[93]</a>. But too great concentration of attention will also produce +failure ("s'il n'arrivait ... de désirer trop fortement le succès et de +m'impatienter en cas de retard, je n'avais plus aucune action sur la +table.") +</p><p> +P. 36 <a href="#Page_151" class="fnlargeanchor">[151]</a>. If the proper mood ("entrain habituel") is wanting and +the tests are unsuccessful, it is best not to attempt some new and difficult +experiment, but to turn to some that are simpler and more entertaining +("La table obéissait mal; les coups étaient frappés mollement et +comme à regret.... Alors nous avons pris un parti dont nous nous +sommes bien trouvés; nous avons persévéré, et persévéré gaiement; ... +nous avons écarté la pensée des tentatives nouvelles, et insisté sur les +opérations aisées et amusantes. Après un certain temps les dispositions +étaient changées, la table bondissait et attendait à peine nos commandements.") +</p><p> +P. 199 <a href="#Page_41" class="fnlargeanchor">[41,</a> <a href="#Page_90" class="fnlargeanchor">90]</a>. It is not necessary to enunciate the questions aloud +("On est convenu que celui qui commanderait ne prononcerait pas à +haute voix le nombre de coups, mais se contenterait de les penser, après +les avoir communiqués à l'oreille de son voisin. Eh bien! la table a +obéi. Il n'y a jamais eu la moindre erreur.") +</p><p> +P. 199 <a href="#Page_64" class="fnlargeanchor">[64 ff.]</a>. The large numbers are tapped more rapidly than the +small ones ("la table a indiqué notre âge tel qu'il était dans notre esprit, +se hâtant même de la manière la plus comique lorsque le nombre +des coups à frapper était un peu considérable.") +</p><p> +P. 210 <a href="#Page_35" class="fnlargeanchor">[35 ff.]</a>. Tests in which "procedure was without knowledge" +failed completely ("Les tables ne révèlent pas ce qui n'est pas dans la +pensée et dans la volonté de l'expérimentateur; quand on veut les +charger d'autre chose que d'obéir comme des membres, on arrive à des +erreurs continuelles.") +</p><p> +P. 28, 29, 217 <a href="#Page_72" class="fnlargeanchor">[72]</a>. When of two experimenters each tries to get +the horse to tap a different number, then that one who is the better able +to compel the animal's attention, will be the successful one. ("L'un veut +faire prévaloire un chiffre pensé plus considérable, l'autre un chiffre +pensé moins considérable.... Eh bien: l'opérateur le plus puissant +l'emporte." "Ainsi A est chargé secrètement de faire frapper 25 +coups, B est chargé secrètement de l'arrêter à 18; A l'emporte, et les +25 coups s'achèvent.... On fait maintenant l'inverse: B est chargé +secrètement de faire frapper 13 coups; A est chargé secrètement de +l'arrêter à 7; A l'emporte encore et le chiffre 7 ne peut être dépassé.")</p></div> +</div> + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_212" id="Page_212"></a>[Pg 212]</span> +<h2 style="padding-bottom:1em;"><a name="CHAPTER_VI" id="CHAPTER_VI"></a>CHAPTER VI</h2> + +<h2 style="padding-bottom:1em;">GENESIS OF THE REACTION OF THE HORSE</h2> + + +<p><span class="firstwords">In</span> the preceding discussion we have regarded the +achievements of the horse as well as Mr. von Osten's +explanation of them, as matters of fact. Let us now consider +the question: How did the horse come by these +achievements, and how did its master arrive at his curious +theory in explanation of them? Did he indeed seek +to instill in the horse's mind the rudiments of human +culture through long years of painstaking instruction in +accordance with the method described in <a href="#SUPPLEMENT_I">Supplement I +(page 245)</a>? If that is the case, then, of course his hoped-for +success was only seeming, not real. Or did he, as so +many critics aver, systematically train the horse to respond +automatically to certain cues, and propound his +theory merely for the purpose of misleading the public? +There might possibly be another alternative, viz.: was +there a mixture of instruction and of training to respond +to cues?</p> + +<p>The production of the horse's achievements would not +require a great deal of explanation, if it were a case of +mere training for the purpose of establishing certain responses +to certain cues. It might be desirable, however, +before deciding in favor of one of these possibilities, to +indicate briefly the process of development, as it might +occur, if the point of view is taken that <i>bona fide</i> instruction +was given.</p><span class="pagenum"><a name="Page_213" id="Page_213"></a>[Pg 213]</span> + +<p>This development would probably be as follows:—Mr. +von Osten, as the result of theoretical speculation or of a +misinterpretation of the facts of experience, having arrived +at the conclusion that the horse possessed extraordinary +capacity, finally undertook to instruct a certain +horse for a period covering three years. This one having +died, he, nothing daunted, undertook the education of +another one. What it was that influenced this old +teacher of mathematics to deprive humankind of the benefit +of his extraordinary pedagogical ability and love of +teaching, we do not know. It may be that he had had +bitter experience in that line, or again, mayhap the newness +and tremendousness of this other task stimulated +him. His first problem must have been to arouse the interest +of the animal in this process of education. It was +hardly to be believed that Hans would eagerly coöperate +in a process which promised to yield him no immediate +benefit. The teacher sought to overcome this lack of immediate +interest by the means of rewards. To Hans the +sweet carrot was as toothsome a bite as candy is to the +child. And since the horse was furthermore kept on low +rations on account of the relatively low amount of physical +exercise he took, the anticipation of the carrots was +doubly enticing.</p> + +<p>The first thing that Mr. von Osten sought to teach the +horse, according to his own statement, was the significance +of the names of colors and of the spatial directions such +as "up", "down", etc. In the case of children there +is a simple test by means of which we may discover if +they have put any content into these words. The test is: +Do they, themselves, use them correctly? Do they call +the blue, blue, and the red, red? Since the horse could +not speak, his instructor had to give him some means by<span class="pagenum"><a name="Page_214" id="Page_214"></a>[Pg 214]</span> +which he could make himself understood. He taught +Hans to approach the colors and select the cloth of the +color wanted. He also taught him to make those movements +of the head or body which correspond with the +expressions: "up", "down", etc.</p> + +<p>First of all, Hans had to be taught to bring the cloths. +Then began the pointing out of the different colors, accompanied +each time by their proper names. It is very +probable that at first Hans had to be led each time to each +separate colored cloth and taught to raise it or to touch +it with his nose. Later, Mr. von Osten, after having pronounced +the name of the color, remained at his place, +with his head and body directed to the cloth in question +and gazing intently at it, in order to see whether or not +the horse was pointing out the right one. Naturally +Hans would, at first, fail a hundred times where he would +succeed but once, but since the horse would receive the +anticipated reward in case of success, he gradually became +conscious that this reward was attached to executions +which had some special mark. This special mark +would be expressed in human speech by the statement +that the horse would go in the direction indicated by the +position of the instructor's body. For Hans, of course, +this would not take the form of an abstract statement, +but simply of a definite way of seeing and of going and a +correlation of the two in a certain definite manner,—the +whole being a process, the elements of which remained +unanalyzed and unaccounted for by Hans. Owing to the +position of the eye, it was possible for him to keep his +master within his field of vision, while he was approaching +the cloths. And only when he had correlated his approach +in a certain definite manner with his visual perception +of the master, i. e., only when he had felt his way,<span class="pagenum"><a name="Page_215" id="Page_215"></a>[Pg 215]</span> +as it were, along the latter's line of vision, did he receive +his reward. A sufficient number of repetitions was all +that was necessary to establish an association in the +psychological sense of the term. In the same manner, +dogs will learn, as was indicated on <a href="#Page_177">page 177</a>, to bring an +object upon which the master has fixed his gaze, it mattering +little whether or not the name of the object be +enunciated. There is only this difference, that, in the +case of the dog it is not possible to keep the image of the +master within the field of vision; but neither is it necessary, +for he has recognized the object before he has +started for it. We must remember, however, that it does +not simplify an attempt at explanation to assume that Mr. +von Osten consciously trained the animal to respond to +certain bodily positions of the questioner. For, even in +this case, it would be necessary to explain how it was possible +for him to train the horse to heed the cues.—In the +course of time, the instructor may have noticed that whenever +he moved during the course of a test the horse invariably +failed. But he may have regarded this merely as +an incidental distraction and afterward was careful to remain +quiet. As soon as he increased the number of cloths +upon the floor, it was no longer possible for him to give +the horse such accurate directive signs, and the number +of errors consequently increased. Ascribing them to the +inattentiveness of his pupil, he sought to encourage him +by such calls as "look out", "look there", "see there", +believing that, thus, he was directing the horse's attention +to the desired color. Without understanding the meaning +of the calls, Hans learned, however, to keep moving +just as long as the calling continued, for if he did this he +was regularly rewarded. An association was established +between the call and the impulse to move on. And with<span class="pagenum"><a name="Page_216" id="Page_216"></a>[Pg 216]</span> +these two associations established, Hans gave the impression +of having grasped the meaning of the color terms.</p> + +<p>The origin of the proper movements in response to the +terms "up" and "down" may be explained by the fact +that the movements themselves were practised in a +purely external fashion. Thus, whenever the word +"left" was pronounced, the horse's head was pulled to +the left by means of the bridle or the reward was held off +to that side. Later, Mr. von Osten, who looked <a name="tn_png_223"></a><!--TN: "expectpectantly" changed to "expectantly"-->expectantly +at the horse's head, whenever he pronounced the +word would unconsciously move his own head in the direction +in which he desired the horse to turn. This is +quite in accord with the words of Darwin to the effect that +whenever we wish an object to move in a certain direction +it is well-nigh impossible for us to inhibit an unconscious, +involuntary movement in that direction. Proof for +this may be found on all sides, in daily experience.<a name="refanchor97"></a><a href="#ref_97" class="fnanchor">[97]</a> +Imagine, for instance, the strain sensations of the bowler +or billiard player as he follows the moving ball. It is impossible +to decide whether Mr. von Osten, consciously +continued to image the head movements which he expected +the horse to make or whether these anticipatory +images later remained below the threshold as was always +the case with Mr. Schillings and myself (see <a href="#Page_100">page 100</a>). +But this question is of little significance, for even assuming +that he always thought of the movement he expected +on the part of the horse, this by no means implies that he +was conscious of the movements on his part, which were +associated with the thought process.</p> + +<p>Everything up to this point might be explained as the +working of simple memory association, but when we +come to problems in counting and arithmetical calculation, +we are in the field of conceptual thought. Here,<span class="pagenum"><a name="Page_217" id="Page_217"></a>[Pg 217]</span> +again, it was necessary for Mr. von Osten to invent a +suitable means of expression for the horse, and once more +this had to be borrowed from the treasury of gesture-language. +Tapping with the hoof was naturally hit upon +as one of the normal, expressive movements of the horse. +This has long been used by trainers, in preparing horses +for show purposes. The method used in training the +horse to make this response is of no import, whether it +was by touching his foot with the hand, or tapping his +leg, or by any other means.</p> + +<p>It is possible that many will declare, as being nonsensical, +any attempt to introduce number-concepts<a name="FNanchor_AJ_36" id="FNanchor_AJ_36"></a><a href="#Footnote_AJ_36" class="fnanchor">[AJ]</a> into +an animal's mind, because the necessary motor basis is +lacking. We will not, just at this point, stop to discuss +whether or not it was not possible to develop number-concepts +from purely auditory or visual representations. +It is evident, however, that Mr. von Osten believed that +a motor basis of some sort was essential. In the case of +man this basis is found in the enunciation of the number +names (or in the manipulation of the fingers). Mr. von +Osten seemed to think that he was justified in assuming +that, even in the case of the horse, some form of inner +articulation of the word-sounds was possible;—at the +same time, in so doing, he did not blink at the psychological +difficulty of this hypothesis. The tapping of the +foot was to be regarded merely as the expression of the +process of inner counting, but not as the motor basis of +the process. For this latter purpose tapping would be +quite inadequate, for the number complexes which arise +in the summation process of counting, could not be dif<span class="pagenum"><a name="Page_218" id="Page_218"></a>[Pg 218]</span>ferentiated +by mere tapping with the foot, any more than +a child could learn to count by employing only one finger. +Mr. von Osten evidently imagined the process was somewhat +like this: Whenever Hans was about to count 5, he +would enunciate inwardly the numbers from 1 to 5, and +would accompany each word with a tap of the foot. +Since, furthermore, wooden pins and balls could be used—as +in the case of children—for giving visual content in +learning the significance of the number-terms, it seemed +as if all the conditions necessary for the formation of +number-concepts were supplied. However, the most essential +thing had to be presupposed, viz.: that the horse +virtually possessed the general power of forming concepts,<a name="FNanchor_AK_37" id="FNanchor_AK_37"></a><a href="#Footnote_AK_37" class="fnanchor">[AK]</a> +and that all that had been lacking was the suitable +conditions for its development. Mr. von Osten held +tenaciously to this conviction, and it was this conviction +that was the basis for the infinite patience with which the +tests had been pursued.</p> + +<p>To come now to the learning process itself;—we may +assume that, at first, whenever the horse began to tap in +response to commands, he would receive a reward for this +purely mechanical feat. Wooden pins were then planted +on the ground and designated as: one, one two, etc., and<span class="pagenum"><a name="Page_219" id="Page_219"></a>[Pg 219]</span> +each time someone would raise the horse's foot as many +times as the count demanded (see <a href="#SUPPLEMENT_I">Supplement I</a>). Then +Mr. von Osten would take his stand at the horse's side +and would command him, let us say, to tap 3. Hans +noting merely (from his master's position) that he was +expected to tap, would begin. The instructor, who had +bent forward in order to watch the horse tapping,<a name="FNanchor_AL_38" id="FNanchor_AL_38"></a><a href="#Footnote_AL_38" class="fnanchor">[AL]</a> would +involuntarily straighten up again at the third tap, without +being conscious of it and quite unaware that he was thus +giving a signal. The horse would be startled, and sometimes +he would immediately cease tapping and sometimes +not. But it was only in the first case that he would receive +a reward. Thus, unknown to the instructor, an +association became established between the sight of the +upward jerk of the instructor and the act of ceasing to +tap. To be sure, the animal would receive sundry visual +impressions from the wooden pins set up before him and +the auditory stimulations of the spoken number names, on +the basis of which, the concepts were to be formed in his +mind. But in this chaos of visual impressions (at times +there were two wooden pins, then three, then four, sometimes +there were the pins, at others, the balls of the counting-machine)—and +in the babel of word-sounds—which +evidently meant nothing but noise to him—amidst all this +there was but one constant element: the final movement +of the instructor's body. The moment the horse reacted +to this, he would receive the tidbit at the hands of his +overjoyed master, and thus he became more and more accustomed +to attend to this jerk, even after it had grad<span class="pagenum"><a name="Page_220" id="Page_220"></a>[Pg 220]</span>ually +decreased in scope. And the reason again, why this +jerk tended to become less pronounced was that the tests +were gradually becoming more and more successful. For, +corresponding to the degree in which the horse began to +react properly, the instructor's tenseness and excitement +tended to decrease, and with this decrease of the emotional +element in the man's consciousness, the accompanying +non-voluntary, expressive movement gradually became +less pronounced until it attained that extraordinary +refinement which it possesses to-day. We noticed also, +that whenever the horse, for any reason, had to be trained +anew, Mr. von Osten's movements would, on the whole, +become somewhat more gross, as for instance after the +tests with the blinders. There is not a shadow of a +doubt that this increase in the movement's extent was entirely +unintentional, since the horse could not see his master +at all on account of the blinders which had been +attached to the trappings.</p> + +<p>In the same way it is possible to explain the details. +Mr. von Osten himself said that at first Hans had tapped +at times with his left foot, at times with his right, just +as he pleased. But later his master taught him to tap +only with the right. Whenever he began with the left, +Mr. von Osten would immediately interrupt him, and he +was allowed to add only a final tap with his left foot. +Thus, this additional tap which was sometimes made with +the left foot was but the vestige of an earlier rudimentary +habit. The signal for it was the stooping posture in which +the master remained after the head-jerk had been made. +Whenever Mr. von Osten had given Hans a small number +to tap, he would bend forward only a little. But when +he expected a larger number he would bend forward +somewhat more, owing to the desire to observe the tap<span class="pagenum"><a name="Page_221" id="Page_221"></a>[Pg 221]</span>ping +more carefully. From the slight inclination of the +master's body the horse would get the cue that he was expected +to tap for a short time only, by the greater degree +of inclination he would know that he was to tap for +a longer period. In the second case he tapped rapidly +and did not raise his foot as high from the ground—evincing +a regard for the saving of energy, which may +well be attributed to a horse. And thus arose the connection +between the degree of inclination of the instructor's +body and the horse's rate of tapping.</p> + +<p>So, now that the ability to count and solve problems +had become fixed—as the old gentleman thought—he began +to instruct the horse in other branches. Since everything +had been translated into terms which were to be +expressed by means of tapping with the foot, and thus +really put into terms of number—which was perhaps +natural for an old teacher of mathematics—the same +mechanism was involved in these accomplishments as in +those of counting, etc. Mr. von Osten saw the animal's +intelligence steadily increase, without having the slightest +notion that between his words and the responsive movements +of the horse, there were interpolated his own unconscious +movements—and that thus instead of the much +desired intellectual feats on the part of the horse, there +was merely a motor reaction to a purely sensory stimulus. +It has been a common custom of man to posit some extraneous +cause for movements resulting from certain involuntary +motions of his own, of which he is not aware, +(witness the divining-rod).<a name="FNanchor_AM_39" id="FNanchor_AM_39"></a><a href="#Footnote_AM_39" class="fnanchor">[AM]</a> And furthermore, when<span class="pagenum"><a name="Page_222" id="Page_222"></a>[Pg 222]</span> +these results appear to be rational, the tendency is to +seek their cause in some extraneous intelligence, not his +own. Just as the spiritualists ascribe the "messages" +which are revealed to them through table-rapping, to certain +rational spirits, so Mr. von Osten credited the intelligence +of the horse with the result produced by his own +involuntary signs—i. e., with the proper solution of problems.</p> + +<p>Two other phenomena may have tended to strengthen +Mr. von Osten's belief in Hans's intelligence. One was +the misleading similarity with which the horse's supposed<span class="pagenum"><a name="Page_223" id="Page_223"></a>[Pg 223]</span> +errors in computation and the poorly adjusted concentration +of the questioner, were expressed. We recall the +difficulty in the case of very high numbers. This might +easily be considered as being due to the horse's ability to +work more readily with small, rather than with large +numbers, whereas, as a matter of fact, it was due solely +to the difficulty of the questioner to keep his attention +concentrated upon the number for so long a time. We +recall also the frequency of errors of one unit too few +and one unit too many. These were easily interpreted as +miscounts on the part of Hans, but in truth were the re<span class="pagenum"><a name="Page_224" id="Page_224"></a>[Pg 224]</span>sult +of the poorly concentrated attention of the questioner. +Added to this was the seeming independence and self-sufficiency +of the horse. Often the number given by him +was other than that desired by his master. Usually Hans +was in the wrong in such cases, but sometimes, too, he +was right. At any rate, this served to give the impression +of independence of thought which his master so thoroughly +believed he possessed, and which was the goal +of his endeavors—though as a matter of fact he was +farther removed than ever from that goal.</p> + +<p>Some may ask: Does not this whole process partake of +the essentials of all training, (though cumbersome and +misunderstood, to be sure), and is there any need of investigating +whether or not the actual development was +of the sort here outlined, or whether it actually took the +course common to all training?</p> + +<p>In order to answer this question we must determine +more specifically what we mean by the term "training". +Usually we take it to mean the establishment in the animal, +of definite habits of motor reaction in response to +certain stimuli purposely selected by the trainer, and without +involving any process of animal consciousness other +than association. Such a conception may be applied also +to man, if we assume that the higher thought processes +can be eliminated. If that were the case, the above definition +would not have to be changed, not even with regard +to the word "animal", for we must take it in the antique +sense of "zoon", a signification readopted by modern +zoology. The concept may be widened, however, by +omitting the differentia of "purpose", or even more, by +including the habitual association of ideas or images +(instead of movements) with certain sensory <a name="tn_png_231"></a><!--TN: Comma changed to period after "stimuli"-->stimuli. +But in so doing, we must bear in mind that we are going<span class="pagenum"><a name="Page_225" id="Page_225"></a>[Pg 225]</span> +beyond the usual content which in everyday practice is +put into the term "training". Especially, when we cease +to regard the presence of purpose in the trainer's mind +(both in giving the stimulus as well as in the habituation +of the animal to them) as essential. When this is done, +the conception of training really resolves itself into the +much wider conception of habit-building, and the whole +discussion becomes merely a quarrel over words. In +order to obviate this, let us bear in mind that in the following, +the word "training" is always taken in the usual +and narrower sense. The term then is still ambiguous +only in so far as it has not merely its original significance +of the <i>act</i> of purposely habituating (a person or an animal) +to perform certain definite movements, but by transference +is also used to denote the <i>effect</i>, i. e., the occurrence +of the movements in question. But this does not +really detract from the clearness of the concept itself.</p> + +<p>Having cleared up the question of definition, let us return +to our original problem: Does the hypothetical account +of the probable development of the horse's reactions, +which is given on pages <a href="#Page_213">213</a> to <a href="#Page_220">220</a>, represent a +case of training? This must be denied decidedly with +regard to the tapping of numbers and the solution of +arithmetical problems. For here the sensory stimuli which +were purposely given, i. e., the wooden pins, the balls, +and the spoken words, were intended to subserve the +function of arousing not movement, but thought processes +in the horse; whereas the function of the horse's +movements was to give expression to these thought +processes. Of the really effective stimuli—the slight +movements on his part—the master was never conscious, +much less were they purposely made. The same holds +true for the "up" and "down", "yes" and "no", etc.,<span class="pagenum"><a name="Page_226" id="Page_226"></a>[Pg 226]</span> +for here also Mr. von Osten counted upon the rise of the +corresponding concepts, and not merely upon a purely external, +mechanical association of meaningless sounds with +certain movement-responses on the part of the horse. +This might also explain the genesis of Mr. von Osten's +belief that Hans was able mentally to put himself in the +place of the questioner, (<a href="#Page_19">page 19</a>). At any rate it is +very improbable that he, Mr. von Osten himself, clearly +distinguished between the concept: "up" and the sound +of the word "up". When we come to consider the +horse's selection of the colored cloths, and even more his +leaping and rearing, we find that the distinction between +"training" and "instruction" vanishes. If we had to +deal only with this class of achievements, we might perhaps +say, without fear of going very far wrong, that the +only difference between this and the ordinary form of +training was that Mr. von Osten had intended to train +the horse to respond to auditory signs (words), but had +unintentionally trained him to respond to visual signs instead. +But it is not this type of performance that has become +the bone of contention. Just as it would be misleading +to maintain that Mr. von Osten's effort was nothing +other than a case of training, so it also would be unjustifiable +to designate the results of his effort by that name, +since the really effective stimuli were not, as has been +pointed out just now, given intentionally.</p> + +<p>As far as the horse is concerned, it is a matter of indifference +whether or not really effective stimuli were +given intentionally by the questioner. The animal knows +nothing of human purposes and if he were transferred to +a circus, he would find nothing new in the method employed +there, except the use of the whip. We, however, +define our concepts from the human and not from the<span class="pagenum"><a name="Page_227" id="Page_227"></a>[Pg 227]</span> +horse's point of view. We may definitely say, therefore, +that the method described cannot be regarded as that of +training, neither in its application nor in the effect produced, +though in the latter it closely simulates the effects +of the training method.</p> + +<p>Having thus differentiated between the methods of instruction +and training, let us now attempt to decide on +the basis of such indications as we may possess, which of +the two was actually represented by the development of +the horse's attainments. Surveying the facts which we +have at hand, we may say that there are hosts of reasons +why we cannot assume that it was a case of training. +Everything that we know from our own observation and +from the well-attested statements of others, with regard +to the actual process of instruction, weighs against the +assumption. Another evidence of this is the long period +of time which Mr. von Osten required (both in the case +of Hans, as well as with his predecessor), whereas the +same end would have been much more speedily attained +if it had been a case of training. A further argument is +the fact that a large horse was selected for the purpose, +whereas a small mare would have been far more suitable, +(c. f., "Clever Rosa", <a href="#Page_7">page 7</a>). Again, the whip, +that sorcerer's rod of all professional trainers, was here +absent. And finally, many traits of character of Mr. von +Osten, as well as his conduct during the whole course of +events, militate against such an assumption. He generously +turned the horse over to us, as he had given it over +to Count zu Castell, Count Matuschka and Mr. Schillings. +He eagerly besought a scientific investigation. He had +made several reports to different ministries. All of these +acts could only hasten the denouément. What could have +been his motive? Some thought they detected an effort<span class="pagenum"><a name="Page_228" id="Page_228"></a>[Pg 228]</span> +at pecuniary speculation, and an advertisement of June, +1902, in the "Militärwochenblatt", in which Hans was +offered for sale, seemed to confirm the conjecture. Mr. +von Osten says that this occurred at a time when he himself +was sick and had become tired of the job. And why +should he not be willing to sell even a thinking horse, +since he had become convinced that any other could be +instructed in the same way? Besides, I have it on good +authority that after the publication of the September report +he received several exorbitant offers; to mention +only one of them: a local vaudeville company was ready +to pay him 30,000 to 60,000 marks per month. He refused +every one of these offers. Some may say that perhaps +he wanted still more. But if he knew that the day of +judgment was close at hand, he also knew that before +then, if ever, was the sunshiny day on which to make his +hay. A more auspicious time he could never hope to see +again.—Let us add, once more, that he never charged +admission to any of Hans's performances, although there +were many who were anxious to see the horse, and many +enthusiasts had come from a great distance. And finally, +he was an old man, unmarried and entirely alone, a property +owner, but a man whose wants were few and very +simple—and his Hans was almost his sole companion. +Is it possible that such a man, one who had all the pride +of gentle birth, would become a trickster in his old age, +all for the love of money?</p> + +<p>The unreliability of Mr. von Osten's signs is good +proof of their involuntary nature. Anyone who had seen +him work with the horse could not have helped noticing +that he certainly did not have complete control over the +animal, and was not able, at a given moment, to make +Hans perform a certain feat, as would have been the case<span class="pagenum"><a name="Page_229" id="Page_229"></a>[Pg 229]</span> +if the process had been one of "training". Again and +again Hans failed to make the right count. Before a +large audience, one time, it took four tests to get him to +tap properly up to 20, and in all four I could note clearly +that it was Mr. von Osten who, by his involuntary premature +movements, was the innocent cause of the failure. +On another occasion, after Hans had done some beautiful +work in fractions, in the presence of a large number +of spectators, the master asked him the simple question: +"Where is the numerator in a fraction?"—The answer +was first: "to the left", and then, after a severe reprimand: +"down" (below), and finally: "up" (above). +He often made just such incorrect movements of the head. +In the color-selecting tests the average of error was quite +unpredictable. With an equal number of tests, on one +day, half would be successful, on another, four fifths, on +a third, one-tenth. Often Hans appeared to be "indisposed" +for days at a time. The color tests would often +end in expressions of rage on the part of Mr. von Osten +and in consequence Hans would become startled and +would then storm about the courtyard so that it was dangerous +to try to approach him. Some may object that all +this was mere comedy and that possibly Mr. von Osten +prevented some of the tests from turning out successfully. +But this objection is to be met by the statement that very +often failure would occur just when it was particularly +desirable to have the tests appear in a favorable light +before a large and enthusiastic assemblage of visitors. +After such failures he would be downcast on account of +Hans's contrariness. It is also significant that Mr. von +Osten's percentage of error, corresponds very closely +with my percentage of error in the "non-voluntary" +tests, (<a href="#Page_84">page 84f.</a>), whereas he never was able to obtain<span class="pagenum"><a name="Page_230" id="Page_230"></a>[Pg 230]</span> +the errorless results which I obtained in my "voluntary" +experiments.</p> + +<p>But we must be careful not to confuse non-voluntary +movement and lack of knowledge of the movement. And +again we must distinguish between knowledge of the +grosser and the finer signals. Mr. von Osten was aware +of the grosser movements, and talked quite freely concerning +them, but in so doing, showed that he was quite +unaware of their true function. He undertook to show +us what we already knew—that, when he remained standing +perfectly erect, he could elicit no sort of response +from Hans. Furthermore, that whenever he continued to +bend forward, Hans would always respond incorrectly +and with very high numbers. He knew, also, that Hans +was distracted in his operations every time the questioner +resumed the erect posture while the tapping was in progress. +This he demonstrated to us on one occasion in the +following manner. He said to Hans: "You are to count +to 7; I will stand erect at 5". He repeated the test five +times, and each time Hans stopped tapping when the master +raised his body. Several such tests resulted in the +same way. Mr. von Osten, however, believed this to be a +caprice of the horse and at first declared that he would +yet be able to eliminate it, but later became resigned to it +as an irremediable evil. Mr. von Osten was also aware +that the questioner ought not move while the horse was +approaching a colored cloth, and cautioned me in regard +to it, though I had already noted as much. And finally, he +also knew what influence his calls had while the horse +was selecting the cloth, and he told me that it was of great +assistance to Hans to be admonished frequently, since +thus his attention was brought to bear upon the proper +cloth. Yet, when we requested Mr. von Osten to desist<span class="pagenum"><a name="Page_231" id="Page_231"></a>[Pg 231]</span> +calling, since he was thereby influencing the horse in the +choice of the cloth, he answered: "Why that's just what +I wish to do!"—But though the statement that he was +aware of the nature of these grosser signs is thus seen +to be true, it by no means necessarily implies that he had +purposely trained the animal to respond to them. In +these observations of his he had builded better than he +knew—he evidently had no notion of their scientific significance. +But the same thing might happen to those +who were <a name="tn_png_238"></a><!--TN: "suppossed" changed to "supposed"-->supposed to be somewhat less naïve, as is +shown by the experience of Mr. Schillings, who quite unconsciously, +for many months had been giving not only +the finer, but also the grosser signs, and never guessed +the true nature of affairs until I explained it to him. Nor +was it an easy matter for me to get at the facts involved +in the process, although it now all appears so very simple.</p> + +<p>On the other hand, it is also true that Mr. von Osten +knew nothing whatever of the finer, more minute signals, +such as the final jerk, the head-movement upward, downward, +etc., and it is difficult to conceive how he might +have gained any knowledge of them. We might perhaps +conceive of four possible sources. He might have +come upon them by chance. But it is extremely improbable +that in the million of possible forms of signaling +he should have hit upon those that at the +same time represent the natural expressive movements. +Or he might have derived a knowledge of them through +a study of the pertinent literature. I have searched +diligently for such a source, in both the old and the +modern literature, but in vain. From the sixteenth +century on, there is a series of accounts of horses that +were able to spell and to solve problems in arithmetic, +and the reports on learned dogs go back even to the time<span class="pagenum"><a name="Page_232" id="Page_232"></a>[Pg 232]</span> +of Justinian, in the middle of the sixth century.<a name="refanchor107"></a><a href="#ref_107" class="fnanchor">[107]</a> All +of these animals were kept for purpose of speculation and +were exhibited for pecuniary reasons only. Nor does one +read that any person could work with these animals off-hand, +which was the characteristic feature of the Osten +horse.<a name="FNanchor_AN_40" id="FNanchor_AN_40"></a><a href="#Footnote_AN_40" class="fnanchor">[AN]</a> In many cases we find mention made of the<span class="pagenum"><a name="Page_233" id="Page_233"></a>[Pg 233]</span> +signs to which the animals reacted. Thus for the beginning +or stopping of the animal's scraping or tapping, the +signals were respectively raising and lowering of the eyes +on the part of the trainer,<a name="refanchor113"></a><a href="#ref_113" class="fnanchor">[113]</a> lowering and raising of the +whip<a name="refanchor114"></a><a href="#ref_114" class="fnanchor">[114]</a> or of the arm, stepping forward and backward,<a name="refanchor115"></a><a href="#ref_115" class="fnanchor">[115]</a> +and as a closing signal a slight bending forward.<a name="refanchor116"></a><a href="#ref_116" class="fnanchor">[116]</a> +The signals for beginning and ceasing to bark +in the case of dogs, were the trainer's commands to +"speak", and, at the same time, his looking at the dog, +and then looking away for a closing sign;<a name="refanchor117"></a><a href="#ref_117" class="fnanchor">[117]</a> or a mouth-movement +on the part of the trainer and then a withdrawing +of the left hand which had been resting on the hip.<a name="refanchor118"></a><a href="#ref_118" class="fnanchor">[118]</a> +Among the signals for nodding and shaking the head we +find the following mentioned: raising and lowering the +hand or arm<a name="refanchor119"></a><a href="#ref_119" class="fnanchor">[119]</a> or the whip;<a name="refanchor120"></a><a href="#ref_120" class="fnanchor">[120]</a> a movement of the hand +toward the horse's nose, as a signal for nodding, and an +arm-movement as a signal for shaking the head.<a name="refanchor121"></a><a href="#ref_121" class="fnanchor">[121]</a> For +this last, we find recommended also a slight breathing +upon the animal,<a name="refanchor122"></a><a href="#ref_122" class="fnanchor">[122]</a> and—in the case of dogs—a mouth-movement +simulating blowing, or a turn of the fingers.<a name="refanchor123"></a><a href="#ref_123" class="fnanchor">[123]</a> +(We will not dwell upon the many signals for selecting +objects, which are mentioned, since we have already discussed +this point on <a href="#Page_230">page 230f</a>). In all these instances it +is plain that we have to do with purely voluntary and<span class="pagenum"><a name="Page_234" id="Page_234"></a>[Pg 234]</span> +"artificial" signals. The only example of involuntary +signs which Mr. von Osten could have found in literature, +was that of Huggins's dog, which need not be considered +here, since, as was said on <a href="#Page_177">page 177</a>, the really effective +signs in that case were not discovered. A third means by +which Mr. von Osten might have gained a knowledge of +the involuntary, natural expressive signs, would have +been by observing others. If he had had opportunity of +observing another von Osten and another Hans, he might +have gotten at the secret. But since this was not the +case, this possibility vanishes. A fourth possibility is +self-observation. We would then have to assume that +Mr. von Osten at first really tried to educate the horse +to think, but soon recognized the fruitlessness of such an +attempt. At the same time, he then would have noticed +his own involuntary movements and their effect upon the +horse, and having noted them, voluntarily reduced their +extent and utilized them in the training process. But +here also there is much that militates against this assumption +when we consider how great is the difficulty of consciously +refining movements which at first were rather +coarse, unless it be by the adjustment of the proper degree +of concentration of attention, a subtlety of method +of which we could hardly believed Mr. von Osten capable. +We must remember, also, that in the first publication regarding +Hans which, by the way, marks the beginning +of his career, ("Das lesende und rechnende Pferd," by +Major-General E. Zobel, in the "Weltspiegel" of July 7, +1904), we may read the following: "He (Mr. von Osten) +is always willing to have the horse undergo an examination +on the part of a stranger, and promises that after +Hans has become fairly well acquainted he will display +the same degree of efficiency as he displays with the mas<span class="pagenum"><a name="Page_235" id="Page_235"></a>[Pg 235]</span>ter, +<a name="tn_png_242"></a><!--TN: Double quote added after "himself"-->himself." This occurred at a time when Mr. Schillings, +the man who was destined to prove the truth of +the statement, had not yet appeared on the scene. How +was Mr. von Osten to know beforehand that every questioner, +who might appear, would execute the same movements +that he himself had used? We would recall also +that not one in the great multitude of persons who worked +successfully with the horse in the absence of Mr. von +Osten, had noticed, even in the slightest measure, any of +these movements in themselves. The position and repute +of these persons vouches for their veracity,—among them +were the writer of the article just mentioned, the Count +zu Castell, Count Matuschka, Count von Eickstedt-Peterswaldt, +General Köring, Dr. Sander, Mr. H. Suermondt +and Mr. H. von Tepper-Laski. Some of these +gentlemen were quite unwilling to believe that they executed +such movements. This happened in the case of Mr. +von Tepper-Laski, who had visited Hans ten times and +who had, during the course of these visits, frequently +worked alone with the horse and had received correct responses. +Count Eickstedt, too, although he was one of +those who had been made acquainted with the nature of +the movements involved before being allowed to visit the +horse, was unable to note them either in his observation +of Mr. von Osten, or of himself, when, in compliance with +his own wish, he was left alone with Hans. Nor did any +of the laboratory subjects, some of whom were well trained +in introspection, discover the true nature of affairs. +They were thoroughly astonished when the facts of the +case were explained to them. And I, also, as was mentioned +on <a href="#Page_100">page 100</a>, did not become aware of my own +movements, until I had noted those of Mr. von Osten. +In fine, everything would indicate that we have here not<span class="pagenum"><a name="Page_236" id="Page_236"></a>[Pg 236]</span> +an intention to deceive the public, but a case of pure self-deception.<a name="FNanchor_AO_41" id="FNanchor_AO_41"></a><a href="#Footnote_AO_41" class="fnanchor">[AO]</a></p> + +<p>This self-deception is easily understood when we consider +the two predominent characteristics of the man: the +pedantry of the pedagogue, and his proneness to be possessed +by a single idea, which is a peculiarity of those of +an inventive turn of mind. Adhering closely to a preformed +plan, he carefully and narrowly circumscribed +the scope and order of instruction. He would not go on +to the number 5 if he were not thoroughly convinced that +the 4 had been completely mastered, nor would he go on +to a more difficult problem in multiplication, until he felt +certain that Hans was entirely proficient in the problems +of the simpler sort. If he had ever put a question to +Hans before its regular order, he would have discovered, +to his amazement, that there really existed no difficulties +for Hans, and also that the horse really required no appreciable +time to acquire new material. Mr. von Osten +would have had a like experience if he had asked Hans +concerning the value of Chinese coins or the logarithm +of 1000. However, he never did anything of the kind, +but always adhered closely to his plan. He required the +questioner to say: "2 and 2", and never "2 plus 2". +Nor were capitals or Latin script to be used in the written +material. And if upon request he did so, he did it, +without faith in the result, and hence there was failure.<span class="pagenum"><a name="Page_237" id="Page_237"></a>[Pg 237]</span> +And so he declared that "if you use Latin script Hans +becomes confused and will be out of sorts for several +weeks thereafter." Mr. von Osten is, and ever will remain, +the schoolmaster, and will never become the psychologist, +the "soul-vivisectionist". Who would work a +child with such puzzling questions? and Hans was to him +like a child. Thus the old man believed himself to be a +witness of a continuous, organic development of the +animal soul—a development which in reality had no other +existence than in his own imagination.</p> + +<p>Added to this pedantry was an extraordinary uncritical +attitude of mind, induced by his obsession by one +favorite idea, which blinded him to all objections. He met +objectionable observations on the part of others in one of +two ways. One method was by attributing to Hans certain +remarkable qualities, such as an extraordinary keenness of +hearing and a wonderful power of memory, or again, certain +defects, such as moodiness and stubbornness,—which +as a matter of fact, were only so many back-doors by +which he might escape from the necessity of offering adequate +explanations. When Hans was able to give off-hand +a gentleman's name which he had heard years before, it +was called a case of extraordinary memory. When the +horse insisted that 2 times 2 was 5, he maintained that +it was an example of animal stubbornness. There was +still a simpler method of overcoming inconvenient objections +and that was by ignoring them altogether. The +number 1, the simplest and most fundamental in the +system of numbers, was one of the most difficult for Hans. +(<a href="#Page_67">Page 67f.</a>). Mr. von Osten was aware of this, but +thought little of it. During the very first visit of Professor +Stumpf, Mr. von Osten asked the horse: "By +how much must you increase the numerator of the frac<span class="pagenum"><a name="Page_238" id="Page_238"></a>[Pg 238]</span>tion +7/8, in order to get a whole number?" Hans repeatedly +answered incorrectly and always tapped numbers +that were too great. The same question was then +asked concerning the fraction 5/8, and immediately there +was a correct response, (the favorite number 3). Mr. +von Osten said very naïvely: "In the case of the difference +of 1, he always goes wrong. It was just what I +expected." Mr. von Osten still relates that the distinction +between right and left created far greater difficulty +for Hans than all of the work in fractions, and that even +to-day it is not thoroughly established; also, that the selection +of colored cloths is often a failure still, although +it was one of the first things in which he was given instruction. +It appears never to have dawned upon Mr. +von Osten that the arts in which Hans seemed to excel, +also formed the standing repertoire of so many trained +horses, regarding whom it was well-known that they +owed all of their cleverness to the training given them +by their masters. This fact alone should have induced +him to make some form of critical investigation.</p> + +<p>When Hans suddenly became a celebrity, and he, himself, +the object of an enthusiastic following, the whole +affair evidently took Mr. von Osten off his feet. Strangers +took the further instruction of the horse in charge, +and the rate and degree of Hans's progress became disconcerting. +One day it came to pass that the horse even +understood French, and the old gentleman, whose apostolic +exterior had always exerted a high degree of suggestion +upon his admirers, in turn fell captive to the spell of +retroactive mass-suggestion. He no longer was uneasy +concerning the most glaring kinds of failure. On one +occasion he even insisted upon the completion of a series +of tests in which procedure was "without knowledge",<span class="pagenum"><a name="Page_239" id="Page_239"></a>[Pg 239]</span> +which promised no results whatever. "The animal's stubbornness +must be broken," he commented. On the other +hand, he regarded every criticism as a form of personal +insult. And once he showed a member of the committee +of the Society for the Protection of Animals the door, because +the man, without having looked at his watch, wanted +to show it to Hans and ask him the time. Many other +critics had similar experiences.</p> + +<p>Summarizing the remarks of this chapter, our judgment +must be as follows: It is in the highest degree improbable +that Mr. von Osten purposely trained the horse +to respond to certain cues. It is also improbable that he +knew that in every test he was giving signals, (although +I can form no judgment concerning what happened after +the publication of the latest report). To assume the +contrary would land us in the midst of insoluble contradictions +of the many ascertained facts in the case. The +explanation here essayed, however, should prevent that. +To be sure, we, must then reckon with curious inner +contradictions in Mr. von Osten's character. But such +contradictions are to be found, upon earnest analysis, in +nearly every human character. And Mr. von Osten may +say with the poet: "Ich bin kein ausgeklügelt Buch. +Ich bin ein Mensch mit seinem Widerspruch."</p> + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_AJ_36" id="Footnote_AJ_36"></a><a href="#FNanchor_AJ_36"><span class="label">[AJ]</span></a> The author intends to take up the problem of counting, so-called, on +the part of animals and of the principle involved, in another work soon +to be forthcoming.</p></div> + +<div class="footnote"><p><a name="Footnote_AK_37" id="Footnote_AK_37"></a><a href="#FNanchor_AK_37"><span class="label">[AK]</span></a> There are some who believe they are warranted in concluding the +opposite from the structure of the animal's brain alone. We may say +that the brain of the horse, compared with that of the ape, or even that +of the dog, represents a relatively low type of development. But owing +to the rapid changes in the views, often contradictory, concerning the +nature of the nervous structures and processes underlying the thought +process, any conclusion based on such views would be premature. For +this reason we cannot agree with the French physiologist who was +dissecting the brain of a horse and, struck by its smallness of size, exclaimed: +"When I saw your proud look and beautiful neck, I hesitated +a moment before mounting upon your back. But now that I have seen +how small is your brain, I no longer have any qualm about using you."<a name="refanchor98"></a><a href="#ref_98" class="fnanchor">[98]</a></p></div> + +<div class="footnote"><p><a name="Footnote_AL_38" id="Footnote_AL_38"></a><a href="#FNanchor_AL_38"><span class="label">[AL]</span></a> This natural and close connection between the process of attention +and the movement toward the object attended to is clearly expressed in +our English and French terms, derived from the Latin "tendere ad—," +to reach toward—.</p></div> + +<div class="footnote"><p><a name="Footnote_AM_39" id="Footnote_AM_39"></a><a href="#FNanchor_AM_39"><span class="label">[AM]</span></a> G. Franzius,<a name="refanchor99"></a><a href="#ref_99" class="fnanchor">[99]</a> privy counselor of the admiralty, master of the dry-dock +at Kiel, is responsible for the undeserved revival of the ancient +belief, long buried by science, that the divining branch is put into motion +solely as the result of the influence of hidden springs or treasures, and +without any agency in the person who is holding it. The untenability of +this theory comes home to us most forcibly when we recall how various +are the kinds of things which have been discovered by means of the +branch. First there is gold and water, which are the only ones mentioned +by Mr. Franzius. The water can be thus discovered only when +it flows below ground, say that which is passing through the mains of a +city, whereas the water of the Rhine or the Elbe would have no effect +on the branch. Besides gold, every other kind of metal has been supposedly +located by the branch,—as well as coal, gypsum, ochre, red-chalk +sulphur and petroleum,—according to the desire of the one searching. +Thus, the very same branch that just a moment ago was influenced by +the least bit of underground water, may remain unaffected by the presence +of a large body of water, if in the meantime I have changed my plan +and decide to search for coal or for gold. But that is not all. The +branch will point out a murderer or the place where a murder has been +committed, it will discover the thief or his trail, as well as the things +stolen or merely touched by him. It will indicate where the boundary-stone +that has been moved, ought to stand. The branch further discloses +the sins of the persons concerning whom it is consulted, as well +as their talents and abilities, the journeys they have made and the wounds +they have received. It will indicate whether or not a person has money +and how much. It can announce what absent persons are doing and +what apparel they are wearing, and of what color it is. It will give information +on theological, medical, zoological, and botanical questions. +In fine, no matter what the question, it will never fail of an answer.<a name="refanchor100"></a><a href="#ref_100" class="fnanchor">[100,</a> <a name="refanchor101"></a><a href="#ref_101" class="fnanchor">101]</a> +</p><p> +The impossibility of explaining the phenomena in a purely physical +way was recognized at a very early date. For a long time the activity +of the users of the divining rod seems to have been restricted to the +search for metals. The first (or one of the first) to raise his voice +against it was the learned G. Agricola<a name="refanchor102"></a><a href="#ref_102" class="fnanchor">[102]</a> (1556), and after him there +were many who all wrote more or less independently of one another. +Aside from swindle and chance, it was usually believed that sorcery of +the agency of Beelzebub was involved, and for that reason the Church +has repeatedly forbidden the use of the divining-rod. But even in the +17th century we find some who believed that it was imagination alone +that moved the person's hand, and with it the rod,<a name="refanchor103"></a><a href="#ref_103" class="fnanchor">[103,</a> <a name="refanchor104"></a><a href="#ref_104" class="fnanchor">104]</a> ("fortassis +etiam phantasia manum in motum concitante"); and that points out +the essentials of the solution of the phenomenon, and we will not go +into the matter here in detail. A number of complex psychological +problems arising in connection with it are still waiting to be solved, but +this much appears certain; the staff or branch plays no other part in the +whole process than that which is served by the three levers in the tests +described in <a href="#CHAPTER_IV">Chapter IV</a> (<a href="#Page_116">pages 116 ff.</a>),—they simply magnify the expressive +movements of the diviner. And so we can understand why +the instruments serving as rod might be so varied. Hay-forks, pickets, +clock-springs and pendulums, scissors and pliers have been used. A +knife and fork or two pipes, fastened together, an open book, and even +a sausage, grasped at both ends and thus bent together somewhat,—all +have served the purpose equally well. We can understand, too, how +some adepts are able to achieve the same degree of success—for they +do succeed beyond a doubt—without any rod whatever, but simply by +placing the index fingers end to end and bending them somewhat, and +even by merely groping about with hands outstretched or folded before +them.<a name="refanchor106"></a><a href="#ref_106" class="fnanchor">[106]</a></p></div> + +<div class="footnote"><p><a name="Footnote_AN_40" id="Footnote_AN_40"></a><a href="#FNanchor_AN_40"><span class="label">[AN]</span></a> There is only one, and I believe it is only a seeming exception +to be found in the literature on the subject. We are told that +about the year 1840 a French revenue official named Léonard had two +hunting dogs that, besides other things, were able to play at dominoes, +and this not only with their master, but with anyone and without the +master's assistance. The owner had educated them simply for the fun +of it, and not for pecuniary gain. This statement is made by both +writers who, apparently independently of one another, have discussed +the case, Youatt<a name="refanchor108"></a><a href="#ref_108" class="fnanchor">[108]</a> and de Tarade.<a name="refanchor109"></a><a href="#ref_109" class="fnanchor">[109]</a> De Tarade himself played +with them, and gives directions how to teach dogs to play the game. +But his exposition is so naïve, and even ridiculous, for those who know +anything about the subject, that we do not believe it necessary to attempt +a detailed refutation. Youatt never saw the animals. But he +tells us that not only the dog's partner, but also the master, sat at the +game. Youatt's assertion, however, that "not the slightest intimation +could have been given by Mr. Leonard to the dog," but that the animal +carried on the game by means of its own observation and calculation, +appears to me a rather bold statement. After my own experience with +dogs, I firmly believe this to have been impossible. Hachet-Souplet,<a name="refanchor110"></a><a href="#ref_110" class="fnanchor">[110]</a> +who shares my conviction, explains the matter as follows: the dog +would simply place a domino having the number of eyes named by his +partner, thus the 6 adjacent to the 6, the 3 to the 3, etc. But even so +a great deal would have to be attributed to the dog, (although in that +case real counting would by no means be absolutely necessary, for an +association between the number term and the total picture of the corresponding +group of eyes would suffice.) But we must note that neither +of the writers mentions that the numbers were always called aloud by +the partner. After the failure of the experiments of Sir John Lubbock,<a name="refanchor111"></a><a href="#ref_111" class="fnanchor">[111]</a> +we must doubt very much if a dog is able to match one domino +with another having the same number of eyes. We are therefore inclined +to believe that this dog continually received signs from its master. +These signs probably were visual, perhaps also auditory, and they were +by no means involuntary. For in a book on the training of animals, +which Léonard, the owner of the dogs, has published, and in which he +describes minutely the method by which they had been trained in their +various accomplishments, he does not mention with so much as a syllable +the game of dominoes, a thing which he certainly would have +dwelt upon, if he had believed in the animals' power of independent +thought. He would not have remained silent concerning this greatest—though +only apparent—achievement of his educational endeavors. +But his whole book is evidence that he was too wise to have thus deceived +himself, and our only alternative is to believe that he was playing +a joke on his credulous admirers.</p></div> + +<div class="footnote"><p><a name="Footnote_AO_41" id="Footnote_AO_41"></a><a href="#FNanchor_AO_41"><span class="label">[AO]</span></a> P. Wasmann, S. J. in the third edition of his book, "Instinkt und +Intelligenz im Tierreich" (Freiburg, Herder, 1905), discusses the case +of Hans and quotes from a letter I wrote him concerning the matter. +In the quotation an error has crept in, which I would here correct. +The statement is ascribed to me that "Hans differs from other horses +only in his extraordinary power of observation, an unintentional by-product +of intentional training," whereas in my letter I said: "unintentional +by-product of intentional education."</p></div> +</div> + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_240" id="Page_240"></a>[Pg 240]</span> +<h2><a name="CONCLUSION" id="CONCLUSION"></a>CONCLUSION</h2> + + +<p><span class="firstwords">If</span> we would make a brief summary of the status of Mr. +von Osten's horse in the light of these investigations and +try to understand what is the bearing upon the question +of animal psychology in general, we may make the following +statements.</p> + +<p>Hans's accomplishments are founded first upon a one-sided +development of the power of perceiving the slightest +movements of the questioner, secondly upon the intense +and continued, but equally one-sided, power of attention, +and lastly upon a rather limited memory, by +means of which the animal is able to associate perceptions +of movement with a small number of movements of its +own which have become thoroughly habitual.</p> + +<p>The horse's ability to perceive movements greatly exceeds +that of the average man. This superiority is probably +due to a different constitution of the retina, and perhaps +also of the brain.</p> + +<p>Only a <a name="tn_png_247"></a><!--TN: "diminshingly" changed to "diminishingly"-->diminishingly small number of auditory stimuli +are involved.</p> + +<p>All conclusions with regard to the presence of emotional +reactions, such as stubbornness, etc., have been +shown to be without warrant. With regard to the emotional +life we are justified in concluding from the behavior +of the horse, that the desire for food is the only +effective spring to action.</p> + +<p>The gradual formation of the associations mentioned +above, between the perception of movement and the +movements of the horse himself, is in all probability not<span class="pagenum"><a name="Page_241" id="Page_241"></a>[Pg 241]</span> +to be regarded as the result of a training-process, but as +an unintentional by-product of an unsuccessful attempt +at real education, which, though in no sense a training-process, +still produced results equivalent to those of such +a process.</p> + +<p>All higher psychic processes which find expression in +the horse's behavior, are those of the questioner. His +relationship to the horse is brought about almost wholly +by involuntary movements of the most minute kind. The +interrelation existing between ideas having a high degree +of affective coloring and the musculature of the +body, (which is brought to light in this process), is by +no means a novel fact for us. Nevertheless, it is possible +that this case may be of no small value, on account of the +great difficulties which are usually met in the attempt to +establish experimentally the more delicate details in this +field.</p> + +<p>And, returning to the considerations of the <a href="#CHAPTER_I">first chapter</a>, +if we ask what contributions does this case make +toward a solution of the problem of animal consciousness, +we may state the following: The proof which was expected +by so many, that animals possess the power of +thought, was not furnished by Hans. He has served to +weaken, rather than strengthen, the position of these enthusiasts. +But we must generalize this negative conclusion +of ours with care,—for Hans cannot without further +qualification be regarded as normal. Hans is a domesticated +animal. It is possible (though the opposite is +usually assumed), that our animals have suffered in the +development of their mental life, as a result of the process +of domestication. To be sure, in some respects they +have become more specialized than their wild kin, (e. g., +our hunting dogs), and in their habits they have become<span class="pagenum"><a name="Page_242" id="Page_242"></a>[Pg 242]</span> +adapted largely to suit our needs. This latter is shown +by all the anecdotes concerning "clever" dogs, horses, +etc. But with the loss of their freedom they have also +gradually been deprived of the urgent need of self-preservation +and of the preservation of their species, and thus +lack one of the greatest forces that make for psychic +development. And often their artificial selection and +culture has been with a view to the development of muscle +and sinew, fat and wool, all at the expense of brain development.<a name="FNanchor_AP_42" id="FNanchor_AP_42"></a><a href="#Footnote_AP_42" class="fnanchor">[AP]</a> +Our horses are, as a rule, sentenced to an +especially dull mode of life. Chained in stalls (and usually +dark stalls at that,) during three-fourths of their +lives, and more than any other domestic animal, enslaved +for thousands of years by reins and whip, they have +become estranged from their natural impulses, and owing +to continued confinement they may perhaps have suffered +even in their sensory life. A gregarious animal, yet kept +constantly in isolation, intended by nature to range over +vast areas, yet confined to his narrow courtyard, and deprived +of opportunity for sexual activity,—he has been +forced by a process of education to develop along lines +quite opposite to his native characteristics. Nevertheless, +I believe that it is very doubtful if it would have +been possible by other methods, even, to call forth in the +horse the ability to think. Presumably, however, it +might be possible, under conditions and with methods of +instruction more in accord with the life-needs of the +horse, to awaken in a fuller measure those mental activities +which would be called into play to meet those needs.</p><span class="pagenum"><a name="Page_243" id="Page_243"></a>[Pg 243]</span> + +<p>Though our investigations do not give support to the +fantastic <a name="tn_png_250"></a><!--TN: "acounts" changed to "accounts"-->accounts of animal intelligence given by Brehms, +they by no means warrant a return to Descartes and his +theory of the animal-machine (as is advocated by a number +of over-critical investigators). We cannot deny the +validity of conclusions from analogy without denying at +the same time the possibility of an animal psychology—indeed +of all psychology. And all such conclusions indicate +that the lower forms possess the power of sense-perception, +that they, like us, presumably have at their +disposal certain images, and that their psychic life is to a +large extent also constituted of mere image-associations, +and that they too, learn by experience. Also that they +are susceptible to feelings of pleasure and of pain and +also to emotions, as jealousy, fear, etc., though these +may be only of the kind which have a direct relation to +their life-needs. We are in no position to deny <i>a priori</i> +the possibility of traces of conceptual thought in those +forms nearest man in the scale—whether living in their +natural manner or under artificial conditions. And even +less so since the final word has not yet been spoken regarding +the nature of conceptual thinking itself. All that +is certain is that nothing of the kind has been proven to +occur in the lower forms, and that as yet not even a +suitable method of discovering its existence has been +suggested. But the community of those elementary +processes of mental life which we have mentioned above +is in itself enough to connect the life of the lower forms +with ours, and imposes upon us the duty of regarding +them not as objects for exploitation and mistreatment, +but as worthy of rational care and affection.</p> + +<div class="footnotes"><h3>FOOTNOTES:</h3> +<div class="footnote"><p><a name="Footnote_AP_42" id="Footnote_AP_42"></a><a href="#FNanchor_AP_42"><span class="label">[AP]</span></a> Buffon,<a name="refanchor124"></a><a href="#ref_124" class="fnanchor">[124]</a> the great naturalist, expresses himself not less pessimistically +in his own brilliant manner: "Un animal domestique est un +esclave dont on s'amuse, dont on se sert, dont on abuse, qu'on altère, +qu'on dépaïse et que l'on dénature."</p></div> +</div> + +<span class="pagenum"><a name="Page_244" id="Page_244"></a>[Pg 244]</span> + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_245" id="Page_245"></a>[Pg 245]</span> +<h1><a name="SUPPLEMENTS" id="SUPPLEMENTS"></a>SUPPLEMENTS</h1> + + + +<hr style="width: 10%;"> +<h2 style="padding-bottom:1em;"><a name="SUPPLEMENT_I" id="SUPPLEMENT_I"></a>SUPPLEMENT I</h2> + +<h2 style="padding-bottom:.25em;">MR. VON OSTEN'S METHOD OF INSTRUCTION</h2> + +<p class="chapterhead2 smcap">[By C. Stumpf]</p> + + +<p><span class="firstwords">The</span> following is a report of the account, which Mr. +von Osten gave Professor Schumann and me, of the +method which he had used in the instruction of the horse, +and which was illustrated by actual demonstrations. I +cannot testify, of course, that Mr. von Osten really did +adhere to this method throughout the four years in which +he tutored the horse, but I will say that I have several +good reasons for believing that it was impossible for him +to have trumped up this make-believe scheme afterward, +merely to mislead us. Among the reasons are the following: +He was always ready to give a detailed explanation +of any question which we might interpose; the +written statements of Major von Keller, who has known +Mr. von Osten for a period of fifteen years; the testimony +of General Zobel, who became acquainted with the +whole process fully a year before any public exhibitions +were given; the accounts given by the tenants in +Mr. von Osten's house, who for years saw the process of +instruction going on in the courtyard of the apartment +building,—according to their account his intercourse with<span class="pagenum"><a name="Page_246" id="Page_246"></a>[Pg 246]</span> +the horse was like that with a child at school,—he made +much use of the apparatus and never did they notice anything +like an habituation to respond to certain signals; +and finally the appearance of the apparatus itself—some +of which could not be bought at second hand—was most +convincing.</p> + +<p>The apparatus used for the work in arithmetic consisted +mainly of a set of large wooden pins, a set of smaller +ones (such as are to be had in toy-shops), a counting-machine, +such as is commonly used in the schools, a chart +upon which were pasted the numbers from 1 to 100, and +finally the digits, cut large and in brass and suspended +from a string. For the work in reading Mr. von Osten +used the chart shown in the frontispiece of this book. +Here we have the letters of the alphabet in small German +script with numbers written below which serve to indicate +the row, and what place in that row, the letters +occupy. For tones, a small, child's organ was used with +the diatonic scale C^1 to C^2, and for instruction in colors, +a number of colored cloths were used.</p> + +<p>The work in arithmetic began by placing a single +wooden pin in front of Hans and then commanding him: +"Raise the foot!—One!" Here we must assume that +the horse had learned to respond to the command to raise +the foot during the preceding period, when tapping in +general had been taught. In order to get the horse to +learn that he was to give only one tap, Mr. von Osten +tried to control the tapping by means of holding the animal's +foot, just as a teacher tries to aid a pupil in learning +to write by guiding his hand. He repeated this exercise +so often that finally the single tap was made. And always +the right foot was insisted upon. Bread and carrots +were the constant rewards.</p><span class="pagenum"><a name="Page_247" id="Page_247"></a>[Pg 247]</span> + +<p>Two of the pins were now set up and the command +given: "Raise the foot!—One, two!" Mr. von Osten +again aided the establishment of the proper association by +using his hand as before. At the same time the two pins +were pointed out, and the order was always without exception +from left to right. Gradually it became unnecessary +to touch the foot or to point to the pins, and instead +the question was introduced: "How many are there?", in +order that the horse should become accustomed to these +words as an invitation to give the taps when he saw the +wooden pins before him.</p> + +<p>Then three pins were taken and the words "one, two, +three" were spoken, and so on. In naming a number +the preceding ones were always named along with it, in +order that the normal order might thus be learned at the +same time. Later the number alone, without the preceding +ones, sufficed to elicit the proper number of taps. +The last word of the series thus becomes characteristic +of the series as a whole. It differs from all the others, +and thus becomes the sign for the whole series of numbers +thus named, each of which arises as a memory image +at the proper place in the series and is accompanied by a +tap of the foot. Thus, Mr. von Osten at any rate had +accounted to himself for his success.</p> + +<p>But Hans was not to acquire merely this relatively mechanical +process of counting (hardly to be called counting), +but he was to acquire also some meaning content +for the number terms. For this purpose everything depended +upon the concept "and". Only he who can grasp +its meaning will be able to understand a number. 2 is +1 <i>and</i> 1, 3 is 2 <i>and</i> 1. Mr. von Osten had someone hold +a large cloth before the horse, where the wooden pins +usually were placed. He then had the cloth taken up and<span class="pagenum"><a name="Page_248" id="Page_248"></a>[Pg 248]</span> +he would pronounce emphatically the word "and". +After this had been done a number of times, he put up two +of the pins and obscured them by the cloth. The cloth +was again raised and the word "and" pronounced. Then +Hans, as a result of his previous instruction (so Mr. von +Osten thought) would give two taps at sight of the pins. +The thing was repeated with three pins, then with one, +and so on, and the horse would always execute the proper +number of taps.</p> + +<p>Now, five pins were set up, the three to the right being +covered by the cloth. The horse tapped twice and Mr. +von Osten said "two". Then the cloth was raised, Hans +gave three further taps, and Mr. von Osten said "and +three" with emphasis.</p> + +<p>In this simple manner he tried to get the horse to understand +that the three belongs to the two, and that both +together make five. The image of the five pins as it was +known from previous experience, was to be associated +with the combined groups of two and three, and conversely, +it was to be reproduced when these groups were +presented. Later the cloth and pins were omitted and the +question was asked: "How much is two and three?". +The horse tapped five times. It had learned how to add. +Still this could be regarded only as a mechanical process, +if the horse were able to add only those numbers which +had been presented together one or more times in the +manner just described. And so long as we remained +within the first decade, we could get twenty-five binary +combinations whose sum does not exceed 10 (counting +inverted orders we would have forty-five binary permutations),—all +of which might have been practised separately. +But as a matter of fact, Mr. von Osten did not +take this course, for as he himself says, he allowed Hans<span class="pagenum"><a name="Page_249" id="Page_249"></a>[Pg 249]</span> +to discover a great deal for himself. "Hans had to develop +the multiplication table for himself."—With larger +numbers and more addends, the number of combinations +becomes so great that there can be no doubt they were +not practised separately.</p> + +<p>Since, after all this preliminary instruction, Hans +really began to give solutions of new problems, the master +believed that this was proof that he had succeeded in inculcating +the inner meaning of the number concepts, and +not merely an external association of memory images +with certain movement responses. But he always remained +within the sphere of the ideas thus developed, +and adhered closely to the customary vocabulary and its +usage. Every new concept, each additional word was +explained anew.</p> + +<p>It would not be legitimate to condemn the whole procedure +from the very beginning on the ground of the +horse's lack of knowledge of language or of its use. It +was Mr. von Osten's aim to convey to the horse an understanding +of the language, by means of sense-presentations, +adequate to give rise to the proper sense-perceptions. +Helen Keller and other blind deaf-mutes have +been educated to an understanding of the language without +the aid of vision and hearing. They have come to it +through the sense of touch alone. Everything depends +upon whether or not the predisposition for it is present. +And it was quite rational that Mr. von Osten should +have chosen counting and arithmetical calculation as the +processes by which to make his attack upon the animal +mind, for as a matter of fact, nowhere else is it so easy +to bridge the gap between perception and conception and +nowhere else can the sign of success or failure be perceived +so readily as in the handling of numbers. It is<span class="pagenum"><a name="Page_250" id="Page_250"></a>[Pg 250]</span> +unfortunate, however, that he did not utilize these same +signs for purposes of counter-testing also, as, for instance, +by inquiring for the cube root of 729. But he was +prevented from doing this by his close adherence to his +pedagogical principle and by his unquestioning faith in +the soundness of the entire procedure.</p> + +<p>In teaching multiplication the counting machine was +used. Two of the ten balls on one of the rods were +pushed far to the left, thus: 00. "How many are +there?" Two taps. "Very well. That is once two." +Another group of two was pushed to the left, at a short +interval from the first group, thus: 00 00. "How many +times two balls are there?" was asked, with a decided +movement of the hand toward the two groups. Two +taps. "How many, therefore, are two times two?" +Four taps.</p> + +<p>The horse was supposed to learn the meaning of the +word "times" by means of the spatial separation of the +groups; he was to be taught to notice and to count the +groups, and also the number of units in a single group. +Three times two then meant three groups with two units +in each group. The horse was supposedly aided by the +following factors: the relative nearness of the units belonging +to one group, as over against the space interval +between the groups themselves; also that the groups +were pointed out as wholes in connection with the emphatic +enunciation of the words <a name="tn_png_257"></a><!--TN: Single quote moved from before "twice," to after it-->'once, twice,' etc.; +and finally the touching and raising of the horse's foot +by means of the hand until all the desired associations of +the ideas with one another and with the corresponding +tapping movements were quite perfect.</p> + +<p>Subtraction was taught in the following manner. Five +pins were set up; the horse tapped five times. Mr. von<span class="pagenum"><a name="Page_251" id="Page_251"></a>[Pg 251]</span> +Osten then removed two of them and said emphatically: +"I take away,—minus. <a name="tn_png_258"></a><!--TN: Double quote removed from before "How"-->How many are still standing?" +The horse tapped three times. Here, too, there +was at first some assistance by means of the hand to get +the tapping.</p> + +<p>In division four balls were first pushed to the left end +of the rod, thus: 0000. "How many balls are there to +the left?" Four taps. They were now divided into two +pairs, thus: 00 00. Pointing to the units of one group, +the teacher asks: "There are always how many in the +group?" Two taps. Three groups were formed, thus: +00 00 00. "There are now how many balls to the left?" +Six taps. "And there are always how many in each +group?", (pointing at them). Two taps. "And how +often is two contained in six?", (pointing to the groups +consecutively). Three taps, etc.</p> + +<p>The ideas of 'part', of 'whole', and of 'being contained' +were illustrated by means of a chalk line which +was interrupted in one or more places by erasure.</p> + +<p>In all these operations Mr. von Osten adhered strictly +to the rule, and required others to do so too, that the number +upon which the operation was performed, must be +mentioned first. Thus, one was not to say, "take 3 away +from 7", but "from 7 take away 3." Otherwise, he believed, +Hans would become easily confused. Also one +was not allowed to say "to multiply", but to "take" a +certain number so many "times". He, himself, never +departed from this practice.</p> + +<p>We will not go into the details of the method by which +Hans was taught the meaning of the number signs, of the +signs of operation, of the numbers above 10, or the significance +of "digits", "tens", etc. Only this,—when in +problems in addition the sum was greater than 10, the 10<span class="pagenum"><a name="Page_252" id="Page_252"></a>[Pg 252]</span> +was first tapped and then the remainder of the number +added to the 10. Thus: "You are to add 9 and 5. How +much must you add to the 9 to have 10?" One tap. +"But now, you were to add not merely 1, but 5; how +much have you still to add to the 10?"—Four taps. In +like manner, whenever the addends were below 20 or 30 +and the sum above 20 or 30, Mr. von Osten would ask +for the 20 or 30 taps first. He thought that he was thus +giving his pupil an ever firmer grasp upon the principle +of the structure of our number system, in which all higher +numbers are constituted of tens and digits. For the +same reason he used at first, instead of the words 'eleven' +and 'twelve' ('elf' and 'zwölf' in the German), expressions +which in English might be rendered as 'one-teen' +and 'two-teen' ('einzehn' and 'zweizehn' in the +German); and only later, after the animal had seemingly +mastered the meaning in question, did Mr. von Osten replace +them by the usual forms.</p> + +<p>All this was beautifully conceived and might perhaps +form the basis for the instruction of primitive races. +But it is of immediate interest for us only because it +enables us to better understand the origin of the conviction +under which Mr. von Osten and his followers +labored.</p> + + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_253" id="Page_253"></a>[Pg 253]</span> +<h2 style="padding-bottom:1em;"><a name="SUPPLEMENT_II" id="SUPPLEMENT_II"></a>SUPPLEMENT II</h2> + +<h2 style="padding-bottom:1em;">THE REPORT OF SEPTEMBER 12, 1904</h2> + + +<p><span class="firstwords">"The</span> undersigned came together for the purpose of +investigating the question whether or not there is involved +in the feats of the horse of Mr. von Osten anything +of the nature of tricks, that is, intentional influence +or aid, on the part of the questioner. After a careful +investigation they are unanimously agreed that such +signs are out of the question under the conditions which +were maintained during this investigation. This decision +in no wise takes into account the character of the men +exhibiting the horse, and who are known to most of the +undersigned: In spite of the most attentive observation, +nothing in the way of movements or other forms of expression +which might have served as a sign, could be discovered. +In order to obviate involuntary movements on +the part of those present, one series of tests was made +with only Mr. Busch present. Among these tests were +some in which, according to his professional judgment, +the possibility of tricks of the sort commonly used in +training, was excluded. Another series of tests was made +in such a way that the correct answers to the questions +which Mr. von Osten put to the horse, were unknown to +the questioner. From previous observation the greater +number of the undersigned also know of a large number +of cases in which, during the absence of Mr. von Osten +and Mr. Schillings, other persons were likewise able to +obtain correct responses from the horse. Among these<span class="pagenum"><a name="Page_254" id="Page_254"></a>[Pg 254]</span> +were some cases in which the questioner did not know +the correct solution of the problem or was mistaken about +it. And lastly, several of the undersigned have become +acquainted with the method which Mr. von Osten used, +which has little in common with methods of training, and +is patterned after the instruction given in the elementary +schools. As a result of these observations the undersigned +are of the opinion that unintentional signs of the +kind which are at present familiar, are likewise excluded. +They are unanimously agreed that this much is certain: +This is a case which appears in principle to differ from +any hitherto discovered, and has nothing in common with +training, in the usual sense of that word, and therefore +is worthy of a serious and incisive investigation.</p> + +<p style="margin-left:2.25em;"><span class="smcap">Berlin</span>, September 12, 1904.</p> + + +<p class="signing"><span class="smcap">Paul Busch</span>, Circus-manager.</p> +<p class="signing"><span class="smcap">Otto, Count zu Castell-Rüdenhausen</span>.</p> +<p class="signing"><span class="smcap">Dr. A. Grabow</span>, member of the schoolboard, retired.</p> +<p class="signing"><span class="smcap">Robert Hahn</span>, Teacher, Municipal schools.</p> +<p class="signing"><span class="smcap">Dr. Ludwig Heck</span>, Director of the Zoölogical Garden.</p> +<p class="signing"><span class="smcap">Dr. Oscar Heinroth</span>, Assistant in the Berlin Zoölogical Garden.</p> +<p class="signing"><span class="smcap">Dr. Richard Kandt</span>.</p> +<p class="signing"><span class="smcap">Major F. W. von Keller</span>, retired.</p> +<p class="signing"><span class="smcap">Major-General Th. Köring</span>, retired.</p> +<p class="signing"><span class="smcap">Dr. Miessner</span>, Assistant in the Royal Veterinary College.</p> +<p class="signing"><span class="smcap">Prof. Nagel</span>, Head of the department of sense-physiology in the Physiological Institute of the University of Berlin.</p> +<p class="signing"><span class="smcap">Prof. C. Stumpf</span>, Director of the Psychological Institute, Member of the Academy of Sciences.</p> +<p class="signing"><span class="smcap">Henry Suermondt</span>."</p> + + + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_255" id="Page_255"></a>[Pg 255]</span> +<h2 style="padding-bottom:1em;"><a name="SUPPLEMENT_III" id="SUPPLEMENT_III"></a>SUPPLEMENT III</h2> + +<h2 style="padding-bottom:1em;">AN ABSTRACT FROM THE RECORDS OF THE +SEPTEMBER-COMMISSION<a name="FNanchor_AQ_43" id="FNanchor_AQ_43"></a><a href="#Footnote_AQ_43" class="fnanchor">[AQ]</a></h2> + + +<p><span class="firstwords">The</span> important meetings occurred on the 11th and +12th of September and both of them extended over four +hours. The greatest difficulty was occasioned by the condition +laid down by Mr. von Osten: that we were to work +without him from the very beginning. In a certain sense +this condition had been met once before when Mr. +Schillings appeared upon the scene, a man whose fairness +ought to be doubted by none. He came utterly +skeptical, and yet in the course of a week he learned +to handle the horse and received responses regularly. +However, since the public had begun to doubt Mr. +Schillings also, another person had to attempt the rôle +of questioner. Count zu Castell tried to do this and +practised for some days before the meetings, but his +success—although of no small moment—was not great +enough to be convincing.</p> + +<p>In apprising Mr. von Osten of this fact we caused a +veritable catastrophe. He declared in a most decisive +manner that he would have to insist upon the condition<span class="pagenum"><a name="Page_256" id="Page_256"></a>[Pg 256]</span> +he had imposed, since the public demanded it, and he +could never assist in any tests, until he had been cleared +of the suspicion of having descended to the use of tricks. +If it should take weeks to accustom the horse to a new +questioner, there would be no alternative but to wait +that length of time.</p> + +<p>A happy circumstance helped us out of our difficulty. +We had chanced in our discussion to mention the experience +of Dr. Miessner, a member of the commission, +who on the day before had gone to witness an exhibition +of the mare "Clever Rosa", and who believed that +he had succeeded in discovering the tricks involved. +There was a sudden change in Mr. von Osten's attitude. +He expressed his willingness to undergo the most stringent +examination and agreed to anything in the way of +conditions of control, challenging even the proven ability +of Dr. Miessner. "I have neither whip nor rod, as had +the man in the exhibition, and agree to any precautionary +measures you may care to take."</p> + +<p>After he had gone, the commission decided to ask him +to have the horse perform one of the more common, +simple, feats. They were going to watch him very +closely. Different members were assigned the task of +attending to different parts of his body (head, eyes, right +hand, left hand, etc.) while Mr. Busch, since he was the +most proficient in the detection of tricks, was to regard +the total behavior of the man.</p> + +<p>The exhibitions included the indication of the day of +the week by means of taps, the day just past, the day +ahead, its date, arithmetical problems, and the counting +of rings strung upon a rod. Messrs. Grabow and Hahn +interpolated a few tests themselves, in which they did the +questioning. All tests were successful.</p><span class="pagenum"><a name="Page_257" id="Page_257"></a>[Pg 257]</span> + +<p>Mr. von Osten withdrew, and in comparison of notes +which followed, Mr. Busch, as well as all the others, +declared that they had discovered nothing of the nature +of a visible sign. Mr. Busch said that he had also kept +an eye on the spectators and had noticed nothing there. +Nevertheless, he desired to see Mr. von Osten go through +one series with no one else but himself (Busch) present.</p> + +<p>This was done, and on this occasion a number of tests +were made in the recognition of colored cloths. The +horse was required to indicate, by tapping, the place in +the series which the cloth occupied and was then asked +to bring the green or the red, as the case might be, in +his mouth. Furthermore, he was asked to approach that +one of the five gentlemen standing at a distance, whose +photograph had been shown him. Then he was requested +to spell the words "Rat" and "Busch" according to the +method which he had been taught. Nearly all of these +tests were likewise successful.</p> + +<p>In the conference which followed, Mr. Busch again +declared that he had noticed no trace of a sign; he maintained +that, in the selecting of colored cloths (especially +when they were placed so closely together) and in the +approach toward a person, there was no possibility whatever +that some trick was being used.</p> + +<p>During the session of September 12th, Mr. von Osten +agreed to two sets of experiments.</p> + +<p>1. Another man was to put the question to the horse. +Mr. von Osten himself was to stand, back to back to the +questioner and to bend forward, so that he was effectually +hidden from the horse's view, yet could, by means of +occasional calls, make his presence known to the animal. +The assumption was that it would be conducive to success +if the horse knew that the master was present and<span class="pagenum"><a name="Page_258" id="Page_258"></a>[Pg 258]</span> +was awaiting the answer, and yet at the same time the +possibility of receiving a sign was obviated.</p> + +<p>2. Another man in Mr. von Osten's absence was to +ask the horse to tap a certain number. Then the questioner +was to leave, and Mr. von Osten, returning, was +to ask the horse to perform some arithmetical process +with the number which was thus unknown to the master. +Mr. von Osten said that he thought that this method was +somewhat risky, since the horse would be aware that he, +Mr. von Osten, did not know the number, and might +therefore be in a humor to play some prank.</p> + +<p>The questions of the first sort were answered with +but very few errors. Mr. Hahn and Count zu Castell +asked simple questions in arithmetic. When Mr. von +Osten withdrew into the stable, the count put several +other problems, among them the counting of persons +and of windows, all of which were solved correctly.</p> + +<p>Between the first and second series of tests the following +experiments were interpolated. The names of six +members of the commission were written upon six slates +respectively, which were then suspended from a string. +Mr. von Osten pointed to one of the men and asked: +"On which of the slates is this gentleman's name to be +<a name="tn_png_265"></a><!--TN: Period removed after "found?"-->found?" The correct number was tapped in every case. +The command to approach the slate in question was also +obeyed as a rule, although this was not as uniformly successful +as tapping.</p> + +<p>In the conference which followed, Mr. Busch declared +that the feats appeared inconceivable to him; and again +none of the men had noted anything in the way of signs.</p> + +<p>Now followed the second series of tests mentioned +above. In order to be sure to get the correct responses, +Mr. Schillings, who up to this point had not been present<span class="pagenum"><a name="Page_259" id="Page_259"></a>[Pg 259]</span> +at any of the experiments, was asked to put the questions +to the horse. Mr. von Osten went into the house, accompanied +by a member of the commission. And again, Mr. +Schillings would go out before the second part of the +test, without having met Mr. von Osten.</p> + +<p>Five tests were made in this way. They were not +attended by such amazing success as were the preceding +ones, but nevertheless the results were surprising. The +horse nearly always repeated the number itself, instead +of performing the operation required. Since, however, +Mr. Schillings, owing to a misunderstanding, had, in the +first two cases, said to the horse: "You are to repeat +this number for Mr. von Osten", the errors might appear +to be a result of this request.</p> + +<p>At the final discussion, the result of which was the +unanimous declaration which was given for publication, +not only the data obtained during these two sessions, but +also the earlier experiences of some of the members of +the commission were taken into consideration. None of +the tests witnessed could be referred to chance or to the +use of tricks. Count zu Castell pointed out that in the +course of eight days he had elicited forty correct +responses from the horse, among them some in regard +to which he himself had been momentarily in error. +Other members recalled the many instances in previous +exhibitions, during which both Mr. Schillings and Mr. +von Osten were absent, when questions were put to the +horse by others. The commission also had access to a +detailed account written by Professor Stumpf on Mr. +von Osten's method of instruction, based on the explanations +and demonstrations which Mr. von Osten +had himself given. As a result of these considerations +the commission felt under obligations to give public<span class="pagenum"><a name="Page_260" id="Page_260"></a>[Pg 260]</span> +expression to its conviction. In the report it limited +itself, however, to the purely negative side—principally +in denying the use of tricks,—and expressed no opinion +with regard to the actual genesis of the horse's accomplishments, +since it believed that there was great possibility +that other factors were involved which ought to be +carefully investigated.</p> + +<div class="footnotes"> +<div class="footnote"><p><a name="Footnote_AQ_43" id="Footnote_AQ_43"></a><a href="#FNanchor_AQ_43"><span class="label">[AQ]</span></a> A few days after the 12th of September I made the present abstract +from the original records <a name="tn_png_268"></a><!--TN: "af" changed to "of"-->of the Commission, which I have here abbreviated +somewhat. (See <a href="#Page_8">page 8</a>). Referring once more to the misunderstanding +mentioned on <a href="#Page_3">page 3</a>, I would say that the closing sentence +of the report is here re-given literally as it then appeared. C. St.</p></div> +</div> + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_261" id="Page_261"></a>[Pg 261]</span> +<h2 style="padding-bottom:1em;"><a name="SUPPLEMENT_IV" id="SUPPLEMENT_IV"></a>SUPPLEMENT IV</h2> + +<h2 style="padding-bottom:1em;">THE REPORT OF DECEMBER 9<span class="smcap">TH</span>, 1904</h2> + + +<p><span class="firstwords">Together</span> with Dr. E. von Hornbostel and Mr. O. +Pfungst, I have tried during the past few weeks to find +an explanation of the accomplishments of the horse +'Hans' by the experimental method. We had access +to the horse in the absence of the master and groom. +The results are as follows:</p> + +<p>The horse failed in his responses whenever the solution +of the problem that was given him was unknown to any +of those present. For instance, when a written number +or the objects to be counted were placed before the +horse, but were invisible to everyone else, and especially +to the questioner, he failed to respond properly. Therefore +he can neither count, nor read, nor solve problems +in arithmetic.</p> + +<p>The horse failed again whenever he was prevented by +means of sufficiently large blinders from seeing the persons, +and especially the questioner, to whom the solution +was known. He therefore required some sort of visual +aid.</p> + +<p>These aids need not, however,—and this is the peculiarly +interesting feature in the case,—be given intentionally. +The proof for this is found in the fact that in +the absence of Mr. von Osten the horse gave correct +replies to a large number of persons; and to be more +specific, Mr. Schillings and later Mr. Pfungst, after<span class="pagenum"><a name="Page_262" id="Page_262"></a>[Pg 262]</span> +working with the horse for a short time, regularly received +correct answers, without their being in any way +conscious of having given any kind of signal.</p> + +<p>So far as I can see, the following explanation is the +only one that will comport with these facts. The horse +must have learned, in the course of the long period of +problem-solving, to attend ever more closely, while +tapping, to the slight changes in bodily posture with +which the master unconsciously accompanied the steps +in his own thought-processes, and to use these as closing +signals. The motive for this direction and straining of +attention was the regular reward in the form of carrots +and bread, which attended it. This unexpected kind of +independent activity and the certainty and precision of +the perception of minimal movements thus attained, are +astounding in the highest degree.</p> + +<p>The movements which call forth the horse's reaction, +are so extremely slight in the case of Mr. von Osten, that +it is easily comprehensible how it was possible that they +should escape the notice even of practised observers. +Mr. Pfungst, however, whose previous laboratory experience +had made him keen in the perception of visual +stimuli of slightest duration and extent, succeeded in +recognizing in Mr. von Osten the different kinds of +movements which were the basis of the various accomplishments +of the horse. Furthermore, he succeeded in +controlling his own movements, (of which he had +hitherto been unconscious), in the presence of the horse, +and finally became so proficient that he could replace +these unintentional movements by intentional ones. He +can now call forth at will all the various reactions +of the horse by making the proper kind of voluntary +movements, without asking the relevant question or<span class="pagenum"><a name="Page_263" id="Page_263"></a>[Pg 263]</span> +giving any sort of command. But Mr. Pfungst meets +with the same success when he does not attend to +the movements to be made, but rather focuses, as +intently as possible, upon the number desired, since +in that case the necessary movement occurs whether he +wills it or not. In the near future he will give a special +detailed report of his observations, which gives promise +of becoming a valuable contribution to the study of involuntary +movements. Also he will give an account of +our tests and of the mechanism of the various accomplishments +of the horse. We must also defer, till then, the +disproof of certain seemingly relevant arguments in favor +of the horse's power of independent thought.</p> + +<p>Some defenders of the view which maintains the +horse's rationality may urge that it was only through +our experiments that the animal became trained and +spoiled in so far as the ability to think is concerned. +They are refuted in this, however, by the fact that the +horse still continues to solve problems involving decimal +fractions and to determine calendar dates for Mr. von +Osten, as brilliantly as ever, as is shown by his recent +demonstration before a large group of spectators. That +these results are now being achieved in a manner essentially +different from formerly is nothing but a bare assertion.</p> + +<p>On the other hand, now that the possibility has been +established that these wonderful results may be obtained +in all their complexity by means of intentional signs, +many will question whether Mr. <a name="tn_png_270"></a><!--TN: "Von" changed to "von"-->von Osten did not +himself train the horse from the very beginning to +respond to these signs. No one has the right, however, +to charge an old man, who has never had a blemish +on his reputation, with having invented a most refined<span class="pagenum"><a name="Page_264" id="Page_264"></a>[Pg 264]</span> +network of lies, if the facts can be explained in a satisfactory +manner in some other rational way. And this +can be done in this case. For we have seen that there +is another alternative, other than the theory that the +horse can think or the assumption that tricks have been +employed.</p> + +<p>And now, aside from the specific results obtained, +what is the scientific and philosophic import of the whole +affair?—For one thing, the revolution in our conception +of the animal mind, which had been hoped for by some, +and feared by others, has not taken place. But a conclusion +of an opposite character is justified. If such unexampled +patience and high pedagogical excellence as +was daily brought to bear by Mr. von Osten during the +course of four long years, could not bring to light the +slightest trace of conceptual thinking, then the old assertion +of the philosophers that the lower forms are incapable +of such thinking, finds corroboration in the results of +these experiments so far as the animal scale up to and including +the ungulates is concerned. For this reason the +tremendous effort put forth by Mr. von Osten, is not, +in spite of the self-deception under which he labors, lost +to science. If anyone has the courage to try the experiment +with the dog or the ape, the insight which we have +now gained will enable him to beware of one source of +error which hitherto has not been noticed.</p> + +<p>In the face of much misapprehension which has arisen, +I wish once more to say emphatically that the committee +of September 12th in no wise declared itself to be convinced +that the horse had the power of rational thinking. +The committee restricted itself entirely to the question +whether or not tricks were involved, and, intentionally +and rightly referred the positive investigation to a purely<span class="pagenum"><a name="Page_265" id="Page_265"></a>[Pg 265]</span> +scientific court. I would also report that for some time +Mr. Schillings has been convinced, by his own observations, +of the horse's lack of reason, and when he was +apprised of our conclusion in the matter, he embraced it +without wavering. I have no intention of taking part +in any discussion which may arise in the press as a result +of the present report. Unless they wish to confine themselves +to mere guesswork, the defenders of other views +will not shrink from the task of basing their criticism +upon careful methodical experimentation, and they will +keep a detailed record of their results day by day; for +statements based solely upon memory, without specific +report of experimental conditions, prove nothing.</p> + +<p style="text-align:right;margin-right:.75em;"><span class="smcap">Prof. Carl Stumpf</span>.</p> + +<p style="text-align:left;margin-left:.75em;">December 9th, 1904.</p><span class="pagenum"><a name="Page_266" id="Page_266"></a>[Pg 266]</span> + + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_267" id="Page_267"></a>[Pg 267]</span> +<h2><a name="TABLE_OF_REFERENCES" id="TABLE_OF_REFERENCES"></a>TABLE OF REFERENCES</h2> +<hr style="width: 10%;"> + +<p class="center">(The names of the authors of anonymous works are placed in parenthesis.)</p> + +<table border="0" width="90%" cellpadding="2" cellspacing="2" summary="Contents" align="center"> + + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_1"></a><a href="#refanchor1" class="reflabel">1.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Zell, Th.</span> Das rechnende Pferd. Ein Gutachten über den +"Klugen Hans" auf Grund eigener Beobachtungen. Berlin, +R. Dietze, 1904.</div></td> +</tr> + + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_2"></a><a href="#refanchor2" class="reflabel">2.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Freund, F.</span> Der "kluge" Hans? Ein Beitrag zur Aufklärung. +Berlin, Boll and Pickardt, 1904.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_3"></a><a href="#refanchor3" class="reflabel">3.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Hansen, F. C. C.</span> and A. Lehmann. Über unwillkürliches +Flüstern. Philosophische Studien, edited by W. Wundt, +Leipsic, 1895, Vol. 11, pp. 471 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_4"></a><a href="#refanchor4" class="reflabel">4.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Sanden, S. v.</span> Über Aktivität und Passivität des Reiters und +seiner Hülfen. Deutsche hippologische Presse, Berlin, 1896, +Jahrg. 12, No. 11, pp. 117 ff. and No. 12, pp. 128 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_5"></a><a href="#refanchor5" class="reflabel">5.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Weyer, E. M.</span> Some Experiments on the Reaction-Time of +a Dog. Studies from the Yale Psychological Laboratory, +New Haven, Conn., 1895, Vol. 3, pp. 96 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_6"></a><a href="#refanchor6" class="reflabel">6.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Dodge, R.</span> Die motorischen Wortvorstellungen. Halle a. S., M. +Niemeyer, 1896, pp. 40 and 77.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_7"></a><a href="#refanchor7" class="reflabel">7.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Darwin, Chas.</span> The Expression of the Emotions in Man and +Animals. New York, D. Appleton & Co., 1873, PP. 273 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_8"></a><a href="#refanchor8" class="reflabel">8.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Wundt, W.</span> Völkerpsychologie. Leipsic, W. Engelmann, 1900, +Vol. 1, Part I, pp. 175 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_9"></a><a href="#refanchor9" class="reflabel">9.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Lieber, F.</span> On the Vocal Sounds of Laura Bridgeman. Smithsonian +Contributions to Knowledge, Washington, 1851, Vol. +2, Art 2, pp. 11 f. (Laura wrote her name: Bridgman.)</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_10"></a><a href="#refanchor10" class="reflabel">10.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Garner, R. L.</span> The Speech of Monkeys. New York, Chas. +Webster & Co., 1892, pp. 57 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_11"></a><a href="#refanchor11" class="reflabel">11.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Féré, Chas.</span> Sensation et mouvement. Paris, F. Alcan, 1887, +pp. 102 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_12"></a><a href="#refanchor12" class="reflabel">12.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">James, W.</span> The Principles of Psychology. New York, Henry +Holt & Co., 1890, Vol. 2, pp. 372 and 381.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_13"></a><a href="#refanchor13" class="reflabel">13.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Beard, G. M.</span> The History of Muscle-Reading. Journal of +Science, and Annals of Astronomy, Biology, Geology, etc., +London, 1881, Series 3, Vol. 3, p. 558 f.</div><span class="pagenum"><a name="Page_268" id="Page_268"></a>[Pg 268]</span></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_14"></a><a href="#refanchor14" class="reflabel">14.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Laurent, L.</span> Les procédés des liseurs de pensées. Journal de +psychologie normale et pathologique, Paris, 1905, second +year, No. 6, pp. 489 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_15"></a><a href="#refanchor15" class="reflabel">15.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Guicciardi, G.</span> e <span class="smcap">G. C. Ferrari.</span> Il lettore del pensiero "John +Dalton." Rivista sperimentale di Freniatria ecc., Reggio +nell' Emilia, 1898, Vol. 24, p. 209.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_16"></a><a href="#refanchor16" class="reflabel">16.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Tarchanoff, J.</span> de. Hypnotisme, suggestion et lecture de pensées. +Translated from the Russian by E. Jaubert, second +edition. Paris, G. Masson, 1893, pp. 153 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_17"></a><a href="#refanchor17" class="reflabel">17.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Preyer, W.</span> Telepathie und Geisterseherei in England. Deutsche +Rundschau, Berlin, 1886, Jahrg. 12, Heft 4, p. 40.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_18"></a><a href="#refanchor18" class="reflabel">18.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Sommer, R.</span> Dreidimensionale Analyse von Ausdrucksbewegungen. +Zeitschrift für Psychologie und Physiologie der +Sinnesorgane, Leipsic, 1898, Vol. 16, pp. 280 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_19"></a><a href="#refanchor19" class="reflabel">19.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Frenkel, H.</span> Des secousses rhythmiques de la tête chez les +aortiques et chez les personnes saines. Revue de Médecine, +Paris, 1902, 22nd Year, No. 7, pp. 617 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_20"></a><a href="#refanchor20" class="reflabel">20.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Zoneff, P.</span> and <span class="smcap">E. Meumann</span>. Über Begleiterscheinungen +psychischer Vorgänge in Atem und Puls. Philosophische +Studien, edited by W. Wundt, Leipsic, 1903, vol. 18, p. 3.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_21"></a><a href="#refanchor21" class="reflabel">21.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Müller, G. E.</span> and <span class="smcap">A. Pilzecker</span>. Experimentelle Beiträge zur +Lehre vom Gedächtniss. Zeitschrift fur Psychologie und +Physiologie der Sinnesorgane, Leipsic, 1900, Ergänzungsband +1, pp. 58 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_22"></a><a href="#refanchor22" class="reflabel">22.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Kraepelin, E.</span> Der psychologische Versuch in der Psychiatrie. +Psychologische Arbeiten, edited by the same, Leipsic, 1895, +Vol. 1, pp. 50 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_23"></a><a href="#refanchor23" class="reflabel">23.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Amberg, E.</span> Über den Einfluss von Arbeitspausen auf die +geistige Leistungsfähigkeit. Ditto, pp. 374 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_24"></a><a href="#refanchor24" class="reflabel">24.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Shaler, N. S.</span> Domesticated animals. London, Smith Elder & +Co., 1896, pp. 143 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_25"></a><a href="#refanchor25" class="reflabel">25.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Coupin, H.</span> L'esprit des animaux domestiques. La Revue, +Paris, 1903, first quarter, Vol. 44, p. 586.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_26"></a><a href="#refanchor26" class="reflabel">26.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs">(<span class="smcap">Lebrun, P.</span>). Lettres qui découvrent l'illusion des philosophes +sur la baguette, et qui détruisent leurs systèmes. Paris, J. +Boudot, 1696, pp. 239 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_27"></a><a href="#refanchor27" class="reflabel">27.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs">Notice sur un nouvel instrument, dont Mr. Ritter, membre de +l'académie de Munich s'est servi dans les expériences qu'il a +récemment faites avec Mr. Campetti etc. Bibliothèque +Brittannique, Sciences et Arts, Geneva, 1807, Vol. 35, +p. 91.</div><span class="pagenum"><a name="Page_269" id="Page_269"></a>[Pg 269]</span></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_28"></a><a href="#refanchor28" class="reflabel">28.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Zell, Th.</span> Tierfabeln und andere Irrtümer in der Tierkunde. +2nd edition. Stuttgart, Kosmos (1905), p. 38.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_29"></a><a href="#refanchor29" class="reflabel">29.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Thorndike, E. L.</span> Animal Intelligence. Psychological Review, +Lancaster, Pa. and New York, 1898, Monograph Supplements, +Vol. 2, No. 4, p. 95.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_30"></a><a href="#refanchor30" class="reflabel">30.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Vaschide, N.</span> et <span class="smcap">P. Rousseau</span>. Études expérimentales sur la +vie mentale des animaux. Revue scientifique, Paris, 1903, +Series 4, Vol. 19, No. 25, p. 782.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_31"></a><a href="#refanchor31" class="reflabel">31.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Ettlinger, M.</span> Sind die Tiere vernünftig? Hochland, Munich +and Kempten, 1904, Jahrg, 2, Heft 2, p. 223.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_32"></a><a href="#refanchor32" class="reflabel">32.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Romanes, G. J.</span> On the Mental Faculties of the Bald Chimpanzee +(Anthropopithecus calvus). Proceedings of the Scientific +Meetings of the Zoological Society of London, 1889, pp. +320 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_33"></a><a href="#refanchor33" class="reflabel">33.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Kinnaman, A. J.</span> Mental Life of two Macacus rhesus Monkeys +in Captivity. American Journal of Psychology, Worcester, +Mass., 1902, Vol. 13, No. 1, pp. 139 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_34"></a><a href="#refanchor34" class="reflabel">34.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Himstedt, Fr.</span> and <span class="smcap">W. A. Nagel</span>. Versuche über die Reizwirkung +verschiedener Strahlenarten auf Menschen- und +Tier-augen. Festschrift der Albrecht-Ludwigs-Universität +in Freiburg zum 50 jährigen Regierungs-Jubiläum Sr. Konigl. +Hoheit des Groszherzogs Friedrich. Freiburg i. Br., C. A. +Wagner, 1902, pp. 272 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_35"></a><a href="#refanchor35" class="reflabel">35.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Dahl, F.</span> Naturwissenschaftliche Wochenschrift, Jena, 1905, +New series, Vol. 4, No. 48, pp. 767 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_36"></a><a href="#refanchor36" class="reflabel">36.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Corte, Claudio.</span> Il cavallerizzo. Di nuove dall'auttore stesso +corretto ed emendato. Venice, G. Ziletti, 1573, Book 1 +Chap. 6, page 8. (I did not have access to the first edition +of 1562, cf. Graesse, Trésor de livres rares, 1861, Vol. 2, p. +277.)</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_37"></a><a href="#refanchor37" class="reflabel">37.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Riegel.</span> Untersuchungen über die Ametropie der Pferde. +Monatshefte für praktische Tierheilkunde, Stuttgart, 1904, +Bd. 16, Heft 1, pp. 31 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_38"></a><a href="#refanchor38" class="reflabel">38.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Berlin, R.</span> Über die Schätzung der Entfernungen bei Tieren. +Zeitschrift für vergleichende Augenheilkunde, Wiesbaden, +1891, Bd. 7, Heft 1, pp. 5 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_39"></a><a href="#refanchor39" class="reflabel">39.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">The same.</span> Über ablenkenden Linsen-Astigmatismus und seinen +Einfluss auf das Empfinden von Bewegung. Ditto, 1887, Bd. +5, Heft 1, pp. 7 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_40"></a><a href="#refanchor40" class="reflabel">40.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Schleich, G.</span> Das Sehvermögen der höheren Tiere. Tübingen, +F. Pietzcker, 1896, p. 24.</div><span class="pagenum"><a name="Page_270" id="Page_270"></a>[Pg 270]</span></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_41"></a><a href="#refanchor41" class="reflabel">41.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Königshöfer.</span> Über das Äugen des Wildes. Monatshefte des +Allgemeinen Deutschen Jagdschutz-Vereins, Berlin, 1898, +Jahrg. 3, No. 17, pp. 250 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_42"></a><a href="#refanchor42" class="reflabel">42.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Zürn, J.</span> Vergleichend histologische Untersuchungen über die +Retina und die Area centralis retinæ der Haussäugetiere. +Archiv fur Anatomie und Physiologie, Anatomische Abteilung, +Leipsic, 1902, Supplementary volume, pp. 116 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_43"></a><a href="#refanchor43" class="reflabel">43.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Hirschberg, J.</span> Zur vergleichenden Ophthalmoskopie. Archiv +fur Anatomie und Physiologie, Physiologische Abteilung, +Leipsic, Jahrg. 1882, p. 96.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_44"></a><a href="#refanchor44" class="reflabel">44.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Berlin, R.</span>, see 39, p. 4.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_45"></a><a href="#refanchor45" class="reflabel">45.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">The same.</span> Über den physikalisch-optischen Bau des Pferdeauges. +Zeitschrift fur vergleichende Augenheilkunde, Leipsic, 1882, +Jahrg. 1, Heft 1, p. 32.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_46"></a><a href="#refanchor46" class="reflabel">46.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Bayer, J.</span> Tierärztliche Augenheilkunde. Vol. 5 of the "Handbuch +der Tierärztlichen Chirurgie und Geburtshilfe" by J. +Bayer und E. Fröhner. Vienna und Leipsic, W. Braumüller, +1900, p. 459.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_47"></a><a href="#refanchor47" class="reflabel">47.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">The same.</span> Ditto, p. 475.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_48"></a><a href="#refanchor48" class="reflabel">48.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Riegel</span>, see 37, p. 35.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_48a"></a><a href="#refanchor48a" class="reflabel">48a.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Schwendimann, F.</span> Untersuchungen über den Zustand der +Augen bei scheuen Pferden. Archiv für wissentschaftliche und +praktische Tierheilkunde, Berlin, 1903, Bd. 29, Heft 6, p. 566.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_48b"></a><a href="#refanchor48b" class="reflabel">48b.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Berlin, R.</span> Refraktion und Refraktionsanomalien von Tieraugen. +Tageblatt der 52. Versammulung deutscher Naturforscher +und Ärzte in Baden-Baden, 1879, p. 348. See also 45, pp. 28 f. +and 39, p. 13.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_49"></a><a href="#refanchor49" class="reflabel">49.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">The same</span>, see 39, p. 9.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_50"></a><a href="#refanchor50" class="reflabel">50.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Bayer, J.</span>, see 46, pp. 460 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_51"></a><a href="#refanchor51" class="reflabel">51.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Zürn, J.</span>, see 42, p. 114.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_52"></a><a href="#refanchor52" class="reflabel">52.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Chievitz, J. H.</span> Über das Vorkommen der Area centralis retinæ +in den vier höheren Wirbeltierklassen. Archiv für Anatomie +und Physiologie, Anatomische Abteilung, Leipsic, 1891, Heft +4-6. p. 329.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_53"></a><a href="#refanchor53" class="reflabel">53.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Zürn, J.</span>, see 42, p. 140.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_54"></a><a href="#refanchor54" class="reflabel">54.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Königshöfer</span>, see 41, pp. 251 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_55"></a><a href="#refanchor55" class="reflabel">55.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Tennecker, S. v.</span> Bemerkungen und Erfahrungen über den +Charakter und das Temperament, sowie über die geistigen +Eigenschaften des Pferdes überhaupt. Beiträge zur Natur- und +Heilkunde, von Friedreich und Hesselbach, Würzburg, +1825, Vol. 1, pp. 110 f.</div><span class="pagenum"><a name="Page_271" id="Page_271"></a>[Pg 271]</span></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_56"></a><a href="#refanchor56" class="reflabel">56.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Zborzill, E.</span> Die mnemonische Dressur des Hundes. Berlin, +S. Mode (1865), p. 21.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_57"></a><a href="#refanchor57" class="reflabel">57.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Müller, Ad.</span> und K. Tiere der Heimat. 3rd Edition, Cassel, +Th. Fischer, 1897, Book 1, p. 70.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_58"></a><a href="#refanchor58" class="reflabel">58.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Hutchinson, W. N.</span> Dog Breaking. 6th Edition, London, J. +Murray, 1876, pp. 105 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_59"></a><a href="#refanchor59" class="reflabel">59.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Huggins, Lady M.</span> Kepler: a Biography. Cited by Sir J. +Lubbock, On the Senses, Instincts, and Intelligence of +Animals. London, Kegan Paul, Trench and Co., 1888, +pp. 284 f. (The original was published privately and never +put on the market. Hence it was not accessible for +me.)</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_60"></a><a href="#refanchor60" class="reflabel">60.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Lubbock, Sir J.</span> Ditto, p. 285.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_61"></a><a href="#refanchor61" class="reflabel">61.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Rouhet, G.</span> L'entraînement complet et expérimental de l'homme +avec étude sur la voix articulée, suivi de recherches physiologiques +et pratiques sur le cheval. Paris, Libraires associés, +and Bordeaux, Feret et fils, 1902, pp. 517 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_62"></a><a href="#refanchor62" class="reflabel">62.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Lipps, Th.</span> Zur Psychologie der Suggestion. Leipsic, J. A. +Barth, 1897, pp. 5 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_63"></a><a href="#refanchor63" class="reflabel">63.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Zell, Th.</span> See 1, pp. 40 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_64"></a><a href="#refanchor64" class="reflabel">64.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Zborzill, E.</span> See 56, p. 23.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_65"></a><a href="#refanchor65" class="reflabel">65.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Beard, G. M.</span> Physiology of Mind-Reading. Popular Science +Monthly, New York, February 1877. Vol. 10, p. 472. +Reprint in the Journal of Science, and Annals of Astronomy, +Biology, Geology, etc., London, 1881, Series 3, Vol. 3, p. 418.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_66"></a><a href="#refanchor66" class="reflabel">66.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Babinet.</span> Les tables tournantes au point de vue de la mécanique +et de la physiologie. Revue des deux mondes, Paris, 1854, +Twenty-fourth year, Vol. 5, pp. 409 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_67"></a><a href="#refanchor67" class="reflabel">67.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Tolstoi, L. N.</span> Anna Karenina.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_68"></a><a href="#refanchor68" class="reflabel">68.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Goldbeck.</span> Besitzen die Tiere, speziell Hunde, Verstand oder +nicht? Deutsche tierärztliche Wochenschrift, Hannover, +1902, Jahrg. 10, No. 20, p. 202.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_69"></a><a href="#refanchor69" class="reflabel">69.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Menault, E.</span> L'intelligence des animaux. 4th Edition, Paris, +Hachette et Cie., 1872, p. 233.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_70"></a><a href="#refanchor70" class="reflabel">70.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">LeBon, G.</span> L'equitation actuelle et ses principes. 3rd Edition, +Paris, Firmin-Didot et Cie., 1895, pp. 120 and 288.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_71"></a><a href="#refanchor71" class="reflabel">71.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Loiset, B.</span> Praktischer Unterricht in Kunstdarstellungen mit +Pferden. New edition. Stuttgart, Schickhardt u. Ebner, +1884, pp. 69 f. and 98 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_72"></a><a href="#refanchor72" class="reflabel">72.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Baucher, F.</span> Dictionnaire raisonné d'équitation. 2nd Edition, +Paris, chez l'auteur, 1851, pp. 291 ff.</div><span class="pagenum"><a name="Page_272" id="Page_272"></a>[Pg 272]</span></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_73"></a><a href="#refanchor73" class="reflabel">73.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Arnim, v.</span> Praktische Anleitung zur Bearbeitung des Pferdes an +der Longe. 2nd Edition, Leipsic, Zuckschwerdt und Co., +1896, pp. 18 f. and 39 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_74"></a><a href="#refanchor74" class="reflabel">74.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Meehan, J.</span> The Berlin "Thinking" Horse. Nature, London. +1904, Vol. 70, No. 1825, p. 602.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_75"></a><a href="#refanchor75" class="reflabel">75.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Spohr.</span> Die Logik in der Reitkunst. Part 2. Pamphlet No. 32 +in the Series: "Unsere Pferde." Stuttgart, Schickhardt +und Ebner, 1904, p. 29 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_76"></a><a href="#refanchor76" class="reflabel">76.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Redding, T. B.</span> The Intelligence of a Horse. Science, New +York, 1892, Vol. 20, No. 500, pp. 133 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_77"></a><a href="#refanchor77" class="reflabel">77.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Spohr.</span> Die naturgemäsze Gesundheitspflege der Pferde. 4th +Edition, Hannover, Schmorl u. v. Seefeld Nachf., 1904, +p. 164.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_78"></a><a href="#refanchor78" class="reflabel">78.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Decroix, E.</span> Projet de langage phonétique universel pour la +conduite des animaux. Bulletin de la Société nationale +d'Acclimatation de France, Paris, 1898, Forty-fourth Year, +pp. 241 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_79"></a><a href="#refanchor79" class="reflabel">79.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Noizet, Général.</span> Etudes philosophiques. Paris, H. Plon, +1864, Vol. 1, pp. 471 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_80"></a><a href="#refanchor80" class="reflabel">80.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Beard, G. M.</span> See 65, Vol. 10, p. 471.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_81"></a><a href="#refanchor81" class="reflabel">81.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">LeBon, G.</span> See 70, p. 120.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_82"></a><a href="#refanchor82" class="reflabel">82.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Flügel, O.</span> Das Seelenleben der Tiere. 3rd Edition, Langensalza, +H. Beyer und Söhne, 1897, pp. 50 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_83"></a><a href="#refanchor83" class="reflabel">83.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Landois, H.</span> Über das musikalische Gehör der Pferde. Zeitshrift +für Veterinärkunde, Berlin, 1889, Jahrg. 1, No. 6. +pp. 237 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_84"></a><a href="#refanchor84" class="reflabel">84.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Foveau de Courmelles.</span> Les facultés mentales des animaux, +Paris, J. B. Baillière et fils, 1890, p. 142.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_85"></a><a href="#refanchor85" class="reflabel">85.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Zürn, F. A.</span> Die intellektuellen Eigenschaften (Geist und Seele) +der Pferde. Pamphlet 8 of the Series: "Unsere Pferde." +<a name="tn_png_279"></a><!--TN: Period removed after "Stuttgart"-->Stuttgart, Schickhardt und Ebner, 1899, p. 26.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_86"></a><a href="#refanchor86" class="reflabel">86.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Fillis, J.</span> Tagebuch der Dressur. Translated from the French +by J. Halperson and G. Goebel. Stuttgart, Schickhardt und +Ebner, 1906, pp. 322 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_87"></a><a href="#refanchor87" class="reflabel">87.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Athenaeus.</span> Dipnosophistæ. Book 12, 520 c. Edited by G. +Kaibel. Leipsic, B. G. Teubner, 1890, Vol. 3, pp. 148 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_88"></a><a href="#refanchor88" class="reflabel">88.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Aelianus, Cl.</span> De natura animalium. Book 16, 23. Edited by +R. Hercher. Leipsic, B. G. Teubner, 1864, Vol. 1, p. 401.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_89"></a><a href="#refanchor89" class="reflabel">89.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Julius Africanus</span>, S. Κεστοἱ, chapter 14. In: Veterum +Mathematicorum Opera. Paris, Typographia Regia, 1693, +P. 293.</div><span class="pagenum"><a name="Page_273" id="Page_273"></a>[Pg 273]</span></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_90"></a><a href="#refanchor90" class="reflabel">90.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Guénon, A.</span> Influence de la musique sur les animaux et en particulier +sur le cheval. (Châlons-sur-Marne), 1898, pp. 83 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_91"></a><a href="#refanchor91" class="reflabel">91.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Lépinay.</span> L'hypnotisme chez le cheval. Revue de l'hypnotisme, +Paris, 1903, Eighteenth Year, No. 5, pp. 152 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_92"></a><a href="#refanchor92" class="reflabel">92.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Fillis, J.</span> Grundsätze der Dressur und Reitkunst. Translated +from the French by G. Goebel. 3rd Edition, Stuttgart, +Schickhardt und Ebner, 1905, pp. 10 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_93"></a><a href="#refanchor93" class="reflabel">93.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Manouvrier, L.</span> Mouvements divers et sueur palmaire consécutifs +à des images mentales. Revue philosophique, Paris, +1886, Vol. 22, pp. 204 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_94"></a><a href="#refanchor94" class="reflabel">94.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Gasparin, Cte A. de.</span> Des tables tournantes, du surnaturel en +général et des esprits. 2nd Edition, Paris, E. Dentu, 1855, +Vol. 1, Part 1.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_95"></a><a href="#refanchor95" class="reflabel">95.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Rivers, W. H. R.</span> and <span class="smcap">E. Kraepelin</span>. Über Ermüdung and +Erholung. Psychologische Arbeiten, edited by E. Kraepelin, +Leipsic, 1895, Vol. 1, pp. 636f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_96"></a><a href="#refanchor96" class="reflabel">96.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs">(<span class="smcap">Carpenter, W. B.</span>). Spiritualism and its Recent Converts. +Quarterly Review, London, 1871, Vol. 131, No. 262, p. 312.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_97"></a><a href="#refanchor97" class="reflabel">97.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Darwin, Chas.</span> See 7, p. 48.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_98"></a><a href="#refanchor98" class="reflabel">98.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Saint-Ange, de.</span> Cours d'hippologie. 2nd Edition, Paris, chez +Dumaine et chez Leneveu and Saumur, chez Mlle. Niverlet +et chez Mlle. Dubosse, 1854, Vol. 1, p. 101.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_99"></a><a href="#refanchor99" class="reflabel">99.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Franzius, G.</span> Die Wünschelrute. Zentralblatt der Bauverwaltung, +Berlin, 1905, Jahrg. 25, No. 74, pp. 461 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_100"></a><a href="#refanchor100" class="reflabel">100.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Ménestrier, Cl. Fr.</span> La philosophie des images énigmatiques. +Lyon, J. Guerrier, 1694, pp. 483 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_101"></a><a href="#refanchor101" class="reflabel">101.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs">(<span class="smcap">Lebrun, P.</span>). Histoire critique des pratiques superstitieuses, +qui ont séduit les peuples et embarassé les sçavans. Paris +(et Amsterdam), 1702, p. 42.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_102"></a><a href="#refanchor102" class="reflabel">102.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Agricola, G.</span> De re metallica libri XII, eiusdem de animantibus +subterraneis liber. Basel, Froben, 1556, Book 2, pp. 27 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_103"></a><a href="#refanchor103" class="reflabel">103.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Schott, C.</span> Magia universalis naturæ et artis. Würzburg, J. G. +Schönwetters Erben, 1659, Part 4, Book 4, p. 430.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_104"></a><a href="#refanchor104" class="reflabel">104.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">The same.</span> Physica curiosa, sive mirabilia naturae et artis. +Würzburg, 1662, Part 2, Book 12, p. 1532.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_105"></a><span class="reflabel">105.</span></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Zeidler, J. G.</span> Pantomysterium, oder das Neue vom Jahre in +der Wünschelruthe, etc. Hall in Magdeburg (Halle a. S.), +Renger, 1700, Chap. 2. p. 47.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_106"></a><a href="#refanchor106" class="reflabel">106.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Barrett, W. F.</span> On the so-called Divining Rod, or Virgula +Divina. Proceedings of the Society for Psychical Research, +London, 1897, Vol. 13, pp. 177 f.</div><span class="pagenum"><a name="Page_274" id="Page_274"></a>[Pg 274]</span></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_107"></a><a href="#refanchor107" class="reflabel">107.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Theophanes.</span> Chronographia. Paris, Typographia Regia, 1655, +pp. 189 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_108"></a><a href="#refanchor108" class="reflabel">108.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Youatt, W.</span> The Dog. London, Ch. Knight and Co., 1845, +pp. 108 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_109"></a><a href="#refanchor109" class="reflabel">109.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Tarade, E. de.</span> Traité de l'élevage et de l'éducation du chien. +Paris, E. Lacroix (1866), pp. 113 ff.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_110"></a><a href="#refanchor110" class="reflabel">110.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Hachet-Souplet, P.</span> Die Dressur der Tiere. Translated from +the French by O. Marschall v. Bieberstein, Leipsic, O. Klemm, +1898, pp. 36 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_111"></a><a href="#refanchor111" class="reflabel">111.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Lubbock, Sir J.</span> See 59, pp. 280 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_112"></a><span class="reflabel">112.</span></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Léonard, A.</span> Essai sur l'éducation des animaux, le chien pris +pour type. Lille, Leleux, 1842, pp. 81-185.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_113"></a><a href="#refanchor113" class="reflabel">113.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Meehan, J.</span> See 74, p. 602.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_114"></a><a href="#refanchor114" class="reflabel">114.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Franconi</span> (<span class="smcap">Gärtner</span>). Die Dressur der Kunstpferde. Jahrbuch +fur Pferdezucht, Pferdekenntnis, Pferdehandel usw. auf das +Jahr 1835, Weimar und Ilmenau, 1835, Jahrg. 11, p. 329.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_115"></a><a href="#refanchor115" class="reflabel">115.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Loiset, B.</span> See 71, p. 130.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_116"></a><a href="#refanchor116" class="reflabel">116.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Hachet-Souplet, P.</span> See 110, p. 91.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_117"></a><a href="#refanchor117" class="reflabel">117.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Knickenberg, F.</span> Der Hund und sein "Verstand." Cöthen +(Anhalt), P. Schettlers Erben, 1905, pp. 129 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_118"></a><a href="#refanchor118" class="reflabel">118.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Lang, R.</span> Geheimnisse zur künstlichen Abrichtung der Hunde, +revised edition. Augsburg and Leipsic, A. Bäumer, pp. 46 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_119"></a><a href="#refanchor119" class="reflabel">119.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Franconi</span> (<span class="smcap">Gärtner</span>). See 114, pp. 326 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_120"></a><a href="#refanchor120" class="reflabel">120.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Tennecker, S. v.</span> Erinnerungen aus meinem Leben. Altona, +I. F. Hammerich, 1838, Vol. 1, pp. 21 f. (The name of the +author is erroneously given on the title page as F. v. Tennecker.)</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_121"></a><a href="#refanchor121" class="reflabel">121.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Loiset, B.</span> See 71, p. 132.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_122"></a><a href="#refanchor122" class="reflabel">122.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs">D——. Über die Abrichtung der kleinen Kunstpferde zu dem +Zählen mit dem Fusse, Kopfschütteln und dgl. Zeitung für +die Pferdezucht, den Pferdehandel, die Pferdekenntnis usw., +Tübingen, 1804, Vol. 4, p. 51.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_123"></a><a href="#refanchor123" class="reflabel">123.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Lang, R.</span> See 118, pp. 52 f.</div></td> +</tr> + +<tr valign="top"> +<td align="right" width="5%"><a name="ref_124"></a><a href="#refanchor124" class="reflabel">124.</a></td> +<td width="95%" style="text-align:justify;"><div class="refs"><span class="smcap">Buffon, Cte de</span>, et <span class="smcap">L. Daubenton</span>. Histoire naturelle, générale +et particulière. Paris, Imprimerie royale, 1753, Vol. 4, +p. 169.</div></td> +</tr> +</table><span class="pagenum"><a name="Page_275" id="Page_275"></a>[Pg 275]</span> +<p><span class="pagenum"><a name="Page_276" id="Page_276"></a>[Pg 276]</span></p> + +<hr class="newpg" style="width: 65%;"><span class="pagenum"><a name="Page_277" id="Page_277"></a>[Pg 277]</span> +<h3 style="padding-top:1em;text-align:left;">Angell's Text-book of General Psychology.</h3> + +<p class="blockquot" style="text-indent:0;word-spacing:.2em;">New Edition. By <span class="smcap">James Rowland Angell</span>, Professor and +Head of the Department of Psychology in the University +of Chicago. Fourth Edition, Revised and Enlarged. +ix+468 pp. 8vo. $1.60.</p> + +<div style="font-size:.85em;"> +<p>The fourth edition contains a large amount of new material, chiefly +empirical in character. To offset this addition, many of the more strictly +theoretical discussions have been condensed. The old material has been +rearranged and many new drawings have been supplied.</p> + +<p class="blockquot"><span class="smcap">Charles H. Judd</span>, University of Chicago:—I regard it as a most +excellent text. Its clear and thoroly interesting style will, I am +sure, make it very attractive to students. It is complete and compact. +Indeed it is a capital presentation of modern psychology.</p> +</div> + + +<h3 style="text-align:left;">Seashore's Elementary Experiments in Psychology.</h3> + +<p class="blockquot" style="text-indent:0;word-spacing:.2em;">By <span class="smcap">Carl Emil Seashore</span>, Head of the Department of +Philosophy and Psychology in the State University of Iowa. +ix+281 pp. 12mo. $1.00.</p> + +<div style="font-size:.85em;"> +<p>A supplement to a regular text-book in elementary psychology. It +provides experiments for one laboratory period a week for one semester.</p> + +<p class="blockquot"><span class="smcap">Frank Drew</span>, State Normal School, Worcester, Mass.:—The +range of experiments and the simplicity of their presentation are +admirable. They will deepen insight.</p> +</div> + +<h3 style="text-align:left;">Jones's Logic, Inductive and Deductive.</h3> + +<p class="blockquot" style="text-indent:0;word-spacing:.2em;">By <span class="smcap">Adam L. Jones</span>, Professor in Columbia University. +ix+304 pp. 12mo. $1.00.</p> + +<p style="font-size:.85em;">The aim of this text-book is to present, in as concrete a form as is +possible, the rudiments of Logic, considered as method.</p> + + +<h3 style="text-align:left;">Jastrow's Psychology of Stereoscopic Vision.</h3> + +<p class="blockquot" style="text-indent:0;word-spacing:.2em;">By <span class="smcap">Joseph Jastrow</span>, Professor in the University of Wisconsin. + <span style="letter-spacing:.3em;">[<i>In press.</i>]</span></p> + + +<h3 style="text-align:left;">Bode's Logic.</h3> + +<p class="blockquot" style="text-indent:0;word-spacing:.2em;">By <span class="smcap">W. H. Bode</span>, Professor in the University of Illinois. $1.00.</p> + + +<div style="text-align:center;text-indent:0em;font-weight:bold;padding-top:1em;"> +<span style="font-size:1.2em;">HENRY HOLT AND COMPANY</span><br> +<span style="font-size:1em;">NEW YORK</span> +</div> + + +<hr class="newpg" style="width: 65%;"><span class="pagenum"><a name="Page_278" id="Page_278"></a>[Pg 278]</span> + +<h2 class="newpg" style="padding-top:1em;padding-bottom:.1em;">LATEST VOLUMES IN<br> +<span style="border-bottom:2px solid;">THE AMERICAN NATURE SERIES</span></h2> + + +<p style="text-align:center;text-indent:0em;">(Prospectus of entire Series on request)</p> + + +<h3>INSECTS AND DISEASE</h3> + +<p style="margin-left:5%;margin-right:5%;word-spacing:.2em;">By <span class="smcap">R. W. Doane</span>, of Stanford University. Illustrated. +$1.50 net; by mail, $1.62.</p> + +<p style="margin-left:5%;margin-right:5%;font-size:.85em;">"Describes lucidly and entertainingly, in language that all may understand, +the discoveries in the disease-bearing qualities of insects, the successful +fights that have been made in consequence against yellow fever, +malaria and plague, and the present state of the investigations."—<i>New +York Sun.</i></p> + + +<h3>THE CARE OF TREES IN LAWN, STREET, AND PARK</h3> + +<p style="margin-left:5%;margin-right:5%;word-spacing:.2em;">By <span class="smcap">B. E. Fernow</span>, of the University of Toronto. Illustrated. +$2.00 net; by mail, $2.17.</p> + +<p style="margin-left:5%;margin-right:5%;font-size:.85em;">Written for amateurs by a forester, this volume furnishes information +such as the owner of trees or the "tree warden" may need.</p> + +<p style="margin-left:5%;margin-right:5%;font-size:.85em;">"Truly admirable ... eminently practical.... His list of trees +desirable for shade and ornament is a full and most valuable one, and +the illustrations are enlightening."—<i>New York Tribune.</i></p> + + +<h3>HARDY PLANTS FOR COTTAGE GARDENS</h3> + +<p style="margin-left:5%;margin-right:5%;word-spacing:.2em;">By <span class="smcap">Helen R. Albee</span>, Author of "Mountain Playmates." +Illustrated. 12mo. $1.60 net; by mail, $1.75.</p> + +<p style="margin-left:5%;margin-right:5%;font-size:.85em;">"Eminently practical and well arranged.... Lists giving manner of +growth, height, time of blooming, exact color, special requirements +of soil and moisture are provided, and proper classifications and indexes +make the book one of the most valuable yet offered to the garden +grower."—<i>Boston Transcript.</i></p> + + +<h3>SHELL-FISH INDUSTRIES</h3> + +<p style="margin-left:5%;margin-right:5%;word-spacing:.2em;">By <span class="smcap">James L. Kellogg</span>, of Williams College. Illustrated. +$1.75 net; by mail, $1.91.</p> + +<p style="margin-left:5%;margin-right:5%;font-size:.85em;">"Interests all classes, the biologist, the oyster grower, the trader and +the eater of oysters. The whole book is very readable."—<i>New York Sun.</i></p> + + +<h3>FISH STORIES: Alleged and Experienced, with a Little History, Natural and Unnatural</h3> + +<p style="margin-left:5%;margin-right:5%;word-spacing:.2em;">By <span class="smcap">Charles F. Holder</span> and <span class="smcap">David Starr Jordan</span>. With +colored plates and many illustrations from photographs. +$1.75 net; by mail, $1.87.</p> + +<p style="margin-left:5%;margin-right:5%;font-size:.85em;">"A delightful miscellany, telling about fish of the strangest kind. +Nearly everything that is entertaining in the fish world is touched upon +and science and fishing are made very readable."—<i>New York Sun.</i></p> + + +<h3>INSECT STORIES</h3> + +<p style="margin-left:5%;margin-right:5%;word-spacing:.2em;">By <span class="smcap">Vernon L. Kellogg</span>. Illustrated. $1.50 net; by mail, $1.62.</p> + +<p style="margin-left:5%;margin-right:5%;font-size:.85em;">"The author is among a few scientific writers of distinction who can +interest the popular mind. No intelligent youth can fail to read it with +delight and profit."—<i>The Nation.</i></p> + +<div class="figcenter" style="padding-top:.3em;"><img src="images/holt.png" border="0" alt="HENRY HOLT AND COMPANY PUBLISHERS NEW YORK" title="" width="700" height="73"> +</div> + + + + +<hr style="width: 65%;" class="newpg"><span class="pagenum"><a name="Page_279" id="Page_279"></a>[Pg 279]</span> +<div class="figcenter" style="padding-top:1em;padding-bottom:1em;"><img src="images/american_science.png" border="0" alt="American Science Series" title="" width="579" height="55"> +</div> +<div style="margin-right:10%;margin-left:10%"> +<h3 style="text-align:left;">Physics.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">A. L. Kimball</span>, Professor in Amherst College.</p> + +<h3 style="text-align:left;">Physics.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">George F. Barker</span>.</p> + +<h3 style="text-align:left;">Chemistry.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">Ira Remsen</span>, President of the Johns Hopkins University.</p> + +<h3 style="text-align:left;">Astronomy.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">Simon Newcomb</span> and <span class="smcap">Edward S. Holden</span>.</p> + +<h3 style="text-align:left;">Geology.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">Thomas C. Chamberlin</span> and <span class="smcap">Rollin D. Salisbury</span>, +Professors in the University of Chicago.</p> + +<h3 style="text-align:left;">Physiography.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">Rollin D. Salisbury</span>, Professor in the University of Chicago.</p> + +<h3 style="text-align:left;">General Biology.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">William T. Sedgwick</span>, Professor in the Mass. Institute, +and <span class="smcap">Edmund B. Wilson</span>, Professor in Columbia University.</p> + +<a name="tn_png_286"></a><!--TN: Comma changed to period after "Botany"--><h3 style="text-align:left;">Botany.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">Charles E. Bessey</span>, Professor in the University of Nebraska.</p> + +<h3 style="text-align:left;">Zoology.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">A. S. Packard</span>, Professor in Brown University.</p> + +<h3 style="text-align:left;">The Human Body.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">H. Newell Martin</span>.</p> + +<h3 style="text-align:left;">Psychology.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">William James</span>, Professor in Harvard University.</p> + +<h3 style="text-align:left;">Ethics.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">John Dewey</span>, Professor in Columbia University and +<span class="smcap">James H. Tufts</span>, Professor in the University of Chicago.</p> + +<h3 style="text-align:left;">Political Economy.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">Francis A. Walker</span>.</p> + +<h3 style="text-align:left;">Finance.</h3> +<p style="margin-left: 2em;text-indent:0em;">By <span class="smcap">Henry C. Adams</span>, Professor in the University of Michigan.</p> + + +<p>For full descriptions of the Advanced, Briefer, and Elementary +Courses published under each topic, see the publishers' +Educational Catalog.</p> +</div> +<div class="figcenter" style="padding-top:.75em;"><img src="images/holt2.png" border="0" alt="HENRY HOLT & CO. 34 West 33d Street, N. Y. +378 Wabash Ave., Chicago" title="" width="700" height="47"> +</div> + + +<hr class="newpg" style="width: 65%;"> +<div class="footnotes"><h2>Transcriber's Notes</h2> +<p style="margin-right:5%;margin-left:5%;text-indent:0em;">Illustrations have been moved +near the relevant section of the text.</p> +<p style="margin-right:5%;margin-left:5%;text-indent:0em;">Inconsistent use of spacing +has been retained for page numbers followed by "f" or "ff", and for "i.e." / "i. e.", "e.g." / "e. g.", and "c.f." / "c. f." +Inconsistent use of commas following "i.e.", "e.g.", and "c.f." has also been retained. +Inconsistent use of single and double quotes +around words and the placing of punctuation either within or external to quotes has been left +as-is. Capitalization inconsistencies and grammatical errors relating to subject/verb agreement were also retained.</p> + +<p style="margin-right:5%;margin-left:5%;text-indent:0em;">Inconsistent hyphenation, accents, and use of separate words have been retained for +"any one" / "anyone", "arm movement" / "arm-movement", "backstep" / "back-step", "blind spot" / "blind-spot", "by the way" / +"by-the-way", "counting machine" / "counting-machine", "divining rod" / "divining-rod", "ear movements" / "ear-movements", "eye movement(s)" / +"eye-movement(s)", "eyebrows" / "eye-brows", "first rank" / +"first-rank", "four fifths" / "four-fifths", "Hans problem" / +"Hans-problem", "head jerk" / "head-jerk", "head movement(s)" / +"head-movement(s)", "hoped for" / "hoped-for", "memory images" / "memory-images", +"movement impulse" / "movement-impulse", "movement responses" / +"movement-responses", "number concepts" / "number-concepts", "number terms" / +"number-terms", "psychophysical" / "psycho-physical", "some one" / "someone", +"sound waves" / "sound-waves", "thought processes" / "thought-processes", +"tieraugen" / "tier-augen", "time measurements" / "time-measurements", +"training process" / "training-process", "vaudeville stage" / "vaudeville-stage", +"well disposed" / "well-disposed", "well known" / "well-known", "well trained" / +"well-trained" "zoologist" / "zoölogist" / "Zoological" / "Zoölogical".</p> +<p style="margin-right:5%;margin-left:5%;text-indent:0em;">There is no direct reference to +Table of Reference item 105 or 112 within this book.</p> +<p style="margin-right:5%;margin-left:5%;text-indent:0em;">Here is a list of the minor typographical corrections made:</p> +<div style="margin-right:15%;margin-left:15%;"> +<ul> +<li><a href="#tn_png_6">Bracket removed following "1904"</a></li> +<li><a href="#tn_png_6a">"VI" changed to "IV"</a></li> +<li><a href="#tn_png_6b">Hyphen added between "September" and "Commission"</a></li> +<li><a href="#tn_png_27">"vice versa" italicized</a></li> +<li><a href="#tn_png_43">Double quote added after "'Hans'?"</a></li> +<li><a href="#tn_png_57">"elasping" changed to "elapsing"</a></li> +<li><a href="#tn_png_65">Bracket removed following "utility."</a></li> +<li><a href="#tn_png_74">"Futhermore" changed to "Furthermore"</a></li> +<li><a href="#tn_png_84">"wtih" changed to "with"</a></li> +<li><a href="#tn_png_85">Comma removed after "Problems"</a></li> +<li><a href="#tn_png_89">Comma removed after "errors"</a></li> +<li><a href="#tn_png_89a">Comma removed after "errors"</a></li> +<li><a href="#tn_png_90">"reponse" changed to "response"</a></li> +<li><a href="#tn_png_90a">Comma changed to period after "one"</a></li> +<li><a href="#tn_png_96">Period added after "Mr"</a></li> +<li><a href="#tn_png_98">Comma added after "continuously"</a></li> +<li><a href="#tn_png_105">"preceive" changed to "perceive"</a></li> +<li><a href="#tn_png_122">Double quote added before "Inhalt"</a></li> +<li><a href="#tn_png_123">"concrn" changed to "concern"</a></li> +<li><a href="#tn_png_129">"of" changed to "is"</a></li> +<li><a href="#tn_png_129a">"is" changed to "of"</a></li> +<li><a href="#tn_png_134">Period removed after "I"</a></li> +<li><a href="#tn_png_142">"to to" replaced by "to"</a></li> +<li><a href="#tn_png_145">Period added after "50cm"</a></li> +<li><a href="#tn_png_153">Double quote added after "you?"</a></li> +<li><a href="#tn_png_157">Double quote removed after "Perseverationstendenz"</a></li> +<li><a href="#tn_png_161">Comma removed from before "continued"</a></li> +<li><a href="#tn_png_163">"proceesses" changed to "processes"</a></li> +<li><a href="#tn_png_166">em-dash changed to hyphen between "soixante" and "six"</a></li> +<li><a href="#tn_png_169">"asociate" changed to "associate"</a></li> +<li><a href="#tn_png_180">Double quote added before "streifenförmige"</a></li> +<li><a href="#tn_png_186">"explantion" changed to "explanation"</a></li> +<li><a href="#tn_png_195">Comma added after "Another"</a></li> +<li><a href="#tn_png_216">"Ostens'" changed to "Osten's"</a></li> +<li><a href="#tn_png_219">"baguette")" changed to "baguette)""</a></li> +<li><a href="#tn_png_219a">"role" changed to "rôle"</a></li> +<li><a href="#tn_png_219b">"taks" changed to "takes"</a></li> +<li><a href="#tn_png_219c">em-dash changed to hyphen before "lens"</a></li> +<li><a href="#tn_png_219d">"satisfactury" changed to "satisfactory"</a></li> +<li><a href="#tn_png_219e">"thought" changed to "though"</a></li> +<li><a href="#tn_png_219f">"53" changed to "73"</a></li> +<li><a href="#tn_png_219g">Apostrophe changed to comma between "84" and "85"</a></li> +<li><a href="#tn_png_219i">"detail" changed to "details"</a></li> +<li><a href="#tn_png_223">"expectpectantly" changed to "expectantly"</a></li> +<li><a href="#tn_png_231">Comma changed to period after "stimuli"</a></li> +<li><a href="#tn_png_238">"suppossed" changed to "supposed"</a></li> +<li><a href="#tn_png_242">Double quote added after "himself"</a></li> +<li><a href="#tn_png_247">"diminshingly" changed to "diminishingly"</a></li> +<li><a href="#tn_png_250">"acounts" changed to "accounts"</a></li> +<li><a href="#tn_png_257">Single quote moved from before "twice," to after it</a></li> +<li><a href="#tn_png_258">Double quote removed from before "How"</a></li> +<li><a href="#tn_png_265">Period removed after "found?"</a></li> +<li><a href="#tn_png_268">"af" changed to "of"</a></li> +<li><a href="#tn_png_270">"Von" changed to "von"</a></li> +<li><a href="#tn_png_279">Period removed after "Stuttgart"</a></li> +<li><a href="#tn_png_286">Comma changed to period after "Botany"</a></li> +</ul> + +</div> +</div> + + + + + + + + +<pre> + + + + + +End of the Project Gutenberg EBook of Clever Hans, by Oskar Pfungst + +*** END OF THIS PROJECT GUTENBERG EBOOK CLEVER HANS *** + +***** This file should be named 33936-h.htm or 33936-h.zip ***** +This and all associated files of various formats will be found in: + 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You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Clever Hans + (The horse of Mr. Von Osten): A contribution to experimental + animal and human psychology + +Author: Oskar Pfungst + +Translator: Carl L. Rahn + +Release Date: October 11, 2010 [EBook #33936] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK CLEVER HANS *** + + + + +Produced by Audrey Longhurst, Linda Hamilton and the Online +Distributed Proofreading Team at http://www.pgdp.net + + + + + + + + + + [Illustration: CLEVER HANS] + + + + + CLEVER HANS + + (THE HORSE OF MR. VON OSTEN) + + _A CONTRIBUTION TO EXPERIMENTAL + ANIMAL AND HUMAN + PSYCHOLOGY_ + + BY + OSKAR PFUNGST + + WITH AN INTRODUCTION BY PROF. C. STUMPF, + AND ONE ILLUSTRATION AND FIFTEEN FIGURES + + TRANSLATED FROM THE GERMAN + BY + CARL L. RAHN + _Fellow in Psychology in the University of Chicago_ + + WITH A PREFATORY NOTE BY + JAMES R. ANGELL + _Professor of Psychology in the University of Chicago_ + + [Illustration] + + NEW YORK + HENRY HOLT AND COMPANY + 1911 + + + + + COPYRIGHT, 1911, + BY + HENRY HOLT AND COMPANY + + + + +PREFATORY NOTE + +[BY JAMES R. ANGELL] + +_The University of Chicago_ + + +It gives me great pleasure to accept the invitation of the publishers to +write a word of introduction for Mr. Rahn's excellent translation of +"Der Kluge Hans", a book which in the original has been but little known +to American readers. The present wave of interest in animal life and +behavior renders its appearance peculiarly appropriate. + +No more remarkable tale of credulity founded on unconscious deceit was +ever told, and were it offered as fiction, it would take high rank as a +work of imagination. Being in reality a record of sober fact, it verges +on the miraculous. After reading Mr. Pfungst's story one can quite +understand how sedate and sober Germany was for months thrown into a +turmoil of newspaper debate, which for intensity and range of feeling +finds its only parallel in a heated political campaign. That the subject +of the controversy was the alleged ability of a trained horse to solve +complex arithmetical problems may excite gaiety and even derision, until +one hears the details. Scientists and scholars of the highest eminence +were drawn into the conflict, which has not yet wholly subsided, +although the present report must be regarded as quite final in its +verdict. + +As for Hans himself, he has become the prototype of a host of less +distinguished imitators representing every level of animal life, and +when last heard from he was still entertaining mystified audiences by +his accomplishments. + +But the permanent worth of the book is not to be found in its record of +popular excitement, interesting as that is. It is a document of the very +first consequence in its revelation of the workings of the animal mind +as disclosed in the horse. Animal lovers of all kinds, whether +scientists or laymen, will find in it material of greatest value for the +correct apprehension of animal behavior. Moreover, it affords an +illuminating insight into the technique of experimental psychology in +its study both of human and animal consciousness. Finally, it contains a +number of highly suggestive observations bearing on certain aspects of +telepathy and muscle-reading. All things considered, it may fairly be +said that few scientific books appeal to so various a range of interests +in so vital a way. + +Readers who wish to inform themselves of all the personal circumstances +in the case may best read the text just as it stands. Those who desire +to get at the pith of the matter without reference to its historical +settings, may be advised to omit the Introduction by Professor Stumpf of +the University of Berlin, together with supplements II, III and IV. + + + + +CONTENTS + + + PAGE + PREFATORY NOTE (By JAMES R. ANGELL) v + + INTRODUCTION (By C. STUMPF) 1 + + + CHAPTER + I. THE PROBLEM OF ANIMAL CONSCIOUSNESS AND "CLEVER HANS" 15 + + II. EXPERIMENTS AND OBSERVATIONS 30 + + III. THE AUTHOR'S INTROSPECTIONS 88 + + IV. LABORATORY TESTS 102 + + V. EXPLANATION OF THE OBSERVATIONS 141 + + VI. GENESIS OF THE REACTION OF THE HORSE 212 + + CONCLUSION 240 + + + SUPPLEMENTS: + + I. MR. VON OSTEN'S METHOD OF INSTRUCTION (By C. STUMPF) 245 + + II. THE REPORT OF SEPTEMBER 12th, 1904 253 + + III. AN ABSTRACT FROM THE RECORDS OF THE + SEPTEMBER-COMMISSION 255 + + IV. THE REPORT OF DECEMBER 9th, 1904 261 + + + TABLE OF REFERENCES 267 + + + + +INTRODUCTION + +[BY C. STUMPF] + + +A horse that solves correctly problems in multiplication and division by +means of tapping. Persons of unimpeachable honor, who in the master's +absence have received responses, and assure us that in the process they +have not made even the slightest sign. Thousands of spectators, +horse-fanciers, trick-trainers of first rank, and not one of them during +the course of many months' observations are able to discover any kind of +regular signal. + +That was the riddle. And its solution was found in the unintentional +minimal movements of the horse's questioner. + +Simple though it may seem, the history of the solution is nevertheless +quite complex, and one of the important incidents in it is the +appearance of the zooelogist and African traveler, Schillings, upon the +scene, and then there is the report of the so-called Hans-Commission of +September 12, 1904. And finally there is the scientific investigation, +the results of which were published in my report of December 9, 1904. + +After a cursory inspection during the month of February, I again called +upon Mr. von Osten in July, and asked him to explain to Professor +Schumann and me just what method he had used in instructing the horse. +We hoped in this way to gain a clue to the mechanism of Hans's feats. +The most essential parts of the information thus gleaned are summarized +in Supplement I. Mr. Schillings came into the courtyard for the first +time about the middle of July. He came as skeptical as everyone else. +But after he, himself, had received correct responses, he too became +convinced, and devoted much of his time to exhibiting the horse, and +daily brought new guests. To be perfectly frank, at the time this seemed +to us a disturbing factor in the investigation, but now we see that his +intervention was a link in the chain of events which finally led to an +explanation. For it was through him that the fact was established beyond +cavil, that the horse was able to respond to strangers in the master's +absence. Heretofore, this had been noted only in isolated cases. Since +it could not be assumed that a well-known investigator should take it +upon himself to mislead the public by intentionally giving signs, the +case necessarily from that time on appeared in the eyes of others in a +light quite different from that in which ordinary circus-tricks would +appear, to which it bore such a striking external resemblance. No matter +how this state of affairs may have arisen in the course of years, no +matter how it might eventually be explained,--the quality of the +extraordinary would necessarily attach itself to this particular case, +as it did. + +Of course, to many persons in the interested public the result was +merely that Schillings, also, was placed in the category of deceivers. +On the other hand there were reputable scientists who could not dispose +of the matter in that fashion, and these now openly took their stand +with Schillings and declared that they believed in the horse's ability +to think. Zooelogists especially, saw in von Osten's results evidence of +the essential similarity between the human and the animal mind, which +doctrine has been coming more and more into favor since the time of +Darwin. Educators were disposed to be convinced, on account of the +clever systematic method of instruction which had been used and which +had not, till then, been applied in the education of a horse. In +addition, there were many details which, it seemed, could not be +explained in any other way. So far as I myself was concerned, I was +ready to change my views with regard to the nature of animal +consciousness, as soon as a careful examination would show that nothing +else would explain the facts, except the assumption of the presence of +conceptual thinking. I had thought out the process hypothetically, i. e., +how one might conceive of the rise of number concepts and arithmetical +calculation along the peculiar lines which had been followed in Hans's +education, and on the basis of the assumption that the beginnings of +conceptual thinking are present in animals. Also, I had too much faith +in human nature to fear lest nothing peculiarly human should remain +after the art of handling numbers should be shown to be common property +with the lower forms. But under no circumstances would I have undertaken +to make a public statement in favor of any particular view in this +extraordinary case, before a thorough investigation, in accordance with +scientific principles, had been made. I expressed this sentiment at the +time, and recommended the appointment of an investigating commission (in +the "Tag" of September 3, 1904). + +The purpose of this commission was misunderstood, and therefore many +were disappointed with the report which it published, (Supplement II). +Some had been expecting a positive conclusive explanation; the +commission recommended further investigation. Some had asked for a +solution of the question whether or not the horse was able to think; the +commission maintained neither the one, nor the other. Some had indicated +as the main condition of a satisfactory investigation, that both Mr. von +Osten and Mr. Schillings be excluded from the tests; this was not done. + +But the commission--which, by the way, did not give itself this name, +since it had been delegated by no one--undoubtedly had the right to +formulate its problem as it saw fit, and this was carefully expressed at +the beginning of its report as follows: "The undersigned came together +for the purpose of investigating the question whether or not there is +involved in the feats of the horse of Mr. von Osten anything of the +nature of tricks, that is, intentional influence or aid on the part of +the questioner." It was this preliminary question, and not whether or +not the horse could think, which the commission intended to answer. They +proposed to act as a sort of court of honor for the two gentlemen who +had been attacked. It is only in this light that even the _raison +d'etre_ of this body can be understood; for a scientific commission +composed of thirteen men, possessed of varying degrees of scientific +preparation, would have been an absurd travesty, and it will readily be +seen why the two men, who had been attacked, should not be excluded, +since it was they, and primarily Mr. von Osten, upon whom the +observations were to be made. + +To be sure the commission did go one step beyond that which it had +proposed to itself, since it added that it believed that unintentional +signs of the kind which are at present familiar, were also excluded. +This led many to the unwarranted conclusion that the commission had +declared that Hans was able to think. Whereas the thing which might have +been logically suggested was that instead of the assumption of the +presence of independent thinking, the commission may have had in mind +unintentional signs of a kind hitherto unknown. I explained this to a +reporter of the "Frankfurter Zeitung" (Mr. A. Gold), who had come to me +for information, and in his article he made this hypothesis appear as +the most probable one.[A] Certain statements of the circus-manager +Busch, who speaks of a 'connection' of some sort, go to show that other +members of the commission held to the view just stated. + + [Footnote A: "Frankfurter Zeitung" of September 22, 1904: + "Concerning the question whether the horse was given some sort of + aid, Professor Stumpf expressed himself freely. He said: 'We were + careful to state in our report that the intentional use of the + (actual) means of training, on the part of the horse's teacher, is + out of the question, ... nor are there involved any of the known + kinds of unconscious, involuntary aids. Our task was completed after + we had ascertained that no tricks or aids of the traditional sort + were being employed'." After some remarks on unconscious habituation + and self-training on the part of animals, the writer arrives at the + conclusion that "the horse of Mr. von Osten has been educated by its + master in the most round-about way, in accordance with a method + suited for the development of human reasoning powers, hence in all + good faith, to give correct responses by means of tapping with the + foot. But what the horse really learned by this wearisome process + was something quite different, something that was more in accord + with his natural capacities,--he learned to discover by purely + sensory aids which are so near the threshold that they are + imperceptible for us and even for the teacher, when he is expected + to tap with his foot and when he is to come to rest."] + +But how did it come to pass that the commission should deny completely +the presence of intentional signals, while, as regards the unintended, +it excluded only those which were of the known sort? The report clearly +shows that the decision as to the absence of voluntary signals was +based not merely upon the fact that no such signals had been detected by +the most expert observers, but also upon the character of the two men +who exhibited the horse, upon their behavior during the entire period, +and upon the method of instruction which Mr. von Osten had employed. In +the case of unintentional signs, on the other hand, one had to deal with +the fact with which physiologists and experimental psychologists are +especially familiar, viz., that our conscious states, without our +willing it--indeed, even in spite of us--are accompanied by bodily +changes which very often can be detected only by the use of extremely +fine graphic methods. The following is a more general instance: every +mother, who detects the lie or divines the wish in the eyes of the +child, knows that there are characteristic changes of facial expression, +which are, nevertheless, very difficult of definition.[B] + + [Footnote B: "From the productions of the 'thought-readers' we see + how slight and seemingly insignificant the unconscious movements may + be, which serve as signs for a sensitive re-agent. But in this case + no contact is necessary. There would have to be some sort of visible + or audible expression on the part of the questioner. No proof for + this has as yet been advanced." + + How any one possessing the power of logical thought could possibly + infer from these words of mine (published in the above-mentioned + article in the "Tag"), that I denied the possibility of the + occurrence of visual signs, is to me incomprehensible. What I did + deny, and still deny, is that up to that time any had been proven to + occur.] + +The commission did not even maintain or believe that unintentional signs +within the realm of the senses known to us, were to be excluded. +Professor Nagel and I would never have subscribed to any such +conclusion. The sentence in question, therefore, could only be +interpreted as follows: that signals of the kind that are used +intentionally in the training of horses, could not have occurred even +as unintended signs, for otherwise Mr. Busch would have detected them. +And in order to be observed by him it was immaterial whether they were +given purposely or not. The same signs, therefore, which as a result of +his observations were declared not to be present, could not be assumed +to be involved as unintentional. + +For my part I am ready to confess that at this time I did not expect to +find the involuntary signals, if any such were involved, in the form of +movements. I had in mind rather some sort of nasal whisper such as had +been invoked by the Danish psychologist A. Lehmann, in order to explain +certain cases of so-called telepathy. I could not believe that a horse +could perceive movements which escaped the sharp eyes of the +circus-manager. To be sure, extremely slight movements may still be +perceived after objects at rest have become imperceptible. But one would +hardly expect this feat on the part of an animal, who was so deficient +in keenness of vision, as we have been led, by those of presumably +expert knowledge, to believe of the horse,--one would expect it all the +less because Mr. von Osten and Mr. Schillings would move hither and +thither in most irregular fashion while the horse was going through his +tapping, and would therefore make the perception of minute movements all +the more difficult. + +Nor was there anything in the exhibitions given at the same time in a +Berlin vaudeville by the mare "Rosa," which might have shattered this +belief. For, in the case of this rival of Hans, the movements involved +were comparatively coarse. The closing signal consisted in bending +forward on the part of the one exhibiting the mare, while up to that +point he had stood bolt upright. Most persons were not aware of this, +because this change in posture cannot be noticed from the front. I +happened to sit to the side and caught the movement every time. It was +the same that was noted by Dr. Miessner, another member of the +commission, (see page 256), but concerning which he did not give me a +more complete account. Later I learned through Professor Th. W. +Engelmann that the very same movement was employed not long ago, for +giving signals to a dog exhibited at Utrecht. This particular movement +is very well adapted to commercial purposes, since the spectator always +tries to view the performance from a point as nearly in front of the +animal and its master as possible, thus making the detection of the +trick all the more difficult. + +The details of the various experiments made by this commission are given +in an excerpt from the records kept by Dr. von Hornbostel, which I +showed to a small group of persons a few days after the 12th of +September (Supplement III). At that time none of the particulars was +published, because the commission wished to wait until some positive +statement might be made. The public was merely to be assured that a +group of reputable men, from different spheres of life, who could have +no purpose in hazarding their reputation, believed that the case was one +worthy of careful investigation. + +I left Berlin on September 17th and did not return until October 3d. In +the meantime Mr. Schillings continued the investigation, and was +assisted in part by Mr. Oskar Pfungst, one of my co-workers at the +Psychological Institute. For the first time a number of tests were now +made in which neither the questioner, nor any of those present knew the +answer to the problem. Such tests naturally were the first steps toward +a positive investigation. The results were such that Mr. Schillings was +led to replace his hypothesis of independent conceptual thinking by one +of some kind of suggestion. In this he was strengthened somewhat by +having noted the fact that in his questions which he put to the horse, +he might proceed as far as to ask the impossible. He has always been +ready to offer himself in the tests which have been undertaken since +then. + +On October 13, 1904, together with the two gentlemen mentioned in the +beginning of my report, I began my more detailed investigation, and +finished on November 29. We worked for several hours on the average of +four times each week. I take this opportunity of giving expression of +the recognition which is due to the two gentlemen. They were ready to go +to the courtyard in all kinds of weather, at times they went without me, +and they always patiently discussed the order and method of the +experiments and the results. Dr. von Hornbostel had the important task +of keeping the records, and Mr. Pfungst undertook the conduct of the +experiments. It was he, who, soon after the blinder-tests disclosed the +necessary presence of visual signs, discovered the nature of these +signs. Without him we might have shown the horse to be dependent upon +visual stimuli in general, but we never would have been able to gain +that mass of detail, which makes the case valuable for human psychology. +But I am tempted to praise not merely his patience and skill, but also +his courage. For we must not believe that Mr. von Osten's horse was a +"perfectly gentle" animal. If he stood untied and happened to be excited +by some sudden occurrence, he would make that courtyard an unsafe place, +and both Mr. Schillings and Mr. Pfungst suffered from more than one +bite. In this connection I would also express my obligations to Count +Otto zu Castell-Ruedenhausen, for his frequent intercession on our behalf +with the owner of the horse, and for his many evidences of good-will and +helpfulness. + +After the publication of this report (Supplement IV), there was still +some further discussion of the case in societies of various kinds and in +the press, but no important objections were raised. A hippologist +thought that men of his calling should have been consulted, a +telepathist believed that telepathists should have been called in. There +was also some further talk of suggestion, will-transference, +thought-reading and the occult, but no attempt was made to elucidate +these vague terms with reference to their application to the case in +hand. Others adhered to the old cry of "fraud," for a share of which Mr. +Pfungst now fell heir. There were a few who felt it incumbent upon +themselves to preserve their 'priority,' and therefore stated with a +show of satisfaction that I had finally 'confessed' myself to hold their +respective points of view. As if there were anything like "confessions" +in science! As if mere affirmations, even though sealed and deposited in +treasure vaults, had any value with reference to a case in which every +manner of supposition had been advanced in lieu of explanation. Why did +they wait so long, if they had convincing proof for their position? + +And finally there were disappointed Darwinists who expressed fear lest +ecclesiastical and reactionary points of view should derive favorable +material from the conclusions arrived at in my report. Needless fear. +For lovers of truth it must always remain a matter of inconsequence +whether anyone is pleased or displeased with the truth, and whether it +is enunciated by Aristotle or Haeckel. + +Mr. von Osten, however, continued to exhibit Hans, and is probably doing +so still, but in what frame of mind, I dare not judge. The spectators +continue to look on, they are doubly alert to catch movements, and many +of them have learned from Mr. Schillings what kind of movements they are +to expect. But these "initiated" ones regularly return and declare that +there is nothing in the movements and that they simply could not +discover any aids given to the horse. Nothing can so well show how +difficult the case is, and how great the need of a thorough exposition +of the whole matter, than the account given in the following pages of +Mr. Pfungst. Its publication has been delayed on account of the +additional tests made in the laboratory, but we have reason to suppose +that through these additional tests the work has gained in permanent +value. Experimental psychologists will perhaps be greatly interested in +the graphic registration of the minute involuntary movements which +accompany the thought process, and in the artificial association of a +given involuntary movement with a given idea. Likewise the tests on +sense-perception in horses, which have led to essential changes in +hitherto current views, and the critical review of the comprehensive +literature on similar achievements of other animals, will be welcomed by +many. + +Before closing these introductory remarks, I would make one more +statement concerning Mr. von Osten. The reader will notice that the +judgment passed upon him in this treatise is placed at the end, whereas +in the report of the commission it came first. This was brought about by +the change that was made in the way of stating the problem. Then the +question discussed was whether 'tricks' were involved; now the question +is: What is the mechanism of the process? The question of the good faith +of the master was taken up once more only because the facts that were +brought to light by the later experimentation seemingly brought forward +new grounds for distrust. But by placing this discussion toward the end +of our report we wished to indicate that everything that is said of the +present status of facts, is quite independent of the view taken +concerning Mr. von Osten. Even assuming that the horse had been +purposely trained by him to respond to this kind of signal, the case +would still deserve a place in the annals of science. For visual signs, +planned and practiced so that they could not only be more readily +perceived by the animal than by man, but could be transferred from their +inventor to others without any betrayal of the secret,--this would be an +extraordinary invention, and Mr. von Osten would then be a fraud, but +also a genius of first rank. + +In truth he probably was neither, but I was brief in my report, for +otherwise I would have been obliged to go into more detail than the case +warranted. And a judgment passed upon a human personality is quite a +different matter from a judgment upon a horse. If it is unscientific to +make unqualified statements concerning a horse after the performance of +only a few experimental tests, it is certainly an unwarranted thing to +pass a moral judgment upon a man upon the basis of meagre material. +Anyone who would assume the role of judge should bear in mind that here +too we have more than a hundredfold the material which they could bring +forward, and among it some which, if taken alone, would be more +unfavorable than any that they had. But here all things should be +weighed together, and not in isolation. A former instructor of +mathematics in a German gymnasium, a passionate horseman and hunter, +extremely patient and at the same time highly irrascible, liberal in +permitting the use of the horse for days at a time and again tyrannical +in the insistence upon foolish conditions, clever in his method of +instruction and yet at the same time possessing not even the slightest +notion of the most elementary conditions of scientific procedure,--all +this, and more, goes to make up the man. He is fanatic in his +conviction, he has an eccentric mind which is crammed full of theories +from the phrenology of Gall to the belief that the horse is capable of +inner speech and thereby enunciates inwardly the number as it proceeds +with the tapping. From theories such as these, and on the basis of all +sorts of imagined emotional tendencies in the horse, he also managed to +formulate an explanation for the failure of the tests in which none of +the persons present knew the answer to the problem given the horse, and +also for the failure of those tests in which the large blinders were +applied. And he would often interfere with or hinder other tests which, +according to his point of view, were likely to lead us astray. And yet, +when the first tests with the blinders did turn out as unmistakably +sheer failures, there was such genuine surprise, such tragi-comic rage +directed against the horse, that we finally believed that his views in +the matter would be changed beyond a doubt. "The gentlemen must admit," +he said at the time, "that after seeing the objective success of my +efforts at instruction, I was warranted in my belief in the horse's +power of independent thought." Nevertheless, upon the following day he +was as ardent an exponent of the belief in the horse's intelligence as +he ever had been. + +And finally, after I could no longer keep from him the results of our +investigation, I received a letter from him in which he forbade further +experimentation with the horse. The purpose of our inquiries, he said, +had been to corroborate his theories. On account of his withdrawal of +the horse a few experimental series unfortunately could not be +completed, but happily the major portion of our task had been +accomplished. + + + + +THE HORSE OF MR. VON OSTEN + +CHAPTER I + +THE PROBLEM OF ANIMAL CONSCIOUSNESS AND "CLEVER HANS" + + +If we would appreciate the interest that has been aroused everywhere by +the wonderful horse solving arithmetical problems, we must first +consider briefly the present state of the problem of animal +consciousness.[C] Animal consciousness cannot be directly gotten at, and +the psychologist must therefore seek to appreciate it on the basis of +the animal's behavior and with the assistance of conceptions borrowed +from human psychology. Hence it is that animal psychology rests upon +uncertain foundations with the result that the fundamental principles +have been repeatedly questioned and agreement has not yet been attained. +The most important of these questions is, "Does the animal possess +consciousness, and is it like the human consciousness?" Comparative +psychologists divide into three groups on this question. + + [Footnote C: Since the present treatise is intended for the larger + public, this brief resume will probably be welcome to many.] + +The one group allows consciousness to the lower forms, but emphasizes +the assertion that between the animal and the human consciousness there +is an impassable gap. The animal may have sensations and memory-images +of sensations which may become associated in manifold combinations. Both +sensations and memory images are believed to be accompanied by +conditions of pleasure and of pain (so-called sensuous feelings), and +these in turn, become the mainsprings of desire. The possession of +memory gives the power of learning through experience. But with this, +the inventory of the content of animal consciousness is exhausted. The +ability to form concepts[D] and with their aid to make judgments and +draw conclusions is denied the lower forms. All the higher intellectual, +aesthetic and moral feelings, as well as volition guided by motives, are +also denied. Among the ancients this view was held by Aristotle and the +Stoics; and following them it was taught by the Christian Church. It +pervaded all mediaeval philosophy, which grew out of the teachings of +Aristotle and the Church. It is this philosophy, in the form of +Neo-Thomism, which still obtains in the Catholic world. + + [Footnote D: Ideas are copies of former sensations, feelings and + other psychic experiences and retain also the accidental signs which + belonged to those earlier experiences. They are images in the + concrete, such as the memory of a certain horse in a certain + definite situation ... say a well fed, long-tailed one standing at a + manger. A concept, on the other hand, is a mental construct which + has its rise in ideas, or memory-images, in that their essential + characteristics are abstracted. For this reason the concept has not + a definite image-content. (Thus the thought of "horse" in general, + is a concept. Not so the thought of a certain individual + horse,----that is an idea, with a definite image-content.)] + +During the 17th century, even though temporarily, another conception of +the consciousness of lower forms came to prevail and was introduced by +Descartes, the "Father" of modern philosophy. Far more radical than the +earlier conception, it denied to animals not only the power of abstract +thought, but every form of psychic life whatever, and reduced the lower +form to a machine, which automatically reacted upon external stimuli. +This daring view, however, prevailed for only a comparatively short +period; but owing to the opposition which it aroused, it gave a +tremendous impetus to the study of animal consciousness. Most of the +great philosophers following Descartes, such as Locke, Leibniz, Kant, +and Schopenhauer, however greatly they may have differed in other +points, in this one returned to the Aristotelian point of view. + +A third belief avers that animal and human consciousness do not differ +in essentials, but only in degree. This conclusion is regularly arrived +at by those who regard so-called abstract thought itself, as simply a +play of individual sensations and sensation-images, as did the French +and British associationists (Condillac and the Mills). The superiority +of man accordingly consisted in his ability to form more intricate +ideational complexes. Again, this conception of the essential similarity +of the human and the animal psyche has also always been arrived at by +the materialists (from Epicurus to C. Vogt and Buechner) who impute +reason to the animal form as well as to man. The same position is, +furthermore, taken by the evolutionists, including those who do not +subscribe to the doctrines of materialism. It has almost become dogma +with them that there exists an unbroken chain of psychic life from the +lowest protozoa to man. Haeckel, preeminently, though not always +convincingly, sought to establish such a graded series and thus to +bridge the chasm between the human and the animal consciousness. + +Two tendencies, therefore, are discernible in animal psychology. The +one seeks to remove the animal psyche farther away from the human, the +other tries to bring the two closer together. It is undoubtedly true +that many acts of the lower forms reveal nothing of the nature of +conceptual thinking. But that others might thus be interpreted cannot be +denied. But need they be thus interpreted?--There lies the dispute. A +single incontrovertible fact which would fulfil this demand, [i.e., +proof of conceptual thinking], would, at a stroke, decide the question +in favor of those who ascribe the power of thought to the lower forms. + +At last the thing so long sought for, was apparently found: A horse that +could solve arithmetical problems--an animal which, thanks to long +training, mastered not merely rudiments, but seemingly arrived at a +power of abstract thought and which surpassed, by far, the highest +expectations of the greatest enthusiast. + +And now what was it that this wonderful horse could do? The reader may +accompany us to an exhibition which was given daily before a select +company at about the noon hour in a paved courtyard surrounded by high +apartment houses in the northern part of Berlin. No fee was ever taken. +The visitor might walk about freely and if he wished, might closely +approach the horse and its master, a man between sixty and seventy years +of age. His white head was covered with a black, slouch hat. To his left +the stately animal, a Russian trotting horse, stood like a docile pupil, +managed not by means of the whip, but by gentle encouragement and +frequent reward of bread or carrots. He would answer correctly, nearly +all of the questions which were put to him in German. If he understood a +question, he immediately indicated this by a nod of the head; if he +failed to grasp its import, he communicated the fact by a shake of the +head. We were told that the questioner had to confine himself to a +certain vocabulary, but this was comparatively rich and the horse +widened its scope daily without special instruction, but by simple +contact with his environment. His master, to be sure, was usually +present whenever questions were put to the horse by others, but in the +course of time, he gradually responded to a greater and greater number +of persons. Even though Hans did not appear as willing and reliable in +the case of strangers as in the case of his own master, this might +easily be explained by the lack of authoritativeness on their part and +of affection on the part of Hans, who for the last four years had had +intercourse only with his master. + +Our intelligent horse was unable to speak, to be sure. His chief mode of +expression was tapping with his right forefoot. A good deal was also +expressed by means of movements of the head. Thus "yes" was expressed by +a nod, "no" by a deliberate movement from side to side; and "upward," +"upper," "downward," "right," "left," were indicated by turning the head +in these directions. In this he showed an astonishing ability to put +himself in the place of his visitors. Upon being asked which arm was +raised by a certain gentleman opposite him, Hans promptly answered by a +movement to the right, even though seen from his own side, it would +appear to be the left. Hans would also walk toward the persons or things +that he was asked to point out, and he would bring from a row of colored +cloths, the piece of the particular color demanded. Taking into account +his limited means of expression, his master had translated a large +number of concepts into numbers; e. g.:--the letters of the alphabet, +the tones of the scale, and the names of the playing cards were +indicated by taps. In the case of playing cards one tap meant "ace," two +taps "king," three "queen," etc. + +Let us turn now to some of his specific accomplishments. He had, +apparently, completely mastered the cardinal numbers from 1 to 100 and +the ordinals to 10, at least. Upon request he would count objects of all +sorts, the persons present, even to distinctions of sex. Then hats, +umbrellas, and eyeglasses. Even the mechanical activity of tapping +seemed to reveal a measure of intelligence. Small numbers were given +with a slow tapping of the right foot. With larger numbers he would +increase his speed, and would often tap very rapidly right from the +start, so that one might have gained the impression that knowing that he +had a large number to tap, he desired to hasten the monotonous activity. +After the final tap, he would return his right foot--which he used in +his counting--to its original position, or he would make the final count +with a very energetic tap of the left foot,--to underscore it, as it +were. "Zero" was expressed by a shake of the head. + +But Hans could not only count, he could also solve problems in +arithmetic. The four fundamental processes were entirely familiar to +him. Common fractions he changed to decimals, and _vice versa_; he could +solve problems in mensuration--and all with such ease that it was +difficult to follow him if one had become somewhat rusty in these +branches. The following problems are illustrations of the kind he +solved.[E] "How much is 2/5 plus 1/2?" Answer: 9/10. (In the case of all +fractions Hans would first tap the numerator, then the denominator; in +this case, therefore, first 9, then 10). Or again: "I have a number in +mind. I subtract 9, and have 3 as a remainder. What is the number I had +in mind?"--12. "What are the factors of 28?"--Thereupon Hans tapped +consecutively 2, 4, 7, 14, 28. "In the number 365287149 I place a +decimal point after the 8. How many are there now in the hundreds +place?"--5. "How many in the ten thousandths place?"--9. It will be +noticed, therefore, that he was able to operate with numbers far +exceeding 100, indeed he could manipulate those of six places. We were +told that this, however, was no longer arithmetical computation in the +true sense of the term; Hans merely knew after the analogy of 10 and 100 +that the thousands take the fourth place, the ten-thousands the fifth, +etc. If an error entered into Hans' answer, he could nearly always +correct it immediately upon being asked: "By how many units did you go +wrong?" + + [Footnote E: All examples mentioned are cited from extant works of + various observers.] + +Hans, furthermore, was able to read the German readily, whether written +or printed. Mr. von Osten, however, taught him only the small letters, +not the capitals. If a series of placards with written words were placed +before the horse, he could step up and point with his nose to any of the +words required of him. He could even spell some of the words. This was +done by the aid of a table devised by Mr. von Osten, in which every +letter of the alphabet, as well as a number of diphthongs had an +appropriate place which the horse could designate by means of a pair of +numbers. Thus in the fifth horizontal row "s" had first place; "sch" +second, "ss," third, etc.; so that the horse would indicate the letter +"s" by treading first 5, then 1, "sch," by 5 and 2, "ss" by 5 and 3. +Upon being asked "What is this woman holding in her hand?" Hans spelled +without hesitation: 3, 2; 4, 6; 3, 7; i. e., "Schirm" (parasol). At +another time a picture of a horse standing at a manger was shown him and +he was asked, "What does this represent?" He promptly spelled "Pferd" +(horse) and then "Krippe" (manger). + +He, moreover, gave evidence of an excellent memory. In passing we might +also mention that he knew the value of all the German coins. But most +astonishing of all was the following: Hans carried the entire yearly +calendar in his head; he could give you not only the date for each day +without having been previously taught anew, but he could give you the +date of any day you might mention. He could also answer such inquiries +as this: "If the eighth day of a month comes on Tuesday, what is the +date for the following Friday?" He could tell the time to the minute by +a watch and could answer off-hand the question, "Between what figures is +the small hand of a watch at 5 minutes after half-past seven?" or, "How +many minutes has the large hand to travel between seven minutes after a +quarter past the hour, and three quarters past?" Tasks that were given +him but once would be repeated correctly upon request. The sentence: +"Bruecke und Weg sind vom Feinde besetzt" (The bridge and the road are +held by the enemy), was given to Hans one day and upon the following day +he tapped consecutively the 58 numbers which were necessary for a +correct response. He recognized persons after having seen them but +once--yes, even their photographs taken in previous years and bearing +but slight resemblance. + +A corresponding high degree of sensory activity seemed to accompany +these astonishing feats of memory and reason. Although the horse is not +usually credited with a very keen sense of vision, Hans was able to +count the windows of distant houses and the street urchins climbing +about on neighboring roofs. He had an ear for the most subtle nuances of +the voice. He caught every word,--no matter how softly it was spoken--so +that we were not allowed to whisper the answer to a problem, even when +standing at a distance of several yards, since it would be +equivalent--so Mr. von Osten declared--to giving the result to the +horse. + +Musical ability also comes into the category of Hans' accomplishments. +He possessed, not only an absolute tone consciousness--a gift granted to +few of us in the human world--which enabled him to recognize a note +sounded or sung to him as c, d, etc. (within the once accented scale of +c-major), but also an infallible feeling for intervals, and could +therefore determine whether two tones, sounded simultaneously, composed +a third or fifth, etc. Without difficulty he analyzed compound clangs +into their components; he indicated their agreeableness or +disagreeableness and could inform us which tones must be eliminated to +make consonance out of dissonance. C, d and e were given simultaneously +and Hans was asked: "Does that sound pleasant?" He shook his head. "What +tone must be omitted to make it pleasant?" Hans trod twice--indicating +tone "d." When the seventh chord, d-f-a-c, was sounded, he shook his +head disapprovingly. He evidently was old-fashioned in his musical +tastes and not agreeably disposed toward modern music, so he indicated +by tapping that the seventh, c, would have to be eliminated; thus +changing the seventh chord to a minor chord in order to obtain harmony. +When asked what tones might not be given simultaneously with the fourth +and sixth, Hans indicated consecutively the third, fifth and seventh; +that the first might be added, he was ready to admit. Finally, he was +familiar with not less than thirteen melodies and their time. + +Not only in the high degree of development of the senses and the +intellect, but also in that of the feeling and the will, did Hans +possess a decided individuality. Being of a high-strung and nervous +temperament and governed by moods, he evinced strong likes and dislikes, +and frequently displayed an annoying stubbornness,--a fact often dwelt +upon by Mr. von Osten. He had never felt the whip, and therefore often +persisted in wilfully answering the simplest questions incorrectly and a +moment later would solve, with the greatest ease, some of the most +difficult problems. Whenever any one asked a question without himself +knowing the answer, Hans would indulge in all sorts of sport at the +questioner's expense. We were told that the sensitive animal could +easily perceive the questioner's ignorance and would therefore lose +confidence in, and respect for, him. It was felt to be desirable, +however, to have just such cases with correct responses. Often, too, +Hans would persist in giving what seemed an incorrect reply, but which +was later discovered to be correct. On the other hand it was useless to +try to get answers upon topics of which he knew nothing. Thus he ignored +questions put in French or Latin and became fidgety, thereby showing the +genuineness of his achievements; but upon topics with which he was +familiar he could not be led astray. Indeed, there was nothing but +language lacking to make him almost human and the intelligent animal was +declared by experienced educators to be at about the stage of +development of a child of 13 or 14 years. + +This wonderful horse, which in the opinion of its friends was the means +of deciding in the affirmative the old, old, question of the +rationality of the lower forms and thus changing radically the existing +Weltanschauung, aroused world-wide interest. A flood of articles +appeared in the newspapers and magazines, two monograph[1, 2] attempts at +explanation were devoted to him.[F] He was made the subject of popular +couplets, and his name was sung on the vaudeville stage. He appeared +upon picture post-cards and upon liquor labels, and his popularity was +shown by his reincarnation in the form of children's playthings. Many +personages of note who had seen the horse's exhibitions, declared, some +of them in public statements, that they were now convinced. Among these, +besides Mr. Schillings, were naturalists of note; e. g.: the African +explorer Prof. G. Schweinfurth, Dr. Heinroth and Dr. Schaeff, the +director of the zoological garden in Hanover; there were likewise +horse-fanciers of first-rank, such as General Zobel, and the well-known +hippological writer Major R. Schoenbeck. Again, the well-known +zooelogist, K. Moebius, writing in the "National-zeitung" declared he was +convinced of the horse's power to count and to solve arithmetical +problems. He also said that he believed the horse's memory and acute +power of sense-discrimination to be at the root of the matter. Those who +gleaned all their knowledge of the horse from newspaper reading were +satisfied to arrest judgment, or, on the other hand, became indignant at +the supposed imposition on the part of the gentleman of leisure and at +the gullibility of the public. Some would of course attempt explanations +on the basis of older facts. Here we have two points of view. + + [Footnote F: The works referred to in the text are to be found listed + on pages 267 ff.] + +Some tried to explain the whole thing on the basis of purely mechanical +memory and would thus allow the title "learned" but not "intelligent" +Hans. If, for instance, he was able to indicate the component of a clang +of three tones, it was not because he had the power to analyze the +tone-complex, but because he was able to see the stops of the harmonica +and was accustomed to give one tap for every stop which was closed. If +he was able to tell time by the watch, it was not because he read it, +but because he was always asked at the same hour of the day (which, of +course, was contrary to fact) and because he had learned by heart the +necessary number of taps. They also said that his manifold arithmetical +achievements were merely the expression of a remarkable memory; that in +the animal brain, lying fallow for centuries, there was stored up a +tremendous amount of energy, which here had been suddenly released. They +justified their point by calling to mind, in this connection, the +wonderful memory of primitive races. The authors of the two monographs +already mentioned, Zell and Freund, adopted this 'mnemotechnic' +interpretation, and the latter considered that he had disposed +definitely of the problem in designating the horse--a "four-legged +computing machine." + +Another group would not even allow Hans the glory of a wonderful memory. +He knew nothing. Rather was he to be regarded as a stupid Hans, and +totally dependent upon signs or helps given by his master. Only a very +few believed, however, that such signs--the nature of which was quite +unknown or regarding which only vague unsubstantiated suppositions were +advanced--were given unintentionally. Most of the critics openly averred +that we here had to do with intentional control, in other words, with +tricks. But not only did stupid orthodoxy dispose of the matter in this +way, but also the enlightened, who believe everything unusual to be +contrary to reason. They put the Hans problem on a level with +spiritualism, and were convinced that if the veil were removed a crass +imposition would be revealed. Professional trainers who regarded +themselves as well informed did not hesitate to give expression to this +same view, even though they had observed Hans inadequately or not at +all. + +The defenders of this second point of view were not at a loss to point +out the signs supposed to be given to Hans. One of these believed he had +discovered the primary means for giving these signs in the slouch hat of +Mr. von Osten. It was no accident, they said, that Mr. Schillings wore a +slouch hat when he experimented with the horse. It is sufficient to note +that Mr. Schillings was usually bare-headed or wore only a cap when he +tested the horse. Another accused, in like fashion, the long coat of the +experimenter; a third, who "had had opportunity to observe Hans on +several occasions," declared with equal certainty that the cue lay in +the movements of the hand as it was thrust into the pocket filled with +carrots. One circus-star declared, that the trick lay in eye movements, +another such star declared it lay in the movements of the hand. A sixth +discovered that the signs were "manifold" and adds, "to be sure, the +trainer must have a fund of such signs in order to prevent +embarrassment." Such a hypothesis is itself, it would seem, one of +embarrassment. On the other hand, there were many first-class observers +who vainly tried to discover regularly recurring signs; among them the +only professional trainer,--who had devoted any satisfactory length of +time to the horse and had also sought diligently for the signs in +question--said, "I was fully convinced that I would be able to explain +the problem in this way, but I was mistaken." The president of the +"Internationale Artisten Genossenschaft," a person who knew all the +usual means of control in trick performances, went over to the other +side as a result of his observations. + +There were others who sought for auditory signs. The opinion was +expressed that "Hans was unable to answer the simplest question such as +'What is two plus three?' whenever the questioner's tone of voice +differed from that of the master's." Another put chief stress upon the +changing inflection; furthermore, a "high degree of auditory +sensitivity" was often offered in explanation. + +The sense of smell was also made to bear some burdens. With its help, +for instance, Hans was believed to be able to recognize the photograph +of some one present, supposing, of course, that the person had carried +the picture about with him, thus allowing it to be impregnated with his +peculiar personal odor. One even suggested that the heat radiating from +the questioner's body and the electric stimulus conducted underground to +Hans's foot were sufficient explanation for his remarkable feats. + +Even the so-called N-rays, of one-day fame, which were supposed to +radiate from the human brain when in activity, were offered as a +solution. A similar thing may have been in the mind of the "natural +philosopher" who even after the publication of the December report, +wrote as follows in one of the journals: "On the basis of most careful +control, I have come to the conclusion, that the brain of the horse +receives the thought-waves which radiate from the brain of his master; +for mental work is, according to the judgment of science, physical +work." Of the same character are the explanations of two others, one of +whom declares that Hans was acting "under the magnetic influence of +man", while the other declared that "hypnotic suggestion is involved", +and, ignoring attested facts, tells us that, "The horse can execute the +commands of another only when the master, with whom it is 'en rapport', +wills that it shall obey." We may close the catalogue of explanations +with one more, which, in spite of its vagueness, found many defenders, +viz: suggestion. Without defining this conception more specifically and +without the slightest notion of the peculiar difficulties which it +involves (L. Loewenfeld in his "Handbuch des Hypnotismus" [Wiesbaden, +1901, pp. 35ff.] cites twenty different definitions of the term given by +as many authors) a critic writes: "The astounding phenomenon of an +animal apparently possessing human reason is to be attributed solely to +suggestion". Having referred to a dog trained for the vaudeville-stage, +the gentleman concludes that, "our intelligent horse, as well as the +dog, is simply of fine nervous organization and hence highly susceptible +to suggestions". + +What was to be done, with this mass of conflicting explanations? +Everyone considered his own opinion the only correct one, without, +however, being able to convince anyone else. The need here was not +simple affirmation, but proof. + + + + +CHAPTER II + +EXPERIMENTS AND OBSERVATIONS + + +A. EXPERIMENTAL CONDITIONS + +The observations on the horse under ordinary conditions would have been +quite insufficient for arriving at a decision as to the tenability of +the several possible explanations. For this purpose experimentation with +controlled conditions was necessary. + +It was necessary, first, that the place in which the experiments were +performed should be guarded against sources of error and interruptions. +Several difficulties stood in the way of the removal of the horse to a +more convenient place. Therefore, a large canvas tent was erected within +the courtyard of Mr. von Osten. This afforded the necessary isolation +without hindering the free movements of the horse. After the essential +part of the experiment had been completed and the problem had been +practically solved, experimentation was sometimes conducted in the open +courtyard. A number of the experiments were also performed in the +horse's stall. + +The choice of proper persons to experiment with the horse required +careful consideration. In so far as observations were to be made upon +the questioner, Mr. von Osten was of course indispensable. But to +obviate every objection he, as well as Mr. Schillings, had to be +excluded from the greater part of the experiments, and other persons +had to be selected who could learn to handle the horse. Now one would +have thought that the horse would respond to any moderately efficient +examiner. But as a matter of fact it was found that the horse would not +react at all in the case of the greater number of persons. Again, in the +case of others he would respond once or twice, but would then cease. All +told, Hans responded more or less readily to forty persons, but it was +only when he worked with Mr. von Osten or with Mr. Schillings, that his +responses were at all dependable. For this reason I undertook to +befriend the horse, and by happy chance it came to pass in a short time +he responded as readily to my questions as to those of the two +gentlemen. In a few of these experiments the Count zu Castell, Count R. +von Matuschka and Mr. Schillings undertook the role of questioner. Where +these are not mentioned in the results here published, I myself did the +questioning. + +With regard to the number of experiments and their performance, the +following precautions were observed. A sufficiently large number of +tests was made in each series in order to obviate the possibility of the +contention that the horse's errors were due to chance. The conditions of +experimentation were such that the further contention that he happened +to be tired or otherwise indisposed, whenever the reactions seemed to be +inadequate, could not be offered. The possibility of confusing the horse +by means of unwonted conditions also had to be avoided. For this reason +it was necessary to alternate the trial in which procedure was with the +knowledge of the answer on the part of the questioner, with the trial in +which the procedure was without such knowledge. Such precautions had +hitherto been neglected, and therefore those negative results which had +been occasionally obtained in single trials, could not claim objective +validity, even though the persons making the tests were subjectively +convinced. + +The course of the experiments was determined by the nature of the +problem itself. By means of a very simple test it was possible to +discover whether or not Hans was able to think independently. He was +confronted with problems in which the procedure was without knowledge of +the answer on the part of the questioner. If under these conditions he +could respond with the correct answer--which could be the result of a +rational process only--then the conclusion that he could think +independently, was warranted. The examination would be closed and Mr. +von Osten would be justified in all he claimed for the horse. If, +however, Hans should fail in this test, then the conclusion that he +could think was by no means warranted, but rather the inference that he +was dependent upon certain stimuli received from the questioner or the +environment. Further investigation would be for the purpose of +discovering the nature of these stimuli. + +To ascertain by means of which sense organ or organs the horse might +receive these necessary stimuli, the method of elimination was employed. +We began by excluding visual stimuli by means of a pair of very large +blinders. Should this investigation be without results, then we would +proceed to test the sense of hearing. The elimination of auditory +stimulations would be more difficult, because ear-caps or the closing of +the passage by means of cotton would not give sufficient assurance that +the sound-waves were being interrupted, even if the horse were docile +enough to suffer these appliances. Thereupon would follow the testing of +the sense of smell and of the skin-senses. And finally there might be +involved another still unknown sense, such as seems to exist in the +lower animal-forms. The reader therefore can readily see that the +investigation might possibly have become very complex, and that the +investigator had to be prepared for all of these possibilities. + +The results of the experiments and the essential circumstances under +which they were conducted, were in every case recorded immediately. + +It goes without saying that in the final formulation of the results, all +values--including those which were not consonant with the majority--were +to be used. + + +B. EXPERIMENTAL RESULTS + +During the course of these experiments Hans wore his accustomed +trappings, i. e., a girdle, light headgear and snaffle, and he either +stood alone, untied, or was held loosely by the bridle either by the +questioner or (though only in a few instances) by his attendant. The +questioner always stood to the right of the horse, as Mr. von Osten had +been accustomed to do. As reward for correct responses Hans received +from the questioner[G]--and from him only--a bit of bread or carrot, and +at times also a square of sugar. Never was a whip applied. From time to +time the horse was led about the courtyard or was allowed to run loose +in order to secure the needful respite. Besides myself there was usually +present Prof. Stumpf and Dr. von Hornbostel, who kept the records, and +frequently also Mr. von Osten. Several times I worked alone with the +horse. The results obtained in the horse's stall were in no respect +different from those got in the course of the experiments carried on in +the courtyard. Whenever a doubt arose as to the number of taps made by +the horse (though this did not frequently occur), then the series in +question was immediately repeated. + + [Footnote G: The expressions _questioner_ and _experimenter_ are used + interchangeably in this treatise.] + +In this report of the results of our experiments, the reader must bear +in mind that it was impossible to adhere to that order and distribution +of tests which we are wont to require in the case of psychophysical +experiments conducted under regular laboratory conditions. All sorts of +difficulties had to be overcome: unfavorable weather, the crowds of +curious ones, certain peculiarities of the horse--such as shying +whenever the wind rippled the canvas of the tent--and last but not +least, the idiosyncrasies of Mr. von Osten who repeatedly attempted to +interrupt the progress of the experiments. + +Since it was evident that different kinds of processes were involved in +solving the problems and since the solutions would be indicated by +tapping, or by movements of the head, or by walking over to the object +to be designated, the results of these three sets of experiments have +been grouped under three corresponding heads. + + +_I. Problems solved by tapping_ + +The following tests were made in which the method was such that when the +problem was presented to the horse, the correct solution was known to +none of those present, least of all to the questioner. This method we +shall designate in the following report as "procedure without knowledge" +whereas we shall call the method in which the answer was known to the +questioner, "procedure with knowledge". + +In order to discover if the horse could read numbers, a series of cards +on which numerals were blazoned, were exposed to the horse's view in +such a way that none of those present was able to see them, and the +horse was asked to tap the numbers as they were shown. This experiment +was repeated at different times and in all there were 49 tests in which +procedure was without knowledge, and 42 in which procedure was with +knowledge. In the case of the former there were 8% correct responses, +whereas in the case of the latter 98% of the answers were right. As an +example of the course which the series tended to take, we insert the +following, in which Mr. von Osten himself acted as questioner. + + Method. No. exposed. No. tapped. + + Without knowledge 8 14 + With " 8 8 + Without " 4 8 + With " 4 4 + Without " 7 9 + With " 7 7 + Without " 10 17 + With " 10 10 + Without " 3 9 + With " 3 3 etc. + +Whenever the questioner knew the solution, nearly all of the horse's +answers were correct; but when the answers were unknown to the +questioner, the horse's responses were, with only a few exceptions, +quite unsuccessful. Since the few exceptional cases must be regarded as +fortuitous, the conclusion is warranted that the horse was unable to +read numerals without assistance. + +In order to discover whether the horse could read words such as "Hans" +or "Stall" or the names of colors, they were written upon placards and +hung up in a row before the horse in such a way that the questioner +could see the individual word but could not immediately recognize the +particular place that each one occupied in the series. The horse was +then asked: "Upon which placard is the word 'Hans'?", "On which is the +word 'Stall'?", etc. In order to make sure, he was required to repeat +each answer. + +Then the experimenter would determine for himself the place of the word +in the series and would ask the question again. Fourteen such tests, in +which the procedure was with knowledge on the part of the questioner, +were interspersed with twelve in which the procedure was without such +knowledge. With the latter there were no correct responses, whereas in +the cases of procedure with knowledge 100% of the answers were correct. +Evidently the horse could not read words. + +Three words were thereupon whispered in his ear, which he was asked to +spell in accordance with the method described on page 21. Since he had +to indicate first the row, and then the place in the row occupied by the +letter, it took two answers to indicate the position of each letter. I +acted as questioner. The ordering of the table of letters was unknown to +me, except the position of the letter "a", which naturally came first, +and the place of the letter "s", concerning whose position I had +purposely inquired. The words chosen for this experiment were "Arm", +"Rom" (Rome) and "Hans". The horse responded incorrectly in the case of +every letter which was unknown to the questioner. "A" and "s" alone were +given correctly. Thus in spelling the word "Rom" the horse responded +with the series 3, 4; 3, 4; 5, 4; 5, 4; i. e. "jjst", instead of the +correct series: 4, 6; 4, 2; 3, 7. I later selected three other words, +the spelling of which involved the tapping of thirty-two numbers on the +part of Hans, and whose position I had carefully ascertained beforehand. +When these were given to the horse to spell, he responded promptly +without a single error. Evidently Hans was unable to spell without +assistance of some sort from the questioner. + +The horse's reputed aptitude in computation was tested in the following +way. Mr. von Osten whispered a number in the horse's ear so that none of +the persons present could hear. Thereupon I did likewise. Hans was asked +to add the two. Since each of the experimenters knew only his own +number, the sum, if known to anyone, could be known to Hans alone. Every +such test was immediately repeated with the result known to the +experimenters. In 31 tests in which the method was procedure without +knowledge, 3 of the horse's answers were correct, whereas in the 31 +tests in which the method was procedure with knowledge, 29 of his +responses were correct. Since the three correct answers in the cases in +which procedure was without knowledge evidently were accidental, the +results of this series of experiments show that Hans was unable to solve +arithmetical problems. + +For the purpose of discovering whether the horse could at least count, +the Russian kindergarten device, which Mr. von Osten had used in +training, was utilized. The machine was placed before the horse, but the +experimenter turned his back upon it. Before each test, a number of +balls were pushed to one side and Hans's problem was to indicate the +number thus separated. Each test was repeated with procedure with +knowledge. Of eight such experiments Hans responded successfully every +time procedure was with knowledge but failed every time procedure was +without knowledge. Thus 7 balls were at one time designated as 9 and +later as 14, while 6 were at first designated as 12, and later as 10. +Since all these errors could not be accounted for on the ground of +miscounts on the part of the horse, it was evident that Hans is quite +unable to count. + +The memory-test was conducted in the following manner. In the absence of +the questioner a number or the name of some day of the week was spoken +to the horse. The experimenter would then return and question him. Of 10 +responses 2 were correct, 8 incorrect. Among the correct answers were +the number 3, a number which, as we shall see, Hans was prone to give +under all sorts of conditions, and which therefore meant very little +when given as a correct response. The number 2, on the other hand, was +consecutively indicated by 7, 9, 5, and 3, 8 was given as 5, 6, 4, and +6, consecutively; and finally Wednesday was indicated as the fourteenth +day of the week. After this we undertook the test the horse's far-famed +knowledge of the calendar. Dates, such as Feb. 29, Nov. 12, etc., were +given to Hans and he was asked to indicate on which day of the week they +fell. Sunday was to be indicated by 1, Monday by 2, etc. Of 14 such +tests, 10 were unsuccessful, 4 successful. But in the case of these 4 +something very interesting occurred. It happened that during this series +the keeper of the horse was present, and he happened to know the days on +which these dates fell,--as he himself testified. The dates in question +were also little more than a week or so from the day of the experiment, +so they could easily be determined. But as soon as we took more remote +dates both man and beast were hopelessly lost. It was certain that Hans +had no knowledge of the calendar. It is needless to say anything of his +supposed knowledge of cards and coins. Hans plainly was incapable of +the astonishing feats of memory which had been claimed for him. + +Finally we investigated Hans' musical ability. In a room adjoining the +horse's stall there was a small harmonica, which spanned the once +accented octave. On this one or more tones were played. The horse was +required to indicate the tone played, the number of tones played and +their relation to one another. For testing his general hearing 20 tests +were given in which the method was procedure without knowledge. Of the +responses only one was correct, and that one was the tone e, for which +the proper response was three taps, but we must bear in mind what has +already been said of the number 3. The tone b was indicated by 11 taps, +although Hans had only learned a scale of one octave and therefore could +respond to only seven tones. In the tests in which the method was +procedure with knowledge, he again, without exception, was successful. +Similar results were obtained in the analysis of compound clangs. In the +cases of procedure without knowledge (although the experimenter here +knew the correct responses, he purposely refrained from thinking of +them) not a single response was correct; while in the cases of procedure +with knowledge, all but one were correct. The following were typical +responses: Three tones were played and the question was asked, "How many +tones were played?" Hans responded first with 4 taps and then with 1. +The tones c, e, g, a, (1, 3, 5, 6) were struck and the question asked, +"Which tone must be eliminated to make the complex a chord?" In the +tests in which the method had been procedure with knowledge, this +question had always been answered correctly, but when procedure was +without knowledge the responses were first 13, a tone which does not +exist for Hans, then 2, a tone which was not given in the clang to be +analyzed, and finally 3, which was not the discordant tone. Hans's +far-famed musical ability was an illusion. + +Taking the results of all the tests into consideration, we find that in +the case of procedure with knowledge, 90 to 100% of the responses of the +various series were correct, whereas, in those series of procedure +without knowledge 10%, at most, of the responses were correct. Under the +conditions prevailing during these latter tests, even these 10% must be +regarded as due to chance. To be sure Mr. Grabow, a member of the school +board and an enthusiastic follower of Mr. von Osten (Zeitschrift fuer +Paedagogische Psychologie, Pathologie und Hygiene, Berlin, 1904, Jahrg. +6, Heft. 6, S. 470), mentions a large number of successful tests, which +were supposedly made in accordance with the method of procedure without +knowledge. A thorough analysis of his experiments was not possible, +because the conditions under which they were conducted were not +adequately specified. But I have no doubt that the successful responses +of the horse were due solely to the absence of precautionary measures. +I, too, could cite a number of seemingly correct responses which +demonstrably were due to the absence of adequate precautionary measures. +I therefore repeat: Hans can neither read, count nor make calculations. +He knows nothing of coins or cards, calendars or clocks, nor can he +respond, by tapping or otherwise, to a number spoken to him but a moment +before. Finally, he has not a trace of musical ability. + +After all this experimentation it was evident that the horse was unable +to work alone, but was dependent upon certain stimuli from its +environment. The question therefore arose: does the horse get these +stimuli while the question is being put, or during his responses, i. e., +during the process of tapping. + +If Mr. von Osten's opinion was correct, then the process of questioning +played an important part in the success of the experiment. Of course, as +he said, it was not necessary to ask the question aloud; it was +sufficient--curiously enough--that it be inwardly spoken, thanks to the +horse's extraordinary auditory sensitivity. If, however, conditions were +made such that the auditory sense was eliminated, then the animal would +be unable to respond. Such a theory is not quite as absurd as it might +seem at first blush. For Hansen and Lehmann have shown that an acute +auditory organ is able to respond to such delicate stimulation as is +involved in the softest whisper, or even in the so-called nasal whisper +in which the lips are tightly closed.[3] They have attempted thus to +explain any modes of supposed "thought-transference", (cf. page 7). +Since experts on horses agree that the horse has acute auditory +sensitivity, Mr. von Osten seized upon this fact and tried to establish +his theory in the following manner. No response was successfully made on +the part of the horse, he said, when the sound waves caused by his (Mr. +von Osten's) inner speech were deflected from the ear of the horse. This +was the case when he closed nose and mouth while inwardly putting the +question, or deflected the waves from the horse's ear by means of a +placard held before his mouth while speaking, or finally by applying +lined ear-muffs to the horse's ears. If, on the other hand, he closed +only his nose and not his mouth while thus inwardly putting the +question, or if he held the placard so that there was a possibility of +deflecting the sounds to the horse's ear, or if the ear-muffs were of +too sheer a material, then Hans could hear and answer the questions +which for human ears were inaudible. He demonstrated all this by means +of experiments and of 20 tests of the first kind, in which auditory +sensations were supposedly eliminated, 95% of the responses were +incorrect (Hans would always tap too great a number); whereas of 28 +tests of the second kind, not a single answer was wrong, just as had +been predicted. Now I have repeated both kinds of tests, but have always +found some correct responses in those cases in which the horse, +supposedly, was unable to hear, a thing which greatly astonished Mr. von +Osten. In fact, the responses of the horse were quite as correct when I +did not even whisper the question inwardly. It was quite clear that +putting the question in any form whatever was wholly unnecessary. Mr. +von Osten's demonstrations to the contrary, which were based upon +erroneous physical principles, are to be explained as cases of vivid +autosuggestions, (but of this, more in Chapter V). After all this +experimentation, it was manifest that the cue was not given to the horse +while the question was being put; it occurred, therefore, at some time +during the process of tapping. But by means of which sense organ was it +received by the horse? + +We began by examining the sense of vision, and in the following manner. +Blinders were applied, and it is worthy of mention that Hans made no +attempt to resist. The questioner stood to the right of the horse, so +that the animal knew him to be present and could hear, but not see him. +Hans was requested to tap a certain number. Then the experimenter would +step forward into the horse's field of vision and would put the same +problem again. Since, in the tests of the first kind, Hans would always +make the most strenuous efforts to get a view of the questioner, and +since he would rave and tear at the lines whenever the attempt was made +to tie him,--a thing which he had never done hitherto,--it was +impossible to determine in some cases whether or not he had seen the +questioner during the process of tapping. I am using, therefore, in the +following exposition, besides the two categories of "not seen" and +"seen", a third which I have called "undecided". A total of 102 tests +were made in which large blinders were used. In 35 of these, the +experimenter certainly was "not seen" in 56 cases he was "seen" and the +remaining 11 are "undecided". Under the first of these categories 6% of +Hans's answers were correct (i. e. only two), under the second head 89% +were correct and under the third 18% were right. In other words, the +horse was at a loss the moment he was prevented from seeing the +questioner; whereas his responses were nearly always correct when the +experimenter was in sight, certain proof that the horse's failures are +to be attributed to the elimination of visual stimuli and not to the +general inconvenience occasioned by the blinders. It is evident +therefore, that the horse required certain visual stimuli or signs in +order to make a correct response.[H] + + [Footnote H: Throughout this treatise I am using the word "sign," or + "signal," whereas all other writers who have touched upon the + Hans-problem, have always spoken of "aids." Following von Sanden,[4] + however, I would distinguish clearly between the two. I would + designate as aids all immediate stimulations of the horse's body (i. + e. by means of contact), which have been designed with reference to + the animal's physiological movement-mechanism in such a way that + they truly 'aid' him in the production of the required movements. I + would regard as signs on the other hand, all stimulations (whether + mediate or immediate) which are selected without especial regard to + the anatomy or physiology of the horse, and bear no inseparable + relation to the thing to be done but are associated with it at the + will of the trainer. The rider's use of reins, and control by means + of leg-pressure and manner of sitting in the saddle, and the + driver's use of the lines,----all these, then are aids. A simple + pull at the reins, however, is not an aid, but a sign. The whip may + be used for giving signs as well as aids,----the latter, when it + does the work of the spur or of the pressure with the knees, as is + the case with ladies' riding-horses and in lunging. All calls and + all movements of the hand or head merely, on the part of the + trainer, are to be regarded as signs.] + +Such unequivocal results, however, were only obtained after we had +provided blinders of sufficient size (15 x 15 centimeters). Mr. von +Osten believing that the horse would not suffer these to be applied, had +at first proposed other measures. He held a slate before his face. Some +of the horse's responses were right, others wrong. The tests were +repeated and were successful as long as I, myself, held the slate before +my face, but not a single one of the responses was correct when another +would attempt to hold the slate before me. Mr. von Osten then brought +forth a kind of bolster which he fastened on the right side of the +horse's face,--the side which was turned toward the questioner. But this +also gave uncertain results. Finally he agreed to apply blinders. But +these were much too small and projected at a great angle from the head +(Mr. von Osten had cut the straps, for he thought they worried the +animal). The result was that only the posterior part of the horse's +normal field of vision was obstructed. Therefore, one could never be +quite sure whether Hans, who--it will be borne in mind--made every +attempt to see the questioner, had not perhaps after all been able to +peer over the edge of the blinder. The number of "undecided" tests, +therefore, became very great. Of 108 tests, only 25 could be placed in +the category of "not seen", 44 in the "seen", and 39, i. e., a third of +the total, in the "undecided." The percentage of correct answers for +these three categories were, respectively: 24%, 82% and 72%. Here we +have once more approximately the same ratio between the categories of +"seen" and "not seen" as in the case of the tests with the smaller +blinders. If we were to count the cases which we had put under the head +of "undecided," in the same category as those in which vision had been +excluded--as Mr. von Osten had done--then one would have been led to the +conclusion that the horse did not need visual signs. Several observers +had thus been led astray: e. g., General Zobel writes in the +"National-Zeitung" (Aug. 28, 1904), that upon request Mr. von Osten had +covered Hans's right eye "by means of some sort of blinder, so that he +was unable to see his instructor", and that Hans did not fail to respond +correctly. We evidently have here to do with the unreliable bolster +mentioned above. Furthermore, Mr. Schillings made a number of tests with +the small blinders, in which 50% of the answers were correct, and +probably in the same manner were obtained the results published in one +of the daily papers (the "Berliner Tageblatt", Dec. 12, 1904), several +days after the publication of the December report, and reading as +follows: "Tests have been made upon Hans with blinders over his eyes and +it is to be noted that, in spite of these, he still responds correctly." +Mention is also made of the experiments noted in Supplement III (page +257), in which Mr. von Osten hid behind the questioner and merely +encouraged the animal by occasional exhortations, but it is not possible +to say with any degree of certainty in how far he was really hidden from +the horse's view. + +I would add that the horse--in so far as it was at all possible to +decide--never looked at the persons or the objects which he was to +count, or at the words which he was to read, yet he nevertheless gave +the proper responses. But he would always make the most strenuous +efforts to see the questioner. (See page 43). I would furthermore add +that several experiments, in which Mr. von Osten and the horse were +separated from each other by means of the canvas tent, failed +completely, and that, on the other hand, all tests were successful in +which the questioner was present in the feed-room and the door between +this and the horse's stall was opened wide enough for him to be seen by +the horse. I would also mention that toward evening the responses became +less and less accurate. The conclusion that visual stimuli were here +operative cannot be gainsaid. + +It was possible, to be sure, that other senses might also be involved, +but it was certain that auditory sensations did not enter it. This is +shown by the fact that one might remain just as silent while the horse +was tapping his answer as during the putting of the question and yet +obtain a correct response. Hans, furthermore, could scarcely be +distracted by auditory stimulations. If either the experimenter or +anyone else present sought, at a given moment, to interrupt him by such +calls as "Halt", "Wrong", etc., while he was going through the process +of tapping, they very seldom succeeded in their attempt. Even though +such interruption did succeed in seven out of the twenty-one cases in +which it was tried, the assumption is well grounded that the success was +due entirely or almost entirely to minimal movements involuntarily +executed by those attempting the interruption. It is to such minimal +movements that the horse, as we shall see later, promptly reacted. When +the experimenter (Pfungst), himself, made the interjections, which +certainly should have been more effective, we found that the horse was +actually disturbed in only two of the fourteen cases; and finally in ten +consecutive cases of attempted interruption not a single one was +successful. There was almost a complete absence of any ear movements on +the part of the horse, a fact in which I have been borne out by Mr. +Henry Suermondt, the distinguished horseback rider. Indeed, I cannot +recall that Hans ever turned his ears toward me, a fact which is +strikingly curious in the case of a horse so attentive and so spirited +in temper. + +Finally, I might also mention that the breathing of the experimenter in +no wise influenced the outcome of the experiment. Whether he held his +breath or breathed on the leg or body of the horse, made no difference. + +Investigations of the other senses became needless, for I had, in the +meantime, succeeded in discovering the essential and effective signs in +the course of my observations of Mr. von Osten. These signs are minimal +movements of the head on the part of the experimenter. As soon as the +experimenter had given a problem to the horse, he, involuntarily, bent +his head and trunk slightly forward and the horse would then put the +right foot forward and begin to tap, without, however, returning it each +time to its original position. As soon as the desired number of taps was +given, the questioner would make a slight upward jerk of the head. +Thereupon the horse would immediately swing his foot in a wide circle, +bringing it back to its original position. (This movement, which in the +following exposition we shall designate as "the back step", was never +included in the count.) Now after Hans had ceased tapping, the +questioner would raise his head and trunk to their normal position. This +second, far coarser movement was not the signal for the back-step, but +always followed it. But whenever this second movement was omitted, Hans, +who had already brought back his foot to the original position and had +thereby put it out of commission, as it were, would give one more tap +with his left foot. + +If it was true that these movements of the questioner guided the horse +in his tapping, then the following must be shown: First, that the same +movements were observed in Mr. von Osten in every case of successful +response; secondly, that they recurred in the same order or with only +slight individual changes in the case of all who were able to obtain +successful responses from the horse, and that they were absent or +occurred at the wrong time in all cases of unsuccessful response. +Furthermore, it was observed that it was possible to bring about +unsuccessful reactions on the part of the horse as soon as the movements +were voluntarily suppressed, and conversely, that by voluntarily giving +the necessary signs the horse might be made to respond at pleasure; so +that anyone who possessed the knowledge of the proper signs could +thereby gain control over the process of response on the part of the +horse. These requirements have all been fulfilled, as we shall see in +the following pages. + +With regard to the regular recurrence of the movements noticed in the +case of Mr. von Osten, I was, after some practice, able to note +carefully their peculiar characteristics. This was rather difficult, not +only on account of their extreme minuteness, but also because that very +vivacious gentleman made sundry accompanying movements and was +constantly moving back and forth. To abstract from these the essential +and really effective movements was truly difficult. It was much easier +to observe these movements in the case of Mr. Schillings, probably on +account of the fewer accompanying movements and perhaps on account of +their greater distinctness. Usually he would raise the entire trunk a +trifle, so that the movements could be noticed from behind. Besides +these, I had an opportunity to observe the Count zu Castell, Mr. Hahn +and the Count Matuschka. All three made the same movements, though +somewhat more minutely than Mr. Schillings, yet none was as slight as +those of Mr. von Osten.[I] I further noticed that Count Matuschka and +Mr. Schillings often showed a tendency to accompany every tap of the +horse with a slight nod of the head, the last being accompanied by a +more pronounced nod and then followed by the upward jerk of the head, in +other words, they beat time with the horse. In the case of the last +three mentioned, for whom the horse responded far less effectively than +for Mr. von Osten or Mr. Schillings, belated or precipitate jerks would +frequently occur. This was found to be true in the case of all other +persons who had failed to elicit adequate responses from the horse. +Often, in both cases, a complete absence of any kind of minimal movement +had been noted. The accuracy of these observations in the case of Mr. +von Osten is attested by Mr. Stumpf and Mr. von Hornbostel, and by these +same gentlemen and Prof. F. Schumann in the case of Mr. Schillings and +myself. They also found these movements to be most minute in the case of +Mr. von Osten. In my case also they pronounced them "minimal, and often +quite imperceptible". All other persons who have seen me work with the +horse, but who were not familiar with the nature of these movements, +never perceived them, no matter how closely they observed me. + + [Footnote I: During the tests Mr. von Osten nearly always wore a + slouch hat with a wide rim. The rim, of course, always moved with + the head, and made the movements appear on a larger scale, (in the + ratio of about 3:2, as I was able to ascertain later by graphic + methods). But observation was successful, even at a distance of a + meter and a half, when he worked with head uncovered. And even if + head and forehead were covered entirely, it was still possible to + note the movements by watching the eye-brows. When Mr. Schillings + and the rest of us worked with the horse, we either went bare-headed + or wore only a very small cap.] + +Since the doubt was expressed that these movements did not precede but +followed closely upon the back-step of the horse (i. e., that an error +with regard to the time-element was involved), it became important that +time measurements be taken. This was done in the following manner: The +questioner asked the horse to tap numbers from 5 to 20, seldom higher. +He purposely refrained from pronouncing the number, but recorded it +after each test had been completed. This was a matter of indifference to +the horse (see page 42), and had the advantage that the measurement was +not influenced by knowledge on the part of the time-keeper. Two +observers were required, one watching the horse, the other the +questioner. Both observers had fifth-second stop-watches. The larger +face of this watch shows the fifth-second and a hand on the smaller face +indicates the minute. By pressing upon the stem the watch may be set in +motion at any moment desired, and by pressing it once more it may be +instantly stopped, and the time elapsing between the setting in motion +and the stopping may be read on the face. By pressing upon the stem a +third time the hands are brought back to zero, and the watch is ready +for another test. At a moment agreed upon beforehand--usually the third +tap of the horse--both observers started their watches. Practice tests +had shown that this could be done with all the accuracy necessary in +this case. As soon as the observer of the questioner noticed the +latter's head movement he stopped his watch, and as soon as the observer +of the horse noticed the latter's back-step he stopped his watch. Since +the movement of the horse's foot does not occur as a jerk, but is of +greater extent than a jerk would be, it was agreed that the observer was +to stop the watch as soon as he recognized the back-step as such, not +when the foot was being raised from the ground, because it was not then +evident whether the horse would bring it back to the original position +or whether he was preparing to give another tap, nor when he had brought +his foot completely back, but at the moment in which it was evident that +the horse intended to make the back-step. Experimentation had shown that +an agreement as to this moment was possible. A tap with the left foot, +which might possibly follow upon the back-step, could be left out of +account. The difference in time between the two watches would show the +time between the head-jerk of the questioner and the back-step of the +horse,[J] and if the back-step was indeed a reaction upon the +head-jerk, then the watches would have to show a later time for the +back-step than for the head-jerk. + + [Footnote J: For the benefit of those who are familiar with + reaction-time experiments of this kind, I would state the following: + The reaction to the head-jerk, on account of the minuteness of the + latter, was sensory throughout, and therefore all precipitate + reactions are entirely wanting. The reaction to the back-step was, + like the preceding one, a reaction to a visual cue. (Hans's tapping + was almost quite inaudible). Both stop-watches were carefully + regulated. In order to eliminate also the constant error which might + possibly arise as a result of some difference in the functioning of + their pressure-mechanism, the two watches were always exchanged in + the different series of tests, by the observer of the man and the + observer of the horse. The two time-measurements obtained by the two + observers contained, of course, the reaction-times of the observers + themselves. In order to equalize the constant error which thereby + arose, it was arranged that each observer should react alternately + now to the man, now to the horse. In order to be perfectly safe, the + reaction-times of those concerned, (von Hornbostel, Pfungst, + Schumann and Stumpf), were later determined in the laboratory by + means of the carefully regulated Hipp chronoscope. Separate + determinations were made of the reactions to the head-jerk and to an + imitation of the horse's back-step. Then the time which one observer + took to react upon a head-jerk, was compared with the reaction-times + of the other observers to the back-step. Since the greatest + difference which was found in this comparison, did not exceed + one-tenth second, the results obtained in the courtyard required no + correction.] + +Measurements of this kind were taken for Mr. von Osten, Mr. Schillings +and myself. In the case of the first two it was taken without any +knowledge on their part. They did not even know that they were being +observed, having been told that the measurements were for the sake of +determining the horse's rate. In my case, to be sure, the time could not +be taken without my knowledge. I succeeded, however, in eliminating the +effect of this knowledge on my part. (Cf. pages 88 and 145.) Since the +results obtained in the case of Mr. Schillings quite agree with those +obtained in my case, it is evident they may be considered as being of +equal value. + +With regard to the number of tests the following table may be referred +to. The first vertical column gives the name of the questioner, i. e. +the person operating with the horse. The four other columns give the +number of tests made upon each of these. The name of the person who made +the observation in each series is indicated at the head of the column. +It is unnecessary to give the name of the observer of the horse, for the +only difficulty lay in the observation of the questioner. The numerals I +and II indicate two series taken at different times. + + -----------------+----------+----------+----------+---------- + | v. H. | Pf. | Schu. | St. + -----------------+----------+----------+----------+---------- + Questioner. | I II | I II | I II | I II + -----------------+----------+----------+----------+---------- + v. Osten | 9 15 | 34 17 | - -- | 8 27 + -----------------+----------+----------+----------+---------- + Schillings | - -- | 19 17 | 6 16 | - -- + -----------------+----------+----------+----------+---------- + Pfungst | 6 13 | -- -- | - -- | 9 -- + -----------------+----------+----------+----------+---------- + +We have omitted from this table several tests in which the observer of +the questioner noticed no head jerks whatever, and therefore could not +arrest his stop-watch, although the horse responded correctly. Four +tests of this kind were made by Mr. von Hornbostel, two by Mr. Pfungst, +two by Mr. Schumann and five by Mr. Stumpf. In the case of Mr. Pfungst +the horse gave the unusually high number of fifty taps. The attention of +the observer had been taxed too long and had failed him (two seconds is +the most favorable time). The head-jerk of Mr. von Osten evidently +occurred during a lapse in Mr. Pfungst's attention and therefore +remained unnoticed. + + -----------------+----------+----------+----------+---------- + | v. H. | Pf. | Schu. | St. + -----------------+----------+----------+----------+---------- + Questioner. | I II | I II | I II | I II + -----------------+----------+----------+----------+---------- + R. | 44% 60% | 62% 88% | -- -- | 0% 48% + V. Osten. | | | | + W. | 56% 20% | 12% 0% | -- -- |100% 22% + -----------------+----------+----------+----------+---------- + R. |100% 92% | -- -- | -- -- |100% -- + Pfungst. | | | | + W. | 0% 0% | -- -- | -- -- | 0% -- + -----------------+----------+----------+----------+---------- + R. | -- -- | 74% 100% | 83% 100% | -- -- + Schillings. | | | | + W. | -- -- | 5% 0% | 17% 0% | -- -- + -----------------+----------+----------+----------+---------- + +The results of the experiments are given in the second table. The +general arrangement corresponds to that of the first table. Even though +the absolute number of tests was small, yet for the sake of giving a +better general view, all values are given in percentages. The tests in +which the movement of the questioner had preceded that of the horse--as +had been anticipated--are recorded under "R" (right); under "W" (wrong), +we have recorded those cases in which the testimony of the +stop-watches--contrary to our expectation--indicated that the reverse +order prevailed. Finally, those cases which would complete the 100%, i. +e. those in which the watches indicate simultaneity of the movements in +question, are not recorded. + +From this table we may note the following: The time-measurements for Mr. +Schillings and Mr. Pfungst are quite in agreement and go to show that +the order in time of the head movement of the questioner and the +back-step of the horse was exactly what had been expected. The few +contradictory cases which occur in Series I of the observations upon Mr. +Schillings are to be accounted for by the fact that he was here for the +first time the subject of observation, whereas the recorded +time-measurements in the case of Mr. Pfungst had been preceded by a +number of practice tests. The results of the measurements taken in the +case of Mr. von Osten were far less satisfactory. Even if one were to +allow a series containing barely more than 50% of "right" cases as +sufficient proof of the correctness of our expectation regarding the +order of the movements of the questioner and the horse, only three of +the six series obtained with Mr. von Osten as subject, would satisfy +this expectation. However, since four of the six series show a greater +number of cases of simultaneity (their percentage may be easily deduced +by referring to the per cent of "right" and "wrong" cases), the proposed +method would give a distorted view, and therefore it appears that the +more correct method would be to consider simply the numerical ratio of +the "right" and "wrong" cases. Since, furthermore, Series II shows, in +every case, a decided change which is similar for all observers (note +especially Pfungst), there can be no doubt but that practice is here +involved, and that Series II is to be regarded as the true standard. +Throughout this series we find a preponderance of "right" cases. +Therefore, the table unmistakably confirms the expected order in time. +That there were more "wrong" cases with Mr. von Osten as subject than +with the other questioners is to be explained by the fact that the +decisive movements were far less easily observed in this case, than in +that of the other questioners. (See page 49.) We expect that Series III +would show the same results, or approximately the same results in the +case of Mr. von Osten that it did for Mr. Pfungst and Mr. Schillings, +but unfortunately he declined to act as subject. In the meantime, +however, new and decisive proof presented itself which destroyed all +possible doubt. + +Before adverting to it, let us consider in a few words the reaction-time +of the horse,--the time elapsing between the final sign of the +questioner and the reaction of the horse (i. e., the back-step). +Unfortunately this time cannot be directly determined. All that can be +ascertained from our time-measurements, is the time intervening between +the moment of the head-jerk and the moment in which the reaction of the +horse is noted. (See page 51). This time averaged, for the 127 +measurements, .45 seconds. If we stated the unavoidable error, (obtained +on the basis of extended supplementary measurements which it is not +necessary to consider here) as .15 seconds, and apply it to the value +found above, we obtain .3 seconds as the probable reaction-time of the +horse.[K] + + [Footnote K: See page 126 on the corresponding reaction-time in the + case of man. Similar tests have been made in the case of animals in + only one instance, and that for dogs, by E. W. Weyer.[5] But, as + might have been expected, they did not yield any satisfactory + results.] + +That the tapping--as well as all other movements of the horse--was +nothing other than a reaction upon certain visual stimuli, was proved +beyond a doubt by the fact that the voluntary execution of the head-jerk +and of other movements--which we will describe in more detail later +on,--brought about all the proper responses on the part of the horse. +Thus, artificial synthesis became the test of the correctness of +analytical observation. + +To elucidate; if the questioner retained the erect position he elicited +no response from the horse, say what he would. If, however, he stooped +over slightly, Hans would immediately begin to tap, whether or not he +had been asked a question. It seems almost ridiculous that this should +never have been noticed before, but it is easily understood, for as soon +as the questioner gave the problem he bent forward--be it ever so +slightly--in order to observe the horse's foot the more closely, for the +foot was the horse's organ of speech. Hans would invariably begin to tap +when I stooped to jot down some note I wished to make. Even to lower the +head a little was sufficient to elicit a response, even though the body +itself might remain completely erect. Of thirty tests made in this +position, twenty-nine were successful. Hans would continue to tap until +the questioner again resumed a completely erect posture. If, for +instance, I stooped forward after having told the horse to tap 13, and +if I purposely remained in this position until I had counted 20, he +would, without any hesitation, tap 20. If I asked him to add 3 and 4, +but did not move until 14 was reached, he would tap 14. Twenty-six such +tests gave similar results. + +The reaction of the horse upon such a signal for stopping showed slight +modifications according to the time which elapsed between the last tap +and the signal for stopping. These modifications, which had hitherto +been paraded as expressions of the horse's psychical power may be +illustrated by the following schematic figures (Figures 1-4). In all of +them the dotted line _c-d_ represents the ground level; _d_ shows where +the horse's right forefoot was located before he began tapping; _a_ and +_c_, respectively, indicate the place to which the foot is lowered +during the process of tapping. The unbroken line gives the direction of +the back-step. + +If Hans, having raised his foot from _a_ to _b_--preparatory to +tapping,--receives the signal at or just before the moment he lowers the +foot, he immediately swings it in a wide circle from _c_ back to its +original position at _d_, (Fig. 1). As a matter of fact _a_ and _c_ +coincide, but are juxtaposed in the diagram for the sake of schematic +utility. This was the usual form of the back-step. + +[Illustration: FIG. 1.] + +If the signal for stopping is given a little after the last tap (Fig. +2), i. e., at the time that the foot is already being raised for another +tap, then the back-step occurs as _a-b-d_. The horse thus gives, at the +moment it receives the signal for stopping, a changed impulse to the +moving foot. The curve, therefore, has a kink at _b_, and the back-step +occurs with seeming hesitancy,--Hans appears not quite certain of his +result. + +[Illustration: FIG. 2.] + +If the signal be given somewhat later still (Fig. 3), i. e., when the +foot is being lowered to complete a tap, Hans is still able to put on +the brakes--as it were--and draw back his foot before it reaches the +ground. The whole process gives the impression that the horse was just +about to make a "mistake" of one unit, but at the last moment had +bethought himself of the correct answer. + +[Illustration: FIG. 3.] + +Finally, if the signal be deferred still longer, it becomes impossible +to prevent the extra tap. The back-step again has the same form as in +figure 1; Hans has made a "mistake" in his answer by one unit too many. + +Conversely, if the head-jerk of the questioner occurs too soon; i. e., +at the moment the horse has raised his foot for the final tap to the +height _b_, (Fig. 4), then the tap is not completed,--but the foot, +without touching the ground, makes the curve _b c_{2} d_, back to its +original position. Hans has again made a "mistake" in his answer,--this +time by one unit too few. + +[Illustration: FIG. 4.] + +All these variations go to show one thing: Hans never knows in advance +which tap is to be the final one. These variations in his reactions +occurred often without having been intended by the questioner. But to +bring them about at will required skill, on account of the shortness of +the time involved in the reaction. + +Whenever the signal for stopping--which we have just discussed--was +followed by the complete erection of the head and trunk, Hans would +definitely cease tapping. If, however, the questioner failed to assume a +completely erect position, or if he stooped forward ever so slightly, +the horse would follow the back-step of the right foot with an extra tap +of the left foot. Besides occurring in tests in which Mr. von Osten +assumed the role of questioner, this fact was also noted when the Count +zu Castell and Mr. Schillings acted as subjects. Since the extra tap +just mentioned was not given like the others with the right foot +forward, but with the left foot upon the spot, it was possible for the +horse to execute it with a greater show of energy. This simulated a high +degree of mental certainty on the part of the horse, as if he wished to +indicate that this was the correct solution of the problem and it would +have to stand. In spite of all this, many errors would creep in. It was +possible to prolong this extra tap and thus make it appear more +dilatory. We need hardly add that henceforth it was within the power of +the experimenter to have the tapping executed entirely with the right +foot or with the final extra tap of the left foot. Hitherto the view had +been current that this lay solely within the pleasure of the horse. + +If the questioner still inclined forward, still remained in the bent +posture after Hans had given the final tap with his left foot, the horse +would immediately begin to tap once more with his right foot, which had, +in the meantime, become ready for further action. If the head jerk was +then made, Hans would bring his right foot back, give the extra tap with +his left foot, then resume tapping with the right and thus continue +until the questioner once more resumed the erect posture. Thus the horse +on one occasion when I wished him to tap 100, gave--contrary to my +desire--the following response; 39 with the right foot, 1 with the left, +24 with the right, 1 with the left, 35 with the right, and 1 with the +left. Later it became possible for me to cause him to tap 1 right, 1 +left, 1 right, 1 left, etc. I could even get him to tap exclusively with +the left foot by standing at his left rather than at his right as had +been customary with his questioners. These taps with the left foot were +executed in a far less elegant fashion than those with the right foot, +and with a great waste of energy. Hans had become a right-handed +individual--as it were--as a result of long habit. + +With regard to the distance at which the experimenter directed the +horse, the following may be said: The usual distance was one-quarter to +one-half meter. This holds for all tests hitherto described. Seventy +tests which were made for the purpose of discovering the influence of +change in distance showed that the reaction of the horse upon the +customary signal of the head-jerk was accurate up to a distance of three +and one-half meters. At a distance of three and one-half to four meters +there suddenly occurred a fall of 60-70% in the number of correct +responses. At a distance of four to four and one-half meters only +one-third of the responses were correct, and at a distance beyond four +and one-half meters there were no correct responses. The greater number +of these tests were made in our presence by Mr. von Osten, who was under +the impression that we were testing the accuracy of the horse's hearing, +whereas we were really testing the accuracy of his perception of +movements. + +With regard to the different positions which the experimenter might +assume with reference to the horse, the following may be noted: The +normal position was to the right of the horse. If the experimenter stood +immediately in front of Hans, the latter's reaction would be just as +accurate, though he would always turn his head and make desperate +efforts to see the questioner, even though he was held in short by the +reins. When a position immediately behind the horse was taken--a +somewhat dangerous proceeding, since Hans would at once begin to +kick--no response could be obtained until he succeeded in turning far +enough around to get the questioner within view. If he was restrained +from turning completely around, he would at least turn his head,--and +always to the right. One might even turn his back upon Hans during the +tests, for the signal for stopping was not obtained from the face of the +questioner, but from a movement of the head. The following incident will +show to what extent the horse had become accustomed to seeing the +questioner in a certain definite position. For a long time I had been +in the habit--without exception--of standing close to the horse's +shoulder. Mr. von Osten, on the other hand, would stand farther back. +When, on a certain day, I assumed the latter position, the horse would +not suffer it, but would move backward until he had his accustomed view +of me. + +Finally we sought to discover by what movements the horse could be made +to cease tapping. We discovered that upward movements served as signals +for stopping. The raising of the head was the most effective, though the +raising of the eyebrows, or the dilation of the nostrils--as in a +sneer--seemed also to be efficacious. However, it was impossible for me +to discover whether or not these latter movements were accompanied by +some slight, involuntary upward movement of the head. The upward +movement of the head was ineffective only when it did not occur as a +jerk, but was executed in a circuitous form,--first upward and then back +again. Such a movement was occasionally observed in the case of Mr. von +Osten. The elevation of the arms or of the elbow nearest the horse, or +the elevation of the entire body was also effective. Even if a placard, +with which the experimenter tried to cover his face, were raised at a +given moment, the horse would make the back-step. On the other hand, +head movements to the right and to the left or forward and back, in +fine, all horizontal movements, remained ineffective. We also found that +all hand movements, including the "wonderfully effective thrust of the +hand into the pocket filled with carrots", brought no response. I might +also change my position and walk forward and then backward some distance +behind the horse, but the back-step would only occur in response to the +characteristic stimulus. After what has been said it is easy to +understand how vain were Mr. Schillings' attempts to disturb the horse +and how naturally he might conclude that Hans was not influenced by +visual signs. Mr. Schillings simply did not know which signs were +effective. + +While the horse could thus be interrupted in the process of tapping by +movements which were executed at the level of the questioner's head, yet +movements below this level had the opposite effect. If Hans showed that +he was about to cease tapping before it was desired, it was possible to +cause him to continue by simply bending forward a trifle more. The +greater angle at which the questioner's trunk was now inclined caused +the horse to increase the rate of tapping. The rule may be stated thus: +The greater the angle at which the body inclined forward, the greater +the horse's rate of tapping, and _vice versa_. It was noticeable that +whenever Mr. von Osten asked for a relatively large number--in which +case he always bent farther forward than in the case of smaller +numbers--Hans would immediately begin to tap very swiftly. Not being +entirely satisfied with these observations, the following more exact +measurements were taken. I asked the horse to tap 20. From 1 to 10 I +held my body at a certain constant angle, at 10 I suddenly bent farther +forward and retained this posture until 20 had been reached. If there +existed a relationship between the angle of inclination and the rate of +tapping, then the time for the last ten taps ought to be less than for +the first ten. Of 34 such tests 31 were sucessful. The following are two +specimen series. + +The first series consisted of ten tests of 15 taps each. In all cases my +head was bent at an angle of 30 deg. to the axis of the trunk, but I +constantly changed the angle of inclination of the trunk. It was not +possible to measure this angle accurately on account of the rapidity +with which the whole test had to be made. I was able, however, to +differentiate between them with enough accuracy to designate the +smallest angle (about 20 deg.) as belonging to Grade I, and the greatest +angle (about 100 deg.) as belonging to Grade VII. By fixing certain points +in the environment, it was possible to get approximately the same angle +repeatedly. The time from the third to the thirteenth tap was, in all +cases, taken by Prof. Stumpf by means of a stop-watch. The tests were +taken in the following order: + + Grade of inclination: I VI II II IV V VI VII + Time for 10 taps: 5.2 4.6 5.0 5.0 4.8 4.8 4.6 4.4 sec. + +From this series it will be seen that in the case of the same angle of +inclination (II and VI were repeated and III was omitted) the same rate +obtained in the tapping. In two other tests I constantly increased the +angle of inclination during the 15 taps, and Hans gradually increased +the rate of tapping accordingly. + +In a second series I had the horse tap 14, five times. I myself took the +time of the taps up to 7 by means of the stop-watch, while Prof. Stumpf +took the time of the taps from 8 to 13. At 8 I suddenly bent forward a +little more and retained this position until tap 13. The results were as +follows: + + Taps 2 to 7 (Pf.): 3.2 2.2-2.4 2.4 2.2-2.4 2.4 seconds. + " 8 to 13 (St.): 2.6 2.0 2.0 2.2 2.2 seconds. + +Such good results, however, were possible only after a number of +preliminary practice tests had been made. The experiment was especially +difficult because the horse was often on the point of stopping in the +midst of a test. This was probably due to some unintentional movement +on my part. In such cases I could induce him to continue tapping only by +bending forward still more, but this effected also, as we have seen, an +increase in his rate of tapping. Such tests, of course, could not give +unambiguous results. + +The rate of tapping was quite independent of my rate of counting. Thus, +if I counted aloud rapidly, but bent forward only very slightly, the +horse's tapping was slow and lagged behind my count. If I counted slowly +but bent far forward, Hans would tap rapidly and advance beyond my +count. Thus we see that his rate of tapping was in accordance with the +degree of inclination of my body and never in accordance with the rate +of my counting, i. e., it was quite independent of every sort of +auditory stimulation. + +Direct observation and a comparison of the records of the time Hans +required in giving to his master responses involving small, medium and +large numbers, with the records of the time which he required to respond +to my questions when I bent only slightly, moderately or very far +forward, proved that the increased rapidity in tapping in the case of +large numbers, which many regarded as an evidence of high intelligence, +(see page 20), was, as a matter of fact, brought about in the way +described. The two series (in each of which the time measured was for 10 +taps) are quite in accord. The horse did not tap faster because he had +been given a large number by Mr. von Osten, but because the latter had +bent farther forward. + +From all this it readily appears why it was possible to cause Hans to +increase his rate of tapping but not to decrease it. To do the latter +would involve a decrease in the angle of inclination of the body. This +would necessitate the erection of the body. As we have seen, this was +the signal to which Hans reacted by ceasing to tap. And as a matter of +fact we never knew the horse to decrease his rate of tapping in the +course of any single test, except in the case of very large numbers, and +then it was probably due to fatigue. Mr. von Osten insisted that Hans +often slowed down toward the end of a test, "in order to obviate +mistakes", but all the tests in which he tried to demonstrate this to +us, were unsuccessful. In spite of all exhortation, Hans would tap +either uniformly or somewhat more rapidly as soon as his master--in all +probability unconsciously--bent somewhat lower. Only once was such a +test successful. Mr. von Osten--upon our request--asked the horse to +give a certain large number. In this instance the decrease in the rate +of tapping was due to fatigue and had nothing whatever to do with the +desire on the part of the horse to avoid error. Furthermore, Mr. Hahn, +who had visited Hans twenty times and had made careful notes of his +observations, corroborated my statement when he said that he himself +never noted the decrease in rate mentioned. Contrary statements may +perhaps be due to the fact that the tense state of expectancy on the +part of the observer made the interval between the last taps appear +subjectively somewhat longer. + +So much for the technique of the tapping. Now a word about the numbers +which Hans tapped. (I refer only to the results obtained in series which +involved no volitional control). The number 1 was very difficult to get. +Hans usually tapped 2 instead. Thus even in the case of Mr. von Osten he +responded five times with 2, and only in the sixth test did he react +correctly. As far as other questioners were concerned, 1 was seldom +ever obtained, except in the case of Mr. Schillings and myself. The +numbers 2, 3 and 4, on the other hand, were very easily obtained and, +above all, 3 seldom failed. 3 seemed to be the horse's favorite number +and was very frequently given instead of other numbers. Thus, one-sixth +of all the horse's incorrect responses which were given to me were in +terms of the number 3. The numbers 5 and 6 were a little more difficult +to obtain and above 10 the difficulty increased rapidly. Indeed, I never +saw Hans respond with a number exceeding 20 to any questioner, Mr. +Schillings and Mr. von Osten excepted. I saw the nine vain attempts of +Count zu Castell to get the number 15, and Count Matuschka's eight +unsuccessful attempts to obtain the number 16 as a response. But even +with Mr. von Osten and Mr. Schillings such failures were not infrequent. +Thus, Mr. von Osten tried five consecutive times to obtain the number +24. I myself did not fare any better at first. But the following table +shows what practice can do. If we compare the percentage of correct +responses (involving the numbers 1 to 7--for which alone I have +sufficient material, viz., 80 to 100 cases), obtained in the first half +of our tests, with that of the second half, we get the following: + + For number: 1 2 3 4 5 6 7 + In first half of tests: 49, 92, 89, 86, 74, 62, 53% + " second " " " : 92, 95, 92, 98, 97, 86, 96% + +From this we see how hard it was at first to get the number 1 and that +failure was as frequent as success, and how much easier it was on the +other hand to get the numbers 2 and 3 (and which, therefore, do not show +any great improvement in the second half of the tests). Beyond the 3 the +percentage of correct responses decreased and the number 7 stood at the +same level as the number 1. In the second half of the tests, all these +differences disappeared and errors were infrequent and seldom exceeded ++1 or -1. These results of practice are not to be accredited to the +horse, but to the experimenter, who was at first quite unskilled. This +difference in results does not appear in the case of Mr. von Osten, for +his initial practice had been had many years previous. The values +obtained in his case were very constant throughout our experimentation +and generally showed something like 90% of correct responses. To be +sure, in his case also, the number 1 was somewhat unfavorable, (79% were +correct responses). But the percentages obtained in his case showed no +improvement whatever throughout our experimentation. We need scarcely +add that with the voluntary control of the giving of the signs, in the +case at least of such small numbers as are here discussed, no errors, +whatever, occurred. + +We have discussed the influence of the experimenter, i. e., the one who +asked the horse to tap; now let us consider the influence of others +present upon the horse. + +As a general rule, other persons had no effect upon the horse's +responses. This appears from the failure of nearly all tests in which +all of those present--with the exception of the questioner himself--knew +the number which the horse was to tap. Even when the others concentrated +their whole attention upon the number, it profited little as a close +analysis of the 136 cases, which belong under this head in our records, +go to prove. Thus, in the presence of a group of twenty interested +persons--during the absence of Mr. von Osten--twenty-one problems were +given to the horse, the solutions of which were known to everyone but +myself, the questioner. Result: only two correct responses. Only when +there was among the spectators someone to whom the horse was accustomed +to respond or one from whom he regularly received his food, would such +an influence be effective.[L] But such cases were few. The most +important were the following: I at one time whispered a number to Hans +(on the occasion of the tests mentioned on page 37), and Mr. von Osten +asked for it the moment I stepped aside. Hans answered incorrectly even +though I stood close beside Mr. von Osten; I did not, however, think +intently of the number. As soon as I concentrated my attention upon the +number he promptly responded correctly. Further cases are those +mentioned on page 38, in which the keeper of the horse unintentionally +aided in giving four dates which were unknown to all others present, +including the questioner. This single instance shows the necessity of +the rule that during tests in which the method is that of procedure +without knowledge the solutions should be known to no one of those +present. Finally the tests made by the September-Commission and reported +in Supplement III (page 255) may possibly belong under this head. Since +they were not followed out any further, I am unable to render a definite +judgment upon them. In most of these tests the question itself, as put +by Mr. von Osten, was not adequately answered, but curiously enough, +however, the number which had been given to Hans in von Osten's absence +and which formed the initial number of some mathematical operation, was +tapped correctly. This may possibly be explained by the assumption that +this initial number had been retained in the memory of some of those +present, (see page 149, on the "perseverative tendency"), and that the +horse, since he had been working with some of them, responded to one of +those present. Chance may have played some part also. + + [Footnote L: Mr. Schillings, however, did succeed in making a number + of tests with the co-operation of others who had never before worked + with the horse. These tests were made under the following + conditions: The horse was standing in his stall, when Mr. Schillings + and another gentleman approached him. There was no one else present. + Mr. Schillings, who tried to remain as passive inwardly, as + possible, asked his partner to think consecutively of different + numbers between one and 20, which thus were known to him alone. Hans + was then commanded by Mr. Schillings to tap the numbers, which he + did, to the great astonishment of the men, and especially of Mr. + Schillings. In like manner Mr. Sander, a staff physician in the + marine, received--so he writes me--three correct responses to four + questions which he put to the horse. It happened also in the case of + two scientific men and finally, too, in my own case when I first + came in contact with the horse, (see page 88). The horse's reaction + was brought about in the same way in every one of these instances. + Mr. Schillings, in bending forward slightly, thereby started the + horse a-tapping, and his companion--just as innocently--interrupted + the process by means of a movement of his head, when the right + number of taps was reached. + + I later tried similar experiments together with Mr. Hahn. I was + aware of the answer to the riddle at the time, but he was not. Mr. + Hahn stepped in front of the horse and thought intently of certain + numbers. I did the questioning, that is, I got the horse to tap. In + twelve tests Hans responded correctly in only two instances. In the + ten others he always tapped beyond the number Mr. Hahn had in mind, + e.g., 21 instead of 2, and was evidently awaiting a movement on my + part. When we exchanged roles, Mr. Hahn doing the questioning and I + doing the "thinking," the horse would not respond at all, although + as a rule Mr. Hahn had been fairly successful in working with him + alone. I had gradually gained so much influence over the horse, that + he would scarcely attend to any one else when I was about--Mr. von + Osten hardly excepted. + + In this connection I would prefer to avoid the term "rapport," which + may rise in the minds of many, since it has been used so much in + connection with the phenomena of hypnotism, for I would not obscure + a fact that is clear by giving it a name that is vague.] + +If the questioner knew the number of taps desired, (which was not the +case with the tests hitherto discussed), then the environment had still +less influence upon the horse--except that it caused occasional +interruption. The horse's responses, therefore, did not tend to become +more successful just because a number of persons were simultaneously +concentrating upon the result desired. This was proven by the +experiments which we repeatedly made for this purpose. Only one person +at a time had any influence upon Hans. If two questioners tried to +influence the horse at the same time,--other conditions being the +same,--success would be for the one who had the greater control over the +animal when working alone with him. Prof. Stumpf and I made the +following experiment. Both of us stood to the right of the horse, each +thinking of a number. In ten such tests Hans always tapped my number. +When Stumpf concentrated upon 5 and I upon 8, the horse responded with +8, i. e., the larger number. When Stumpf had 7 in mind, and I had 4, the +response would be 4, i. e., the smaller number. When Stumpf thought of +number 6, and I had fixed upon none, Hans tapped 35. He was evidently +awaiting my signal. When I went away Stumpf again demanded the number 6, +and the horse responded properly. When I returned, Stumpf's attempts +again failed. On another occasion Count Matuschka put a number of +questions, while Mr. von Osten stood behind him. All of the horse's +responses were correct, even the one answering the question: "How much +is 7 times 7?", which was difficult on account of the great number of +taps required. I was able to note from the direction of the horse's eyes +that he was attending only to his master and not to the Count. On still +another occasion Mr. Grabow sang two tones--the second being the fourth +of the first--and asked Hans: "How many intervals lie between?" I was +standing erect before the horse, and was thinking intently of the +number 2, but without giving any voluntary sign of any sort. Hans tapped +2, whereupon Mr. Grabow put a number of similar questions; but I no +longer thought of the answers, and all of Hans's responses went wrong. + +Although Hans was not influenced by others so long as a suitable +experimenter was present, yet he might be disturbed and under certain +conditions might be led to make the back-step in response to certain +movements in his environment. The person to whom he responded would have +to be close to the experimenter and would necessarily have to execute a +movement greater in extent than the experimenter's. In such instances +the raising of the head, arm or trunk, was a sufficient stimulus. Thus +we made the following two series of tests. Mr. Stumpf stood with trunk +bent forward before the horse, and at a moment decided upon beforehand, +assumed an erect position. I myself stood beside Hans and asked him to +tap. When I stood at the horse's neck, then Mr. Stumpfs interruption was +effective. When I stood at the horse's flank, the interruption effected +only a seeming hesitation, and when I moved still farther back, the +horse continued to tap despite any attempted disturbance. In the second +series the questioner remained constantly at the right shoulder of the +horse, while the one who attempted to distract him, changed positions. +When the latter stood to the right immediately in front of or beside the +questioner, the disturbance was effective in 10 out of 13 cases. But +when he stood back of, and to the right of, the questioner, the attempts +at disturbance were seldom successful. If he chose a place before and to +the left of the horse, there was hardly any distraction (in 4 cases +only, out of 13), and if he stood to the left and behind the animal, he +exerted no influence whatever. Hans manifestly turned his attention, +almost exclusively, to the side at which the questioner stood. + +That knowledge of this _modus operandi_ made it possible for those +persons to get responses from the horse, who hitherto had been +unsuccessful, is shown in the case of Mr. Stumpf when he began to +control his movements voluntarily on the basis of observations which had +been made. + + +_II. Problems which Hans solved by movements of the head._ + +We are here concerned with the horse's head movements upward, downward, +to the right and to the left, and also with nodding and shaking of the +head to signify "yes" and "no". We soon discovered that these +experiments, also, were successful without an oral statement of the +problem,--in other words, the auditory stimulus was quite superfluous. +The tests with the blinders showed that Hans was lost as soon as his +questioner was out of his view, but responded adequately the moment the +questioner was in sight. Hans, therefore, had established no idea of any +sort in connection with the terms "up", "down", etc., but in these +cases, likewise, he reacted in response to certain visual stimuli. The +nature of these stimuli I discovered at first in my observations of Mr. +von Osten and also of myself, when working with the horse. + +Above all things it was necessary that the questioner, during these +tests, should stand perfectly erect. If he stooped ever so slightly, the +test was unsuccessful. If he carefully refrained from any movement +whatsoever, and looking straight before him asked the horse, "Which +direction is right?" or "Which way is upward?", Hans would execute all +sorts of head movements without rhyme or reason. It was evident that he +noted that a head movement of some kind was expected of him, but did not +know the particular one that was wanted. But if the questioner now +raised his head, Hans would begin to nod and would continue doing so +until the questioner lowered his head. This reaction was interpreted as +signifying "yes". Mr. von Osten had always asked Hans before each of the +more difficult tests whether he had comprehended the meaning of the +problem, and was reassured only upon seeing the horse's affirmative +response. But contrary to Mr. von Osten's expectation, Hans also +responded in this manner after a pair of ear-caps had been drawn over +his ears. In the case of the tests described at the beginning of the +chapter, in which the method was that of "procedure without knowledge", +Mr. von Osten had always insisted that we await Hans's nod of +comprehension before proceeding. We complied; Hans nodded and--regularly +disgraced himself! + +When the questioner raised his head somewhat higher than normal, Hans +would throw his own upward, which was supposed to signify "upward". A +lowering of the head on the part of the questioner was followed by a +lowering on the part of Hans, which was his form of response for "down". +For some time I was in a quandary as to the difference between the +questioner's signal for this latter response and the one which was the +signal for the horse to begin tapping, although I had often given both +kinds unwittingly. Further experiments showed that Hans responded with a +nod of the head whenever the questioner, while bending forward, chanced +to stand in front of, or to the side of the horse's head, but that he +would begin to tap in response to the same signal, as soon as the +experimenter stood farther back. The difference in the two signals, +therefore, was very slight, and I repeatedly noted that instead of +tapping, as he had been requested, Hans would respond to the Count zu +Castell's and Mr. Schillings' questions by a nod of the head. + +If, while standing in the customary position to the right of and facing +the horse, the questioner would turn his head a little to the right--a +movement which, when seen from the horse's position, would appear to be +to the left,--Hans would turn his head to his left. But if on the other +hand the questioner would turn slightly to the left,--i. e. seen from +the horse's position, to the right,--then Hans would turn his head to +his right. And finally, whenever the questioner turned his head first to +the right, then to the left, Hans would respond by turning first to his +left, then to his right. This, according to Mr. von Osten, signified +"zero" or "no". Since this movement could not be executed by the +experimenter while in a stooping position, it can now readily be seen +why it was that Hans, instead of shaking his head, always began to tap +whenever a placard with "O" upon it, was shown to him in the course of +the experiments in which the method was procedure without knowledge on +the part of the questioner. The latter expected the horse to tap, and +therefore bent forward. Like all of the horse's other forms of response, +this, too, was always unsuccessful whenever the questioner stepped +behind the animal. Although Hans had always responded to Mr. von Osten +and Mr. Schillings, and at first also to me, by means of the stereotyped +movement of the head to the right and then to the left to signify "zero" +or "no", I later succeeded in controlling my signals so as to get the +inverted order in the horse's response. In the case of Mr. Schillings +and of Mr. von Osten all of the movements just described were very +minute, and long after the movements, which were effective stimuli for +releasing the process of tapping, were recognized, it was still +exceedingly difficult to discover them in these two gentlemen. The +signal for "zero" and "no" was relatively the most pronounced of the +group in the case of Mr. von Osten, while with Mr. Schillings it was the +least pronounced, in comparison with his very strong "jerk". Yet in both +cases Hans responded with absolute certainty. + +It is now readily conceivable how it was possible to make the horse +respond to all sorts of foolish questions, both by involuntary signs--i. +e., expressions following upon the bare imaging of the response +expected,--as well as by means of controlled signs. One could thus +obtain consecutively the answers "yes" and "no" to the same question. Or +one might ask: "Hans, where is your head?", and Hans would bend to the +earth. "And where are your legs?" He would look at the skies. Etc. + +Let us examine for a moment the directives which the horse required for +the various positions. If one called him, while he was running about the +courtyard, he paid no attention whatever, but if one beckoned to him, he +came immediately. A raising of the hand brought him to a standstill. If +one now stepped forward or pointed one's hand in that direction, he +would step forward, or _vice versa_, he would step backward. By means of +minimal movements of the head, of the arm nearest the horse, or of the +whole body, Hans could be induced to assume the position one desired, +without touching him or speaking a word. I noticed this quite early in +the course of the investigation. Once, when intending to ask the horse +to step backward to the right, I inadvertently said "Step backward to +the left!", whereupon he stepped backward to the right. In spite of my +verbal error, I had involuntarily given him the proper directives. + +Finally we may note that Mr. von Osten had occasionally asked the horse +to jump or to rear. The command in this case was: "Jump", or the +question was: "What do the horses do in the circus?". Since these tests +were just as effective when the command was given silently, it was an +indication that these, too, depended upon visual stimuli. What was +necessary to cause the horse to step backward and then jump forward was +to step backward oneself, or make a slight movement of the hand in that +direction. If one wished to make him rear, it might be effected by +throwing the arm or head slightly upward. + + +_III. Problems which Hans solved by approaching the objects to be +designated._ + +The method pursued in these tests was the following: From five to eight +pieces of colored cloth 1/2 x 1/4 meters in size were arranged in +changing series upon the ground, the interval between them being equal +to the width of one piece, or else they were hung upon a string a man's +height above the ground. This method was also employed when placards of +like size with written symbols were used. The horse stood ten paces away +and opposite the middle of the series, while Mr. von Osten stood at his +right. Hans was asked to go and point out the cloth of a certain color +or the placard with a certain word upon it. If the cloth lay upon the +ground, Hans picked it up with his mouth and carried it to the +questioner. If the cloth, like the placards, hung from the cord, he +approached, pointed it out with his nose and then backed up to his +original position. Before approaching the objects, Hans was required to +indicate, by tapping, the number of the place in the series (counting +from left to right), which the cloth or placard occupied. Mr. von Osten +never omitted this requirement. Then the command "Go!" was given, and +Hans obeyed. (As a matter of fact, a slight directive movement of the +head or hand was just as effective as the spoken command). + +The following cases, chosen in a haphazard fashion, show that the +horse's indication of the object's place in the series, by means of +tapping, was by no means a guarantee that he would point it out +correctly. Five placards hung from the cord. Mr. von Osten asked: "What +is the position, counting from left to right, of the placard which has +the word 'aber' inscribed upon it?". Hans answered: 3. (It was indeed +the middle placard.) Then he was commanded: "Go!". Thereupon Hans went +straight to the fourth placard. On another occasion Hans happened to +drop a brown cloth upon a black one. His master asked him: "In which +place are there two cloths?". Hans responded correctly, "In the second +place". To the question "Which of the two is the black one?" he also +answered rightly: "The lower one". Upon being asked to get it, he +brought the white cloth. + +The large number and the irregularities of the errors showed that there +was no manner of intelligence involved in the pointing out process. Thus +during the two months of our experimentation Hans was asked twenty-five +times by Mr. von Osten to bring the green cloth. Only six times did he +succeed in the first attempt, while in five instances he selected an +orange-colored cloth, four times a blue, three times a white one. + +The fact that the errors were equally distributed over the tests with +the colored cloths and those with the placards is strong evidence that +the horse's response involved no intellectual process, for if that were +the case, then the responses in the tests with the placards would have +been very much more difficult, for they would have involved the ability +to read, whereas the tests with the colored cloths demanded only that a +few names be remembered. Nevertheless, the horse was as unsuccessful in +tests of one kind as he was in those of the other,--even when Mr. von +Osten acted as questioner. (50% failures in 78 placard tests; 46% +failures in 103 color tests.) + +The fact that commands which were purposely enunciated poorly, or else +not spoken at all, were executed with just as much accuracy as those +given aloud, strengthened us in our supposition. On one occasion I +placed a blank placard with the others. When I ordered him to approach +_tabula rasa_, he invariably went to the right one. The following +illustrates how he fulfilled quite nonsensical commands. A series of +blue and green cloths lay upon the ground. Being asked where the black, +the orange, and the yellow cloths lay, Hans shook his head +energetically, i. e. they were not there. And yet, upon being asked to +bring them in the order named, he regularly brought one of the blue +ones. + +All this goes to show that Hans did not know the names of the colors (to +say nothing of the symbols on the placards). It was plain that here +also, as in all the other cases, he was controlled by signs made by the +questioner, the nature of which I soon discovered. Standing erect, Mr. +von Osten always turned head and trunk in the direction of the cloth or +placard desired. Hans, keeping his eye on his master, would proceed in +that direction. Even after he had already started out, thanks to his +large visual field one could control his direction by turning slightly +more to the right or to the left. If, however, he had already arrived at +the row of placards or cloths, this method ceased to be effective, for +then he could no longer see the experimenter. It made no difference +whether the cloths lay on the ground, or were suspended, like the +placards. + +The following fact justifies the conclusion that the bodily attitude of +the questioner was the effective signal. The more numerous the cloths, +or the nearer they were placed together, the more difficult one would +expect it to be for the horse to select the one indicated by the +experimenter. Such was indeed the case, for the number of errors +increased with the number of cloths presented. + +But no matter how many cloths there might be, or how closely they might +be placed, it was always possible to indicate either end of the row, for +in that case one had merely to turn to the extreme left or the extreme +right, and might even turn beyond the row. Hans seldom failed in these +cases, whereas he made many errors when cloths or placards within the +series were wanted. + +To turn from the nature and number of Hans's errors, to their +distribution,--observation proved the hypothesis that the nearer two +cloths lay together, the greater was the chance of their being mistaken +one for the other. If we designate as "error 1" all those cases in which +Hans went to cloth II instead of to cloth I, cloth III instead of cloth +II, to V instead of IV, etc., and as "error 2" when he mistook III for +I, IV for II, in fine, whenever he went two places too far to the right +or left, and as "error 3" whenever he went three places too far to +either side of the cloth desired, we find the following grouping of +errors: + + With Mr. von Osten, a total of 63 errors: + 73% "error 1" + 21% "error 2" + 4% "error 3" + 1% "error 4" + 1% "error 5" + + With Mr. Pfungst, a total of 64 errors: + 68% "error 1" + 20% "error 2" + 11% "error 3" + 1% "error 4" + 0% "error 5". + +The most frequently recurring error, therefore, was the one in which the +horse, instead of going to the cloth desired, approached the one +immediately adjacent. On page 79 I said that Hans's errors were without +system, but only in so far as it was impossible to explain them on a +basis of the colors which seemingly were mistaken one for the other. A +part of a series in which Mr. von Osten acted as questioner may serve as +an illustration. The order given is that of the experimental series as +it occurred. Five colored cloths were used. + + Color of the cloth + asked for: blue, brown, brown, brown, brown, brown, green, green. + | | | | | | | | + brought: orange, orange, green, green, yellow, green, blue, orange. + + Place of cloth + asked for: V II II II II II III III + | | | | | | | | + brought: IV IV III III I III V IV + +The interpretation of this series which it would be hard to explain by a +reference to the colors which were mistaken, is simply this: Cloths +lying near together were regularly mistaken on the part of the horse. + +Experimental control of the questioner's movements decided the question. +If the questioner at first indicated the proper direction and then +turned about after the horse had already started forward, he was as a +rule misled. When the questioner did not face the cloths at all, but +turned away at right angles, or when he turned his back upon them, Hans +was completely at sea. If, on the other hand, the cloths were arranged, +not in a row, but in several heaps, so that one might turn to a +particular heap, but could not indicate a particular cloth, then Hans +would regularly go to the proper heap, but would always bring forth the +wrong cloth. After much persuasion Mr. von Osten consented to make a +series of these tests himself. Hans's failures were deplorable. He would +take up first one cloth then another, turn again to the first, etc. We +would mention, however, that this apparent searching was not done +spontaneously, but in response to Mr. von Osten's calls, such as "See +there!", "The blue!", etc. Every time Mr. von Osten called, Hans would +drop the cloth he was holding in his mouth, or he would turn away from +the one he was about to grasp, and would then try another one. + +In addition to these visual signs, the horse received auditory signals +in these tests, (as in all others in which he was required to bring +objects). As soon as the questioner noticed that Hans was about to take +up the wrong cloth, all that was necessary to make him correct his error +was to give some sort of an exclamation, such as "Wrong!", "Look, you!", +"Blue!", etc. Hans would pass on as long as the calling continued. If +he was picking up, or about to pick up, a cloth when the exclamation was +made, he would go on to the next; but if, at the time he was on his way +to a certain cloth, he would change his direction in response to the +call. If he stood before one of the pieces at the time, but had not +lowered his head, he would pass on to the next. In all this he would +adhere to a certain routine of procedure. If he was approaching a series +from the right, then a call would cause him to turn to the left, if he +was coming from the left, he would turn to the right. If he had +approached the row of cloths near the center, he would turn, in response +to the questioner's calls, to the left,--seldom, very seldom, to the +right. Mr. von Osten did not seem to be able to control the responses of +the horse, entirely. As a rule, but not always, one call sufficed to +make Hans pass on to the next cloth. If too many calls were given, he +would often go too far. Loud exclamations were superfluous. + +These statements are not mere assertions, but are founded upon the +records of the results. The tests in which calls were made show a larger +percentage of correct responses than do those without calls. Of a total +of 103 tests with colored cloths, which Mr. von Osten performed for us, +only 37% brought forth successful responses on the part of the horse +when visual signs were the only directives and when there were no +directions by means of calls, whereas the total percentage of successful +responses was 54%, if we add to the above those in which the vocal +exclamations helped to bring about success. The corresponding +percentages for the total of 78 tests with the placards were 23% and +50%. In a total of 110 color tests I myself obtained 31% correct +responses under the first head, and 56% under the second head. In a +total of 59 tests with placards I succeeded in getting 31% correct +responses under the first head and 46% under the second head. We must +note that without verbal admonition only one-third of the tests brought +forth correct responses, whereas one-half succeeded when those in which +calls were used, are added. Still, this is a relatively poor showing. In +the most favorable series that Mr. von Osten ever obtained in our +presence--and there was only one such--50% of the responses 'without +admonition' were correct, and 90% when all the correct reactions, both +with and without admonition, were taken into account. + +Not all the places in the row required the same amount of assistance by +means of calls. Those positions which needed the most help, were those +which it was most difficult to indicate to the horse by the visual sign, +i. e., the attitude of the questioner's body. We noted above (page 81) +that the cloths at either end of the row were less difficult to point +out than those nearer the middle. If our hypothesis holds true, we would +expect that the end cloths would involve fewer auditory signals in the +process of pointing out, and those within the row a greater number of +such signs. By way of illustration, I will cite one series of tests in +which Mr. von Osten was questioner, chosen not because it is most +conformable to my hypothesis but because it is the longest (48 +consecutive tests with five cloths) which I have. In the upper row I am +placing the successful responses without auditory signs, in the lower +those involving both auditory and visual signs. + + Place of the cloth : I II III IV V + No. of sucessful } visual signs only : 5 2 1 2 4 + responses. } visual and auditory signs : 5 5 8 5 5 + +We see that without verbal admonition the first and last places are most +favorable for success, the second and fourth far less, and the middle +least favorable. These differences disappear when admonitions are +introduced, for all of the places then have the same number of correct +responses with the exception of the middle, which now has even more than +the others. + +One more experiment which I made will close the discussion. The +following colors were placed from right to left: orange, blue, red, +yellow, black, green. I turned my back upon them, and therefore could +guide the horse by verbal commands only. I asked him to bring the +orange. Hans approached the yellow. I now called three times, allowing a +short interval between the calls. At the first "Go!" he passed from the +yellow to the red, at the second from the red to the blue, and at the +third from the blue to the orange, which he then proceeded to pick up +and bring to me. I had noted this same thing in Mr. von Osten's tests, +although there, there were often other factors entering in. By +exercising the utmost precision in facing the cloths, and by using, in +addition, suitable oral signs, I succeeded in getting Hans to bring, +successively, each one of the six cloths in the row, and without a +single error,--and all this in the presence of Mr. Schillings who did +not have the slightest notion of the secret of my success. + +We need hardly say, in passing, that all that was true of the tests with +colored cloths, was also true of the tests in which the placards were +used. It was all the same to the horse whichever was placed before him. + +We have thus tested all of the horse's supposed achievements. None of +them stood the critical test. It would have been gratifying to have +repeated some of the experiments and to have made Hans the object of +further psychological investigations, but unfortunately he was no longer +at my disposal after the publication of the report of the +December-Commission. Some may say that we have had almost enough of a +good thing, but we must bear in mind that many of the tests which were +carried out,--such as those in which the method was that of "procedure +without knowledge", those in which the ear-muffs were used, those in +which distractions were introduced,--had previously been made by other +persons (see pages 41f, 45, 63), and with other results, than ours. A +more thorough test, therefore, would have been doubly desirable. + + + + +CHAPTER III + +THE AUTHOR'S INTROSPECTIONS + + +In the preceding chapter we asked: What is it that determines the +horse's movements? Independent thinking, or external signs?--We found +that it was solely external signs, which we described as certain +postures and movements of the questioner. Beyond a doubt these necessary +signs were given involuntarily by all the persons involved and without +any knowledge on their part that they were giving any such signs. This +is to be seen from their statements, which cannot be cavilled at, as +well as from the fact that several of them even to-day still doubt the +correctness of the explanation which we are here offering. I myself for +some time made these involuntary movements quite unwittingly and even +after I had discovered the nature of these movements and had thus become +enabled to call forth at will all the various responses on the part of +the horse, I still succeeded in giving the signs in the earlier naive +involuntary manner. It is not easy, to be sure, to eliminate at once the +influence of knowledge and to focus attention with the greatest amount +of concentration on the number desired, rather than upon the movement +which leads to a successful reaction on the part of the horse. To some +this may appear impossible, but those who are accustomed to do work in +psychological experimentation, will not deny the possibility of such +exclusive concentration upon certain ideas. + +If we now ask: "What occurred in the mind of the questioners, while they +were giving the signs?", the answer can be found only by way of the +process which in psychology is technically called "introspection", i. e. +observation of self. In the following we will give the most important +results of this process of self-observation, which took place in the +same period in which the observations recorded in the preceding chapter +were made. + +My first experiments were made while the horse was counting or solving +arithmetical problems and were as follows: Mr. Schillings, who was alone +with me in the horse's barn, asked me to think of several numbers, +maintaining that the horse would be able to indicate them correctly upon +being asked. He stood to the right of the horse, I stood erect and at +the side of Mr. Schillings. There was no one else present. Somewhat +skeptical in attitude, I concentrated my mind consecutively on five +small numbers. Hans tapped one of them incorrectly, one correctly and +three by one unit too many. At the time I considered these attempts as +unsuccessful and credited some curious chance with the answers which +were correct, or nearly so. This was a mistake, for often during the +following days, and in the absence of Mr. von Osten, the horse would +give correct answers. Others, of course, would be incorrect, and usually +the mistakes would be by one unit,--so that I soon saw that even in the +horse's errors there lay some system. It will be seen that Hans +responded to me from the very beginning, undoubtedly because I had had +the opportunity of watching Mr. von Osten and Mr. Schillings and had +thus patterned my behavior after theirs. I was not at first successful +in getting the horse to respond correctly in the case of large numbers. +For in order to get complete control over the horse, and, what was, as +I later discovered, more to the point, control of myself, some practice +was needed. But I was able to work with the horse quite successfully, +while I was still in the dark as to my own behavior. + +From the very beginning Hans responded as promptly to those questions +which I articulated merely inwardly, as to those which were spoken +aloud. That all formulation of the question was unnecessary, however, +was shown by the following experiments. If, for example, I did not think +of any particular number until after the horse had begun to tap, and +then fixed upon 5, he would tap 5. If, however, I told him to count to +6, but gave no further thought to the command after he had begun +tapping, I would get an entirely wrong response. It was easy to obtain +any answer one wished to a question, simply by focussing consciousness, +with a great degree of intensity, upon the answer desired. Thus Hans +answered my question: "How many angles has a hexagon?", first by 6, then +2, then 27, in accordance with the numbers that came into my mind. The +animal always followed the ideas which were in the questioner's mind, +and never his words, for it was with the former that the movements upon +which the horse depended were bound up. + +It was not enough, however, simply to imagine the number desired. It was +furthermore necessary that the questioner be conscious of the moment +when the horse reached that number. Larger numbers (above 6) were +therefore, successful only when every single tap was inwardly counted to +the end. The manner of counting was indifferent. Thus I counted 6 as +follows: 1, 2, 3, 4, 5, 6, and later: 6, 5, 4, 3, 2, 1, and then again: +6, 6, 6, 6, 6, 6. Finally I used the Greek letters and also nonsense +syllables. And in all cases I obtained six taps, the correct response. +If, however, I simply counted the taps without knowing when the desired +number was reached, the responses were always incorrect, e. g., I +counted + + For No. 10: 10, 10, 10 continuously, Hans tapped 13, + " " 10: 1, 2, 3 to 10 " " 10, + " " 12: 12, 12, 12 continuously, " " 15, + " " 12: 1, 2, 3 to 12 " " 12. + +In the case of smaller numbers, on the other hand, one often obtained +correct results without counting. In this I am borne out by Mr. +Schillings. It was merely necessary to image vividly the number 3, or 4, +or even the name of a week-day or of a month without the number which +would indicate it. In the last of these cases the number corresponding +to the day or the month (e. g. 3 for Tuesday, 5 for May, etc.), though +not consciously presented, still evidently lay at hand in the +subconscious. To use a popular expression, I usually had a "feeling" +when Hans had arrived at the right number. + +It was furthermore found that it was not only necessary to count to, or +to think of, the number desired, but that this must take place with a +high degree of tension of expectancy--that is, a strong affective +element must enter in. The state required for a successful response was +not the mere passive expectation that the horse would tap the number +demanded of him nor the wish that he might tap it, but rather the +determination that he should do it. An inward "Thou shalt", as it were, +was spoken to the horse. This affective state was registered in +consciousness in terms of sensation of tension in the musculature of the +head and neck, by intraorganic sensations, and finally by a steadily +rising feeling of unpleasantness. When the final number was reached, the +tension would suddenly be released, and a curious feeling of relaxation +would ensue. I have made a series of tests to determine the most +favorable degree of tension in expectation. It was possible to +distinguish with certainty, three degrees of tension besides the state +of utter relaxation,--all of which I measured by means of the +differences in the sensations of tension. In cases of tension of the +first degree (greatest concentration) the responses were usually +correct, a few, however, were lacking by one unit. There was therefore +in the latter instance a premature release of inner tension. In cases of +tension of the second degree all answers were correct except a very few +which were too great by one unit. In cases of tension of the third +degree, many answers were wrong, and usually by several units too many. +I wished to have the horse tap 10, with the lowest degree of +concentration. He tapped 13, then in a repetition of the test, 12. I +thereupon increased the tension, Hans then tapped 8. I decreased the +tension once more, but so that it was somewhat greater than at first. +Hans tapped 10 correctly. At another time I tried to have him tap the +number 5, with a low degree of tension. He tapped 6. I intensified +expectation and Hans tapped 4. I again decreased it, and he tapped 5, +_comme il faut_. Apparently, therefore, the most favorable degree of +tension was one between the first and second,--the latter being the +least favorable. After some practice a lesser degree than was used in +the beginning sufficed to evoke adequate reactions. The flow of nervous +energy to the motor centers of the brain evidently became facilitated +through practice. It will be easy to understand why the first days of +experimentation caused intense headaches, which later never occurred. + +Whenever, in the foregoing, we spoke of a certain degree of +concentration which had to be attained, it is not to be understood that +the same tension had to be maintained throughout the test, from the +horse's first tap to his last. But rather, that it began with a low +degree, and gradually increased as the final unit of the count was being +approached. It may best be represented by a curve whose maximum +represents that degree of tension which we have been discussing. The +rise to this maximum which, when attained, was followed by a sudden +fall, did not always occur in the same manner. Three types of curve may +be distinguished, which were first discovered in purely empirical +fashion, and later reproduced voluntarily for purposes of +experimentation by diagramming before each test the intricate curve of +the varying degrees which the intensity of concentration was to assume. +The types may be described as follows: + +I. Here the tension curve rises steadily from beginning to end. This +type preponderates in the case of small numbers. Thus, when I asked the +horse: "How much is 2 plus 4?", the tension increased slowly with every +tap from the moment I began counting, until the final tap was reached, +when it was again relaxed. Externally this relaxation is noticeable as a +slight jerk. + +II. In this case the curve does not rise at an equal rate, but rather +more slowly at the beginning and later undergoes a sudden increase, or +the tension increases immediately at the beginning, remains constant for +some time and then ascends to the maximum. This curve is the rule in the +case of large numbers and evidently means economy of physical energy, +for experience soon taught that a steady increase in tension from the +very beginning soon brought it to a level which cannot be long +maintained and usually leads to a premature relaxation. In the case of +very large numbers the alternation of the slight and the sudden increase +may be repeated several times, and at times it may even sink below a +level which has already been attained, thus making a wave-like curve. + +III. The third type of curve shows a sudden jump between two units at a +certain point in its course. This may occur in the case of both small +and large numbers but only when the highest or first degree of +concentration is employed (see page 91). Such a jump frequently occurs +in the transition from the tap preceding the last to the last one which +is being eagerly expected. Relaxation--with the upward jerk and raising +of the head--here occurs at the normal time; Hans taps to the end with +his right foot. Oftener still the "jump" described occurs while passing +over to the number just before the last. The goal seems within reach and +the mental tension relaxes, and with it the physical tension,--the head +gives a slight jerk and Hans makes the back-step. Since, however, +another tap is still awaited with some degree of tenseness and, since +complete erection of the head does not follow immediately upon the jerk +of the head, the horse gives another tap with the left foot. Thereupon +occurs the complete relaxation of attention, and the assumption of the +erect posture on the part of the questioner. That this is +psychologically the clue which leads to the final tap, will readily +appear from the following remarkable fact: I was able to bring about at +will either the back-step with the right foot, or the additional extra +tap with the left foot by concentrating the mind either upon the last +unit or upon the one just preceding it. In either case the movement +which served as stimulus to the horse followed naturally upon +concentration on the number. I could of course also control the response +by direct voluntary control of the movements involved. Hans thus solved +for me the same ten problems first with the back-step, then with the +extra final tap. + +Finally we will indicate the one true inner cause of the difficulty in +getting the number 1 as a response. It is not easy to relax attention +immediately after having just begun to concentrate. Relaxation, +therefore, often occurs with a certain retardation, and the result is a +belated jerk of the head. + +Briefly, I would also mention a few of the more interesting +introspective observations which were made in situations in which the +horse responded with movements of the head for answers such as "yes" and +"no", "up" and "down", etc. From the very beginning I put questions to +Hans which would have to be answered by a shake of the head. It often +happened that instead of indicating "0", Hans would begin tapping some +number. But the wonder of it was that, in many cases, he responded +properly. I knew only that I inwardly pronounced the word "null" (zero), +and that I looked expectantly at the horse's head. In the case of +questions to which I expected the answer "yes" or "no", I imagined +myself enunciating the answer, i. e., I used motor imagery. The tests +failed, the moment I employed only visual or auditory imagery, whereas, +motor imagery was always effective in calling forth correct +reactions.[M] When the proper response was "up" and "down" I would +think of those directions in space, and likewise with "left" and "right" +in which case also I would put myself in the horse's place. + + [Footnote M: Thus it is possible to think of the word "no" in three + different ways. I may get a visual image of the written or printed + word, or the auditory image of the word as spoken by another person, + or finally I might think of it in terms of images of the sensations + of movement which would arise if I myself were to enunciate or write + the word. And so, in like manner, I could think of any other word in + terms of either visual or auditory or motor imagery. In all + probability the auditory and motor always occur together,[6] but + still it is possible to make the one or the other predominate. + + It appears that the imagery of most persons is a mixture of + auditory-motor and visual elements, with a predominance of one or + the other kind. Individuals who utilize almost exclusively the + visual (as does the author, as a rule), are rare. But rarer still is + the pronounced motor type.] + +While I was still ignorant of the nature of the necessary movements, the +tests were successful only when I had put the question aloud or in a +whisper, but never when I failed to enunciate, i. e., when I merely had +the question in mind ("in idea"). But this also became possible after a +little practice, although I could not then give an explanation for my +success. Except in one instance, we could discern no difference between +problems spoken and those merely conceived by Mr. von Osten who had had +the advantage of long practice. But the one exception deserves mention. +The old gentleman commissioned Hans, presumably without uttering a word, +to step backward to the left. Hans thereupon responded by giving his +entire repertoire, as follows: He moved his head to the right, then to +the left. Then he leaped forward and repeated the same movement of the +head. Hereupon he stepped backward and signified a "yes" by a movement +of the head. He then lowered his head and made two leaps forward. After +this performance Mr. von Osten repeated the same command aloud, and in +every case Hans responded properly. Again the silent command was given +and again the horse responded with the series of reactions described +above, lowering his head leaping forward, etc. In this experiment, +without exception, the spoken command evoked adequate reactions,--the +silent command, an incorrect response. Evidently the impulse to movement +was not so great with the mere conceiving of "right", "left", etc., as +when the words were enunciated. It, therefore, required some practice on +my part before a sufficiently strong movement-impulse became associated +with the idea. All this is in no wise at variance with the fact that +tests involving counting and computation were as successful when the +problem was given in silence, as when it was spoken. The signs for +tapping, viz.: inclination and erection of the head and body, followed +the question. The question therefore became superfluous. On the other +hand the signs for head-movements on the part of the horse, were given +while the question was being put. I ask, which way is "upward", and at +the same time I look upward. In this case therefore the question itself +is not entirely insignificant.--I experienced greater difficulty in +getting Hans to respond with the head-movement to the left. After much +practice I was able to evoke this movement by means of giving the +command aloud, but never by means of the "silent" command. Accidentally +I hit upon a device by means of which I attained this end also. I asked +the horse aloud "Which direction is left?",--whereupon he reacted +properly; then I immediately repeated the question silently, and was +successful every time. My mental attitude here was still the same as +when I put the question aloud. What sort of an attitude this was, I +could not, of course, have stated explicitly at the time. I could not, +therefore, awaken it at will,--and if I allowed but a minute to elapse +between the spoken and the silent question, the vivid after-effect (the +so-called "primary memory image") soon disappeared and the test was +wholly unsuccessful. Practice, however, soon helped me to overcome this +last difficulty also. I believe that my inability to evoke this specific +reaction on the part of the horse, lay in the unfavorable position which +I assumed, for it did not allow the horse to perceive my movements +easily. For the same reason, Hans would at first indicate "no" and +"zero" by turning to the right, seldom to the left. + +As in the case of counting, a high degree of concentration was also +necessary here, but with this difference, that here attention was +directed to ideas present to the mind, ("yes", "no", etc.), whereas in +the counting process attention was directed toward expected sensory +impressions (i. e., the taps of the horse). + +All that has been said thus far is readily understood psychologically. +The following curious fact, however, is noteworthy. Hans used the +head-movement to indicate two such different concepts as "zero" and +"no"; it appeared therefore that in both cases he was receiving the same +kind of directive. Observation proved that such was the case and the +directive in question was none other than an imitation in miniature, or +rather a movement anticipatory of the expected head-movement of the +horse. Now, whereas the signs for "up", "down", "right", and "left" were +natural expressive movements which are normally associated with the +corresponding concepts, this cannot be said to be true of "no" and +"zero". My laboratory observations (see page 107) lead me to conclude +that the movements, by means of which the concepts "no" and "zero" are +naturally expressed, are quite different; and neither of these +corresponds to the signs for "zero" and "no" which the questioner +involuntarily gave to Hans. What was the genesis of these unnatural +forms of expression? If we might assume that the questioner always had +in mind the movement he awaited on the part of the horse, and never +thought of "zero" or "no", then the contradiction would solve itself. +But I must deny decidedly that I ever thought of the movements of the +horse's head, and Mr. Schillings, whom I questioned on this point, +agreed with me in this, in so far as his own mental processes were +concerned. I can see nothing for it but that in this instance the +expressive movements normally connected with the concepts "zero" and +"no" have been replaced by other forms, without the questioner becoming +aware of it. That such displacements may occur, has been shown by the +tests described on pages 107 to 112. That they did occur in this +instance may be concluded from the following observation. In responding +to me, as well as to Mr. Schillings, Hans always moved his head first to +the left, then to the right, never in the opposite order. That this was +_not_ a peculiarity of the horse, but must be ascribed to the signs +which were given him, is shown by the possibility of inverting the order +under experimental control (page 77). Frequently Mr. Schillings and I +had seen the horse respond to his master by means of such +head-movements, and the order was always, without exception, the one +mentioned. It must be assumed therefore that the horse's movement, which +we so often noticed, made such an impression upon us, that afterwards it +was regularly reproduced on our part quite unconsciously, so that Mr. +Schillings never, and I only after a long time, became aware of the +whole process. + +In closing, just a word as to the discovery of our own movements. I soon +noticed that every pronounced raising of the head or trunk brought about +an interruption in the horse's response. But only by observing the +final movement in the case of Mr. von Osten did I discover that I, too, +performed a slight erection of the head. Observation of others was less +difficult than the observation of one's own movements. As in the case of +all other signs given to the horse, these movements were so slight that +they were prone to escape notice even though one's whole attention were +concentrated upon their detection. I also questioned whether in my +attempts to disturb the horse by means of loud calls, it were really the +call or some simultaneous involuntary movement which was the true cause +of the interruption. The doubt was justified, for when I finally learned +to cry out vehemently without making the slightest move, all my crying +was in vain. Also it had seemed to me at first as if I were able to +induce the horse to rear, not only by means of the proper sign or +movement, but also by a mere command, but I found later that in every +case there was always some movement, were it ever so slight. Finally I +tried to simulate voluntarily the oft-mentioned involuntary jerks of the +head. Although it is not very difficult to execute them at will with +almost the same minuteness as when they were performed involuntarily, I +still did not succeed in getting a series of such jerks of equal +fineness throughout. In spite of (and partly on account of) the most +concentrated attention, there would be from time to time a jerk of +somewhat greater extent and energy. As soon as the movement had been +executed, I was able to form a good judgment as to its relative extent, +but I was unable to regulate the impulse beforehand. + +With the following comment the chapter will be concluded. Introspections +are necessarily subjective in character. If they are to possess general +validity, they must be borne out by evidence furnished by others--and +this to a greater extent than is necessary for other forms of +observation. It was hardly possible to get corroboration from the other +persons who had worked with Hans, for, although some of them were +excellent observers of external natural phenomena, few of them had had +the necessary amount of practice in introspection. The necessary +confirmation, however, was had in laboratory tests, which we shall +presently describe. + + + + +CHAPTER IV + +LABORATORY TESTS + + +The tests which are to be briefly reported here, were begun in November, +1904, and were carried out at the Psychological Institute of the +University of Berlin. The purpose was twofold: first, to discover +whether the expressive movements noted in Mr. von Osten, Mr. Schillings, +and others, were to be regarded as typical and to be found in the +majority of individuals,--and secondly, to ascertain in how far the +psychical processes which I had noted in my own case and which I +believed to lie at bottom of these movements, were paralleled in, and +confirmed by, the introspections of others. The effort was made to make +the experimental conditions as nearly as possible like those under which +the horse had worked. The affective atmosphere which colored the +situations in which the horse took part, could not, of course, be +transferred, but this was in some respects an advantage. One person +undertook the role of questioner, another--myself--that of the horse. +The experiments fall into three groups, corresponding to the types of +the horse's reactions: 1, tests in counting and computation; 2, tests in +space reactions; 3, tests in fetching or designating objects. + +In the experiments in counting and computation, the questioner, standing +at my right, thought with a high degree of concentration of some number +(usually between 1 and 10, but sometimes also as high as 100), or of +some simple problem in addition. Then I would begin to tap,--but in +human fashion with my right hand, rather than with my foot--and +continued until I believed that I had perceived a final signal. I thus +tested, all in all, twenty-five persons, of every age and sex (including +children of five and six years), differing also in nationality and +occupation. None of them was aware of the purpose of the experiments. It +could not escape them, to be sure, that they were being watched. It was +also evident to them that the things noted were certain tensions and +movements; but none of my subjects discovered what the particular +phenomena were that I was looking for. Only in a few isolated instances +did they report that they were conscious of any movements on their part. +With the exception of two persons, they all made the same involuntary +movements which were described in chapter II, the most important of +which was the sudden slight upward jerk of the head when the final +number was reached. It was at once evident that the direction of this +jerk depended upon the position which one had asked the subject to +assume at the beginning of the test, the direction changing whenever the +position was changed. Thus, if the subject stood with head bowed--the +body either being held erect or likewise bowed,--then release of tension +would be expressed physically by an upward jerk. (Occasionally the +entire trunk is slightly raised, so that it was possible to observe this +physical reaction when standing behind the subject). If the subject had +bent his head backward, the "psychological moment" was marked by a +forward movement, (although under certain conditions the head was, in +such a case, observed to bend still farther backward). If during the +tests the head was bent slightly to the right, then the reaction was +expressed in a movement toward the left, and _vice versa_, if it had +been on the left, it was bent to the right. If the subject had been +bending his head forward and to the right, he then raised it upward and +to the left, etc. In all of these changes of position I noticed an +intermediate posture which, to be sure, it was not always an easy matter +to discover,--viz.: an upright position in which there was discernible +no manner of head-movement or only a slight tremor. If the subject was +lying on his back with his head supported, then there was noticeable a +very slight movement to one side. In this same way a number of other +positions were tested in order to discover for each the characteristic +movement expressive of release of tension. It would therefore appear +that the raising of the questioner's head, which served as the signal +for stopping for Mr. von Osten's horse, was but one instance of a +general law which may perhaps be stated thus: The release of muscular +tension which occurs with the cessation of psychic tension, tends to +bring about that position of the head (and body) which, at the time, +represents the slightest amount of muscular strain.--These movements +seldom were pronounced enough to be compared to motion through a +distance of one millimeter, in a very few cases only did they attain to +the magnitude of one or two millimeters: I failed to note them entirely, +however, in only two individuals, two scientific men whose mode of +thought was always the most abstract, and one of these was, in spite of +repeated attempts, unable to elicit any response whatever on the part of +the horse. + +In the cases of the more suitable subjects I was able to indicate not +only the number they had in mind, but also the divisions in which the +number was thought, thus 12 as 5 and 5 and 2, or the same number as 2 +and 5 and 5, and I was also able to determine the addends in the +addition--i. e., whether the problem had been conceived as 3+2=5 or as +2+3=5. It frequently happened that in the beginning I would sometimes +mistake these subdivisions, which were recognizable by the less +pronounced jerks, for the final number. Thus I would often respond with +4 instead of 8, or 3 instead of 9, or with 3 when the problem was 3+2, +just as Hans had so often done. In these tests, too, the difficulty of +getting the number 1, as well as the larger numbers, came to light. Thus +three times in succession 17 was indicated as 4, as 9, and as 17. But +after some practice I was able to give numbers as high as 58 and 96. The +frequency of the errors of one unit too many and of one unit too few is +also noticeable in these tests. + +We also found desirable corroboration, by trustworthy subjects, of the +introspective observations of the author, which were reported in Chapter +III, with regard to the significance of concentration and the curve of +attention. It is hardly necessary to mention that no attempts were made +to influence the subjects in their accounts by asking suggestive +questions. The most valuable feature about these tests was that the mute +horse had now been replaced, as it were, by an animal capable of speech, +and that it was now possible to follow the same process both from within +and from without. Two illustrations may be welcome. The one who took the +part of the horse gave three taps and made the following entry: "At 3 I +saw a slight upward jerk of the head on the part of the questioner". The +questioner however had thought of 4, and made the following note, +without knowledge of the other's entry: "I was aware of extreme tension, +so that it was impossible for me to get beyond 3". Or again, the +'horse', reacting to a movement on the part of the questioner, stopped +at 3, but the latter, having intended to obtain 2, made the following +entry: "I noted clearly that I ceased thinking of the number too late, +and did not put on the brakes, as it were, until I had arrived at 3". We +see that errors here were entirely the fault of the questioner, just as +had been the case in the tests with Hans. (See page 151f.). + +In a second group of experiments I asked a subject to fix his mind upon +certain concepts, such as "up", or "down", "right" or "left", "yes" or +"no", and others, in any order he pleased, but with the greatest +possible degree of concentration. The subject each time had the choice +of four or six concepts, and he was told to think of one of them at the +signal "Now!". How he was to 'think' the concept was left entirely to +him. He was also told to interpolate the series with a 'blank', that is, +to think of nothing at all. Standing opposite the subject, I tried to +guess at the mental content of the person's mind, on the basis of +expressive movements. Sometimes I reacted by shaking or nodding the +head, etc., just as Hans had done, but as a rule I was content to say +the word which I thought the subject had in mind. With twelve subjects +(a total of 350 tests) I made an average of 73% correct responses, and +in the more favorable cases I attained even 90 to 100% correct +responses. Very slight involuntary movements of the head and eyes, which +showed but little individual variation, and always occurred when the +subject began to fix upon the concept, were the signs which I used as +cues. As in the case of the movements expressive of the release of +tension, which I discussed above, these movements, too, occurred without +the subject being aware of them, (except in those rare cases in which +they had once or twice been especially pronounced). Indeed, it was very +difficult and in some cases almost impossible for those persons whom I +had initiated into the secret, to inhibit them voluntarily. "Up" and +"down", "right" and "left", were expressed by movements of head or eye +in those directions, "forward" by a forward movement of the head, "back" +by a corresponding movement. "Yes" was accompanied by a slight nod of +the head; "no" by two to four rapid turnings of the head to either +side.[N] "Zero" was expressed by a movement of the head describing an +oval in the air. Indeed, it was even possible to discover whether the +subject had conceived of a printed or a written zero, for the +characteristics of both were revealed in the head-movements. I was able +later to verify this graphically. With Ch. as subject, I made 70% +correct interpretations in a total of 20 tests; with von A. as subject, +72% in a total of 25 tests. And finally I was able to interpret the +signs without any errors at all. It was not absolutely necessary to look +directly at the subject's face. Even though I focussed a point quite to +one side, so that the image of the subject's face would fall upon a +peripheral portion of my retina, I still was able to make 89% correct +interpretations in a total of 20 tests.--This is not astonishing after +all, when we recall that the periphery of the retina possesses a +relatively high sensitivity for movement impressions, although its +chromatic sensitivity is very low.[O] + + [Footnote N: It was Charles Darwin[7] who first pointed out that the + expressive movements (of the coarser sort) to be noted in nearly + every race and people show a great, though by no means complete, + similarity. The similarity is most pronounced in the shaking of the + head to signify negation and nodding to denote affirmation. It will + be noted that the former is essentially of the nature of a turning + toward, and the latter a turning away.[8] These same movements have + been reported in the case of the blind and deaf Laura Bridgman,[9] + and we have been explicitly assured that they were a spontaneous + development, and not acquired by imitation. For it is by imitation + and never before the completion of the first year, that our children + acquire these movements. On account of his unreliability, we can put + but little stock in the statement of Garner,[10] a writer on the + speech of monkeys, that these same gestures have been observed in + the case of those animals. My experiments show that the same + movements, greatly diminished in scope, as a rule accompany the mere + thought of "yes," "no," etc. I cannot, however, regard the assertion + as an established fact that every thought process whatsoever is + connected with some form of muscular movement, as has been + generalized by the French physiologist Fere,[11] and the American + psychologist Wm. James.[12]] + + [Footnote O: The productions of mind-readers, so-called, also, are + based upon the perception of involuntary movements, insofar as they + are not based upon pre-arranged schemes and trickery. But there we + have to do principally with tactual perception, since the reader + touches the hand of the subject and is guided by its tremor. Some of + the expert mind-readers, however, conduct tests without touching the + subject. They depend chiefly upon auditory impressions: the sound of + footsteps,[13] involuntary whisperings[14] and the changes in the + subject's respiration[15] and the murmuring of the spectators. To a + less degree visual signs also are involved: posture and facial + expression of the subject, and movements of eyes and lips.[16] Even + the heat radiating from the person's body is supposed to have some + influence.[17] And my own experience has taught me that surprising + results may be obtained by the utilization of the movements + described in the preceding chapter. + + It may be that these truly microscopic movements also play some part + in bringing about the success of some of the experiments in + telepathy, so-called, (transference of thought from one person to + another, ostensibly without any mediation of the senses known to + us.) In spite of the huge mass of "experimental evidence" which has + been collected, chiefly in England and in America, it appears to me + that telepathy is nothing but an unproven hypothesis based upon + experimental errors.] + +It was assumed, as indicated on page 99, that in the case of Mr. +Schillings and myself the movements naturally expressive of "zero" and +"no" had been displaced--without our being aware of the fact--by +others, viz.: those which the horse required as directives for his +reactions. Since this was the case, we tried to discover if a similar +displacement could be brought about experimentally. The attempt was +successful and we discovered that under suitable conditions we could +cause the subject--quite without knowledge on his part,--to establish an +"association" between any given concept and any given expressive +movement. The following experimental series will serve to illustrate +this fact. + +I had one of the subjects (von A.) think of "left" and "right" in any +order he chose. (The command was purposely given only in a general way: +"Think of 'right' or 'left'".). We had agreed that I was to try to guess +the mental content of the subject's mind, but I was not to utter a word. +Instead, I was to indicate "right" in every case by an arm movement +downward, and "left" by a movement upward. To the subject I gave a +fictitious but plausible reason for all this. The behavior of the +subject took the following course: In the first three tests he moved his +eyes to the right when he thought of "right", and to the left when he +thought of "left". This was the normal expressive movement. In the +fourth test, however, the thought "left" was accompanied by an upward +movement of the eyes. Two further tests again showed eye-movements to +the right and left. In the seventh test with the idea "left" the eyes +moved first to the left and then immediately upward. In the following +ten tests the eyes were turned regularly upward at the thought of +"left", and downward at the thought of "right", with only one exception +which was a normal movement to the left. The normal expressive +movements, therefore, were displaced by the artificial, after the +seventh test. + +In the case of another subject (B.) in whom normally the thought of "up" +was accompanied by a slight raising of the head, and "down" by a +downward movement, these natural forms of expression disappeared +entirely as a result of my arm movements to the right to indicate that I +inferred his having in mind the thought of "up", and to the left when I +inferred that he was thinking of "down". Instead, there appeared not +merely the desired movements to the right and left, but rather movements +upward to the right and downward to the left. That is, instead of a +complete displacement of the old by the new, there occurred a +combination of the two. + +A third type of result appeared in still another subject (Ch.), who +normally expressed the concepts "right" and "left" by eye or head +movements (never both kinds at the same time) to the right and left. +Here my arm movements up and down caused the eye and head movements to +be made simultaneously, so that the thought of "right" found expression +in an upward movement of the head and an eye movement to the right, and +the idea of "left" in a downward head movement and a movement of the eye +to the left. The subject had no knowledge of this process, and it took +six tests to bring about the new reaction. From that point onward the +new movements were so well established that, depending upon them for my +cue, I was able to make 32 correct inferences in a total of 40 tests. +During the latter part of this series I blindfolded the subject, so that +I could not see the movements of his eyes, and therefore had to base my +inference entirely upon his head movements.--After removing the bandage, +at the end of the series, I told the subject that I would go through +another series, in which I intended to indicate his thought of "right" +by an arm movement downward (instead of upward as heretofore), and his +thought of "left" by a movement upward. (This he regarded as an idle +whim of mine). It was only after the twelfth test that the former +"association" which I myself had caused to be established, was +completely displaced by the new. The thought of "right" was now +accompanied by an eye movement to the right and instead of a raising +there was a lowering of the head. A corresponding change occurred in the +head movement expressive of the thought of "left". These responses were +occasionally varied by some in which only the head movement or only the +eye movement occurred. But these movements were always to the right, or +downward and to the right, at the thought of "right",--and to the left, +or upward and to the left, at the thought of "left". In ten tests I made +ten correct inferences. After the new association appeared firmly +established, I ceased responding by means of arm movements, and +indicated my 'guesses' by word of mouth. At first the newly acquired +movements continued to appear promptly in the subjects. But gradually +they tended to become more uncertain and finally disappeared, as readily +as they had appeared, and the normal conditions were once more +established. Nor was there any tendency to reappear on the following day +in another series of tests. (Those just described had been made on one +day in the course of an hour or two). But as soon as I again used the +earlier method of arm movement to indicate my inferences (raising the +arm for "right", lowering it for "left"), the former artificial +association was again established, although not until some 14 tests had +been made,--during which the normal movements to the right and left were +often inhibited and during which the conditions were, on the whole, +chaotic. The new association, thus re-established, remained constant +during the ten tests of the remainder of the series, but has very +probably again disappeared long ere this. In the case of this subject it +appears therefore that the new associations were superimposed upon, but +in no sense displaced, the normal expressive movements. Nor did the two +coalesce (except in a few exceptional cases), but tended as a rule to +occur independently of one another. + +I would emphasize once more that none of the subjects had any knowledge +of the purpose or meaning of the experiments. Also, I was convinced by +questioning the subjects afterwards that none of them--and this is the +essential point--had merely conceived of the arm movement which they +were expecting me to make, instead of concentrating thought upon the +idea of "right" or "left". On the contrary, all of them considered my +particular movements mere vagaries and without purpose, and they felt +perfectly certain that they were in no wise influenced by these +movements. Also, none of the subjects was conscious of any movements on +their part, except one, who was at times aware of her eye movements to +the right, but never of those to the left, (see page 111), nor of the +head movements which for us constituted the phenomena of prime interest. +When I asked my subjects what they believed to be the cue upon which I +based my inferences, they invariably responded with probable +explanations which were always wide of the mark, and those to whom I +disclosed the cue--(after the experiments were completed), were +thoroughly astonished. + +In the tests just described we had to do only with such ideas or +concepts as normally were associated with some stereotyped form of +expressive movement (see page 106). I now chose a group of ideas which +are not normally associated with a particular form of motor expression +peculiarly characteristic of them, and sought to establish artificially +such a connection with some arbitrary movement, without consciousness of +the process on the part of the subject. Thus I asked one subject (Miss +St.), who had no intimation of the aim of the tests, to think of the +following words in any order she might choose: "Ibis" (ibis), "Irbis" +(panther), "Kiebitz" (plover) and "Kuerbis" (pumpkin). I said that I +would react to her thoughts by means of arm movements forward and +backward to the right and to the left, respectively. 15 out of 20 tests +were successful, without the slightest suspicion on the part of the +subject (whose whole attention was concentrated on the word-content), +that she was giving me the necessary directives in the form of very +minute movements of the head and eyes to the right and left, etc. She +was greatly astonished that I should be able to guess words so much +alike,--(she did not know that the element of likeness was productive of +no difficulty). When, during one of the tests, the subject happened to +think spontaneously of the movement she was expecting me to make, she +became confused, and as a result the number of my sucessful reactions +suddenly fell. I never would have discovered the cause, had not the +subject enlightened me without my asking. + +I repeated this series with three other persons, who had had some +psychological training. I did not use the same movement for each word in +all three cases, but indicated the word "Kiebitz", for instance, by +means of an upward movement in one case, by turning the head to the +right in another, etc. In one of the three cases the tests were almost +wholly unsuccessful. The cause for this came to light later, but it +would involve too much exposition to discuss it at this point. In the +case of the other two persons, the tests were successful beyond +expectation. I had made my various arm movements only a few times when +they presently began to raise their heads slightly when thinking of +"Irbis", and to move it to the right at the thought of "Kuerbis", etc. In +the two series of 35 tests I did not have a single error. In a number of +instances I succeeded in guessing the word upon which the subject had +decided, even before the test proper was entered upon--i. e., before the +signal for concentration had been given. Nothing surprised a subject +more than the remark: "You are intending to think of the word 'Kuerbis'", +or "You had thought of concentrating your mind upon 'Ibis' but later +decided in favor of 'Kiebitz'", yet nothing could be more simple. Before +every test the subject would consider what word he would fix upon, and +while he was saying to himself "I will choose 'Ibis'", the proper +movement would accompany his decision, although it was only very slight, +because attention had not yet attained the degree of concentration which +was employed in the test proper. + +In these experiments also, the subjects, whom I know to be absolutely +trustworthy, declared that they never thought of the arm movements which +I was to make. They regarded them as being quite irrelevant. Also--with +but one exception--they thought of the objects, in so far as they imaged +them visually, as being directly before them, and not off in the +direction indicated by my arm movements. Thus they did not image the +plover ("Kiebitz") as being on the wing, when I raised my arm, or as +resting on the ground, when I pointed downward, etc. One of the subjects +had done this occasionally, but by no means regularly. He was therefore +asked to localize all objects in the same place, i. e., directly in +front of him at the level of the eye. He complied with this request, but +no change, whatever, was observed to occur in his expressive movements. + +In order to overcome the difficulty just mentioned, I selected another +subject (Miss von L.), whose power of visualizing was very slight, and +requested her to fix her mind upon four words which I had selected +because they were not, necessarily, associated with a particular image. +The order in which the words were to be thought of, was entirely +optional on her part. The words were "Form", "Inhalt", "Mass", and +"Zahl", (form, content, measure, and number), and each of them I +accompanied, with a certain definite arm movement. The subject always +pronounced the word inwardly as emphatically as possible, but without +ever imaging the corresponding arm movement. Often, it must be noted, +she did not know whether or not the movement which I made was the proper +one. And yet she, too, soon fell into line in the matter of executing +unconsciously the characteristic head movements. In a total of 50 tests, +I was able to make 10 correct guesses in the course of the first 20 +tests, 8 in the next 10 tests, and 19 in the last 20 tests. Miss von L. +noted only a few of her upward head-movements, viz.: those that were +especially pronounced (movements through about 2 millimeters), but of +the others she knew nothing. The same experiment was repeated with a +psychologist, well-trained in introspection, as a subject. Success was +even greater here. But no matter how closely the subject observed +himself, he was unable to solve the puzzle. + +Variations which were introduced in these tests, I will only mention in +passing. Thus, instead of making an arm movement, I, in some cases, +would tap with my foot, for "Ibis" once, for "Kiebitz" twice. The +subject could not see my feet. The involuntary movement-expression which +became associated with "Ibis" was one nod of the head, with "Kiebitz" +two nods, etc. Here our only concern was to show that unconscious change +in natural expressive movements and the acquisition of artificial ones +are possible in the case of psychically normal subjects trained in +introspection. + +I was not satisfied with convincing myself subjectively of the facts +indicated, but sought to fix them objectively, by means of a graphic +method. For this purpose I used the device mentioned by Prof. R. Sommer +for the analysis of expressive movements.[18] The purpose for which +Prof. Sommer's apparatus had been constructed, was to record the +involuntary tremor and movement of the hand. These movements, of course, +take place in the three dimensions of space. By means of three levers it +is possible to record the movements upon the flat surface of a smoked +paper fastened to the revolving drum of the kymograph, the movements in +each direction being recorded by a separate lever, in such a way that +the three curves thus made represent the analysis of a single movement +into its three dimensional components. By making slight changes, which +tended to complicate the experiment somewhat, I adapted the apparatus to +the measurement of movements of the head. The method of experimentation +was the following. The subject whose movements were to be registered, +was placed in the device in such a way that his trunk and head were bent +slightly forward, the latter a little more than the former. This, it +will be remembered, was the usual position of the questioner when +working with the horse. Three levers were attached to his head in such a +way that every movement backward or forward would act upon the first +lever, every movement to the right or left would move the second, and +every movement of the head upward or downward would be recorded by the +third. With regard to the sensitivity of the machine, micrometric +determination showed that when the subject was properly installed, +movements through so small a distance as 1/10 millimeter could be +accurately ascertained. The subject was carefully instructed to remain +as quiet as possible, but without constraint. Voluntary movements were +thus obviated. But the question arose: were not the involuntary +movements thus suffering a loss?--And it was upon them that we were +experimenting. The question cannot be put aside summarily, but +experience taught us that the movements in question, nevertheless, did +appear quite effectually, if one could have the right kind of subjects +at one's command. We need hardly mention that besides the two persons +immediately concerned--I, myself, attended to the apparatus--there was +no one else present, and that the subject was not allowed to see the +curves produced on the kymograph. Besides the registration of the +head-movements, I also undertook to register the respiratory-movements +of the subject. This was done by means of the so-called pneumograph, +attached to which was a lever recording the thoracic expansion and +contraction. This was for the purpose of ascertaining the relationship, +which might eventually be found to exist, between the release of psychic +tension, on the one hand, and respiration, on the other. + +The subject was now told to think of some number, which, of course, was +unknown to me. At a given moment I was to tap upon one of a series of +keys arranged like those of a piano, with the middle finger of my right +hand--corresponding to the right forefoot of the horse. The questioner +observed my key, I, his head,--just what had happened in the experiments +with Hans,--and as soon as I perceived the involuntary closing signal I +reacted upon it by releasing, suddenly, another key upon the same +keyboard, which I had in the meantime been pressing down with my second +finger, thus marking what with Hans had been called the backstep. Each +key was connected with a separate electro-magnet, and these in turn with +markers, in such a manner that pressure upon the keys closed two +electric circuits and, releasing the keys, opened them, and both the +closing and the opening were recorded upon the smoked paper by means of +the markers. And, finally, in order to ascertain the time relations of +all these processes, a time-marker indicated the time in fifth-seconds +upon the revolving kymograph record. The time-curve was recorded just +below the other curves. + +Of the curves[P] thus obtained under the most equable conditions +possible, we publish seven which show the great general uniformity of +the tests made upon the horse with those made in the laboratory. The +role of questioner was undertaken at different times by Mr. Schillings +and the students of philosophy, Messrs. von Allesch, Chaym and K. Zoege +von Manteuffel. To all of them I am greatly indebted for their unselfish +services in these laborious tests. The experiments with von Allesch and +Chaym, who were among the most suitable of my subjects, were conducted +absolutely without knowledge on their part of the nature of the +phenomena which I was observing. Neither of them knew anything about the +expressive movements in which they were unconsciously indulging, and +furthermore, since they kept their heads bowed during the entire course +of these experiments, they did not perceive what it was that I was +observing. It is interesting to note that Chaym on the occasion of his +only visit to the horse, immediately received a number of correct +responses. Without a doubt von Allesch would have met with equal +success. The other two subjects (von M. and Sch.) went through this +series of tests, possessing some knowledge of the nature of the +movements involved. Conditions were such that they (and especially Mr. +Schillings) could not be prevented from obtaining some knowledge of the +essentials, at least. However, it would be wrong to suppose that for +this reason the results were more favorable, owing, mayhap, to voluntary +efforts on the part of the subject. The contrary was true. The two +subjects who had no knowledge of the character of the reactions upon +which my responses depended, retained their normal habits, unchanged, +throughout the series,--whereas the last-named two, afraid lest their +knowledge vitiate the result, lost more and more of their power of +concentration and within a short time were in a condition of tense +inhibition, which is all the more conceivable, since they had had no +psychological training whatever.[Q] + + [Footnote P: For registering the curves a Hering kymograph was used, + with a loop 2-1/2 metres long. The kymograph rested on felt. With + the aid of the Marey model a pneumographic record was taken now of + the thoracic, now of the abdominal, breathing, never both + simultaneously, since this was extrinsic to my purpose, and it would + have made the whole experiment too complex. The time was recorded by + means of the Jacquet chronograph. For purposes of making more exact + measurements the acoustic current interrupter of Bernstein was used, + attuned to 100 vibrations per second. But this necessitated such + rapid revolution of the drum of the kymograph that the curves were + not compact enough for purposes of demonstration. The levers were + all fitted with micrometer adjustments. They wrote tangentially and, + except the one registering the breathing curve, all points lay in + one vertical line. The error of deflection and that due to the + rondure of the writing-surface were both very slight on account of + the comparative length of the levers and the small extent of the + excursions, and for that reason synchronous points lie practically + in one perpendicular. Only the breathing curve has been moved + somewhat to the left, 7.5 millimeters in figures 6 and 7, 2 + millimeters in figure 8, 4.5 millimeters in figure 9. (When the + breathing was very profound, as occasionally happened, the error of + deflection would, of course, have to be taken into account.) The + curves here used as illustrations have been reproduced in the exact + size of the originals by the zinco-graphic method, though somewhat + compressed vertically in order to economize space.] + + [Footnote Q: My own expressive movements, on the other hand, are as + pronounced as ever. I still find the attempt to suppress them as + difficult now as when I was working with the horse (page 57). I + could not, of course, procure a curve of these movements of my own.] + +Their movements, which at first were quite profuse, decreased more and +more, so that in the case of von Manteuffel the percentage of my +successful responses sank from 73% correct responses in 90 tests to 20% +in a total of 20 tests,--and in the case of Schillings from 75-100% to +23% in a series of 35 tests. The curves obtained with von Manteuffel as +subject, which I am here publishing (figures 8 and 15), are, however, +true to his normal habits. The same is true of the two first curves of +Schillings (figures 10 and 11), whereas the third (figure 12) shows +distinctly the traces of the state of inhibition into which he fell, and +represents the same condition as when Mr. Schillings, while preoccupied, +tried to work with Hans. All the finer details of the phenomena in +question, were likewise unknown to these two subjects. + +For purposes of a clearer understanding of the various curves, figure 5 +is inserted to give the general scheme of their arrangement. + +[Illustration: FIG. 5.] + +All curves are to be read like script from left to right. The first is +the breathing curve of the questioner, the second, third and fourth +curves represent his head movements,--all translated through the +workings of the levers into up-and-down movements. The objective +direction of these head movements is indicated by the arrows. It will be +noted that (because the lever in question was one with two arms, and +therefore reverses all movements made) each lowering of the head is +indicated by a rise in the fourth curve, and each raising of the head is +recorded by a sinking in the same curve. The records of the head +movements forward and backward and to the left and right (curves 2 and +3) are two and one-half times the size of the actual movements; while +the curve of the movements up and down (curve 4)--which is of especial +interest to us--is five times its actual size. The fifth and sixth +curves, which record my own responses, represent the taps of the +horse,--the fifth indicating the number of taps and the sixth the +back-step, which was Hans's reaction when he noted the head-jerk of the +questioner. The seventh, the lowest line, indicates the time in +fifth-seconds. Since the rate at which the drum revolved was not uniform +for all the tests, the fifth-second marks do not appear the same +distance apart in all the records, but are farther apart the greater the +rapidity with which the drum revolved. For the experiment itself this is +quite immaterial. Figures 6 to 9 correspond in detail with the diagram +just described. Figures 10 to 12 differ only in that the breathing and +back-step curves (the first and sixth in the diagram) are lacking. In +these there is no response on my part to the head-jerk of the subject, +but tapping was continued _ad libitum_ (in the case of the illustrations +here given I tapped to 5). When these latter curves were taken the +ordering and the technique of the experiments had not yet been +perfected. When this was finally done, Mr. Schillings, who acted as +subject in those tests, had to be eliminated from the ranks of +appropriate subjects on account of the increasing inhibitions, which +gradually developed as described on page 120. + +Analysis of such curves is rather difficult, and those of different +subjects cannot be directly compared. It is necessary to make a study of +the normal curve of each subject taken when his affective state could be +described as "indifferent". The influences of the purely physiological +processes, such as pulse[R] and respiration, must also be determined. +And even so, an interpretation of the curve becomes possible only when a +large mass of material is at hand, and when the introspections of the +subject are taken into consideration. The following remarks, therefore, +are not based solely upon the illustrations given, but upon the mass +total of my results. + + [Footnote R: Slight head movements accompanying the pulse-beat were + until recently regarded as the symptom of certain diseases of the + vascular system (the so-called symptom of Nusset), but H. Frenkel + has now shown them to exist also in normal individuals.[19] I myself + discovered such movements (lateral as well as sagittal) more or less + pronounced in all the curves obtained from my subjects. The most + striking case was that of a young physician whose circulatory system + was perfectly healthy. In most instances I was able to note these + oscillatory movements directly and to count them without much + difficulty. For purposes of control the radial pulse was always + determined at the same time. The observation of the phenomenon + appears to be especially easy in the case of somewhat full-blooded + individuals.] + +In beginning our analysis, let us take first the breathing curve. Our +results here were quite in accord with the view taken by Zoneff and +Meumann,[20] who believe that in the respiration is to be found a good +index of the affective tone of the subject's mental state. In the +greater number of cases it was possible to conclude as to the degree of +concentration of attention,--and when this was very great, it was even +possible to get a clue as to the number thought of. Since the high +degree of tension, under which a subject labored during a test, would be +accompanied by strong affective coloring, we cannot regard as normal any +of the curves here reproduced (with the exception of the two high points +in figure 9). Although breathing was always deep and regular before and +after a test, during the test it was less deep and irregular. Very often +it was suspended altogether (figures 7, 8 and 9). In ordinary life we +often notice that highly concentrated attention is usually accompanied +by non-voluntary inhibition of movements in the musculature which, for +the moment, is not directly involved; the man lost in thought slackens +his pace and finally stands still, the intent listener or looker-on +holds his breath. + +Of the three curves registering the movements of the head, we find that +nothing peculiarly characteristic is revealed by the two upper ones, +giving the movements up and down, and to the right and left, +respectively. They are the ordinary tremor-like movements and indicate +nothing beyond the fact that the subject is unable to hold his head +absolutely quiet for even one second. It is the third line that is of +interest to us, for it is here that the oft-mentioned head-jerk (which +indicates arrival--in the counting--at the number expected) registers +itself. The moment of the head-jerk corresponds, almost without +exception, with the moment of the first deep inhalation,--just as one +would be led to expect from common experience. But we are not to regard +the head-jerk as a result of the inhalation, for it also occurs when the +subject complies with the request that he hold his breath during the +test. The actual height of the jerks recorded in figures 6 to 12 was +1/4 to 1-1/2 millimeters and the average height obtained from the forty +curves of these four subjects was 1 millimeter. There is great +individual variation: the greatest height that was obtained from the +records was 2-3/10 millimeters, the lowest 1/10 millimeter. The +variations within the records of the several individuals are +comparatively slight and are evidently dependent, in the main, upon the +degree of concentration of attention. Thus in the case of von Allesch, +where in 75 tests the average height of the jerk is 1 millimeter, the +mean variation is 4/10 millimeter. If, in order to obtain some idea of +the size of Mr. von Osten's movements,[S] we compared the values gained +in the laboratory with those which would probably obtain in his case, we +would say that his head movements were more minute than almost any of +those of which we obtained records. At the most they could not have been +more than 1/5 millimeter (when measured in terms of the distance through +which the brim of his broad hat moved, they would appear to be about +1-1/2 times as large. See page 49.) The movements of Mr. Schillings, on +the other hand, were certainly four or five times as great as those of +Mr. von Osten, and occasionally even greater than that. When we turn to +consider the time-interval elapsing between the subject's final +head-jerk and my reaction (as recorded in the sixth curve), we find +that the reaction-time averages 3/10 seconds, a value which agrees very +favorably with that estimated for the horse (page 56). Thus it appears +that man and beast have the same reaction-time--though we must bear in +mind that I worked under some difficulty, since I had to care for the +apparatus. + + [Footnote S: In a special series of experiments a subject was + instructed to execute rapid head movements as minute and as evenly + as possible. These were registered objectively and at the same time + I made judgments concerning them. The results showed that my + judgments were most exact in the case of the most minute jerks. The + thing that made it especially easy to judge the movements of Mr. von + Osten under normal conditions, (page 220), was their extraordinary + evenness, such as I have not met with in any other individual.] + +Let us now turn to a discussion of the several figures. + +Figure 6 (von Allesch) gives a typical view of the great, and at the +same time economic concentration of attention characteristic of the +subject. Respiration (first curve) is not so profound as usual, yet is +changed very little. The head-jerk (fourth curve) is of medium height. +It occurs just at the proper moment,--the subject had thought of 2, and +had directed his attention economically. This attention was of the kind +described as type I on page 93. The lowering of the head, (recorded in +the figure by a rise in the curve), immediately following upon the +head-jerk upward, is irrelevant. + +In figure 7 (Chaym) we have a record of a different nature. Respiration +was inhibited throughout the test,--(the small waves are due to the +pulsating of the heart); immediately after the test deep breathing takes +place. Tension steadily increased till 3, the number expected, was +reached. The head, accordingly, gradually sank a little forward. The +head-jerk ensued during an interval beginning just before the reaching +of the goal and ended immediately after. The movement was predominantly +backward, its upward direction being only through a distance of 1/4 +millimeter. (This subject was not so strongly motor as the preceding +one.) The reaction followed promptly as seen in curve 6. It was the +decided raising of the head which follows the head-jerk, that prevented +the usual back-step with the left foot, when the subject was working +with Hans. + +[Illustration: FIG. 6.] + +[Illustration: FIG. 7.] + +Figure 8 (von Manteuffel) is typical of strong and at the same time +economical concentration. Respiration, normally deep and very regular, +is for a time completely inhibited. Tension rises steadily and the head +gradually inclines forward. In the interval between the number before +the final one and the final one the subject makes a sudden bend forward +and immediately upon reaching the final number gives a violent jerk of +the head, upward. The attention here would be characterized as being of +type III, described on page 94. (Owing to lack of space it is impossible +to give an example of type II, which is only to be found in the case of +very large numbers.) + +Figure 9 (von Allesch) is expressive of great, but--according to the +subject's introspection--not economical concentration. Respiration, +which before and after the test was quite regular, during the test +itself shows a pause. (The tiny waves are due to the heart-beat.) The +subject had thought of 5, and this number is accompanied by a decided +head-jerk. But we note that even before the final jerk a number of less +pronounced jerks occur--the result of poorly regulated psychic tension. + +[Illustration: FIG. 8.] + +[Illustration: FIG. 9.] + +Figure 10 (Schillings) depicts a very high degree of uneconomical +concentration. There was sudden concentration at the beginning of the +test, and a steady increase throughout its course. Accordingly Mr. +Schillings bent forward at the start, and inclined still farther +forward at the second--and just before the third--tap. But at 3 there is +a sudden upward jerk. The number thought of had been 4, tension +therefore had exploded, as it were, too soon. + +[Illustration: FIG. 10.] + +Figure 11 (again of Schillings) gives indications, on the other hand, of +a medium and economic concentration of attention, which is more normal +in character. The number thought of was 4. + +[Illustration: FIG. 11.] + +Figure 12 (Schillings again) is indicative of a low degree of psychic +tension. With the very first tap the head begins to rise and continues +to do so throughout the test. A true final jerk does not occur, we note +rather in all three curves registering the head movements, slight +time-marking movements, especially in the second curve. In the third +curve they are at first minute, but increase steadily in size until the +fourth tap, after which they suddenly disappear. The subject had, as a +matter of fact, thought of the number 4, but it is hardly probable that +Hans would have reacted properly upon these stimuli. + +[Illustration: FIG. 12.] + +Mr. Schillings had thought of the same number in all three tests given +in figures 10, 11 and 12. The probabilities are that if he had been +working with the horse at the time, in the first case Hans would have +reacted with three taps with the right foot and a final tap with the +left, as a result of the questioner's bending forward again after the +premature head-jerk at 3. In the second instance the horse would +probably have given four taps with the right foot, and in the third, the +chances are that he would have continued to tap beyond the 4. + +These curves give, on the whole, a fair idea of the intensity and of the +course of attention of the various subjects. + +Let us now consider a number of records which illustrate the expressive +movements involved in the process of thinking of such concepts as "up", +"down", etc. Their arrangement is identical with the scheme given in +figure 5, with the exception that the tapping curves (the sixth and +seventh) do not appear. The subject was asked to think of any of the +words "up", "down", "right", "left", "yes", "no", etc. He was to begin +to conceive them vividly when the command "Now!" was given. This moment +is recorded in figures 13 to 15 on the fifth curve. What has been said +on page 123 with regard to respiration, holds also in these instances: +only the first rise recorded in figure 14 can be regarded as normal. +The magnitude of these movements varies between 1/2 and 3 millimeters. +The records of the subject whose movements were most extensive, show an +average of 1-7/10 millimeter (based on 50 tests), with a mean variation +of 6/10 millimeter. Lack of space precludes the reproduction of more +than three records. + +Figure 13 (von Allesch) shows the movement accompanying the thought of +"up", a slight raise of the head, recorded in the fourth curve. (The +thought of "down" is accompanied by a corresponding downward movement.) + +[Illustration: FIG. 13.] + +Figures 14 (von Allesch) and 15 (von Manteuffel) illustrate the nod +which is associated with the thought of "yes" in the case of two +subjects. It is essentially the same in both: the head is lowered and +then raised. The first of the two subjects is more decidedly motor, and +his movements therefore were somewhat the more extensive. In the case of +the second subject the nod proper is followed by another which is +somewhat less extensive. + +[Illustration: FIG. 14.] + +[Illustration: FIG. 15.] + +A number of other experiments were carried out which corresponded with +the color-selecting tests made upon Hans. (Page 78.) Five sheets of +white paper, 1/2 meter long and 1/4 meter wide, were arranged in a +series upon the floor, 1/4 meter apart. A dot marked the middle of each. +The experimenter stood at a distance of 7-1/2 meters and directly +opposite the middle sheet. At about 1/2 meter to the right or left of +him stood the subject who took the part of the "horse". The problem of +the experimenter was to indicate to the "horse" a certain one of the +five sheets, but without the use of word or gesture. I at first +undertook the role of "horse", whereas the others consecutively played +the part of questioner. All of them looked fixedly at the sheet which +they had in mind. Besides, it usually happened that they would turn at +least their heads, and often their bodies, more or less in the direction +of the particular sheet--and this without purpose or knowledge on their +part, but purely as a result of concentration upon the sheet they wished +me to point out. One of the experimenters remarked, quite casually, +that he had noted that I always made a better judgment, the more +intently he thought of the sheet. Others often admitted that, when I had +made an error, they had not imagined the sheet vividly, or had been +debating whether or not to decide to think of the neighboring sheet--the +one I had designated. This indecision could be noticed by the direction +of the eyes. But the following table shows how uniform, on the whole, +was the behavior of the various persons when under the guidance of the +same impulse. The number of tests was 200 in each case. All errors were +of the same character. Neighboring sheets were mistaken for each other, +and the errors were never of more than one position to either side. +Their number can easily be obtained by subtracting the percentage of +correct inferences from the total, 100%. + + Experimenter: v. A. B. C. Mrs. v. H. K. Miss v. L. + Correct inferences: 88% 88% 77% 81% 77% 82% + +It will be seen that the number of correct interpretations is quite high +and in none of the cases does it deviate far from the mean average of +82%. + +I based my judgment as to the direction of the subject's eyes, upon an +imaginary line perpendicular to the center of the cornea. (This +perpendicular does not always coincide with the subject's line of +vision, which was the thing I was after, but this cannot be directly +obtained. This, of course, was what made the judgment a rather difficult +matter.) My judgment as to the direction of the head I based largely on +the direction of the nose, (to express it more accurately: upon the +direction of the median plane.) I purposely noted only the position of +the experimenter and not the movement which led up to it. When I tried +to do the latter, the results were not always satisfactory, because the +head and eyes of the person would frequently, in the process of +adjustment, move beyond the goal and thus lead me into error. An attempt +was made to make each judgment as independent as possible of the +preceding one. But usually, after a few tests, an unintentional +association became established between certain attitudes and the +different places in the series of papers. Often all that was necessary +was to observe the experimenter in order to know which of the places he +had in mind, it was not necessary to look at the papers at all. Every +change in the position of the person would, of course, make the +association thus established, useless. + +Later, the subjects and I changed roles, I took the part of the +experimenter and they the part of the "horse". The number of tests in +each case was 200 as before. Here, too, errors were, with but one +exception, never more than of one place to either side. Whether the +error was one place to the right or one place to the left appeared to +depend upon the position of the person making the judgment, i. e., it +depended on whether he stood at my right or at my left. The following +results were obtained: + + Subject ("horse"): v. A. B. C. Mrs. v. H. K. Miss v. L. + Correct inferences: 76% 79% 75% 81% 77% 74% + +A certain agreement can be seen in these results. The average of correct +inferences is somewhat lower than that which was obtained by me (page +135), 77% as over against 82%. This is probably due to the fact that the +subjects had had so little practice compared with me. + +With one of these subjects, Mr. Koffka, a student of philosophy, I +carried these tests somewhat further, varying them partly by increasing +the number of sheets of paper, partly by decreasing the distance between +them. The increase in the number of sheets made only a slight difference +in the results. With 200 tests in each case I obtained the following +results: + + No. of sheets : 5 6 7 8 9 10 + Correct inferences: 77% 72% 72% 69% 73% 68% + +With but few exceptions, the errors were, as a rule, of one place. The +series with an odd number of sheets (5, 7, 9) gave better results than +those with an even number (6, 8, 10). In the tests with the odd number +of sheets the experimenter (K.) stood in front of the middle sheet, so +that it was at the apex of a right angle made by the series of papers +and the median plane of the subject's body; whereas in the case of the +even number of papers the subject stood opposite the space between the +two middle sheets, thus making the position of the sheets less +favorable. + +In the preceding tests the distance between the centers of the +neighboring sheets was always 50 centimeters, so that the angle through +which the median plane of the experimenter's body would have to turn in +order to pass from one sheet to the next, was about 3-3/4 degrees. In +the following tests these distances were gradually decreased. The +sheets, always five in number, were replaced by ever narrower white +strips of paper mounted on dark cardboard and illumined by a Nernst +lamp. The following table shows the decrease in correct inferences +running parallel with the decrease of the angle through which the +subject would have to turn in order to be in line with the several +pieces of a series successively. The percentage in each case is based +upon at least 100 tests. + + Angle: 3-3/4 deg. 3 deg. 2-1/2 deg. 2 deg. 1-1/2 deg. 1 deg. + Distance between the + centres of two neighboring + papers: 50cm. 39cm. 33cm. 26cm. 20cm. 13cm. + No. of correct inferences: 77% 73% 71% 68% 66% 61% + +A curious and unexpected change was here noted in the subject, Mr. +Koffka, who, while concentrating his attention to the uttermost, began +unawares to develop a new system of expressive movements of the head. +When the distance between the sheets was relatively great, he had been +in the habit of turning his head and eyes in the direction of the sheet +intended, and as the distances became less he had reacted only by a +turning of the eyes. But now, as the distances were still further +decreased, he began again to react by means of head movements, and these +were of exaggerated magnitude, for which he would compensate, as it +were, by an eye-movement in the opposite direction. Although the head +movements decreased in scope as the distances between the sheets were +steadily decreased, they still were always decidedly greater than the +eye movements, which I was now normally led to expect and which could be +judged without much difficulty. This form of reaction was much more +satisfactory as a cue, and therefore it came to pass that, whereas in +the preceding series I had made only 60% correct inferences when the +angle was 1 degree, I now found that--the angle remaining the same--80% +of my inferences were correct. (My final judgment I continued to base, +as before, upon the position, and not upon the movement, of head and +eye). The number of correct inferences continued relatively high, even +after the distance between the papers was decreased tenfold,--as will be +seen from the following table: + + Angle: 1 deg. 30' 15' 9' 7' 6' 5' 3' 2' + Distance between the + centres of two neighboring + papers: 131 65 33 20 15 13 11 6-1/2 4mm. + Percentage of correct + inferences: 80 79 78 81 84 80 77 68 68% + +Beginning with an angle of 1' (distance between the centers of two +neighboring papers = 2 mm.), the subject was unable to focus, with +sufficient steadiness of vision, upon one paper alone, and the +movements, for that reason, ceased to manifest themselves. Comparing the +results obtained in the case of this subject with those obtained from +two others, whose reactions had remained normal, B. and Miss St., we +find that with them there were only 53% correct inferences in both cases +(based each upon 200 tests), when the angle was 5'. In my errors, too, I +often shot wider of the mark. In another series of 200 tests, in which +Miss St. "merely thought of the places", I had a percentage of 56% +correct inferences, and my errors did not become any coarser. Miss St. +believed this a case of true telepathy, but I had been guided in my +judgments entirely by her unwittingly made movements--or rather the +direction--of her eyes. The magnitude of these movements bore a constant +relationship to the distance between papers as it was conceived by the +subject. + +Reviewing the experiments discussed in this chapter, we find that the +same kind of movements and postures, which had been noted in persons +experimenting with the horse, tended to recur in the laboratory, in so +far as the mental attitude of the subjects, given in their introspective +accounts, corresponded with that of the questioners of the horse. + + + + +CHAPTER V + +EXPLANATION OF THE OBSERVATIONS + + +The author having described the observations made upon the horse, and +having discussed the activities of the questioner upon the basis of +observations made objectively and upon his own introspections, and +having verified the results thus obtained, by means of laboratory +tests,--we are now in a position to solve satisfactorily all the +problems which this interesting case has presented. + +That which is least difficult to understand is the horse's seeming +knowledge of language and particularly his ability to answer questions, +no matter by whom, or in what dialect, they were put. As a matter of +fact, it made no difference who desired an answer, for the only person +upon whom the experiment depended was the questioner, that is, the one +who asked the horse to tap. We have everywhere designated this person as +the experimenter or questioner. It was he who gave the directions, and +since all that were involved were visual signs, the drama in which Hans +appeared as the hero, was nothing but a pantomime. All speech was +superfluous and, except in so far as the tone of voice in which it was +spoken was soothing or reprimanding, it was quite unintelligible to the +horse. + +From the foregoing, the reader understands without further explanation +Hans's ability to count and to make computations. If the number of taps +had depended solely upon the length of time and the angle at which the +questioner bent forward, the horse would have been able to tap any +number desired. Since, however, only the right foot was employed, the +left one being used at most for making a final tap, the number of taps +had an upper limit which was due to the fatigue of the animal. This +limit was about 100. That it was possible to ask such questions as: "How +many times is 100,000 contained in 654321?", and thus to give problems +involving millions, is perfectly clear. + +All wonderful feats of counting and computation which were accomplished +while thus experimenting with the horse are to be accredited, not to the +horse, but to the questioner. If such is the case, they certainly cannot +be considered astonishing. Thus, when to the question, "How many of the +gentlemen present are wearing straw hats?" the horse answers correctly +in accordance with the wording of the question and omits the straw hat +of a lady, then Mr. von Osten is the guide. It is no wonder that Hans +never showed the slightest excitement when confronted with difficult +problems, nor that it apparently took no time whatever to solve them. + +Hans, however, was also a faithful mirror of all the errors of the +questioner. Aside from mistakes due to occasional interruptions on the +part of visitors, these errors had two sources: faulty computation and +inadequate concentration--i. e., aside from arithmetical errors on the +part of the questioner, were his premature or belated movements. Since +both of these factors might be operative, the following three +possibilities arise. + +(_a_) The questioner computes correctly but does not move at the proper +moment. Nearly all the errors which had been accredited to the horse, +were of this kind. + +A part of these errors had the appearance of being significant, that +is, they might be interpreted as a misapprehension of the question. If, +for instance, instead of a sum only one of the quantities was given, or, +if instead of a product only one of the factors was given, it might be +interpreted that the horse simply wished to repeat the problem. Thus, +Mr. von Osten in response to the question: "How much is 3 times 5?", +twice in succession received the answer, "3", and upon my question, "How +much is 3 plus 4?" he answered, "3", and to "How much is 2 times 6?" he +tapped 6, and to "What is one-fourth of 36?" 4. In part (certainly in +the second and third example cited) an individual quantity or factor had +been emphasized in the consciousness of the questioner (cf. page 105) +and in part the reactions were due to chance. Thus, when Mr. Hahn asked +the question: "What is one-half of 10?", he received the following +responses: 2 and 10, and then 17 and 3. To this class belong also, the +tests made by the Commission of September and reported in Supplement +III. (See page 255). + +Other errors, even though they may not have appeared to be significant, +might yet have been characterized as mistakes due to speed; as when, e. +g., Hans made an error of one unit--and sometimes, though less +frequently, of two units--too much or too little in his response. One +might be led to believe that Hans had not made an error of calculation +but merely of counting in the process of giving his result, which always +had to be done by the cumbersome method of tapping. As a matter of fact, +the trouble lay in the wrong degree of concentration on the part of the +questioner: In errors of +1, tension was too slight, in those of -1, it +was too great (see page 91). This comes out clearly in a comparison of +the two more extensive series which I took in the case of Mr. +Schillings. During the first series, he was well disposed, and was able +to concentrate effectively, while during the second, he was nervous and +easily diverted. This difference in intensity of concentration in the +case of the two series is attested, not only subjectively by Mr. +Schillings's introspective statement, but may be measured objectively by +means of the number of final taps which the horse gave with his left +foot during these two series. We saw (page 94) that these final taps +were always a sign of intense concentration and, as a matter of fact, +one-half of the horse's responses to Mr. Schillings during the first +series were made in this way; whereas, in the second series, only +one-third were of this sort. (I, myself, was never able to get, without +conscious control, a greater number of this type of response.) We may +therefore say that, in the first series we had a high degree of tension, +or concentration, whereas, in the second series, we had a low degree. +The errors distribute themselves over the two series as follows: + + +1 +2 -1 -2 + Series I (31 tests) + Correct responses: 87% + Incorrect " : 0% 0% 13% 0% + Series II (40 tests) + Correct responses: 40%. + Incorrect " : 40% 8% 2.5% 0% (and 9.5% + other kinds of errors.) + +We find in Series I no "+1" errors, but only "-1" errors; in series II, +on the other hand, the errors are almost exclusively of the "+1" +category, equaling the number of correct responses, and there is only +one "-1" error. A series obtained in the case of Mr. von Osten is almost +as satisfactory an illustration. When he first began to take part in +tests in which the procedure was the one we characterized as "without +knowledge" and had to note their complete failure, he was thrown into +such confusion that the responses in the case of procedure with +knowledge were also incorrect. The errors there were always +1, (whereas +those in the case of procedure with knowledge, which were due to quite +different causes, were very great and inconstant.) The number of +1 +errors obtained on this occasion comprises one-fourth of all the plus +errors which were ever obtained in the case of Mr. von Osten during the +entire course of these experiments. Finally, I would mention two +examples of my own. In the course of my very first attempts with Hans I +obtained, as I said on page 89, three responses in a total of five which +exceeded the correct result by 1. This I would explain by the fact that +although I employed a high degree of concentration, I nevertheless was +somewhat skeptical. The result was a certain deficiency in the degree of +concentration. A second example which I would cite is taken from the +period in which I had already discovered the cue to Hans's reactions and +goes to show that I was then still able to eliminate the influence of +this knowledge and to work ingenuously. To the question, "How much is 9 +less 1?" I, momentarily indisposed, received the answer 10, and then six +times in succession the answer "9", and finally the correct response, +"8". + +Errors of another kind--the not infrequent offenses against the very +elements of counting and the fundamental arithmetical processes--were +regarded in part as intentional jokes and by an authority in pedagogy as +a "sign of independence and stubbornness which might also be called +humor". Hans emphatically asserted that 2+2 was 3 or he would answer +questions given in immediate succession as follows: "How many eyes have +you?"--2. "How many ears?"--2. "How many tails?"--2. These errors, as a +matter of fact, evince neither wit nor humor, but prove incontrovertibly +that Hans had not even mastered the fundamentals. + +Many of the errors baffle every charitable attempt at interpretation. +These gave the horse the reputation of capriciousness and unreliability. +If Hans designated the tone "e" as the seventeenth, or "g" as the +eleventh, or when he called Friday the 35th day of the week or believed +50 pfennige to be worth only 48, the cause for these responses lay +either in the insufficient degree of tension on the part of the +questioner (as in the first three examples) or in the extravagant +expenditure of the same (as in the last case). If, therefore, the horse +at times would "hopelessly flounder" which would seem to be indicated by +tapping now with the right and now with the left foot, then as a matter +of fact, this form of reaction came about as was described on page 61, +with this difference that there we had to do with voluntary controlled +movements on the part of the questioner, whereas here, they are the +result of an unsuitable degree of tension which expressed itself in +frequent and disconcerting jerks. Besides the answer 3, this so-called +floundering was the only reaction the average person could obtain from +the horse in the absence of Mr. von Osten and Mr. Schillings. It would +however occur also in the case of these gentlemen and would be received +by them with resentment when in truth it was Hans's greatest feat, for +he showed his extremely keen reaction upon every movement of the +questioner. To this group belong also the errors in the case of higher +numbers, the sole cause of which lay in the difficulty with which +tension could be maintained and the body kept motionless for so long a +period. These errors occurred in accordance with a certain law. If, for +instance, a certain test repeatedly evoked incorrect responses, the +questioner would gradually increase the duration of tension and would +thus come a little nearer to the desired goal with every test. In this +way, Mr. von Osten desiring 30 as an answer obtained consecutively the +responses, 25, 28, 30; and I, myself, for the answer 20, received +consecutively the responses 10, 18, 20 (see also the laboratory tests, +page 105). Sometimes too, the questioner would flag in his efforts +before the goal was reached. Thus in one of my first tests, I received +for the answer 11 the following responses: 1, 4, 5, 7, 4. I was unable +to get beyond 7. In other instances, the horse responded first with too +few and then with too many taps. The correct response therefore could +only be obtained after an appreciable amount of gauging of tension, as +in target practice there must be a gauging of distance. (See page 92). +In this way Mr. von Osten obtained for 10 the responses 8, 8, 11, 10, +and Mr. Schillings for 17, received 9, 16, 19, 18, 18, 14, 9, 9, and +finally, after some efforts, 17 taps. Thus there was a rise from 9 to +19, then a fall back to 9 and after eight tests the correct response. As +long as we attempt to explain this fact as error on the part of the +horse, so long will it remain inexplicable, but the moment we regard it +from the point of view of the psychology of the tension of expectation, +it becomes perfectly plain. + +The same holds true for the curious predilection which Hans appeared to +have for the numbers from 2 to 4, especially for 3 (see page 68). As a +matter of fact the cause of this lies in nothing other than the +inadequate concentration of attention on the part of the questioner and +less often in an extravagant expenditure of concentration, which +explodes immediately after the first tap on the part of Hans (as in the +case of my first tests); but usually the cause lay in a complete lack of +concentration, though the same result may be produced by various causes. +It is usually after 2 to 4 taps of the horse's foot that the questioner, +who does not concentrate, makes his first move which naturally puts an +end to the tapping on the part of the horse. As a rule this jerk follows +immediately upon the second tap. (On the other hand, relaxation of +attention is very difficult upon the first tap. See page 95). The +questioner, however, would expect further tapping and therefore would +not bring his body back to a completely erect position and the result +would be a 3, the last unit of which would be given by the final tap +with the left foot. Here we also obtained light as to the answers which +Hans gave in those tests in which the method was that of "procedure +without knowledge". These responses had nothing to do with the problem, +for neither the horse nor any one else knew the solution. But in the +horse's responses the degree of tension of the questioner's +concentration was faithfully mirrored. An experimenter who was as +skillful in concentrating as Mr. von Osten, obtained--almost without +exception--very high numbers, whereas one whose concentration was slight +would receive in response to nearly all questions the answers 2, 3 or 4. +Thus, the Count zu Castell received in response to seventeen questions +the answer 2, three times, the answer 3, six times, and the answer 4, +four times, two answers being accidentally correct. + +Another group of errors was characterized as stubbornness on the part of +Hans, such as his persistence in repeating an incorrect response, or his +repetition of a former correct answer in response to later questions +where it was perfectly senseless. During a demonstration before a large +number of persons, I held a slate with the number 13 upon it within the +horse's view and also within view of the spectators. I, myself, did not +know what number was written on the slate. Having been asked to tap the +number, Hans responded by tapping 5. The grand-stand shouted "Wrong!" I +asked Hans to try again. Four times in succession he answered 5. At +another time Mr. von Osten and I each whispered a number (7 and 1, +respectively,) into the horse's ear and asked him to add the two. Three +times in succession he tapped 11. After the test had been repeated in +accordance with "procedure with knowledge" and a correct response had +been received, we tried once more a test of "procedure without +knowledge". Again, he responded with an 11. On a third occasion, I asked +Hans to tap 5. He responded with a 4 and then, correctly, with a 5. +Thereupon, I asked him to tap 6. Again, he responded with a 4. Then I +asked him to tap 7. Once more he responded with a 4, and only when I +proceeded to count aloud did he tap 7 correctly. I had him repeat the 7 +and then went over to 9. Promptly he responded with another 7. In these +cases, which by-the-way were not very frequent, we have to do, not with +stubbornness on the part of Hans, but with the persistence of that +number in the consciousness of the questioner. Modern psychology has +recognized this tendency of ideas, which have once been in +consciousness, to reappear on other occasions even though they are +wholly inappropriate. It has been termed "perseverative tendency." +(Perseverationstendenz).[21] + +While the errors thus far discussed appeared sporadically in long series +of correct responses, there still might be observed at times a massing +of errors, usually at the beginning of a day of experimentation or at +the beginning of a new series. We were regularly told that Hans always +had to have time to adjust himself to new circumstances. The records +often showed comments such as these: "After a number of practice tests +the horse appears particularly well disposed", or "Hans, at first +inattentive, does not respond. Suddenly he gets the hang of things". +Different questioners who worked with the horse required different +lengths of time to obtain proper responses. Some needed a quarter of an +hour, others scarcely half a minute. I, myself, found that in the degree +in which I learned to control my attention, in that degree did this +phenomenon tend to disappear, but would reappear the moment I became +indisposed. From this we see that, instead of attributing all sorts of +mental characteristics, such as stubbornness, etc., to the horse, we +should lay them to the account of the questioner. As a matter of fact we +find that this "getting into the sweep of things", i. e. the overcoming +of psycho-physical inertia, has long been known in the case of man and +has been experimentally determined and called "Anregung" (excitation) by +the psychiatrist, Kraepelin,[22] and his pupil, Amberg.[23] A massing of +errors toward the end of a long series occurred only when the questioner +was fatigued. There was nothing which had to be interpreted as fatigue +or as indisposition on the part of the horse, (except in the few cases +of very large numbers, cf. page 67). To be sure, Mr. von Osten always +offered these two excuses. That they were without warrant is shown by +the fact that Hans, after appearing indisposed or fatigued while working +with one questioner, would nevertheless react promptly and correctly a +moment later for some other experimenter, and furthermore, when working +with me, the number of his correct responses would rise or fall with my +own mental disposition. + +Finally, I would here note a rather interesting observation for which I +am indebted to Mr. Schillings and the Count zu Castell. They had +noticed, independently of each other, that the horse would often fail to +react when for any length of time he was given problems dealing with +abstract numbers, even though they were of the simplest kind; but that +he would immediately improve whenever the questions had to do with +concrete objects. They believed that Hans found applied mathematics more +interesting, and that abstract problems, or those which were altogether +too elementary, bored him. The Count zu Castell furthermore noticed that +the responses tended to be more correct as soon as he had the horse +count objects which he, himself, (Castell) could see during the test. +Quite in accord with this is the statement to be found in the report of +the September-Commission, in which we find this note in a discussion of +the arithmetical problems (not involving visible objects), which the +gentlemen already mentioned had given the horse. "The horse responded +with less and less attentiveness and appeared to play with the +questioner." Here again, that was looked for in the animal which should +have been sought in the man. Mr. Schillings was capable of intense, but +not continued concentration and it was he who was bored, and not the +horse. And it was the Count zu Castell and not the horse that found it +necessary to invoke the aid of perceptual objects to bring his +attention to the proper height of concentration. + +The reader will see that thus far I have supposed the horse to be a +never-failing mechanism and that I have placed all errors to the account +of the questioner. The horse never failed to note the signal for +stopping and therefore never was the immediate cause of an error. It is +not to be denied that now and then he would cease tapping spontaneously +and in this way would become the cause of an error. We have no data on +this point, but undoubtedly the horse's share in the total number of +errors was very slight. + +(_b._) Another source of error was faulty computation on the part of the +questioner. The questioner made the signal for stopping when the +expected number of taps had been reached. The horse faithfully mirrored +the miscalculation of the questioner. I have knowledge of only one such +case. The journals report that once Mr. von Osten, when someone called +to his attention that Hans had indicated the wrong day of the week, +replied: "Yes, you are right, it was not Thursday, but Friday," +whereupon Hans being asked again, promptly responded correctly. This +appeared to the reporter in question as proof of the subjective +influence of Mr. von Osten upon the horse. + +(_c._) When errors in calculation and failures in proper concentration +combine, i. e. when the questioner makes a mistake in calculation +because he is excited or inattentive and for the same reason does not +make the movement, which is the signal for stopping, in accordance with +the number which he deems to be the correct answer, then the result is +usually wrong, but it may be correct in the few cases in which the two +errors exactly compensate each other. Nothing has been so effective in +establishing Hans's reputation, nothing has brought him so many +followers, as these cases in which he, rather than his mentor, has been +in the right. Compared with the mass of cases in which Hans was wrong +these latter cases are diminishingly few in number, yet these few made +such an impression upon the observers that their number tended to be +overestimated. As a matter of fact, I have been able to discover records +of only seven such cases. Two of these were reported by the Count zu +Castell. On the 8th of September, he entered the horse's stall, alone, +and believing it to be the seventh day of the month, he asked Hans the +date. The horse responded correctly with 8 taps. At another time he held +up before Hans a slate on which were written the numbers 5, 8 and 3 and +asked the horse to indicate their sum which in the momentary excitement, +vaguely appeared to Castell to be 10. To his chagrin he noticed that +Hans continued to tap. Thereupon he intentionally remained motionless +until the horse had stopped tapping spontaneously--as he thought--at 16. +(The newspapers reported that the numbers to be added had been 5, 3, and +2; that the questioner had expected the answer 11, but that Hans had in +three tests always ceased tapping at 10.) In both cases the questioner +regarded the answers of the horse as wrong and recognized his mistake +when his attention was called to it. I, myself, had the same experience. +One time I received in response to the question, "What day of the week +is Monday?", the answer 2, although I had expected the answer 1; at +another time I asked, "How much is 16 less 9?", and the horse responded +with 7 taps, although I had erroneously expected 5. I noticed my mistake +only when my attention was called to it by one of those present. Another +example is related by Mr. Schillings. A row of colored cloths lay +before Hans. Beside them stood an army officer. Pointing to the latter's +red coat Mr. Schillings asked the horse to indicate, by means of +tapping, the place in the row where a piece of the same color lay. Hans +tapped eight times, but Mr. Schillings reprimanded him because the red +piece was, as a matter of fact, second in the row. Upon a repetition of +the test, Hans again tapped 8. (By some, the facts are recounted as +having been the other way round; viz.: Hans tapped 2 instead of 8. This +of course would call for a different explanation.) It was noticed that +at the place which would be indicated by eight taps there was not a red +piece but a carmine colored piece of cloth. A newspaper reports, +somewhat vaguely, a sixth case as follows: Hans was asked to spell the +name "Doenhoff" and began correctly: "Doe". Mr. von Osten, who somehow +began to think of another name, "Dohna", interrupted him and wished to +correct him by suggesting o instead of oe (i. e., 2 taps instead of 3). +Hans, however, continued to spell the entire word with the greatest +equanimity. He had not erred. A similar experience is reported by Mr. H. +von Tepper-Laski, the well known hippologist. Although the details have +slipped from his memory, he reports that in the case in question the +correct answer was thrice refused by the questioner who thought that the +horse's answer was incorrect. Hans, upon being severely reprimanded in a +loud and harsh tone of voice, turned about as if disgusted with the +injustice of the man and made straight for his stall.--It is clear that +in the cases described we are not dealing with accidentally correct +responses, for in nearly every case the test was repeated a number of +times and the same responses were received each time. As a matter of +fact, my own introspection convinced me that the third and fourth cases +were surely, and the first and sixth were very probably, due to +insufficient concentration on the part of the questioner. Accordingly +there is everywhere in these cases a difference of +1 or +2 between the +number thought of and the number tapped (see page 92 f.). The data in +the second and fifth and still more in the seventh case were too meager +to warrant an attempt at explanation, for it is not even known whether +Hans responded with more or fewer taps than was expected by the +questioner. It is unfortunate that a more complete record was not made. + +The frequent and intentional attempts of Mr. von Osten to induce the +horse to give an incorrect response,--which, by-the-way, were regularly +unsuccessful--belong only apparently to this group. Thus he asked, e. +g., "2 times 2 is 5, is it not?" "3 times 3 is 8?", etc., but Hans +refused to be misled, and responded correctly. This was from the very +beginning one of the main arguments for independent thinking on the part +of the horse. The actual procedure was as follows, even though the +questioner had said "2 times 2 is 5", there still was present in his +consciousness the number 4. I, myself, would think either of the first +member of the equation, i. e., 2 times 2, in which case Hans would +respond with 4 taps or I would have in mind the second member, i. e., 5, +in which case he would respond with 5 taps. Never did I succeed in +thinking of both at the same time. The association between the thought +"2 times 2" and the concept "4" is so close and supported by so many +other associations that the attempt to form a new one, that is at +complete variance with all these, is futile. One may say "2 times 2 +equals 5" but it is impossible to conceive it. + +Let us turn now, from the tests in counting and computation to those in +reading. We have seen that Hans manifested his seeming knowledge of +language symbols in a threefold manner: he might approach a slate on +which was written the symbol asked for, or he would indicate its +location in a series of slates by means of tapping, or finally by means +of so-called spelling of the word which was written upon a slate or +placard. The responses by means of approaching a placard were very often +unsuccessful, while indications by means of tapping were scarcely ever +unsuccessful. If it were true that higher intellectual processes[T] were +here involved, then the converse would have been expected, for tapping +required not only the ability to read, but also the ability to count. +If, on the other hand, we assume that the horse simply followed the +directions given by the questioner's movements, this seeming difficulty +resolves itself, for it would be more difficult for Hans to perceive the +signs which he receives while moving than those which he receives while +tapping. When we recall that it was easier to direct the horse to a +placard near the end of a row than one nearer the center (see page 81), +we can readily understand how it was that during the experimentation +carried on by the September-Commission (Supplement III; page 255), Hans +was able to point out immediately the placards on which were written the +names "Castell" and "Stumpf", for they were at the two extreme ends, but +was unsuccessful in locating the one on which was written the name +"Miessner" which was not a bit more difficult to read, but was located +at the fourth place in the row. He first approached the fifth card, then +upon repetition of the test he pointed out the other neighboring tablet, +viz., the third. + + [Footnote T: Professor Shaler[24], a well-known American savant, + mentions a three-year old pig belonging to a Virginian farmer, that + was able to read and had some understanding of language. From + numerals which were written upon cards and spread out before it, + this pig could compose dates. It could also select from among + certain cards one upon which was written a given name, asked for by + the master. Supposedly no signs of any kind were given. (Shaler + thought to exclude effectively the sense of smell, which is so + highly developed in the pig, in that he, Shaler, himself smelled at + the cards, since he also "possessed an acute olfactory sense!") + Since we are told that the farmer in question made a business of + supplying trained pigs for exhibition purposes, the case appears + suspicious. We hear of a pig exhibited in London, that was able to + read and spell, and could also tell the time by the watch[25]. We + cannot tell, however, whether the two pigs, which beyond a doubt + were mechanically trained to respond to signals, are identical or + not.] + +In spelling, Hans was quite indifferent whether his table with the +eighty-four number signs upon it stood before him, for he had no +knowledge of letters. Neither Mr. von Osten nor Mr. Schillings required +it, for the former knew the table by heart and Mr. Schillings told me +that before every test he made a note of the numbers which were +necessary to indicate the required letters, trusting in this way to +control the responses of the horse and never guessing that by so doing +he was making it possible for the horse to answer correctly. The +newspaper reports aroused much interest at the time by stating that Hans +was able to spell such proper names as "Plueskow" and "Bethmann-Hollweg", +even to putting in the difficult "w" and "th". The friends of Mr. von +Osten at the same time called attention to the exquisite auditory +acuteness of the horse which enabled him to perceive the aspirated "w" +and to discriminate between the "th" and "t", (the "th" is softer than +the "t" in German.--_Translator_). This explanation, of course, must +have appeared somewhat daring even at that time. + +Hans was quite guiltless of the many limitations imputed to him +concerning his knowledge of symbols. That he was unable to read capitals +or Latin script was merely a vagary of the master, like the belief that +it was necessary to confine one's self in one's questions to a certain +vocabulary and to a certain form. Mr. von Osten's apparent failure to +elicit responses from the horse on topics of which it was ignorant is a +beautiful illustration of the power of imagination. Mr. von Osten was +convinced from the very first that Hans could not answer such questions. +When the belief in success was lacking, of course there was not the +requisite amount of concentration which, alone, leads to perceptible +expressive movements and thus elicits a successful reaction on the part +of the horse. + +Mr. Schillings, owing to his great impressionability, remained long +under the spell of Mr. von Osten's point of view. Thus I find in the +record of the September-Commission that the question "How much is 3 plus +2?" was answered incorrectly by Hans, but he responded correctly the +moment Mr. Schillings replaced the word "plus" which was "tabooed", by +the word "and". For a long time also he could receive no response to +questions put in French until one day he made the discovery that, +curiously enough, the animal never responded adequately unless he +himself firmly believed in the possibility of success. It is noteworthy +that the Count zu Castell, independently of Mr. Schillings, made the +same discovery. Mr. Schillings made his curious discovery--which he was +unable to interpret, but which aroused some suspicion--on the following +occasion. One day--whether accidentally or because his prejudice was +temporarily overcome--he commanded; "Dis deux!". Hans responded promptly +with 2 taps. He was greatly surprised and believed that Hans had gotten +hold of the French by hearing it spoken in his environment. Possibly he +understood also "trois" and "quatre"? He put the questions and received +correct responses. He asked again, "dix", "vingt", and so on to +"soixante". At "soixante-six" he became doubtful. Indeed, Hans failed +him. At "quatre-vingt", the game began again. "Cent", again, succeeded. +The old saying that "Faith will move mountains" was verified once +more.[U] + + [Footnote U: It has been scientifically proven that a number of + supposed mystical phenomena, table-moving, table-rapping, and + divination by means of the rod, all are the result of involuntary + movements made unawares by those concerned, just as in the case of + this work with Hans. (We must of course except those not infrequent + instances in which the phenomena in question are purposely and + fraudulently simulated.) There is this difference, however, that + there the thing affected is a lifeless object,--the table or the + rod,--here it is a living organism, the horse; hence there the + immediate effect of the movement is physical work in the form of + energy expended in moving the table, here the movement becomes a + visual stimulus. A number of observations which I find in the + relevant literature, and which I shall introduce into this chapter, + may serve to show how close is the similarity between the two cases, + how much depends upon the questioner, and how little really upon the + instrument--whether table or horse--which is acted upon. + + Two examples will suffice to illustrate the significance of belief + and of the concentrated attention that results from it. The first is + taken from the letters of Father P. Lebrun on the divining rod[26], + which appeared in 1696. An old woman once told a treasure-seeker + that she had always heard that a treasure was buried at a certain + place in the fields. The man, who was known as an expert in the art + of using the divining rod, immediately set out to locate the gold. + Lo, and behold, the moment he set foot on the spot described by the + old woman, the branch turns downward, and from its movements the man + gathers that twelve feet below ground there lies buried some copper, + silver and gold. He calls a peasant to dig a pit eleven feet deep, + then he sends him away so that no other should get into the secret. + He himself digs a foot deeper, but all in vain, for he finds + nothing. Standing in the pit, he again takes up the branch. Again it + moves, but this time it points upward, as if to indicate that the + treasure had disappeared from the earth. Dismayed, he climbs out of + the pit and questions the branch a third time. This time it points + downward once more. He climbs back into the pit. Presently he feels + the prick of conscience (for in the 17th century many regarded the + dipping of the divining rod as the work of the Devil). Terrified, he + exclaims: "O God, if the thing I am doing here is wrong, then I + renounce the Evil One and his rod (s'il y a du mal, je renonce au + demon et a la baguette)". Having spoken, he once more takes the rod + in hand to test it. It does not move. Horrified, for now there was + no longer any doubt that Satan was the cause of its movements, the + man makes the sign of the cross and runs away. But he had hardly + gone more than two or three hundred paces when the thought strikes + him: Is it really true that the branch will no longer move for him? + He throws a coin to the ground, cuts a branch from a bush nearby, + and is overjoyed when he notes how it dips down toward the money. + + Another example is to be found in a report of the well-known + physicist, Ritter[27], of Munich, which appeared during the early + part of the 19th century. Ritter, a man with a bent for natural + philosophy and metaphysics, describes an instrument which was to + replace the divining rod, and which he called "balancier." It was + simple enough, consisting of a metal strip that was balanced + horizontally upon a pivot, and was supposed to be put into motion in + the presence of metals. Ritter used this instrument in his numerous + experiments with the Italian Campetti, a man who had achieved a + measure of fame in Europe for his ability to discover springs and + metals by the use of the divining rod. Carrying the "balancier" on + the tip of the middle finger of his left hand, Campetti--whose + integrity one cannot cavil at--had to touch repeatedly a plate of + zinc or pewter, and had to count aloud the number of touches he + made. The following curious law was found to obtain (that was + probably suggested to the subject by Ritter without his being aware + of it): with the first contact the "balancier" turns to the left, + with the second to the right, and with the third it remains at rest. + At 4 it turns once more to the left, at 5 to the right, at 6 it + remains at rest, etc. It remained immovable only at the so-called + trigonal numbers (3, 6, 9, 15, 21, etc.). Ritter tells us that when + Campetti did not really count or did not think of the number, then + it would not have any influence whatever upon the action of the + instrument. This Ritter ascribes to the agency of electricity (which + in the 18th and 19th centuries was made to play very much the same + role that Satan had played in the 16th and 17th centuries). + + The similarity of these two cases and that of Mr. Schillings is + evident. When the questioner of the horse and the bearers of the + "balancier" and of the divining rod are confident of success, they + succeed. When they do not expect success, they fail.] + +Hans's seeming knowledge of the value of coins and cards, of the +calendar and the time of day, as well as his ability to recognize +persons or their photographs, can now be readily understood. In all of +these cases, we had to deal, in so far as knowledge is concerned, only +with that of the questioner,--the horse simply tapped the number the +questioner had in mind. The meaning which was supposed to be expressed +by the tapping never existed as far as Hans was concerned; it was only +in the mind of the questioner that the concepts: ace, gold, Sunday, +January, were associated with "1", etc. The same was true with regard to +all other wonderful feats of memory. The sentence: "Bruecke und Weg sind +vom Feinde besetzt", (The road and the bridge are held by the enemy), +which was given to the horse one day and correctly repeated by him on +the following day, was not an answer elicited from the horse by means of +a question, but rather a system of automatic reactions which were +induced by certain involuntary movements of the questioner as stimuli. +Far from showing a wonderful memory in these feats--as is claimed for +him by the very non-critical compiler, Zell[28]--Hans, on the contrary, +has at his service a remarkably small number of associations. For, +besides possessing the powers of any ordinary horse, he recognizes only +a few meager visual signs. To be sure, we find in the literature a horse +that was said to have recognized 1500 signals,[29] but all proof is +lacking and the report is so meager that we cannot discover whether +these signs were auditory or visual.[V] + + [Footnote V: The French investigators Vaschide and Rousseau make a + reference to this case, and mistakenly state the number of signals + as 1500 instead of 115[30]. Ettlinger[31] takes over this wrong + figure and makes the additional mistake of assuming that the + reference is to an original investigation made by the two + Frenchmen.] + +Having thus disposed of all questions concerning the horse's apparent +feats of reason and memory, let us turn to those in the field of +sensation. We shall begin with vision. That Hans was unable to select +colored pieces of cloth merely upon the basis of color quality, without +reference to their order, was shown in Chapter II. It would, however, be +somewhat hasty to infer color-blindness from this fact, as did +Romanes[32] on the basis of similar unsucessful responses on the part of +a chimpanzee ("Sally" of the London Zooelogical Garden). It is much +easier to explain the failure of the horse than that of the monkey on +the basis of intellectual poverty, a poverty of associative activity. It +presumably can discriminate between the various colors, but it cannot +associate with these their names. The existence of chromatic vision in +the lower forms is by no means as unquestionable as is assumed by +popular thought. Even teleological considerations which are often +brought forward (especially that of the ornamental and protective +coloring of so many animals) can never do more than establish a certain +probability. For definite proof, we need data given by observation (we +have none in this case), or experimental evidence. Such evidence we +have, but it is insufficient in quantity and unfortunately most of it +was obtained under inadequate experimental conditions.[W] We know +nothing regarding chromatic vision in the horse, though we have often +had trained horses which apparently possessed color discrimination. The +earliest report of this kind I find in a work published in the year +1573.[36] Here we read that a number of Germans exhibited two horses in +Rome which could, upon request of their masters, point out those persons +among the spectators who were wearing stockings of any designated color. +The passage, "conoscevano i colori", (they recognized the colors,) +proves nothing and no one has ever heard, even in modern times, of a +horse that actually knew colors. + + [Footnote W: All told, there are hardly more than half dozen + experimental investigations of the color-sense in mammals,--to speak + only of these. Three of them deserve especial mention. One, the work + of the American, Kinnaman,[33] on two Rhesus monkeys. Then a brief + but careful piece of work by Himstedt and Nagel.[34] These two + investigators were able to determine that their trained poodle could + distinguish red of any tone or shade from the other colors, and from + Professor Nagel I learned that later the tests were extended and the + same was shown to be true concerning the blue and the green. And + finally there is an investigation which hitherto has been known only + from a reference which Professor Dahl,[35] the investigator, himself + makes. The work is on a monkey, Cercopithecus (Chlorocebus) + griseoviridis Desm. (Professor Dahl has kindly allowed me to look + over the records of the experiments. He intends to publish the + monograph at an early date.) + + All of these investigators arrive at the conclusion that the animals + tested by them possess color-sense. The monkey last-mentioned shows + one peculiarity: it was unable to distinguish a saturated blue from + the black. It will require further tests to clear this up.] + +Nor did Hans possess anything like that high degree of visual acuity +which had been attributed to him. He was supposed to be able to read +easily at a distance small, almost illegible script, which we ourselves +could decipher only with the greatest difficulty close at hand. It was +also supposed that he could distinguish ten-and fifty-pfennig pieces +whose faces had become worn beyond recognition for us. None of these +accomplishments have stood the test. We have no reason to believe that +Hans can see the objects about him more clearly than other horses, +regarding whom one usually assumes that they receive only vague visual +impressions. Horses do not as a rule seem to be near-sighted as is often +asserted by the layman, but rather somewhat far-sighted, or if we may +believe Riegel,[37] who tested some six hundred horses, they probably +have normal vision. But we are told that many horses--and according to +some authors all--have an innate imperfection which detracts +considerably from the clarity of vision. This imperfection consists in +an irregular formation of the sclerotic coat and of the lens of the +eye.[38] The two organs do not have the same refraction in all parts. As +a result, objective points are not imaged as points upon the retina. +(Hence the name: astigmatism, i. e., "without points", for this +disorder.) The retinal image of the object is not only vague, but also +distorted.[X] + + [Footnote X: There is no justification for the wide-spread belief + that the horse which on account of the greater size of his eye (more + correctly, on account of the greater focal distance) receives larger + retinal images of objects than does the human eye, for that reason + also sees objects, larger than we do. Horses' shying is often + explained in this way. But the conclusion just mentioned is + erroneous. The retinal image is not the perceptual image. It + undergoes many transformations within the nervous system itself.] + +Many will doubt whether with such imperfect images an animal can react +to directives so minute, as we have asserted to be true in the case of +Hans. In considering this question we must distinguish between the +directives for pointing out colors and the directives for tapping and +for head movements on the part of the horse. In pointing out and +bringing forth pieces of colored cloth there is involved the perception +of an object at rest, viz.: the direction of the questioner who is +standing quietly; whereas in the case of responses by means of tapping +the stimulus is the horse's perception of the questioner's movements. +Now, the construction of the horse's eye, as described above, is not +favorable for the perception of objects (so-called acuity of vision). +This may partly account for the slight success of the horse in those +tests in which he was required to select a piece of cloth of a +designated color, in so far as these commands were not accompanied by +calls or exhortations. Where human observers averaged eighty per cent +correct responses (page 135), Hans, under similar conditions was +successful in only one-third of the tests. In his errors he was also +wider of the mark than were the human observers (page 82). The object +perceived, to be sure, is a large one, viz.: the questioner, and he at +close range. We must therefore consider more specifically what are the +determining factors that make for success or failure of the response. +First of all, the innocent questioner very often did not designate the +direction with sufficient clearness. Furthermore, Hans presumably was +not able to discriminate sufficiently between the direction of the +experimenter's eye and that of his head, which two directions did not +always coincide. Finally the horse's attention was often diverted, while +he was running toward the piece indicated, by the other pieces lying to +the right and to the left, and for this reason the addition of a single +piece to the otherwise unchanged row of five pieces tended to decrease +greatly the chances of success. + +The case is different with the perception of the directive signs for +tapping, for nodding and shaking the head, etc., all of which require +the perception of movements. This is not necessarily more difficult on +account of the imperfect constitution of the tissues that serve for the +refraction of light. Some authors even aver that this facilitates the +perception of moving objects. This view was first advanced by the +excellent ophthalmologist, R. Berlin[39] of Stuttgart. In arriving at +this view he was guided by the following considerations. The peculiar +form of astigmatism of the lens of the horse's eye, which Berlin has +described as "butzenscheibenfoermig",[Y] because it appears in the form +of a series of glossy concentric circles around the lens nucleus, has +the property of enlarging the pathway (and with it the rapidity) of +moving retinal images. If we take a speculum by means of which a view +may be had of the interior of the eye, and fixate a definite point on +the retina of the horse, and then make a slight movement of the head +horizontally, we find that the point fixated moves--apparently at +least--toward the border of the pupil. In a normally constructed eye +this seeming movement will be in a straight line, while in the eye of +the horse, (according to Berlin), its path is curved, and therefore +longer. Berlin believes that the same thing which here occurs in the +case of this merely apparent movement, must also happen when an external +moving object is imaged on the horse's retina. Its pathway, too, will be +curved, and therefore longer, so that if the head of Mr. von Osten moves +past the animal's eye, then the image on the horse's retina will take a +longer, more circuitous route than it would if the eye were not +astigmatic. We cannot, however, immediately conclude from the fact that +an objective movement is imaged as being greater in extent on the +retina, that it will therefore be more readily perceived by much less +that it will appear greater to, the horse, than would be the case if the +lens were normally constructed. The visual percept is not immediately +dependent upon the retinal processes, for between the two are +interpolated complex, inaccessible nervous processes. Still, Berlin +believes that he is justified in drawing this conclusion from a number +of relevant considerations. Accepting it, he believes that it would be +possible for the horse to perceive movements, that for the human eye, +which is not subject to this form of astigmatism, would lie below the +threshold. + + [Footnote Y: "Butzenscheiben" are the small circular panes of green + glass, used in leaded windows in early days. They are high in the + middle (hence the name: "Butze," a protuberance) with a number of + concentric circles around the central elevation.--Translator.] + +This theory, the simplicity of which certainly must make a strong +appeal, has been adopted by a number of well-known investigators +(Schleich[40], Koenigshoefer[41]). If we also could accept it, then Hans's +phenomenal power of perceiving the movements of objects would be +explained. But doubts arise which restrain us. Even if we were to accept +Berlin's view in general, we should still come upon the following +difficulties. In the first place, it is questionable whether the +peculiar form of astigmatism mentioned is indeed as common as he +supposes.[Z] The references in the literature are exceedingly meager on +this point. In order to make a few tests at least, I undertook to +examine nine horses with the aid of Dr. R. Simon, oculist, to whom I am +greatly beholden for the assistance given in these and other tests to be +mentioned presently. In not one of the nine cases did we discover +anything like the curved deflection which is supposed to be the sign of +the form of astigmatism in question. But in order to test objectively +whether Berlin's assumption were justified, we examined in the +laboratory fresh specimens taken from two horses. The eyes were fastened +in a frame in what corresponded to their normal position. Their +posterior spherical wall (i. e., their respective retinal surface) was +replaced by a piece of ground glass. On a spherical surface linear +movements of a point of light are always imaged as curves, no matter +what the shape of the lens forming the image may be. (For a more +detailed statement see page 170, at close of note.) Since, however, our +investigation had to do only with those curves which were due to the +qualities peculiar to the lens, we had to replace the spherical by a +plane projection surface. In front of the eye thus modified a strong +light was placed at such a distance that the image of it, produced on +the improvised back of the eye by the cornea and the lens, was a sharply +defined point of light. Now, when the source of light was moved, the +point of light would also move on the glass plate. Sitting at some +distance behind the eye, we observed the movements of this point through +a telescope. Thus we became witnesses of what happens upon the horse's +retina when a moving object passes in front of his eye. Although we saw +the point of light move through relatively long distances both +horizontally and vertically, no sort of deflection in its pathway could +be noted. Berlin's exposition does not hold true for the eyes of the +horses, either living or dead, which were examined by us. + + [Footnote Z: Since no opportunity was given us to examine Hans's + eyes we do not know what their condition is in this respect. Though + it would have been interesting to know, it would hardly make any + difference in the views presented. If Hans should prove to be either + far or near-sighted, then, if we are to make any supposition at all, + it would be that the defect could not be very great, since near + sightedness exceeding 2 or 3 diopters and far-sightedness exceeding + one diopter is seldom found in the case of the horse. According to + Mr. von Osten, Hans at one time manifested a tendency to shy easily. + Be this as it may, for little could be concluded from it, since in + many extremely shy horses, no kind of visual imperfection can be + discovered.] + +But in the case of some of the horses in whom Berlin had seen the +phenomenon for which we sought in vain, he himself tells us, the +deflection was very slight. In that case, it would appear, no great +advantage would be gained along the lines indicated. But even assuming +the degree of deflection to be very great, his theory goes to pieces on +the very point it was supposed to explain. A concrete example will make +this clear. If Mr. von Osten, standing two feet away from the horse, +raised his head 1/5 millimeter (which figure by no means represents the +extreme values that were obtained), then in the horse's retinal image +every point of the man's head would move through a distance of 0.0025 +millimeter--assuming the horse's eye to be free from astigmatism and +assuming its focal distance to be 25.5 millimeters. If, however, other +conditions remaining the same, we presuppose an extreme form of +astigmatism, one in which the path of the retinal image is not a +straight line, but is deflected into a semicircle, then each point would +pass through a distance of nearly 0.004 millimeter. If the sensitive +retinal elements have a diameter of 0.002 millimeter (as Berlin, +somewhat inexactly, states), then from two to four elements would be +stimulated in case there were no astigmatic deflection. But in case the +deflection did take place, it would not necessarily involve more +elements, as can be seen by making a simple graph; indeed we can imagine +cases in which the circuitous path would involve even fewer elements +than the straight one. And finally, when the movement which the horse is +to perceive, does not occur in a straight line but in the form of a +curve, (which will generally be the rule), then the astigmatism will +tend in many cases to decrease the curvature of the image's path on the +retina, and sometimes even obviate it entirely. In all these cases, on +Berlin's own theory, the perception of the movements would be hindered +rather than aided.[AA] + + [Footnote AA: For the benefit of specialists I would say the + following in addition to the more general remarks just made. For the + most part, the determinations of refraction made on the eye of the + horse are still rather unreliable. In sciascopy there is a dispute + among investigators concerning ambiguous shadows, and in the use of + the refraction-ophthalmoscope no definite region of the eye's + background has been adhered to by the various investigators. It + appears that Riegel, whose diligent researches mentioned on page 164 + were published in 1904, knew nothing concerning the round area in + the horse's eye, discovered by I. Zuern[42] in 1902. Also, if so + great a degree of astigmatism is really the rule as is emphasized + especially by Hirschberg[43] and Berlin,[44] then the simple + refractive index usually given--sometimes within a half + diopter--would be meaningless. Berlin[45] and Bayer[46] believe the + vagueness of the retinal image resulting from the astigmatism, is + offset by this: that the oval pupil functions as a stenopaic slit. + In view of the width of the horse's pupil this appears to me to be + rather hypothetical. + + Concerning Berlin's theory of deflecting astigmatism I would say the + following: Of the two ophthalmoscopic signs mentioned as being + characteristic of this form of astigmatism,--the concentric circles + and the arcuate deflection of the pathway of the fixated + points,--when there is a movement of the eye of the observer (or of + the eye observed), according to Berlin the former is not so constant + as the latter. So far as I know, the concentric ring formation is + mentioned only by Bayer[47] and Riegel,[48] and is said to occur + principally in horses with myopic vision--and hence, relatively, in + a minority of cases. Judging from the particulars, we are inclined + to believe that a case of "Butzenscheiben"-lens reported by + Schwendimann[48_a_] is in reality a case of senile sclerosis. + Berlin repeatedly warns us against mistaking the one for the + other.[48_b_] The arcuate deflection, on the other hand, has not + been mentioned elsewhere as a personal observation. In Berlin's + calculation[49] of the increase in the extent of the retinal pathway + an ambiguity has crept in. He says that "in the astigmatic eye there + are stimulated 207 times as many nervous elements as would be + stimulated in the ideally normal eye." It ought to read "207 more" + instead of "207 times as many." And this number holds only for the + one case computed by Berlin, and under the specific assumption that + exactly [Greek: pi]/2 times the normal number of elements were + stimulated (571 instead of 364). Therefore the general statement + which Bayer[50] makes in his text-book, that according to Berlin's + evaluation "207 times more nervous elements" are stimulated in the + astigmatic eye than in the non-astigmatic one, does not hold true. + + Closing this note, a few remarks concerning the experiments made by + Dr. Simon and myself. All of the nine horses were tested for the + vertical image by means of the ophthalmoscope. In most cases Wolff's + electric speculum was used. Atropine was not employed.--For the + laboratory tests the adipose and the muscular tissues were removed + from the eye-ball and the rear part of the bulb cut away. The front + part, containing the cornea and the lens, was fastened over one + opening of a metal cylinder which was closed at the other end by + means of a disc of ground glass. The whole, approximately as long as + a horse's eye, was filled with a normal salt solution whose + refractive index (1.336) corresponds quite closely with that of the + vitreous humor of the horse's eye. The pressure from within was + regulated so that on the one hand it was not dimmed and yet on the + other there were no wrinkles in the cornea. The source of light--the + filament of a Nernst lamp--was moved about in a plane 120 cm. + distant from the eye and perpendicular to the optic axis. It was + moved through the point of intersection as well as at various + distances from it. Movement in horizontal and vertical directions + was in each case along lines 150 centimeters in length, which would + correspond to an angle of vision of not less than 64 deg.. The pathway + of the imaged point was controlled by means of the cross-hairs of + the telescope. If in the same way we observe through the sclerotic + of an intact eye-bulb a point of light falling upon the retina and + shining through the sclerotic and choroid (which is not difficult + when we use an intense light), then to the observer its pathway + will, of course, appear to be deflected convexly toward the + periphery,--and the deflection will appear the greater, the farther + the point of light is removed from the optic axis.] + +But to come now to the most pertinent objection. We saw that Berlin's +whole train of thought rested upon the assertion that it made no +difference whether we regarded by means of the speculum the seeming +movement of a fixed retinal point, or whether the image of an external +moving object is passing over the horse's retina. As a matter of fact, +however, these two processes are very different from one another. In +moving the mirror, with its small opening we are looking through ever +changing portions of the horse's lens,--testing it out, as it were. The +horse, on the other hand, sees with all parts of the lens +simultaneously, in so far as the lens is not covered by the iris. The +arcuate deflection, which is nothing but a registration of the +difference in the indices of refraction of the different parts of the +lens used consecutively, might thus be formed for the observer using the +mirror, but never for the horse. For these reasons we cannot conclude +that the kind of astigmatism described can really increase the horse's +acuity in the perception of movements. + +Since the light-refracting apparatus of the horse's eye does not offer a +satisfactory explanation for the extraordinary keenness of visual +perception possessed by the Osten horse, we must go a step further and +ask whether it may not perhaps be found in the part immediately +sensitive to light, the retina. That portion really would seem to be +adapted to the perception of movements of minimal extent, and for this +reason: it is more than three times as great in extent as the human +retina, and the horse's retinal images are likewise larger owing to the +position of the nodal point. The cells of the retina that are sensitive +to light, the rods and cones, might therefore be correspondingly larger +than those of the human eye, without thereby making the whole organ less +efficient than the human eye. But the most recent measurements[51] have +shown that the rods and cones of the horse's eye are more minute than +ours. Assuming that, in the case of the horse, as is presumably the case +in human vision, the transition of a stimulus from one retinal cell to +the next already in itself induces a sensation of movement, then the +horse ought indeed be extraordinarily keen in the perception of moving +objects (provided that the horse's more minute cells are packed just as +closely as in the human retina). And besides, there are two specially +adapted areas within the retina of the horse. The "band" +("streifenfoermige Area") which was discovered fifteen years ago by +Chievitz,[52] is a strip of 1 to 1-1/2 millimeters in width, traversing +the entire retina horizontally, and is noteworthy on account of its +structure and probably, too, on account of its greater efficiency. It +may have something to do with the accomplishments of the Osten horse; +but in how far it would be hard to say. The other noteworthy portion of +the horse's retina is the "round area" discovered some four years ago, +located at the rear outer end of the "band", and it is the best-equipped +part of the horse's retina and corresponds to the area of clearest +vision, the yellow spot, in the human eye. But this round area need not +come in for consideration by us, for its location would indicate that it +is used in binocular vision, that is, seeing with both eyes.[53] But in +all our experiments the Osten horse observed only with one eye. That +does not mean, however, that under other circumstances the round area +may not be of very great importance. + +In the present state of our knowledge, all attempts at explanation are, +of course, of the nature of hypotheses. If further investigations should +disclose this explanation to be untenable, then we would either have to +suppose some unknown power in the eye of the horse,[AB] or else seek a +cause in the animal's brain. Further experiments on other horses would +be necessary in order to discover whether the species as a whole +possesses this ability or whether only certain ones are thus endowed. +The former is of course more probable. In this particular case +conditions were unusually favorable for the development of this +ability. We must bear in mind that in all probability Mr. von Osten's +movements very gradually became as minute as they are now, and that +therefore Hans at first learned to react to such as were relatively +coarse. Furthermore, his practice extended throughout four years and +during this time it was his sole occupation. Without specific +predisposition, however, all this practice would have been utterly +futile. We can also readily appreciate how indispensable in the struggle +for existence a well-developed power of perceiving moving objects must +be to horses (and most other animals) living in their natural condition +and habitat, in order to be aware of the approach of enemies, or, in the +case of carnivora, the presence of prey. In view of all these +considerations we can readily see how it was possible that the horse, +perhaps in spite of rather defective vision, could react with precision +to movement-stimuli which escaped observation by human eyes. + + [Footnote AB: Koenigshoefer, who as we have already said, seconds the + explanation given by the ophthalmologist Berlin (and who confounds + "Butzenscheiben" astigmatism with the common, so-called regular + form), believes[54] that not only astigmatism but also the shape of + the blind-spot of the eye must be taken into consideration. This + portion of the retina, where the fibres of the optic nerve enter the + eye (and called "blind-spot" because there are no cells there that + are sensitive to light) is very nearly circular in man, but differs + in shape in the different species of animals. Koenigshoefer thought he + had discovered that a relatively elongated blind spot was favorable + to keenness of vision. If we place the mammalia in series on the + basis of their relative keenness of vision, he says, we would find + that this series is identical with the one in which they are grouped + with reference to the form of the blind-spot from the circular up to + the most elongated. (In such a series the marmot takes the place of + honor.) + + This exposition is not very satisfactory, however. We cannot be sure + what he means by "keenness of vision" ("scharfaeugigkeit"). Is it + visual acuity in the usual sense of the term (as is said in one of + his passages), or keenness in the perception of the movements of + objects, (this would appear to be his real meaning), or both at the + same time. But whatever the significance he may put into the term, + any such attempt at grouping the lower forms must prove + unsatisfactory from the very start on account of the scant data + which we possess on visual perception in animals. The experiences of + the hunt upon which Koenigshoefer partly bases his view, are entirely + inadequate for such a purpose. This much is certain, that the Osten + horse, in spite of a blind-spot which, though somewhat oval, is by + no means very elongated, possesses an extraordinary acuity in the + perception of movements. Even if the parallelism mentioned by + Koenigshoefer were really shown to exist, it would not explain the + matter until it were also shown in what way keenness of vision is + dependent upon the shape of the blind-spot,--a portion of the eye + which is not immediately operative in the visual sensation at all.] + +We can understand also the horse's never-flagging attentiveness when we +recall that self-preservation prompts eternal vigilance over against all +that is going on in the animal's environment. (In the case of Hans, +hunger was at first the motive; later, habit did the work.) Furthermore, +the lower form is not hindered in giving itself over to its +sense-impressions by the play of abstract thought which tends so +strongly to direct inward our psychic energy,--at least, in the case of +the cultured. + +Nevertheless, Hans still remains a phenomenon not only in excelling all +his critics in the power of observation, but also in that he is the +first of his species, in fact the first animal, in which this +extraordinary perceptual power has been proven experimentally to be +present. It has long been known[55] that horses could be trained to +respond to cues in the form of slight movements, which remained +unnoticed by the layman, and this fact has been made use of by circus +trainers to its fullest extent. But such signs, I have discovered, are +without exception, of a far coarser sort than those we have here +described, and they can be instantly detected by the practised observer. +Nor was it known to professional trainers that it was possible for the +master to direct a horse to any point of the compass simply by means of +the quiet posture of the body. For this reason it was believed that no +signs could possibly be involved in the color-selecting-tests (cf. +Supplement III, page 255). In this we have the support of some of our +experts, as is witnessed by the following extract from a letter of his +Excellency Count G. Lehndorff, one of our best hippological authorities, +who at one time carefully examined the Osten horse. (The letter was +addressed to Mr. Schillings, and I have permission of both gentlemen to +use it). In it he says: "If the author's statements, in which you also +have concurred, are correct, and if, as a matter of fact, the horse +really does react to such minute movements as are absolutely +imperceptible to the human observer, then we have indeed something quite +new, for hitherto no one would have believed that horses can perceive +movements which man cannot. But I am even more surprised by the +explanation of the color-selecting feats.--This too, is something +absolutely new. One would not have deemed it possible that a horse could +do anything of the kind simply by using the posture of a man's body as a +cue to which it could react with such precision." + +And yet, even though both facts were new concerning the horse and had +not hitherto been proven experimentally regarding any other species, +nevertheless something of this sort has been known concerning the dog +for some time. His ability to single out an object upon which his master +had intently fixed his gaze, was made the basis of a special form of +training, called "eye-training,"[56] nearly one hundred years ago. The +dog was taught to focus constantly upon his master's eyes and then upon +command to select the object which he, the master, had been fixating. +Such a dog has been described by the naturalists A. and K. Mueller.[57] +But the master of the dog, unlike Mr. von Osten, would not permit anyone +else to work with the animal, and the two brothers, recognizing the +trick, were justified in adding that "the whole affair aimed at +deceiving the public, and the dog's reputation was but a means of making +money". The success of such exhibitions appeared furthermore, to depend +upon the close proximity of the trainer and the dog, whereas the +direction of the head (and even of the body) could very probably be +perceived at greater distances also. At least we learn from a reputable +source that in the hunt, dogs can perceive from the mere posture of +their master, what direction he intends to take.[58] + +But a still more curious fact is this, that dogs, too, learn--evidently +spontaneously--to react to the minimal involuntary expressive movements +of their master. The first example mentioned in the literature on the +subject is that of an English bull-dog called Kepler, belonging to the +English astrophysicist, Sir William Huggins.[59] We are told that this +dog seemingly could solve the most difficult problems, such as +extracting square roots and the like. The numbers were indicated by +barking,--thus one bark was for one, two barks for two, etc. Every +correct solution was rewarded with a piece of cake. Huggins states +explicitly that he gave no signals voluntarily, but that he was +convinced that the dog could see from the questioner's face, when he +must cease barking, for he would never for an instant divert his gaze +during the process. Huggins was unable, however, to discover the nature +of the effective signs. This satisfactory, though still unproven, +explanation has been accepted by specialists, among them Sir John +Lubbock.[60] I, too, regard this dog as a predecessor of our Hans. + +A similar case is reported by Mr. Hugo Kretschmer, a writer of Breslau, +in the "Schlesische Zeitung" of August 21, 1904. To him I am beholden +for a detailed written statement, which he has kindly permitted me to +use in this connection. The gentleman named, first trained his dog to +ring the table-bell, and this, by pressing the dog's paw upon the +bell-button. When the dog had learned to do this independently, his +master tried to teach him the rudiments of numbers, in such a way that +the animal was to give one ring of the bell for the number 1, two for 2, +etc. But these attempts failed utterly and had to be abandoned. But Mr. +Kretschmer had noticed that he was able to get the dog to ring any +number which he, Mr. Kretchmer, might decide upon. (Success was always +rewarded by a bit of bread and butter.) At first Mr. Kretschmer tried to +imagine vividly only the final number, but failed thereby to elicit +correct responses from the dog. But he did succeed when he tried making +a series of separate volitions. Thus for the number 5, he would "will" +each separate push of the button on the part of the dog. Even so, +however, he never got beyond 9, for then the dog would become impatient +and would ring the bell continuously. Anything that diverted the dog's +attention, such as noises, etc., also entailed failure. In these tests +master and dog had faced each other, each gazing steadfastly at the +other. Mr. Kretchmer was convinced, however, that the dog was not guided +by any sort of sign, but rather by suggestion. He based his belief on +the following two observations. After some practice, he says, the tests +were also successful when he did not look at the dog, but stood back to +back with it, or when he screened himself from the dog's view by +stepping to one side behind a curtain. The tests were unsuccessful, on +the other hand, whenever he was mentally fatigued or had taken some +alcoholic drink. The arguments do not appear to me to be adequate. If he +turned his back upon the dog and no other observer was present, he had +no means of knowing whether the dog did not, after all, peer around to +get a peep at him. If others who knew the desired number, were present, +the dog might have gotten his cues from them. And there may be some +doubt whether the curtain adequately served the purpose for which it was +intended. At any rate, it was added that all attempts to influence the +dog from an adjoining room--which would thus exclude effectively all +visual signs--were utter failures. I am also strengthened rather than +weakened in my belief, by the second argument which Mr. Kretschmer +makes, viz.: that mental fatigue or the use of alcohol on the part of +the questioner tends to make the result unsatisfactory. We noted a +similar effect in the case of the horse (page 150), where a disturbance +of the "rapport" between the questioner and the horse was invoked by +some by way of explanation. The facts were explained by us much more +simply. We attributed the result to the close correlation between the +type of mental concentration and the nature of the expressive +movements--a correlation which we have shown experimentally to exist. I +cannot, therefore, subscribe to the view that this dog did not require +either visual or other sensory signs. The tests which were made for the +purpose of strengthening that view, are on a par, I believe, with those +mentioned on page 45. And since auditory, olfactory, and other stimuli, +though not impossible, still are improbable, I believe that our Hans, +Huggins's dog, and the one belonging to Mr. Kretschmer, differ from one +another only in this, that the first taps, the second barks, and the +third presses a bell-button. + +And finally I have access to a letter from the Rhine Province in which +there is a brief account of a dog that would promptly obey any command +that was given without a sound and supposedly without the accompaniment +of the slightest kind of gesture. It is specially mentioned that the +animal steadily watched its master during these tests. The perception of +the slightest involuntary expressive movements is in all probability the +secret in this case also. Here, too, suggestion has been invoked by way +of explanation, but there was not the slightest attempt made to find for +it a more specific foundation, and we cannot suppress an objection based +on the matter of principle. It is incumbent upon anyone who uses a term +so ambiguous, to define what content he desires to have put into it. If +he does not do this, he is giving us, instead of a concept, a bare word, +instead of bread, a stone. + +While we must reject the explanation based on suggestion,[AC] we +believe, on the other hand, that we have here again, evidence of the +presence of visual signs, given unwittingly and involuntarily, just as I +am sure that they were involved in the two preceding cases, and +similarly in the case of the Huggins dog. Since the effective signs were +discoverable in none of these canine predecessors of Hans, an +investigation would be desirable, based upon the insight gained as a +result of these experiments upon Mr. von Osten's horse. Unfortunately +this is impossible, since the dogs in question are dead. But others like +them undoubtedly exist in many places. We might mention that when Hans +first came under the limelight of public attention, there was also +frequent reference to the Huggins dog, but he soon dropped out of the +discussion again.[63] And this for two reasons. The dog never took his +gaze from his master and appeared to be entirely dependent upon him in +his reactions. Hans, on the other hand, seemed to give evidence of a +high degree of independence and never appeared to look at the +questioner. But we know now that, though he was never dependent upon the +will of his master, he, too, abjectly hung upon the man's involuntary +movements and never for a moment lost him from view. But since the horse +is able to observe with one eye alone, and needed to direct only it and +not the entire head toward the questioner, in order to focus +comfortably, one could not conclude as to his line of vision from the +direction of the head. Since, furthermore, in the horse the pupil is +hardly distinguishable from the darkly pigmented iris and since the +white sclerotic is hidden by the eyelids, except when the eye is turned +very much, it is difficult to determine what direction the eye is +taking. I once purposely stepped backward to the horse's flank, so that +he had to turn his eye far back and thus the outer border of the iris +and the white sclerotic coat became visible and all doubt concerning the +line of vision was removed. This doubt could never arise in the case of +the dog, the median plane of whose head is always directed toward the +object fixated, and Zborzill is justified in saying, as he does, in his +discussion of training of the kind mentioned on page 177, "But any +careful observer can immediately guess the manner in which such a dog +has been trained."[64] If Hans had chanced to possess so-called +"glass-eyes"--in which the dark pigment is wholly or partly lacking, so +that the black pupil is clearly defined against the lighter +background,--then no doubt could ever have arisen concerning the +direction of the eye, and Hans never would have come to be regarded as +the "clever" Hans. + + [Footnote AC: I can find examples of supposed suggestion in the case + of animals given only by Rouhet.[61] He says that by means of + suggestion he taught a half-year old half-blooded mare-colt which he + had raised himself, to fetch and carry, and this in a very short + time. In order to indicate to the colt what was wanted, Rouhet would + concentrate with his whole mind upon the object intended (a watch), + and at the same time he would bend forward slightly. In the third + test, that is at the end of fifteen minutes, he had accomplished his + purpose, and in the tenth lesson, no more mistakes occurred. The + colt would fail to respond, however, as soon as he refrained from + making any gestures, or was in a laissez faire frame of mind, or + when he thought of other things. He therefore believes that there + must have been some kind of immediate, though inexplicable, + connection between the brain of the trainer and that of the horse. I + think the explanation is evident: the connection was not as he + thought, an immediate one, but arising through the mediation of the + man's attitude ("attitude un peu baissee"), and of his movements + ("gestes"), both resulting from his intense concentration ("tension + de la pensee"). + + In general we may say that, no matter what content we may wish to + put into the term "suggestion," not a single fact has since come to + light which would justify, and much less demand, the application of + the term to lower forms, unless we would expand the definition of + the term to the extent of comprising every kind of command, every + arousal of ideas, whatsoever. But it would then be nothing but a new + name for old knowledge[62] and would lose all explanatory value. + (Hypnotism, so-called, in the case of horses, I shall discuss + elsewhere in another connection.)] + +After the publication of the December report, Hans acquired a reputation +for excellence in thought-reading and thus the discussion of +thought-reading among animals in general became once more the order of +the day. That is to say that many of our domestic animals are--like the +human mind-reader (a la Cumberland),--supposed to have the ability to +infer the thoughts of their masters from slight, involuntary movements. +They are thus aware when the feeding hour approaches, when they may go +out in the open, etc. They also appear to be aware that their welfare +lies in our hands, and therefore would seem to have a vital interest in +divining our intentions and our wishes. Not only our spoken words, but +also numberless movements--usually without our knowing it and often +contrary to our desire--speak a clear language. As is well said by the +American neuropathologist, Beard,[65] (who first explained the +phenomenon of thought-reading, on the basis of the perception of very +minute muscular jerks, and therefore called it "muscle-reading" or +"body-reading"): "Every horse that is good for anything is a +muscle-reader; he reads the mind of his driver through the pressure on +the bit,--though not a word of command is uttered." We know that in the +case of perfectly trained horses the rider's mere thought of the +movement which he expects the horse to make, is seemingly sufficient to +cause the animal to execute it.[AD] Such cases are of course very much +like that of our Hans, excepting that instead of visual signs they +involve aids of a mechanical nature, which, however, does not alter the +general principle, since both of them are of the nature of sensory +stimulation. But we must not overlook the essential difference between +this so-called thought-reading on the part of animals and that which is +done by man. The human thought-reader can interpret movements, for he is +familiar with the ideas which are their source. Thus when at the second +tap, I notice a very slight jerk of the subject's head, and a stronger +one at the fifth tap, I infer that he thought of the problem 2+3=5. +While the experimenter thus cannot be said to read thoughts, he still +infers them. The animal, on the other hand, we may be reasonably sure, +draws no such inferences. In its conscious life it remains ever on the +sensory level. If we could ask Hans about it, he would probably answer: +"As soon as my master stoops forward, I begin to tap; as soon as he +moves, I stop. The thing which induces me to act thus is the carrot +which is given me; what it is that induces my master to make his +movements, I do not know."--It is therefore erroneous to believe that +animals require the power of abstract thinking in order to utilize the +signs which are consciously or unconsciously given them, as is argued by +Goldbeck[68] when he says with reference to the training for visual +signs, which we have already mentioned before: "There the dog has +consciously interpreted the visual impression in terms of the conclusion +that he is expected to bring forth the leaf indicated." Nor was there +any justification for the critic who thought he could put the essence of +the report of December, given in Supplement IV, into the following +words: "He (Hans) showed that he has the power of attention, can draw +logical conclusions, and can communicate the result of his +thinking,--and all this independently." Yet none of this had been +asserted. The whole thing may be explained satisfactorily by means of a +process of simple association established between the signs observed in +the master and certain reactions on the part of the horse. The fact that +the movements made were so exquisitely minute does not change the matter +in the least. Such signs call for a high degree of sensory keenness and +great concentration of attention, but by no means an "extremely high +intelligence." + + [Footnote AD: An illustration is given by Babinet[66] concerning the + horse of an English lord. Mr. Burkhardt-Foottit, also, that + excellent trainer, who has been master for more than forty of the + most highly-trained horses, tells us that while sitting on a + well-managed horse it sometimes happened that he had merely thought + of making a certain turn, when the horse immediately executed it, + before he, the rider, had to his knowledge given any sign or aid. An + observation belonging under this head is also made in Tolstoi's + "Anna Karenina"[67], this perfect mine of acute psychological + observation. In the famous description of the race we are told + concerning Count Wronskij riding his Frou-Frou just behind Machotin + mounted upon Gladiator, who was leading the race: "At the very + moment when Wronskij thought that it was time to overtake Machotin, + Frou-Frou, divining her master's thought, increased her pace + considerably and this without any incitement on his part. She began + to come nearer to Gladiator from the more favorable, the near side. + But Machotin would not give it up. Wronskij was just considering + that he might get past by making the larger circuit on the off-side, + when Frou-Frou was already changing direction and began to pass + Gladiator on that side." Similar experiences might be gathered + elsewhere. Not infrequently the reflection of the rider that his + horse had not for a long time indulged in some trick peculiar to + him, will immediately call it forth; or doubts on the part of the + rider concerning the possibility of crossing some barrier, are often + the cause of the horse's fall or of his refusal to leap and of his + running away.] + +Let us turn now from the consideration of visual perception to that of +auditory perception in the horse. We saw that the fact that Hans was +able to respond to commands which were only inwardly enunciated, that +is, commands which were merely thought of but not spoken, was not proof +of great acuity of hearing, but rather that hearing was not at all +involved. If Hans had been deaf he would, none the less, have promptly +obeyed the commands. Blind and near-sighted horses try to overcome their +deficiency by means of the sense of hearing, and hence show a pronounced +play of ears. In the case of the Osten horse, however, attention has +been diverted from auditory stimuli in the process of habituation to +visual signs, and as a result ear-movements are almost completely +wanting. One is not of course permitted to deny _a priori_ that perhaps +some associations might have been formed between objects and the vocal +signs belonging to them, e. g., between the colored cloths and the names +of the colors if both had been presented together oftener than was the +case. + +But there is a dearth of reliable observation as to how far auditory +associations of this sort may be established in horses. Usually the +following is cited. Horses learn to start off, to stop, and to turn +about in response to calls. They are able to distinguish properly +between the expressions "right" and "left", or equivalent terms. Upon +command they will start to walk, to trot or to run. And they also know +the name by which they are usually called. All authors agree that +cavalry horses understand the common military commands; one writer even +avers that they excel the recruits in this respect.[69] Some believe +that in riding schools the horses pay closer heed to the calls of the +riding-master than to the control of unpractised riders, even when the +two are at variance with one another.[70] My experience with the Osten +horse and a number of other pertinent observations aroused in me the +suspicion that much that is called or spoken in the process of managing +a horse may possibly be just so much labor lost. In consequence I made a +series of relevant experiments. I have thus far tested twenty-five +horses of different kinds, from the imported Arabian and English +full-blood, down to the heavy draft-horse. The experiments were made +partly in the courtyard of military barracks, partly in the circus, and +partly in a riding-school or in private stalls. I am specially indebted +for kind assistance to Messrs. von Lucanus, Busch, and to H. H. +Burkhardt-Foottit and E. Schumann, the two excellent trainers connected +with the Busch Circus. During these tests, the horses were always amid +circumstances familiar to them, whether free or bridled, under a rider +or hitched to a wagon. All aids or signals, except the calls, were +eliminated in so far as it was possible. + +The results of those tests were in substance as follows: Many horses +react to a smack of the lips by a rather fast trot. Many stop on the cry +"Hola" or "Brr". This last was nicely illustrated in the case of two +carriage horses supplied with large blinders and held with a loose rein, +and hitched to a landau. One of them regularly stopped when the "brr" +was given by the driver, whereas the other, which had not been +habituated to this signal, kept serenely on the trot, so that the +vehicle regularly veered off the track--a sure sign that no +unintentional aid was being given by means of the reins. Other horses, +again, were accustomed to halt in response to a long-drawn-out "hola", +but it was the cadence of melody rather than the word that was +effective, since any other word, or even a series of inarticulate +sounds, would produce the same result, provided they were given with the +proper inflection. When this was changed, then the response would fail. + +The result was not so apparent when it came to controlling the kinds of +gait. One riding-school horse, when lunged and in a gallop, could be +induced by a friendly call--the word again was a matter of +inconsequence--to slacken his pace into a trot and from a trot into a +walk. But this reaction was by no means very precise. Another, a +full-blood, contrary to the trainer's expectation and to his great +astonishment, failed to respond to any kind of spoken command as soon as +the one who carried the reins refrained from making any movements which +might indicate what was wanted. (To refrain from all expressive +movements of this kind is by no means an easy matter). The slightest +move, apart from any help by means of the reins or the whip-handle, was +sufficient to evoke a response. The results in the case of the military +horses, differed in many particulars. Thanks to the courtesy of Captain +von Lucanus I had the opportunity of testing three cavalry horses, two +geldings and one mare, aged nine, thirteen, and nineteen years +respectively, and all of them in the regiment ever since their fourth +year. They had been selected as the "most intelligent" in the squadron, +and we were assured that they would obey punctiliously all the usual +commands. They were ranged behind one another, with the customary +distance of two horses' lengths between, and were ridden each by his +accustomed rider. Both starting and stopping upon command were tested. +The horses were held by the reins, but the riders were cautioned to +refrain from giving any aid that might cause the horse to start when +starting was to be tested, or that might restrain him when stopping in +response to the spoken command was to be tested. If a suspicion arose--a +thing which happened only twice, however--that a rider had actively +aided in his horse's reaction, then an officer would mount into the +saddle. If it appeared that one of the horses was simply imitating the +others, then the others were purposely restrained by their respective +riders. The commands were given by the corporal who usually had charge +of the horses. In a few cases the sergeant of the squadron gave the +commands, but this made no difference in the success of the experiment. +Now as to the results. Whenever the horses were trotting or walking, all +commands, without exception, were in vain. They effected neither an +increase nor a decrease in the pace. A result was obtained only when the +horses were standing when the test began; and this result was simple +enough,--upon certain calls the animals would respond by beginning to +walk. This was the only reaction that was obtained. The most effective +of the commands appeared to be "Squadron,--march!" But the command +"Squadron!" or "March!" alone, were quite as effective; yet none of +these commands was obeyed without exception. Reactions were occasionally +obtained in response to "trot!", "gallop!" "retreat!", (the usual +introductory "squadron" was purposely omitted here, because it alone +sufficed to start the horses). But the reactions were always the same, +viz., to start on a walk. Another series of commands (such as those +which are addressed to the rider alone, e. g., "Lances down!") had no +effect whatever; a certain amount of selection therefore did seem to +take place. In all these tests the order of the horses with reference to +each other's position was repeatedly changed. One of the horses, the +youngest, and reputed to be the most "intelligent", (he was as a matter +of fact the most spirited), gave evidence of a gregarious instinct, +intensified by habit, which, if it had been overlooked, might have +become a source of serious error. Not being accustomed to go at the +head, when so placed it started properly in only 18% of all such cases. +When, however, (other conditions remaining the same,) he was put in +second or third place, he started properly in 67% of the tests, and if +we take into account only those cases in which the three most effective +commands were used ("Squadron!", "March!", and "Squadron--march!") he +reacted correctly in 91% of the cases. (The number of tests was 17, 36 +and 22 respectively for the three groups mentioned.) The horse, +therefore, almost always began to step properly when he stood behind one +of his companions, but seldom when he stood at the head. And when he +stood at the head and began to walk at the proper moment, it was plain +that it was a case of imitation and not initiative, for the horse was +still able to see the others, owing to the extent of his field of vision +backward, and he was always the last to move, whereas otherwise he was +always the first to move, and always difficult to restrain. So when the +horses to the rear were restrained or when the intervening distance of +two horses' lengths was lessened, so that this gelding could not see the +one in the rear, he failed completely to respond. Accordingly these +three horses did little to justify the faith which their squadron had +placed in them. + +Now a few words on the manner in which horses react upon the call of +their names. We are not concerned with those that are seldom or never +called by name (such as those in the cavalry). I have not discovered one +horse that constantly and unequivocally reacted upon the mention of its +name (though I would not assert that there are none that would do so.) I +was nearly always able to convince the owners or grooms, who at first +had maintained a contrary opinion, that any inarticulate sound was +capable of producing the same effect as the calling of the name. What +the significance of inflection may be, I am not at all certain. When a +certain one of a number of horses standing in the same stable was +called, all of them responded by pricking their ears, raising their +heads, or else turning about. For this reason the reaction of the horse +specifically called lost all significance. Likewise the call which is +ordinarily used in lunging when the man in the center of the circle +wishes the horse to change its gait, or to advance toward him, also +proved ineffectual as soon as the man inhibited every sort of movement. +A slight nod, on the other hand, was always effective. Several times I +have tried to call horses to me, when they were free and running about +in the arena, but was unsuccessful. After I had given them some sugar, +however, they would always come to me--whether I had called or not--and +would then refuse to leave my side. But this is a matter of common +observation. + +I would, however, regard all of these tests as merely provisional. In +spite of the greatest effort, it was not always possible to control all +the conditions of the experiment, and furthermore, the number of tests +would have to be materially increased in order to yield an appreciation +of the difference due to race, age, and the individual variation and +training of horses. But we may, even now, be sure of one thing. Over +against the certainty with which horses react to visual stimuli (in the +form of movements perceived), it does not appear that the formation of +auditory associations is greatly favored by nature in these +animals,--indeed, auditory associations are far less common than is +generally supposed.[AE] Horses compare very unfavorably with dogs in +this respect. The latter easily learn to react with a high degree of +precision to auditory signs,--as I learned from a series of experiments +which I was enabled to perform. The Osten horse, therefore, does not +stand alone among his kind in his inferior auditory equipment, as one +might be tempted to believe at first blush. + + [Footnote AE: All the authors who have given practical suggestions + for the training of horses, whether free or with lunging reins, have + great faith in the efficacy of calls, but usually recommend a + mingling of calls and movements in the way of signs, (thus + Loiset,[71] Baucher,[72] von Arnim[73]). It therefore cannot be + stated just in how far the calls really effect anything. In other + cases I am inclined to doubt outright the influence which is + ascribed to the auditory signs. Meehan[74] gives an account of a + horse that was exhibited in London in the early 90's of the last + century. Pawing with his hoof, this horse apparently was able to + count and answer questions in arithmetic, and among other + accomplishments he was supposed also to be able to understand + something of language. In reality, however, he merely responded to + cues which were disclosed to the reporter by the trainer. In pawing, + the horse was guided by movements of the trainer, and in nodding or + shaking the head he reputedly got his cue from the inflections of + the man's voice. Is it not probable that in this latter case it was + the movements which accompanied speech that were alone effective in + inducing the nod or the shake of the head, so that the exhibiter was + deceiving not merely the public, but also himself? Perhaps we may + also doubt the exposition made by the well-known hippologist, + Colonel Spohr.[75] He tells us that it is easy to train horses to + raise the left foot or the right foot in response to the commands + "Left--foot!" or "Right--foot!" and that it will be the fore foot + when one is standing in front of the horse, and the hind foot if one + stands near the rear. It cannot be so very difficult, he thinks, + even to get the horse to understand the commands "Left (or + right)--fore foot!" and "Left (or right)--hind foot!"--and all + without any other aids but the spoken words. Should this really be + possible without even the slightest kind of designating + movement?----The following case, again, I believe is undoubtedly + based upon a misinterpretation. Redding[76] relates concerning his + nineteen-year old horse that he himself had owned for thirteen + years, and had always kept in single harness,----that this horse not + only understood the meaning of a long list of words, such as: + bureau, post-office, school, churchyard, apple, grass, etc., but he + also knew a number of persons by name, as well as their places of + residence. If he were told in advance to halt at a certain + residence, he would do it without any further aid from the driver. + For this reason the happy owner felt certain that the animal + possessed a high order of intelligence and "that this horse does + reason." What sources of error were here operative, whether signs + were given by means of reins, or head or arm movements, could be + determined only by a careful examination of the case. + + And finally we would exercise some reserve in entertaining the + suggestions for the acoustic education of horses which have come + from various sources. Colonel Spohr[77] whom we have just been + mentioning, thinks that it would not be a difficult matter to get a + horse to respond with a walk to one smack of the lips, with a trot + to two smacks, and with a galop to three, and then he could be made + to slacken his pace once more into a trot in response to one + long-drawn "Pst!" and to stop in response to two. Others have gone + even further. Decroix,[78] at one time leader in veterinary affairs + in France, conceived the idea of working out a universal language as + regards the commands that are given to horses, in the humane purpose + of sparing them the whip. He called it "Volapuek hippique." For the + commands "go," "right," "left," and "halt," he suggests these: "Hi!" + "Ha!" "He!" and "Ho!" respectively. From these it was possible to + make eight combinations, such as "Hi! Hi!" for "Trot!" "He! He!" for + "Left about" (while the single "He" was to mean "Forward, to the + left!") "Ho! Ho!" for "Back!" etc. Decroix thought that the whole + system could be inculcated in a very few lessons. He even had a + medal struck which was to be awarded to the driver or rider who + should first exhibit a horse, thus instructed, to the Societe + Nationale d'Acclimatation de France (of which Decroix was + president). Eight years have elapsed since then, but we have heard + of no one who has earned the medal mentioned. In the future greater + care will probably be exercised in the putting forth of such + suggestions, and two sources of error may be guarded against, viz.: + involuntary movements on the part of the rider or driver, and + imitation of the horses amongst themselves. (One horse, guarded by + an experienced rider, may serve as copy for ten others with + inexperienced men in the saddle.)] + +It is easy to explain the musical accomplishments. The tones which were +played for the horse, were known to Mr. von Osten, since he himself +played the harmonica, or when someone else played it, he, Mr. von Osten, +could see the stoppers. He then thought of the number which indicated +the tone in question, and Hans would tap it. Thus arose the tale of the +horse's absolute tonal memory. This tale gained much support at the +time, from an experience which has been recounted to me by the +well-known composer, Professor Max Schillings. It shows more clearly +than any other report how very confused were the threads that had been +spun in the whole matter. In order to test the horse's musical ability +Prof. Schillings played, let us say, three tones upon the accustomed +instrument. Complying with Mr. von Osten's wish, Prof. Schillings always +indicated which three he was about to play. The horse always tapped them +correctly. In order to make a decisive test, Prof. Schillings then +played, without anyone's knowledge, a note that was in reality a third +below the one he had indicated to Mr. von Osten. Curiously enough, Hans +tapped, as a matter of fact, the number indicating the note that was +actually struck, and it was only in the third repetition and after many +exhortations on the part of the master "to have a care", that the horse +finally tapped the number indicating the note Mr. von Osten had in mind +and which in truth was the wrong one. This curious experiment seemed to +those to whom Professor Schillings communicated it, to yield conclusive +evidence of the horse's absolute hearing. As a matter of fact, however, +Prof. Schillings had unwittingly, and, contrary to any intention on his +part, inspired the horse. Standing, as he did, just behind the right +shoulder of the horse, he was able to interrupt Hans (who had begun to +tap in response to a move on the part of Mr. von Osten,) by means of an +involuntary movement which did the work of a closing signal. At the same +time Mr. von Osten, likewise standing to the right of the horse and +expecting more taps, remained perfectly quiet. (This is as it was in +the tests, mentioned on page 71, in which, of two experimenters, one +started the horse tapping, and the other stopped him.) Mr. von Osten +very probably lost patience after Hans had seemingly given the wrong +response twice, and thereupon came nearer to the horse and thus by +monopolizing its attention--so as to exclude Prof. Schillings--he was +able to get the response so ardently desired.[AF] When, in tests such as +these, two stoppers were opened and thus two notes sounded, Mr. von +Osten would count the number of stoppers intervening between the two, +and Hans would tap the number. And so arose the tale of Hans's knowledge +of musical intervals. Whenever the two notes were sung or whistled, in +which case there would be no stoppers that could be counted, then Mr. +von Osten, who was quite destitute of musical knowledge, was at a loss, +and also Hans. If, however, the intervening notes were sung, then +everything went smoothly once more. Major and minor chords were +regularly characterized as "beautiful", all others as "bad", (but even +here errors occurred). A musician had taught Mr. von Osten these +distinctions. The old man also knew the melodies that were played on the +hand-organ. Each one had a number assigned to it, and Hans was required +to tap the number of the melody in token of recognition.--Hans was as +ignorant of musical time, as he was of melody, and all attempts to get +him to march in regular step were utterly futile. A number of musical +tests were made in the absence of Mr. von Osten. In these Mr. Hahn +undertook the questioner's role, and since he had had musical training, +he was aware of what the numbers should be, even when he could not see +the stoppers of the harmonica, and, therefore, we readily understand why +it was that the horse responded so wonderfully in his case. + + [Footnote AF: General Noizet[79] has left us a story of the middle + of the last century, which in essential detail corresponds closely + with the one just given. The scene is a French chateau and the hero + is--a rapping table, highly prized on account of the intelligent + answers it could give. Seated about it were a number of ladies and + at the other end of the room sat a French savant, a member of the + Academy. The ladies requested him to put a simple mathematical + question to the table, and complying with their request, he asked + for the cube root of 4. None of the ladies who sat about the table + knew the solution; the table unhesitatingly gave 6 raps. This answer + was refused as incorrect. The table was asked to try again, and + again it wrapped 6. For this it was bitterly reproached. Hereupon + the questioner, who during the whole time had remained in his place + at the other end of the room, came forward with the confession that + the table was innocent, that he had made a mistake. He had asked for + the cube root of 4, but had really meant to ask for the cube of that + number, viz., 64, and the table had as a matter of fact given the + first numeral of that number. + + One is immediately struck by the analogy between this case and that + of Professor Schillings. In both cases those immediately concerned + (the women in the one, Mr. von Osten in the other) believe that a + wrong answer is being given repeatedly. The cause of the error lies + in a person who seemingly is not concerned with the response. (The + Frenchman asked the question, but did not sit at the table. + Professor Schillings sounded the notes, but it was Mr. von Osten who + got the horse to tap.) In both instances the questioner asks one + thing, but had something else in mind. (With the Frenchman it was a + slip of the tongue; Mr. Schillings did it purposely.) And finally, + in both cases the response corresponds not to the question that has + been asked, but to that which has been thought, so that, though + seemingly wrong, the responses of both table and horse were really + correct. By way of explanation, Noizet believes that he has a case + of true thought-transference or "telepathy" (page 108). The + questioner watched with utmost attentiveness the rapping of the + table, and the women in turn regarded the man. And thus, Noizet + believes, the man's thought was transferred to the minds of the + others without the mediation of eye or ear, etc., and hence + unvitiated by the words that had been spoken. I myself prefer + another explanation. At that moment in which the rapping arrived at + the expected number, the Frenchman executed a movement + characteristic of release of tension and to this the women of the + circle reacted. It was not necessary that they should be able to + account for this afterward, (just as sometimes occurs in the case of + thought-readers[80]). It is very probable, too, that they were not + of a very reflective turn of mind anyway. We are warranted, I think, + in regarding the two cases as identical in kind.] + +The so-called musical ability of horses appears, from all that is known, +to be confined within very narrow bounds. Only one fact is universally +accepted, viz., horses of the military are believed to possess a +knowledge of the significance of trumpet signals, and are often said to +interpret them more readily than the recruits.[81] Since no experiments +had been made along these lines, I undertook to make a brief test of the +cavalry horses mentioned on page 188. As in the preceding tests, the +three animals were arranged behind one another with the customary +distance of two horses' lengths between, and each was ridden by his +accustomed rider. They were held by the reins, but received no aid of +any kind, either to start them or to restrain them. A bugle then sounded +the various signals at the other end of the barrack's courtyard. We had +been previously assured that the horses would certainly react without +fail. But, as a matter of fact, the result was quite the contrary. Two +of the horses did not move at all, and the third, a thirteen-year old +gelding, was startled nearly every time and would tear off in a +gallop--even though a trot had been sounded. I would not, however, +venture to draw any conclusions from results such as these. Many more +tests would have to be made, and some of them upon the whole squadron, +before a judgment could be given.[AG] + + [Footnote AG: Professor Fluegel,[82] basing his statements on an + article appearing in "Schorer's Familienblatt" (Berlin, 1890, No. 8, + p. 128), gives an account of similar experiments which were supposed + to have been conducted by the Zoological Society for Westphalia and + Lippe, and presumably showed that "the horses of the military do not + understand the bugle calls." No matter how well trained a horse may + have been, it would not respond to a signal. This report, however, + is due to a mistake. Such experiments have never been made by the + society mentioned, so I am told by its director, Dr. Reeker. Nor do + I know of any one else who has made experiments of this kind. + However, Professor Landois,[83] the eminent zoologist, now deceased + (founder of the scientific society mentioned), tested four + circus-horses for their musical ability and specifically for their + sense of musical time. He arrives at the conclusion that horses + "have no feeling for time, whatsoever." With but few + exceptions,[84, 85] all experts to-day are of the same opinion. + Horse-trainers, especially, are universally agreed on this point. It + is easy to see in any circus performance that it is not the horses + that accommodate themselves to the music, but that the music + accommodates itself to them, and that the trained horses[86] are + induced to do their artistic stepping only by the aids given by + their riders. Furthermore, all these horses are trained without the + use of music.----It would therefore appear that the time had arrived + when the tales of the dancing horses of the Sybarites ought no + longer to gain credence. Two Greek writers, Athenaeus[87] and + AElian,[88] tell us that the inhabitants of Sybaris, far-famed for + their luxurious habits, had trained their horses to dance to the + music of flutes during their banquets. Building upon this, the men + of Crotona, in one of their campaigns against the Sybarites, ordered + the flute-players to play the tunes familiar to the Sybarite horses. + Immediately the well-trained steeds began to dance, thus throwing + the whole Sybarite army into confusion, and the men of Crotona won + the day. (The same story is told in more detail concerning the + horses of the inhabitants of Cardia. Both accounts, somewhat mixed, + are to be found in Julius Africanus,[89] a writer of the third + century of the Christian era.)--In recent years a French veterinary + surgeon, Guenon,[90] experimented on the effect of music upon the + horses of the military. He entered their stalls, playing upon a + flute, and noted their behavior. Four-fifths of the animals, he + says, were deeply moved, yes, delighted, even, ("charmes." One + interpreter[91] calls it a case of hypnosis!). This emotional + excitement was expressed--somewhat unaesthetically--by the dropping + of excrementa. Guenon characterizes the feeling-state of these + animals as being a mixture of pleasure and astonishment, of + satisfaction and excitement ("melange de plaisir et d'etonnement, de + satisfaction et de trouble.") He also asserts that the horse's + musical taste is similar to our own. But I can find nothing in his + whole exposition which might prove this. Indeed there is nothing + that could be interpreted as anything other than a purely sensuous + effect upon the horses. I may go a step farther and say that thus + far the sense of music, i. e., understanding of melody, harmony and + rhythm, has not been shown to exist in any animal. Some animals may, + however, be susceptible to the sensuous pleasantness of the tones + themselves.] + +I shall now turn to peculiarities of character, highly humanized, which +have been attributed to Hans. His "sympathies" and "antipathies", +so-called, were nothing but erroneous appellations for the success or +failure on the part of the respective individuals to elicit responses. +He who could procure answers frequently, apparently stood high in the +horse's favor. That Hans shook his head violently when asked by Mr. von +Osten: "Do you like Mr. Stumpf?", and answered in the affirmative the +further question: "Do you like Mr. Busch?", was nothing but a +confession--unwilling, to be sure--on the part of the master himself. In +the first case the master thought "no", in the second instance, "yes", +and the two thoughts were accompanied by the corresponding head +movements, to which Hans responded mechanically. Hans appeared to be +well-disposed toward me, but evidently because I always rewarded him +liberally when he answered correctly, and I did not scold him when his +responses were wrong, as did Mr. von Osten and Mr. Schillings, who +instead of seeking the cause within themselves, were always ready to +rebuke Hans for his contrariety and fickleness. The horse did not show, +in so far as can be judged at all, any real affection for his master. On +the other hand it would be unwarranted to say that, in spite of all +rewards, he developed a grudge against all those who bothered him with +instruction and examination. Shortly after the close of our +experimentation it happened that Hans severely injured his groom by a +blow in the face. Yet this man had always been very gentle with the +horse and had been forbidden by Mr. von Osten to make Hans solve any +problems for him. Experts assure me that we have here to deal, not with +a case of "moral insanity", but with a very common experience,--although +this view will probably be cavilled at by enthusiastic lovers of horses. +The work of so excellent an expert as Fillis,[92] for instance, bears us +out in this respect. + +The horse's supposed fickleness was nothing but a token of the fact that +even those who were accustomed to working with him, did not have him +completely in hand. (They simply did not understand how to obtain +correct responses from the horse.) It often happened that in the +evening, when it had become so dark that the movements of Mr. von Osten +could no longer be seen, Hans had to suffer bitter reproaches because he +made so many errors. That, in truth, he never was stubborn and that the +cause of failure really lay in the questioner, is shown by the fact that +the mood, for which he was reproved, would disappear the moment the +questioner voluntarily controlled the signals. We may add that there was +no basis for the assumption that "he had an uncommon, finely constituted +nervous system" or was possessed of a "high degree of nervousness". Both +these phrases were often mentioned by way of explanation. Hans was +restive, as horses usually are. And besides, he lived a life so secluded +(he was never allowed to leave the courtyard) that as a result he was +easily disturbed by strange sights and sounds. There was not the +slightest trace of the clinical symptoms of neurasthenia--on the +contrary he gave the impression of perfect health,--which was curious +enough when we remember his rather unnatural mode of life. + +Hans's stubbornness was a myth. He was suspected of it whenever the same +error occurred a number of times in succession, i. e., when the +questioner did not properly regulate his attention (page 146) or when he +was being controlled by "perseverative tendency", mentioned on page 149. +Mr. Schillings, who has provided me with material here as elsewhere, +relates the following episode which occurred on one such occasion. To +one and the same question put alternately by Mr. von Osten and Mr. +Schillings, Hans responded correctly, with two taps, to the former, and +just as persistently incorrectly, with three taps, to the latter. After +Mr. Schillings had suffered this to occur three times he accosted the +horse peremptorily: "And now are you going to answer correctly?". +Hereupon Hans promptly shook his head, to the great merriment of all +those present. (Mr. Schillings had, with no accounted reason, expected a +"no".) Hans was called willful whenever the same question was +successively answered by different responses, as frequently happened +with the increasing tension that characterized the high numbers (page +145). He was also regarded as stubborn when no reply at all was +forthcoming, as in the tests with the blinders. + +Hans's supposed distrust of the questioner, when the latter did not know +the answer to the problem, is nothing but a poor attempt to account for +the failure of those tests. Hans's distrust of the correctness of his +own responses was supposed to be evident from his tendency to begin to +tap once more if, after the completion of a task, the questioner did not +immediately give expression to some form of approval or +disapproval--just as a schoolboy begins to doubt his answer if the +teacher remains silent for a short time. In terms of the results of our +experimentation this would mean that whenever the questioner did not +resume the erect posture, after Hans had given the final tap with the +left foot, then the horse would immediately begin once more to tap with +the other foot (page 61). + +As the evil characteristics, so, too, the good. Thus, his precipitancy, +which was supposedly evidenced by his beginning to tap before the +questioner had enunciated the question, was nothing but a reflection of +the questioner's own precipitancy in bending forward (page 57). Never +did Hans evince the slightest trace of spontaneity. He never spelled, of +his own accord, anything like "Hans is hungry," for instance. He was +rather like a machine that must be started and kept going by a certain +amount of fuel (in the form of bread and carrots). The desire for food +did not have to be operative in every case. The tapping might ensue +mechanically as a matter of habit--for horses are to a large extent +creatures of habit. This lack of spontaneity could hardly be reconciled +with the horse's reputation for cleverness. It would not be necessary to +touch upon the signs that were supposed to betoken genius: the +intelligent eye, the high forehead, the carriage of the head, which +clearly showed that "a real thought process was going on inside",--all +these, we said, would not need mentioning, if they had not been taken +seriously by sober-minded folk. If there is a report that Hans turned +appreciatively toward visitors who made some remark in praise of his +accomplishments,--it is evidence only of the observer's imaginativeness. + +Turning from a consideration of the horse to that of the persons +experimenting with him,[AH] the first and most important question that +arises is this: How was it possible that so many persons (there were +about forty) were able to receive responses from the horse, and many of +them on the very first occasion? The answer is not hard to find. All of +these persons came to the horse in very much the same frame of +mind--which found a similar expression in all, in both posture and +movements. And it was these motor expressions of the questioner (aside +from the signs for "yes" and "no", which I believe I have adequately +explained on page 98), that the horse needed as stimuli for his +activity. + + [Footnote AH: I cannot enter upon a discussion of the latest + psychological problems, here involved, partly because that would + take us beyond the purpose of this monograph, and partly because + they are still moot questions and hence not suited to popular + treatment. Briefly though, they are these: What is the nature of the + relationship between cognitive and affective states on the one hand + and involuntary, (so-called expressive) movements on the other? Is + this connection an external thing, as it were, an association + arising as a habit formation, or does every idea partake essentially + of a motor character? Do purely cognitive states give rise to such + movements, or does the movement impulse depend more particularly + upon the affective consciousness accompanying the cognitive states? + And in how far do given kinds of expressive movements depend upon + certain ideational types (c.f. page 95)? Thus, what is the + influence of the visual image upon the gestures for "up," "down," + etc.? And then, are these involuntary movements, when not noted, + truly unconscious, or merely not attended to,----in other words, are + they beyond the pale of consciousness or merely "at the fringe?" The + various writers speak almost without exception of unconscious + movements in the strict sense of the term. My own introspections, + however, have led me to doubt whether they are quite unconscious. + Since I have attained some practice I am able to describe in detail + (under conditions of objective control) my involuntary movements, no + matter how slight, even down to mere muscular tensions. None of my + subjects, however, has as yet succeeded in this. It is no very easy + matter to be on the lookout for some unknown movements which might + eventually occur, while attempting to concentrate attention to the + utmost upon a certain definite ideational content, for this very + dividing of attention effects a decrease in the force of the + movement, and thus makes it all the more difficult to discover. From + my own experience, however, I am inclined to believe that these + movements are not unconscious, but merely unattended to, in other + words, we have a narrowing down of the apperceived content within + certain limits, but not a narrowing down of consciousness, (much + less a "splitting" of consciousness or of personality as the thing + unfortunately has sometimes been called). In order, however, not to + be guilty of premature judgment, I have avoided the terms + "unconscious" and "unattended to," and chose expressions which leave + these finer distinctions untouched.] + +The next question that arises is: why did only a few persons receive +responses regularly from Hans, whereas the greater number were favored +only occasionally? What was the selective principle involved? The answer +is, that the successful person had to belong to a certain type, which +embodied the following essential characteristics. + +1. A certain measure of ability and tact in dealing with the horse. As +in the case of dealing with wild animals, such as the lion, etc., Hans +must not be made uneasy by timidity in the questioner, but must be +approached with an air of quiet authority. + +2. The power of intense concentration, whether in expectation of a +certain sensory impression (the final tap), or in fixing attention upon +some idea-content ("yes", "no", etc.). It is only when expectancy and +volition are very forceful, that a sufficient release of tension can +ensue. This release of tension is accompanied by a change in innervation +and results in a perceptible movement. And it was only when the thought +of "yes", or "up", etc., was very vivid, that the nervous energy would +spread to the motor areas and thence to the efferent fibers, and thus +result in the head-movement of the questioner. From infancy we are +trained to keep all of our voluntary muscles under a certain measure of +control. During the state of concentration just described, this control +is relaxed, and our whole musculature becomes the instrument for the +play of non-voluntary impulses. The stronger the customary control, the +stronger must the stimuli be which can overcome it. The steady +unremitting fixation, which resulted in the horse's selection of the +cloths, also involves a high degree of concentration. + +3. Facility of motor discharge. Great concentration was necessary of +course, but not sufficient. Persons in whom the flow of nervous energy +tended to drain off over the nerves leading to the glands and the +vascular system might betray great tension, not so much by movements as +by a flow of perspiration (we have many excellent examples of this given +by Manouvrier)[93] or by a violent beating of the heart, blushing and +the like,--in short, by secretory and vasomotor effects. Or it is not +inconceivable that long dealing with very abstract thoughts might have +weakened the tendency of overflow to other parts of the brain, and that +therefore the entire discharge is used up in those portions of the brain +which are the basis of the intellectual processes. But if expressive +movements occur, the motor pathways must be particularly unresisting in +order to take up the overflow of psychophysic energy. This is the +necessary condition for obtaining the tapping and the head movements on +the part of the horse, although for the tapping there is still one other +circumstance necessary: viz., + +4. The power to distribute tension economically--i. e., the ability to +sustain it long enough, and to release it at the right moment (after the +manner of the curves described on page 93), and to control properly the +unavoidable variations which will occur.[AI] + + [Footnote AI: The mental state just described is probably + essentially the same as that of the spiritualistic "mediums" when + they are occupied with table-rapping and table-moving. In both cases + concentration is very intense,----in other words, the field of + attention is limited. We saw that this state not only favors the + tendency toward involuntary movement, but on account of the + absorption of the individual's attention by a certain limited + content, the person will be unaware of the voluntary movements as + they occur. And we are not necessarily here dealing with + neurasthenic, hysteric, or other diseased nervous conditions. In the + case of table-rapping there are movements of the hands, in our case + there are those of the head. Our head, balanced as it is upon the + cervical vertebral column, is continually in a state of unstable + equilibrium and therefore peculiarly susceptible to + movement-impulses of every kind. But I could induce not only + movements of the head, but also of the arms and legs, and this by + having the subject assume a posture which enabled him to hold arms + or legs in as unstable a position as possible. He might stretch out + his legs horizontally before him, or he could raise them vertically + upward as in the hand-stand in gymnastic work. An extract from a + treatise by Count A. de Gasparin,[94] which appeared about the + middle of the last century, may serve to show how close the + correspondence between the two processes, that of getting the table + to rap and that of causing Hans to respond, really is. The report of + this writer, based upon the detailed record of his tests in + table-moving and table-rapping, closely parallels in many minute + details the observations which were made in the course of our + experimentation with Hans. The case is all the more remarkable when + we bear in mind that this writer did not seek the cause of the + phenomena, as we did, in involuntary movements, but thrusting aside + this explanation, he posited the cause in the agency of some + mysterious fluid. It may not be amiss to say that this as well as + most other references were consulted after the present experiments + and introspections had been completed. Of the page references + preceding the following citations, the first always refers to the + page in the French original, and the other, enclosed in brackets, to + the parallel passage in the present monograph. + + P. 49 [31]. Some questioners are especially suitable + ("experimentateurs hors ligne"), but in their absence, other persons + may also operate successfully ("le succes, quoique moins brillant + alors, n'est pas impossible.") + + P. 25 [229]. But even the most suitable questioners do not always + succeed equally well ("les plus surs d'eux-memes ne reussissaient + pas egalement tous les jours.") + + P. 42 [151]. When the questioner is in any way indisposed, the + measure of success is also less. + + P. 91 & 87 [150]. The Questioner must first get into the sweep of + things ("en train"), and once he has done so, all interruption + whatsoever must be avoided. + + P. 91 [93]. Unless there is sufficient tension on the part of the + questioner, the test will fail. ("La volonte est-elle absente, rien + ne bouge.") + + P. 210 [93]. When there is too low a degree of tension, then too + great a number will be tapped ("si votre volonte ne les [les tables] + arrete pas au moment ou se termine le chiffre pense, elles + continueront indefiniment.") + + P. 31 [93]. But too great concentration of attention will also + produce failure ("s'il n'arrivait ... de desirer trop fortement le + succes et de m'impatienter en cas de retard, je n'avais plus aucune + action sur la table.") + + P. 36 [151]. If the proper mood ("entrain habituel") is wanting and + the tests are unsuccessful, it is best not to attempt some new and + difficult experiment, but to turn to some that are simpler and more + entertaining ("La table obeissait mal; les coups etaient frappes + mollement et comme a regret.... Alors nous avons pris un parti dont + nous nous sommes bien trouves; nous avons persevere, et persevere + gaiement; ... nous avons ecarte la pensee des tentatives nouvelles, + et insiste sur les operations aisees et amusantes. Apres un certain + temps les dispositions etaient changees, la table bondissait et + attendait a peine nos commandements.") + + P. 199 [41, 90]. It is not necessary to enunciate the questions + aloud ("On est convenu que celui qui commanderait ne prononcerait + pas a haute voix le nombre de coups, mais se contenterait de les + penser, apres les avoir communiques a l'oreille de son voisin. Eh + bien! la table a obei. Il n'y a jamais eu la moindre erreur.") + + P. 199 [64 ff.]. The large numbers are tapped more rapidly than the + small ones ("la table a indique notre age tel qu'il etait dans notre + esprit, se hatant meme de la maniere la plus comique lorsque le + nombre des coups a frapper etait un peu considerable.") + + P. 210 [35 ff.]. Tests in which "procedure was without knowledge" + failed completely ("Les tables ne revelent pas ce qui n'est pas dans + la pensee et dans la volonte de l'experimentateur; quand on veut les + charger d'autre chose que d'obeir comme des membres, on arrive a des + erreurs continuelles.") + + P. 28, 29, 217 [72]. When of two experimenters each tries to get the + horse to tap a different number, then that one who is the better + able to compel the animal's attention, will be the successful one. + ("L'un veut faire prevaloire un chiffre pense plus considerable, + l'autre un chiffre pense moins considerable.... Eh bien: l'operateur + le plus puissant l'emporte." "Ainsi A est charge secretement de + faire frapper 25 coups, B est charge secretement de l'arreter a 18; + A l'emporte, et les 25 coups s'achevent.... On fait maintenant + l'inverse: B est charge secretement de faire frapper 13 coups; A est + charge secretement de l'arreter a 7; A l'emporte encore et le + chiffre 7 ne peut etre depasse.")] + +The experience of a number of practical men, who have had much to do +with horses and yet achieved but very modest success with Hans, goes to +show that it is not always the lack of sufficient authoritativeness, +mentioned under heading 1 that is the sole cause of failure, as has been +claimed so often. That the horse was, to a certain degree, influenced by +this element of authority is shown, however, by the following incident. +A certain gentleman, when alone in the courtyard with Hans, received +responses only so long as I (concealed in the barn) kept the barn-door +open just a little, so that my presence could be known to the horse. As +soon as I closed the door, Hans refused to respond to the gentleman. +Those who possessed sufficient power of concentration and the requisite +motor tendency--the two characteristics mentioned under 1 and 2 +above,--were able to obtain responses from the horse without any +previous practice. Practice merely effected a more economic distribution +of attention, so that the larger numbers especially were more successful +as a result (pages 68 and 89). Those who were lacking in either of the +characteristics mentioned under 2 and 3 would not be aided even by the +greatest amount of practice, as is shown by the case mentioned in +Supplement III (page 255).--That many individuals were at first +successful but were later unable to get any successful responses, is to +be accounted for by the fact that the power of concentration, at first +present, later rapidly disappeared. This temporary increase in the power +of doing mental work was first investigated experimentally by Rivers and +Kraepelin,[95] and was called by them "Antrieb" and aptly likened to the +first pull of a team of horses in starting off. This, too, explains an +experience which befell a number of the horse's visitors, who later +described it to me. Wishing to utilize a momentary absence of Mr. von +Osten, they excitedly put a hasty question to Hans, and with amazing +regularity received correct responses.--Besides Mr. von Osten, Mr. +Schillings and myself, not many were always able to induce Hans to bring +the colored cloths or to execute the head movements. It was easy, on the +other hand, to get him to nod. Therefore there was some truth in Mr. von +Osten's assertion, that Hans would be unable to answer a difficult +question if he had not previously indicated by means of a nod that he +had grasped its import. Those who were not concentrating sufficiently, +would not look into Hans's face, when he was expected to nod, and would +not bend over, when Hans ought to begin tapping--such persons could not, +therefore, since they did not induce Hans to nod, elicit the tapping. I, +myself saw the "no" successfully elicited only in the case of Mr. von +Osten, Mr. Schillings and Mr. Hahn; the "right" and "left" only in the +case of the former two. It must remain uncertain whether this failure on +the part of otherwise suitable persons to elicit the responses for +"right" and "left" was due to their accompanying these ideas by +movements of the eyes instead of by movements of the head, (page 106). +For unfortunately it was not possible to make special tests to discover +whether Hans reacted to isolated eye movements. There is, however, more +than one reason why I would doubt this. Taken all in all, there were but +few persons who were entirely representative of the type described (c. +f. page 31)--they were those who are commonly characterized as being of +a lively temperament and strongly impulsive. Thus Hans acquired a +reputation for "Einkennigkeit", that is, he would accustom himself only +to certain persons. Such a reputation was hard to reconcile with his +much praised intelligence. + +In closing, just a word on the influence of the public that was present. +As was shown on page 69, the public in general did not influence the +horse in his reactions. The effect upon the questioner, however, was +unmistakable, and worked in a twofold manner. On the one hand the +questioner's zeal was increased and with it the tension of +concentration. On the other hand, it introduced an element of diversion, +and attention was divided between the horse and the spectators, and thus +concentration suffered. If the disturbing effect was slight, as in the +case of Mr. von Osten, then the favorable influence exercised by the +presence of the public outweighed the unfavorable. Mr. von Osten was, +for that reason, often particularly successful when working in the +presence of a large body of spectators. This was noted by many and was +ascribed to the ambition of the horse. When, however, a person was +easily diverted, as was Mr. Schillings, then the presence of the public +had a less fortunate effect. + +This, then, completes my explanation of the facts gleaned from +observation and experimentation. It accomplishes all, I hope, that may +be expected of an explanation. All the known achievements of the horse, +all the successes and failures of the questioner, have been reduced to a +single principle; no secondary hypothesis has been invoked, and but +slight place has been given to the element of chance. Nevertheless, it +may not be out of place to forestall two objections which might possibly +be raised. First, some may assert that it was through our +experimentation that the horse became mechanized and incapacitated as +regards conceptual thinking; that formerly he really could solve +arithmetical problems, and only later developed the very bad habit of +depending upon the signs which I gave him. This objection is to be +refuted in that I did not originate these signs, but first noted them in +Mr. von Osten, himself, and in that Hans still works as faithfully as +ever for Mr. von Osten. I have learned from many trustworthy witnesses +that the horse still continues to give brilliant exhibitions of his +"ability". If, on the other hand, anyone should assert that it was only +with us that Hans reacted to movements, but that with his master he +really thought and still thinks, then I must ask for proof. This latter +argument is by no means very original. When Faraday in 1853 proved +experimentally that "table-rapping" is the result of involuntary +movements on the part of the participants standing about the table, the +spiritualists asserted that his experiments had nothing in common with +their own proceedings, because his subjects (who by the way, had been up +to that time firm believers in table-rapping) probably did move the +table, they said, while they (the spiritualists) do no such thing.[96] + + + + +CHAPTER VI + +GENESIS OF THE REACTION OF THE HORSE + + +In the preceding discussion we have regarded the achievements of the +horse as well as Mr. von Osten's explanation of them, as matters of +fact. Let us now consider the question: How did the horse come by these +achievements, and how did its master arrive at his curious theory in +explanation of them? Did he indeed seek to instill in the horse's mind +the rudiments of human culture through long years of painstaking +instruction in accordance with the method described in Supplement I +(page 245)? If that is the case, then, of course his hoped-for success +was only seeming, not real. Or did he, as so many critics aver, +systematically train the horse to respond automatically to certain cues, +and propound his theory merely for the purpose of misleading the public? +There might possibly be another alternative, viz.: was there a mixture +of instruction and of training to respond to cues? + +The production of the horse's achievements would not require a great +deal of explanation, if it were a case of mere training for the purpose +of establishing certain responses to certain cues. It might be +desirable, however, before deciding in favor of one of these +possibilities, to indicate briefly the process of development, as it +might occur, if the point of view is taken that _bona fide_ instruction +was given. + +This development would probably be as follows:--Mr. von Osten, as the +result of theoretical speculation or of a misinterpretation of the facts +of experience, having arrived at the conclusion that the horse possessed +extraordinary capacity, finally undertook to instruct a certain horse +for a period covering three years. This one having died, he, nothing +daunted, undertook the education of another one. What it was that +influenced this old teacher of mathematics to deprive humankind of the +benefit of his extraordinary pedagogical ability and love of teaching, +we do not know. It may be that he had had bitter experience in that +line, or again, mayhap the newness and tremendousness of this other task +stimulated him. His first problem must have been to arouse the interest +of the animal in this process of education. It was hardly to be believed +that Hans would eagerly cooeperate in a process which promised to yield +him no immediate benefit. The teacher sought to overcome this lack of +immediate interest by the means of rewards. To Hans the sweet carrot was +as toothsome a bite as candy is to the child. And since the horse was +furthermore kept on low rations on account of the relatively low amount +of physical exercise he took, the anticipation of the carrots was doubly +enticing. + +The first thing that Mr. von Osten sought to teach the horse, according +to his own statement, was the significance of the names of colors and of +the spatial directions such as "up", "down", etc. In the case of +children there is a simple test by means of which we may discover if +they have put any content into these words. The test is: Do they, +themselves, use them correctly? Do they call the blue, blue, and the +red, red? Since the horse could not speak, his instructor had to give +him some means by which he could make himself understood. He taught +Hans to approach the colors and select the cloth of the color wanted. He +also taught him to make those movements of the head or body which +correspond with the expressions: "up", "down", etc. + +First of all, Hans had to be taught to bring the cloths. Then began the +pointing out of the different colors, accompanied each time by their +proper names. It is very probable that at first Hans had to be led each +time to each separate colored cloth and taught to raise it or to touch +it with his nose. Later, Mr. von Osten, after having pronounced the name +of the color, remained at his place, with his head and body directed to +the cloth in question and gazing intently at it, in order to see whether +or not the horse was pointing out the right one. Naturally Hans would, +at first, fail a hundred times where he would succeed but once, but +since the horse would receive the anticipated reward in case of success, +he gradually became conscious that this reward was attached to +executions which had some special mark. This special mark would be +expressed in human speech by the statement that the horse would go in +the direction indicated by the position of the instructor's body. For +Hans, of course, this would not take the form of an abstract statement, +but simply of a definite way of seeing and of going and a correlation of +the two in a certain definite manner,--the whole being a process, the +elements of which remained unanalyzed and unaccounted for by Hans. Owing +to the position of the eye, it was possible for him to keep his master +within his field of vision, while he was approaching the cloths. And +only when he had correlated his approach in a certain definite manner +with his visual perception of the master, i. e., only when he had felt +his way, as it were, along the latter's line of vision, did he receive +his reward. A sufficient number of repetitions was all that was +necessary to establish an association in the psychological sense of the +term. In the same manner, dogs will learn, as was indicated on page 177, +to bring an object upon which the master has fixed his gaze, it +mattering little whether or not the name of the object be enunciated. +There is only this difference, that, in the case of the dog it is not +possible to keep the image of the master within the field of vision; but +neither is it necessary, for he has recognized the object before he has +started for it. We must remember, however, that it does not simplify an +attempt at explanation to assume that Mr. von Osten consciously trained +the animal to respond to certain bodily positions of the questioner. +For, even in this case, it would be necessary to explain how it was +possible for him to train the horse to heed the cues.--In the course of +time, the instructor may have noticed that whenever he moved during the +course of a test the horse invariably failed. But he may have regarded +this merely as an incidental distraction and afterward was careful to +remain quiet. As soon as he increased the number of cloths upon the +floor, it was no longer possible for him to give the horse such accurate +directive signs, and the number of errors consequently increased. +Ascribing them to the inattentiveness of his pupil, he sought to +encourage him by such calls as "look out", "look there", "see there", +believing that, thus, he was directing the horse's attention to the +desired color. Without understanding the meaning of the calls, Hans +learned, however, to keep moving just as long as the calling continued, +for if he did this he was regularly rewarded. An association was +established between the call and the impulse to move on. And with these +two associations established, Hans gave the impression of having grasped +the meaning of the color terms. + +The origin of the proper movements in response to the terms "up" and +"down" may be explained by the fact that the movements themselves were +practised in a purely external fashion. Thus, whenever the word "left" +was pronounced, the horse's head was pulled to the left by means of the +bridle or the reward was held off to that side. Later, Mr. von Osten, +who looked expectantly at the horse's head, whenever he pronounced the +word would unconsciously move his own head in the direction in which he +desired the horse to turn. This is quite in accord with the words of +Darwin to the effect that whenever we wish an object to move in a +certain direction it is well-nigh impossible for us to inhibit an +unconscious, involuntary movement in that direction. Proof for this may +be found on all sides, in daily experience.[97] Imagine, for instance, +the strain sensations of the bowler or billiard player as he follows the +moving ball. It is impossible to decide whether Mr. von Osten, +consciously continued to image the head movements which he expected the +horse to make or whether these anticipatory images later remained below +the threshold as was always the case with Mr. Schillings and myself (see +page 100). But this question is of little significance, for even +assuming that he always thought of the movement he expected on the part +of the horse, this by no means implies that he was conscious of the +movements on his part, which were associated with the thought process. + +Everything up to this point might be explained as the working of simple +memory association, but when we come to problems in counting and +arithmetical calculation, we are in the field of conceptual thought. +Here, again, it was necessary for Mr. von Osten to invent a suitable +means of expression for the horse, and once more this had to be borrowed +from the treasury of gesture-language. Tapping with the hoof was +naturally hit upon as one of the normal, expressive movements of the +horse. This has long been used by trainers, in preparing horses for show +purposes. The method used in training the horse to make this response is +of no import, whether it was by touching his foot with the hand, or +tapping his leg, or by any other means. + +It is possible that many will declare, as being nonsensical, any attempt +to introduce number-concepts[AJ] into an animal's mind, because the +necessary motor basis is lacking. We will not, just at this point, stop +to discuss whether or not it was not possible to develop number-concepts +from purely auditory or visual representations. It is evident, however, +that Mr. von Osten believed that a motor basis of some sort was +essential. In the case of man this basis is found in the enunciation of +the number names (or in the manipulation of the fingers). Mr. von Osten +seemed to think that he was justified in assuming that, even in the case +of the horse, some form of inner articulation of the word-sounds was +possible;--at the same time, in so doing, he did not blink at the +psychological difficulty of this hypothesis. The tapping of the foot was +to be regarded merely as the expression of the process of inner +counting, but not as the motor basis of the process. For this latter +purpose tapping would be quite inadequate, for the number complexes +which arise in the summation process of counting, could not be +differentiated by mere tapping with the foot, any more than a child +could learn to count by employing only one finger. Mr. von Osten +evidently imagined the process was somewhat like this: Whenever Hans was +about to count 5, he would enunciate inwardly the numbers from 1 to 5, +and would accompany each word with a tap of the foot. Since, +furthermore, wooden pins and balls could be used--as in the case of +children--for giving visual content in learning the significance of the +number-terms, it seemed as if all the conditions necessary for the +formation of number-concepts were supplied. However, the most essential +thing had to be presupposed, viz.: that the horse virtually possessed +the general power of forming concepts,[AK] and that all that had been +lacking was the suitable conditions for its development. Mr. von Osten +held tenaciously to this conviction, and it was this conviction that was +the basis for the infinite patience with which the tests had been +pursued. + + [Footnote AJ: The author intends to take up the problem of counting, + so-called, on the part of animals and of the principle involved, in + another work soon to be forthcoming.] + + [Footnote AK: There are some who believe they are warranted in + concluding the opposite from the structure of the animal's brain + alone. We may say that the brain of the horse, compared with that of + the ape, or even that of the dog, represents a relatively low type + of development. But owing to the rapid changes in the views, often + contradictory, concerning the nature of the nervous structures and + processes underlying the thought process, any conclusion based on + such views would be premature. For this reason we cannot agree with + the French physiologist who was dissecting the brain of a horse and, + struck by its smallness of size, exclaimed: "When I saw your proud + look and beautiful neck, I hesitated a moment before mounting upon + your back. But now that I have seen how small is your brain, I no + longer have any qualm about using you."[98]] + +To come now to the learning process itself;--we may assume that, at +first, whenever the horse began to tap in response to commands, he would +receive a reward for this purely mechanical feat. Wooden pins were then +planted on the ground and designated as: one, one two, etc., and each +time someone would raise the horse's foot as many times as the count +demanded (see Supplement I). Then Mr. von Osten would take his stand at +the horse's side and would command him, let us say, to tap 3. Hans +noting merely (from his master's position) that he was expected to tap, +would begin. The instructor, who had bent forward in order to watch the +horse tapping,[AL] would involuntarily straighten up again at the third +tap, without being conscious of it and quite unaware that he was thus +giving a signal. The horse would be startled, and sometimes he would +immediately cease tapping and sometimes not. But it was only in the +first case that he would receive a reward. Thus, unknown to the +instructor, an association became established between the sight of the +upward jerk of the instructor and the act of ceasing to tap. To be sure, +the animal would receive sundry visual impressions from the wooden pins +set up before him and the auditory stimulations of the spoken number +names, on the basis of which, the concepts were to be formed in his +mind. But in this chaos of visual impressions (at times there were two +wooden pins, then three, then four, sometimes there were the pins, at +others, the balls of the counting-machine)--and in the babel of +word-sounds--which evidently meant nothing but noise to him--amidst all +this there was but one constant element: the final movement of the +instructor's body. The moment the horse reacted to this, he would +receive the tidbit at the hands of his overjoyed master, and thus he +became more and more accustomed to attend to this jerk, even after it +had gradually decreased in scope. And the reason again, why this jerk +tended to become less pronounced was that the tests were gradually +becoming more and more successful. For, corresponding to the degree in +which the horse began to react properly, the instructor's tenseness and +excitement tended to decrease, and with this decrease of the emotional +element in the man's consciousness, the accompanying non-voluntary, +expressive movement gradually became less pronounced until it attained +that extraordinary refinement which it possesses to-day. We noticed +also, that whenever the horse, for any reason, had to be trained anew, +Mr. von Osten's movements would, on the whole, become somewhat more +gross, as for instance after the tests with the blinders. There is not a +shadow of a doubt that this increase in the movement's extent was +entirely unintentional, since the horse could not see his master at all +on account of the blinders which had been attached to the trappings. + + [Footnote AL: This natural and close connection between the process + of attention and the movement toward the object attended to is + clearly expressed in our English and French terms, derived from the + Latin "tendere ad--," to reach toward--.] + +In the same way it is possible to explain the details. Mr. von Osten +himself said that at first Hans had tapped at times with his left foot, +at times with his right, just as he pleased. But later his master taught +him to tap only with the right. Whenever he began with the left, Mr. von +Osten would immediately interrupt him, and he was allowed to add only a +final tap with his left foot. Thus, this additional tap which was +sometimes made with the left foot was but the vestige of an earlier +rudimentary habit. The signal for it was the stooping posture in which +the master remained after the head-jerk had been made. Whenever Mr. von +Osten had given Hans a small number to tap, he would bend forward only a +little. But when he expected a larger number he would bend forward +somewhat more, owing to the desire to observe the tapping more +carefully. From the slight inclination of the master's body the horse +would get the cue that he was expected to tap for a short time only, by +the greater degree of inclination he would know that he was to tap for a +longer period. In the second case he tapped rapidly and did not raise +his foot as high from the ground--evincing a regard for the saving of +energy, which may well be attributed to a horse. And thus arose the +connection between the degree of inclination of the instructor's body +and the horse's rate of tapping. + +So, now that the ability to count and solve problems had become +fixed--as the old gentleman thought--he began to instruct the horse in +other branches. Since everything had been translated into terms which +were to be expressed by means of tapping with the foot, and thus really +put into terms of number--which was perhaps natural for an old teacher +of mathematics--the same mechanism was involved in these accomplishments +as in those of counting, etc. Mr. von Osten saw the animal's +intelligence steadily increase, without having the slightest notion that +between his words and the responsive movements of the horse, there were +interpolated his own unconscious movements--and that thus instead of the +much desired intellectual feats on the part of the horse, there was +merely a motor reaction to a purely sensory stimulus. It has been a +common custom of man to posit some extraneous cause for movements +resulting from certain involuntary motions of his own, of which he is +not aware, (witness the divining-rod).[AM] And furthermore, when these +results appear to be rational, the tendency is to seek their cause in +some extraneous intelligence, not his own. Just as the spiritualists +ascribe the "messages" which are revealed to them through table-rapping, +to certain rational spirits, so Mr. von Osten credited the intelligence +of the horse with the result produced by his own involuntary signs--i. +e., with the proper solution of problems. + + [Footnote AM: G. Franzius,[99] privy counselor of the admiralty, + master of the dry-dock at Kiel, is responsible for the undeserved + revival of the ancient belief, long buried by science, that the + divining branch is put into motion solely as the result of the + influence of hidden springs or treasures, and without any agency in + the person who is holding it. The untenability of this theory comes + home to us most forcibly when we recall how various are the kinds of + things which have been discovered by means of the branch. First + there is gold and water, which are the only ones mentioned by Mr. + Franzius. The water can be thus discovered only when it flows below + ground, say that which is passing through the mains of a city, + whereas the water of the Rhine or the Elbe would have no effect on + the branch. Besides gold, every other kind of metal has been + supposedly located by the branch,--as well as coal, gypsum, ochre, + red-chalk sulphur and petroleum,--according to the desire of the one + searching. Thus, the very same branch that just a moment ago was + influenced by the least bit of underground water, may remain + unaffected by the presence of a large body of water, if in the + meantime I have changed my plan and decide to search for coal or for + gold. But that is not all. The branch will point out a murderer or + the place where a murder has been committed, it will discover the + thief or his trail, as well as the things stolen or merely touched + by him. It will indicate where the boundary-stone that has been + moved, ought to stand. The branch further discloses the sins of the + persons concerning whom it is consulted, as well as their talents + and abilities, the journeys they have made and the wounds they have + received. It will indicate whether or not a person has money and how + much. It can announce what absent persons are doing and what apparel + they are wearing, and of what color it is. It will give information + on theological, medical, zoological, and botanical questions. In + fine, no matter what the question, it will never fail of an + answer.[100, 101] + + The impossibility of explaining the phenomena in a purely physical + way was recognized at a very early date. For a long time the + activity of the users of the divining rod seems to have been + restricted to the search for metals. The first (or one of the first) + to raise his voice against it was the learned G. Agricola[102] + (1556), and after him there were many who all wrote more or less + independently of one another. Aside from swindle and chance, it was + usually believed that sorcery of the agency of Beelzebub was + involved, and for that reason the Church has repeatedly forbidden + the use of the divining-rod. But even in the 17th century we find + some who believed that it was imagination alone that moved the + person's hand, and with it the rod,[103, 104] ("fortassis etiam + phantasia manum in motum concitante"); and that points out the + essentials of the solution of the phenomenon, and we will not go + into the matter here in detail. A number of complex psychological + problems arising in connection with it are still waiting to be + solved, but this much appears certain; the staff or branch plays no + other part in the whole process than that which is served by the + three levers in the tests described in Chapter IV (pages 116 + ff.),--they simply magnify the expressive movements of the diviner. + And so we can understand why the instruments serving as rod might be + so varied. Hay-forks, pickets, clock-springs and pendulums, scissors + and pliers have been used. A knife and fork or two pipes, fastened + together, an open book, and even a sausage, grasped at both ends and + thus bent together somewhat,--all have served the purpose equally + well. We can understand, too, how some adepts are able to achieve + the same degree of success--for they do succeed beyond a + doubt--without any rod whatever, but simply by placing the index + fingers end to end and bending them somewhat, and even by merely + groping about with hands outstretched or folded before them.[106]] + +Two other phenomena may have tended to strengthen Mr. von Osten's belief +in Hans's intelligence. One was the misleading similarity with which the +horse's supposed errors in computation and the poorly adjusted +concentration of the questioner, were expressed. We recall the +difficulty in the case of very high numbers. This might easily be +considered as being due to the horse's ability to work more readily with +small, rather than with large numbers, whereas, as a matter of fact, it +was due solely to the difficulty of the questioner to keep his attention +concentrated upon the number for so long a time. We recall also the +frequency of errors of one unit too few and one unit too many. These +were easily interpreted as miscounts on the part of Hans, but in truth +were the result of the poorly concentrated attention of the questioner. +Added to this was the seeming independence and self-sufficiency of the +horse. Often the number given by him was other than that desired by his +master. Usually Hans was in the wrong in such cases, but sometimes, too, +he was right. At any rate, this served to give the impression of +independence of thought which his master so thoroughly believed he +possessed, and which was the goal of his endeavors--though as a matter +of fact he was farther removed than ever from that goal. + +Some may ask: Does not this whole process partake of the essentials of +all training, (though cumbersome and misunderstood, to be sure), and is +there any need of investigating whether or not the actual development +was of the sort here outlined, or whether it actually took the course +common to all training? + +In order to answer this question we must determine more specifically +what we mean by the term "training". Usually we take it to mean the +establishment in the animal, of definite habits of motor reaction in +response to certain stimuli purposely selected by the trainer, and +without involving any process of animal consciousness other than +association. Such a conception may be applied also to man, if we assume +that the higher thought processes can be eliminated. If that were the +case, the above definition would not have to be changed, not even with +regard to the word "animal", for we must take it in the antique sense of +"zoon", a signification readopted by modern zoology. The concept may be +widened, however, by omitting the differentia of "purpose", or even +more, by including the habitual association of ideas or images (instead +of movements) with certain sensory stimuli. But in so doing, we must +bear in mind that we are going beyond the usual content which in +everyday practice is put into the term "training". Especially, when we +cease to regard the presence of purpose in the trainer's mind (both in +giving the stimulus as well as in the habituation of the animal to them) +as essential. When this is done, the conception of training really +resolves itself into the much wider conception of habit-building, and +the whole discussion becomes merely a quarrel over words. In order to +obviate this, let us bear in mind that in the following, the word +"training" is always taken in the usual and narrower sense. The term +then is still ambiguous only in so far as it has not merely its original +significance of the _act_ of purposely habituating (a person or an +animal) to perform certain definite movements, but by transference is +also used to denote the _effect_, i. e., the occurrence of the movements +in question. But this does not really detract from the clearness of the +concept itself. + +Having cleared up the question of definition, let us return to our +original problem: Does the hypothetical account of the probable +development of the horse's reactions, which is given on pages 213 to +220, represent a case of training? This must be denied decidedly with +regard to the tapping of numbers and the solution of arithmetical +problems. For here the sensory stimuli which were purposely given, i. +e., the wooden pins, the balls, and the spoken words, were intended to +subserve the function of arousing not movement, but thought processes in +the horse; whereas the function of the horse's movements was to give +expression to these thought processes. Of the really effective +stimuli--the slight movements on his part--the master was never +conscious, much less were they purposely made. The same holds true for +the "up" and "down", "yes" and "no", etc., for here also Mr. von Osten +counted upon the rise of the corresponding concepts, and not merely upon +a purely external, mechanical association of meaningless sounds with +certain movement-responses on the part of the horse. This might also +explain the genesis of Mr. von Osten's belief that Hans was able +mentally to put himself in the place of the questioner, (page 19). At +any rate it is very improbable that he, Mr. von Osten himself, clearly +distinguished between the concept: "up" and the sound of the word "up". +When we come to consider the horse's selection of the colored cloths, +and even more his leaping and rearing, we find that the distinction +between "training" and "instruction" vanishes. If we had to deal only +with this class of achievements, we might perhaps say, without fear of +going very far wrong, that the only difference between this and the +ordinary form of training was that Mr. von Osten had intended to train +the horse to respond to auditory signs (words), but had unintentionally +trained him to respond to visual signs instead. But it is not this type +of performance that has become the bone of contention. Just as it would +be misleading to maintain that Mr. von Osten's effort was nothing other +than a case of training, so it also would be unjustifiable to designate +the results of his effort by that name, since the really effective +stimuli were not, as has been pointed out just now, given intentionally. + +As far as the horse is concerned, it is a matter of indifference whether +or not really effective stimuli were given intentionally by the +questioner. The animal knows nothing of human purposes and if he were +transferred to a circus, he would find nothing new in the method +employed there, except the use of the whip. We, however, define our +concepts from the human and not from the horse's point of view. We may +definitely say, therefore, that the method described cannot be regarded +as that of training, neither in its application nor in the effect +produced, though in the latter it closely simulates the effects of the +training method. + +Having thus differentiated between the methods of instruction and +training, let us now attempt to decide on the basis of such indications +as we may possess, which of the two was actually represented by the +development of the horse's attainments. Surveying the facts which we +have at hand, we may say that there are hosts of reasons why we cannot +assume that it was a case of training. Everything that we know from our +own observation and from the well-attested statements of others, with +regard to the actual process of instruction, weighs against the +assumption. Another evidence of this is the long period of time which +Mr. von Osten required (both in the case of Hans, as well as with his +predecessor), whereas the same end would have been much more speedily +attained if it had been a case of training. A further argument is the +fact that a large horse was selected for the purpose, whereas a small +mare would have been far more suitable, (c. f., "Clever Rosa", page 7). +Again, the whip, that sorcerer's rod of all professional trainers, was +here absent. And finally, many traits of character of Mr. von Osten, as +well as his conduct during the whole course of events, militate against +such an assumption. He generously turned the horse over to us, as he had +given it over to Count zu Castell, Count Matuschka and Mr. Schillings. +He eagerly besought a scientific investigation. He had made several +reports to different ministries. All of these acts could only hasten the +denouement. What could have been his motive? Some thought they detected +an effort at pecuniary speculation, and an advertisement of June, 1902, +in the "Militaerwochenblatt", in which Hans was offered for sale, seemed +to confirm the conjecture. Mr. von Osten says that this occurred at a +time when he himself was sick and had become tired of the job. And why +should he not be willing to sell even a thinking horse, since he had +become convinced that any other could be instructed in the same way? +Besides, I have it on good authority that after the publication of the +September report he received several exorbitant offers; to mention only +one of them: a local vaudeville company was ready to pay him 30,000 to +60,000 marks per month. He refused every one of these offers. Some may +say that perhaps he wanted still more. But if he knew that the day of +judgment was close at hand, he also knew that before then, if ever, was +the sunshiny day on which to make his hay. A more auspicious time he +could never hope to see again.--Let us add, once more, that he never +charged admission to any of Hans's performances, although there were +many who were anxious to see the horse, and many enthusiasts had come +from a great distance. And finally, he was an old man, unmarried and +entirely alone, a property owner, but a man whose wants were few and +very simple--and his Hans was almost his sole companion. Is it possible +that such a man, one who had all the pride of gentle birth, would become +a trickster in his old age, all for the love of money? + +The unreliability of Mr. von Osten's signs is good proof of their +involuntary nature. Anyone who had seen him work with the horse could +not have helped noticing that he certainly did not have complete control +over the animal, and was not able, at a given moment, to make Hans +perform a certain feat, as would have been the case if the process had +been one of "training". Again and again Hans failed to make the right +count. Before a large audience, one time, it took four tests to get him +to tap properly up to 20, and in all four I could note clearly that it +was Mr. von Osten who, by his involuntary premature movements, was the +innocent cause of the failure. On another occasion, after Hans had done +some beautiful work in fractions, in the presence of a large number of +spectators, the master asked him the simple question: "Where is the +numerator in a fraction?"--The answer was first: "to the left", and +then, after a severe reprimand: "down" (below), and finally: "up" +(above). He often made just such incorrect movements of the head. In the +color-selecting tests the average of error was quite unpredictable. With +an equal number of tests, on one day, half would be successful, on +another, four fifths, on a third, one-tenth. Often Hans appeared to be +"indisposed" for days at a time. The color tests would often end in +expressions of rage on the part of Mr. von Osten and in consequence Hans +would become startled and would then storm about the courtyard so that +it was dangerous to try to approach him. Some may object that all this +was mere comedy and that possibly Mr. von Osten prevented some of the +tests from turning out successfully. But this objection is to be met by +the statement that very often failure would occur just when it was +particularly desirable to have the tests appear in a favorable light +before a large and enthusiastic assemblage of visitors. After such +failures he would be downcast on account of Hans's contrariness. It is +also significant that Mr. von Osten's percentage of error, corresponds +very closely with my percentage of error in the "non-voluntary" tests, +(page 84f.), whereas he never was able to obtain the errorless results +which I obtained in my "voluntary" experiments. + +But we must be careful not to confuse non-voluntary movement and lack of +knowledge of the movement. And again we must distinguish between +knowledge of the grosser and the finer signals. Mr. von Osten was aware +of the grosser movements, and talked quite freely concerning them, but +in so doing, showed that he was quite unaware of their true function. He +undertook to show us what we already knew--that, when he remained +standing perfectly erect, he could elicit no sort of response from Hans. +Furthermore, that whenever he continued to bend forward, Hans would +always respond incorrectly and with very high numbers. He knew, also, +that Hans was distracted in his operations every time the questioner +resumed the erect posture while the tapping was in progress. This he +demonstrated to us on one occasion in the following manner. He said to +Hans: "You are to count to 7; I will stand erect at 5". He repeated the +test five times, and each time Hans stopped tapping when the master +raised his body. Several such tests resulted in the same way. Mr. von +Osten, however, believed this to be a caprice of the horse and at first +declared that he would yet be able to eliminate it, but later became +resigned to it as an irremediable evil. Mr. von Osten was also aware +that the questioner ought not move while the horse was approaching a +colored cloth, and cautioned me in regard to it, though I had already +noted as much. And finally, he also knew what influence his calls had +while the horse was selecting the cloth, and he told me that it was of +great assistance to Hans to be admonished frequently, since thus his +attention was brought to bear upon the proper cloth. Yet, when we +requested Mr. von Osten to desist calling, since he was thereby +influencing the horse in the choice of the cloth, he answered: "Why +that's just what I wish to do!"--But though the statement that he was +aware of the nature of these grosser signs is thus seen to be true, it +by no means necessarily implies that he had purposely trained the animal +to respond to them. In these observations of his he had builded better +than he knew--he evidently had no notion of their scientific +significance. But the same thing might happen to those who were supposed +to be somewhat less naive, as is shown by the experience of Mr. +Schillings, who quite unconsciously, for many months had been giving not +only the finer, but also the grosser signs, and never guessed the true +nature of affairs until I explained it to him. Nor was it an easy matter +for me to get at the facts involved in the process, although it now all +appears so very simple. + +On the other hand, it is also true that Mr. von Osten knew nothing +whatever of the finer, more minute signals, such as the final jerk, the +head-movement upward, downward, etc., and it is difficult to conceive +how he might have gained any knowledge of them. We might perhaps +conceive of four possible sources. He might have come upon them by +chance. But it is extremely improbable that in the million of possible +forms of signaling he should have hit upon those that at the same time +represent the natural expressive movements. Or he might have derived a +knowledge of them through a study of the pertinent literature. I have +searched diligently for such a source, in both the old and the modern +literature, but in vain. From the sixteenth century on, there is a +series of accounts of horses that were able to spell and to solve +problems in arithmetic, and the reports on learned dogs go back even to +the time of Justinian, in the middle of the sixth century.[107] All of +these animals were kept for purpose of speculation and were exhibited +for pecuniary reasons only. Nor does one read that any person could work +with these animals off-hand, which was the characteristic feature of the +Osten horse.[AN] In many cases we find mention made of the signs to +which the animals reacted. Thus for the beginning or stopping of the +animal's scraping or tapping, the signals were respectively raising and +lowering of the eyes on the part of the trainer,[113] lowering and +raising of the whip[114] or of the arm, stepping forward and +backward,[115] and as a closing signal a slight bending forward.[116] +The signals for beginning and ceasing to bark in the case of dogs, were +the trainer's commands to "speak", and, at the same time, his looking at +the dog, and then looking away for a closing sign;[117] or a +mouth-movement on the part of the trainer and then a withdrawing of the +left hand which had been resting on the hip.[118] Among the signals for +nodding and shaking the head we find the following mentioned: raising +and lowering the hand or arm[119] or the whip;[120] a movement of the +hand toward the horse's nose, as a signal for nodding, and an +arm-movement as a signal for shaking the head.[121] For this last, we +find recommended also a slight breathing upon the animal,[122] and--in +the case of dogs--a mouth-movement simulating blowing, or a turn of the +fingers.[123] (We will not dwell upon the many signals for selecting +objects, which are mentioned, since we have already discussed this point +on page 230f). In all these instances it is plain that we have to do +with purely voluntary and "artificial" signals. The only example of +involuntary signs which Mr. von Osten could have found in literature, +was that of Huggins's dog, which need not be considered here, since, as +was said on page 177, the really effective signs in that case were not +discovered. A third means by which Mr. von Osten might have gained a +knowledge of the involuntary, natural expressive signs, would have been +by observing others. If he had had opportunity of observing another von +Osten and another Hans, he might have gotten at the secret. But since +this was not the case, this possibility vanishes. A fourth possibility +is self-observation. We would then have to assume that Mr. von Osten at +first really tried to educate the horse to think, but soon recognized +the fruitlessness of such an attempt. At the same time, he then would +have noticed his own involuntary movements and their effect upon the +horse, and having noted them, voluntarily reduced their extent and +utilized them in the training process. But here also there is much that +militates against this assumption when we consider how great is the +difficulty of consciously refining movements which at first were rather +coarse, unless it be by the adjustment of the proper degree of +concentration of attention, a subtlety of method of which we could +hardly believed Mr. von Osten capable. We must remember, also, that in +the first publication regarding Hans which, by the way, marks the +beginning of his career, ("Das lesende und rechnende Pferd," by +Major-General E. Zobel, in the "Weltspiegel" of July 7, 1904), we may +read the following: "He (Mr. von Osten) is always willing to have the +horse undergo an examination on the part of a stranger, and promises +that after Hans has become fairly well acquainted he will display the +same degree of efficiency as he displays with the master, himself." +This occurred at a time when Mr. Schillings, the man who was destined to +prove the truth of the statement, had not yet appeared on the scene. How +was Mr. von Osten to know beforehand that every questioner, who might +appear, would execute the same movements that he himself had used? We +would recall also that not one in the great multitude of persons who +worked successfully with the horse in the absence of Mr. von Osten, had +noticed, even in the slightest measure, any of these movements in +themselves. The position and repute of these persons vouches for their +veracity,--among them were the writer of the article just mentioned, the +Count zu Castell, Count Matuschka, Count von Eickstedt-Peterswaldt, +General Koering, Dr. Sander, Mr. H. Suermondt and Mr. H. von +Tepper-Laski. Some of these gentlemen were quite unwilling to believe +that they executed such movements. This happened in the case of Mr. von +Tepper-Laski, who had visited Hans ten times and who had, during the +course of these visits, frequently worked alone with the horse and had +received correct responses. Count Eickstedt, too, although he was one of +those who had been made acquainted with the nature of the movements +involved before being allowed to visit the horse, was unable to note +them either in his observation of Mr. von Osten, or of himself, when, in +compliance with his own wish, he was left alone with Hans. Nor did any +of the laboratory subjects, some of whom were well trained in +introspection, discover the true nature of affairs. They were thoroughly +astonished when the facts of the case were explained to them. And I, +also, as was mentioned on page 100, did not become aware of my own +movements, until I had noted those of Mr. von Osten. In fine, everything +would indicate that we have here not an intention to deceive the +public, but a case of pure self-deception.[AO] + + [Footnote AN: There is only one, and I believe it is only a seeming + exception to be found in the literature on the subject. We are told + that about the year 1840 a French revenue official named Leonard had + two hunting dogs that, besides other things, were able to play at + dominoes, and this not only with their master, but with anyone and + without the master's assistance. The owner had educated them simply + for the fun of it, and not for pecuniary gain. This statement is + made by both writers who, apparently independently of one another, + have discussed the case, Youatt[108] and de Tarade.[109] De Tarade + himself played with them, and gives directions how to teach dogs to + play the game. But his exposition is so naive, and even ridiculous, + for those who know anything about the subject, that we do not + believe it necessary to attempt a detailed refutation. Youatt never + saw the animals. But he tells us that not only the dog's partner, + but also the master, sat at the game. Youatt's assertion, however, + that "not the slightest intimation could have been given by Mr. + Leonard to the dog," but that the animal carried on the game by + means of its own observation and calculation, appears to me a rather + bold statement. After my own experience with dogs, I firmly believe + this to have been impossible. Hachet-Souplet,[110] who shares my + conviction, explains the matter as follows: the dog would simply + place a domino having the number of eyes named by his partner, thus + the 6 adjacent to the 6, the 3 to the 3, etc. But even so a great + deal would have to be attributed to the dog, (although in that case + real counting would by no means be absolutely necessary, for an + association between the number term and the total picture of the + corresponding group of eyes would suffice.) But we must note that + neither of the writers mentions that the numbers were always called + aloud by the partner. After the failure of the experiments of Sir + John Lubbock,[111] we must doubt very much if a dog is able to match + one domino with another having the same number of eyes. We are + therefore inclined to believe that this dog continually received + signs from its master. These signs probably were visual, perhaps + also auditory, and they were by no means involuntary. For in a book + on the training of animals, which Leonard, the owner of the dogs, + has published, and in which he describes minutely the method by + which they had been trained in their various accomplishments, he + does not mention with so much as a syllable the game of dominoes, a + thing which he certainly would have dwelt upon, if he had believed + in the animals' power of independent thought. He would not have + remained silent concerning this greatest--though only + apparent--achievement of his educational endeavors. But his whole + book is evidence that he was too wise to have thus deceived himself, + and our only alternative is to believe that he was playing a joke on + his credulous admirers.] + + [Footnote AO: P. Wasmann, S. J. in the third edition of his book, + "Instinkt und Intelligenz im Tierreich" (Freiburg, Herder, 1905), + discusses the case of Hans and quotes from a letter I wrote him + concerning the matter. In the quotation an error has crept in, which + I would here correct. The statement is ascribed to me that "Hans + differs from other horses only in his extraordinary power of + observation, an unintentional by-product of intentional training," + whereas in my letter I said: "unintentional by-product of + intentional education."] + +This self-deception is easily understood when we consider the two +predominent characteristics of the man: the pedantry of the pedagogue, +and his proneness to be possessed by a single idea, which is a +peculiarity of those of an inventive turn of mind. Adhering closely to a +preformed plan, he carefully and narrowly circumscribed the scope and +order of instruction. He would not go on to the number 5 if he were not +thoroughly convinced that the 4 had been completely mastered, nor would +he go on to a more difficult problem in multiplication, until he felt +certain that Hans was entirely proficient in the problems of the simpler +sort. If he had ever put a question to Hans before its regular order, he +would have discovered, to his amazement, that there really existed no +difficulties for Hans, and also that the horse really required no +appreciable time to acquire new material. Mr. von Osten would have had a +like experience if he had asked Hans concerning the value of Chinese +coins or the logarithm of 1000. However, he never did anything of the +kind, but always adhered closely to his plan. He required the questioner +to say: "2 and 2", and never "2 plus 2". Nor were capitals or Latin +script to be used in the written material. And if upon request he did +so, he did it, without faith in the result, and hence there was +failure. And so he declared that "if you use Latin script Hans becomes +confused and will be out of sorts for several weeks thereafter." Mr. von +Osten is, and ever will remain, the schoolmaster, and will never become +the psychologist, the "soul-vivisectionist". Who would work a child with +such puzzling questions? and Hans was to him like a child. Thus the old +man believed himself to be a witness of a continuous, organic +development of the animal soul--a development which in reality had no +other existence than in his own imagination. + +Added to this pedantry was an extraordinary uncritical attitude of mind, +induced by his obsession by one favorite idea, which blinded him to all +objections. He met objectionable observations on the part of others in +one of two ways. One method was by attributing to Hans certain +remarkable qualities, such as an extraordinary keenness of hearing and a +wonderful power of memory, or again, certain defects, such as moodiness +and stubbornness,--which as a matter of fact, were only so many +back-doors by which he might escape from the necessity of offering +adequate explanations. When Hans was able to give off-hand a gentleman's +name which he had heard years before, it was called a case of +extraordinary memory. When the horse insisted that 2 times 2 was 5, he +maintained that it was an example of animal stubbornness. There was +still a simpler method of overcoming inconvenient objections and that +was by ignoring them altogether. The number 1, the simplest and most +fundamental in the system of numbers, was one of the most difficult for +Hans. (Page 67f.). Mr. von Osten was aware of this, but thought little +of it. During the very first visit of Professor Stumpf, Mr. von Osten +asked the horse: "By how much must you increase the numerator of the +fraction 7/8, in order to get a whole number?" Hans repeatedly answered +incorrectly and always tapped numbers that were too great. The same +question was then asked concerning the fraction 5/8, and immediately +there was a correct response, (the favorite number 3). Mr. von Osten +said very naively: "In the case of the difference of 1, he always goes +wrong. It was just what I expected." Mr. von Osten still relates that +the distinction between right and left created far greater difficulty +for Hans than all of the work in fractions, and that even to-day it is +not thoroughly established; also, that the selection of colored cloths +is often a failure still, although it was one of the first things in +which he was given instruction. It appears never to have dawned upon Mr. +von Osten that the arts in which Hans seemed to excel, also formed the +standing repertoire of so many trained horses, regarding whom it was +well-known that they owed all of their cleverness to the training given +them by their masters. This fact alone should have induced him to make +some form of critical investigation. + +When Hans suddenly became a celebrity, and he, himself, the object of an +enthusiastic following, the whole affair evidently took Mr. von Osten +off his feet. Strangers took the further instruction of the horse in +charge, and the rate and degree of Hans's progress became disconcerting. +One day it came to pass that the horse even understood French, and the +old gentleman, whose apostolic exterior had always exerted a high degree +of suggestion upon his admirers, in turn fell captive to the spell of +retroactive mass-suggestion. He no longer was uneasy concerning the most +glaring kinds of failure. On one occasion he even insisted upon the +completion of a series of tests in which procedure was "without +knowledge", which promised no results whatever. "The animal's +stubbornness must be broken," he commented. On the other hand, he +regarded every criticism as a form of personal insult. And once he +showed a member of the committee of the Society for the Protection of +Animals the door, because the man, without having looked at his watch, +wanted to show it to Hans and ask him the time. Many other critics had +similar experiences. + +Summarizing the remarks of this chapter, our judgment must be as +follows: It is in the highest degree improbable that Mr. von Osten +purposely trained the horse to respond to certain cues. It is also +improbable that he knew that in every test he was giving signals, +(although I can form no judgment concerning what happened after the +publication of the latest report). To assume the contrary would land us +in the midst of insoluble contradictions of the many ascertained facts +in the case. The explanation here essayed, however, should prevent that. +To be sure, we, must then reckon with curious inner contradictions in +Mr. von Osten's character. But such contradictions are to be found, upon +earnest analysis, in nearly every human character. And Mr. von Osten may +say with the poet: "Ich bin kein ausgekluegelt Buch. Ich bin ein Mensch +mit seinem Widerspruch." + + + + +CONCLUSION + + +If we would make a brief summary of the status of Mr. von Osten's horse +in the light of these investigations and try to understand what is the +bearing upon the question of animal psychology in general, we may make +the following statements. + +Hans's accomplishments are founded first upon a one-sided development of +the power of perceiving the slightest movements of the questioner, +secondly upon the intense and continued, but equally one-sided, power of +attention, and lastly upon a rather limited memory, by means of which +the animal is able to associate perceptions of movement with a small +number of movements of its own which have become thoroughly habitual. + +The horse's ability to perceive movements greatly exceeds that of the +average man. This superiority is probably due to a different +constitution of the retina, and perhaps also of the brain. + +Only a diminishingly small number of auditory stimuli are involved. + +All conclusions with regard to the presence of emotional reactions, such +as stubbornness, etc., have been shown to be without warrant. With +regard to the emotional life we are justified in concluding from the +behavior of the horse, that the desire for food is the only effective +spring to action. + +The gradual formation of the associations mentioned above, between the +perception of movement and the movements of the horse himself, is in all +probability not to be regarded as the result of a training-process, but +as an unintentional by-product of an unsuccessful attempt at real +education, which, though in no sense a training-process, still produced +results equivalent to those of such a process. + +All higher psychic processes which find expression in the horse's +behavior, are those of the questioner. His relationship to the horse is +brought about almost wholly by involuntary movements of the most minute +kind. The interrelation existing between ideas having a high degree of +affective coloring and the musculature of the body, (which is brought to +light in this process), is by no means a novel fact for us. +Nevertheless, it is possible that this case may be of no small value, on +account of the great difficulties which are usually met in the attempt +to establish experimentally the more delicate details in this field. + +And, returning to the considerations of the first chapter, if we ask +what contributions does this case make toward a solution of the problem +of animal consciousness, we may state the following: The proof which was +expected by so many, that animals possess the power of thought, was not +furnished by Hans. He has served to weaken, rather than strengthen, the +position of these enthusiasts. But we must generalize this negative +conclusion of ours with care,--for Hans cannot without further +qualification be regarded as normal. Hans is a domesticated animal. It +is possible (though the opposite is usually assumed), that our animals +have suffered in the development of their mental life, as a result of +the process of domestication. To be sure, in some respects they have +become more specialized than their wild kin, (e. g., our hunting dogs), +and in their habits they have become adapted largely to suit our needs. +This latter is shown by all the anecdotes concerning "clever" dogs, +horses, etc. But with the loss of their freedom they have also gradually +been deprived of the urgent need of self-preservation and of the +preservation of their species, and thus lack one of the greatest forces +that make for psychic development. And often their artificial selection +and culture has been with a view to the development of muscle and sinew, +fat and wool, all at the expense of brain development.[AP] Our horses +are, as a rule, sentenced to an especially dull mode of life. Chained in +stalls (and usually dark stalls at that,) during three-fourths of their +lives, and more than any other domestic animal, enslaved for thousands +of years by reins and whip, they have become estranged from their +natural impulses, and owing to continued confinement they may perhaps +have suffered even in their sensory life. A gregarious animal, yet kept +constantly in isolation, intended by nature to range over vast areas, +yet confined to his narrow courtyard, and deprived of opportunity for +sexual activity,--he has been forced by a process of education to +develop along lines quite opposite to his native characteristics. +Nevertheless, I believe that it is very doubtful if it would have been +possible by other methods, even, to call forth in the horse the ability +to think. Presumably, however, it might be possible, under conditions +and with methods of instruction more in accord with the life-needs of +the horse, to awaken in a fuller measure those mental activities which +would be called into play to meet those needs. + + [Footnote AP: Buffon,[124] the great naturalist, expresses himself + not less pessimistically in his own brilliant manner: "Un animal + domestique est un esclave dont on s'amuse, dont on se sert, dont on + abuse, qu'on altere, qu'on depaise et que l'on denature."] + +Though our investigations do not give support to the fantastic accounts +of animal intelligence given by Brehms, they by no means warrant a +return to Descartes and his theory of the animal-machine (as is +advocated by a number of over-critical investigators). We cannot deny +the validity of conclusions from analogy without denying at the same +time the possibility of an animal psychology--indeed of all psychology. +And all such conclusions indicate that the lower forms possess the power +of sense-perception, that they, like us, presumably have at their +disposal certain images, and that their psychic life is to a large +extent also constituted of mere image-associations, and that they too, +learn by experience. Also that they are susceptible to feelings of +pleasure and of pain and also to emotions, as jealousy, fear, etc., +though these may be only of the kind which have a direct relation to +their life-needs. We are in no position to deny _a priori_ the +possibility of traces of conceptual thought in those forms nearest man +in the scale--whether living in their natural manner or under artificial +conditions. And even less so since the final word has not yet been +spoken regarding the nature of conceptual thinking itself. All that is +certain is that nothing of the kind has been proven to occur in the +lower forms, and that as yet not even a suitable method of discovering +its existence has been suggested. But the community of those elementary +processes of mental life which we have mentioned above is in itself +enough to connect the life of the lower forms with ours, and imposes +upon us the duty of regarding them not as objects for exploitation and +mistreatment, but as worthy of rational care and affection. + + + + +SUPPLEMENTS + + + + +SUPPLEMENT I + +MR. VON OSTEN'S METHOD OF INSTRUCTION + +[BY C. STUMPF] + + +The following is a report of the account, which Mr. von Osten gave +Professor Schumann and me, of the method which he had used in the +instruction of the horse, and which was illustrated by actual +demonstrations. I cannot testify, of course, that Mr. von Osten really +did adhere to this method throughout the four years in which he tutored +the horse, but I will say that I have several good reasons for believing +that it was impossible for him to have trumped up this make-believe +scheme afterward, merely to mislead us. Among the reasons are the +following: He was always ready to give a detailed explanation of any +question which we might interpose; the written statements of Major von +Keller, who has known Mr. von Osten for a period of fifteen years; the +testimony of General Zobel, who became acquainted with the whole process +fully a year before any public exhibitions were given; the accounts +given by the tenants in Mr. von Osten's house, who for years saw the +process of instruction going on in the courtyard of the apartment +building,--according to their account his intercourse with the horse +was like that with a child at school,--he made much use of the apparatus +and never did they notice anything like an habituation to respond to +certain signals; and finally the appearance of the apparatus +itself--some of which could not be bought at second hand--was most +convincing. + +The apparatus used for the work in arithmetic consisted mainly of a set +of large wooden pins, a set of smaller ones (such as are to be had in +toy-shops), a counting-machine, such as is commonly used in the schools, +a chart upon which were pasted the numbers from 1 to 100, and finally +the digits, cut large and in brass and suspended from a string. For the +work in reading Mr. von Osten used the chart shown in the frontispiece +of this book. Here we have the letters of the alphabet in small German +script with numbers written below which serve to indicate the row, and +what place in that row, the letters occupy. For tones, a small, child's +organ was used with the diatonic scale C^1 to C^2, and for instruction +in colors, a number of colored cloths were used. + +The work in arithmetic began by placing a single wooden pin in front of +Hans and then commanding him: "Raise the foot!--One!" Here we must +assume that the horse had learned to respond to the command to raise the +foot during the preceding period, when tapping in general had been +taught. In order to get the horse to learn that he was to give only one +tap, Mr. von Osten tried to control the tapping by means of holding the +animal's foot, just as a teacher tries to aid a pupil in learning to +write by guiding his hand. He repeated this exercise so often that +finally the single tap was made. And always the right foot was insisted +upon. Bread and carrots were the constant rewards. + +Two of the pins were now set up and the command given: "Raise the +foot!--One, two!" Mr. von Osten again aided the establishment of the +proper association by using his hand as before. At the same time the two +pins were pointed out, and the order was always without exception from +left to right. Gradually it became unnecessary to touch the foot or to +point to the pins, and instead the question was introduced: "How many +are there?", in order that the horse should become accustomed to these +words as an invitation to give the taps when he saw the wooden pins +before him. + +Then three pins were taken and the words "one, two, three" were spoken, +and so on. In naming a number the preceding ones were always named along +with it, in order that the normal order might thus be learned at the +same time. Later the number alone, without the preceding ones, sufficed +to elicit the proper number of taps. The last word of the series thus +becomes characteristic of the series as a whole. It differs from all the +others, and thus becomes the sign for the whole series of numbers thus +named, each of which arises as a memory image at the proper place in the +series and is accompanied by a tap of the foot. Thus, Mr. von Osten at +any rate had accounted to himself for his success. + +But Hans was not to acquire merely this relatively mechanical process of +counting (hardly to be called counting), but he was to acquire also some +meaning content for the number terms. For this purpose everything +depended upon the concept "and". Only he who can grasp its meaning will +be able to understand a number. 2 is 1 _and_ 1, 3 is 2 _and_ 1. Mr. von +Osten had someone hold a large cloth before the horse, where the wooden +pins usually were placed. He then had the cloth taken up and he would +pronounce emphatically the word "and". After this had been done a number +of times, he put up two of the pins and obscured them by the cloth. The +cloth was again raised and the word "and" pronounced. Then Hans, as a +result of his previous instruction (so Mr. von Osten thought) would give +two taps at sight of the pins. The thing was repeated with three pins, +then with one, and so on, and the horse would always execute the proper +number of taps. + +Now, five pins were set up, the three to the right being covered by the +cloth. The horse tapped twice and Mr. von Osten said "two". Then the +cloth was raised, Hans gave three further taps, and Mr. von Osten said +"and three" with emphasis. + +In this simple manner he tried to get the horse to understand that the +three belongs to the two, and that both together make five. The image of +the five pins as it was known from previous experience, was to be +associated with the combined groups of two and three, and conversely, it +was to be reproduced when these groups were presented. Later the cloth +and pins were omitted and the question was asked: "How much is two and +three?". The horse tapped five times. It had learned how to add. Still +this could be regarded only as a mechanical process, if the horse were +able to add only those numbers which had been presented together one or +more times in the manner just described. And so long as we remained +within the first decade, we could get twenty-five binary combinations +whose sum does not exceed 10 (counting inverted orders we would have +forty-five binary permutations),--all of which might have been practised +separately. But as a matter of fact, Mr. von Osten did not take this +course, for as he himself says, he allowed Hans to discover a great +deal for himself. "Hans had to develop the multiplication table for +himself."--With larger numbers and more addends, the number of +combinations becomes so great that there can be no doubt they were not +practised separately. + +Since, after all this preliminary instruction, Hans really began to give +solutions of new problems, the master believed that this was proof that +he had succeeded in inculcating the inner meaning of the number +concepts, and not merely an external association of memory images with +certain movement responses. But he always remained within the sphere of +the ideas thus developed, and adhered closely to the customary +vocabulary and its usage. Every new concept, each additional word was +explained anew. + +It would not be legitimate to condemn the whole procedure from the very +beginning on the ground of the horse's lack of knowledge of language or +of its use. It was Mr. von Osten's aim to convey to the horse an +understanding of the language, by means of sense-presentations, adequate +to give rise to the proper sense-perceptions. Helen Keller and other +blind deaf-mutes have been educated to an understanding of the language +without the aid of vision and hearing. They have come to it through the +sense of touch alone. Everything depends upon whether or not the +predisposition for it is present. And it was quite rational that Mr. von +Osten should have chosen counting and arithmetical calculation as the +processes by which to make his attack upon the animal mind, for as a +matter of fact, nowhere else is it so easy to bridge the gap between +perception and conception and nowhere else can the sign of success or +failure be perceived so readily as in the handling of numbers. It is +unfortunate, however, that he did not utilize these same signs for +purposes of counter-testing also, as, for instance, by inquiring for the +cube root of 729. But he was prevented from doing this by his close +adherence to his pedagogical principle and by his unquestioning faith in +the soundness of the entire procedure. + +In teaching multiplication the counting machine was used. Two of the ten +balls on one of the rods were pushed far to the left, thus: 00. "How +many are there?" Two taps. "Very well. That is once two." Another group +of two was pushed to the left, at a short interval from the first group, +thus: 00 00. "How many times two balls are there?" was asked, with a +decided movement of the hand toward the two groups. Two taps. "How many, +therefore, are two times two?" Four taps. + +The horse was supposed to learn the meaning of the word "times" by means +of the spatial separation of the groups; he was to be taught to notice +and to count the groups, and also the number of units in a single group. +Three times two then meant three groups with two units in each group. +The horse was supposedly aided by the following factors: the relative +nearness of the units belonging to one group, as over against the space +interval between the groups themselves; also that the groups were +pointed out as wholes in connection with the emphatic enunciation of the +words 'once, twice,' etc.; and finally the touching and raising of the +horse's foot by means of the hand until all the desired associations of +the ideas with one another and with the corresponding tapping movements +were quite perfect. + +Subtraction was taught in the following manner. Five pins were set up; +the horse tapped five times. Mr. von Osten then removed two of them and +said emphatically: "I take away,--minus. How many are still standing?" +The horse tapped three times. Here, too, there was at first some +assistance by means of the hand to get the tapping. + +In division four balls were first pushed to the left end of the rod, +thus: 0000. "How many balls are there to the left?" Four taps. They were +now divided into two pairs, thus: 00 00. Pointing to the units of one +group, the teacher asks: "There are always how many in the group?" Two +taps. Three groups were formed, thus: 00 00 00. "There are now how many +balls to the left?" Six taps. "And there are always how many in each +group?", (pointing at them). Two taps. "And how often is two contained +in six?", (pointing to the groups consecutively). Three taps, etc. + +The ideas of 'part', of 'whole', and of 'being contained' were +illustrated by means of a chalk line which was interrupted in one or +more places by erasure. + +In all these operations Mr. von Osten adhered strictly to the rule, and +required others to do so too, that the number upon which the operation +was performed, must be mentioned first. Thus, one was not to say, "take +3 away from 7", but "from 7 take away 3." Otherwise, he believed, Hans +would become easily confused. Also one was not allowed to say "to +multiply", but to "take" a certain number so many "times". He, himself, +never departed from this practice. + +We will not go into the details of the method by which Hans was taught +the meaning of the number signs, of the signs of operation, of the +numbers above 10, or the significance of "digits", "tens", etc. Only +this,--when in problems in addition the sum was greater than 10, the 10 +was first tapped and then the remainder of the number added to the 10. +Thus: "You are to add 9 and 5. How much must you add to the 9 to have +10?" One tap. "But now, you were to add not merely 1, but 5; how much +have you still to add to the 10?"--Four taps. In like manner, whenever +the addends were below 20 or 30 and the sum above 20 or 30, Mr. von +Osten would ask for the 20 or 30 taps first. He thought that he was thus +giving his pupil an ever firmer grasp upon the principle of the +structure of our number system, in which all higher numbers are +constituted of tens and digits. For the same reason he used at first, +instead of the words 'eleven' and 'twelve' ('elf' and 'zwoelf' in the +German), expressions which in English might be rendered as 'one-teen' +and 'two-teen' ('einzehn' and 'zweizehn' in the German); and only later, +after the animal had seemingly mastered the meaning in question, did Mr. +von Osten replace them by the usual forms. + +All this was beautifully conceived and might perhaps form the basis for +the instruction of primitive races. But it is of immediate interest for +us only because it enables us to better understand the origin of the +conviction under which Mr. von Osten and his followers labored. + + + + +SUPPLEMENT II + +THE REPORT OF SEPTEMBER 12, 1904 + + +"The undersigned came together for the purpose of investigating the +question whether or not there is involved in the feats of the horse of +Mr. von Osten anything of the nature of tricks, that is, intentional +influence or aid, on the part of the questioner. After a careful +investigation they are unanimously agreed that such signs are out of the +question under the conditions which were maintained during this +investigation. This decision in no wise takes into account the character +of the men exhibiting the horse, and who are known to most of the +undersigned: In spite of the most attentive observation, nothing in the +way of movements or other forms of expression which might have served as +a sign, could be discovered. In order to obviate involuntary movements +on the part of those present, one series of tests was made with only Mr. +Busch present. Among these tests were some in which, according to his +professional judgment, the possibility of tricks of the sort commonly +used in training, was excluded. Another series of tests was made in such +a way that the correct answers to the questions which Mr. von Osten put +to the horse, were unknown to the questioner. From previous observation +the greater number of the undersigned also know of a large number of +cases in which, during the absence of Mr. von Osten and Mr. Schillings, +other persons were likewise able to obtain correct responses from the +horse. Among these were some cases in which the questioner did not know +the correct solution of the problem or was mistaken about it. And +lastly, several of the undersigned have become acquainted with the +method which Mr. von Osten used, which has little in common with methods +of training, and is patterned after the instruction given in the +elementary schools. As a result of these observations the undersigned +are of the opinion that unintentional signs of the kind which are at +present familiar, are likewise excluded. They are unanimously agreed +that this much is certain: This is a case which appears in principle to +differ from any hitherto discovered, and has nothing in common with +training, in the usual sense of that word, and therefore is worthy of a +serious and incisive investigation. + +BERLIN, September 12, 1904. + + PAUL BUSCH, Circus-manager. + OTTO, COUNT ZU CASTELL-RUeDENHAUSEN. + DR. A. GRABOW, member of the schoolboard, retired. + ROBERT HAHN, Teacher, Municipal schools. + DR. LUDWIG HECK, Director of the Zooelogical Garden. + DR. OSCAR HEINROTH, Assistant in the Berlin Zooelogical Garden. + DR. RICHARD KANDT. + MAJOR F. W. VON KELLER, retired. + MAJOR-GENERAL TH. KOeRING, retired. + DR. MIESSNER, Assistant in the Royal Veterinary College. + PROF. NAGEL, Head of the department of sense-physiology in the + Physiological Institute of the University of Berlin. + PROF. C. STUMPF, Director of the Psychological Institute, Member of + the Academy of Sciences. + HENRY SUERMONDT." + + + + +SUPPLEMENT III + +AN ABSTRACT FROM THE RECORDS OF THE SEPTEMBER-COMMISSION[AQ] + + [Footnote AQ: A few days after the 12th of September I made the + present abstract from the original records of the Commission, which + I have here abbreviated somewhat. (See page 8). Referring once more + to the misunderstanding mentioned on page 3, I would say that the + closing sentence of the report is here re-given literally as it then + appeared. C. St.] + + +The important meetings occurred on the 11th and 12th of September and +both of them extended over four hours. The greatest difficulty was +occasioned by the condition laid down by Mr. von Osten: that we were to +work without him from the very beginning. In a certain sense this +condition had been met once before when Mr. Schillings appeared upon the +scene, a man whose fairness ought to be doubted by none. He came utterly +skeptical, and yet in the course of a week he learned to handle the +horse and received responses regularly. However, since the public had +begun to doubt Mr. Schillings also, another person had to attempt the +role of questioner. Count zu Castell tried to do this and practised for +some days before the meetings, but his success--although of no small +moment--was not great enough to be convincing. + +In apprising Mr. von Osten of this fact we caused a veritable +catastrophe. He declared in a most decisive manner that he would have to +insist upon the condition he had imposed, since the public demanded it, +and he could never assist in any tests, until he had been cleared of the +suspicion of having descended to the use of tricks. If it should take +weeks to accustom the horse to a new questioner, there would be no +alternative but to wait that length of time. + +A happy circumstance helped us out of our difficulty. We had chanced in +our discussion to mention the experience of Dr. Miessner, a member of +the commission, who on the day before had gone to witness an exhibition +of the mare "Clever Rosa", and who believed that he had succeeded in +discovering the tricks involved. There was a sudden change in Mr. von +Osten's attitude. He expressed his willingness to undergo the most +stringent examination and agreed to anything in the way of conditions of +control, challenging even the proven ability of Dr. Miessner. "I have +neither whip nor rod, as had the man in the exhibition, and agree to any +precautionary measures you may care to take." + +After he had gone, the commission decided to ask him to have the horse +perform one of the more common, simple, feats. They were going to watch +him very closely. Different members were assigned the task of attending +to different parts of his body (head, eyes, right hand, left hand, etc.) +while Mr. Busch, since he was the most proficient in the detection of +tricks, was to regard the total behavior of the man. + +The exhibitions included the indication of the day of the week by means +of taps, the day just past, the day ahead, its date, arithmetical +problems, and the counting of rings strung upon a rod. Messrs. Grabow +and Hahn interpolated a few tests themselves, in which they did the +questioning. All tests were successful. + +Mr. von Osten withdrew, and in comparison of notes which followed, Mr. +Busch, as well as all the others, declared that they had discovered +nothing of the nature of a visible sign. Mr. Busch said that he had also +kept an eye on the spectators and had noticed nothing there. +Nevertheless, he desired to see Mr. von Osten go through one series with +no one else but himself (Busch) present. + +This was done, and on this occasion a number of tests were made in the +recognition of colored cloths. The horse was required to indicate, by +tapping, the place in the series which the cloth occupied and was then +asked to bring the green or the red, as the case might be, in his mouth. +Furthermore, he was asked to approach that one of the five gentlemen +standing at a distance, whose photograph had been shown him. Then he was +requested to spell the words "Rat" and "Busch" according to the method +which he had been taught. Nearly all of these tests were likewise +successful. + +In the conference which followed, Mr. Busch again declared that he had +noticed no trace of a sign; he maintained that, in the selecting of +colored cloths (especially when they were placed so closely together) +and in the approach toward a person, there was no possibility whatever +that some trick was being used. + +During the session of September 12th, Mr. von Osten agreed to two sets +of experiments. + +1. Another man was to put the question to the horse. Mr. von Osten +himself was to stand, back to back to the questioner and to bend +forward, so that he was effectually hidden from the horse's view, yet +could, by means of occasional calls, make his presence known to the +animal. The assumption was that it would be conducive to success if the +horse knew that the master was present and was awaiting the answer, and +yet at the same time the possibility of receiving a sign was obviated. + +2. Another man in Mr. von Osten's absence was to ask the horse to tap a +certain number. Then the questioner was to leave, and Mr. von Osten, +returning, was to ask the horse to perform some arithmetical process +with the number which was thus unknown to the master. Mr. von Osten said +that he thought that this method was somewhat risky, since the horse +would be aware that he, Mr. von Osten, did not know the number, and +might therefore be in a humor to play some prank. + +The questions of the first sort were answered with but very few errors. +Mr. Hahn and Count zu Castell asked simple questions in arithmetic. When +Mr. von Osten withdrew into the stable, the count put several other +problems, among them the counting of persons and of windows, all of +which were solved correctly. + +Between the first and second series of tests the following experiments +were interpolated. The names of six members of the commission were +written upon six slates respectively, which were then suspended from a +string. Mr. von Osten pointed to one of the men and asked: "On which of +the slates is this gentleman's name to be found?" The correct number was +tapped in every case. The command to approach the slate in question was +also obeyed as a rule, although this was not as uniformly successful as +tapping. + +In the conference which followed, Mr. Busch declared that the feats +appeared inconceivable to him; and again none of the men had noted +anything in the way of signs. + +Now followed the second series of tests mentioned above. In order to be +sure to get the correct responses, Mr. Schillings, who up to this point +had not been present at any of the experiments, was asked to put the +questions to the horse. Mr. von Osten went into the house, accompanied +by a member of the commission. And again, Mr. Schillings would go out +before the second part of the test, without having met Mr. von Osten. + +Five tests were made in this way. They were not attended by such amazing +success as were the preceding ones, but nevertheless the results were +surprising. The horse nearly always repeated the number itself, instead +of performing the operation required. Since, however, Mr. Schillings, +owing to a misunderstanding, had, in the first two cases, said to the +horse: "You are to repeat this number for Mr. von Osten", the errors +might appear to be a result of this request. + +At the final discussion, the result of which was the unanimous +declaration which was given for publication, not only the data obtained +during these two sessions, but also the earlier experiences of some of +the members of the commission were taken into consideration. None of the +tests witnessed could be referred to chance or to the use of tricks. +Count zu Castell pointed out that in the course of eight days he had +elicited forty correct responses from the horse, among them some in +regard to which he himself had been momentarily in error. Other members +recalled the many instances in previous exhibitions, during which both +Mr. Schillings and Mr. von Osten were absent, when questions were put to +the horse by others. The commission also had access to a detailed +account written by Professor Stumpf on Mr. von Osten's method of +instruction, based on the explanations and demonstrations which Mr. von +Osten had himself given. As a result of these considerations the +commission felt under obligations to give public expression to its +conviction. In the report it limited itself, however, to the purely +negative side--principally in denying the use of tricks,--and expressed +no opinion with regard to the actual genesis of the horse's +accomplishments, since it believed that there was great possibility that +other factors were involved which ought to be carefully investigated. + + + + +SUPPLEMENT IV + +THE REPORT OF DECEMBER 9TH, 1904 + + +Together with Dr. E. von Hornbostel and Mr. O. Pfungst, I have tried +during the past few weeks to find an explanation of the accomplishments +of the horse 'Hans' by the experimental method. We had access to the +horse in the absence of the master and groom. The results are as +follows: + +The horse failed in his responses whenever the solution of the problem +that was given him was unknown to any of those present. For instance, +when a written number or the objects to be counted were placed before +the horse, but were invisible to everyone else, and especially to the +questioner, he failed to respond properly. Therefore he can neither +count, nor read, nor solve problems in arithmetic. + +The horse failed again whenever he was prevented by means of +sufficiently large blinders from seeing the persons, and especially the +questioner, to whom the solution was known. He therefore required some +sort of visual aid. + +These aids need not, however,--and this is the peculiarly interesting +feature in the case,--be given intentionally. The proof for this is +found in the fact that in the absence of Mr. von Osten the horse gave +correct replies to a large number of persons; and to be more specific, +Mr. Schillings and later Mr. Pfungst, after working with the horse for +a short time, regularly received correct answers, without their being in +any way conscious of having given any kind of signal. + +So far as I can see, the following explanation is the only one that will +comport with these facts. The horse must have learned, in the course of +the long period of problem-solving, to attend ever more closely, while +tapping, to the slight changes in bodily posture with which the master +unconsciously accompanied the steps in his own thought-processes, and to +use these as closing signals. The motive for this direction and +straining of attention was the regular reward in the form of carrots and +bread, which attended it. This unexpected kind of independent activity +and the certainty and precision of the perception of minimal movements +thus attained, are astounding in the highest degree. + +The movements which call forth the horse's reaction, are so extremely +slight in the case of Mr. von Osten, that it is easily comprehensible +how it was possible that they should escape the notice even of practised +observers. Mr. Pfungst, however, whose previous laboratory experience +had made him keen in the perception of visual stimuli of slightest +duration and extent, succeeded in recognizing in Mr. von Osten the +different kinds of movements which were the basis of the various +accomplishments of the horse. Furthermore, he succeeded in controlling +his own movements, (of which he had hitherto been unconscious), in the +presence of the horse, and finally became so proficient that he could +replace these unintentional movements by intentional ones. He can now +call forth at will all the various reactions of the horse by making the +proper kind of voluntary movements, without asking the relevant question +or giving any sort of command. But Mr. Pfungst meets with the same +success when he does not attend to the movements to be made, but rather +focuses, as intently as possible, upon the number desired, since in that +case the necessary movement occurs whether he wills it or not. In the +near future he will give a special detailed report of his observations, +which gives promise of becoming a valuable contribution to the study of +involuntary movements. Also he will give an account of our tests and of +the mechanism of the various accomplishments of the horse. We must also +defer, till then, the disproof of certain seemingly relevant arguments +in favor of the horse's power of independent thought. + +Some defenders of the view which maintains the horse's rationality may +urge that it was only through our experiments that the animal became +trained and spoiled in so far as the ability to think is concerned. They +are refuted in this, however, by the fact that the horse still continues +to solve problems involving decimal fractions and to determine calendar +dates for Mr. von Osten, as brilliantly as ever, as is shown by his +recent demonstration before a large group of spectators. That these +results are now being achieved in a manner essentially different from +formerly is nothing but a bare assertion. + +On the other hand, now that the possibility has been established that +these wonderful results may be obtained in all their complexity by means +of intentional signs, many will question whether Mr. von Osten did not +himself train the horse from the very beginning to respond to these +signs. No one has the right, however, to charge an old man, who has +never had a blemish on his reputation, with having invented a most +refined network of lies, if the facts can be explained in a +satisfactory manner in some other rational way. And this can be done in +this case. For we have seen that there is another alternative, other +than the theory that the horse can think or the assumption that tricks +have been employed. + +And now, aside from the specific results obtained, what is the +scientific and philosophic import of the whole affair?--For one thing, +the revolution in our conception of the animal mind, which had been +hoped for by some, and feared by others, has not taken place. But a +conclusion of an opposite character is justified. If such unexampled +patience and high pedagogical excellence as was daily brought to bear by +Mr. von Osten during the course of four long years, could not bring to +light the slightest trace of conceptual thinking, then the old assertion +of the philosophers that the lower forms are incapable of such thinking, +finds corroboration in the results of these experiments so far as the +animal scale up to and including the ungulates is concerned. For this +reason the tremendous effort put forth by Mr. von Osten, is not, in +spite of the self-deception under which he labors, lost to science. If +anyone has the courage to try the experiment with the dog or the ape, +the insight which we have now gained will enable him to beware of one +source of error which hitherto has not been noticed. + +In the face of much misapprehension which has arisen, I wish once more +to say emphatically that the committee of September 12th in no wise +declared itself to be convinced that the horse had the power of rational +thinking. The committee restricted itself entirely to the question +whether or not tricks were involved, and, intentionally and rightly +referred the positive investigation to a purely scientific court. I +would also report that for some time Mr. Schillings has been convinced, +by his own observations, of the horse's lack of reason, and when he was +apprised of our conclusion in the matter, he embraced it without +wavering. I have no intention of taking part in any discussion which may +arise in the press as a result of the present report. Unless they wish +to confine themselves to mere guesswork, the defenders of other views +will not shrink from the task of basing their criticism upon careful +methodical experimentation, and they will keep a detailed record of +their results day by day; for statements based solely upon memory, +without specific report of experimental conditions, prove nothing. + +PROF. CARL STUMPF. + +December 9th, 1904. + + + + +TABLE OF REFERENCES + + +(The names of the authors of anonymous works are placed in parenthesis.) + +1. ZELL, TH. Das rechnende Pferd. Ein Gutachten ueber den "Klugen Hans" +auf Grund eigener Beobachtungen. Berlin, R. Dietze, 1904. + +2. FREUND, F. Der "kluge" Hans? Ein Beitrag zur Aufklaerung. Berlin, Boll +and Pickardt, 1904. + +3. HANSEN, F. C. C. and A. Lehmann. Ueber unwillkuerliches Fluestern. +Philosophische Studien, edited by W. 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Vergleichend histologische Untersuchungen ueber die Retina +und die Area centralis retinae der Haussaeugetiere. Archiv fur Anatomie +und Physiologie, Anatomische Abteilung, Leipsic, 1902, Supplementary +volume, pp. 116 ff. + +43. HIRSCHBERG, J. Zur vergleichenden Ophthalmoskopie. Archiv fur +Anatomie und Physiologie, Physiologische Abteilung, Leipsic, Jahrg. +1882, p. 96. + +44. BERLIN, R., see 39, p. 4. + +45. THE SAME. Ueber den physikalisch-optischen Bau des Pferdeauges. +Zeitschrift fur vergleichende Augenheilkunde, Leipsic, 1882, Jahrg. +1, Heft 1, p. 32. + +46. BAYER, J. Tieraerztliche Augenheilkunde. Vol. 5 of the "Handbuch der +Tieraerztlichen Chirurgie und Geburtshilfe" by J. Bayer und E. Froehner. +Vienna und Leipsic, W. Braumueller, 1900, p. 459. + +47. THE SAME. Ditto, p. 475. + +48. RIEGEL, see 37, p. 35. + +48a. SCHWENDIMANN, F. Untersuchungen ueber den Zustand der Augen +bei scheuen Pferden. Archiv fuer wissentschaftliche und praktische +Tierheilkunde, Berlin, 1903, Bd. 29, Heft 6, p. 566. + +48b. BERLIN, R. Refraktion und Refraktionsanomalien von Tieraugen. +Tageblatt der 52. Versammulung deutscher Naturforscher und Aerzte in +Baden-Baden, 1879, p. 348. See also 45, pp. 28 f. and 39, p. 13. + +49. THE SAME, see 39, p. 9. + +50. BAYER, J., see 46, pp. 460 f. + +51. ZUeRN, J., see 42, p. 114. + +52. CHIEVITZ, J. H. Ueber das Vorkommen der Area centralis retinae in den +vier hoeheren Wirbeltierklassen. Archiv fuer Anatomie und Physiologie, +Anatomische Abteilung, Leipsic, 1891, Heft 4-6. p. 329. + +53. ZUeRN, J., see 42, p. 140. + +54. KOeNIGSHOeFER, see 41, pp. 251 ff. + +55. TENNECKER, S. V. Bemerkungen und Erfahrungen ueber den Charakter +und das Temperament, sowie ueber die geistigen Eigenschaften des Pferdes +ueberhaupt. Beitraege zur Natur- und Heilkunde, von Friedreich und +Hesselbach, Wuerzburg, 1825, Vol. 1, pp. 110 f. + +56. ZBORZILL, E. Die mnemonische Dressur des Hundes. Berlin, S. Mode +(1865), p. 21. + +57. MUeLLER, AD. und K. Tiere der Heimat. 3rd Edition, Cassel, Th. +Fischer, 1897, Book 1, p. 70. + +58. HUTCHINSON, W. N. Dog Breaking. 6th Edition, London, J. Murray, +1876, pp. 105 f. + +59. HUGGINS, LADY M. Kepler: a Biography. Cited by Sir J. Lubbock, On +the Senses, Instincts, and Intelligence of Animals. London, Kegan Paul, +Trench and Co., 1888, pp. 284 f. (The original was published privately +and never put on the market. Hence it was not accessible for me.) + +60. LUBBOCK, SIR J. Ditto, p. 285. + +61. ROUHET, G. L'entrainement complet et experimental de l'homme avec +etude sur la voix articulee, suivi de recherches physiologiques et +pratiques sur le cheval. Paris, Libraires associes, and Bordeaux, Feret +et fils, 1902, pp. 517 ff. + +62. LIPPS, TH. Zur Psychologie der Suggestion. Leipsic, J. A. Barth, +1897, pp. 5 f. + +63. ZELL, TH. See 1, pp. 40 f. + +64. ZBORZILL, E. See 56, p. 23. + +65. BEARD, G. M. Physiology of Mind-Reading. Popular Science Monthly, +New York, February 1877. Vol. 10, p. 472. Reprint in the Journal of +Science, and Annals of Astronomy, Biology, Geology, etc., London, 1881, +Series 3, Vol. 3, p. 418. + +66. BABINET. Les tables tournantes au point de vue de la mecanique et de +la physiologie. Revue des deux mondes, Paris, 1854, Twenty-fourth year, +Vol. 5, pp. 409 f. + +67. TOLSTOI, L. N. Anna Karenina. + +68. GOLDBECK. Besitzen die Tiere, speziell Hunde, Verstand oder nicht? +Deutsche tieraerztliche Wochenschrift, Hannover, 1902, Jahrg. 10, No. 20, +p. 202. + +69. MENAULT, E. L'intelligence des animaux. 4th Edition, Paris, Hachette +et Cie., 1872, p. 233. + +70. LEBON, G. L'equitation actuelle et ses principes. 3rd Edition, +Paris, Firmin-Didot et Cie., 1895, pp. 120 and 288. + +71. LOISET, B. Praktischer Unterricht in Kunstdarstellungen mit Pferden. +New edition. Stuttgart, Schickhardt u. Ebner, 1884, pp. 69 f. and 98 ff. + +72. BAUCHER, F. Dictionnaire raisonne d'equitation. 2nd Edition, Paris, +chez l'auteur, 1851, pp. 291 ff. + +73. ARNIM, V. Praktische Anleitung zur Bearbeitung des Pferdes an der +Longe. 2nd Edition, Leipsic, Zuckschwerdt und Co., 1896, pp. 18 f. and +39 f. + +74. MEEHAN, J. The Berlin "Thinking" Horse. Nature, London. 1904, Vol. +70, No. 1825, p. 602. + +75. SPOHR. Die Logik in der Reitkunst. Part 2. Pamphlet No. 32 in the +Series: "Unsere Pferde." Stuttgart, Schickhardt und Ebner, 1904, p. 29 +f. + +76. REDDING, T. B. The Intelligence of a Horse. Science, New York, 1892, +Vol. 20, No. 500, pp. 133 f. + +77. SPOHR. Die naturgemaesze Gesundheitspflege der Pferde. 4th Edition, +Hannover, Schmorl u. v. Seefeld Nachf., 1904, p. 164. + +78. DECROIX, E. Projet de langage phonetique universel pour la conduite +des animaux. Bulletin de la Societe nationale d'Acclimatation de France, +Paris, 1898, Forty-fourth Year, pp. 241 ff. + +79. NOIZET, GENERAL. Etudes philosophiques. Paris, H. Plon, 1864, Vol. +1, pp. 471 ff. + +80. BEARD, G. M. See 65, Vol. 10, p. 471. + +81. LEBON, G. See 70, p. 120. + +82. FLUeGEL, O. Das Seelenleben der Tiere. 3rd Edition, Langensalza, H. +Beyer und Soehne, 1897, pp. 50 f. + +83. LANDOIS, H. Ueber das musikalische Gehoer der Pferde. Zeitshrift fuer +Veterinaerkunde, Berlin, 1889, Jahrg. 1, No. 6. pp. 237 ff. + +84. FOVEAU DE COURMELLES. Les facultes mentales des animaux, Paris, J. +B. Bailliere et fils, 1890, p. 142. + +85. ZUeRN, F. A. Die intellektuellen Eigenschaften (Geist und Seele) der +Pferde. Pamphlet 8 of the Series: "Unsere Pferde." Stuttgart, +Schickhardt und Ebner, 1899, p. 26. + +86. FILLIS, J. Tagebuch der Dressur. Translated from the French by J. +Halperson and G. Goebel. Stuttgart, Schickhardt und Ebner, 1906, pp. +322 f. + +87. ATHENAEUS. Dipnosophistae. Book 12, 520 c. Edited by G. Kaibel. +Leipsic, B. G. Teubner, 1890, Vol. 3, pp. 148 f. + +88. AELIANUS, CL. De natura animalium. Book 16, 23. Edited by R. +Hercher. Leipsic, B. G. Teubner, 1864, Vol. 1, p. 401. + +89. JULIUS AFRICANUS, S. [Greek: Kestohi], chapter 14. In: Veterum +Mathematicorum Opera. Paris, Typographia Regia, 1693, P. 293. + +90. GUENON, A. Influence de la musique sur les animaux et en particulier +sur le cheval. (Chalons-sur-Marne), 1898, pp. 83 ff. + +91. LEPINAY. L'hypnotisme chez le cheval. Revue de l'hypnotisme, Paris, +1903, Eighteenth Year, No. 5, pp. 152 f. + +92. FILLIS, J. Grundsaetze der Dressur und Reitkunst. Translated from the +French by G. Goebel. 3rd Edition, Stuttgart, Schickhardt und Ebner, +1905, pp. 10 f. + +93. MANOUVRIER, L. Mouvements divers et sueur palmaire consecutifs a des +images mentales. Revue philosophique, Paris, 1886, Vol. 22, pp. 204 ff. + +94. GASPARIN, CTE A. DE. Des tables tournantes, du surnaturel en general +et des esprits. 2nd Edition, Paris, E. Dentu, 1855, Vol. 1, Part 1. + +95. RIVERS, W. H. R. and E. KRAEPELIN. Ueber Ermuedung and Erholung. +Psychologische Arbeiten, edited by E. Kraepelin, Leipsic, 1895, Vol. 1, +pp. 636f. + +96. (CARPENTER, W. B.). Spiritualism and its Recent Converts. Quarterly +Review, London, 1871, Vol. 131, No. 262, p. 312. + +97. DARWIN, CHAS. See 7, p. 48. + +98. SAINT-ANGE, DE. Cours d'hippologie. 2nd Edition, Paris, chez Dumaine +et chez Leneveu and Saumur, chez Mlle. Niverlet et chez Mlle. Dubosse, +1854, Vol. 1, p. 101. + +99. FRANZIUS, G. Die Wuenschelrute. Zentralblatt der Bauverwaltung, +Berlin, 1905, Jahrg. 25, No. 74, pp. 461 f. + +100. MENESTRIER, CL. FR. La philosophie des images enigmatiques. Lyon, +J. Guerrier, 1694, pp. 483 f. + +101. (LEBRUN, P.). Histoire critique des pratiques superstitieuses, qui +ont seduit les peuples et embarasse les scavans. Paris (et Amsterdam), +1702, p. 42. + +102. AGRICOLA, G. De re metallica libri XII, eiusdem de animantibus +subterraneis liber. Basel, Froben, 1556, Book 2, pp. 27 f. + +103. SCHOTT, C. Magia universalis naturae et artis. Wuerzburg, J. G. +Schoenwetters Erben, 1659, Part 4, Book 4, p. 430. + +104. THE SAME. Physica curiosa, sive mirabilia naturae et artis. +Wuerzburg, 1662, Part 2, Book 12, p. 1532. + +105. ZEIDLER, J. G. Pantomysterium, oder das Neue vom Jahre in der +Wuenschelruthe, etc. Hall in Magdeburg (Halle a. S.), Renger, 1700, +Chap. 2. p. 47. + +106. BARRETT, W. F. On the so-called Divining Rod, or Virgula Divina. +Proceedings of the Society for Psychical Research, London, 1897, Vol. +13, pp. 177 f. + +107. THEOPHANES. Chronographia. Paris, Typographia Regia, 1655, pp. +189 f. + +108. YOUATT, W. The Dog. London, Ch. Knight and Co., 1845, pp. 108 ff. + +109. TARADE, E. DE. Traite de l'elevage et de l'education du chien. +Paris, E. Lacroix (1866), pp. 113 ff. + +110. HACHET-SOUPLET, P. Die Dressur der Tiere. Translated from the +French by O. Marschall v. Bieberstein, Leipsic, O. Klemm, 1898, pp. +36 f. + +111. LUBBOCK, SIR J. See 59, pp. 280 f. + +112. LEONARD, A. Essai sur l'education des animaux, le chien pris pour +type. Lille, Leleux, 1842, pp. 81-185. + +113. MEEHAN, J. See 74, p. 602. + +114. FRANCONI (GAeRTNER). Die Dressur der Kunstpferde. Jahrbuch fur +Pferdezucht, Pferdekenntnis, Pferdehandel usw. auf das Jahr 1835, Weimar +und Ilmenau, 1835, Jahrg. 11, p. 329. + +115. LOISET, B. See 71, p. 130. + +116. HACHET-SOUPLET, P. See 110, p. 91. + +117. KNICKENBERG, F. Der Hund und sein "Verstand." Coethen (Anhalt), P. +Schettlers Erben, 1905, pp. 129 f. + +118. LANG, R. Geheimnisse zur kuenstlichen Abrichtung der Hunde, revised +edition. Augsburg and Leipsic, A. Baeumer, pp. 46 f. + +119. FRANCONI (GAeRTNER). See 114, pp. 326 f. + +120. TENNECKER, S. V. Erinnerungen aus meinem Leben. Altona, I. F. +Hammerich, 1838, Vol. 1, pp. 21 f. (The name of the author is +erroneously given on the title page as F. v. Tennecker.) + +121. LOISET, B. See 71, p. 132. + +122. D----. Ueber die Abrichtung der kleinen Kunstpferde zu dem Zaehlen +mit dem Fusse, Kopfschuetteln und dgl. Zeitung fuer die Pferdezucht, den +Pferdehandel, die Pferdekenntnis usw., Tuebingen, 1804, Vol. 4, p. 51. + +123. LANG, R. See 118, pp. 52 f. + +124. BUFFON, CTE DE, et L. DAUBENTON. Histoire naturelle, generale et +particuliere. Paris, Imprimerie royale, 1753, Vol. 4, p. 169. + + + + +Angell's Text-book of General Psychology. + +New Edition. By JAMES ROWLAND ANGELL, Professor and Head of the +Department of Psychology in the University of Chicago. Fourth Edition, +Revised and Enlarged. ix+468 pp. 8vo. $1.60. + +The fourth edition contains a large amount of new material, chiefly +empirical in character. To offset this addition, many of the more +strictly theoretical discussions have been condensed. The old material +has been rearranged and many new drawings have been supplied. + +CHARLES H. JUDD, University of Chicago:--I regard it as a most excellent +text. Its clear and thoroly interesting style will, I am sure, make it +very attractive to students. It is complete and compact. Indeed it is a +capital presentation of modern psychology. + + +Seashore's Elementary Experiments in Psychology. + +By CARL EMIL SEASHORE, Head of the Department of Philosophy and +Psychology in the State University of Iowa. ix+281 pp. 12mo. $1.00. + +A supplement to a regular text-book in elementary psychology. It +provides experiments for one laboratory period a week for one semester. + +FRANK DREW, State Normal School, Worcester, Mass.:--The range of +experiments and the simplicity of their presentation are admirable. +They will deepen insight. + + +Jones's Logic, Inductive and Deductive. + +By ADAM L. JONES, Professor in Columbia University. ix+304 pp. 12mo. +$1.00. + +The aim of this text-book is to present, in as concrete a form as is +possible, the rudiments of Logic, considered as method. + + +Jastrow's Psychology of Stereoscopic Vision. + +By JOSEPH JASTROW, Professor in the University of Wisconsin. [_In +press._] + + +Bode's Logic. + +By W. H. BODE, Professor in the University of Illinois. $1.00. + + + HENRY HOLT AND COMPANY + NEW YORK + + + + +LATEST VOLUMES IN THE AMERICAN NATURE SERIES + +(Prospectus of entire Series on request) + + +INSECTS AND DISEASE + +By R. W. DOANE, of Stanford University. 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SALISBURY, + Professors in the University of Chicago. + + Physiography. + By ROLLIN D. SALISBURY, Professor in the University of Chicago. + + General Biology. + By WILLIAM T. SEDGWICK, Professor in the Mass. Institute, + and EDMUND B. WILSON, Professor in Columbia University. + + Botany. + By CHARLES E. BESSEY, Professor in the University of Nebraska. + + Zoology. + By A. S. PACKARD, Professor in Brown University. + + The Human Body. + By H. NEWELL MARTIN. + + Psychology. + By WILLIAM JAMES, Professor in Harvard University. + + Ethics. + By JOHN DEWEY, Professor in Columbia University and + JAMES H. TUFTS, Professor in the University of Chicago. + + Political Economy. + By FRANCIS A. WALKER. + + Finance. + By HENRY C. ADAMS, Professor in the University of Michigan. + + +For full descriptions of the Advanced, Briefer, and Elementary Courses +published under each topic, see the publishers' Educational Catalog. + + + HENRY HOLT & CO. + 34 West 33d Street, N. Y. + 378 Wabash Ave., Chicago + + + + +Transcriber's Notes + + +Illustrations have been moved near the relevant section of the text. + +Inconsistent use of spacing has been retained for page numbers followed +by "f" or "ff", and for "i.e." / "i. e.", "e.g." / "e. g.", and +"c.f." / "c. f." Inconsistent use of commas following "i.e.", "e.g.", +and "c.f." has also been retained. Inconsistent use of single and +double quotes around words and the placing of punctuation either +within or external to quotes has been left as-is. Capitalization +inconsistencies and grammatical errors relating to subject/verb +agreement were also retained. + +Inconsistent hyphenation, accents, and use of separate words have been +retained for "any one" / "anyone", "arm movement" / "arm-movement", +"backstep" / "back-step", "blind spot" / "blind-spot", "by the way" / +"by-the-way", "counting machine" / "counting-machine", "divining rod" / +"divining-rod", "ear movements" / "ear-movements", "eye movement(s)" / +"eye-movement(s)", "eyebrows" / "eye-brows", "first rank" / "first-rank", +"four fifths" / "four-fifths", "Hans problem" / "Hans-problem", "head +jerk" / "head-jerk", "head movement(s)" / "head-movement(s)", +"hoped for" / "hoped-for", "memory images" / "memory-images", +"movement impulse" / "movement-impulse", "movement responses" / +"movement-responses", "number concepts" / "number-concepts", "number +terms" / "number-terms", "psychophysical" / "psycho-physical", "some +one" / "someone", "sound waves" / "sound-waves", "thought processes" / +"thought-processes", "tieraugen" / "tier-augen", "time measurements" / +"time-measurements", "training process" / "training-process", "vaudeville +stage" / "vaudeville-stage", "well disposed" / "well-disposed", "well +known" / "well-known", "well trained" / "well-trained" "zoologist" / +"zooelogist", "Zoological" / "Zooelogical". + +There is no direct reference to Table of Reference item 105 or 112 +within this book. + +Here is a list of the minor typographical corrections made: + + - Bracket removed following "1904" on Page vii + - "VI" changed to "IV" on Page vii + - Hyphen added between "September" and "Commission" on Page vii + - "vice versa" italicized on Page 20 + - Double quote added after "'Hans'?" on Page 36 + - "elasping" changed to "elapsing" on Page 50 + - Bracket removed following "utility." on Page 58 + - "Futhermore" changed to "Furthermore" on Page 67 + - "wtih" changed to "with" on Page 77 + - Comma removed after "Problems" on Page 78 + - Comma removed after "errors" on Page 82 + - Comma removed after "errors" on Page 82 + - "reponse" changed to "response" on Page 83 + - Comma changed to period after "one" on Page 83 + - Period added after "Mr" on Page 89 + - Comma added after "continuously" on Page 91 + - "preceive" changed to "perceive" on Page 98 + - Double quote added before "Inhalt" on Page 115 + - "concrn" changed to "concern" on Page 116 + - "of" changed to "is" on Page 122 + - "is" changed to "of" on Page 122 + - Period removed after "I" on Page 127 + - "to to" replaced by "to" on Pages 135 and 136 + - Period added after "50cm" on Page 138 + - Double quote added after "you?" on Page 146 + - Double quote removed after "Perseverationstendenz" on Page 150 + - Comma removed from before "continued" on Page 154 + - "proceesses" changed to "processes" on Page 156 + - em-dash changed to hyphen between "soixante" and "six" on Page 159 + - "baguette")" changed to "baguette)"" on Page 160 + - "role" changed to "role" on Page 161 + - "asociate" changed to "associate" on Page 162 + - "taks" changed to "takes" on Page 162 + - em-dash changed to hyphen before "lens" on Page 170 + - Double quote added before "streifenfoermige" on Page 173 + - "satisfactury" changed to "satisfactory" on Page 174 + - "thought" changed to "though" on Page 174 + - "explantion" changed to "explanation" on Page 179 + - Comma added after "Another" on Page 188 + - "53" changed to "73" on Page 192 + - Apostrophe changed to comma between "84" and "85" on Page 198 + - "detail" changed to "details" on Page 206 + - "Ostens'" changed to "Osten's" on Page 209 + - "expectpectantly" changed to "expectantly" on Page 216 + - Comma changed to period after "stimuli" on Page 224 + - "suppossed" changed to "supposed" on Page 231 + - Double quote added after "himself" on Page 235 + - "diminshingly" changed to "diminishingly" on Page 240 + - "acounts" changed to "accounts" on Page 243 + - Single quote moved from before "twice," to after it on Page 250 + - Double quote removed from before "How" on Page 251 + - "af" changed to "of" on Page 255 + - Period removed after "found?" on Page 258 + - "Von" changed to "von" on Page 263 + - Period removed after "Stuttgart" on Page 272 + - Comma changed to period after "Botany" on Page 279 + + + + + +End of the Project Gutenberg EBook of Clever Hans, by Oskar Pfungst + +*** END OF THIS PROJECT GUTENBERG EBOOK CLEVER HANS *** + +***** This file should be named 33936.txt or 33936.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/3/3/9/3/33936/ + +Produced by Audrey Longhurst, Linda Hamilton and the Online +Distributed Proofreading Team at http://www.pgdp.net + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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