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diff --git a/33936.txt b/33936.txt new file mode 100644 index 0000000..99727ab --- /dev/null +++ b/33936.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: 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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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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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" / +"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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