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| author | Roger Frank <rfrank@pglaf.org> | 2025-10-15 04:35:19 -0700 |
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| committer | Roger Frank <rfrank@pglaf.org> | 2025-10-15 04:35:19 -0700 |
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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..6833f05 --- /dev/null +++ b/.gitattributes @@ -0,0 +1,3 @@ +* text=auto +*.txt text +*.md text diff --git a/10843-0.txt b/10843-0.txt new file mode 100644 index 0000000..76bc713 --- /dev/null +++ b/10843-0.txt @@ -0,0 +1,5911 @@ +*** START OF THE PROJECT GUTENBERG EBOOK 10843 *** + +The Mental Life of Monkeys and Apes: + A Study of Ideational Behavior + + + ROBERT M. YERKES + Harvard University + + + + + BEHAVIOR MONOGRAPHS + Volume 3, Number 1, 1916 + Serial Number 12 + Edited by JOHN B. WATSON + The Johns Hopkins University + + +WITH SIX PLATES AND FIVE TEXT FIGURES + + + + + + +CONTENTS + + I. Interests, opportunity and materials + + II. Observational problems and methods + + III. Results of multiple-choice experiments: + + 1. Skirrl, _Pithecus irus_ + 2. Sobke, _Pithecus rhesus_ + 3. Julius, _Pongo pygmaeus_ + + IV. Results of supplementary tests of ideational behavior: + + 1. Julius, _Pongo pygmaeus_: + Box stacking experiment + Box and pole experiment + Draw-in experiment + Lock and key test + 2. Skirrl, _Pithecus irus_: + Box stacking experiment + Box and pole experiment + Draw-in experiment + Hammer and nail test + Other activities + 3. Sobke, _Pithecus rhesus_: + Box stacking experiment + Draw-in experiment + Box and pole experiment + Other activities + + V. Miscellaneous observations: + + 1. Right- and left-handedness + 2. Instinct and emotion: + Maternal instinct + Fear + Sympathy + + VI. Historical and critical discussion of ideational behavior in + monkeys and apes: + + 1. Evidences of ideation in monkeys + 2. Evidences of ideation in apes + + VII. Provision for the study of the primates and especially the monkeys + and anthropoid apes + +VIII. Bibliography + + + +I + +INTERESTS, OPPORTUNITY AND MATERIALS + + +Two strong interests come to expression in this report: the one in the +study of the adaptive or ideational behavior of the monkeys and the +apes; and the other in adequate and permanent provision for the thorough +study of all aspects of the lives of these animals. The values of these +interests and of the tasks which they have led me to undertake are so +widely recognized by biologists that I need not pause to justify or +define them. I shall, instead, attempt to make a contribution of fact on +the score of each interest. + +While recognizing that the task of prospecting for an anthropoid or +primate station may in its outcome prove incomparably more important for +the biological and sociological sciences and for human welfare than my +experimental study of ideational behavior, I give the latter first place +in this report, reserving for the concluding section an account of the +situation regarding our knowledge of the monkeys, apes, and other +primates, and a description of a plan and program for the thorough-going +and long continued study of these organisms in a permanent station or +research institute. + +In 1915, a long desired opportunity came to me to devote myself +undividedly to tasks which I have designated above as "prospecting" for +an anthropoid station and experimenting with monkeys and apes. First of +all, the interruption of my academic duties by sabbatical leave gave me +free time. But in addition to this freedom for research, I needed +animals and equipment. These, too, happily, were most satisfactorily +provided, as I shall now describe. + +When in 1913, while already myself engaged in seeking the establishment +of an anthropoid station, I heard of the founding of such an institution +at Orotava, Tenerife, the Canary Islands, I immediately made inquiries +of the founder of the station, Doctor Max Rothmann of Berlin, concerning +his plans (Rothmann, 1912).[1] As a result of our correspondence, I was +invited to visit and make use of the facilities of the Orotava station +and to consider with its founder the possibility of coöperative work +instead of the establishing of an American station. This invitation I +gratefully accepted with the expectation of spending the greater part of +the year 1915 on the island of Tenerife. But the outbreak of the war +rendered my plan impracticable, while at the same time destroying all +reasonable ground for hope of profitable coöperation with the Germans in +the study of the anthropoids. In August, 1915, Doctor Rothmann died. +Presumably, the station still exists at Orotava in the interests of +certain psychological and physiological research. So far as I know, +there are as yet no published reports of studies made at this station. +It seems from every point of view desirable that American psychologists +should, without regard to this initial attempt of the Germans to provide +for anthropoid research, further the establishment of a well equipped +American station for the study not only of the anthropoid apes but of +all of the lower primates. + +[Footnote 1: See bibliography at end of report.] + +In the early months of the war while I was making every effort to obtain +reliable information concerning conditions in the Canary Islands, I +received an urgent invitation from my friend and former student, Doctor +G. V. Hamilton, to make use of his collection of animals and laboratory +at Montecito, California, during my leave of absence from Harvard. This +invitation I most gladly accepted, and in February, 1915, I established +myself in Santa Barbara, in convenient proximity to Doctor Hamilton's +private laboratory where for more than six months I was able to work +uninterruptedly under nearly ideal conditions. + +Doctor Hamilton without reserve placed at my disposal his entire +collection of animals, laboratory, and equipment, provided innumerable +conveniences for my work, and in addition, bore the entire expense of my +investigation. I cannot adequately thank him for his kindness nor make +satisfactory acknowledgment here of his generous aid. Thanks to his +sympathetic interest and to the courtesy of the McCormick family on +whose estate the laboratory was located, my work was done under wholly +delightful conditions, and with assistance from Ramon Jimenez and Frank +Van Den Bergh, Jr., which was invaluable. The former aided me most +intelligently in the care of the animals and the construction of +apparatus; and the latter, especially, was of very real service in +connection with many of my experiments. + +The collection of animals which Doctor Hamilton placed at my disposal +consisted of ten monkeys and one orang utan. The monkeys represented +either _Pithecus rhesus_ Audebert (_Macacus rhesus_), _Pithecus irus_ F. +Cuvier (_Macacus cynomolgos_), or the hybrid of these two species +(Elliot, 1913). There were two eunuchs, five males, and three females. +All were thoroughly acclimated, having lived in Montecito either from +birth or for several years. The orang utan was a young specimen of +_Pongo pygmaeus_ Hoppius obtained from a San Francisco dealer in +October, 1914 for my use. His age at that time, as judged by his size +and the presence of milk teeth, was not more than five years. So far as +I could discover, he was a perfectly normal, healthy, and active +individual. On June 10, 1915, his weight was thirty-four pounds, his +height thirty-two inches, and his chest girt twenty-three inches. On +August 18 of the same year, the three measurements were thirty-six and +one-half pounds, thirty-three inches, and twenty-five inches. + +For the major portion of my experimental work, only three of the eleven +animals were used. A growing male, _P. rhesus_ monkey, known as Sobke; a +mature male, _P. irus_, called Skirrl; and the young orang utan, which +had been named Julius. Plates I and II present these three subjects of +my experiments in characteristically interesting attitudes. In plate I, +figure 1, Julius appears immediately behind the laboratory seated on a +rock, against a background of live oaks. This figure gives one an +excellent idea of the immediate environment of the laboratory. Figure 2 +of the same plate is a portrait of Julius taken in the latter part of +August. By reason of the heavy growth of hair, he appeared considerably +older as well as larger at this time than when the photograph for figure +1 was taken. In plate II, figure 3, Julius is shown in the woods in the +attitude of reaching for a banana, while in figure 4 of the same plate +he is represented as walking upright in one of the cages. + +Likenesses of Sobke are presented in figures 5 and 6 of plate II. In the +latter of these figures he is shown stretching his mouth, apparently +yawning but actually preparing for an attack on another monkey behind +the wire screen. Figure 7 of this plate indicates Skirrl in an +interesting attitude of attention and with an obvious lack of +self-consciousness. The same monkey is represented again in figures 8 +and 9 of plate II, this time in the act of using hammer and saw. + + +EXPLANATION OF PLATE II + + +FIGURE 3.--Orang utan, Julius, reaching for banana. + +FIGURE 4.--Julius walking across his cage. + +FIGURE 5.--_P. rhesus_, Sobke. + +FIGURE 6.--Sobke stretching his jaws (yawn?) preparatory to a fight. + +FIGURE 7.--_P. irus_, Skirrl. + +FIGURE 8.--Skirrl using hammer and nail. + +FIGURE 9.--Skirrl using a saw. + + + +All of the animals except the orang utan had been used more or less for +experiments on behavior by Doctor Hamilton, but this prior work in no +way interfered with my own investigation. Doctor Hamilton has +accumulated a large mass of the most valuable and interesting +observations on the behavior of monkeys, and he more thoroughly +understands them than any other observer of whom I have knowledge. Much +to my regret and embarrassment in connection with the present report, he +has thus far published only a small portion of his data (Hamilton, 1911, +1914). In his most recent paper on "A study of sexual tendencies in +monkeys and baboons," he has given important information concerning +several of the monkeys which I have observed. For the convenience of +readers who may make use of both his reports and mine, I am designating +the animals by the names previously given them by Hamilton. The +available and essential information concerning the individuals is +presented below. + + + +_List of animals in collection_ + +Skirrl. _Pithecus irus_. Adult male. + +Sobke. _P. rhesus_. Young adult male. + +Gertie. _P. irus-rhesus_. Female. Born November, 1910. + +Maud. _P. rhesus_. Young adult female. + +Jimmy II. _P. irus_. Adult male. + +Scotty. _P. irus_ (?). Adult male. + +Tiny. _P. irus-rhesus_. Female. Born August, 1913. + +Chatters. _P. irus_. Adult eunuch. + +Daddy. _P. irus_. Adult eunuch. + +Mutt. _P. irus_. Young adult male. Born August, 1911. + +Julius. _Pongo pygmaeus_. Male. Age, 4 years to 5 years. + + + +When I arrived in Santa Barbara, Doctor Hamilton was about to remodel, +or rather reconstruct, his animal cages and laboratory. This gave us +opportunity to adapt both to the special needs of my experiments. The +laboratory was finally located and built in a grove of live oaks. From +the front it is well shown by figure 10 of plate III, and from the rear, +by figure 11. Its location was in every way satisfactory for my work, +and in addition, the spot proved a delightful one in which to spend +one's time. + + +[Illustration: FIGURE 12.--Ground plan of Montecito laboratory and +cages. Scale 1/120 + +L, laboratory; C, cages; A, experiment room in which multiple-choice +apparatus was installed; B, E, additional rooms for research; D, store +room and shop; Z, large central cage communicating with the eight +smaller cages 1-8.] + + +Figure 12 is a ground plan, drawn to scale, of the laboratory and the +adjoining cages, showing the relations of the several rooms of the +laboratory among themselves and to the nine cages. Although the +construction was throughout simple, everything was convenient and so +planned as to expedite my experimental work. The large room A, adjoining +the cages, was used exclusively for an experimental study of ideational +behavior by means of my recently devised multiple-choice method. +Additional, and supplementary, experiments were conducted in the large +cage Z. Room D served as a store-room and work-shop. + +The laboratory was forty feet long, twenty-two feet wide, and ten feet +to the plate. Each small cage was six, by six, by twelve feet deep, +while the large compartment into which each of the smaller cages opened +was twenty-four feet long, ten feet wide, and twelve feet deep. + + + +II + +OBSERVATIONAL PROBLEMS AND METHODS + + +My chief observational task in Montecito was the study of ideational +behavior, or of such adaptive behavior in monkeys and apes as +corresponds to the ideational behavior of man. It was my plan to +determine, so far as possible in the time at my disposal, the existence +or absence of ideas and the rôle which they play in the solution of +problems by monkeys and apes. I had in mind the behavioristic form of +the perennial questions: Do these animals think, do they reason, and if +so, what is the nature of these processes as indicated by the +characteristics of their adaptive behavior? + +My work, although obviously preliminary and incomplete, differs from +most of the previous studies of the complex behavior of the infrahuman +primates in that I relied chiefly upon a specially devised method and +applied it systematically over a period of several months. The work was +intensive and quantitative instead of more or less incidental, casual, +and qualitative as has usually been the case. Naturally, during the +course of my special study of ideational behavior observations were made +relative to various other aspects of the life of my subjects. Such, for +example, are my notes on the use of the hands, the instincts, the +emotions, and the natural aptitudes of individuals. It is, indeed, +impossible to observe any of the primates without noting most +interesting and illuminating activities. And although the major portion +of my time was spent in hard and monotonous work with my experimental +apparatus, I found time each day to get into intimate touch with the +free activities of my subjects and to observe their social relations and +varied expressions of individuality. As a result of my close +acquaintance with this band of primates, I feel more keenly than ever +before the necessity of taking into account, in connection with all +experimental analyses of behavior, the temperamental characteristics, +experience, and affective peculiarities of individuals. + +The light which I have obtained on the general problem of ideation has +come, first, through a method which I have rather inaptly named the +multiple-choice method, and second, and more incidentally, through a +variety of supplementary methods which are described in Section IV of +this report. These supplementary methods are simple tests of ideation +rather than systematic modes of research. They differ from my chief +method, among other respects, in that they have been used by various +investigators during the past ten or fifteen years. It was not my aim to +repeat precisely the observations made by others, but instead to verify +some of them, and more especially, to throw additional light on my main +problem and to further the analysis of complex behavior. + +What has been referred to as the multiple-choice method was devised by +me three years ago as a means of obtaining strictly comparable objective +data concerning the problem-solving ability of various types and +conditions of animals. The method was first tried with human subjects in +the Psychopathic Hospital, Boston, with a crude keyboard apparatus +which, however, proved wholly satisfactory as a means of demonstrating +its value. It has since been applied by means of mechanisms especially +adapted to the structure and activities of the organisms, to the study +of the behavior of the crow, pig, rat, and ringdove (Yerkes, 1914; +Coburn and Yerkes, 1915; Yerkes and Coburn, 1915). The method has also +been applied with most gratifying results to the study of the +characteristics of ideational behavior in human defectives,--children, +and adults,--and in subjects afflicted with various forms of mental +disease. It is at present being tried out as a practical test in +connection with vocational guidance and various forms of institutional +examination, such as psychopathic hospital and court examinations. + +As no adequate description of the method has yet been published to which +I can here refer, it will be necessary to present its salient +characteristics along with a description of the special form of +apparatus which was found suitable for use with monkeys and apes. + +The method is so planned as to enable the observer to present to any +type or condition of organism which he wishes to study any one or all of +a series of problems ranging from the extremely simple to the complex +and difficultly soluble. All of the problems, however, are completely +soluble by an organism of excellent ideational ability. For the human +subject, the solution of the easiest problem of all requires almost no +effort, whereas even moderately difficult problems may require many +repetitions of effort and hours or days of application to the task. In +each case, the solution of the problem depends upon the perception of a +certain constant relation among a series of objects to which the subject +is required to attend and respond. Such relations are, for example, +secondness from one end of the group, middleness, simple alternation of +ends, or progressive movement by constant steps from one end of a group +to the other. + +It is possible to present such relational problems by means of +relatively simple reaction-mechanisms. In their essential features, all +of the several types of multiple-choice apparatus designed by the writer +and used either by him or by his students and assistants are the same. +They consist of a series of precisely similar reaction-devices, any one +or all of which may be used in connection with a given observation. +These reaction-mechanisms are so chosen as to be suited to the structure +and action-system of the animal to be studied. For the human being the +mechanism consists of a simple key and the total apparatus is a bank of +keys, with such electrical connections as are necessary to enable the +observer to obtain satisfactory records of the subject's behavior. Let +us suppose the bank of keys, as was actually the case in my first form +of apparatus, to consist of twelve separate reaction-mechanisms; and let +us suppose, further, the constant relation (problem) on the basis of +which the subject is required to react to be that of middleness. It is +evident that in successive trials or experiments the keys must be +presented to the subject in odd groups, the possibilities being groups +of 3, 5, 7, 9, or 11. If for a particular observation the experimenter +wishes to present the first three keys at the left end of the keyboard, +he pushes back the remaining nine keys so that they cannot be operated +and requires the subject to select from the group of three keys the one +which on being pressed causes a signal to appear. It is of course the +clearly understood task of the subject to learn to select the correct +key in the group on first trial. This becomes possible only as the +subject observes the relation of the key which produces the desired +effect to the other keys in the group. On the completion of a subject's +reaction to the group of three keys, a group of seven keys at the +opposite end of the keyboard may, for example, be presented. Similarly, +the subject is required to discover with the minimum number of trials +the correct reaction-mechanism. Thus, time after time, the experimenter +presents a different group of keys so that the subject in no two +successive trials is making use of the same portion of the keyboard. It +is therefore impossible for him to react to spatial relations in the +ordinary sense and manner, and unless he can perceive and appropriately +respond to the particular relation which constitutes the only constant +characteristic of the correct reaction-mechanism for a particular +problem, he cannot solve the problem, or at least cannot solve it +ideationally and on the basis of a small number of observations or +trials. + +For the various infrahuman animals whose ideational behavior has been +studied by means of this method, it has been found eminently +satisfactory to use as reaction-mechanisms a series of similar boxes, +each with an entrance and an exit door. An incentive to the selection of +the right box in a particular test is supplied by food, a small quantity +of which is placed in a covered receptacle beyond the exit door of each +of the boxes. Each time an animal enters a wrong box, it is punished for +its mistake by being confined in that box for a certain period, ranging +from five seconds to as much as two minutes with various individuals or +types of organism. This discourages random, hasty, or careless choices. +When the right box is selected, the exit door is immediately raised, +thus uncovering the food, which serves as a reward. After eating the +food thus provided, the animal, according to training, returns to the +starting point and eagerly awaits an opportunity to attempt once more to +find the reward which it has learned to expect. With this form of the +apparatus, the boxes among which choice may be made are indicated by the +raising (opening) of the front door. + +Since with various birds and mammals the box form of apparatus had +proved most satisfactory, I planned the primate apparatus along similar +lines, aiming simply to adapt it to the somewhat different motor +equipment and destructive tendencies of the monkeys. I shall now briefly +describe this apparatus as it was constructed and used in the Montecito +laboratory. + + + +EXPLANATION OF PLATE IV + +FIGURE 13.--Multiple-choice apparatus, showing observer's bench + and writing stand. +FIGURE 14.--Apparatus as seen from observer's bench. +FIGURE 15.--Entrances to multiple-choice boxes as seen from + the response-compartment. +FIGURE 16.--Apparatus as seen from the rear, showing exit + doors, food receptacles, and covers for same. + + + +The apparatus was built in room A (figure 12), this room having been +especially planned for it with respect to lighting as well as dimensions +and approaches. It was unfortunately impossible to obtain photographs +showing the whole of the apparatus, but it is hoped that the four +partial views of plate IV may aid the reader who is unfamiliar with +previously described similar devices to grasp readily the chief points +of construction. In this plate, figure 13 shows the front of the +complete apparatus, with the alleyway and door by way of which the +experimenter could enter. The investigator's observation-bench and +record-table also appear in this figure, together with weighted cords +used to operate the various doors and the vertically placed levers by +means of which each pair of doors could be locked. Figure 14 is the view +presented to the observer as he stood on the bench or observation stand +of figure 13 and looked over the entire apparatus. Three of the entrance +doors are shown at the right of this figure as raised, whereas the +remainder of the nine entrance doors of the apparatus are closed. Figure +15 is a view of the entrance doors from below the wire roof of the +apparatus. Again, two of the doors are shown as raised, and three +additional ones as closed. The rear of the apparatus appears in figure +16, in which some of the exit doors are closed and others open. In the +latter case, the food receptacles appear, and on the lower part of the +raised doors of the corresponding boxes may be seen metal covers for the +food receptacles projecting at right angles to the doors, while on the +lower edge of each door is an iron staple used to receive a sliding bar +which could be operated from the observer's bench as a means of locking +the doors after they had been closed. The space beyond the exit doors +was used as an alleyway for the return of the animals to the starting +point. + +It will be necessary at various points in later descriptions to refer to +these several figures. But further description of them will be more +readily appreciated after a careful examination of the ground plan of +the apparatus presented as figure 17 In accordance with the labelling of +this figure, the experimenter enters the apparatus room through doorway +16, passes thence through doorways 17 and 10 to the large cage Z, from +which he has direct access to the animals and can bring them into the +apparatus. The multiple-choice mechanism proper, consisting of nine +similar boxes (nine were used instead of twelve as a matter of +convenience of construction, not because this smaller number is +otherwise preferable) is labelled F. These boxes are numbered 1 to 9, +beginning at the left. This numbering was adhered to in the recording of +results throughout the investigation. The other important portions of +the apparatus are the runway D, from which the subject at the +experimenter's pleasure could be admitted through doorway 12 to the +large response-chamber E; the alleyways G, H, and I, by way of which +return to the starting point was possible; the observation bench C, with +its approach step 13; and the observer's writing table A. + +In the construction of this large apparatus, it was necessary to make +provision for the extremely destructive tendencies of monkeys and +anthropoid apes,--hence the apparent cumbersomeness of certain portions. +It was equally necessary to provide for the protection of the observer +and the prevention of escape of the subjects by completely covering the +apparatus and alleyways with a heavy wire netting. + +Each of the eighteen doors of the multiple-choice boxes, and in addition +doors 11, 12, and 15 of the runway D, were operated by the observer from +his bench C by means of weighted window cords which were carried by +pulleys appropriately placed above the apparatus. Each weight was so +chosen as to be just sufficient to hold its door in position after the +experimenter had raised it. For the convenience of the experimenter in +the rapid operation of the twenty-one doors, the weights for the doors +of runway D were painted gray, those for the entrance doors, white, and +those for the exit doors, black. + +In each entrance door, as is shown in figure 15 of plate IV, a window +was cut so that the experimenter might watch the animal after it had +entered a given box, and especially note when it left the box after +having received its reward. This window was covered with wire netting. +No such windows were necessary in the exit doors, but to them were +attached heavy galvanized iron flanges which served to cover the food +receptacles. One of these flanges is labelled o in figure 17. The food +receptacles were provided by boring holes in a 2 by 4 inch timber +securely nailed to the floor immediately outside of the exit doors. Into +these holes aluminum cups fitted snugly, and the iron flanges, when the +doors were closed, fitted so closely over the cups that it was +impossible for the animals to obtain food from them. + + +[Illustration: FIGURE 17.--Ground plan of multiple-choice apparatus in +experiment room A. Scale 1/60 + +A, record stand; C, bench for observer; B, step as approach to C; D, +alleyway leading to E, response-compartment; F, one of the nine (1-9) +similar multiple-choice boxes; G, H, alleyways leading from boxes to +starting point at D; I, alleyway used by experimenter as approach to +rear of apparatus; W, W, windows; P, alleyway; Z, large cage; 16, +entrance to room A; 17, entrance to apparatus and thence via 10 to +cages; 18, entrance to alleyway 1; 11, 15, entrances to D; 12, entrance +to E; 13, entrance door of box 5; 14, exit door of box 5; o, cover for +food receptacle.] + + +As originally constructed, no provision was made in the apparatus for +locking the entrance and exit doors of the several boxes when they were +closed. But as two of the subjects after a time learned to open the +doors from either outside or inside the boxes, it became necessary to +introduce locking devices which could be operated by the experimenter +from the observation bench. This was readily accomplished by cutting +holes in the floor, which permitted an iron staple, screwed to the lower +edge of each door, to project through the floor. Through these staples +by means of a lever for each of the nine boxes, the observer was able to +slide a wooden bar, placed beneath the floor of the room, thus locking +or unlocking either the entrance door, the exit door, or both, in the +case of any one of the nine boxes. + +Since figure 17 is drawn to scale, it will be needless to give more than +a few of the dimensions of the apparatus. Each of the boxes was 42 +inches long, 18 inches wide, and 72 inches deep, inside measurements. +The alleys D, I, and H were 24 inches, and G 30 inches wide, by 6 feet +deep. The doors of the several boxes were 18 inches wide, by 5 feet +high, while those in the alleyways were 24 inches wide by 6 feet high. +The response-compartment E of figure 17 was 14 feet 4 inches, by 8 feet, +by 6 feet in depth. In order that the apparatus might be used with adult +human subjects conveniently, if such use should prove desirable, the +depth throughout was made 6 feet, and it was therefore possible for the +experimenter to walk about erect in it. + +The experimental procedure was briefly as follows: A small quantity of +food having been placed in each of the food cups and covered by the +metal flanges on the exit doors, the experimenter raised door 11 of +figure 17 and then opened door 10 and the door of the cage in which the +desired subject was confined. After the latter, in search of food, had +entered the runway D, the experimenter lowered door 11 to keep it in +this runway, and immediately proceeded to set the reaction-mechanisms +for an experiment (trial). Let us suppose that the first setting to be +tried involved all of the nine boxes. Each of the entrance doors would +therefore be raised. Let us further suppose that the right door is +defined as the middle one of the group. With the apparatus properly set, +the experimenter next raises door 12, thus admitting the animal to the +response-compartment E. Any one of the nine boxes may now be entered by +it. But if any except number 5, the middle member of the group, be +entered, the entrance door is immediately lowered and both the exit and +entrance doors locked in position so that the animal is forced to remain +in the box for a stated period, say thirty seconds. At the expiration of +this time the entrance door is raised and the animal allowed to retrace +its steps and make another choice. When the middle box is chosen, the +entrance door is lowered and the exit door immediately raised, thus +uncovering the food, which the animal eats. As a rule, by my monkeys and +ape the reward was eaten in the alleyway G instead of in the +multiple-choice box. As soon as the food has been eaten, the exit door +is lowered by the experimenter, and the animal returns by way of G and H +to runway D, where it awaits its next trial. + +As rewards, bananas and peanuts were found very satisfactory, and +although occasionally other foods were supplied in small quantities, +they were on the whole less constantly desired than the former. + +Four problems which had previously been presented to other organisms +were in precisely the same form presented to the three primates. These +problems may be described, briefly, by definition of the right reaction +mechanism, thus: problem 1, the first mechanism at the subject's left; +problem 2, the second mechanism at the subject's right (that is, from +the end of the series at the subject's right); problem 3, alternately, +the first mechanism at the subject's left and the first at its right; +problem 4, the middle mechanism of the group. + +It was my intention to present these four problems, in order, to each of +the three animals, proceeding with them as rapidly as they were solved. +But as it happened, only one of the three subjects got as far as the +fourth problem. When observations had to be discontinued, Sobke was well +along with the last, or fourth problem; Skirrl was at work at the third +problem; and Julius had failed to solve the second problem. + +For each of the problems, a series of ten different settings of the +doors was determined upon in advance. These settings differ from those +employed in a similar investigation with the pig only in that the +numbering of the doors is reversed. In the present apparatus, the boxes +as viewed from the front (entrance) are numbered from the left to the +right end, whereas those of the pig apparatus were numbered from the +right end to the left end. + +Below are presented for each of the several problems (1) the numbers of +the settings presented in series; (2) the numbers of the doors open; (3) +the number of doors open in each setting and for the series of ten +settings; and (4) the number of the right door. + + + +PROBLEM 1. First mechanism at left of group + + Doors No. of No. of +Settings open doors open right door + 1..................1.2.3......................3..................1 + 2..................8.9........................2..................8 + 3..................3.4.5.6.7..................5..................3 + 4..................7.8.9......................3..................7 + 5..................2.3.4.5.6..................5..................2 + 6..................6.7.8......................3..................6 + 7..................5.6.7......................3..................5 + 8..................4.5.6.7.8..................5..................4 + 9..................7.8.9......................3..................7 +10..................1.2.3......................3..................1 + -- + Total 35 + + +PROBLEM 2. Second mechanism from the right end of group + + Doors No. of No. of +Settings open doors open right door + 1..................7.8.9......................3..................8 + 2..................1.2.3.4....................4..................3 + 3..................2.3.4.5.6.7................6..................6 + 4..................1.2.3.4.5.6................6..................5 + 5..................4.5.6.7.8..................5..................7 + 6..................1.2.3......................3..................2 + 7..................2.3.4.5....................4..................4 + 8..................1.2.3.4.5.6.7.8.9..........9..................8 + 9..................1.2.3.4....................4..................3 +10..................3.4.5.6.7.8................6..................7 + -- + Total 50 + + +PROBLEM 3. Alternately the first mechanism at the left and the + first at the right end of the group + + Doors No. of No. of +Settings open doors open right door + 1..................5.6.7......................3..................5 + 2..................5.6.7......................3..................7 + 3..................1.2.3.4.5.6................6..................1 + 4..................1.2.3.4.5.6................6..................6 + 5..................4.5.6.7.8..................5..................4 + 6..................4.5.6.7.8..................5..................8 + 7..................2.3.4.5....................4..................2 + 8..................2.3.4.5....................4..................5 + 9..................3.4.5.6.7.8.9..............7..................3 +10..................3.4.5.6.7.8.9..............7..................9 + -- + Total 50 + + +PROBLEM 4. Middle mechanism of the group + + Doors No. of No. of +Settings open doors open right door + 1..................2.3.4......................3..................3 + 2..................5.6.7.8.9..................5..................7 + 3..................1.2.3.4.5.6.7..............7..................4 + 4..................7.8.9......................3..................8 + 5..................4.5.6.7.8..................5..................6 + 6..................1.2.3.4.5.6.7.8.9..........9..................5 + 7..................1.2.3......................3..................2 + 8..................2.3.4.5.6..................5..................4 + 9..................3.4.5.6.7.8.9..............7..................6 +10..................6.7.8......................3..................7 + -- + Total 50 + + + +It was found desirable after a problem had been solved to present a new +and radically different series of settings in order to determine to what +extent the subject had learned to choose the correct door by memorizing +each particular setting. These supplementary observations may be known +as control experiments, and the settings as supplementary settings. In +case of these, as for the original settings, the essential facts are +presented in tabular arrangement. + + + +Settings for Control Experiments + +PROBLEM 1. First at left end + + Doors No. of No. of +Settings open doors open right door + 1..................2.3.4......................3..................2 + 2..................6.7.8.9....................4..................6 + 3..................3.4.5......................3..................3 + 4..................4.5.6.7.8.9................6..................4 + 5..................6.7.8.9....................4..................6 + 6..................1.2.3.4.5..................5..................1 + 7..................2.3.4.5.6.7.8..............7..................2 + 8..................3.4.5.6.7.8................6..................3 + 9..................5.6.7......................3..................5 +10..................1.2.3.4.5.6.7.8.9..........9..................1 + + +PROBLEM 2. Second from right end + + Doors No. of No. of +Settings open doors open right door + 1..................5.6.7.8....................4..................7 + 2..................2.3.4.5.6..................5..................5 + 3..................1.2.3.4.5.6.7.8.9..........9..................8 + 4..................5.6.7......................3..................6 + 5..................1.2.3.4....................4..................3 + 6..................4.5.6......................3..................5 + 7..................2.3.4.5....................4..................4 + 8..................1.2.3......................3..................2 + 9..................1.2.3.4.5.6.7..............7..................6 +10..................2.3.4.5.6.7.8.9............8..................8 + + +PROBLEM 3. Alternate left and right ends + + Doors No. of No. of +Settings open doors open right door + 1..................5.6........................2..................5 + 2..................5.6........................2..................6 + 3..................4.5.6.7.8.9................6..................4 + 4..................4.5.6.7.8.9................6..................9 + 5..................1.2.3.4.5..................5..................1 + 6..................1.2.3.4.5..................5..................5 + 7..................2.3.4.5.6.7................6..................2 + 8..................2.3.4.5.6.7................6..................7 + 9..................3.4.5.6.7.8................6..................3 +10..................3.4.5.6.7.8................6..................8 + + +PROBLEM 4. Middle + + Doors No. of No. of +Settings open doors open right door + 1..................4.5.6.7.8..................5..................6 + 2..................1.2.3......................3..................2 + 3..................1.2.3.4.5.6.7.8.9..........9..................5 + 4..................2.3.4.5.6..................5..................4 + 5..................6.7.8......................3..................7 + 6..................3.4.5.6.7.8.9..............7..................6 + 7..................7.8.9......................3..................8 + 8..................1.2.3.4.5.6.7..............7..................4 + 9..................2.3.4......................3..................3 +10..................3.4.5.6.7..................5..................5 + + + +It was my aim so far as possible to present to a given subject each day +the ten settings under a given problem in order, without interruption. +If for any reason the series of observations had to be interrupted, it +was resumed at the same point subsequently. Occasionally it was found +desirable or necessary to present only five of the series of ten +settings in succession and then to interrupt observations for an +interval of a few minutes or even several hours. But as a rule it was +possible to present the series of ten settings. All things being +considered, it proved more satisfactory to give only ten trials a day to +each subject. Frequently twenty and rarely thirty trials were given on +the same day. In such cases the series of settings was simply repeated. +The only pause between trials was that necessary for resetting the +entrance doors and replenishing the food which served as a reward for +success. + + + +III + +RESULTS OF MULTIPLE-CHOICE EXPERIMENTS + + +1. Skirrl, _Pithecus irus_ + +_Problem 1. First at the Left End_ + + +Systematic work with the multiple-choice apparatus and method described +in the previous section was undertaken early in April with Skirrl, +Sobke, and Julius. The results for each of them are now to be presented +with such measure of detail as their importance seems to justify. + +Skirrl had previously been used by Doctor Hamilton in an experimental +study of reactive tendencies. He proved so remarkably inefficient in the +work that Doctor Hamilton was led to characterize him as feeble-minded, +and to recommend him to me for further study because of his mental +peculiarities. With me he was from the first frank, aggressive, and +inclined to be savage. It was soon possible for me to go into the large +cage, Z, with him and allow him to take food from my hand. He was +without fear of the experimental apparatus and it proved relatively easy +to accustom him to the routine of the experiment. Throughout the work he +was rather slow, inattentive, and erratic. + +Beginning on April 7, I sought to acquaint him with the multiple-choice +apparatus by allowing him to make trips through the several boxes, with +the reward of food each time. Thus, for example, with the entrance and +exit doors of box 7 raised, the monkey was allowed to pass into the +reaction-compartment E and thence through box 7 to the food cup. As soon +as he had finished eating, he was called back to D by the experimenter +and, after a few seconds, allowed, similarly, to make a trip by way of +one of the other boxes. By reason of this preliminary training he soon +came to seek eagerly for the reward of food. + +On April 10 the apparatus was painted white in order to increase the +lightness and thus render it easier for the experimenter to observe the +animal's movements, and when on April 12 Skirrl was again introduced to +it for further preliminary training, he utterly refused to enter the +boxes, giving every indication of extreme fear of the white floors and +even of the sides of the boxes. Finally, the attempts to induce him to +enter the boxes had to be given up, and he was returned to his cage +unfed. The following day I was equally unsuccessful in either driving or +tempting him with food into the apparatus. But on April 14 he was so +hungry that he was finally lured in by the use of food. He cautiously +approached the boxes and attempted to climb through on the sides instead +of walking on the floor. It was perfectly evident that he had an +instinctive or an acquired fear of the white surfaces. As the matter was +of prime importance for the success of my work, I inquired of Doctor +Hamilton, and of the men in charge of the cages, for any incident which +might account for this peculiar behavior, and I learned that some three +months earlier, while the animal cages were being whitewashed, Skirrl +had jumped at one of the laborers who was applying a brush to the +framework of one of the cages and had shaken some lime into his eyes. He +was greatly frightened and enraged. Evidently he experienced extreme +discomfort, if not acute pain, and there resulted an association with +whiteness which was quite sufficient to cause him to avoid the freshly +painted apparatus. + +Having obtained an adequate explanation of this monkey's peculiar +behavior, I proceeded with my efforts to induce him to work smoothly and +rapidly, and on April 15, by covering the floor with sawdust, I so +diminished the influence of the whiteness as to render the preliminary +training fairly satisfactory. At the end of two more days everything was +going so well that it seemed desirable to begin the regular experiment. + +On the morning of April 19, Skirrl was introduced to the apparatus and +given his first series of ten trials on problem 1. This problem demanded +the selection of the first door at the left in any group of open doors. +The procedure was as previously described in that the experimenter +raised the entrance doors of a certain group of boxes, admitted the +animal to the reaction-chamber, punished incorrect choices by confining +the animal for thirty seconds, and rewarded correct choices by raising +the exit door and thus permitting escape and the obtaining of food. The +trials were given in rapid succession, and the total time required for +this first series of ten trials was thirty-five minutes. Skirrl worked +faithfully throughout this interval and exhibited no marked +discouragement. When confined in a box he showed uneasiness and +dissatisfaction by moving about constantly, shaking the doors, and +trying to raise them in order to escape. + +For the series of settings used in connection with problem 1, the reader +is referred to page 18. In the first setting, the doors numbered 1, 2, +and 3, were opened. As it happened, the animal when admitted to the +reaction-chamber immediately chose box l. Having received the reward of +food, he was called back to D, and doors 8 and 9 having been raised in +preparation for the next trial, he was again admitted to the +reaction-chamber. This time he quickly chose box 9 and was confined +therein for thirty seconds. On being released, he chose after an +interval of four minutes, box 8, thus completing the trial. + +As it is highly important, not only in connection with the present +description of behavior, but also for subsequent comparison of the +reactions of different types of organism in this experiment, to present +the detailed records for each trial, tables have been constructed which +offer in brief space the essential data for every trial in connection +with a given problem. + +Table 1 contains the results for Skirrl in problem 1. It is constructed +as follows: the date of a series of trials appears in the first vertical +column; the numbers (and number) of the trials for the series or date +appear in column 2; the following ten columns present respectively the +results of the trials for each of the ten settings. Each number, in +these results, designates a box entered. At the extreme right of the +table are three columns which indicate, first, the number of trials in +which the right box was chosen first, column headed R; and second, the +number of trials in which at least one incorrect choice occurred, column +headed W. In the last column, the daily ratio of these first choices +appears. + +Taking the first line of table 1 below the explanatory headings, we note +on April 19 ten trials, numbered 1 to 10, were given to Skirrl. In trial +1, with setting 1, he chose correctly the first time, and the record is +therefore simply 1. In trial 2, setting 2, he incorrectly chose box 9, +the first time. At his next opportunity, he chose box 8, which was the +right one. The record therefore reads 9.8. In trial 3, setting 3, he +chose incorrectly twice before finally selecting the right box. The +record reads 6.7.3, and so on throughout the ten trials which constitute +a series. The summary for this series indicates three right and seven +wrong first choices, that is, three cases in which the right box was +entered first. The ratio of right to wrong first choices is therefore 1 +to 2.33. Since the total number of doors open in the ten settings is +thirty-five, and since in each of the ten settings one door is +describable as the right door, the probable ratio, apart from the +effects of training, of right to wrong first choices is 1 to 2.50. It is +evident, therefore, that Skirrl in his first series of trials closely +approximated expectation in the number of mistakes. + + + +TABLE 1 + +Results for Skirrl, _P. irus_, in Problem 1 + +========+==========+=========+=========+===========+=============+===========+===========+===========+=============+===========+===========+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | Ratio +Date | of | | | | | | | | | | | R | W | of + | trials | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | R to W +--------+----------+---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- + April | | | | | | | | | | | | | | + 19 | 1- 10 | 1 | 9.8 | 6.7.3 | 9.7 | 6.2 | 7.8.6 | {6.7.7.7 | 4 | 7 | 2.3.3.1 | 3 | 7 | 1:2.33 + | | | | | | | | {6.5 | | | | | | + | | | | | | | | | | | | | | + 20 | 11- 20 | 3.2.1 | 9.8 | 5.3 | 7 | 4.2 | 8.8.6 | 5 | 8.4 | 7 | 3.1 | 3 | 7 | 1:2.33 + 21 | 21- 30 | 3.1 | 8 | 3 | 8.7 | 6.2 | 6 | 5 | 6.4 | 9.7 | 1 | 5 | 5 | 1:1.00 + 22 | 31- 40 | 1 | 9.8 | 3 | 7 | 6.2 | 6 | 6.7.5 | 5.8.4 | 9.8.9.8.7 | 2.1 | 4 | 6 | 1:1.50 + 23 | 41- 50 | 2.3.1 | 8 | 5.7.3 | 7 | 4.2 | 6 | 5 | 7.8.4 | 7 | 3.1 | 5 | 5 | 1:1.00 + 24 | 51- 60 | 1 | 8 | 4.5.7.3 | 9.7 | 5.6.2 | 6 | 6.7.5 | 6.4 | 8.9.7 | 1 | 4 | 6 | 1:1.50 + 26 | 61- 70 | 1 | 8 | 6.7.4.7.3 | 7 | 4.5.6.2 | 6 | 5 | 8.4 | 7 | 3.2.3.1 | 6 | 4 | 1: .67 + 27 | 71- 80 | 3.1 | 8 | 3 | 9.7 | 4.6.2 | 7.6 | 6.5 | 5.8.4 | 7 | 1 | 4 | 6 | 1:1.50 + 28 | 81- 90 | 2.3.1 | 8 | 3 | 7 | 4.5.6.2 | 6 | 5 | 5.8.4 | 7 | 1 | 7 | 3 | 1: .43 + 29 | 91- 100 | 1 | 8 | 3 | 9.7 | 6.2 | 6 | 5 | 4 | 7 | 1 | 8 | 2 | 1: .25 + 30 | 101- 110 | 1 | 8 | 4.3 | 7 | 5.6.2 | 6 | 5 | 4 | 7 | 2.3.1 | 7 | 3 | 1: .43 + May | | | | | | | | | | | | | | + 1 | 111- 120 | 2.3.2.1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: .11 + 3 | 121- 130 | 1 | 8 | 5.6.3 | 7 | 4.5.2 | 6 | 5 | 4 | 7 | 1 | 8 | 2 | 1: .25 +4 and 5 | 131- 140 | 3.2.1 | 8[1] | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: .11 + 5 | 141- 150 | 1 | 8 | 4.3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: .11 +--------+----------+---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- + | | | | | | | | 2.3.4.5 | | | 1.2.3.4.5 | | | + | | 2.3.4 | 6.7.8.9 | 3.4.5 | 4.5.6.7.8.9 | 6.7.8.9 | 1.2.3.4.5 | 6.7.8 | 3.4.5.6.7.8 | 5.6.7 | 6.7.8.9 | | | + | +---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- + 6 | 1- 10 | 2 | 6 | 3 | 4 | 6 | 3.2.1 | 6.2 | 5.6.7.8.3 | 5 | 6.1 | 6 | 4 | 1: .67 +========+==========+=========+=========+===========+=============+===========+===========+===========+=============+===========+===========+===+===+======== + +[Footnote 1: End of series on May 4.] + + + +By reading downward in any particular column of results, one obtains a +description of the changes in the animal's reaction to a particular +setting of the doors. Thus, for instance, in the case of setting 1, +which was presented to the animal in trials numbered 1, 11, 21, and so +on to 141, it is clear from the records that no definite improvement +occurred. But oddly enough, in the case of setting 10, which presented +the same group of open doors, almost all of the reactions are right in +the lower half of the column. For setting 2, it is evident that mistakes +soon disappeared. + +Comparison of the data of table 1 indicates that the number of correct +first choices is inversely proportional to the number of doors in use, +while the number of choices made in a given trial is directly +proportional to the number of doors in use. + +During the first week of work on this problem, Skirrl improved markedly. +His performance was somewhat irregular and unpredictable, but on the +whole the experiment seemed fairly satisfactory. Cold, cloudy, or rainy +days tended to diminish steadiness and to increase the number of +mistakes. Similarly, absence of hunger was unfavorable to continuous +effort to find the right box. + +The period of confinement, as punishment for wrong choices, was +increased from thirty seconds to sixty seconds on April 26. But there is +no satisfactory evidence that this favored the solution of the problem. +Work on May 4 was interrupted by a severe storm, the noise of which so +distracted the monkey that he ceased to work. Consequently, observations +were interrupted on the completion of trial 132, and on May 5, the +series was begun with setting 3. On this date, eighteen trials were +given in succession, and in only one of them did a mistake occur. Since +the ten trials numbered 133 to 142 were correct, Skirrl was considered +to have solved problem 1, and systematic training was discontinued. + +On the following day, as a measure of the extent to which the animal had +learned to select the first door at the left no matter what its position +or the number of doors in the group presented, a control series was +given in which the settings differed from the regular series of +settings. These supplementary settings are presented at the bottom of +table 1 together with the records of reaction in ten trials. + +Since in only six of these ten control settings was the first choice +correct, it is scarcely fair to insist that the animal was reacting on +the basis of an ideational solution of the problem. Rather, it would +seem that he had learned to react to particular settings. A careful +study of all of the data of response, together with notes on the varied +behavior of the animal during the experiments, justifies the statement +that Skirrl's solution of problem 1 was incomplete and unreliable. It +was highly dependent upon the particular situation, or even the +particular door at the left end of the group, and slightly if at all +dependent upon anything comparable to the human idea of first at the +left of the group. + +This particular series of observations has been described and discussed +in some detail in order to make the chief points of method clear. It +will be needless, hereafter, to refer explicitly to many of the +characteristics of reaction or to the important points in the +construction of tables which have been mentioned. + +A graphic representation of Skirrl's learning process in problem 1 is +presented in figure 18. The irregularities are most striking, and fairly +indicate the erraticness of the animal. The curve is based upon the data +in next to the last column of table 1, that is, the column presenting +the errors or wrong first choices in each series of trials. + +Unquestionably, the form of such a curve of learning should be +considered in connection with the method or methods of selecting the +right box employed by the animal during the course of experimentation. +It appears from an analysis of the behavior of Skirrl in problem 1 that +there developed a single definite and persistent method, namely, that of +going to one box in the group, and in case it happened to be a wrong +one, of choosing, on emergence from it, the next toward the right end of +the group, and so on down the line. Having reached the extreme right +end, the tendency was to follow the side of the reaction-chamber around +to the opposite end and to enter the first box at the left end of the +group, which was, of course, the right one. This method appears, with +certain slight variations, in approximately ninety per cent of the +trials which involved incorrect choices. Thus, in the case of trials 121 +to 130, of which eight exhibit right first choices, the remaining two +exhibit the method described above except that the final member at the +right end of the group was in each case omitted. + +[Illustration: FIGURE 18.--Error curves of learning for the solution of +problem 1 (first box at left end).] + +On the whole, Skirrl's behavior in connection with this problem appears +to indicate a low order of intelligence. He persisted in such stupid +acts as that of turning, after emergence from the right box, toward the +right and passing into the blind alley I, instead of toward the left, +through G and H, to D. In contrast with the other animals, he spent much +time before the closed doors of the boxes, instead of going directly to +the open doors, some one of which marked the box in which the reward of +food could be obtained. It is, moreover, obvious that his responses, as +they appear in table 1, are extremely different from those of a human +being who is capable of bringing the idea of first at the left end to +bear upon the problem in question. + + +_Problem 2. Second from the Right End_ + +Following the series of control trials of problem 1 given to Skirrl on +May 6, a period of four days was allowed during which the animal was +merely fed in the boxes each day. This was done in order that he should +partially lose the effects of his previous training to choose the first +box at the left before being presented with the second problem, the +second box from the right. + +On May 11 regular experimentation was begun with problem 2. Naturally +the situation presented unusual difficulties to the monkey because of +his previously acquired habit, and on the first day it was possible to +give only five trials, in all except the first of which Skirrl had to be +aided by the experimenter to find the right box. He persistently, as +appears in the first line of records of table 2, entered the first box +at the left. The series was continued on May 13, but with very +unsatisfactory results, since he apparently had been greatly discouraged +by the unusual difficulties previously met. Only four trials could be +given, and in these the showing made was very poor. It is noteworthy, +however, that in trials 6, 7, and 8, May 13, there was no marked +tendency to choose the first box at the left. Thus quickly had the force +of the previous habit been broken. + +For problem 2, the total number of open doors in the ten settings is +fifty, as appears from the data on page 18, and as ten of these fifty +open doors may be defined as right ones, the expected ratio of right to +wrong first choices in the absence of previous training is 1 to 4. The +actual ratio for the first series given in problem 2 is 1 to 8, while in +the second series it is 0 to 10. + +On the morning of May 13, work was interrupted in the ninth trial by +what seemed at the moment a peculiarly unfortunate accident, but in the +light of later developments, an incident most fruitful of valuable +results. + +Skirrl, in trial 9, directly entered box 1. Since this was not the right +box, he was punished by being confined in it for ten seconds. While in +the box he howled and when the entrance door was raised for him to +retrace his steps, he came out with a rush, showing extreme excitement +and either rage or fear, I could not be sure which. At intervals he +uttered loud cries, which I am now able to identify as cries of alarm. +Repeatedly he went to the open door of box 1 and peered in, or peered +down through the hole in the floor which received the staple on the +door. He refused to enter any one of the open boxes and continued, at +intervals of every half minute or so, his cries. For thirty minutes I +waited, hoping to be able to induce him to complete the series of +trials, but in vain. Although it was obvious that he was eager to escape +from the apparatus, he would not enter any of the boxes even when the +exit doors were raised. Instead, he gnawed at the door (12 in fig. 17) +to the alleyway D and attempted to force his way through, instead of +taking the easy and clear route to the alleys, through one of the boxes. +His behavior was most surprising and puzzling. Finally, I gave up the +attempt to complete the series and returned him to his cage by way of +the entrance door to the response-compartment E. + +I then entered the apparatus to seek some explanation of the animal's +behavior, and my search was rewarded by the finding of two sharp pointed +nails which protruded for an inch or more in the middle of the floor of +box 1. My assistant, who had been charged with the task of installing +the locks for the several doors, had used nails instead of screws for +attaching staples underneath the floor and had neglected to clinch the +nails. Skirrl, in the dim light of the box, doubtless stepped upon one +of the nails and inflicted a painful, although not serious, injury upon +himself. It was impossible for him to see clearly the source of his +injury. He was greatly frightened and expressed the emotion most +vigorously. His behavior strongly suggested a superstitious dread of +some unseen danger. It may be that the instinctive fear of snakes, so +strong in monkeys, was partly responsible for his response. + +The first result of this accident was that more than two weeks were +lost, for it was impossible, during the next few days, to induce the +animal to enter any of the multiple-choice boxes voluntarily. From May +14 to May 24, I labored daily to overcome his newly acquired fear. The +usual procedure was to coax him through one box after another by +standing at the exit door with some tempting morsel of food. After +several days of this treatment, he again trusted himself to the boxes, +although very circumspectly and only when both entrance and exit doors +were raised. Not until May 24 was it possible to resume regular +experimentation, and on that day it was found necessary to indicate the +right box by raising the exit door slightly and then immediately +lowering it. Trials in which this form of aid was given are indicated in +table 2 by a star following the last choice. + +Gradually, Skirrl regained his confidence in the apparatus and began to +work more naturally. For a long time he would not stand punishment, and +it was necessary for the experimenter to be very careful in locking the +doors, since the sound of the bar sliding beneath the floor often +frightened and caused him to quit work. Day after day the tendency to +peer through the holes in the floor at the entrance to the boxes +rendered it clear that the animal feared some danger from beneath the +floor. This behavior was so persistent that much time was wasted in the +experiments. + +On the last day of May, punishment by confinement for ten seconds in +wrong boxes was introduced, but since this tended to discourage the +monkey, there was substituted for it on June 1 the punishment of forcing +him to work his way out of each wrong box by raising the entrance door +which had been closed behind him. This he could fairly readily do, and +his stay in a box rarely measured more than ten seconds. + +As a variation in the mode of procedure, confinement for thirty seconds +was tried on June 5, but it worked unsatisfactorily and had to be +abandoned. During this series, the animal was startled by the sound from +one of the sliding bars under the floor, and in the sixth trial he +refused to work. + +As improvement was very slow, varied modes of rewarding and punishing +the animal were tried in the hope of discovering a means of facilitating +the work. Among the former are the use of banana, grapes, peanuts, and +other eagerly sought foods in varying quantities, and in the latter are +included periods of confinement ranging from ten seconds to sixty +seconds. In the end, confinement of about thirty seconds, combined with +a small quantity of food which was much to the monkey's taste, gave most +favorable results. + +All this time Skirrl's attention to the task in hand was seldom good. He +was easily diverted and even when extremely hungry, often stopped work +in the middle of an early trial, yawned repeatedly and finally sat down +to wait for release from the apparatus. + +The results obtained during the long continued trials with this animal +in problem 2 are presented in table 2, which differs from the previously +described table, first, in that several of the trials are followed by an +asterisk to indicate that aid was given by the experimenter, and second, +in that two additional columns, headed, respectively, R and W, are +presented. These give the right and wrong first choices for each day, +whereas the two columns preceding them give the same data for each +series of ten trials. Similarly, the ratio of right to wrong choices is +presented for each day in table 2, instead of for each series of ten +trials as in table 1. + +From the results of table 2, several peculiarly interesting facts +appear. In the first place the influence of the habit of choosing the +first box at the left disappears with surprising suddenness, and in the +second place, there are remarkable contrasts in the results for +different settings as they appear in their respective vertical columns. +Thus, in the case of setting 1, after the first trial mistakes became +relatively infrequent, whereas in setting 6, which involved the same +number of doors, mistakes continued to be the rule until nearly a +thousand trials had been given. The most likely explanation of this +difference is that for some reason the animal avoided box 9. + +The _reactive tendencies_, or better, the _methods of reaction_ which +manifested themselves during this long series of observations may be +described as follows: (a) choice of the first box at the left; (b) +random choice with tendency to choose first, a box near the middle of +the group; (c) choice of first box at the right followed by the one next +to it on the left; (d) direct choice of the right box. + + + +TABLE 2 + +Results for Skirrl, _P. irus_, in Problem 2 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | 1.2.3.4.5 | | | R | W | R | W | of + | trials | 7.8.9 | 1.2.3.4 | 2.3.4.5.6.7 | 1.2.3.4.5.6 | 4.5.6.7.8 | 1.2.3 | 2.3.4.5 | 6.7.8.9 | 1.2.3.4 | 3.4.5.6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + May | | | | | | | | | | | | | | | | + 11&13 | 1- 9 | 7.7.9.7.8 | {1.2.2.1.4.1 | {2.3.2.3.2.5 | {4.6.1.4.1.1 | 4.4.7 | 3.1.2 | 4 | 4.1.8 | 1 | | 1 | 8 | 1 | 8 | 1: 8.00 + | | | {2.1.2.1.3 | {2.3.2.5.6 | {2.6.1.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 24 | 11- 20 | 8*[1] | 2.4.3* | 4.5.6* | 2.2.5* | 5.6.6.7* | 3.1.2 | {5.2.3.5.3.2 | 4.6.8* | 4.4.3* | 5.5.6.7* | 0 |10 | 0 |10 | 0:10.00 + | | | | | | | | {3.5.2.4* | | | | | | | | + | | | | | | | | | | | | | | | | + 25 | 21- 30 | 8* | 4.4.3* | 5.6 | {6.6.2.3.4 | 6.7 | 2 | 4 | 5.6.3.8 | 4.4.3 | 6.4.6.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | {6.6.5* | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 26 | 31- 40 | 8 | 4.3 | 6 | 4.5 | 6.7 | 3.2 | 5.4 | 5.8 | 4.3 | 5.3.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | | | | | | | | + 27 | 41- 50 | 8 | 4.4.3 | 6 | 5 | 6.8.6.8.7 | 3.3.3.2 | 5.4 | {6.5.4.3 | 4.3 | 5.4.8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | {2.1.5.8 | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 51- 60 | 8 | 4.4.3 | 7.6 | 5 | 5.6.7 | 3.3.3.2 | 4 | {5.4.3 | 4.3 | {5.4.3.3.4.5 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | {3.6.8 | | {6.4.3.5.7 | | | | | + | | | | | | | | | | | | | | | | + 29 | 61- 70 | 8 | 4.3 | 6 | 6.6.5 | 7 | 3.3.3.2 | 5.4 | 7.6.4.7.6.8 | 4.3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 31 | 71- 80 | 8 | 4.4.4.3 | 6 | 6.5 | 6.8.7 | 3.2 | 5.4 | {6.7.6.4.3 | 4.3 | 6.7 | 2 | 8 | 2 | 8 | 1: 4.00 + June | | | | | | | | | {2.6.3.7.8 | | | | | | | + | | | | | | {6.8.6.5.4 | | | | | | | | | | + 1 | 81- 90 | 8 | 4.3 | 6 | 5 | {6.5.6.5.8 | 3.1.3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | | | + | | | | | | {5.4.6.4.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 91- 100 | 9.7.8 | 4.2.4.3 | 7.5.6 | 5 | 6.8.7 | 3.3.1.2 | 5.3.4 | 8 | 4.3 | 6.8.7 | 2 | 8 | 7 |13 | 1: 1.86 + 2 | 101- 110 | 8 | 4.3 | 6 | 5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 6.8.6.5.7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + " | 111- 120 | 8 | 4.3 | 7.3.5.7.6 | {6.2.3.6.4 | 7 | 3.2 | {5.2.3.5.3.2 | 9.6.4.7.8 | {4.1.2 | 6.8.7 | 2 | 8 | 6 |14 | 1: 2.33 + | | | | | {3.6.2.5 | | | {3.5.2.3.4 | | {4.2.3 | | | | | | + | | | | | | | | | | | {6.8.6.3 | | | | | + 3 | 121- 130 | 8 | 4.4.3 | 6 | 5 | 6.7 | 3.2 | {5.3.2.3 | 8 | 4.2.3 | {5.4.5.8.8 | 4 | 6 | | | + | | | | | | | | {5.2.5.4 | | | {6.3.8.7 | | | | | + | | | | | | | | | | | | | | | | + " | 131- 140 | 8 | 4.3 | 5.7.3.2.6 | 4.5 | 5.7 | 1.3.2 | 5.3.4 | 6.7.8 | 4.2.1.3 | 7 | 2 | 8 | 6 |14 | 1: 2.33 + | | | | | | | | | | | | | | | | + 4 | 141- 150 | 8 | 4.3 | 7.6 | 6.5 | 7 | 2 | {5.3.2.3 | 6.8 | 4.1.3 | 5.6.7 | 3 | 7 | | | + | | | | | | | | {5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | + " | 151- 160 | 8 | 4.3 | 6 | 5 | 6.7 | 2 | 4 | 5.6.7.8 | 4.3 | 5.6.8.7 | 5 | 5 | 8 |12 | 1: 1.50 + 5 | 161- 170 | 8 | 4.3 | 7.6 | 6.5 | 6.8.7 | 3.2 | 5.3.2.3.5.4 | 8 | 4.3 | 6.7 | 2 | 8 | | | + " | 171- 176 | 8 | 2.4.3 | 7.6 | 6.5* | 8.7 | 3.2* | | | | | 1 | 5 | 3 |13 | 1: 4.33 + 7 | 177- 180 | | | | | | | 5.4 | 8 | 4.4.3 | 8.7 | 1 | 3 | | | + " | 181- 190 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.3.2.5.4 | 8 | 4.3 | 7 | 4 | 6 | 5 | 9 | 1: 1.80 + 8 | 191- 200 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 | | | + " | 201- 210 | 8 | 4.3 | 6 | 6.4.6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 6 |14 | 1: 2.33 + 9 | 211- 220 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.6.7 | 2 | 8 | | | + " | 221- 230 | 9.8 | 4.3 | 7.6 | 6.5 | 6.7 | 3.2 | 5.4 | 7.6.8 | 4.3 | 7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | | | | | | | | | | | + 10 | 231- 240 | 8 | 4.3 | 7.6 | 6.5 | 6.7 | 3.2 | 5.4 | {3.2.3.2.4.3 | 4.3 | 7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | {2.5.4.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + 11 | 241- 250 | 8 | 4.3 | 7.6 | 6.6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | | | | | | | | 12 | 251- 260 | 8 | 4.3 | 6 | 6.5 | 6.7 | 3.3.2 | 5.4 | {7.6.7.7 | 3 | 3.7* | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | {6.9.8* | | | | | | | + | | | | | | | | | | | | | | | | 14 | 261- 270 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | {5.3.4.3 | 3 | {3.3.3.3.4 | 5 | 5 | 5 | 5 | 1: 1.00 + | | | | | | | | | {9.8* | | {4.6.4.7* | | | | | + | | | | | | | | | | | | | | | | 15 | 271- 280 | 7.9.8 | 4.2.3 | 3.4.3.7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 1 | 9 | | | + " | 281- 290 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 3 | 7 | 4 |16 | 1: 4.00 + | | | | | | | | | | | | | | | | | | | | | | | | | {4.3.2.3 | | | | | | | + 16 | 291- 300 | 7.8 | {4.4.4 | 6 | 6.5 | 7 | 3.3.2 | 5.4 | {6.5.4.3 | 4.3 | 6.7 | 2 | 8 | | | + | | | {4.4.3 | | | | | | {5.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | " | 301- 310 | 8 | 4.4.3 | 7.6 | 6.5 | 7 | 3.3.2 | 5.5.4 | {7.6.5.4.6 | 4.3 | 7 | 3 | 7 | 5 |15 | 1: 3.00 + | | | | | | | | | {5.7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | 17 | 311- 320 | 7.8 | 4.3 | 7.6 | 6.6.5 | 7 | 3.2 | 5.4 | 7.6.7.6.7.8 | 4.3 | 7 | 2 | 8 | | | + " | 321- 330 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 6.7 | 2 | 8 | 4 |16 | 1: 4.00 + 18 | 331- 340 | 7.7.8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | | | + " | 341- 350 | 8 | 4.3 | 7.6 | 6.6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | 7 |13 | 1: 1.86 + 19 | 351- 360 | 8 | 4.3 | 7.6 | 6.5 | 6.5.6.5.7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 361- 370 | 8 | 4.3 | 7.6 | 6.4.3.6.5 | 7 | 3.2 | 5.4 | 9.8 | 4.3 | 7 | 3 | 7 | 6 |14 | 1: 2.33 + 21 | 371- 380 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 8.7 | 2 | 8 | | | + " | 381- 390 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 6 |14 | 1: 2.33 + 22 | 391- 400 | 8 | 4.3 | 7.6 | 6.5 | 6.5.4.6.7 | 3.3.3.2 | 5.4 | 6.7.8 | 4.4.3 | 7 | 2 | 8 | | | + " | 401- 410 | 8 | 3 | 7.6 | 6.5 | 8.7 | 2 | 5.4 | 6.7.7.8 | 3 | 7 | 5 | 5 | 7 |13 | 1: 1.86 + | | | | | | | | | | | | | | | | 23 | 411- 420 | 8 | 4.4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | {7.6.7.6 | 4.3 | 7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | {6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | 24 | 421- 430 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 6 | 4 | | | + " | 431- 440 | 8 | 3 | 7.6 | 6.5 | 7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 |11 | 9 | 1: 0.82 + 25 | 441- 450 | 7.8 | 4.4.3 | 7.6 | 6.5 | 6.5.7 | 3.3.2 | 5.5.4 | 7.8 | 4.3 | 7 | 1 | 9 | 1 | 9 | 1: 9.00 + 26 | 451- 460 | 7.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 461- 470 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 6 |14 | 1: 2.33 + 28 | 471- 480 | 8 | 4.4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 9.8 | 3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + 29 | 481- 490 | 8 | 4.3 | 7.7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + 30 | 491- 500 | 7.9.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 501- 510 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.4.3 | 8.7 | 2 | 8 | 5 |15 | 1: 3.00 + July | | | | | | | | | | | | | | | | + 1 | 511- 520 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | 2 | 521- 530 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | {7.6.5.6.5 | 4.4.3 | 7 | 3 | 7 | | | + | | | | | | | | | {6.5.6.8 | | | | | | | + | | | | | | | | | | | | | | | | " | 531- 540 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 7 |13 | 1: 1.86 + 3 | 541- 550 | 7.8 | 4.4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 5.5.7 | 3 | 7 | | | + " | 551- 560 | 7.8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 5 | 5 | 8 |12 | 1: 1.50 + 5 | 561- 570 | 7.7.8 | 4.3 | 6 | 6.5 | 6.7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 571- 580 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 4 | 6 | 7 |13 | 1: 1.86 + | | | | | | | | | | | | | | | | | | | | | | {6.5.4.6.5 | | | | | | | | | | + 6 | 581- 590 | 7.8 | 4.3 | 7.6 | 6.6.5 | {5.4.5.4.4 | 2 | 3.4 | 6.5.4.3.7.8 | 3 | 7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | {6.5.6.5.8.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | 7 | 591- 600 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 8.7 | 3 | 7 | | | + " | 601- 610 | 7.8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 1 | 9 | 4 |16 | 1: 4.00 + 8 | 611- 620 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 | | | + " | 621- 630 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 9.8 | 4.3 | 8.7 | 1 | 9 | | | + " | 631- 640 | 8 | 4.4.3 | 7.7.6 | 6.5 | 8.7 | 3.2 | 4 | 8 | 4.3 | 8.7 | 3 | 7 | 6 |24 | 1: 4.00 + | | | | | | | | | | | | | | | | 9 | 641- 650 | 7.8 | 4.3 | 7.6 | 6.5 | 6.7 | 3.2 | {3.2.5.3 | 7.6.5.4.8 | 3 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | {2.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | | | | | | | | | | {6.5.4.3.7 | | | | | | | + 10 | 651- 660 | 7.8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | {6.5.4.7.6 | 4.3 | 7 | 3 | 7 | | | + | | | | | | | | | {5.4.8 | | | | | | | + | | | | | | | | | | | | | | | | 10 | 661- 670 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 6 | 4 | 9 |11 | 1: 1.22 + 12 | 671- 680 | 7.8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 6.5.4.7.8 | 4.3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | | | | | | | | 13 | 681- 690 | 8 | 3 | 7.6 | 6.5 | {6.5.4 | 3.2 | 4 | 6.7.8 | 3 | {6.5.4.5 | 4 | 6 | | | + | | | | | | {6.5.7 | | | | | {6.5.8.7 | | | | | + | | | | | | | | | | | | | | | | " | 691- 700 | 8 | 3 | 6 | 5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 8 | 2 |12 | 8 | 1: 0.67 + | | | | | | | | | | | | | | | | 14 | 701- 710 | 8 | 3 | 7.6 | 6.5 | {6.5.4.5 | 2 | 3.5.4 | 8 | 3 | 7 | 6 | 4 | | | + | | | | | | {4.6.8.7 | | | | | | | | | | + " | 711- 720 | 8 | 3 | 6 | 5 | 7 | 2 | 5.4 | 6.5.4.8 | 3 | 6.5.7 | 7 | 3 |13 | 7 | 1: 0.54 + 15 | 721- 730 | 7.8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | | | + " | 731- 740 | 8 | 3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 6 | 4 |11 | 9 | 1: 0.82 + 16 | 741- 750 | 7.8 | 3 | 6 | 6.5 | 7 | 3.2 | 4 | 8 | 3 | 7 | 7 | 3 | | | + " | 751- 760 | 7.8 | 3 | 7.6 | 6.5 | 7 | 2 | 4 | 7.8 | 4.3 | 7 | 5 | 5 |12 | 8 | 1: 0.67 + 17 | 761- 770 | 8 | 4.3 | 6 | 5 | 8.7 | 3.2 | 5.4 | 8 | 4 | 7 | 6 | 4 | | | + " | 771- 780 | 8 | 2.2.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 3 | 7 | 9 |11 | 1: 1.22 + 19 | 781- 790 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 3.4 | 7.6.5.8 | 3 | 7 | 6 | 4 | | | + " | 791- 800 | 7.8 | 3 | 6 | 5 | 7 | 2 | 5.4 | 8 | 3 | 6.5.6.7 | 7 | 3 | | | + " | 801- 810 | 8 | 2.3 | 6 | 5 | 6.5.7 | 2 | 5.4 | 8 | 3 | 7 | 7 | 3 |20 |10 | 1: 0.50 + 20 | 811- 820 | 7.8 | 3 | 7.6 | 5 | 7 | 3.3.2 | 5.4 | 8 | 2.2.3 | 7 | 5 | 5 | | | + " | 821- 830 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 4 | 8 | 2.3 | 8.7 | 6 | 4 |11 | 9 | 1: 0.82 + 21 | 831- 840 | 8 | 3 | 5.4.5.6 | 5 | 7 | 2 | 4 | 6.7.8 | 3 | 8.7 | 7 | 3 | | | + " | 841- 850 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 3.2.4 | 8 | 3 | 7 | 7 | 3 |14 | 6 | 1: 0.43 + 22 | 851- 860 | 8 | 4.3 | 6 | 5 | 7 | 3.2 | 3.5.4 | 8 | 3 | 8.7 | 6 | 4 | | | + " | 861- 870 | 7.8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 4 | 8 | 3 | 8.7 | 3 | 7 | | | + " | 871- 880 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 |11 |19 | 1: 1.73 + 23 | 881- 890 | 8 | 3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | | | + " | 891- 900 | 8 | 3 | 7.6 | 6.5 | 7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | 9 |11 | 1: 1.22 + 24 | 901- 910 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | | | + " | 911- 920 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 7 | 3 |11 | 9 | 1: 0.82 + 26 | 921- 930 | 7.8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 8 | 2.2.3 | 8.7 | 4 | 6 | | | + " | 931- 940 | 8 | 3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 7 |13 | 1: 1.86 + 27 | 941- 950 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + 28 | 951- 960 | 8 | 3 | 7.6 | 6.5 | 5.4.7 | 2 | 5.5.4 | 8 | 3 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 29 | 961- 970 | 8 | 3 | 7.6 | 5 | 8.7 | 2 | 4 | 8 | 3 | 7 | 8 | 2 | 8 | 2 | 1: 0.25 + | | | | | | | | | | | | | | | | 30 | 971- 980 | 8 | 3 | 4.3.2.6 | 5 | {6.5.4.6 | 2 | 5.5.4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | {6.5.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | 31 | 981- 990 | 8 | 3 | 6 | 6.5 | 8.7 | 2 | 4 | 8 | 3 | 7 | 8 | 2 | 8 | 2 | 1: 0.25 + August | | | | | | | | | | | | | | | | + 2 | 991-1000 | 8 | 3 | 7.6 | 5 | 7 | 2 | {2.3.5.3 | 7.6.8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | | | {2.3.3.4 | | | | | | | | + | | | | | | | | | | | | | | | | 3 | 1001-1010 | 8 | 3 | 7.6 | 5 | 7 | 2 | 4 | 7.6.5.6.7.8 | 3 | 5.4.3.4.3.7 | 7 | 3 | | | + " | 1011-1020 | 8 | 2.3 | 5.6 | 3.2.3.6.5 | 7 | 2 | 5.4 | 9.8 | 2.1.3 | 7 | 4 | 6 |11 | 9 | 1: 0.82 + | | | | | | | | | | | | | | | | 4 | 1021-1030 | 7.8 | 3 | 5.4.3.7.6 | 6.5 | {6.5.6 | 3.2 | 5.4 | 8 | {2.2.4.2 | 8.7 | 2 | 8 | | | + | | | | | | {5.6.7 | | | | {4.2.3 | | | | | | + | | | | | | | | | | | | | | | | " | 1031-1040 | 7.8 | 3 | 6 | 6.4.3.6.5 | 7 | 2 | 3.5.4 | 8 | 2.3 | 8.7 | 5 | 5 | 7 |13 | 1: 1.86 + | | | | | | | | | | | | | | | | 5 | 1041-1050 | 8 | 3 | 6 | 2.3.2.6.5 | 8.7 | 2 | 4 | 8 | 2.2.4.3 | {8.8.6.8.4 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | {6.5.8.7 | | | | | + | | | | | | | | | | | | | | | | 6 | 1051-1060 | 8 | 3 | 6 | 4.2.6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | | | | | | 7 | 1061-1070 | 8 | 3 | 5.4.3.6 | 4.5 | {6.5.6.5 | 2 | 4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | {4.8.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | 9 | 1071-1080 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 7 |10 | 0 |10 | 0 | 1: 0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 1.2.3.4.5 | | | | | | 1.2.3.4 | 2.3.4.5 | | | | | + | | 5.6.7.8 | 2.3.4.5.6 | 6.7.8.9 | 5.6.7 | 1.2.3.4 | 4.5.6 | 2.3.4.5 | 1.2.3 | 5.6.7 | 6.7.8.9 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 10 | 1- 10 | 6.5.7 | 3.2.6.5 | 8 | 6 | 2.4.3 | 5 | 5.4 | 2 | 7.5.2.7.6 | 8 | 5 | 5 | 5 | 5 | 1: 1.00 + 11 | 11- 20 | 7 | 3.6.5 | 8 | 6 | 3 | 6.5 | 4 | 3.2 | 7.6 | 8 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | | | | | | | | | | | | | | {3.2.3.5.3 | | | | | | | | + 12 | 21- 30 | 7 | 2.2.6.5 | 7.8 | 6 | 3 | 5 | {2.5.3.2 | 2 | 6 | 8 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | | | {5.3.2.5 | | | | | | | | + | | | | | | | | {2.5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote 1: First choices correct by reason of aid from the experimenter +are not counted as correct (R) in the summary.] + +[Footnote *: Aided by experimenter.] + + +The method of choosing the first box at the right end and then the one +next to it developed in the case of all except two of the ten settings. +The time of appearance is worth noting. In setting 1, it failed to +appear; in setting 2, it developed early,--after about one hundred +trials; in setting 3, after about one hundred and fifty trials; in +setting 4, after about one hundred and fifty trials; in setting 5, after +about one hundred and seventy trials; in setting 6, after about one +hundred trials; in setting 7, after about fifty trials; in setting 8, it +never developed; in setting 9, after about fifty trials; and in setting +10, it developed very late,--after about four hundred and seventy +trials. + +This method of reaction, although inadequate, proved remarkably +persistent, and it is doubtful whether it had been wholly overcome at +the conclusion of the experiment. In the case of the series of trials +given on June 8, numbered 191 to 200, the method used was either that of +the first at the right and then the next, or direct choice of the right +box. + +Throughout the trials with this problem, the end boxes, numbers 1 and 9, +were avoided. This is at least partially explained by the fact that they +never existed, and obviously never could appear, in problem 2, as right +boxes. In trials 601 to 610, given on July 7, there occurred partial +return to the formerly established method of choosing the first door at +the right. This relapse was characteristic of what happened during the +many days which intervened between the definite appearance of this habit +and the final solution of the problem. + +Especially in connection with such relapses, Skirrl showed extreme +fatigue or ennui and often would refuse to work and simply sit before +the open doors yawning. This happened even when he was extremely hungry +and evidently eager enough for food. + +From July 12 on the hunger motive was increased by feeding the monkey +only in the apparatus and by so regulating the amount of food given in +each trial that he should obtain barely enough to keep him in good +physical condition. An increase in the number of correct choices +promptly resulted, and continued until on July 14 the ratio of choices +was 1 to .54. It appeared from these data that a relatively small number +of choices, say not more than ten a day, the rewards in connection with +which supplied the only food received by the animal, yielded most +favorable results. + +On July 16, the period of confinement in wrong boxes was increased to +sixty seconds, and it was so continued for a number of days. But in the +end, it became clear that the period of thirty seconds, combined with a +liberal reward in the shape of desired food and a single series of ten +trials per day, was most satisfactory. The detailed data of table 2 +indicate that at this time Skirrl was making his choices by memory of +the particular setting. + +Skirrl, on July 17 was evidently hungry and eager to locate food, but +seemingly unable to select the right box. In trial 5 (765th) of the +series, he was punished by confinement in box 8. When the doors were +unlocked in order that the entrance door might be raised to release him, +the lock-bar, sliding under the floor, made a slight grating noise, and +the instant the entrance door was opened, he jumped out excitedly. _He +made no outcry, but as soon as he was out of the box, sat down, and +taking up his right hind foot, examined it for a few seconds._ Having +apparently assured himself that nothing serious had happened, he went on +unconcernedly about his task. The presumption is that the sound of the +lock-bar, associated as it was with his painful experience in box 1, +revived the strongly affective experience of stepping on the nail. +Psychologically described, the sound induced an imaginal complex +equivalent to the earlier painful experience. The behavior seems to the +writer a most important bit of evidence of imagery in the monkey. +Finally, on August 9, after ten hundred and seventy trials, Skirrl +succeeded in choosing correctly in the ten trials of a series, and he +was therefore considered to have solved the problem of the second door +from the right end of the group. + +On the following day, he was given a control series with the settings +which are presented on page 19 and also at the bottom of table 2. In +this series he chose correctly five times,--in other words, as often +correctly as incorrectly. An analysis of the choices indicates, however, +that two of the five correct choices were made in box 8, which, as it +happened, had proved a peculiarly easy one for him throughout the +training, since from the first he tended to avoid door 9. Consequently, +it is only fair to conclude, from the results for this control series +and for those given on August 11 and 12, that the animal chose not on +the basis of anything remotely resembling a general idea of secondness +from the right end, but instead on the basis of gradually acquired modes +of reaction to the particular settings. This conclusion is strengthened +by the fact that he had failed to learn to react appropriately and +readily to most of the settings of the regular series. + +The curve which represents the course of the learning process in this +problem is presented in figure 19. For this and all other curves which +involve more than a single series of observations a day, the method of +construction was as follows: The first series for each day of training +is indicated on the curve by a dot, while the second or third series on +a given day, although space is allowed for them, are not so indicated. +Consequently, the form of the curve is determined chiefly by the first +series per day. The extreme irregularities of this curve are most +interesting and puzzling, as are also the variations in the daily ratios +of right to wrong first choices. Three times in the course of the +training, this ratio rose to 1 to 9, or higher. The causes for such +extreme variations are not easily enumerated, but a few of the most +obvious contributory causes are variations in the weather, especially +cloudiness or fogginess, which rendered the apparatus dark; variations +in the degree of hunger or eagerness for food; differences in the +activities of the animals in the cages outside of the laboratory +(sometimes they were noisy and distracted the subject), and finally, +differences in the physical fitness and attitude of the animal from day +to day. + +The more or less incidental behavior in connection with this experiment +more strongly than the statistical results of the work on problem 2 +indicate the existence of imagery. That ideas played a part in the +solution of the problem is probable, but at best they functioned very +ineffectively. The small number of methods used in the selection of the +right box, and the slight variations from the chief method, that of +choosing the first box at the right end and then the one next to it, +apparently justify Doctor Hamilton's characterization of this monkey as +defective. + + +[Illustration: FIGURE 19.--Error curves of learning for the solution of +problem 2 (second box from right end).] + + +_Problem 3. Alternately First at Left and First at Right_ + +Following the control series given in connection with problem 1, an +interval of rest lasting from August 12 to August 19 was allowed in +order that Skirrl might in part at least lose the effects of his +training and regain his customary interest in the apparatus by being +allowed to obtain food easily instead of by dint of hard labor,--labor +which was harder by far, apparently, than physical activity because it +demanded of the animal certain mental processes which were either +lacking or but imperfectly functional. The difficultness of the daily +tasks appears to be reliably indicated by the tendency to yawn. + +Systematic work on problem 3, which has been defined as alternately the +first door at the left and the first door at the right of the group, was +begun August 19, and for nine days a single series of ten trials per day +was given. Work then had to cease because of the experimenter's return +to Cambridge. + +The results of the work on this problem demand but brief analysis and +comment. The expected ratio of one right to four wrong choices per +series appears (see table 3) for the first series of trials, and _this +in spite of the fact that Skirrl had been trained for several weeks to +choose the second door from the right end_. One would ordinarily have +predicted a much larger number of incorrect choices. The right choices +were due to the monkey's strong tendency to go first to the first door +at the right and thence to the one next to it. Indeed in the series +given on August 24; this method was followed without variation. In other +words, in every one of the ten trials Skirrl entered first the box at +the extreme right end of the group. This necessarily resulted in as many +right as wrong first choices. Consequently, the ratio reads 1 to 1. But +the method was not adhered to, and at no time either before or after +that date did he succeed in equalling this achievement. There was, as a +matter of fact, no steady improvement, and so far as one may judge from +the records which were obtained, the course of events in the solution of +this problem would have been similar to those in problem 2. + + + +TABLE 3 + +Results for Skirrl, _P. irus_, in Problem 3 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + Date | No. of | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | R | W | R | W |Ratio of + | trials | 5.6.7 | 5.6.7 | 1.2.3.4.5.6 | 1.2.3.4.5.6 | 4.5.6.7.8 | 4.5.6.7.8 | 2.3.4.5 | 2.3.4.5 | 3.4.5.6.7.8.9| 3.4.5.6.7.8.9| | | | |R to W +________|___________|______________|______________|______________|______________|______________|______________|______________|______________|______________|______________|___|___|___|___|________ +August | | | | | | | | | | | | | | | | + | | | | {6.5.4.6 | | | | | | | {8.7.6.5 | | | | | + 19 | 1- 10 | 7.5 | 6.7 | {3.2.6.4 | 5.3.6 | {7.8.7.6 | 8 | 4.3.5.4.5.2 | 5 | 9.8.7.6.4.3 | {4.5.8.7 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | {3.6.1* | | {8.6.4 | | | | | {6.5.9* | | | | | + | | | | | | | | | | | | | | | | + | | | | {5.4.6.5 | | {8.7.6.7 | | | | | | | | | | + 20 | 11- 20 | 7.6.5 | {6.5.6.5 | {4.6.5.3 | 5.3.2.4.6 | {7.5.8.8 | 8 | 5.4.3.2 | 4.5 | 8.7.6.5.4.3 | {8.7.6.8.3 | 1 | 9 | 1 | 9 | 1:9.00 + | | | {7 | {2.5.1* | | {7.6.4* | | | | | {7.6.4.3.9 | | | | | + | | | | | | | | | | | | | | | | + | | | | {6.2.5.6 | | | | {5.3.5.4 | | | | | | | | + 21 | 21- 30 | 7.6.7.6.5 | 7 | {5.3.6.5 | 2.5.5.6 | 8.6.5.4 | 8 | {3.5.3.5 | 5 | {9.8.7.6 | 8.9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | {4.3.1* | | | | {4.3.2* | | {5.4.3 | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 23 | 31- 40 | 7.6.5 | 6.5.7 | {6.4.3.2 | 3.2.6 | 8.7.6.4 | 8 | 5.4.5.3.2 | 5.2 | 8.7.3 | 9 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | {5.6.2.1 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 24 | 41- 50 | 7.6.5 | 7 | {6.2.5 | 6 | {8.7.8.7 | 8 | 5.3.2 | 5 | {9.8.7.6 | 9 | 5 | 5 | 5 | 5 | 1:1.00 + | | | | {4.3.1 | | {5.7.5.4 | | | | {5.4.3 | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | {8.7.3.6 | | | | | + 25 | 51- 60 | 7.6.5 | 6.5.7 | 5.2.1 | 6 | 8.5.4 | 8 | 2 | 2.5 | 9.8.7.4.3 | {8.7.5.3 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | {8.7.9* | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 26 | 61- 70 | 7.6.5 | 6.5.7 | 1 | 2.1.6 | 8.7.6.4 | 8 | 2 | 3.2.5 | 9.8.7.5.3 | {3.6.8.3 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | {4.7.9 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | {8.6.3.3 | | | | | + 27 | 71- 80 | 7.6.5 | 7 | 2.1 | 1.5.6 | 8.7.6.4 | 8 | 2 | 5 | 9.8.7.6.3 | {7.5.3.8 | 4 | 6 | 4 | 6 | 1:1.50 + | | | | | | | | | | | {3.6.9* | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 81- 90 | 7.6.7.5 | 7 | 3.1 | 6 | 8.6.4 | 4.8 | 2 | 2.4.5 | 8.7.4.3 | 3.8.9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + + + + +2. Sobke, _Pithecus rhesus_ + + +_Problem 1. First at the Left End_ + +Sobke was somewhat afraid of the experimenter when the investigation was +undertaken, and instead of willingly coming out of his cage when the +door was raised, he often had to be coaxed out and lured into the +apparatus with food. Whereas Skirrl was frank and rather aggressive, +Sobke was stealthy in his movements, furtive, and evidently suspicious +of the experimenter as well as of the apparatus. He was perfectly safe +to approach, but would not permit anyone to touch him. After a few days, +he began to take food from the hands of the experimenter. + +Preliminary work to acquaint this monkey with the routine of the +experiment was begun on April 13. As in the case of Skirrl, he was lured +into the apparatus and was taught the route through the boxes to the +starting point by being allowed to obtain food once each day in each of +the nine boxes. The procedure was simple. The entrance door and the exit +door of a particular box were raised and the animal admitted to the +reaction-compartment and permitted to pass through the box whose doors +stood open, take its food, and return to the starting point. Sobke very +quickly learned the route perfectly and came to work steadily and +rapidly. After five days of preliminary work of this sort, he was so +thoroughly accustomed to the apparatus that it was evidently desirable +to begin with regular training experiments. + +The first series of trials was given on April 19. Both punishment and +reward were employed from the first. The punishment consisted of +confinement for thirty seconds in each wrong box, and the reward of a +small piece of banana, usually not more than a tenth of a medium sized +banana for each correct choice. The total time for the first series of +trials was fourteen minutes. This indicates that Sobke worked rapidly. +My notes record that he worked quickly though shyly, wasted almost no +time, made few errors of choice, and waited quietly during confinement +in the boxes. In this, also, he differed radically from Skirrl who was +restless and always tried to escape from confinement. + +Throughout the work on problem 1, punishment and reward were kept +constant. Everything progressed smoothly; there were no such +irregularities of behavior as appeared in the case of Skirrl, and +consequently the description of results is a relatively simple matter. +Sobke invariably chose the end boxes. His performance was in every way +superior to that of Skirrl. + +As previously, the detailed results are presented in tabular form (table +4). From this table it appears that, whereas the expected ratio of right +to wrong first choices for this problem is 1 to 2.5, the actual ratio +for Sobke's first series was 1 to .67. This surprisingly good showing is +unquestionably due to his marked tendency to choose the end box of a +group; and this tendency, in turn, may in part be the result of the +preliminary training, for during that only one box was open each time. +But, if the preliminary training were responsible for Sobke's tendency, +it should be noted that it had very different effect upon Skirrl, and, +as will be seen later, upon Julius. + +The results for the ten different settings of the doors for problem 1 as +they appear in table 4 are of interest for a number of reasons. In the +first place, the setting 1. 2. 3 appearing twice,--at the beginning of +the series and again at the end--yielded markedly different results in +the two positions. For whereas no mistakes were made in the case of +setting 1, there were fifty per cent of incorrect first choices for +setting 10. Again, satisfactory explanation is impossible. It is +conceivable that fatigue or approaching satiety may have had something +to do with the failures at the end of the series, but as a rule, as is +indicated by settings 1, 2, and 6, if correct choices were made at the +beginning, they continued throughout the day's work. + +In this problem, Sobke's improvement was steady and fairly rapid, and in +the eighth series, trials 71 to 80, only correct first choices appear. +Consequently, seventy trials were required for the solution of the +problem. This number is in marked contrast with Skirrl's one hundred and +thirty-two trials. + +Immediately following the first perfect series, Sobke was given two +series of control tests on April 28. Conditions were unfavorable, since +the day was stormy and the rain pattering on the sheet-iron roof made a +great din. Nevertheless, he worked steadily and well up to the sixth +trial, which was preceded by a slight delay because of the necessity of +refilling some of the food boxes. After this interruption, wrong choices +occurred in trial 6. And again after trial 9, there was brief +interruption, followed by wrong choices in trial 10. The ratio of right +to wrong choices for this first control series was therefore 1 to .25. + + + +TABLE 4 + +Results for Sobke, _P. rhesus_, in Problem 1 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | | | R | W | R | W | of + | trials | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + April | | | | | | | | | | | | | | | | + 19 | 1-10 | 1 | 8 | 3 | 9.7 | 6.2 | 6 | 7.5 | 4 | 9.7 | 1 | 6 | 4 | 6 | 4 | 1:0.67 + 20 | 11-20 | 1 | 8 | 3 | 7 | 2 | 6 | 7.5 | 8.4 | 9.9.7 | 1 | 7 | 3 | 7 | 3 | 1:0.43 + 21 | 21-30 | 1 | 8 | 4.3 | 9.7 | 2 | 6 | 5 | 8.4 | 7 | 1 | 7 | 3 | 7 | 3 | 1:0.43 + 22 | 31-40 | 1 | 8 | 3 | 7 | 6.2 | 6 | 6.5 | 4 | 7 | 3.1 | 7 | 3 | 7 | 3 | 1:0.43 + 23 | 41-50 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 9.7 | 3.1 | 8 | 2 | 8 | 2 | 1:0.25 + 24 | 51-60 | 1 | 8 | 3 | 9.7 | 2 | 6 | 5 | 4 | 7 | 2.1 | 8 | 2 | 8 | 2 | 1:0.25 + 26 | 61-70 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 3.1 | 9 | 1 | 9 | 1 | 1:0.11 + 27 | 71-80 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 |10 | 0 |10 | 0 | 1:0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | 2.3.4 | | | 1.2.3.4.5 | | | | | + | | 2.3.4 | 6.7.8.9 | 3.4.5 | 4.5.6.7.8.9 | 6.7.8.9 | 1.2.3.4.5 | 5.6.7.8 | 3.4.5.6.7.8 | 5.6.7 | 6.7.8.9 | | | | | + | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ | | | | + 28 | 1-10 | 2 | 6 | 3 | 4 | 6 | 5.4.1 | 2 | 3 | 5 | 5.4.2.1 | 8 | 2 | | | + " | 11-20 | 2 | 6 | 3 | 4 | 6 | 2.1 | 2 | 3 | 5 | 1 | 9 | 1 |17 | 3 | 1:0.18 + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + + + +Six minutes after completion of the first control series, a second was +given under slightly more favorable conditions, and in this only a +single wrong choice occurred, in that box 2 was first chosen in trial 6 +instead of box 1. From the results of these two control series, it is +evident that Sobke's solution of problem 1 is reasonably adequate. He is +easily diverted or disturbed in his work by any unusual circumstances, +but so long as everything goes smoothly, he chooses with ease and +certainty. Whether it is fair to describe the behavior as involving an +idea of the relation of the right box to the other members of the group +would be difficult to decide. I hesitate to infer definite ideation from +the available evidence, but I strongly suspect the presence of images +and relatively ineffective or inadequate ideation. + +It is perfectly evident that Sobke is much more intelligent than Skirrl. +In practically every respect, he adapted himself more quickly to the +experimental procedure and progressed more steadily toward the solution +of the problem than did Skirrl. The contrast in the learning processes +of the two monkeys could scarcely be better exhibited than by the curves +of learning which are presented in figure 18. The first, that for Sobke, +is surprisingly regular; the second, that for Skirrl, is quite as +surprisingly irregular. These results correlate perfectly with the +steadiness and predictability of the former's responses and the +irregularity and erraticness of the latter's. + + +_Problem 2. Second from the Right End_ + +On the completion of problem 1 Sobke was in perfect condition, as to +health and training, for experimental work. He had come to work quietly, +fairly deliberately, and very steadily. His timidity had diminished and +he would readily come to the experimenter for food, although still he +was somewhat distrustful at times and became timid when anything unusual +occurred in the apparatus. + +As preparation for problem 2, a break in regular experimentation +covering four days followed the control series of problem 1. On each of +these four days the monkey was allowed to get food once from each of the +nine boxes, both doors of a given box being open for the trial and all +other doors closed. For this feeding experiment, the doors were opened +in irregular order, and this order was changed from day to day. + +Systematic work with problem 2 began on May 3, with punishment of thirty +seconds for mistakes and a liberal reward of food for each success. +Early in the series of trials it was discovered that Sobke was likely to +become discouraged and waste a great deal of time unless certain aid +were given by the experimenter. On this account, after the first two +trials, the method was adopted of punishing the animal by confinement +for the first ten mistakes in a trial, and of then, if need be, +indicating the right box by slightly and momentarily raising the exit +door. Every trial in which aid was thus given by the experimenter is +indicated in table 5 by an asterisk following the last choice. In the +first series of trials for this problem, aid had to be given in seven of +the ten trials, and even so the series occupied seventy-one minutes. It +is possible that had no aid been given, the work might have been +continued successfully with a smaller number of trials than ten per day. +But under the circumstances it seemed wiser to avoid the risk of +discouraging and thus spoiling the animal for use in the experiment. It +should be stated, also, that it proved impossible to adhere to the +period of thirty seconds as punishment in this series. For the majority +of the wrong choices confinement of not more than ten seconds was used. + +For the second series, given on May 4, the conditions were unfavorable +in that it was dark and rainy, and the noise of the rain on the roof +frightened Sobke. He refused to work after the fourth trial, and the +series had to be completed on the following day. The total time required +for this series was seventy-eight minutes. + +The work on May 6 was distinctly better, and the animal's behavior +indicated, in a number of trials, definite recognition of the right +door. He might, for example, make a number of incorrect choices, then +pause for a few seconds to look steadily at the doors, and having +apparently found some cue, run directly to the right box. No aid from +the experimenter was needed in this series. + +On the following day improvement continued and the animal's method of +choosing became definite and fairly precise. He was deliberate, quiet, +and extremely business-like. The time for the series was thirty-one +minutes. + +The period of punishment was increased on May 12 to thirty seconds. +Previously, for the greater number of the trials, it had been ten to +fifteen seconds. This increase apparently did not disturb the monkey, +for he continued to work perfectly throughout the series, although +making many mistakes in spite of deliberate choices and the refusal of +certain boxes in each trial. + +An interesting and significant incident occurred on May 13 when at the +conclusion of trial 5, Doctor Hamilton came into the experiment room for +a few minutes. Sobke immediately stopped working, and he could not be +induced to make any choices until Doctor Hamilton had left the room. +This well indicates his sensitiveness to his surroundings, and his +inclination to timidity or nervousness even in the presence of +conditions not in themselves startling. + +Work was continued thus steadily until May 28 when, because of the +failure of the animal to improve, it seemed wise to increase the period +of confinement as punishment to sixty seconds. In the meantime, it had +sometimes been evident that Sobke was near to the solution of his +problem. He would often make correct choices in three or four trials in +succession and then apparently lose his cue and fail utterly for a +number of trials. + +After June 1, in order to hasten the solution of the problem, two series +per day were given. In some instances the second series was given almost +immediately after the first, while in others an interval of an hour or +more intervened. It was further found desirable to give Sobke all of his +food in the apparatus. When the rewards obtained in the several trials +did not satisfy his hunger, additional food was presented, on the +completion of the series of experiments, in one or more of the food +cups. On days marked by unwillingness or refusal to work, very little +food was given. Thus, the eagerness of the monkey to locate the right +box was increased and, as a matter of observation, his deliberateness +and care in choice increased correspondingly. Sixty seconds punishment +was found satisfactory, and it was therefore continued throughout the +work on this problem. + +It was evident, on June 9, from the behavior of the monkey as well as +from the score, that the perfect solution of the problem was near at +hand. This fact the experimenter recorded in his daily notes, and sure +enough, on the following day Sobke chose correctly throughout the series +of ten trials. The time for this series was only ten minutes. The +choices were made deliberately and readily. + +An analysis of the data of table 5 reveals five methods or reactive +tendencies which appeared more or less definitely in the following +order: (a) Choice of first box at the left, because of experience in +problem 1. This tendency was very quickly suppressed by the requirements +in connection with problem 2. Indeed one of the most significant +differences which I have discovered between the behavior of the primates +and that of other mammals is the time required for the suppression of +such an acquired tendency. The monkey seems to learn almost immediately +that it is not worth while to persist in a tendency which although +previously profitable no longer yields satisfaction, whereas in the +crow, pig, rat, and ring dove, the unprofitable mode of response tends +to persist during a relatively large number of trials. (b) The tendency +to choose, first, a box near the left end of the group, to go from that +to the box at the extreme right end of the group, thence to the one next +in order, which was, of course, the right box. This tendency appears +fairly clearly from May 7th on. (c) The box at the extreme right was +first chosen and then the one next to it. For example, in setting 2, box +4 would be chosen first, then box 3. Or, if this did not occur, the +method previously described under (b) was likely to be employed, as for +example, in setting 8, where such choices as 7.6.5.1.8 appear. (d) In +certain series there appeared a marked preference for a particular box, +usually box 3 (see results for May 24). This was doubtless due in a +measure, if not wholly, to the fact that box 3 was the right box twice +in each series of ten settings. But it should be added that the same is +true of box 7, for which no preference was manifested at any time. (e) +Direct choice of the right box. + +The five reactive methods or tendencies enumerated above roughly +appeared in the order named, but there were certain irregularities and +the order as well as the time of appearance varied somewhat from setting +to setting. In general, method c was the most frequently used prior to +the development of method e, the direct choice of the right box. + + + +TABLE 5 + +Results for Sobke, _P. rhesus_, in Problem 2 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | 1.2.3.4.5 | | | R | W | R | W | of + | trials | 7.8.9 | 1.2.3.4 | 2.3.4.5.6.7 | 1.2.3.4.5.6 | 4.5.6.7.8 | 1.2.3 | 2.3.4.5 | 6.7.8.9 | 1.2.3.4 | 3.4.5.6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + May | | {7.7.9.7.7 | {1.2.4.1 | {3.2.7.2 | {4.6.1.6 | | {3.1.3.3 | | | {4.1.4.1 | {3.8.3.3 | | | | | + 3 | 1-10 | {9.7.9.7.9 | {1.4.1.1 | {7.7.7.5 | {1.6.1.1 | 5.8.6.7 | {3.3.1.1 | 3.5.4 | 9.1.8 | {4.1.4.2 | {3.8.6.3 | 0 |10 | 0 |10 | 0:10.00 + | | {7.9.9.7.8* | {4.3* | {2.7.6* | {1.3.5* | | {1.1.2* | | | {1.4.3* | {8.3.7* | | | | | + | | | | | | | | | | | | | | | | + | | | | {4.7.2.7 | | (8.8.4.8 | | {5.5.5.5 | {9.5.5.9 | | | | | | | +4 and 5 | 11-20 | (7.9.7.9.9 | 1.4.1.3 | {2.7.3.2 | 1.6.5 | {8.8.4.8 | {3.3.1.1.3 | {5.5.5.3 | {7.1.6.6 | {4.4.4.4 | {8.8.6.8 | 0 |10 | 0 |10 | 0:10.00 + | | {9.7.7.9.8 | | {7.2.6* | | {4.8.7* | {3.3.1.2 | {5.5.4* | {6.5.8* | {4.4.4.3 | {8.7 | | | | | + | | | | | | | | | | | | | | | | + 6 | 21-30 | 9.7.9.7.8 | 4.3 | 7.2.3.7.6 | {6.3.1.6 | 6.8.7 | 3.1.2 | {5.3.5.3 | {6.9.4.6.1 | {4.1.2.4 | {3.4.5.3 | 0 |10 | 0 |10 | 0:10.00 + | | | | | {6.2.6.5 | | | {2.4 | {7.9.7.8 | {4.2.3 | {8.6.7 | | | | | + | | | | | | | | | | | | | | | | + 7 | 31-40 | 7.9.7.8 | 1.4.3 | 2.7.6 | 3.5 | 4.8.7 | 3.1.2 | 3.2.3.5.4 | 8 | 4.3 | 5.8.3.4.8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + 8 | 41-50 | 7.9.7.8 | (4.2.4.1.4 | 6 | 5 | 6.5.4.8.7 | {3.1.3.1 | 5.3.5.4 | {7.4.2.1 | {4.2.4.1 | 5.3.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | {4.2.2.4.3 | | | | {3.1.3.2 | | {9.8 | {4.3 | | | | | | + | | | | | | | | {5.3.5.3 | | | | | | | | + 10 | 51-60 | 7.7.8 | 3 | 7.3.2.7.6 | 6.4.6.5 | (6.4.8.5 | 3.1.3.2 | {2.5.3.5 | 5.9.8 | 4.2.4.3 | {6.5.4 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | {4.8.7 | | {2.5.4 | | | {3.8.7 | | | | | + | | | | | | | | | | | | | | | | + 11 | 61-70 | 7.9.7.8 | 1.4.3 | 4.3.2.7.6 | 6.5 | {5.4.8.6 | 3.2 | 5.4 | 6.5.2.3.1.8 | 3 | 6.5.3.8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | {5.4.8.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + 12 | 71-80 | 7.9.8 | 3 | 7.3.2.7.6 | 6.5 | 5.4.8.7 | 1.2 | 5.4 | 8 | 4.3 | 5.4.3.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + 13 | 81-90 | 7.8 | 4.3 | 3.7.6 | 6.5 | 8.7 | 1.3.2 | 2.5.2.5.4 | 7.6.5.9.8 | 3 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | | | | | | | | | + | | | | | | | | | | {1.2.1.2.2 | | | | | | + 14 | 91-100 | 7.8 | 3 | 6 | 5 | 6.5.4.7 | 1.3.2 | 5.4 | 9.8 | {1.4.2.2.1 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | {4.1.4.3 | | | | | | + | | | | | | | | | | | | | | | | + 15 | 101-110 | 7.8 | 3 | 7.6 | 5 | 5.4.5.7 | 3.2 | 5.4 | 8 | 2.1.3 | 8.8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | | | | | | | | + 17 | 111-120 | 7.8 | 4.3 | 7.6 | {2.1.2.1.2 | 8.7 | 3.2 | 5.4 | 7.6.5.1.8 | 3 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | {1.3.2.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 18 | 121-130 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.6.5.2.8 | 3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | | | | | | | | + | | | | | | | | {5.3.2.5.3 | | | | | | | | + | | | | | | | | {2.5.2.5.3 | | | | | | | | + 19 | 131-140 | 8 | 3 | 3.2.6 | 5 | 7 | 3.2 | {5.5.2.5.5 | 7.6.9.8 | 3 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | {3.2.5.5.3 | | | | | | | | + | | | | | | | | {2.5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | + 20 | 141-150 | 7.8 | 3 | 3.2.7.6 | 6.5 | 5.4.7 | 3.2 | 3.2.5.4 | 6.5.4.3.8 | 3 | 7 | 3 | 7 | 3 | 7 | 1: 2.33 + 21 | 151-160 | 7.8 | 3 | 5.7.5.3.7.6 | 5 | 7 | 3.2 | 5.3.5.2.5.4 | 7.6.5.9.8 | 3 | 6.4.3.8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 22 | 161-170 | 7.8 | 3 | 7.6 | 3.2.6.5 | 7 | 3.2 | {5.2.5.3 | 7.6.5.8 | 3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | {2.5.4 | | | | | | | | + | | | | | | | {3.1.3 | | | | | | | | | + 24 | 171-180 | 8 | 3 | {3.2.7.5 | {3.6.4 | 8.7 | {1.3.3 | {3.5.4 | 8 | {4.4.2.1 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | {7.3.6 | {3.6.5 | | {3.2 | | | {4.3 | | | | | | + | | | | | | | | | | | | | | | | + 25 | 181-190 | 7.9.7.9.8 | 3 | 3.7.6 | 5 | 8.7 | 3.2 | 5.4 | 4.3.8 | 4.3 | 8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + 26 | 191-200 | 8 | 3 | 6 | 5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 5 | 5 | 5 | 5 | 1: 1.00 + 27 | 201-210 | 7.9.8 | 3 | 3.2.7.6 | 5 | 8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + 28 | 211-220 | 8 | 3 | 3.7.6 | 4.3.2.6.5 | 8.7 | 3.2 | 5.4 | 7.6.5.9.8 | 3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + 29 | 221-230 | 7.8 | 3 | 5.4.3.7.6 | 6.5 | 7 | 2 | 3.2.5.4 | 7.6.5.8 | 3 | 3.8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + 31 | 231-240 | 7.7.8 | 3 | 3.7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 9.8 | 3 | 3.7 | 2 | 8 | 2 | 8 | 1: 4.00 + June | | | | | | | | | | | | | | | | + 1 | 241-250 | 8 | 3 | 5.4.7.6 | 3.2.6.5 | 8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + " | 251-260 | 7.9.8 | 3 | 3.7.6 | 5 | 6.5.4.8.7 | 3.2 | 4 | 5.4.3.8 | {4.2.1.4 | 7 | 4 | 6 | 8 |12 | 1: 1.50 + | | | | | | | | | | {2.4.4.3 | | | | | | + | | | | | | | | | | | | | | | | + 2 | 261-270 | 7.8 | 3 | 6 | 3.2.6.5 | 7 | 3.2 | 3.4 | 8 | 3 | 6.5.3.8.7 | 5 | 5 | | | + " | 271-280 | 7.8 | 3 | 3.7.6 | 3.6.5 | 7 | 3.2 | 5.4 | 7.6.5.4.3.8 | 3 | 7 | 4 | 6 | 9 |11 | 1: 1.22 + 3 | 281-290 | 7.8 | 3 | 7.6 | 3.6.5 | 8.7 | 3.2 | 4 | 7.8 | 3 | 7 | 4 | 6 | | | + " | 291-300 | 9.8 | 3 | 3.6 | 4.3.6.5 | 8.7 | 2 | 3.5.4 | 7.6.5.9.8 | 3 | 8.7 | 3 | 7 | 7 |13 | 1: 1.86 + 4 | 301-310 | 8 | 3 | 7.6 | 3.4.3.6.5 | 8.7 | 2 | 3.2.5.4 | 7.6.5.8 | 3 | 3.8.7 | 4 | 6 | | | + " | 311-320 | 8 | 3 | 5.4.7.6 | 3.2.6.5 | 7 | 2 | 3.2.5.4 | 8 | 3 | 7 | 7 | 3 |11 | 9 | 1: 0.82 + 5 | 321-330 | 8 | 3 | 6 | 4.6.5 | 7 | 2 | 3.5.4 | 8 | 4.3 | 7 | 7 | 3 | | | + " | 331-340 | 8 | 3 | 7.4.7.6 | 3.2.4.6.5 | 7 | 3.2 | 3.5.4 | 8 | 3 | 7 | 6 | 4 |13 | 7 | 1: 0.54 + 7 | 341-350 | 8 | 3 | 7.6 | 5 | 8.7 | 1.3.1.2 | 3.5.4 | 8 | 3 | 7 | 6 | 4 | | | + " | 351-360 | 8 | 3 | 7.6 | 5 | 8.7 | 2 | 3.5.4 | 8 | 3 | 7 | 7 | 3 |13 | 7 | 1: 0.54 + 8 | 361-370 | 7.8 | 3 | 4.7.6 | 3.5 | 8.7 | 2 | 3.4 | 9.8 | 3 | 7 | 4 | 6 | | | + | 371-380 | 8 | 3 | 7.6 | 3.4.4.3.5 | 8.7 | 3.2 | 3.4 | 8 | 3 | 7 | 5 | 5 | 9 |11 | 1: 1.22 + 9 | 381-390 | 8 | 3 | 6 | 4.2.1.5 | 7 | 2 | 3.4 | 8 | 3 | 8.7 | 7 | 3 | | | + " | 391-400 | 8 | 3 | 6 | 5 | 7 | 2 | 3.4 | 8 | 3 | 7 | 9 | 1 |16 | 4 | 1: 0.25 + 10 | 401-410 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 7 |10 | 0 |10 | 0 | 1: 0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 1.2.3.4.5 | | | | | | 1.2.3.4 | 2.3.4.5 | | | | | + | | 5.6.7.8 | 2.3.4.5.6 | 6.7.8.9 | 5.6.7 | 1.2.3.4 | 4.5.6 | 2.3.4.5 | 1.2.3 | 5.6.7 | 6.7.8.9 | | | | | + | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 11 | 1-10 | 6.7 | 3.5 | 8 | 6 | 3 | 5 | 3.4 | 3.2 | 7.7.2.6 | 8 | 5 | 5 | 5 | 5 | 1: 1.00 + 12 | 11-20 | 7 | 3.6.6.2.5 | 8 | 6 | 3 | 4.5 | 4 | 2 | 7.6 | 8 | 7 | 3 | 7 | 3 | 1: 0.43 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +Examination of table 5 indicates that some of the settings proved very +easy for Sobke; others, extremely difficult. Consequently, the number of +methods which were tried and rejected for a given setting varies from +two to five. Setting 2 proved a fairly simple one, and after the +inhibition of the tendency to choose the first box at the left, the only +definite tendency to appear was that of choosing the first box at the +right, and then the one next to it. After one hundred and thirty trials, +this method suddenly gave place to direct choice of the right box, and +during the following twenty-eight series, no error occurred for this +setting. Setting 4, on the contrary, proved extremely difficult, and a +variety of methods is more or less definitely indicated by the records. + +It is needless to lengthen the description by analyzing the data for +each setting, since the reader by carefully scanning the columns of data +in table 5 may observe for himself the various tendencies and their +mutual relations. + +Sobke's curve of learning (figure 19) in problem 2, is extremely +irregular, as was that of Skirrl. Similar irregularities appear in the +daily ratios of right to wrong first choices presented in the last +column of table 5. Most of these irregularities were due, I have +discovered, to unfavorable external conditions. Thus, dark rainy days +and disturbing noises outside the laboratory were obviously conditions +of poor work. + +On the day following the final and correct series for problem 2, a +control series was given. In this Sobke seemed greatly surprised by the +new situations which presented themselves. Repeatedly he exhibited +impulses to enter the box which would have been the correct one in the +regular series of settings. He frequently inhibited such impulses and +chose correctly, but at other times he reacted quickly and made +mistakes. It was evident from his behavior that he was not guided by +anything like a definite idea of the relation of the right box to the +other members of the group. + +In a second control series given on the following day, June 12, +confusion appeared, but less markedly. For the first setting, a correct +choice was made with deliberation. For the second setting, box 3 was +immediately chosen, as should have been the case in the regular series +of settings. Sobke seemed confused when he emerged from this box and had +difficulty in locating the right one. Then followed direct correct +choices for settings 3, 4, and 5. For setting 6, there is recorded a +deliberately made wrong choice, and so on throughout the series, the +choices being characterized by deliberateness and definite search for +the right box. Uncertainty was plainly indicated, and in this the +behavior of the animal differed markedly from that in the concluding +series of the regular experiment. + +It seems safe to conclude from the results of these control series that +Sobke has no free idea of the relation of secondness from the right and +is chiefly dependent upon memory of the particular settings for cues +which lead to correct choice. + + +_Problem 3. Alternately First at Left and First at Right_ + +For four successive days after the last control series in connection +with problem 2, Sobke was merely fed in the apparatus according to +previous description (p. 43). He exhibited a wonderfully keen appetite +and was well fed during this interval between problems. + +The method of experimentation chosen for problem 3 in the light of +previous experience was that of confining the monkey for a short time, +ten to fifteen seconds, in the wrong box, in each of the first ten +mistakes for a given trial, and of then aiding him to find the right box +by the slight and momentary raising of the exit door. Aid proved +necessary in a few of the trials during the first four days. Then he +worked independently. As work progressed it was found possible and also +desirable to increase the period of confinement, and in the end, sixty +seconds proved satisfactory. It was also thought desirable to increase +the number of trials per day from a single series during the early days +to two or even three series from June 29 on. Often three series could be +given in succession without difficulty. During the early trials on this +problem Sobke worked remarkably well, but later his willingness +diminished, evidently because of his failure readily to solve the +problem, and it became extremely difficult to coax him into the +apparatus. On days when he entered only reluctantly and as it seemed +against his will, he was likely to be nervous, erratic, and often slow +in making his choices, but above all he tended to waste time by not +returning to the starting point, preferring rather to loiter in the +alleyways or run back and forth. + + + +TABLE 6 + +Results for Sobke, _P. rhesus_, in Problem 3 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | 3.4.5.6 | 3.4.5.6 | R | W | R | W | of + | trials | 5.6.7 | 5.6.7 | 1.2.3.4.5.6 | 1.2.3.4.5.6 | 4.5.6.7.8 | 4.5.6.7.8 | 2.3.4.5 | 2.3.4.5 | 7.8.9 | 7.8.9 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + June | | | | | {3.1.2.1 | {7.8.7.8 | | | | {9.8.7.9 | | | | | | + 17 | 1--10 | {6.6.7.6 | 5.7 | {4.4.3.5.4 | {4.4.2.1 | {8.8.7.8 | 8 | 2 | 3.2.5 | {8.7.6.9 | 3.8.9 | 2 | 8 | 2 | 8 | 1:4.00 + | | {6.5 | | {5.4.2.1 | {5.4.6* | {7.7.4* | | | | {8.7.3* | | | | | | + | | | | | | | | | | | | | | | | + | | | | {3.4.2.5 | | {8.7.7.5 | | | | | | | | | | + 18 | 11--20 | 6.6.6.5 | 5.7 | {4.5.6.4 | 3.1.4.3.6 | {8.8.7.8 | 8 | 3.2 | (3.4.2.4 | 9.8.8.7.3 | 8.6.9 | 1 | 9 | 1 | 9 | 1:9.00 + | | | | {2.3.1* | | {7.8.4* | | | {4.5 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | {3.6.5.4 | | {8.8.7.7 | | | | | | | | | | + 19 | 21--30 | 6.5 | 7 | {2.5.2.6 | 3.6 | {7.8.8.8 | 8 | 4.3.2 | {3.2.4.2 | {9.8.7.9.7 | 9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | {3.5.1* | | {8.4 | | | {2.5 | {6.5.4.3 | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | (8.8.8.8 | | | | {9.9.8.9 | | | | | | + 21 | 31--40 | 6.5 | 5.6.5.7 | {3.5.4.6 | 2.5.3.6 | {7.8.3.8 | 8 | 4.2 | 2.5 | {9.5.9.9 | 9 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | {4.3.5.1 | | {8.7.4* | | | | {9.9.3* | | | | | | + | | | | | | | | | | | | | | | | + 22 | 41--50 | 7.6.5 | 6.5.5.7 | 1 | 2.1.3.6 | {8.8.8.8 | 8 | 2 | 2.3.2.2.5 | {9.8.9.8.7 | 9 | 4 | 6 | 4 | 6 | 1:1.50 + | | | | | | {7.8.4 | | | | {6.5.9.3 | | | | | | + | | | | | | | | | | | | | | | | + 23 | 51--60 | 5 | 6.5.7 | 1 | {1.2.1.1 | 8.5.4 | 8 | 5.4.2 | 2.4.2.5 | {9.8.4.9 | 9 | 4 | 6 | 4 | 6 | 1:1.50 + | | | | | {3.2.6 | | | | | {7.3 | | | | | | + | | | | | | | | | | | | | | | | + 24 | 61--70 | 7.6.5 | 7 | 2.3.1 | 2.1.5.4.2.6 | 8.7.8.4 | 8 | 4.5.4.3.2 | 2.2.4.5 | 9.7.6.8.3 | 9 | 3 | 7 | 3 | 7 | 1:2.33 + 25 | 71--80 | 6.5 | 5.7 | 3.1 | 6 | 8.5.4 | 8 | 2 | 3.2.5 | 9.8.7.3 | 3.9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | | | | | | + 26 | 81--90 | 7.7.6.5 | 6.5.7 | 3.1 | {1.4.1.1 | 8.4 | 8 | 5.4.2 | 2.5 | 9.8.9.6.3 | 9 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | | {5.1.6 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 91--100 | 7.6.5 | 7 | 1 | 1.2.4.6 | 8.4 | 8 | 2 | 3.2.2.2.5 | 9.8.8.7.9.3 | 9 | 5 | 5 | 5 | 5 | 1:1.00 + | | | | | | | | | | | | | | | | + 29 | 101--110 | 7.6.5 | 5.7 | 1 | {1.1.5.3 | 8.4 | 8 | 2 | 4.2.5 | {9.9.8.9.4 | 9 | 4 | 6 | | | + | | | | | {2.1.6 | | | | | {9.7.6.3 | | | | | | + | | | | | | | | | | | | | | | | + " | 111--120 | 6.5 | 6.5.7 | 1 | 2.1.1.3.6 | 8.5.4 | 8 | 2 | 3.2.5 | 9.8.7.6.4.3 | 9 | 4 | 6 | 8 |12 | 1:1.50 + 30 | 121--130 | 5 | 6.5.6.5.5.7 | 1 | 3.1.6 | 8.7.6.8.5.4 | 8 | 2 | 4.2.4.2.5 | 9.3 | 9 | 5 | 5 | | | + " | 131--140 | 5 | 7 | 1 | 2.3.6 | 8.5.6.4 | 8 | 2 | 5 | 9.8.3 | 3.9 | 6 | 4 |11 | 9 | 1:0.82 + July | | | | | | | | | | | | | | | | + 1 | 141--150 | 5 | 7 | 1 | 1.6 | 8.7.4 | 8 | 2 | 3.2.5 | 9.8.6.9.3 | 9 | 6 | 4 | | | + " | 151--160 | 5 | 7 | 1 | 2.5.3.6 | 8.4 | 8 | 2 | 2.5 | 9.3 | 8.8.7.5.4.9 | 5 | 5 |11 | 9 | 1:0.82 + 2 | 161--170 | 6.5 | 7 | 1 | 2.6 | 8.4 | 8 | 2 | 3.5 | 9.3 | 9 | 5 | 5 | 5 | 5 | 1:1.00 + 3 | 171--180 | 6.5 | 7 | 1 | 1.5.6 | 8.4 | 8 | 2 | 3.5 | 9.3 | 9 | 5 | 5 | | | + " | 181--190 | 5 | 7 | 1 | 4.6 | 8.6.4 | 8 | 2 | 5 | 9.8.4.8.5.3 | 9 | 7 | 3 |12 | 8 | 1:0.67 + 5 | 191--200 | 6.5 | 5.7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 9.5.3 | 9 | 6 | 4 | | | + " | 201--210 | 5 | 7 | 6.1 | 2.6 | 8.6.4 | 8 | 5.3.5.4.3.2 | 4.3.5 | 9.7.3 | 9 | 4 | 6 |10 |10 | 1:1.00 + | | | | | | | | | | | | | | | | + 6 | 211--220 | 5 | 5.7 | 1 | 2.6 | 8.6.4 | 8 | 2 | 4.3.5 | 9.3 | {5.4.8.3 | 4 | 6 | | | + | | | | | | | | | | | {8.5.4.9 | | | | | + | | | | | | | | | | | | | | | | + " | 221--230 | 5 | 7 | 1 | 5.3.6 | 8.6.8.4 | 8 | 4.2 | 3.2.5 | 9.3 | 9 | 5 | 5 | 9 |11 | 1:1.22 + 7 | 231--240 | 5 | 7 | 1 | 2.6 | 8.4 | 7.4.8 | 2 | 4.3.5 | 8.3 | 9 | 5 | 5 | | | + " | 241--250 | 5 | 7 | 2.6.3.5.1 | 6 | 8.4 | 8 | 2 | 5 | 9.3 | 9 | 7 | 3 | | | + | | | | | | | | | | | | | | | | + | | | | {2.6.2.6.4 | | | | | | | | | | | | + " | 251--260 | 5 | 7 | {6.3.2.6 | 6 | 8.4 | 8 | 2 | 5 | 9.5.3 | 9 | 7 | 3 |19 |11 | 1:0.58 + | | | | {5.4.3.1 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 8 | 261--270 | 7.5 | 7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 8.3 | 8.5.4.9 | 5 | 5 | | | + " | 271--280 | 5 | 7 | 2.6.4.6.1 | 6 | 8.5.8.4 | 7.4.8 | 5.5.3.5.2 | 5 | 9.3 | 9 | 5 | 5 |10 |10 | 1:1.00 + | | | | | | | | | | | | | | | | + 9 | 281--290 | 5 | 5.7 | 1 | 6 | 8.4 | 8 | 2 | 2.5 | 8.3 | {7.3.8.6.8 | 5 | 5 | | | + | | | | | | | | | | | {4.7.3.9 | | | | | + | | | | | | | | | | | | | | | | + " | 291--300 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 9.3 | 9 | 8 | 2 | | | + " | 301--310 | 5 | 7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 9.5.3 | 9 | 7 | 3 |20 |10 | 1:0.50 + 10 | 311--320 | 5 | 7 | 1 | 6 | 8.4 | 7.4.8 | 2 | 5 | 9.3 | 9 | 7 | 3 | | | + " | 321--330 | 5 | 7 | 1 | 5.2.6 | 8.7.4 | 8 | 2 | 5 | 9.3 | 9 | 7 | 3 |14 | 6 | 1:0.43 + 12 | 331--340 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 8.3 | 9 | 8 | 2 | | | + " | 341--350 | 5 | 7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 9.3 | 9 | 7 | 3 |15 | 5 | 1:0.33 + 13 | 351--360 | 5 | 5.7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 3 | 9 | 7 | 3 | | | + " | 361--370 | 5 | 7 | 6.1 | 6 | 4 | 8 | 5.2 | 3.2.5 | 9.3 | 9 | 6 | 4 |13 | 7 | 1:0.54 + 14 | 371--380 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 7.4.3.9 | 8 | 2 | | | + " | 381--390 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 9.3 | 4.7.3.9 | 7 | 3 |15 | 5 | 1:0.33 + 15 | 391--400 | 5 | 5.5.7 | 1 | 3.6 | 8.4 | 8 | 3.2 | 5 | 8.3 | 9 | 5 | 5 | | | + " | 401--410 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 7.3 | 6.5.3.9 | 7 | 3 |12 | 8 | 1:0.67 + 16 | 411--420 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 9 | 9 | 1 | | | + " | 421--430 | 5 | 7 | 1 | 6 | 4 | 8 | 2 | 5 | 3 | 4.7.4.9 | 9 | 1 | | | + " | 431--440 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 5.7.3.9 | 8 | 2 |26 | 4 | 1:0.15 + 17 | 441--450 | 5 | 7 | 1 | 6 | 4 | 4.8 | 2 | 5 | 4.3 | 3.5.9 | 7 | 3 | | | + " | 451--460 | 5 | 7 | 1 | 3.6 | 4 | 5.4.8 | 2 | 5 | 9.3 | 9 | 7 | 3 | | | + " | 461--470 | 5 | 7 | 1 | 6 | 4 | 8 | 2 | 5 | 3 | 9 |10 | 0 |24 | 6 | 1:0.25 + 19 | 471--480 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 9 | 9 | 1 | 9 | 1 | 1:0.11 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + | | 5.6 | 5.6 | 4.5.6.7.8.9 | 4.5.6.7.8.9 | 1.2.3.4.5 | 1.2.3.4.5 | 2.3.4.5.6.7 | 2.3.4.5.6.7 | 3.4.5.6.7.8 | 3.4.5.6.7.8 | | | | | + | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 19 | 1--10 | 5 | 6 | 4 | 9 | 1 | 5 | 3.7.2 | 7 | 3 | 8 | 9 | 1 | 9 | 1 | 1:0.11 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +The data of table 6 indicate for this problem only three pronounced +reactive tendencies: (a) As the initial tendency, the choice of the +second box from the right end. This proved surprisingly weak, in view of +the animal's long training on problem 2, and it disappeared quickly. (b) +Choice of the end boxes, and (c) direct choice of the right box. + +For this, as for the other problems, extreme differences in method and +in time and degree of success appear for the different settings. Thus, +while settings 1, 2, 3, 6, 7, and 10 proved to be easy, settings 4, 5, +8, and 9 were evidently more difficult. + +[Illustration: FIGURE 20.--Error curve of learning for the solution of +problem 3 (alternately the first box at the left end and the first at +the right end) by Sobke.] + +From the first this problem promised to be much easier for Sobke than +problem 2, and although the actual number of trials necessary for the +solution is greater by sixty for problem 3 than for problem 2, +comparison of the data of the tables justifies the statement that the +third problem was both easier and more nearly adequately solved than the +second. This is not surprising when the nature of the two problems is +considered, for whereas problem 2 requires choice by perception of the +relationship of secondness from the right end of the group, problem 3 +requires, instead, the choice of the end member of the group each time, +with the additional variation of alternation of ends. Now as it happens, +the end member is easily selected by the monkey, and it appears further +that alternation was relatively easy for Sobke to acquire. Consequently, +the combination of end and alternation proved easier than the choice of +the second from the right end of the group. + +The above statements are supported by comparison of the curves of +learning. The curve for problem 2, figure 19, is extremely irregular; +that for problem 3, figure 20, much more regular. Similarly, the daily +ratios of right to wrong choices as exhibited in tables 5 and 6 indicate +smaller variations for the third problem than for the second. + +Sobke made ten correct first choices in the third series for July 17, +but he was working very uncertainly and it seemed rather a matter of +good luck than good management that he succeeded in presenting this +perfect series: For this reason and also because it did not seem +feasible to have Sunday intervene between the final and perfect regular +series and the control series, an additional regular series was given on +July 19, in which, as the table indicates, a single mistake occurred, in +trial 5. The monkey was working perfectly. The series of trials required +only ten minutes, and it was evident that carelessness and eagerness to +obtain food were chiefly responsible for the mistake. + +The control series given on July 19 immediately after the series just +described resulted similarly in one failure and nine successes. The +choices were made easily and with certainty, and the only mistake, that +of setting 7, was apparently due to carelessness. + +This excellent showing for the control series wholly justifies the +comparison of problems 2 and 3 as to difficultness, made above. Whereas +in both problems 1 and 2 the control trials caused confusion, in the +case of problem 3, they did not essentially alter the behavior of the +animal. The fact seems to be that for this problem the particular +setting is of relatively little importance; while turning alternately to +the extreme left and the extreme right is of prime importance. That +Sobke had the idea of alternation or of the end box, there seems no more +reason for insisting than that he had the idea of secondness from the +right end in problem 2. It is possible, even probable, that these ideas +existed rather vaguely in his consciousness, but there is obviously no +necessity for insisting that the solution of the problems depended upon +them. + + +_Problem 4. Middle_ + +As the available time for the continuation of the experiment was +limited, it was decided to proceed with work on problem 4 immediately +upon the completion of problem 3, and on July 20, the problem of the +middle door was presented to Sobke. Since it was anticipated that this +sudden change would confuse and discourage him greatly, the only form of +punishment administered was the momentary lowering of the entrance door +of the wrong box. As in the previous problem, he was aided after ten +successive wrong choices. As might have been anticipated, he +persistently entered the end boxes of the groups, and this in some +instances probably would have been kept up for many minutes had not the +experimenter lured him into the right box by slightly raising the exit +door. In the first series, he had to be aided in five of the ten trials. +The total time for the series was forty-five minutes, the total number +of choices, eighty-eight. In the second series, he was aided in four of +the trials. The total time required was seventy-two minutes, and the +total number of choices was seventy-six. + +Throughout the first series, Sobke worked hard, but with evidently +increasing dissatisfaction. He clung persistently to his acquired +tendency to choose the end boxes, and after each trial he returned less +willingly to the starting point. Up to this time his attitude toward the +experimenter had been perfectly friendly, if not wholly trustful. But +when on July 21 he was brought into the apparatus for the second series, +he exhibited a wholly new form of behavior, for instead of attending +diligently to the open doors and devoting his energies to trying to find +the right box, he instead, after gazing at them for a few seconds, +turned toward the experimenter and jumped for him savagely, throwing +himself against the wire netting with great force. This was repeated a +number of times during the first two or three trials, and it occurred +less frequently later in the series. Since nothing unusual had happened +outside of the experiment room, the suggested explanation of this sudden +change in attitude and behavior is that the monkey resented and blamed +on the experimenter the difficulty which he was having in obtaining +food. + +From this time on until the end of my work, Sobke was always savage and +both in and out of the apparatus he was constantly on the watch for an +opportunity to spring upon me. Previously, it had been possible for me +to coax him into the apparatus by offering him food and to return him to +his cage by walking after him. But on and after the twenty-first of +July, it was impossible for me to approach him without extreme risk of +being bitten. + +Doctor Hamilton when told of this behavior, reported that several times +monkeys have shown resentment toward him when they were having trouble +in the experiment. I therefore feel fairly confident that I have not +misinterpreted Sobke's behavior. When on July 22 I gave Sobke an +opportunity to enter the apparatus, he refused, and it was impossible to +lure him in with food. Two hours later, having waited meantime for his +breakfast, he entered readily and worked steadily and persistently +through his third series of trials, but in no one of these trials did he +choose correctly. Neither on this day nor the following did he exhibit +resentment while at work. He apparently had regained his affective poise +and was able to attend as formerly to the task of locating his rewards. + +During these first three series, although the ratio of right to wrong +choices stood 0 to 10, there occurred a marked reduction in the number +of trials in which aid was necessary as well as in the total number of +choices, and on July 23 correct reactions began to appear. Improvement +during the next hundred trials was steady and fairly rapid, and on July +31, a record of seven right to three wrong trials was obtained. This was +surprising to the experimenter, as well as gratifying, since he was +eager to have the animal complete this problem before work should have +to be discontinued. + +Everything went smoothly until August 2, when my assistant, who had been +left in charge of the experimental work for a week, attempted to +increase the number of trials per day to two series. Sobke apparently +was not quite ready for this increase in the amount of his day's labor +and refused to work at the end of the first series. In this series he +did less well than on the previous day. The following day, August 3, +unfortunately and contrary to the wishes of the experimenter, the +laboratory was painted and there was necessarily considerable +disturbance because of the presence of the workmen, and in addition, the +pervasive odor of fresh paint. Sobke chose still less successfully on +this date, and on August 4, he refused to work after the eighth trial. +It is true that during these bad days the total number of choices +steadily diminished while the successes, also, diminished, or at best, +failed to increase. When on August 9, I returned to the laboratory to +take charge, I found that Sobke was no longer trying to solve the +problem as when I had gone away. His attitude had changed in that he had +become indifferent, careless, and obviously discouraged with his task. + + + +TABLE 7 + +Results for Sobke, _P. rhesus_, in Problem 4 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | 1.2.3.4 | | | 1.2.3.4.5 | | | 3.4.5.6 | | R | W | R | W | of + | trials | 2.3.4 | 5.6.7.8.9 | 5.6.7 | 7.8.9 | 4.5.6.7.8 | 6.7.8.9 | 1.2.3 | 2.3.4.5.6 | 7.8.9 | 6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + July | | | {5.9.5.5 | {1.7.1.3 | {9.7.9.7 | | {1.9.3.1 | | {6.3.2.6 | | | | | | | + 20 | 1- 10 | 2.4.2.4.3 | {5.9.5.6 | {1.7.1.7 | {7.9.7.9 | {8.4.8.4 | {9.2.9.3 | 3.1.3.2 | {3.6.3.2 | {9.3.4.3 | {8.6.6.8.6 | 0 |10 | 0 |10 | 0:10.00 + | | | {5.8.7* | {1.7.4* | {7.7.8 | {4.6 | {9.1.5* | | {6.3.4* | {3.9.3.6 | {8.6.8.6.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | {7.9.7.7 | {4.8.5.5 | {1.4.3.2 | | | {3.9.3.8 | | | | | | + 21 | 11- 20 | 2.3 | {5.6.5.5 | {1.2.7.1 | {7.9.7.7 | {8.4.8.4 | {8.9.1.9 | 3.1.2 | {6.2.3.2.6 | {4.3.3.5 | 6.7 | 0 |10 | 0 |10 | 0:10.00 + | | | {9.5.5.7 | {7.3.7.4 | {9.7.8* | {5.4.6* | {1.9.5* | | {3.5.2.4 | {3.4.6* | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | {3.7.4.8 | | | | | | + 22 | 21- 30 | 2.3 | 5.6.5.6.7 | 1.7.4 | {7.9.7 | 4.7.4.6 | {1.4.6.3 | 3.1.2 | 5.2.6.4 | {4.3.5.8 | 6.6.7 | 0 |10 | 0 |10 | 0:10.00 + | | | | | {7.7.8 | | {2.7.5 | | | {3.7.6* | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | {5.4.7.4 | | | | | | + 23 | 31- 40 | 2.4.3 | 5.6.8.7 | 1.7.4 | {7.7.7.7 | 4.7.6 | 2.7.5 | 3.1.2 | 6.4 | {7.5.4.3 | 7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | {7.7.8 | | | | | {7.3.6 | | | | | | + | | | | | | | | | | | | | | | | + 24 | 41- 50 | 3 | 5.6.7 | 1.6.4 | 7.7.7.8 | 4.7.6 | {2.7.6.4 | 3.2 | 6.5.4 | 5.3.8.6.6 | 7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | {2.7.3.8 | | | | | | | | | + | | | | | | | {9.6.5* | | | | | | | | | + | | | | | | | | | | | | | | | | + 26 | 51- 60 | 4.3 | 6.5.7 | 2.7.4 | 7.8 | 6 | {6.4.2.7 | 3.2 | {6.5.3.5.2 | 7.6 | 7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | {4.8.6.5 | | {6.5.6.4 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | {4.7.3.7 | | | | | | | | | + 27 | 61- 70 | 3 | 6.5.7 | 2.5.4 | 7.7.8 | 5.7.6 | {4.6.1.4 | 2 | 6.5.4 | 5.7.6 | 6.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | {7.3.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 71- 80 | 3 | 7 | 6.5.4 | 7.8 | 5.4.7.6 | 2.7.6.5 | 2 | 5.5.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 29 | 81- 90 | 3 | 6.5.7 | 2.4 | 7.7.8 | 5.4.6 | {2.7.7.6 | 2 | 4 | 5.4.7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | {2.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 30 | 91-100 | 3 | 7 | 2.6.5.4 | 7.8 | 6 | 5 | 2 | 5.4 | 5.4.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 31 | 101-110 | 3 | 7 | 2.4 | 7.8 | 6 | 5 | 2 | 4 | 7.6 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + August | | | | | | | | | | | | | | | | + 2 | 111-120 | 3 | 7 | 6.5.7.6.4 | 7.8 | 6 | 4.2.7.6.5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 3 | 121-130 | 3 | 6.5.7 | 7.6.5.4 | 7.8 | 7.6 | 5 | 2 | 6.5.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 4 | 131-140 | 3 | 7 | 6.5.7.6.4 | 7.8 | 6 | {2.7.6.4 | 2 | 6.4 | 3.5.4.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + | | | | | | | {8.7.6.5 | | | | | | | | | + | | {2.4.4.4 | | | | | | | | | | | | | | + 5 | 141-150 | {2.4.4.2 | 6.5.7 | {2.7.6.7 | 8 | 7.6 | {2.8.7.6 | 3.2 | 6.4 | 7.6 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | {4.3* | | {5.4 | | | {8.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 6 | 151-160 | 2.4.4.3 | 7 | 2.6.5.4 | 7.8 | 7.6 | 7.6.5 | 2 | 6.4 | 6 | 7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + | | {4.4.2.4 | | | | | | | | | | | | | | + " | 161-170 | {4.2.4.2 | 7 | 6.5.4 | 7.8 | 7.6 | 7.6.5 | 3.2 | 5.4 | 7.6 | 7 | 2 | 8 | 6 |14 | 1: 2.33 + | | {4.4.3 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 7 | 171-180 | 4.3 | 7 | 6.5.4 | 8 | 7.6 | 5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | | | + | | | | | | | | | | | | | | | | + " | 181-190 | {4.2.4.4 | 7 | 7.6.5.4 | 7.8 | 6 | 6.5 | 2 | 6.5.4 | 7.6 | 7 | 4 | 6 | 9 |11 | 1: 1.22 + | | {2.4.3 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 9 | 191-200 | 3 | 7 | 5.4 | 8 | 8.7.6 | 6.5 | 2 | 6.5.4 | 7.6 | 8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 10 | 201-210 | 3 | 7 | 2.5.4 | 7.8 | 7.6 | {2.8.7.6 | 2 | 6.5.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | {8.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 11 | 211-220 | 3 | 7 | 6.5.4 | 7.8 | 6 | {7.6.4.3 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + | | | | | | | {2.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 12 | 221-230 | 3 | 7 | 2.4 | 7.8 | 6 | 7.6.5 | 2 | 6.5.4 | 8.7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 19 | 231-240 | 3 | 7 | 2.4 | 7.8 | 6 | 5 | 2 | 6.4 | 8.7.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | | | | | | + 20 | 241-250 | 3 | 7 | 5.4 | 8 | 7.6 | {2.4.1.2.7 | 3.2 | 6.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | {8.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 21 | 251-260 | 3 | 7 | 6.5.4 | 7.8 | {7.4.5.4 | {6.4.3.2 | 2 | 6.5.4 | 8.7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | {8.7.6 | {7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 23 | 261-270 | 3 | 7 | 6.5.4 | 7.8 | 6 | 6.5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 24 | 271-280 | 3 | 7 | 6.4 | 7.8 | 7.6 | 2.5 | 2 | 4 | 7.4.3.8.7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 25 | 281-290 | 3 | 7 | 2.5.4 | 8 | 7.6 | 5 | 2 | 6.4 | 7.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 26 | 291-300 | 3 | 7 | 6.5.4 | 8 | 7.6 | 7.6.5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 27 | 301-310 | 3 | 7 | 2.6.5.4 | 8 | 7.6 | 5 | 2 | 6.5.4 | 7.5.4.9.8.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 28 | 311-320 | 3 | 7 | 2.5.4 | 8 | 6 | 9.8.7.5 | 2 | 3.4 | 8.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +I immediately set about reinstating the former attitude by lessening the +number of trials and the punishment, and by increasing the value of the +reward, but my best efforts, continuing up to August 28, failed markedly +to improve the condition. The number of correct choices did somewhat +increase, but at no time did the animal attain the degree of success +which he had achieved as early as July 31 in the eleventh series of +trials. + +During the last two weeks of experimentation, all possible efforts were +put forth to discover the best combination of rewards and punishments. +Punishment was varied from 0 to confinement of sixty seconds, and many +kinds of food in different amounts were tried as rewards, but in spite +of everything Sobke failed to improve markedly. From time to time, +notably on August 12 and 21, he exhibited peculiarly strong resentment +toward me and repeatedly attempted to attack me. + +The outcome of my experiments with problem 4 is peculiarly interesting +in that it indicates the importance of a favorable attitude toward the +work and the extreme risk from disturbing or discouraging conditions. It +seems not improbable that had the work progressed without change in +experimenter, or method of procedure, and above all without the +disturbance of the painting, Sobke might have solved problem 4 within a +few days. This is by no means certain, however, for in problems 2 and 3 +the ratio of right to wrong choices instead of increasing steadily +increased very irregularly. + +The detailed results for this problem are given in table 7. Reactive +tendencies which appear are: (a) persistent choice of the end boxes +followed, subsequently, by (b) the tendency to locate the middle box +directly. This proved fairly easy when the number of boxes involved was +only three as in settings 1, 4, 7, and 10. Setting 4 was most difficult +of all, because box 9 was avoided or ignored. When the number of open +boxes was as great as five, as in settings 2 and 8, the task was +obviously more difficult, but whereas success in setting 2 appeared +early, in setting 8 it failed to appear during the course of +experimentation. For the settings 3, 6, and 9, involving either seven or +nine open boxes, the direct choice of the middle box was next to +impossible, and Sobke tended to choose, first of all, a particular box +toward one end of the series, for example, box 2, in setting 3, and box +7 in setting 9. To the experimenter, as he watched the animal's +behavior, it looked as though effort each time were being made to locate +the middle member of the group. This appeared relatively easy for groups +of three boxes, extremely difficult for as many as five boxes, and +almost impossible for seven or nine. + + +3. Julius, _Pongo pygmaeus_ + +_Problem 1. First at the Left End_ + +The orang utan, Julius, was gentle, docile, and friendly with the +experimenter throughout the period of investigation. He at no time +showed inclination to bite and could be handled safely. As contrasted +with Skirrl and even with Sobke, he adapted himself to the +multiple-choice apparatus very promptly, and only slight effort on the +part of the observer was necessary to prepare him, by preliminary +trials, for the regular experiments. But in order to facilitate work, he +was familiarized with the apparatus by means of regular route training +and feeding in the several boxes from April 5 to April 9. + +On April 10 the apparatus was painted white as has been stated +previously, and on the following Monday, April 12, Julius when again +introduced to it gave no indications of fear, uneasiness, or dislike, +but worked as formerly, making his round trips quickly and eagerly +entering any box which happened to be open, in order to obtain the +reward of food. + +The regular experimentation was undertaken on April 13, and the results +of the first series of trials with Julius are sharply contrasted with +those obtained with the monkeys in that fewer choices were necessary. +Instead of the expected ratio of right to wrong first choices, 1 to 2.5, +the orang utan gave a ratio of 1 to 1. An additional markedly different +result from that obtained with the monkeys is indicated below in the +total time required for a series of trials. As examples, the data for +the first, second, fifth, and tenth series are presented. + + + +TIME FOR SERIES OF TRIALS + + 1st series 2nd series 5th series 10th series +Skirrl 35 min. 20 min. 14 min. 10 min. +Sobke 14 " 17 " 10 " 9 " (8th series) +Julius 12 " 11 " 14 " 9 " + + + +It is also noteworthy that Julius in the presence of visitors or under +other unusual conditions worked steadily and well, whereas the monkeys, +and especially Sobke, tended to be distracted and often refused to work +at all. + +Almost from the beginning of his work on problem l, Julius began to +develop the tendency to enter immediately the open door nearest the +starting point. In case the group of open doors lay to the right of the +middle of the apparatus, this method naturally yielded success; whereas +if the group included doors to the left of the middle, it resulted in +failure. Obviously it was a most unsatisfactory method, and although it +enabled him to make more right than wrong first choices, it prevented +him from increasing the number of right choices, and as table 1 +indicates, it maintained the ratio of 1 right to .67 wrong first choices +for eight successive days. + +On April 23 a break occurred in which the number of correct choices was +reduced from six to five. Julius worked very rapidly and with almost no +hesitation in choosing. My notes record "he seems to miss the point +wholly. It is doubtful whether the punishment is sufficiently severe." +At this time he was being punished by thirty seconds confinement in each +wrong box, the interval having been held fairly steadily from the first +series of experiments. On April 26 it was increased to sixty seconds, in +an effort to break him of the habit of choosing the "nearest" door. But +he became extremely restless under the longer confinement and tried his +best to raise the entrance and exit doors. Since there was at this time +no mechanism for locking them when closed, it was difficult for the +experimenter to prevent him from escaping by way of the entrance door or +from raising the exit door sufficiently to obtain the food. Indeed, the +longer confinement worked so unsatisfactorily that on the following day +I substituted for it the punishment of forcing him to raise the entrance +door of the wrong box in order to escape for a new choice. He was +rewarded with food in the alleyway H, beside door 15 (figure 17), only +when he chose correctly on first attempt. + +This method discouraged him extremely and proved wasteful of time. +Consequently, in a second series on the same date return was made to the +former method, and he was rewarded with food whenever he found the right +box. But on April 28, the two methods were again employed, the first in +the initial series and the second in a final series of trials. The +animal's persistent attempts to raise the doors gave the experimenter so +much trouble that on April 29 barbed wire was nailed over the windows of +the entrance doors with the hope that it might prevent him from working +at them. But he quickly learned to place his fingers between the barbs +and raise the doors as effectively as ever. + +On April 30 the reward of food was given only when the first choice was +that of the right box and in that event it was placed in the alleyway H +as stated above. + +As it seemed absolutely essential to break the unprofitable habit of +choosing the nearest door, on May 3 a new series of settings was +presented, in which only the doors to the left of the middle of the row +of nine boxes were used as right doors. That is, in this new series, +doors 1 to 4 occur as right doors; 5 to 9 do not. As punishment for +wrong choices on this date, Julius was confined in the wrong box from +one to five minutes. It was difficult to keep him in, but by means of +cords which had been attached to the doors, this was successfully +accomplished. Yet another and slightly different series of settings was +employed on May 4, and this, proving satisfactory, was continued in use +until the end of the experiment, with punishment ranging from sixty to +one hundred and twenty seconds for each mistake. + +Naturally the modification of settings introduced May 3 greatly +increased the proportion of wrong first choices. Indeed, as appears in +table 8, the ratio of right to wrong immediately changed from 1:0.67 to +1:4.00. Between May 3 and May 10, no steady and consistent improvement +in method or in the number of correct first choices occurred, and on the +last named date, Julius chose correctly only three times in his ten +trials. At this time there was, as my notes record, no satisfactory +indication of progress, and the status of the experiment seemed +extremely unsatisfactory in as much as in spite of the experimenter's +best efforts to break up the habit of choosing the nearest door, the +orang utan still persisted, to a considerable extent, in the use of this +method. The only encouraging feature of the results was an evident +tendency to choose somewhat nearer the left end of a group than +previously. + + + + +TABLE 8 + +Results for Orang utan in Problem 1 + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | | | R | W | R | W | of + | trials | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + April | | | | | | | | | | | | | | | | + 13 | 1- 10 | 3.1 | 8 | 4.3 | 7 | 4.2 | 7.6 | 5 | 4 | 7 | 3.1 | 5 | 5 | 5 | 5 | 1:1.00 + 14 | 11- 20 | 3.2.1 | 8 | 4.3 | 7 | 4.4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 15 | 21- 30 | 3.2.1 | 8 | 4.3 | 7 | 4.5.5.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 16 | 31- 40 | 3.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | 6 | 4 | 1:0.67 + 17 | 41- 50 | 3.2.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 19 | 51- 60 | 3.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 20 | 61- 70 | 2.1 | 8 | 4.3 | 7 | 5.3.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 21 | 71- 80 | 3.1 | 8 | 4.3 | 7 | 5.4.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | 6 | 4 | 1:0.67 + 22 | 81- 90 | 3.1 | 8 | 5.3 | 7 | 6.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | 6 | 4 | 1:0.67 + 23 | 91-100 | 3.2.1 | 8 | 5.3 | 7 | 4.3.2 | 6 | 5 | 5.4 | 7 | 3.2.1 | 5 | 5 | 5 | 5 | 1:1.00 + 24 | 101-110 | 3.2.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 26 | 111-120 | 3.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 5.4 | 7 | 3.1 | 5 | 5 | 5 | 5 | 1:1.00 + 27 | 121-130 | 3.2.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 6.5 | 5.8.6.4 | 7 | 3.3.3.1 | 4 | 6 | | | + " | 131-140 | 3.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 |10 |10 | 1:1.00 + 28 | 141-150 | 3.2.1 | 8 | 3 | 7 | 5.4.2 | 6 | 5 | 4 | 7 | 3.1 | 7 | 3 | | | + " | 151-160 | 3.1 | 8 | 3 | 7 | 3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 7 | 3 |14 | 6 | 1:0.43 + 29 | 161-170 | 3.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | | | + " | 171-180 | 3.2.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 |12 | 8 | 1:0.67 + | | | | | | | | | | | | | | | | + 30 | 181-190 | 3.1 | 8 | 4.3 | 7 | {4.5.6.4 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | | | + | | | | | | {5.6.4.2 | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 191-200 | 3.1 | 8 | 4.5.6.7.3 | 7 | 4.5.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 |12 | 8 | 1:0.67 + May | | | | | | | | | | | | | | | | + 1 | 201-210 | 3.1 | 8 | 4.3 | 7 | 3.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | | | + " | 211-220 | 3.2.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 |12 | 8 | 1:0.67 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 2.3.4.5 | | | | | | | 2.3.4.5 | | | | | + | | 1.2.3 | 3.4.5.6.7 | 6.7.8 | 1.2.3 | 3.4.5.6.7 | 4.5.6.7.8.9 | 2.3.4.5 | 1.2.3 | 4.5.6.7.8.9 | 6.7.8.9 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 3 | 221-230 | 3.1 | 4.3 | 4.2 | 3.1 | 4.3 | 4 | 4.3.2 | 3.1 | 4 | 4.3.2 | 2 | 8 | 2 | 8 | 1:4.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 2.3.4.5 | 4.5.6.7 | | | | | 2.3.4.5 | | | | | | + | | 1.2.3 | 3.4.5.6.7 | 6.7.8 | 8.9 | 2.3.4.5 | 3.4.5.6 | 1.2.3 | 4.5.6.7.8 | 6.7.8.9 | 1.2.3 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 4 | 231-240 | 3.2.1 | 4.3 | 4.2 | 4 | 4.3.2 | 4.3 | 3.2.1 | 4 | 3.2 | 3.2.1 | 2 | 8 | 2 | 8 | 1:4.00 + 5 | 241-250 | 2.1 | 3 | 3.2 | 4 | 3.2 | 4.3 | 3.2.1 | 4 | 3.2 | 3.2.1 | 3 | 7 | 3 | 7 | 1:2.33 + 6 | 251-260 | 2.1 | 3 | 2 | 4 | 3.2 | 3 | 2.1 | 4 | 3.2 | 2.1 | 5 | 5 | 5 | 5 | 1:1.00 + 7 | 261-270 | 2.1 | 3 | 3.2 | 4 | 3.2 | 3 | 2.1 | 4 | 4.2 | 2.1 | 4 | 6 | 4 | 6 | 1:1.50 + 8 | 271-280 | 2.1 | 4.3 | 4.3.2 | 4 | 3.2 | 4.3 | 3.1 | 4 | 3.2 | 2.1 | 2 | 8 | 2 | 8 | 1:4.00 + 10 | 281-290 | 1 | 4.3 | 4.2 | 4 | 3.2 | 4.3 | 2.1 | 4 | 3.2 | 2.1 | 3 | 7 | 3 | 7 | 1:2.33 + 11 | 291-300 | 1 | 3 | 2 | 4 | 2 | 3 | 1 | 4 | 2 | 1 |10 | 0 |10 | 0 | 1:0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + | | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 12 | 301-310 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 |10 | 0 |10 | 0 | 1:0.00 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + + + +A series of correct first choices was obtained on May 11, greatly to the +surprise of the experimenter, for no indication had previously appeared +of this approaching solution of the problem. It seemed possible, +however, that the successes were accidental, and it was anticipated that +in a control series Julius would again make mistakes. But on the +following day, May 12, the presentation of the original series of ten +settings, which, of course, differed radically from the settings used +from May 4 to May 11 was responded to promptly, readily, and without a +single mistake. Julius had solved his problem suddenly and, in all +probability, ideationally. + +Only three reactive tendencies or methods appeared during Julius's work +on this problem: (a) choice of the open door nearest to the starting +point (sometimes the adjacent boxes were entered); (b) a tendency to +avoid the "nearest" door and select instead one further toward the left +end of the group; (c) direct choice of the first door on the left. + +The curve of learning plotted from the daily wrong choices and presented +in figure 18, had it been obtained with a human subject, would +undoubtedly be described as an ideational, and possibly even as a +rational curve; for its sudden drop from near the maximum to the base +line strongly suggests, if it does not actually prove, insight. + +Never before has a curve of learning like this been obtained from an +infrahuman animal. I feel wholly justified in concluding from the +evidences at hand, which have been presented as adequately as is +possible without going into minutely detailed description, that the +orang utan solved this simple problem ideationally. As a matter of fact, +for the solution he required about four times the number of trials which +Sobke required and twice as many as were necessary for Skirrl. Were we +to measure the intelligence of these three animals by the number of +trials needed in problem 1, Sobke clearly would rank first, Skirrl +second, and Julius last of all. But other facts clearly indicate that +Julius is far superior to the monkeys in intelligence. We therefore must +conclude that _where very different methods of learning appear, the +number of trials is not a safe criterion of intelligence._ The +importance of this conclusion for comparative and genetic psychology +needs no emphasis. + + +_Problem 2. Second from the Right End_ + +Julius was given four days' rest before being presented with problem 2. +He was occasionally fed in the apparatus, but regular continuation of +training was not necessary to keep him in good form. During this rest +interval, locks were attached to the doors of the apparatus so that the +experimenter by moving a lever directly in front of him could fasten +either one or both of the doors of a given box by a single movement. On +May 13 Julius was given opportunity to obtain food from each of the +boxes in turn, and trial of the locks was made in order to familiarize +him with the new situation. He very quickly discovered that the doors +could not be raised when closed, and after two days of preliminary work, +he practically abandoned his formerly persistent efforts to open them. +The locks worked satisfactorily from a mechanical point of view as well +as from that of the adaptation of the animal to the modified situation. + +Problem 2 was regularly presented for the first time on May 17, on which +day a single series was given. The period of punishment adopted was +twenty seconds, and for each successful choice a small piece of banana +was given as a reward. After the first trial in this series, in which +Julius repeatedly entered the first box at the left, that is box 7, +there was but slight tendency to reënter the first box at the left of +the group. Instead, Julius developed the method of moving box by box +toward the right end of the group. The choices were made promptly, and +their systematic character enabled the animal to obtain his reward +fairly quickly, in spite of the large number of mistakes. + +In the second series, the orang utan developed the interesting trick of +quickly dodging out of the wrong box before the experimenter could lower +the door behind him. This he did only after having been punished for +many wrong choices to the point of discouragement. The trick was easily +broken up by the sudden lowering of the entrance door as soon as he had +passed under it. + +There appeared on May 21 an unfavorable physical condition which +manifested itself, first of all through the eyes which appeared dull and +bloodshot. On the following day they were inflamed and the lids nearly +closed. Julius refused to eat, and experimentation was impossible. Until +June 2 careful treatment and regulation of diet was necessary. He passed +through what at the time seemed a rather startling condition, but +rapidly regained his usual good health, and on June 3, although somewhat +weak and listless, he again worked fairly steadily. + +Since it was now possible to lock the doors and confine the animal for +any desired period, on June 5 the interval of punishment was made sixty +seconds, and a liberal quantity of banana, beet, or carrot was offered +as reward. No increase in the number of successful choices appeared, and +Julius showed discouragement. Sawdust had been strewn on the floor, and +in the intervals between trials as well as during confinement in wrong +boxes, he took to playing with the sawdust. He would take it up in one +hand and pour it from hand to hand until all had slipped through his +fingers, then he would scrape together another handful and go through +the same process. Often he became so intent on this form of amusement +that even when the exit door was raised, he would not immediately go to +get the food. + +The reactive tendencies which appeared in the work on problem 2 will now +be presented in order, since I shall have to refer to them repeatedly, +and the list will be more useful to the reader at this point than at the +conclusion of the presentation of daily results. The following is not an +exhaustive list but includes only the most important and conspicuous +tendencies or methods together with the dates on which they were most +apparent. + +(a) May 17, choice of first box at left of group or near it, then the +next in order, and so on, until the second from the right was reached. +This method with irregularities and certain definite skipping was used +at various times, sometimes over periods of several days, during the +course of the work. + +(b) June 3, preference for number 3 and number 4 developed immediately +after the orang utan's illness and when he was working rather +listlessly. + +On June 9 and 10, the original tendency (a) reappeared and persisted for +a number of series. + +(c) June 14, a tendency to choose the box at or near the right end of a +group, and then the one next to it. In connection with this tendency, +which of course required only two choices in any given trial, interest +in playing with the sawdust on the floor developed. + +Again on June 21, the animal returned to the use of tendency (a). + +(d) June 29, movement to box at right end of group, hesitation before +it, and turning through a complete circle so that the second box from +the right was faced. This, the correct box, was often promptly entered. +This method, if persisted in, would obviously have yielded solution of +the problem. + +(e) July 5, approach to and pretense to enter the box next to the right +end (right one), and then choice of some other box. This _feint_ is +peculiarly interesting, and its origin and persistence are difficult to +account for. + +(f) In connection with the tendency to pretend that he was going to +enter the second box from the right end, Julius developed also the +tendency to turn around in front of the box at the right end, starting +sometimes to back into it, and then to enter, instead, the box second +from the end. + +(g) July, 6 and 7, a fairly definite tendency to take the one next in +order or, instead, to go directly to the right box. + +(h) July 10, direct first choices without approach to other boxes +appeared for the first time on this date. + +For this problem, it proved impossible to establish and maintain uniform +conditions of experimentation. Instead, because of the failure of the +animal to improve and the tendency to discouragement, both punishment +and reward had to be altered from time to time, and other and more +radical changes were occasionally made in the experimental procedure. +Below for the sake of condensed and consecutive presentation, the most +important conditions from day to day are arranged in tabular form: + + + +CONDITIONS OF EXPERIMENT FROM DAY To DAY FOR PROBLEM 2 + +Date Punishment Reward + +May 17 ............. 20 sec. confinement ........ Food in right box for each + (Aid after 10 trials) trial + + " 18 to 21 ........ 30 sec. confinement ........ Food (banana) in right box + for each trial + + " 22 to June 2 .... Illness, no experiments + +June 3 ............... 15 sec. confinement ........ Food (banana) in right box + for each trial + + " 4 ............... 30 " " ............. Food (banana) in right box + for each trial + + " 5-10 ............ 60 " " ............. Beet, carrot and loquat, in + addition to banana + + " 11 .............. 10 to 30 sec. confinement .. Beet, carrot and loquat, in + addition to banana + + " 12 to 15 ........ 60 sec. confinement ........ Beet, carrot and loquat, in + addition to banana + + " 16 .............. 60 " " ............. Banana and sweet corn--former + preferred + + " 17 (1st series). 60 sec. confinement ........ Food (banana, as in early + series) + + " 17 (2nd series). No confinement in wrong box; Food only for correct first + but instead, return to choices + starting point by way of + alleys + + " 18 to 22 ........ No confinement in wrong box; Food only for correct first + but instead, return to choices + starting point by way of + alleys + + " 22 (2nd series). No punishment; allowed to Food for each trial + enter boxes until right + one was found + " 23 .............. Return to starting point. + After five wrong choices + of a given box the animal + was held for 60 secs. in + one of the boxes and was + then released by way of + the exit door and rewarded + when the right one was + chosen + + " 23 (2nd series). No punishment .............. Reward for each trial + + " 24 (1st series). Return to starting point. .. Food only for correct first + choices + + " 24 (2nd series). No punishment .............. Reward for each trial + + " 25-30 ........... Same as on 24th ............ + +July 1 (1st series). No punishment .............. " " " " + + " 1 (2nd series). Return to starting point ... Reward only for correct first + choices + " 2-8 ............. Same as on July 1 .......... + + " 8 (2nd series). No punishment .............. Reward for each trial + + " 8 (3rd series). Return to starting point ... Reward only for correct first + choices + + " 9-10 ............ Same as for July 8 (3rd series) + + " 10 (2nd series). Momentary confinement in ..... Reward for each correct choice + wrong boxes + + " 12 .............. Return to starting point ..... Reward for correct first choice + + " 12 (2nd series). 30 sec. confinement .......... Reward for each correct choice + + " 12 (3rd series). 5 " " ............... " " " " " + + " 13 .............. 30 " " ............... " " " " " + + " 14-17 ........... Return to starting point ..... Reward for correct first choices + + " 17 (2nd series). 60 sec. confinement .......... Reward for each correct choice + + " 19 .............. 30 " " ............... " " " " " + + " 20-26 ........... 10 " " ............... " " " " " + + " 27-30 ........... Right box indicated by slight Reward in each right box + raising of exit door + momentarily. + No punishment + + " 30 (2nd series). Return to starting point ..... Reward for correct first choices + + " 31 .............. " " " " ..... " " " " " + + " 31 (2nd series) + to Aug. 10 .... 10 to 60 sec. confinement .... Reward for each correct choice + +Aug. 10 (2nd series). Threatened with whip ......... " " " " " + + " 11 (1st series). " " " ........... " " " " " + + " 11 (2nd series). 10 sec. confinement .......... " " " " " + + " 12 .............. Threatened with whip ......... " " " " " + + " 12 (2nd series). 10 sec. confinement .......... " " " " " + + " 19 .............. 10 " " ............... " " " " " + + " 19 (2nd series). Threatened with whip ......... " " " " " + + + + +With the above reactive tendencies and modifications of method in mind +we may continue our description of results. On June 9 there developed a +tendency to increase the magnitude of the original error by choosing +nearer the left end of the groups. This is odd, since one would +naturally suppose that an animal as intelligent as the orang utan would +tend to avoid the general region in which success was never obtained and +to focus attention on the right, as contrasted with the wrong end of +each group. _It obviously contradicts the law of the gradual elimination +of use less activities._ In other words, it is wholly at variance with +the principle of trial and error exhibited by many infrahuman organisms. +Julius, although making many mistakes, worked diligently and, for the +most part, fairly rapidly. The day's work proved most important because +of the change in method and also because of the appearance of +hesitation, the rejection of certain boxes, and the definite choice of +others. My notes record "this is a most important day for Julius in +problem 2;" but subsequent results do not clearly justify this prophecy. + +The method of choosing the first box at the left and then of moving down +the line until the right one was reached was so consistently followed +that during a number of days it was possible for me to predict almost +every choice. Indeed, to satisfy my curiosity in this matter during a +number of series I guessed in advance the box which would be chosen. The +percentages of correct guesses ranged from ninety to one hundred. June +10, for example, yielded two series for which the ratio of right to +wrong first choices was 0 to 10, and in which the method described above +was used consistently throughout. + +It was inevitable that punishment by confinement and the discouragement +resulting therefrom should interfere with the regularity of work and +make it extremely difficult to obtain strictly comparable results from +series to series and from day to day. The data for this problem, as +presented in table 9, have values quite different from those for the +monkeys, chiefly because of the more variable conditions of observation. + +It was occasionally noted that the disintegration of a definite method +and the disappearance of the tendency on which it depended occurred +rather suddenly. Frequently it happened that having used an inadequate +method fairly persistently on a given day, the animal would on the +following day exhibit a wholly different method. Even over night a new +method might develop. In the monkeys, although there was occasionally +something comparable with this, it was by no means so evident. + + + +TABLE 9 + +Results for Orang utan in Problem 2 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | 1.2.3.4.5 | | | R | W | R | W | of + | trials | 7.8.9 | 1.2.3.4 | 2.3.4.5.6.7 | 1.2.3.4.5.6 | 4.5.6.7.8 | 1.2.3 | 2.3.4.5 | 6.7.8.9 | 1.2.3.4 | 3.4.5.6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + May | | {7.7.7.7 | | | | | | | | | | | | | | + 17 | 1- 10 | {7.7.7.7 | 1.1.3 | 2.4.6 | 2.3.4.5 | 4.5.7 | 3.2 | 2.3.4 | {2.3.4.5 | 1.2.3 | 3.4.5.6.7 | 0 |10 | 0 |10 | 0:10.00 + | | {7.7.8 | | | | | | | {6.7.8 | | | | | | | + | | | | | | | | | | | {4.5.6.8 | | | | | + 18 | 11- 20 | 7.8 | 1.3 | 3.4.5.6 | 2.4.5 | 4.5.6.7 | 2 | 2.3.4 | {2.3.4.5 | 1.2.3 | {8.8.8.3 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | | {6.7.8 | | {4.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | {2.4.7.7.2 | | | | | | | {5.3.4.5 | | | | | + 19 | 21- 30 | 7.8 | 1.3 | {5.7.7.2 | 5 | 4.6.8.4.7 | 1.2 | 2.3.4 | 5.8 | 3 | {6.8.4.5 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | {3.2.4.6 | | | | | | | {3.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + 20 | 31- 40 | {7.9.7.7 | 3 | 4.5.6 | 4.5 | 5.6.7 | 2 | 4 | 5.6.7.8 | 3 | 5.6.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | {9.7.8 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 21 | 41- 50 | 7.8 | 3 | 3.4.5.6 | 4.5 | 4.5.6.7 | 2 | 3.4 | 4.5.6.8 | 3 | 4.5.6.7 | 3 | 7 | 3 | 7 | 1: 2.33 + June | | | | | | | | | | | | | | | | + 3 | 51- 60 | 7.8 | 3 | 4.5.6 | 3.4.5 | 4.5.6.7 | 3.1.2 | 3.4 | {3.7.9.7 | 3 | 4.5.6.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | {9.7.6.8 | | | | | | | + | | | | | | | | | | | | | | | | + 4 | 61- 70 | 7.8 | 3 | 4.5.6 | 4.5 | 4.5.6.7 | 3.3.1.2 | 4 | 4.5.6.7.8 | 3 | 4.5.6.7 | 3 | 7 | 3 | 7 | 1: 2.33 + 5 | 71- 80 | 7.9.7.8 | 3 | 3.4.5.6 | 3.6.3.4.5 | 4.7 | 3.1.2 | 4 | 3.4.5.6.7.8 | 3 | 4.5.6.7 | 3 | 7 | | | + " | 81- 90 | 7.8 | 3 | 3.4.5.6 | 3.4.5 | 4.5.6.7 | 2 | 3.4 | 3.4.5.6.7.8 | 2.3 | 4.5.6.7 | 2 | 8 | 5 |15 | 1: 3.00 + | | | | | | | | | | | | | | | | + 7 | 91- 100 | 7.8 | 3 | 4.5.6 | 4.5 | 4.5.6.7 | 1.2 | 3.4 | {3.4.5.6 | 2.3 | {3.4.5.6 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | | {7.8 | | {8.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + 8 | 101- 110 | 7.8 | 3 | 4.5.6 | 4.5 | 4.5.6.7 | 2 | 3.4 | 4.5.6.7.8 | 3 | 4.5.6.7 | 3 | 7 | | | + " | 111- 120 | 7.8 | 3 | 4.5.6 | 3.4.5 | 5.6.7 | 2 | 5.5.2.3.4 | 4.5.6.7.8 | 4.4.1.2.3 | 4.5.6.7 | 2 | 8 | 5 |15 | 1: 3.00 + | | | | | | | | | | | | | | | | + 9 | 121- 130 | 7.8 | 2.3 | 4.5.6 | 4.5 | 4.5.6.7 | 2 | 3.4 | {2.3.4.5 | 1.2.3 | 3.4.5.6.7 | 1 | 9 | | | + | | | | | | | | | {6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 131- 140 | 7.8 | 1.2.3 | 2.3.4.5.6 | 5 | 4.5.6.7 | 1.2 | 2.3.4 | 6.7.8 | 2.3 | 3.4.5.6.7 | 1 | 9 | 2 |18 | 1: 9.00 + | | | | | | | | | | | | | | | | + 10 | 141- 150 | 7.8 | 1.2.3 | 2.3.4.5.6 | 1.2.3.4.5 | 4.5.6.7 | 1.2 | 2.3.4 | {1.2.3.4 | 1.2.3 | 3.4.5.6.7 | 0 |10 | | | + | | | | | | | | | {5.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 151- 160 | 7.8 | 1.2.3 | 2.3.4.5.6 | 1.2.3.4.5 | 4.5.6.7 | 1.2 | 2.3.4 | {1.2.3.4 | 1.2.3 | 3.4.5.6.7 | 0 |10 | 0 |10 | 0:10.00 + | | | | | | | | | {5.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + 11 | 161- 170 | 8 | {4.1.2.4.1 | 2.3.4.5.6 | 5 | 6.7 | {3.1.3.1 | 5.2.3.4 | 2.6.7.8 | 4.1.2.3 | 8.5.6.7 | 2 | 8 | | | + | | | {4.1.4.1.3 | | | | {3.1.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 171- 180 | 9.7.8 | 4.3 | 5.6 | 4.5 | 7 | 3.1.2 | 5.4 | 8 | 4.2.3 | 7 | 3 | 7 | 5 |15 | 1: 3.00 + 12 | 181- 190 | 7.9.7.9.8 | 1.2.3 | 3.4.5.6 | 6.4.5 | 5.6.7 | 2 | 5.3.4 | 7.8 | 4.1.2.3 | 4.5.6.7 | 1 | 9 | 1 | 9 | 1: 9.00 + 14 | 191- 200 | 9.8 | 3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 6.7.8 | 4.2.3 | 7 | 2 | 8 | | | + " | 201- 210 | 8 | 2.3 | 7.6 | 6.5 | 8.7 | 3.1.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | 5 |15 | 1: 3.00 + | | | | | | | | | | | | | | | | + 15 | 211- 220 | {7.9.7.9 | 4.2.3 | 6 | 5 | 8.7 | 3.2 | 5.4 | 9.8 | 4.3 | 7 | 3 | 7 | | | + | | {7.9.8 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 221- 230 | 9.8 | 4.3 | 7.6 | 6.5 | 5.6.7 | 1.2 | 2.3.4 | 3.4.5.6.7.8 | 4.3 | 7 | 1 | 9 | 4 |16 | 1: 4.00 + 16 | 231- 240 | 7.9.8 | 3 | 7.6 | 6.5 | 8.7 | 2 | 5.4 | 5.6.7.8 | 4.1.4.3 | 8.7 | 2 | 8 | | | + " | 241- 250 | 9.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 6.7.8 | 4.3 | 6.7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | | | | | | | | | | | + 17 | 251- 260 | 9.8 | 4.3 | 7.6 | 6.5 | {6.5.4.6 | 3.2 | 5.4 | 6.5.6.7.8 | 3 | 5.6.7 | 1 | 9 | | | + | | | | | | {5.4.5.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | {6.6.6.5.6 | | | | | | | | | | + | | | | | | {5.5.5.6.6 | | | | | | | | | | + " | 261- 270 | {9.7.7.7 | 4.4.4.4.3 | 6 | 5 | {6.6.6.6.6 | {3.3.3.3 | 4 | {4.5.4.5.4 | 3 | {5.5.5.5 | 4 | 6 | 5 |15 | 1: 3.00 + | | {7.7.7.8 | | | | {6.5.4.5 | {3.3.2 | | {5.6.7.8 | | {5.5.8.7 | | | | | + | | | | | | {6.5.5.4 | | | | | | | | | | + | | | | | | {4.5.6.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + 18 | 271- 280 | {7.7.7.7 | 4.4.4.4.3 | 5.5.5.5.6 | 5 | {5.5.5.6 | {3.3.3. | 4 | {4.6.5.6 | 4.4.3 | 5.6.4.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | {7.7.8 | | | | {5.5.6 | {3.3.2 | | {6.7.4.8 | | | | | | | + | | | | | | | | | | | | | | | | + | | {7.7.7.9 | | | | | | | | | | | | | | + 19 | 281- 290 | {9.9.9.7 | {4.4.4 | {5.7.7 | 5 | 5.7 | {3.3.3.3 | 4 | 5.8 | {4.4.4.4 | {6.5.6.5 | 2 | 8 | | | + | | {7.7.8 | {4.4.3 | {7.4.6 | | | {3.3.2 | | | {4.4.3 | {5.5.7 | | | | | + | | | | | | | | | | | | | | | | + " | 291- 300 | 7.7.7.7.8 | 4.4.4.4.3 | 5.5.6 | 5 | {5.6.6.5.6 | 3.3.2 | {5.5.5.5 | 5.6.8 | 4.4.3 | 6.6.6.7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | {6.6.6.7 | | {3.4 | | | | | | | | + | | | | | | | | | {5.6.6.6.7 | | | | | | | + 21 | 301- 310 | 7.7.8 | 4.4.3 | 5.6 | 5 | {6.6.6.5 | {3.3.3.3 | 5.5.5.2.4 | {3.4.3.5.5 | {4.2.2.4 | 5.3.7 | 1 | 9 | | | + | | | | | | {5.6.5.7 | {3.2 | | {1.1.2.4.7 | {4.3 | | | | | | + | | | | | | | | | {2.3.2.2.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 311- 320 | {7.7.7.7 | 1.1.1.2.3 | {5.5.4.2 | 1.1.6.5 | 4.6.7 | 1.3.2 | {2.2.2.2 | {1.1.2.3 | {2.2.2.4 | {6.3.3.8 | 0 |10 | 1 |19 | 1:19.00 + | | {7.7.8 | | {2.5.6 | | | | {2.2.3.4 | {6.6.6.8 | {2.3 | {4.8.7 | | | | | + | | | | | | | | | | | | | | | | + 22 | 321- 330 | 7.8 | {2.4.2.1.4 | 6 | 5 | 6.6.8.7 | 3.2 | 5.5.3.3.4 | 3.3.7.7.8 | 4.4.4.2.3 | 6.7 | 2 | 8 | | | + | | | {4.4.4.3 | | | | | | | | | | | | | + " | 331- 340 | 7.8 | 3 | 6 | 5 | 6.7 | 3.2 | 5.4 | 6.7.8 | 3 | 5.6.7 | 4 | 6 | 6 |14 | 1: 2.33 + | | | | | | | | | | | | | | | | + 23 | 341- 350 | 7.8 | 4.2.4.3 | 6 | 5 | 6.7 | {3.3.3.1 | 5.5.4 | {7.5.4.3 | 4.4.4.3 | {6.6.3.6 | 2 | 8 | | | + | | | | | | | {3.3.3.2 | | {6.7.7.8 | | {8.6.8.7 | | | | | + | | | | | | | | | | | | | | | | + " | 351- 360 | 7.8 | 4.4.3 | 6 | 6.5 | 6.7 | 3.3.2 | 5.4 | {6.7.6.5 | 4.3 | 5.6.7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | | | | {7.6.8 | | | | | | | + | | | | | | | | | | | | | | | | + 24 | 361- 370 | 7.8 | 4.4.2.3 | 7.7.6 | 6.6.4.5 | 7 | {3.3.3.3 | 5.4 | 8 | 4.4.3 | 5.6.7 | 2 | 8 | | | + | | | | | | | {3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 371- 380 | 8 | 4.3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 7.6.8 | 4.3 | 7 | 4 | 6 | 6 |14 | 1: 2.33 + | | | | | | | | | | | | | | | | + 25 | 381- 390 | 8 | 4.4.3 | 7.7.7.6 | {6.6.6.6 | 8.6.7 | 3.1.2 | 5.3.5.4 | 8 | 3 | 7 | 4 | 6 | | | + | | | | | {6.4.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 391- 400 | 8 | 4.3 | 6 | 5 | 6.5.8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 5 | 5 | 9 |11 | 1: 1.22 + | | | | | | | | | | | | | | | | + 26 | 401- 410 | 9.9.9.8 | 3 | {7.7.7.7.3 | {6.6.6.6 | 8.8.8.7 | 3.2 | {5.5.5.5 | 7.8 | {4.4.4.4 | 6.6.8.8.7 | 1 | 9 | | | + | | | | {3.7.7.6 | {6.6.5 | | | {5.5.4 | | {4.4.3 | | | | | | + | | | | | | | | | | | | | | | | + " | 411- 420 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 4 |16 | 1: 4.00 + | | | | | | | | | | | | | | | | + 28 | 421- 430 | 8 | {4.4.4.4 | 7.6 | {6.6.3.6 | 7 | {3.3.3.3 | 5.5.5.4 | 9.7.7.5.8 | 4.4.4.3 | 8.7 | 2 | 8 | | | + | | | {4.4.3 | | {6.6.6.5 | | {3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 431- 440 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {7.6.5.4 | | | | | | | + " | 441- 450 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | {3.2.1.5 | 4.3 | 7 | 2 | 8 | 8 |22 | 1: 2.75 + | | | | | | | | | {7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + 29 | 451- 460 | 8 | 3 | 6 | 6.6.6.5 | 8.6.7 | {3.3.3.3 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | | | + | | | | | | | {3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 461- 470 | 8 | 4.3 | 6 | 5 | 8.7 | 3.2 | 3.2.3.4 | 7.8 | 4.3 | 7 | 4 | 6 | | | + " | 471- 480 | 8 | 4.4.3 | 7.7.6 | 6.6.5 | 7 | 2 | 5.5.5.5.5.4 | 7.8 | 4.4.3 | 7 | 4 | 6 |13 |17 | 1: 1.31 + | | | | | | | | | | | | | | | | + 30 | 481- 490 | 8 | {4.4.4.4 | 7.7.6 | 6.6.6.5 | 8.6.6.5.7 | {3.1.3.3 | 5.5.5.4 | 8 | 4.4.4.3 | 7 | 3 | 7 | | | + | | | {4.4.3 | | | | {3.3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 491- 500 | 8 | 4.3 | 7.7.7.6 | 6.6.5 | 8.8.7 | 3.3.3.3.2 | 5.4 | {9.9.7.4 | 3 | 8.8.7 | 2 | 8 | 5 |15 | 1: 3.00 + | | | | | | | | | {9.6.8 | | | | | | | + July | | | | | | | | | | | | | | | | + 1 | 501- 510 | 9.7.9.8 | 4.3 | 6 | 6.5 | 8.6.7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 511- 520 | {9.7.7.7 | 4.3 | 7.6 | 6.4.5 | 7 | 3.2 | 4 | 8 | 4.4.4.3 | 8.6.5.6.7 | 3 | 7 | 6 |14 | 1: 2.33 + | | {7.9.8 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 2 | 521- 530 | 9.8 | 3 | 7.5.7.6 | 6.4.5 | 8.7 | 2 | 4 | 8 | 3 | 7 | 6 | 4 | | | + | | | | | | | | | | | | | | | | + " | 531- 540 | 9.9.7.8 | 3 | 7.4.6 | 5 | 6.6.7 | 3.3.2 | 3.4 | 7.3.5.4.8 | 4.3 | {8.8.6.5 | 2 | 8 | 8 |12 | 1: 1.50 + | | | | | | | | | | | {4.5.7 | | | | | + | | | | | | | | | | | | | | | | + 3 | 541- 550 | 8 | 4.3 | 6 | {6.6.6.6 | 6.8.7 | 3.3.3.2 | 5.5.4 | 9.6.9.6.8 | 4.3 | 7 | 3 | 7 | | | + | | | | | {6.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 551- 560 | 9.9.7.8 | 4.3 | 6 | 5 | 8.6.5.7 | {3.3.3.3 | 5.4 | {7.6.5.7 | 3 | 7 | 4 | 6 | 7 |13 | 1: 1.86 + | | | | | | | {3.2 | | {9.7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + 5 | 561- 570 | 8 | 4.3 | 7.6 | 6.5 | {8.8.8.8 | {3.3.3.3 | 5.5.5.5.4 | 8 | 4.4.4.3 | 8.8.8.8.7 | 2 | 8 | | | + | | | | | | {8.8.7 | {3.3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 571- 580 | 9.8 | 4.4.4.3 | 6 | 6.5 | 8.8.7 | {3.3.3.3.3 | {5.5.5.5.5 | 7.6.8 | 4.4.3 | 7 | 2 | 8 | 4 |16 | 1: 4.00 + | | | | | | | {3.3.3.2 | {5.5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | + 6 | 581- 590 | 9.8 | 4.3 | 7.7.6 | 6.6.5 | 7 | 2 | 5.4 | 7.8 | 4.3 | 7 | 3 | 7 | | | + " | 591- 600 | 8 | 3 | 6 | 4.5 | 6.6.6.7 | 2 | 5.3.5.4 | 8 | 4.4.3 | 8.8.8.7 | 5 | 5 | 8 |12 | 1: 1.50 + 7 | 601- 610 | 8 | 1.3 | 6 | 5 | 6.5.7 | 2 | 5.4 | 5.6.6.6.7.8 | 4.3 | 7 | 5 | 5 | | | + | | | | | | | | | | | | | | | | + " | 611- 620 | {9.7.7.7.9 | 3 | 6 | 5 | 6.5.6.5.7 | 3.2 | 5.4 | 7.9.7.9.8 | {4.4.4.4 | 8.7 | 3 | 7 | 8 |12 | 1: 1.50 + | | {7.7.7.8 | | | | | | | | {4.4.4.3 | | | | | | + | | | | | | | | | | | | | | | | + 8 | 621- 630 | {9.9.9.7.9 | 4.3 | 6 | 6.6.6.5 | {8.8.8.8 | 3.2 | 5.4 | 7.6.8 | 3 | 7 | 3 | 7 | | | + | | {9.9.8 | | | | {5.6.5.7 | | | | | | | | | | + | | | | | | | | | {7.6.5.7 | | | | | | | + " | 631- 640 | 9.8 | 3 | 6 | 6.5 | 7 | 3.2 | 4 | {6.5.4.6 | 3 | 7 | 6 | 4 | | | + | | | | | | | | | {9.7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 641- 650 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 7.9.6.7.9.8 | 3 | 8.6.8.7 | 8 | 2 |17 |13 | 1: 0.76 + 9 | 651- 660 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 7.6.7.6.8 | 3 | 8.6.8.8.4.7 | 8 | 2 | | | + " | 661- 670 | 9.9.8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 7.6.7.6.8 | 4.3 | 5.6.8 | 3 | 7 |11 | 9 | 1: 0.82 + | | | | | | | | | | | | | | | | + 10 | 671- 680 | 9.8 | 3 | 5.4.5.6 | 5 | 6.4.8.6.7 | 3.2 | {3.5.3.2.3 | {7.6.5.6 | 3 | 5.4.3.7 | 3 | 7 | | | + | | | | | | | | {5.3.5.2.4 | {5.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 681- 690 | 8 | 4.3 | 6 | 5 | 7 | 2 | 5.4 | 8 | 3 | 6.8.7 | 7 | 3 |10 |10 | 1: 1.00 + 12 | 691- 700 | 7.8 | 3 | 5.6 | 5 | 7 | 3.2 | 3.4 | 7.7.7.7.8 | 4.2.2.3 | 8.7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 701- 710 | 9.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | {7.6.5.4.3 | 3 | 8.7 | 2 | 8 | | | + | | | | | | | | | {2.1.4.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 711- 720 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | {7.6.5.4.3 | 3 | {6.5.4.3.6 | 4 | 6 | 9 |21 | 1: 2.33 + | | | | | | | | | {2.5.9.8 | | {5.4.3.8.7 | | | | | + | | | | | | | | | | | | | | | | + 13 | 721- 730 | 7.8 | 4.3 | 6 | 4.3.6.5 | 4.6.5.4.7 | 2 | 4 | {6.5.4.3 | 3 | {5.4.3.6 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | {2.1.8 | | {8.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {4.7.5.4 | | | | | | | + 14 | 731- 740 | 8 | 3 | 5.5.6 | 5 | {5.6.5.5 | 3.2 | 4 | {7.7.4.6 | 3 | 4.6.7 | 5 | 5 | | | + | | | | | | {8.8.7 | | | {5.6.8 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {5.4.5.5.4 | | {4.4.4.5.5 | | | | | + " | 741- 750 | 8 | 3 | 5.6 | 5 | {6.5.6.6 | 2 | 4 | {5.6.4.4.4 | 3 | {5.4.8.8.4 | 6 | 4 |11 | 9 | 1: 0.82 + | | | | | | {6.8.4.7 | | | {7.6.8 | | {5.5.6.4.7 | | | | | + | | | | | | | | | | | | | | | | + 15 | 751- 760 | 7.7.9.7.8 | 3 | 6 | 5 | 6.6.7 | 2 | 4 | 6.6.8 | 3 | {6.6.6.8 | 6 | 4 | | | + | | | | | | | | | | | {5.6.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | {5.4.6.6.5 | | | | | + " | 761- 770 | 8 | 3 | 5.6 | 5 | 6.6.6.6.7 | 2 | 3.4 | 5.4.7.8 | 3 | {5.3.5.8.5 | 5 | 5 |11 | 9 | 1: 0.82 + | | | | | | | | | | | {5.5.7 | | | | | + | | | | | | | | | {4.6.7.6.9 | | | | | | | + 16 | 771- 780 | 7.7.7.8 | 3 | 6 | 4.5 | 5.7 | 2 | 3.4 | {7.7.5.5 | 3 | (5.6.8.5 | 4 | 6 | | | + | | | | | | | | | {6.6.6.8 | | {3.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {6.6.7.2 | | | | | | | + " | 781- 790 | 7.8 | 3 | {4.5.4.3 | {4.6.4.4 | {4.4.6.8 | 2 | 3.4 | {3.4.4.4 | 3 | 6.7 | 3 | 7 | 7 |13 | 1: 1.86 + | | | | {2.6 | {1.4.3.5 | {5.7 | | | {9.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + 17 | 791- 800 | 7.8 | 2.3 | 6 | {4.4.4.3.6 | 4.8.4.6.7 | 2 | 4 | {5.7.6.6.1 | 3 | 5.7 | 4 | 6 | | | + | | | | | {2.4.2.5 | | | | {7.4.4.8 | | | | | | | + | | | {2.4.4.4.2 | | | | | | | | | | | | | + " | 801- 810 | 7.8 | {4.2.4.1.4 | 5.7.6 | 5 | 5.7 | 2 | 3.5.5.4 | 6.8 | {2.4.4.2 | 6.8.7 | 2 | 8 | 6 |14 | 1: 2.33 + | | | {2.4.3 | | | | | | | {4.2.4 3 | | | | | | + | | | | | | | | | | | | | | | | + 19 | 811- 820 | 7.9.7.8 | 2.4.2.4.3 | 5.7.6 | 3.6.4.6.5 | 7 | 2 | 3.5.4 | 6.8 | 4.4.3 | 6.8.7 | 2 | 8 | | | + " | 821- 830 | 7.8 | 2.4.4.3 | 6 | 4.6.6.6.5 | 6.8.7 | 2 | 3.5.5.5.4 | 6.8 | 2.4.3 | 6.5.7 | 2 | 8 | | | + " | 831- 840 | 7.9.8 | 2.4.4.2.4.3 | 7.6 | 5 | 7 | 2 | 4 | 7.6.4.6.8 | 2.4.3 | 6.8.7 | 4 | 6 | 8 |22 | 1: 2.75 + 20 | 841- 850 | 7.8 | 3 | 5.7.6 | 4.6.5 | 6.8.7 | 2 | 3.5.4 | 3.5.8 | 2.4.3 | 6.8.6.8.7 | 2 | 8 | | | + " | 851- 860 | 8 | 2.4.3 | 6 | 3.6.5 | 5.7 | 2 | 2.5.4 | 4.7.8 | 2.4.3 | 4.4.6.7 | 3 | 7 | | | + " | 861- 870 | 7.8 | 2.4.3 | 6 | 5 | 7 | 2 | 2.4 | 6.8 | 2.4.3 | 4.7 | 4 | 6 | 9 |21 | 1: 2.33 + 21 | 871- 880 | 7.9.8 | 2.4.3 | 5.7.6 | {4.6.4.6 | 4.6.7 | 2 | 3.5.3.5.4 | 5.7.8 | 2.4.3 | 5.7 | 1 | 9 | | | + | | | | | {3.2.4.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 881- 890 | 7.8 | 2.4.2.3 | 3.5.7.6 | 3.4.6.4.6.5 | 4.6.5.6.7 | 2 | 4 | 6.8 | 3 | 4.6.5.7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 891- 900 | 7.8 | 2.4.3 | 5.7.6 | 4.5 | 5.7 | 3.3.3.2 | 4 | {4.6.5.7.6 | 2.4.3 | 5.7 | 1 | 9 | 5 |25 | 1: 5.00 + | | | | | | | | | {4.2.4.8 | | | | | | | + | | | | | | | | | | | | | | | | + 22 | 901- 910 | 7.8 | 2.4.3 | 5.7.6 | 4.6.5 | 6.8.7 | 2 | 2.5.4 | 5.6.8 | 2.3 | 6.7 | 1 | 9 | | | + " | 911- 920 | 7.8 | 2.3 | 5.6 | 4.5 | 5.7 | 2 | 3.4 | 4.6.8 | 2.3 | 5.6.7 | 1 | 9 | 2 |18 | 1: 9.00 + | | | | | | | | | | | | | | | | + 23 | 921- 930 | 7.8 | 2.3 | {3.2.4.4 | 5 | 4.6.5.6.7 | 2 | 3.2.4 | 5.4.6.8 | 2.3 | {4.5.4.3.5 | 2 | 8 | | | + | | | | {5.6 | | | | | | | {6.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + 23 | 931- 940 | 7.9.7.8 | 3 | 5.4.6 | 5 | 5.7 | 2 | 4 | 6.7.8 | 3 | 6.8.7 | 5 | 5 | | | + " | 941- 950 | 7.8 | 3 | 5.6 | 4.6.5 | 7 | 2 | 3.5.4 | 5.6.8 | 2.3 | 6.7 | 3 | 7 |10 |20 | 1: 2.00 + | | | | | | | | | | | | | | | | + 24 | 951- 960 | 7.8 | 2.3 | {2.7.7.4 | 4.6.5 | 5.7 | 2 | 4 | 4.6.8 | 3 | 6.8.7 | 3 | 7 | | | + | | | | {5.7.4.6 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 961- 970 | 7.9.7.8 | 3 | 6 | 5 | (6.8.6.8 | 2 | 5.5.3.4 | 7.8 | 3 | 7 | 6 | 4 | 9 |11 | 1: 1.22 + | | | | | | {6.7 | | | | | | | | | | + | | | | | {4.2.6.4 | | | | | | | | | | | + 26 | 971- 980 | 7.9.7.8 | 3 | 6 | {6.4.6.4 | 7 | 2 | 4 | 6.8 | 3 | 6.8.7 | 6 | 4 | | | + | | | | | {6.1.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 981- 990 | 7.9.7.8 | 3 | 6 | 5 | 7 | 2 | 4 | 7.6.8 | 3 | 6.8.7 | 7 | 3 | | | + | 991-1000 | 7.8 | 3 | 6 | 5 | 6.8.5.7 | 2 | 4 | 6.8 | 4.2.3 | 6.5.7 | 5 | 5 |18 |12 | 1: 0.67 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + In |trials 1001| to 1100 the | right door |was indicated | by being |raised before | the choice | was made. | | | | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 30 | 1101-1110 | 8 | 4.3 | 7.6 | 6.6.5 | 7 | 2 | 5.4 | {7.7.7.7.7 | 3 | 6.6.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | {7.6.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {7.7.6.7 | | | | | | | + 31 | 1111-1120 | 7.7.8 | 3 | 7.6 | 5 | 6.7 | 3.3.2 | 4 | {7.6.6.7 | 4.4.4.3 | 7 | 4 | 6 | | | + | | | | | | | | | {6.6.8* | | | | | | | + | | | | | | | | | | | | | | | | + " | 1121-1130 | 8 | 4.3 | 6 | 6.5 | 8.7 | 3.2 | 5.4 | 7.8 | 3 | 7 | 4 | 6 | 8 |12 | 1: 1.50 + August | | | | | | | | | | | | | | | | + 2 | 1131-1140 | 8 | 4.4.3 | 6 | 5 | 7 | 3.3.3.2 | 4 | 7.8 | 4.3 | 7 | 6 | 4 | | | + " | 1141-1150 | 7.8 | 4.4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | 9 |11 | 1: 1.22 + 3 | 1151-1160 | 7.9.8 | 4.3 | 7.6 | 5 | 6.7 | 2 | 5.4 | 7.6.7.8 | 4.3 | 6.7 | 2 | 8 | | | + " | 1161-1170 | 8 | 4.3 | 6 | 5 | 7 | 2 | 5.4 | 7.8 | 4.3 | 7 | 6 | 4 | 8 |12 | 1: 1.50 + 4 | 1171-1180 | 8 | 4.3 | 6 | 6.5 | 6.7 | 3.2 | 5.4 | 7.8 | 4.3 | 6.5.6.7 | 2 | 8 | | | + " | 1181-1190 | 8 | 3 | 6 | 5 | 7 | 3.3.2 | 4 | 7.8 | 3 | 7 | 8 | 2 |10 |10 | 1: 1.00 + 5 | 1191-1200 | 7.8 | 4.4.3 | 6 | 5 | 6.7 | 3.3.3.2 | 4 | 6.7.8 | 3 | 7 | 5 | 5 | | | + | 1201-1210 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 3 | 7 | 5 | 5 | | | + " | 1211-1220 | 7.8 | 3 | 7.6.5 | 5 | 7 | 2 | 4 | 7.7.6.7.8 | 3 | 7 | 7 | 3 |17 |13 | 1: 0.76 + | | | | | | | | | | | | | | | | + 6 | 1221-1230 | 8 | 3 | 6 | 5 | {6.5.6.6 | 2 | 4 | {5.6.5.7 | 3 | 6.8.6.7 | 7 | 3 | | | + | | | | | | {5.6.5.7 | | | {9.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 1231-1240 | 7.8 | 3 | 6 | 4.5 | 7 | 2 | 4 | 6.7.8 | 3 | 6.7 | 6 | 4 |13 | 7 | 1: 0.54 + 7 | 1241-1250 | 7.8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 8.7 | 8 | 2 | | | + " | 1251-1260 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 7 | 3 | | | + " | 1261-1270 | 8 | 3 | 6 | 5 | 7 | 3.2 | 5.3.4 | 8 | 3 | 7 | 8 | 2 |23 | 7 | 1: 0.30 + 9 | 1271-1280 | 8 | 3 | 6 | 5 | 7 | 2 | 5.4 | 9.7.8 | 3 | 7 | 8 | 2 | | | + " | 1281-1290 | 8 | 3 | 6 | 5 | 7 | 3.2 | 4 | 7.8 | 3 | 7 | 8 | 2 |16 | 4 | 1: 0.25 + 10 | 1291-1300 | 7.8 | 3 | 7.6 | 5 | 6.7 | 3.2 | 4 | 6.7.8 | 3 | 7 | 5 | 5 | | | + " | 1301-1310 | 7.8 | 4.3 | 5.6 | 4.5 | 6.7 | 2 | 4 | 6.8 | 3 | 6.8.7 | 3 | 7 | | | + " | 1311-1320 | 7.8 | 3 | 6 | 5 | 5.7 | 2 | 4 | 5.7.8 | 3 | 4.6.8.7 | 6 | 4 |14 |16 | 1: 1.14 + 11 | 1321-1330 | 7.8 | 3 | 6 | 5 | 6.7 | 3.2 | 4 | 4.6.7.8 | 2.3 | 5.7 | 4 | 6 | | | + " | 1331-1340 | 7.8 | 3 | 6 | 4.5 | 6.7 | 2 | 4 | 6.7.8 | 3 | 7 | 6 | 4 |10 |10 | 1: 1.00 + 12 | 1341-1350 | 9.8 | 3 | 6 | 5 | 6.7 | 2 | 4 | 6.7.8 | 3 | 6.7 | 6 | 4 | | | + " | 1351-1360 | 7.8 | 3 | 6 | 5 | 6.7 | 2 | 4 | 7.8 | 3 | 6.7 | 6 | 4 |12 | 8 | 1: 0.67 + 19 | 1361-1370 | 7.8 | 3 | 6 | 5 | 6.7 | 2 | 4 | 6.7.8 | 3 | 6.7 | 6 | 4 | | | + | 1371-1380 | 9.8 | 3 | 6 | 5 | 7 | 3.2 | 4 | 7.9.8 | 3 | 6.8.7 | 6 | 4 |12 | 8 | 1: 0.67 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +After two hundred and fifty trials on problem 2 had been given Julius, +it seemed desirable to introduce a radical change in method in order to +stimulate him to maximal effort. It was therefore decided to force him +to make a round trip through the apparatus in connection with each +choice, and to let this forced labor serve, in the place of confinement, +as punishment for mistakes. This new method yielded peculiar and +characteristic results. They differ from those previously obtained +largely because of the orang utan's remarkably strong tendency to +reenter the box through which he had just passed. This occurred so +persistently, as may be seen in table 9 (June 17, second series, June +18, etc.), that a further modification of method was introduced in that +after the same wrong box had been entered five times in succession, the +experimenter on the next choice of the box confined the animal for a +stated interval, say sixty seconds, in it, and then allowed it to escape +by way of the exit door and choose repeatedly until it finally located +the right box. Were it not for this particular feature of the method, +the number of choices recorded after June 17 would unquestionably be +very much greater than the table indicates. + +The new method proved a severe test of the orang utan's patience and +perseverance, for he had to work much harder than formerly for his +reward, and often became much fatigued before completing the regular +series of ten trials. Early in the use of this method, he developed the +habit of rolling around from exit door to starting point by a series of +somersaults. When especially discouraged he would often bump his head +against the floor so hard that I could hear the dull thud. As has been +noted, I found it desirable to vary the procedure repeatedly. It proved +especially interesting to give one series per day with the round trip as +punishment and another series with confinement as punishment. + +Day after day, as the experiment progressed, slight or great +fluctuations of the ratios of right to wrong choices appeared, but +without consistent improvement. There was, to be sure, as the last +column of table 9 shows, a radical improvement during the first six +hundred and fifty trials, for the number of right choices per series +increased from 0 to 8. But, as the observations were continued from day +to day, it became more and more evident that the animal was merely +passing from tendency to tendency--method to method--mixing tendencies, +and occasionally developing new ones, without approach to the solution +of the problem. This fact would have led me to discontinue the work much +earlier than I actually did had it not been for the peculiarity of the +results obtained with problem 1. It seemed not improbable that at any +time Julius might succeed in perfectly solving this problem over night +precisely as he had solved the first problem. + +A curiously interesting bit of behavior appeared for the first time on +June 29. Julius had gone to the first box at the right end of the group, +and instead of entering, he had wheeled around toward his right, and +turning a complete circle, faced the right box, which he promptly +entered. Subsequently, the tendency developed and the method was used +with increasing frequency. On June 30, it appeared in the first series, +four times, in the second series, six times; on July 1, in the first +series, three times, and in the second series, four times; on July 2, in +the first series, five times, and in the second series, nine times. It +was indeed only by accident that the animal failed to fulfill the +technical requirement for perfect solution of the problem in this +series. Yet, had he done so, his subsequent trials would doubtless have +revealed the lack of any other idea than that of turning completely +around before entering a box. + +This odd bit of behavior proved peculiarly interesting and significant +in that the tendency to turn became dissociated from the position (in +front of the first box at the right end of the group) in connection with +which it originally developed. After a few days, Julius would enter the +reaction-chamber and instead of proceeding directly to the right end of +the group, would stop suddenly wherever he happened to be, turn toward +his right in a complete circle, and hasten into the box nearest to him +which, as often as not, proved to be the wrong one. Thus the idea of +turning completely about, which had it continued its association with +the idea of facing the first box at the right, would have yielded +success, instead became useless because of its dissociation. That the +orang utan is capable of using free ideas seems clear enough in the +light of this behavior. That he proved incapable of getting the idea of +second from the right end is as clearly shown by the detailed results of +table 9,--the fruits of weeks of experimenting. + +Certain other interesting tricks developed in Julius's behavior. Thus, +on July 5, there appeared the tendency to move as though about to enter +the right box (feint), then to stop suddenly and promptly enter another +box, which was, of course, a wrong one. The reason for the development +of this tendency could not be discovered, but in connection with it, +there appeared another tendency which possibly can be explained. Julius +took to backing into the chosen box so that he could face the +experimenter. He would then, after a period of hesitation, come out and +promptly enter one of the other boxes. This tendency was apparently due +to the fact that during one or two series the experimenter growled at +the orang utan every time he made a mistake. The growl startled him and +caused him to look around. He evidently felt the need of keeping his +eyes on the experimenter,--Hence the backing into the open box. The +tendency disappeared shortly after the experimenter gave up the use of +the growl as a method of punishing the animal for what were suspected to +be careless choices. + +Curiously enough, it was not until July 10 that direct choice of the +right box was made at all frequently. Previously, selection of it had +been made almost invariably after approach to other boxes. But in the +second series for July 10 there was an extraordinary improvement in +method. This developed in the presence of two visitors, and it is +therefore all the more surprising. The choices were made not only +directly, but with decision and evident certainty that was quite at +variance with the previous behavior of the animal. + +All the while through variation of methods, I was seeking to discover +the best means of holding the orang utan to his maximum effort and care +in attempting to select the right box. One day it would seem as though +forcing him to make round trips with rewards only for correct first +choices proved most satisfactory, and the next it might seem equally +clear that punishment by confinement for thirty seconds or sixty +seconds, with reward for correct choice in every trial, yielded better +results. In the end I had to admit that no best method had been +demonstrated and that I had failed to develop conditions which served to +compel the animal's attention to the problem and to lead him to work +without discouragement. There were, it is true, days on which it seemed +practically certain that the problem would be solved, but as it turned +out, Julius never succeeded in choosing correctly--throughout a series +of ten trials. + +As a last resort, in order to make perfectly sure that the orang utan +was doing his best, I decided to introduce corporal punishment in a mild +form. For this purpose, I placed my assistant in charge of the apparatus +and the series of trials, and stationed myself in one corner of the +reaction-chamber with a whip in my hand. Whenever Julius entered a wrong +box, I approached him with the whip and struck at him, being careful not +to injure him and rarely striking him at all, for the threat was more +effective than a blow. He was extremely afraid of the whip and would +begin to whine and attempt to get out of the way as soon as he saw it. + +This method was introduced on August 10, but no improvement resulted, +and in the end there was no reason to consider it more satisfactory than +the other procedures. I am now wholly convinced that Julius did his best +to choose correctly in the majority of the numerous series which were +given him in connection with problem 2. + +From trials 1001 to 1100, a radical departure from the previous methods +was introduced in that the right box was indicated to the animal by the +slight and momentary raising of its exit door. Of course no records of +the choices for this group of one hundred trials appear in table 9, for +the simple reason that the animal inevitably and immediately entered the +right box. It was thought that this method might serve to break up the +previously developed tendencies toward inadequate forms of response and +so encourage the animal that he would later solve the problem when given +opportunity to select the right box without aid from the experimenter. +But as a matter of fact, while the ratio of right to wrong first choices +was 1 to .67 in the series preceding this change of method, it was 1 to +1.50 in the first series following its use. There is no satisfactory +evidence that Julius profited by this experience, though as a matter of +fact he did succeed in making his best daily record, eight right to two +wrong choices, on August 4, after 1190 trials. + +The curve of learning for this problem has been plotted and is presented +in figure 19. It is of course incomplete and it is offered only to +indicate the extreme irregularity in performance. + + +_Problem 1a. First at the Right End_ + +It was decided on August 19 that the further continuation of the work of +Julius on problem 2 was not worth while. He had become much discouraged, +and although willing to work for food, gave no indications whatever of +improvement and seemed to have exhausted his methods. It seemed wise +instead of giving up work with him in the multiple-choice method to +return to a form of problem 1. We may designate it as problem 1a. The +right box is definable as the first at the right end of the series +instead of the first at the left end as in the original problem 1. It +was thought possible that Julius might quickly solve this problem by a +process similar to that used for problem 1. + +Work was begun on problem 1a, August 20, and for six successive days two +series of trials per day were given, the settings for which as well as +the resulting choices are given in table 10. Most notable in these +results is the large number of cases in which Julius chose first the +second box from the right end of the series, or in other words that box +which had been the right one in problem 2. Contrary to expectation, he +showed no inclination to abandon this tendency to choose the second from +the right end, and the ratio of right to wrong choices changed in the +direction opposite from expectation, beginning with 1 to 4 and ending on +the sixth day with 0 to 20. + +It was obviously useless to continue the experiment further since Julius +had given up his attempts to locate the right box in the first choice +and was apparently satisfied to discover it by a process of trial and +error. He had, it would seem, satisfied himself that the problem was +insoluble. These results obtained in problem 1a constitute a most +interesting comment on the effects of problem 2 on the orang utan. +Behavior similar to that which he developed well might have been +obtained from a child of three to four years placed in a like situation +and forced to strive, day after day, to solve a problem beyond its +ideational capacity. + +In many respects the most interesting and to the experimenter the most +surprising result of this long series of observations with Julius was +the lack of consistent improvement. It seemed almost incredible that he +should continue, day after day, to make incorrect choices in a +particular setting while choosing correctly in some other setting which +from the standpoint of the experimenter was not more difficult. + + + +TABLE 10 + +Results for Orang utan in problem 1a + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | | 1.2.3.4 | R | W | R | W | of + | trials | 5.63 | 1.2.3.4 | 6.7.8.9 | 2.3.4.5 | 3.4.5.6.7 | 1.2.3 | 5.6.7.8 | 1.2 | 2.3.4.5.6 | 5.6.7 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + August | | | | | | | | | | | | | | | | + 20 | 1- 10 | 6 | 3.4 | 6.7.8.9 | 4.5 | 6.7 | 3 | 7.8 | 2 | 5.5.6 | 6.7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 11- 20 | 5.6 | 3.4 | {7.8.7.8 | 4.5 | 6.7 | 2.3 | {7.6.7.7 | 2 | 5.6 | 6.7 | 1 | 9 | 4 |16 | 1: 4.00 + | | | | {8.7.8.9 | | | | {6.7.7.8 | | | | | | | | + | | | | | | | | | | | | | | | | + 21 | 21- 30 | 5.6 | 3.4 | {7.8.7.6 | 4.5 | 6.7 | 2.3 | 7.8 | 2 | 5.6 | 5.7 | 1 | 9 | | | + | | | | {8.7.9 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 31- 40 | 5.6 | 3.4 | 7.7.6.8.9 | 4.5 | 6.7 | 3 | 6.7.8 | 2 | 6 | 6.7 | 3 | 7 | 4 |16 | 1: 4.00 + 23 | 41- 50 | 5.6 | 3.4 | 7.8.9 | 4.5 | 6.7 | 2.3 | 6.7.8 | 2 | 5.6 | 5.6.7 | 1 | 9 | | | + " | 51- 60 | 5.6 | 3.4 | 7.8.9 | 4.5 | 6.7 | 2.3 | 6.8 | 2 | 5.6 | 6.7 | 1 | 9 | 2 |18 | 1: 9.00 + 24 | 61- 70 | 5.6 | 3.4 | 6.8.9 | 4.5 | 5.7 | 2.3 | 6.7.8 | 1.2 | 5.6 | 6.7 | 0 |10 | | | + " | 71- 80 | 5.6 | 3.4 | 6.7.8.9 | 4.5 | 5.7 | 2.3 | 5.7.8 | 2 | 5.6 | 6.7 | 1 | 9 | 1 |19 | 1:19.00 + 25 | 81- 90 | 5.6 | 3.4 | 6.7.8.9 | 5 | 5.6.7 | 2.3 | 7.8 | 1.2 | 5.6 | 4.5.6.7 | 1 | 9 | | | + " | 91-100 | 5.6 | 3.4 | 6.7.8.9 | 3.4.5 | 6.6.7 | 2.3 | 6.7.8 | 1.2 | 5.6 | 6.7 | 0 |10 | 1 |19 | 1:19.00 + | | | | | | | | | | | | | | | | + 26 | 101-110 | 5.6 | 3.4 | {6.7.8.8 | 3.5 | 5.6.7 | 2.3 | 5.6.7.6.7.8 | 1.2 | 5.6 | 6.7 | 0 |10 | | | + | | | | {6.7.6.9 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + | | | | {6.7.8.8 | | | | | | | | | | | | + " | 111-120 | 5.6 | 2.3.4 | {6.7.8.7 | 3.4.5 | 5.6.7 | 2.3 | 7.8 | 1.2 | 5.6 | 4.5.6.7 | 0 |10 | 0 |20 | 0:20.00 + | | | | {6.7.9* | | | | | | | | | | | | + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + + +[Footnote *: Aided by experimenter.] + + + +The evidence suggests that in this young orang utan ideational learning +tended to replace the simpler mode of problem solution by trial and +error. Seemingly incapable of solving his problems by the lower grade +process, he strove persistently, and often vainly, to gain insight. He +used ideas ineffectively. Animals far lower in intelligence (e.g., the +pig), surpass him in ability to solve these relational problems because +they use the method of elimination by trial consistently and +effectively. Julius, in these experiments, made a poor showing because +his substitute for trial and error is only slightly developed. Would he +have succeeded better with the same problems if mentally mature? + +There are many important features of the results which, for lack of +space, have not been indicated or discussed. They can be developed from +later comparative studies of the data, for in the tables appear all of +the essential facts of response apart from those mentioned in the text. + + + +IV + +RESULTS OF SUPPLEMENTARY TESTS OF IDEATIONAL BEHAVIOR + + +1. Julius, _Pongo pygmaeus_ + + +_Box Stacking Experiment_ + +In addition to the multiple-choice experiments which have been described +in detail in the previous section, it was possible to conduct certain +less systematic tests of ideational behavior in the monkeys and the +orang utan. From the technical standpoint these tests were relatively +unsatisfactory because only inexactly describable. But their results are +in many respects more interesting, if not also more important, in the +light which they throw on ideation than are those previously presented. +First, in order of time, comes a test which may be designated as the box +stacking experiment. The method will now be described in connection with +an account of the behavior of Julius as contrasted with that of a child +of three years and four months of age. + +In the large central cage labelled Z, figure 12, which was twenty-four +feet long, ten feet wide, and ten to twelve feet deep, the following +situation was arranged. From the center of the wire covering of the +cage, a banana was suspended on a string so that it was approximately +six feet from the floor, five feet from either side of the cage, and +twelve feet from either end. From all approaches it was far beyond the +reach of Julius, since it was impossible for him to climb along the wire +roof and thus reach the string. Two boxes were placed on the floor of +the cage several feet from the point directly under the banana. The one +of these boxes was heavy and irregular in shape, as is shown in figures +21, 23 and 24 of plate V. Its greatest height was twenty-one inches; its +least height, eighteen inches; its other dimensions, twelve and sixteen +inches respectively. The smaller and lighter box measured twenty-two by +twelve by ten inches. According to the experimenter's calculations, the +only way in which Julius could obtain the banana was by placing the +smaller box upon the larger and then climbing upon them. + +At 10 a.m. on March 5, Julius was admitted to the large cage, and the +banana was pointed out to him by the experimenter. He immediately set +about trying to get it, and worked diligently during the whole of the +period of observation, which, because of the unfinished condition of +some of the cages, was limited to slightly over ten minutes. Within this +period he made upward of a dozen fairly well directed attempts to obtain +the food. Chief among them were three attempts to reach the banana from +different positions on the left wall of the cage (as the experimenter +faced the laboratory); two attempts to reach it from different positions +on the right wall; two from the large box in positions nearly under the +banana; two from the large box with the aid of the experimenter's hand; +and one from the distant end of the cage(?). There occurred, also, less +definite and easily describable efforts to get at the reward. + +On account of the unfinished condition of the cages, the experimenter +had to remain in the large cage with Julius during the test. This +interfered with the experiment because the animal tended both to try to +escape and to get the experimenter to help him with his task. +Particularly interesting is the latter sort of behavior. After the orang +utan had made two or three futile attempts to obtain the food he came to +the experimenter, who was standing in one corner of the cage, took him +by the hand, and led him to a point directly under the banana. He then +looked up toward the banana, grasped the experimenter's arm, raised it, +and then tried to pull himself up. He was not allowed to get the food by +climbing up on the experimenter. A few minutes later, he again led the +experimenter toward the banana, but receiving discouragement in this +activity, he proceeded to devote himself to other methods. + +Apart from the distractions which have been mentioned above, Julius's +attention to the food was surprisingly constant. Whatever his position +with respect to it, he seemed not for an instant to lose his motive, and +to whatever part of the cage he went and whatever he did during the +interval of observation was evidently guided by the strong desire to +obtain the banana. Frequently he would look directly at it for a few +seconds and then try some new method of reaching it. His gaze was +deliberate and in the handling of the boxes he accurately gauged +distances. Several times he succeeded in placing the larger box almost +directly under the banana, and repeatedly he located that portion of the +side wall from which he could most nearly reach the coveted prize. + + + +EXPLANATION OF PLATE V + +Orang utan, Julius, obtaining banana by piling boxes +or by using pole + +FIGURE 21.--Julius in act of setting larger box on end. + +FIGURE 22.--Placing smaller box on larger. + +FIGURE 23.--Balancing on larger box preparatory to reaching for banana. + +FIGURE 24.--Balancing and reaching to the utmost. + +FIGURE 25.--Standing on three boxes (after stacking them) and +reaching for reward. + +FIGURE 26.--Lifting smaller box up toward banana. + +FIGURE 27.--The act of stacking the boxes. + +FIGURE 28.--Sequel to figure 27. + +FIGURE 29.--Box and pole experiment. Pushing the second pole +into the box. + +FIGURE 30.--Pushing pole into box. + +FIGURE 31.--Enjoying the reward of success. + + + +From my notes I quote the following comment on the results of the +initial experiment: "Despite all that has been written concerning the +intelligent behavior of the orang utan, I was amazed by Julius's +behavior this morning, for it was far more deliberate and apparently +reflective as well as more persistently directed toward the goal than I +had anticipated. I had looked for sporadic attempts to obtain the +banana, with speedy discouragement and such fluctuations of attention as +would be exhibited by a child of two to four years. But in less than ten +minutes Julius made at least ten obvious and well directed attempts to +reach the food. There were also wanderings, efforts to obtain aid from +the experimenter, and varied attempts to escape from the cage." + +Before proceeding further with the description of the behavior of Julius +in the box stacking test, I shall describe for contrast the behavior of +a boy three years four months of age when confronted with a situation +practically identical with that which the ape was given an opportunity +to meet. For the child, the banana was suspended, as previously +described, from the roof of the cage. The same two boxes were placed on +the floor at considerable distances from the banana, and in addition, a +light stick, about six feet long, and a piece of board, the latter by +accident, were on the floor. The child was asked to get the banana for +Julius, and he eagerly and confidently volunteered to do so. + +His behavior may best be described by enumeration of the several +attempts made. They include (1) placing the larger box nearly under the +banana and reaching from it. (2) Standing of the larger box on end with +resulting failure because the child could not stand on the sloping edges +of the top of the box. (3) The larger box was turned on its side and the +lighter box drawn up opposite it and stood on end. The child then +mounted the larger box and from it stepped to the top of the smaller. +But the boxes had not been placed beneath the banana, and when the child +reached for it, he found himself several feet away from his prize. (4) +The boxes were moved to a position nearly under the banana and another +futile attempt was made to reach it without placing the smaller box on +top of the larger one, the only position from which the child could +readily obtain it. (5) The piece of board was placed on top of the +larger box and from this height the child again reached upward. (6) The +six-foot stick was taken up and an attempt was made to strike the banana +and thus dislodge it, but it was too securely fastened to be obtained +thus. (7) Attention shifted to other things, and the child played for a +time with the board. Reminded of the banana by the experimenter, he +again tried method (3). (8) He again used the stick on the banana. (9) +The effort to knock the prize to the floor having failed, he became +discouraged and said that he must go home. (10) When told that Julius +was very hungry and wanted the banana, he repeated efforts similar to +those described in (3) and (6). + +Up to this time the observations had covered a period of twenty minutes. +The child was now taken from the cage and allowed to play about for +fifteen minutes. Asked then whether he would go back and try to get the +banana, he replied, "No, 'cause I don't want to get it," thus indicating +his discouragement with the situation. When taken into the cage, he, +nevertheless, made the additional attempts indicated below: (11) Use of +one of the boxes. (12) He remarked, "Now I know, I'll get it," and after +so saying, repeated (3). (13) Failing, he turned to me and said, "I +could get it if I was on your head," but he did not, as Julius had done, +lead me to the proper place and try to reach the banana by climbing up +or by urging me to lift him. (14) Later, he played in the boxes, +apparently forgetful of his task. Finally he remarked: "I'll get the +banana," but he made no attempt to do so, and instead, watched the +monkeys intently. Thereafter, he showed no further interest in the +solution of the problem, and the experiment, after a total period of +fifty-five minutes, was discontinued. + +Comparison of the behavior of the ape with that of the child indicates a +greater variety of ideas for the latter. Julius gauged his distances +much more accurately than the child, attended more steadily, and worked +more persistently to obtain the reward, but he did not so nearly +approach the idea of stacking the boxes as did the child, for the +latter, in placing the board on one of the boxes, exhibited in +ineffective form the idea which should have yielded the solution of the +problem. + +The child was given no further opportunity to work at the problem, +whereas Julius, as I shall now describe, continued his efforts on +subsequent days under somewhat different conditions. On Wednesday, March +10, the banana was suspended as formerly, and three boxes, all of them +small and light enough to be readily handled by the ape, were placed in +distant parts of the cage. The six-foot stick which had been present in +the test with the child, but not in the first test with Julius, was also +placed in the cage. + +Julius was allowed to work for about an hour. As formerly, he was +sufficiently hungry to be eager to get the food and evidently tried all +of the possible ways which occurred to him. Chief among these were (1) +the use of the various boxes separately or in pairs in very varied +positions but never with one upon another,--the only way in which the +banana could be reached; (2) climbing to various points on the sides of +the cage, with infrequent attempts to reach the banana. Usually his eyes +saved him the vain effort. + +Unlike the child, Julius paid little attention to the six-foot stick. +Two or three times he took it up and seemingly reached for the banana, +but in no case did he try persistently to strike it and knock it from +the string. It is but fair, however, to remark that such an act is very +difficult for the young orang utan, as compared with the child, because +of the weakness of the legs and the awkwardness of striking from a +sitting posture. As previously, the steadiness of attention and the +persistence of effort toward the end in view were most surprising. At +one time Julius walked to the end of the cage and there happened to see +one of the monkeys eating. He watched intently a few seconds and then +hastened back to the banana as if his task had been suggested to him by +the sight of the feeding animal. Most interesting and significant in +this behavior was the suddenness with which he would turn to a new +method. It often looked precisely as though a new idea had come to him, +and he was all eagerness to try it out. + +On March 11, Julius was given another opportunity to obtain the banana +by the use of the three boxes. Although he used them together he made no +effort to place one upon another. Certain of his methods are shown in +plate V, especially by figures 21, 23 and 24. + +This experiment was continued on April 2 under yet different conditions, +for this time only two boxes were placed in the cage, the one of them +the heavy, irregularly-shaped box and the other the smaller, lighter one +originally used. On the end of the heavier box had been nailed a two by +two inch wooden block in order to increase the difficulty in using this +box alone. As previously, Julius made varied attempts to obtain the +banana, but on the whole his interest and attention seemed somewhat +weaker than previously and there were indications of discouragement +because of repeated failures. + +He handled the boxes conspicuously well, and it seemed at times that he +would certainly succeed in placing the one upon the other and in +reaching the food. + +After one series of attempts from the sides of the cage and from the +large box, he deliberately turned away from the box and neatly executed +a somersault on the floor of the cage, as much as to say, "I am +disgusted with the whole situation." Again, later on the same day, after +falling from the top of the larger box, which tilted over very easily, +he rolled himself into a ball, and childlike, played with his feet. An +additional evidence of his changed affective attitude toward his task, +especially in connection with definite failures, appeared in his rough +handling and biting of the boxes. When most impatient, he worked very +roughly. + +Julius was allowed to work for the reward from thirty to ninety minutes, +or, as a rule, until he had become completely discouraged on April 3, 5, +6, 7, 8, 9 and 13. His behavior was interesting and significant, but +nothing new appeared except that his willingness to work gradually +disappeared, and on April 13, although previously hungry, he made only a +single attempt to obtain the banana and then paid no further attention +to it. + +The prolonged and varied efforts to obtain the banana were due in a +measure at least to three accidental successes. Thus on April 2, 3 and +again on the 5th, by fortunate combinations of circumstances, he +succeeded in getting the banana, contrary to the intention of the +experimenter. + +Although active at first on April 6, he soon wearied of his task and +quit work. The same was true on April 7, and again on the 8th and 9th. +On these days, although hungry, he did not care to enter the large cage +and worked only a few minutes each day, seldom making more than two or +three half-hearted attempts to obtain the banana. His attitude toward +the task had changed completely, in that hopelessness had taken the +place of eager expectancy. By the 13th of April he had so nearly given +up voluntary efforts to solve the problem that it seemed worth while to +test his ability to get the idea by watching the experimenter. For this +purpose the following test of imitation was made. + +On the morning of April 14, having placed a banana in the usual +position, I took Julius into the large cage, dragged the two boxes to +the proper position beneath the banana, placed the smaller one upon the +larger one and then climbed up on them to show the ape that I could +reach the banana. I then stepped down and gave him a chance to climb on +the boxes. He did so immediately and obtained the food. + +Another piece of banana was supplied, the boxes were placed in distant +corners of the cage, and fifteen minutes were allowed Julius so to place +them that he could obtain his reward. He gave no indications of having +profited by my demonstration, but worked with the boxes singly, usually +with the larger one. On April 16, with the banana in position and the +two boxes also in the cage, Julius was admitted and allowed to work for +five minutes, but again without success. I then placed the boxes +properly for him and he immediately climbed up and got the banana. While +he was eating, the boxes were carried to distant corners of the cage and +another banana placed in position. Now thirty minutes were allowed him +for unaided work on the problem. As formerly, the larger box was used +repeatedly and attempts to reach from the side of the cage appeared, but +there was no tendency to try to use the two boxes together. He worked +fairly persistently, however, and showed clearly the stimulating and +encouraging effect of aid from the experimenter. Once more, on April 17, +Julius was taken into the cage and allowed to watch me place the boxes +in proper position. He then climbed up and obtained the desired food. +After the bait had been renewed and the boxes displaced, he immediately +tried to use the larger one, then he reached for the small one as though +to use both together. But the impulse died out and he turned again to +the larger box as usual, standing it on end, and persistently trying to +balance himself on it. Nothing else of special interest happened during +the interval of unaided effort. + +Similarly, I placed the boxes for the ape on April 19, allowed him to +get the banana and then gave him opportunity to try for himself after +the boxes had been displaced. This time he immediately reached for the +smaller box and moved it about a little, thus indicating a new +association. He next turned to the larger box and worked with it +persistently. Later, he once more worked with the smaller box in an +unusual manner. He repeatedly stood on it, but made no attempt to lift +it or to place it on the larger box. Clearly the usually neglected +smaller box had become associated with the satisfaction of obtaining the +banana. The same method was carried out on April 20. As I placed the +boxes in position beneath the banana, Julius watched with unusual +intentness, and when it came his turn to try to obtain the food by the +use of the boxes, he began at once to work with the smaller box, but as +on April 19, he soon abandoned it and turned to the other. While I was +making note of this particular feature of his behavior, he suddenly +seized the smaller box by two corners with his hands and by one edge +with his teeth, and after a few attempts placed it on top of the larger +box, climbed up, and obtained the banana. + +Because of bad weather on April 21, the next test was made on April 22, +with everything as usual. Unaided, the ape was given an opportunity to +obtain the coveted reward, while I stood ready to obtain records of his +behavior with my camera. He wasted no time, but piled the smaller box on +top of the larger one immediately, and obtained his reward. As soon as +opportunity was offered, he repeated the performance. The same thing +happened on April 23 and several succeeding dates. + +Julius had got the idea, and the only further improvement possible was +in skill in manipulating the boxes. + +One of the curious performances which appeared during the imitative +period is pictured in figure 26, plate V, where the ape is seen lifting +the smaller box into the air. This he did three or four times one day, +raising it toward the banana each time as though he expected thus to +obtain the reward. As he did not go up with the box (according to his +expectation?), he abandoned this method, and looking about, discovered +the larger box in a distant corner. Thereupon, he promptly pulled the +boxes to their proper position beneath the banana, stacked them, and +obtained his food. + +After considerable skill had been acquired in the placing of the boxes, +the one upon the other, the height of the banana above the floor was +increased so that three boxes were necessary. Figure 25 of plate V shows +him standing on three boxes and reaching upward, and figures 22, 27 and +28 show various modes of handling the boxes and of reaching from them. +He was not at all particular as to the stability of his perch, and often +mounted the boxes when it seemed to the experimenter inevitable that +they should topple over and precipitate him to the floor. Only once, +however, during the several days of experimentation did he thus fall. + +Obviously important is the evident change in the animal's attention on +April 20. He watched with a keenness of interest which betokened a +dawning idea. Before he had succeeded in stacking the boxes, I had +written in my note-book, "He seemed much interested today, in my placing +of the boxes." Interesting, and important also, is the ease and +efficiency with which he met the situation time after time, after this +first success. "Trial and error" had no obvious part in the development +of the really essential features of the behavior. The ape had the idea +and upon it depended for guidance. + +Except for the fact that Julius was immature, probably under five years +of age, it is likely that he would have stacked the boxes spontaneously +instead of by suggestion from the experimenter or imitatively. + +No unprejudiced psychologist would be likely to interpret the activities +of the orang utan in the box-stacking experiment as other than imaginal +or ideational. He went directly, and in the most business-like way from +point to point, from method to method, trying in turn and more or less +persistently or repeatedly, almost all of the possible ways of obtaining +the coveted food. The fact that he did not happen upon the only certain +road to success is surprising indeed in view of the many ineffective +methods which he used. It seemed almost as though he avoided the easy +method. + +It is especially important, in connection with these results, to point +out the risk of misinterpretation of observations on the anthropoid +apes. If they can imitate human activities as readily and effectively as +Julius did in this particular experiment, we can never be sure of the +spontaneity of their ideational behavior unless we definitely know that +they have had no opportunity to see human beings perform similar acts. + +Of all the methods of eliciting ideational or allied forms of behavior +used in my study of the monkeys and ape, none yielded such illuminating +results as the box stacking test, and although from the technical +standpoint, it has many shortcomings, as a means to qualitative results +it has proved invaluable. + + +_Other Methods of Obtaining the Reward_ + +Some weeks later, I tried to discover how Julius would obtain the much +desired banana when the boxes were absent. I placed in the large cage a +stick about six feet long and an old broom. When admitted, he looked +about for the boxes, but not seeing them, picked up the broom and +placing it with the splints down, beneath the banana, he tried to climb +it, but as it fell over with him, he abandoned this after a few trials, +went to his cage, and picking up some old bags which he used at night as +covers, he dragged them out and placed them on the floor beneath the +banana. He next put the broom upon them and tried to climb up. This +general type of behavior persisted for several minutes, everything +within reach being used as were the bags, as a means of raising him in +the desired direction. Finally, he placed his feet on the broom where +the handle joins the splints, seized the handle near the top with his +hands, drew himself up as far as possible, and then launched himself in +the air and tried to seize the banana. On the third attempt he +succeeded. + +Later, he was given a plain stick about five feet long. Figure 32 of +plate VI shows him using this to obtain the banana in the manner +described above. He would grasp it with one or both feet, usually one, +ten to fifteen inches from the floor of the cage, meanwhile holding with +his hands near the top of the stick. He would then, with all his +strength, draw himself up suddenly and jump toward the banana. Often he +came down rather hard on the cement floor, much to his disgust. + +Yet another method of obtaining the reward developed a day or two later. +A light red-wood stick about five feet long and an inch in its other +dimensions was the only object in the cage which could possibly be of +use in obtaining the banana. The aim of the experimenter was to discover +whether Julius would use this as a club. + +Previously, in connection with the use of the boxes, he had taken up the +same stick two or three times and reached for the banana with it, but in +no case had he struck at it or clearly tried to knock it from the +string, as did the child most readily and naturally. When provided with +this same stick, and it alone, as a means of obtaining the food, he hit +upon the following interesting method. Placing one end of the stick +between a wooden brace and the wire side of the cage, he climbed up to a +level with the banana as is shown in figure 33 of plate VI. Then holding +with one hand and one foot to a timber of the cage and to the stick with +his other foot, he swung outward as far as possible and reached the +banana with his free hand. Having once succeeded by the method, he used +it whenever given an opportunity. It was impossible for him to make the +reach without the use of the small stick, while with it he succeeded +fairly easily and regularly. + + +_Box and Pole Experiment_ + +Following the box stacking test, Julius was given an opportunity to +exhibit ideation in another type of experiment. This may be designated +the box and pole test. The conditions are describable thus. A strong +wooden box eighty-four inches long, by four inches wide, by four inches +deep, with open ends, was built with one side hinged. Hasps and padlocks +enabled the experimenter to lock this "lid" after food had been placed +in the center of the box. This box could be placed in the center of the +large cage and there fastened by means of cross bars. It is well shown +in position in figure 29, plate V. Two poles each eight feet long and +approximately one and a half inches in their other dimensions were the +only additional materials in the experiment. + +On May 1, Julius was allowed to see the experimenter place a half banana +in this box, close the lid, lock it in position, and securely fasten the +box by means of the cross bars. He was then given opportunity to try to +get the banana. The two poles lay on opposite sides of the box and near +the edges of the cage. Doctor Hamilton and the writer were in the cage +watching. Julius looked into the box through one end, and seeing the +banana, reached for it. He could not obtain it in this way, so he began +to bite at the box and to pull at it with all his strength. During the +fifteen minutes allowed him, he worked at the box in a great variety of +ways, fooling with the locks which had been attached to the hasps as +well as with the cross bars and continually reaching in at the one or +the other end. He was somewhat distracted by the presence of the two +observers and attended rather unsatisfactorily to the task in hand. Not +once did he touch the poles, and it is doubtful whether he even noticed +them. He was not very hungry at this time, and after a few minutes +active work he virtually gave up trying to get the food. + +Two days later, on May 3, the box was once more placed in position, this +time with a half banana in the middle and a small piece of banana near +each open end. The two poles lay on the floor of the cage, each several +feet distant from the box. Julius was eager for food. When released he +went immediately to the box, reached in and obtained a piece of banana +from the end nearer the laboratory. He then looked in and saw the piece +near the middle of the box. His next move was to pick up the eight foot +pole and push it into the box, but before pushing it all the way +through, he stopped and began to pull at the box in various ways. +Shortly he returned to the pole and twice thrust it in as far as he +could reach. The first time, after thrusting it all the way through, he +pulled it out and examined the end as though expecting the banana to +come out with it. After a third attempt he looked into the box, +presumably seeing the banana, then turned a backward somersault, came to +the end of the cage, and looked at me. Had it been at all possible, he +would have taken me by the hand and led me to the box as a helper. After +a few seconds, he returned to the pole, pried the lid of the box with +it, then gnawed at the pole. For about five minutes he worked fairly +rapidly and steadily, using the poles, pulling, gnawing, and walking +about. + +His next move was to go to the opposite end of the box, look in, take +the piece of banana which was near the opening, then pick up the second +pole, which had not previously been noticed, and after a number of +attempts, push it into and through the box, looking after it and then +pulling it out and looking into the box. Having done this he again came +to my end of the cage, and from there returned to try once more with the +pole which he had first used. He pushed this pole all the way through, +then walked to the other end of the box, looked in and reaching in, +obtained the banana which had been pushed far enough along to be within +his grasp. Figures 29, 30 and 31 of plate V show stages of this process. + +Julius had worked twenty-four minutes with relatively little lost time +before succeeding. He had shown almost from the start the idea of using +the pole as an instrument, and his sole difficulty was in making the +pole serve the desired purpose. + +The experiment was rendered still more crucial on May 5 by the placing +of the two poles upright in opposite corners of the large cage. For a +few minutes after he entered the cage, Julius did not see them, and his +time was spent pulling and gnawing at the box. Then he discovered one of +the poles, seized it, and pushed it into the box. He tried four times, +then went and got the other pole and pushed it into the opposite end of +the box. Twice he did this, then he returned to the original pole, +bringing the second one with him. He pushed it in beside the first, and +as it happened, shoved the banana out of the opposite end of the box. +But he did not see this, and only after several seconds when he happened +to walk to that end of the box did he discover the banana. The total +time until success was fifteen minutes. + +Subsequently the ape became very expert in using the pole to obtain the +banana, and often only a minute or two sufficed for success. It was not +possible for him to direct the stick very accurately, for when he was in +such a position that he could look through the box, he could not work +the stick itself. It was, therefore, always a matter of chance whether +he obtained the banana immediately or only after a number of trials. + +Although it is possible that the use of the poles in this experiment was +due to observation of human activities, it seems probable in the light +of what we know of the natural behavior of the anthropoid apes that +Julius would have solved this problem independently of human influence. +It was the expectation of the experimenter that the pole would be used +to push the banana through the box, but as a matter of fact the ape used +it, first of all, to pull the food toward him, thus indicating a natural +tendency which is important in connection with the statements just made. +Subsequently he learned that the banana must be pushed through and +obtained at the farther end of the box. I am not prepared to accept the +solution of this problem as satisfactory evidence of ideation, but I do +know that few observers could have watched the behavior of the orang +utan without being convinced that he was acting ideationally. + + +_Draw-in Experiment_ + +An interesting contrast with the box and pole test is furnished by what +may be called the draw-in experiment. This was planned as a simple test +of Julius's ability to use a stick to draw things into his cage from +beyond the wire side. A board was placed, as is shown in figure 34 of +plate VI, with sides to hold a banana, carrot, or some other bit of +food, in position. In the actual test either a carrot or a banana was +placed about two feet from the wire netting and a stick two feet long +was then put into the cage with the ape. + +When this situation was first presented to Julius, he looked at the +banana, reached for it, and failing, picked up a bag from the floor of +the cage and tried to push it through the wire mesh toward the banana. +He also used a bit of wire in the same way, but was unable thus to get +the food. As soon as a stick was placed in his cage, he grasped it and +used it in a very definite, although unskillful, way to pull the banana +toward him. He was extremely eager and impatient, but nevertheless +persistent in his efforts, and within five minutes from the beginning of +the first trial, he had succeeded in getting two pieces of banana, using +always his left hand to manipulate the stick. This test was repeated a +number of times with similar results. He had from the first the ability +to use a stick in this way, and the only difficulty with the test as a +means of obtaining evidence of ideational behavior is that the +possibility of imitation of man cannot be certainly excluded. + + +_Lock and Key Test_ + +By my assistant it was reported on May 5 that the orang utan had been +seen to place a splinter of wood in a padlock which was used on the +cages and to work with it persistently. It looked very much like +imitation of the human act of using the key, and I therefore planned a +test to ascertain whether Julius could readily and skillfully use a key +or could learn quickly to do so by watching me. + +The first test was made on May 15 with a heavy box whose hinged lid was +held securely in position by means of a hasp and a padlock. The key, +which was not more than an inch in length, was fastened to a six inch +piece of wire so that Julius could not readily lose it. With the animal +opposite me, I placed a piece of banana in the box, then closed the lid +and snapped the padlock. I next handed Julius the key. He immediately +laid it on the floor opposite him and began biting the box, rolling it +around, and occasionally biting also at the lock and pulling at it. +During these activities he had pulled the box toward his cage. Now he +suddenly looked up to the position where the banana had been suspended +in the box experiment. Evidently the box had suggested to him the +banana. For thirty minutes he struggled with the box almost +continuously, chewing persistently at the hinges, the hasp, or the lock. +Then he took the key in his teeth and tried to push it into one of the +hinges, then into the crack beneath the lid of the box. + +Subsequently I allowed him to see me use the key repeatedly, and as a +result, he came to use it himself now and then on the edge of the box, +but he never succeeded in placing it in the lock, and the outcome of the +experiment was total failure on the part of the animal to unfasten the +lock of his own initiative or to learn to use the key by watching me do +so. I did not make any special attempt to teach him to use the key, but +merely gave him opportunity to imitate, and it is by no means impossible +that he would have succeeded had the key been larger and had the +situation required less accurately coordinated movements. However, it is +fair to say that the evidence of the idea of using the key in the lock +was unconvincing. My assistant's observation was, perhaps, misleading in +so far as it suggested that idea. It may and probably was purely by +accident that the animal used the splinter on the padlock. + + +2. Skirrl, _Pithecus irus_ + + +_Box Stacking Experiment_ + +The monkey Skirrl was tested by means of the box stacking experiment +much as Julius had been. On August 23, with a carrot suspended six feet +from the floor of the large cage and three boxes in distant corners, the +animal was admitted and his behavior noted. + +The boxes, which were made of light, thin material, ranged in size from +one six inches in its several dimensions to one twenty inches long, +thirteen inches wide, and eleven inches deep. Only by using at least two +of these boxes was it possible for the animal to reach the carrot. + +Immediately on admission to the cage, Skirrl began to gnaw at the boxes, +trying with all his might to tear them to pieces. After some thirty +minutes of such effort, interrupted by wanderings about the cage and +attempts to get at the other monkeys, he suddenly went to the largest +box of all, set it up on end almost directly under the carrot, mounted +it, and looked up at the food. It was still beyond his reach and he made +no effort to get it, but instead, he reached from his perch on the big +box for the next smaller box, which was approximately sixteen inches, by +fourteen, by twelve. This he succeeded in pulling toward him, at the +same time raising it slightly from the floor, but his efforts caused the +large box to topple over and he quit work. The experiment was +discontinued after a few minutes, the total period of observation having +been thirty-five minutes. + +Skirrl handled the boxes with ease and with evident pleasure and +interest. He also noticed the carrot at various times during the +interval, but his attention was fixed on it only for short periods. + +The test was continued on August 24 when, instead of a carrot, a half +banana was used as bait. It was placed only five feet from the floor, +and three boxes were as formerly placed in distant corners of the cage. +When admitted, Skirrl looked at the banana, then pulled one of the boxes +toward it, but instead of mounting, he went to the smallest box and +began to gnaw it. Shortly, he mounted the middle sized box and looked up +toward the banana, but the box was not directly under the bait, and in +any event, it would have been impossible for him to reach it. He next +went to the largest box, gnawed it vigorously, turned it over several +times, and then abandoned it for the middle sized box, from which by +skillful use of his teeth and hands, he quickly tore off one side. + +By this time, apparently without very definitely directed effort on the +part of the monkey, all three of the boxes were in the center of the +cage and almost directly beneath the banana. Skirrl climbed up on the +largest box and made efforts to pull the middle sized one up on to it, +the while looking at the banana every few seconds. He did not succeed in +getting the boxes properly placed, and after a time began moving them +about restlessly. + +His behavior plainly indicated that hunger was not his chief motive. He +was more interested in playing with things or in working with them than +in eating, and the satisfaction of tearing a box to pieces seemed even +greater than that of food. It is especially noteworthy that when Skirrl +attempts to dismember a box, instead of starting at random, he searches +carefully for a favorable starting point, a place where a board is +slightly loosened or where a slight crack or hole enables him to insert +his hand or use his teeth effectively. Many times during this experiment +he was observed to examine the boxes on all sides in search of some weak +point. If no such weak point were found, he shortly left the box; but if +he did find a favorable spot, he usually succeeded, before he gave up +the attempt, in doing considerable damage to the box. + +Following the behavior described above, Skirrl returned to the middle +sized box, placed it on end under the banana, mounted, and looked upward +at the bait, but as it was a few inches beyond his reach, he made no +attempt to get it, but instead, after a few seconds, went to the +smallest box, and finding a weak point, began to tear it to pieces. + +Later he rolled what was left of the smallest box close to the other two +boxes, nearly under the banana, and the remainder of his time was spent +gnawing at the boxes and playing with pieces which he had succeeded in +tearing from them. During the remainder of the thirty minute interval of +observation, no further attention was given the bait. + +Again, on August 25, the test was tried, but this time with boxes whose +edges had been bound with tin so that it was impossible for the monkey +to destroy them. He spent several minutes searching for a starting point +on the middle sized box, but finding none, he dragged it under the +banana, looked up, mounted the box, but, as previously, did not reach +for the bait because it was beyond his reach. He then played with the +boxes for several minutes. Finally he worked the two smaller boxes to a +position directly under the banana, put the middle sized one on end, +mounted it, and looked at the bait, but again abandoned the attempt +without reaching. + +During the thirty minutes of observation he made no definite effort to +place one box upon another. Three times he mounted one or another of the +boxes when it was under the banana or nearly so, but in no case was it +possible for him to reach the bait. + +From the above description of this monkey's behavior, it seems fairly +certain that with sufficient opportunity, under strong hunger, he would +ultimately succeed in obtaining the bait by the use of two or more +boxes. For his somewhat abortive and never long continued efforts to +drag two boxes together or to place the one upon the other clearly +enough indicate a tendency which would ultimately yield success. The +possibility of imitation is not excluded, for Skirrl had opportunities +to see Julius and the experimenter handle the boxes. + +Because of the other work which seemed more important at the time, this +experiment was not continued further. The results obtained suggest the +desirability of testing thoroughly the ability of monkeys to use objects +as only the anthropoid apes and man have heretofore been thought capable +of using them. + + +_Box and Pole Experiment_ + +Skirrl was first tested with the box and pole experiment on August 12. +As in the case of Julius, a half banana was placed in the middle of the +long box and the attention of the monkey was attracted to the bait by +small pieces of carrot placed near each open end. Two poles were placed +near the box on the floor of the cage. When admitted to the cage Skirrl +went almost directly to the ends of the box, took the pieces of carrot +which were in sight, but apparently failed to perceive the bait in the +middle of the box. For a while he played with the locks on the box, +shoved it about, and amused himself with it, showing no interest in +obtaining the food. Later he looked through the box and saw the banana. +He then dragged the box about, apparently trying to get it into his +cage, but he gave no attention to the poles nor did he make any evident +effort to obtain the banana which was easily visible in the center of +the box. The period of observation was only twelve minutes. + +On August 24 this experiment was repeated with an important modification +of the apparatus in that the wooden lid of the long box had been +replaced by a wire cover through which the animal could see the bait. +Two poles were as formerly on the floor of the cage, not far from the +box. Skirrl almost immediately noticed the banana and tried to get it by +gnawing at the box. He did not once reach in at the ends of the box, but +he did handle the poles, throwing them about and pounding with them. +There was not the slightest attempt to use them in obtaining the bait. + +This experiment was later repeated three times at intervals of a number +of days, but in no case did Skirrl show any tendency to use the poles as +means of obtaining the food. + + +_Draw-in Experiment_ + +This also was arranged in the same manner as for Julius, and on each of +five days Skirrl was allowed at least thirty minutes to work for the +bait. Either a banana or a carrot was each day placed on the board well +beyond his reach, and one or two, usually two, small sticks were put +into his cage. Not once during the several periods of observation did +Skirrl make any attempt to use a stick or any other object as a means of +drawing the food to him. Instead, he reached persistently with his arm, +pulled and gnawed at the wires which were in his way, and occasionally +picked up and gnawed or pounded with the sticks in the cage. His +attention every now and then would come back to the food, but it tended +to fluctuate rather rapidly, and in the regular period of observation, +thirty minutes, it is unlikely that he attended to the bait itself for +as much as five minutes. In this respect as well as many others, +Skirrl's behavior contrasts sharply with that of the orang utan. + +The results of this experiment indicate the lack in the monkey of any +tendency or ability, apart from training, to use objects as means of +obtaining food. Ways of using objects as tools which apparently are +perfectly natural to the anthropoid apes and to man are rarely employed +by the lower primates. + + +_Hammer and Nail Test_ + +One day I happened to observe Skirrl playing with a staple in his cage. +He had found it on the floor where it had fallen and was intently +prodding himself with the sharp points, apparently enjoying the unusual +sensations which he got from sticking the staple into the skin in +various portions of his body, and especially into the prepuce. + +A few days later I saw him playing in similar fashion with a nail which +he had found, and still later he was seen to be using a stick to pound +the nail with. This suggested to me the hammer and nail test. + +A heavy spike was driven into an old hammer to serve as an +indestructible handle. This hammer, along with a number of large wire +nails and a piece of redwood board, was then placed in the monkey's +cage. Skirrl immediately took up the hammer, grasping the middle of the +handle with his left hand, and with his right hand taking up a nail. He +then sat down on the board, examined the nail, placed the pointed end on +the board, and with well directed strokes by the use of the head of the +hammer drove the nail into the board for the distance of at least an +inch. He then tried to pull it out, but was forced to knock it several +times with the hammer before he could do so. + +This performance, during the next few minutes, was repeated several +times with variations. Often the side of the hammer was used instead of +the head, and occasionally, as is shown in figure 8 of plate II, he +seized the hammer well up toward the juncture of the same with the +spike. This figure does justice to the performance. At the moment the +picture was taken, Skirrl's attention had been attracted by a monkey in +an adjoining cage, and he had momentarily looked up from his task, the +while holding nail and hammer perfectly still. + +This test was repeated on various days, and almost uniformly Skirrl +showed intense interest in hammer and nails and used them more or less +persistently in the manner described. Occasionally, apparently for the +sake of variety, he would put the blunt end of the nail on the board and +hammer on the point. Again, he would try persistently to drive the nail +into the cement floor, and once by accident, when hammer and nails were +left in his cage over night, he succeeded in making several holes in the +bottom of his sheet iron water pan. There was no doubting the keen +satisfaction which the animal took in this form of activity. + +It is impossible to say that the behavior was not imitative of man, for +Skirrl, along with all of the other monkeys, had had abundant +opportunity to see carpenters working. But this much can be said against +the idea of imitation,--no one of the other animals, not excepting the +orang utan, showed any interest whatever in hammer and nails. +Occasionally they would be played with momentarily or pushed about, but +Sobke, Jimmie, Gertie, Julius, although given several opportunities to +exhibit any ability which they might have to drive nails, made not the +least attempt to do so. Evidently we must either conclude that Skirrl +had a peculiarly strong imitative tendency in this direction, or +instead, a pronounced disposition or instinct for the use of objects as +tools. It would seem fair to speak of it as an instinct for mechanical +activity. + +Under this same heading may be described Skirrl's reactions to such +objects as a handsaw, a padlock, and a water faucet. The saw was given +to him in order to test his ability to use it in human fashion, for if +he could so expertly imitate the carpenter driving nails, it seems +likely that he might also imitate the use of the saw. + +As a matter of fact, he showed no tendency to use the saw as we do. +Instead, he persistently played with it in various ways, at first using +it as a sort of plane to scrape with, later often rubbing the teeth over +a board so that they cut fairly well, but never as effectively as in the +hands of a man. After two or three days' practice with the saw, Skirrl +hit upon a method which is, as I understand, used by man in certain +countries, namely, that of placing the saw with the teeth up, holding it +rigid, and then rubbing the object which is to be sawed over it. This +Skirrl succeeded in doing very skillfully, for he would sit down on the +floor of the cage, grip with both feet the handle of the saw, with the +teeth directed upward, then holding either end in his hands, he would +repeatedly rub a stick over the teeth. In this way, of course, he could +make the saw cut fairly well. But still more to his liking was the use +of a spike instead of a stick as an object to rub over the teeth, for +with this he was able to make a noise that would have satisfied even a +small boy. + +Further light is shed on the force of the tendency to imitate man by the +saw test. After Skirrl had been given an opportunity to show what he +could do with the tool spontaneously, I demonstrated to him the approved +human way of sawing. Often he would watch my performance intently as +though fascinated by the sound and motion, but when given the tool he +invariably followed his own methods. Although I repeated this test of +imitation several times on three different days, the results were wholly +negative. + + +_Other Activities_ + +One day as Skirrl was being returned to his own cage by way of the +larger cage, he picked up an unfastened padlock and carried it into the +cage with him. For more than an hour he amused himself almost without +interruption by playing with this lock. The things which he did with it +during that time would require pages to describe. His interest in it was +very similar to that which he had exhibited in hammer and nails, saw, +and indeed any objects which he could play with. The lock was pounded in +various ways, bitten, poked with nails, hooked into the wires of the +cage, used to pull on, pounded with a stick, used to hammer on the floor +of the cage with, and in fine, manipulated in quite as great a variety +of ways as a human being could have discovered. Finally it was hooked to +the side of the cage and snapped shut, and as Skirrl was unable to +dislodge it from this position, he shortly gave up playing with it. + +At the end of the large cage and just outside the wire netting was a +faucet to which a hose was usually attached. The valve could be opened +by turning a wheel-shaped hand piece. Both Skirrl and Julius learned to +turn this wheel in order to get water to play with, but usually the +former's strength was not sufficient to turn on the water. The latter +could do it readily. The indications are that both animals profited by +seeing human beings turn on the water. This unquestionably attracted +their attention to the faucet, and probably by playing with it they +accidentally happened upon the proper movement. At any rate, Skirrl's +behavior was significant in this connection, for he would pick up the +hose to see if water were flowing, and if it were not, he would throw it +down, go directly to the faucet, and try to turn the wheel. The +association of the wheel with the desired flow of water was therefore +definitely established. Shall we describe the act as ideational? It +seems the natural thing to do. + + +3. Sobke, _Pithecus rhesus_ + + +_Box Stacking Experiment_ + +For this test, in the case of Sobke, three light boxes made of redwood +about one-third of an inch thick were used. The smallest, box 1, was six +inches in each direction, the next larger, box 2, was twelve inches, and +the third, box 3, eighteen inches. As in the case of the other animals, +bait, either banana or carrot, was suspended from the middle of the roof +of the large cage at such distance from the floor as to be reached by +the animal only by the use of the boxes. + +The first observations on Sobke were made on June 14. The three boxes +had been placed in the form of a pyramid directly under the banana, +which hung about eighteen inches above the uppermost box. Sobke's +attention while in his cage had been attracted to the bait by seeing me +fastening it in position, but when admitted to the large cage, he simply +glanced at it and then wandered about the cage, picking up bits of food +and struggling to get at the other monkeys. This he did for about five +minutes. He then went to the boxes, placed his hands on top of the +bottom one, but did not climb up on it. A few minutes later he returned +to the box again, climbed up, and readily reached the food, which he ate +while resting on boxes 1 and 2. + +I now replaced the bait and gave the monkey a second chance to obtain +it. Almost immediately he climbed up as far as the second box, but +although he could reach the banana only from the uppermost box, he +deliberately shoved it off to the ground and sat down upon box 2. As he +was unable to obtain the banana from this, he soon began to gnaw and +pull at it, and as he was succeeding all too well in his efforts to tear +the box to pieces, he had to be returned to his cage. + +The most important features of his behavior were, first, his stealthy +and indirect manner, and second, his failure to use other means of +obtaining the bait than that supplied by the observer. Instead of +looking straight at the experimenter, or at the object which he wished +to obtain, he apparently looked and attended elsewhere. For this reason +it was often difficult to decide whether or not he had noticed the bait +or the boxes. Finally I was led to conclude that he usually knew exactly +what was going on and had in his furtive way noted all of the essential +features of the situation, and that his manner was extremely indicative +of his mental attitude of limited trust. Both Julius and Skirrl went to +the opposite extreme in the matter of directness, or as we should say in +human relations, frankness. They would look the experimenter directly in +the eye, and they usually gazed intently at anything, such for example +as the bait, that interested them. Sobke, even when very hungry, instead +of going directly toward the bait, and trying to obtain it, usually did +various other things as though pretending that he had no interest in +food. + +On the following day, June 15, the three boxes were again placed nearly +under the banana, but this time the two smaller boxes, numbers 1 and 2, +were pushed to the extreme end of the lower box and so far from the bait +that it could not be reached from box 1. It was necessary then for the +animal to push boxes 1 and 2 along on box 3 until they were nearer the +bait. + +Sobke, when admitted to the cage, evidently noticed the banana, but as +formerly, he made no immediate effort to obtain it. After wandering in +search of food and quarreling with the other monkeys for several +minutes, he went to the boxes, pushed the topmost one, number 1, off on +to the floor, and then carried it into his cage where he quickly tore +one side off. He next returned to the large cage, climbed up on box 2, +and he was able, by jumping, to reach and obtain the banana. + +As Sobke was very good at jumping, his new method rendered the box +stacking experiment of uncertain value, since it was next to impossible +so to arrange the spatial relations of bait and boxes that he should be +neither discouraged by too great a distance nor encouraged to jump by +too small a distance. Evidently it would be more satisfactory to +simplify the conditions by trying to discover, first of all, whether he +would use a single box as a means of reaching the reward. + +In pursuance of this idea, I suspended a piece of bread five feet from +the floor of the cage, and a few feet to one side of it, I placed a box +from which it could be reached, or at least easily seized by jumping. +Sobke shortly walked to a point beneath the bait and leaping into the +air, seized it. + +I then replaced the bait, raising it to a height of five feet ten inches +from the floor of the cage. When I had retired, Sobke placed himself in +the proper position beneath, looked up at it, but went away without +jumping for it. During the remaining ten minutes of observation, he paid +no further attention to the bait, having satisfied himself evidently +that it was beyond his reach. + +My use of this test was concluded on June 16 when once more I suspended +a piece of bread six feet from the floor and placed a few feet to one +side the eighteen inch box, number 3, from which had the monkey pushed +it to a point directly under the bread, he could have obtained the food +easily. Sobke noticed the food promptly, and from time to time as he +wandered about, he glanced at it out of the corner of his eye, but not +once did he sit down and look at it steadily and directly as Julius and +Skirrl might have done. + +In the first twenty minutes of observation the monkey made no attempt +either to use the box or to reach the food by jumping. I then placed the +box directly under the bait, and scarcely had I withdrawn from the cage +before Sobke climbed up on it and looked toward the food. He could not +reach it without jumping, and he made no effort to get it. I had left a +second box in the cage,--one which I had been using as a seat. Sobke now +went to this box, placed his hands on it, looked toward the bait, and +then went to a distant part of the cage. No further indications were +obtained during the remainder of the period of observation of interest +in the boxes as possible means of obtaining the desired food. + +It is of course obvious that this experiment was not long enough +continued to justify the conclusion that either Sobke or Skirrl could +not use the boxes or even learn to place one box upon another in order +to obtain the bait. The experiment, like several others which are being +described briefly, was used to supplement the multiple-choice +experiment, and the experimenter's chief interest was to discover the +number and variety of methods which would be used by the animal in +the first few presentations of a situation. It is practically certain +that both of these monkeys would have succeeded ultimately in solving +the problem of obtaining the food had they been left in the cage with a +number of boxes, for Skirrl very early indicated interest in moving the +boxes about, and Sobke showed a tendency in that direction which perhaps +was inhibited partially by his distrust of the experimenter. + + +_Draw-in Experiment_ + +For Sobke, as for Julius and Skirrl, the draw-in test was made by +putting food on a shelf outside the cage, beyond the reach of the +animal, and placing in the cage with the animal one or two sticks long +enough to be used for drawing in the bait. + +Sobke was first given this test on July 24. He tried persistently to +reach the banana with his hand, seized the box which supported the bait, +shook it, picked up one or other of the sticks, and chewed at it +repeatedly, but not once did he make any move to use a stick to draw the +food toward him. + +This experiment was repeated on July 27, 29, 30 and 31, a period of +thirty minutes being allowed on each day for observation. At no time did +Sobke show any inclination to use either a stick or any other object as +a means of reaching the bait. Instead, he confined himself strictly to +the use of hands and teeth. + +This test makes it fairly certain that Sobke had no natural tendency to +use objects as tools. In so far as he attended to things about the cage +or laboratory, it seemed to be rather to play with them in a general way +than to use them ideationally or otherwise for definite purposes. + +The definitely negative result of the draw-in experiment rendered +needless prolonged observation with the box and pole test, whose results +are now to be presented. + + +_Box and Pole Experiment_ + +The eighty-four inch box, previously used for a similar test with +Julius, was presented to Sobke on August 24, the wooden cover having +been replaced by a wire one so that the monkey could readily see the +bait in the middle of the box. Sobke, when admitted to the large cage, +went directly to the box and at once discovered the banana which was +midway between the ends. He evidently desired it. Shortly, he went to +one end of the box and looked in. This he repeated later. He also shook +the box and tried to pull it about and tear it with his teeth, but to +the two poles lying nearby on the floor of the cage he gave not the +slightest attention during a thirty minute period of observation. + +The experiment was not repeated because of more important work. + + +_Other Activities_ + +In more respects than I have taken time to enumerate in the above +descriptions of behavior, the relations of Sobke to objects differed +from those of Skirrl, and still more from those of Julius. Hammer, +nails, saw, stones, sticks, locks, and various other objects received +relatively little attention from Sobke unless they happened to come in +his way; then they were usually pushed aside with but scant notice. +Rarely he would carry something to the shelf of his cage with him, but +as a rule only to lay it down and attend to something else. Skirrl, on +the contrary, attended persistently to anything new in the shape of a +movable object. He was extremely partial to objects which could be +manipulated by him in various ways, and especially to any thing with +which he could make a noise. His interest in hammer and nails, saw, +locks, etc., seemed never to wane. I have seen him play for an hour +almost uninterruptedly with a hammer and a nail, or even with a big +spike which he could use to pry about his cage. In the absence of +anything more interesting, even a staple or a small nail might receive +his undivided attention for minutes at a time. How important is the +species difference in this connection, I have no means to judge, but if +we may not consider these different modes of behavior characteristic of +_P. rhesus_ as contrasted with _P. irus_, we must conclude that +remarkable individual differences exist among monkeys, for whereas +Skirrl is by nature a mechanical genius, Sobke has apparently no such +disposition. I can imagine no more fascinating task than the careful +analytical study of the temperaments of these two animals. Skirrl's +behavior has importantly modified my conception of genius. + + + +V + +MISCELLANEOUS OBSERVATIONS + + +1. _Right- and left-handedness_ + +Several years ago Doctor Hamilton reported to me observations which he +had made on preference for the right or left paw in dogs. He has not, I +believe, published an account of his work. Subsequently, Franz observed +a similar preference in monkeys which, according to his report, exhibit +marked tendency to be right-handed, left-handed, or ambidextrous. + +My own observations, although they are wholly incidental to my other +work, seem worthy of description at this point. I noted, first of all, +that the orang utan Julius tended to use his left hand. He by no means +limited himself to this, but in difficult situations he almost +invariably reached for food or manipulated objects in connection with +food getting with the left hand. Figures 23 and 24 of plate V, show him +reaching for a banana with the left hand. Likewise, figure 34 exhibits +the use of the left hand in the draw-in experiment. + +So marked was Julius's preference for his left hand that I became +interested in observing similar phenomena in the monkeys. Skirrl, when +driving nails, held the hammer with his left hand and the nail with his +right hand. The fact that he never was observed to reverse the use of +the hands is surprising, for other observations indicate that he +preferred the right hand for certain acts. + +Stimulated by the obvious left-handedness, in certain connections, of +Julius and Skirrl, I tested the preference of several of the monkeys in +the following simple way. Standing outside the cage I would hold out a +peanut to a hungry animal, keeping it so far from the cage that the +monkey could barely reach it with its fingers. I noted the hand which +was used to grasp the food. Next I varied the procedure by placing the +peanut on a board in order to make sure that I was not definitely +directing the animal's attention. + +With Sobke the following results were obtained. In forty trials given on +two different days, he reached for and obtained the food each time with +his left hand. Only by holding the bait well toward the right side of +his body was it possible to induce him to use the right hand. So far as +may be judged from these observations and from others in connection with +the experiments, this animal is definitely left-handed. + +With Skirrl the results are strikingly different. As stated above, he +used the hammer consistently with his left hand, but in twenty attempts +to obtain food by reaching, he used his right hand seventeen times and +his left only three times. It was quite as difficult to induce him to +use his left hand for this purpose as it was to induce Sobke to use his +right. We must therefore conclude that Skirrl is right-handed in +connection with certain movements and left-handed in others. + +The monkey named Gertie in the reaching experiment consistently used her +left hand, never once using the right. + +Jimmie, so far as it was possible to make tests with him, also used his +left hand, but it should be said that the results are unsatisfactory +because he was at the time extremely pugnacious and paid attention to +the experimenter rather than to the food. + +Scotty, in the first series of ten trials, used his right hand eight +times, his left twice. In the second series, given the following day, he +used the right hand three times and the left seven times. From this we +should have to infer that he is ambidextrous. + +A female _rhesus_ monkey which had been brought to the laboratory only a +few days previously showed a preference for the right hand by the use of +it fourteen times to six. + +In connection with these data which are, I should repeat, too scanty to +be of any considerable value, I wish to describe my own experience. +Although naturally left-handed, I am by training right-handed to the +extent of having been able to use my hands in writing and in various +other activities equally well at the age of twelve. I am at present +ambidextrous in that there are many things which I do with equal +readiness and skill with either hand. Delicate, exact, and finely +coordinated movements, such as those of writing and using surgical +instruments, I perform always with my left hand while grosser movements +involving the whole hand or arm, I am rather likely to perform with my +right hand. + +It seems not improbable in the light of my own experience that we shall +find some specialization among the lower animals with respect to +preference for right and left hand or arm. I should not be at all +surprised to discover that it is the rule for animals to possess or to +develop readily definite preference for one hand in connection with a +given act of skill and to have quite as definite a preference for the +other hand in connection with a radically different kind of act. + + +2. _Instinct and emotion_ + +Of the many presumably instinctive modes of behavior which were +observed, only those which have to do with social relations seem +especially worth reporting. From among them I shall select for +description a few which have already been referred to in connection with +the experimental observations. + + +_Maternal Instinct_ + +Aspects of the maternal instinct I had opportunity to observe in Gertie, +who on February 27 gave birth to a male infant, I present below the +substance of a previously published note on her behavior (Yerkes, 1915). + +"On February 27 one of the monkeys of our collection gave birth, in the +cages at Montecito, to a male infant. The mother is a _Macacus +cynomolgus rhesus_ (_P. irus rhesus_) who has been described by Hamilton +(1914, p. 298) as 'Monkey 9, Gertie, _M. cynomolgus rhesus_ (_P. irus +rhesus_). Age, 3 years 2 months. (She is now, May 1, 1915, 4 years and 6 +months.) Daughter of monkeys 3 and 10. First pregnancy began September, +1913.' The result of this pregnancy was, I am informed, a still-birth. + +"The second pregnancy, which shall now especially concern us, resulted +likewise in a still-birth. Parturition occurred Saturday night, and the +writer first observed the behavior of the mother the following Monday +morning. In the meantime the laboratory attendant had obtained the data +upon which I base the above statements. + +"At the time of parturition Gertie was in a 6 by 6 by 12 foot out-door +cage containing a small shelter box, with an exceptionally quiet and +gentle male (not the father of the infant) who is designated in +Hamilton's paper as Monkey 28, Scotty. + +"My notes record the following exceptionally interesting and genetically +important behavior. On March 1, when I approached her cage, Gertie was +sitting on the floor with the infant held in one hand while she fingered +its eyelids and eyes with the other. Scotty sat close beside her +watching intently. When disturbed by me the mother carried her infant to +a shelf at the top of the cage. Repeatedly attempts were made to remove +the dead baby, but they were futile because Gertie either held it in her +hands or sat close beside it ready to seize it at the slightest +disturbance. + +"Especially noteworthy on this, the second day after the birth of the +infant, are the male's, as well as the female's, keen interest in the +body and their frequent examinations of the eyes, as if in attempts to +open them. Often, also, the mother searched the body for fleas. + +"Observations were made from day to day, and each day opportunity was +sought to remove the body without seriously frightening or exciting the +female. No such opportunity came, and during the second week the corpse +so far decomposed that, with constant handling and licking by the +adults, it rapidly wore away. By the third week there remained only the +shriveled skin covering a few fragments of bone, and the open skull from +the cavity of which the brain had been removed. This the mother never +lost sight of: even when eating she either held it in one hand or foot, +or laid it beside her within easy reach. + +"Gradually this remnant became still further reduced until on March 31 +there existed only a strip of dry skin about four inches long with a +tail-like appendage of nearly the same length. + +"The male, Scotty, on this date was removed to another cage. Gertie made +a great fuss, jumping about excitedly and uttering plaintive cries when +she discovered that her mate was gone. Whenever I approached her cage +she scurried into the shelter box and stayed there while I was near. +This behavior I never before had observed. It continued for two days. On +April 2, it was noted that she had lost her recently acquired shyness +and she no longer made any attempts to avoid me. As usual, on this date, +she was carrying the remnant about with her. + +"The following day, April 3, Gertie was lured from her cage to a large +adjoining compartment for certain experimental observations. After she +had been returned to her own cage the remnant was noticed on the floor +of the large cage. I picked it up. Gertie evidently noticed my act; for +although at a distance of at least ten feet from me, she made a sharp +outcry and sprang to the side of the cage nearest me. I held the piece +of skin (it looked more like a bit of rat skin than the remains of a +monkey) out to her and she immediately seized it and rushed with it to +the shelf at the top of the cage. + +"Two days later the remnant was missing, and careful search failed to +discover it in the cage. It is probable that Gertie had carelessly left +it lying on the floor whence it was washed out when the cages were +cleaned. On this date Gertie seemed quieter than for weeks previously. + +"Thus it appears that during a period of five weeks the instinct to +protect her offspring impelled this monkey to carry its gradually +vanishing remains about with her and to watch over them so assiduously +that it was utterly impossible to take them from her except by force. + +"After reading this note in manuscript, Doctor Hamilton informed me that +Gertie had behaved toward her first still-birth as toward her second. +And, further, that Grace, a baboon, also carried a still-birth about for +weeks. + +"I am now heartily glad that my early efforts to remove the corpse were +futile, for this record of the persistence of maternal behavior seems to +me of very unusual interest to the genetic psychologist." + + +_Fear_ + +In connection with the multiple-choice experiments Skirrl exhibited what +seemed to be instinctive fear as a result of his unfortunate experience +with nails in the floor of box 1. He seemingly referred his misadventure +to some unseen enemy under the floor, and this in spite of the fact that +he was given abundant opportunity to examine the floor of the box, but +not until after the dangerous nails had been clinched. His long +continued avoidance of the experiment boxes and his still more +persistent hesitancy in entering them, coupled with his almost ludicrous +efforts to see beneath the floor through the holes cut for the staples +on the doors, gave me the impression of superstitious fear of the +unseen. As I watched and recorded his behavior day after day during the +period of most pronounced fear, I could not avoid the thought that the +instinctive fear of snakes had something to do with his peculiar +actions, and although I have never studied either the natural or the +acquired responses of monkeys to snakes, I suspect that lacking such +instinctive equipment, Skirrl would have behaved differently as a result +of the pricks which he received from the nails. It is needless to +redescribe his acquired fear of whiteness as it manifested itself in the +freshly painted apparatus. Accompanying these instructive modes of +response and their emotions are suggestions of peculiarly interesting +problems as well as of modes of attacking them. As a matter of fact, +Skirrl's fear-reactions did much to alter my conception of the +constitution of his mind. I should not have been surprised by the +features of behavior exhibited, but I was by no means prepared for their +persistence, and for the highly emotional attitude toward the particular +situation. Only an organism of complexly constituted nervous system and +fairly highly developed affective life could be expected to respond as +did this monkey. As has been suggested above, I find the appeal to +instinct, modified by experience, a natural mode of accounting for the +unexpected features of Skirrl's behavior. + + +_Sympathy_ + +The instinctive playfulness of the young monkey Tiny contrasted most +strikingly with the more serious, if not more sedate, modes of behavior +of the older individuals. + +During the greater part of my period of observation Tiny was cage-mate +of Scotty, the most calm and apparently lazy of all the monkeys. Tiny +delighted in teasing Scotty, and her varied modes of mildly tormenting +him and of stirring him to pursuit or to retaliation were as interesting +as they were amusing. Her most common trick was to steal up behind him +and pull the hair of his back, or seize his tail with her hands or +teeth. Often when he was asleep she would suddenly run to him, give a +sudden jerk at a handful of hairs, and leap away. He was surprisingly +patient, and I never saw him treat her roughly in retaliation. + +Another of Tiny's favorite forms of amusement was that of trying to stir +up the other monkeys to attacks on one another. She very cleverly did +this by pretending that she herself was being attacked. The instant the +older animals began to show hostility toward one another she would leap +out of the way and watch the disturbance with evident satisfaction. It +was this mode of behavior in the little animal which ultimately provided +opportunity for the observations which I wish now to report as +indicative of sympathetic, possibly I may say altruistic, emotions. + +Tiny was confined with Scotty in a cage adjoining the one in which +Jimmie and Gertie were being kept. The cages were separated by wire +netting of half-inch mesh. + +One morning as I was watching the behavior of the animals in the several +cages, I noticed Tiny dressing with her teeth a wounded finger. It had +evidently been bitten by one of the other animals, in all probability +either by Jimmie or Gertie. Tiny was trimming away the loose bits of +skin very neatly and cleansing the wound. After working at this task for +a few minutes, she quickly climbed up to the shelf near the top of her +cage, and by rushing to the partition wire between the two cages, she +lured Gertie to an attempted attack on her. Gertie sprang up to the +partition, placed her hands on it, with the fingers projecting through +the meshes, and attempted to seize Tiny's fingers with her teeth. But +the latter was too quick for her, and withdrawing her hands, like a +flash seized in her teeth the middle finger of Gertie's left hand. She +then bit it severely and with all her might, at the same time pulling +and twisting violently, often placing the entire weight of her body on +the finger. Her sharp teeth cut to the bone, and it was impossible for +the larger and stronger monkey to tear away. For several seconds this +continued, then Gertie succeeded in escaping, whereupon she at once +retreated to the opposite end of her shelf and proceeded to attend to +her injured finger. She cried, wrung her hands, and from time to time +placed the finger in her mouth as though in an effort to relieve the +pain. By this time Jimmie's attention had been attracted by the +disturbance and he rushed up to the shelf, and facing Gertie, watched +her intently for a few seconds. The look of puzzled concern on his face +was most amusing. Apparently he felt dimly that something in which he +should have intelligent interest was going on, but was unable wholly to +understand the situation. After watching Gertie for a time and trying to +discover what she was doing, which was rendered difficult by her +tendency to turn away from him, in order to shield her injured finger, +he rushed over to the wire partition and made strenuous efforts to seize +Tiny with his hands and teeth. But although she continued close to the +partition and often crowded against it with face and hands flattened on +the wires, he was not able to get hold of her, and after a few vain +attempts he returned to his mate, and again with evident solicitousness +and the most troubled expression, watched her wringing her hands and +chewing or sucking at her injured finger. Shortly he again returned to +the partition and renewed his attempts to seize the young monkey. Thus +he went back and forth from one place of interest to the other several +times, but being unable to achieve anything at either point, he finally +gave up and returned to his breakfast on the floor of the cage. + +I report this incident fully because the behavior of Jimmie was in +marked contrast with the usual behavior of the monkeys. Selfishness +seemed everywhere dominant, while clear indications of sympathetic +emotions were rare indeed. The above is undoubtedly the best evidence of +anything altruistic that I obtained. + +It is possible that Tiny's action was retaliatory, but although it is +practically certain that either Gertie or Jimmie inflicted the wound on +her finger, I of course cannot be sure that the spirit of revenge +stirred her to punish Gertie so severely. Jimmie's part in the whole +affair is, however, perfectly intelligible from our human point of view, +and there seems no reason to doubt that he did experience something like +a feeling of sympathy with his mate, coupled with a feeling of +resentment or anger against Tiny. + + + +VI + +HISTORICAL AND CRITICAL DISCUSSION OF IDEATIONAL BEHAVIOR IN MONKEYS AND +APES + + +It is my purpose in this section to indicate the relations of my work on +monkeys and apes to that of other investigators. Although throughout the +report I have used freely the psychological terms idea and ideation, it +has been my aim to describe the behavior of my animals rather than to +interpret it or speculate concerning its accompaniments. Certain acts I +have designated as ideational simply because they seemed to exhibit the +essential features of what we call ideational behavior in man. Further +study may, and probably will, modify my opinion concerning this matter. +It is of prime importance to analyze ideational behavior so that it may +be accurately described and satisfactorily defined in terms of its +distinguishing characteristics. I had hoped to be able to present a +tentative analysis in this report, but the results of my efforts are so +unsatisfactory that I do not feel justified in publishing them. + +The terms idea and ideation have been used to designate contents of +consciousness which are primarily representative. Nowhere have I +attempted to indicate different types or grades of ideational behavior +and nowhere have I found it necessary to emphasize differences between +image and idea. In general, the acts which I have called ideational have +been highly adaptive, and the learning processes in connection with +which they have appeared have differed strikingly from those of the +selective sort in their abruptness of appearance. + +Extremely interesting and valuable definitions of ideation and +discussions of the characteristics of different sorts of ideas in the +light of original observations on monkeys have been presented by +Thorndike (1901, pp. 1, 2; 1911, p. 174); Kinnaman (1902, p. 200); and +Hobhouse (1915, p. 270). As these authors have contributed importantly +to our knowledge of the behavior of monkeys, their discussions of the +meaning of terms are especially valuable. Serviceable definitions are to +be found, also, in Romanes (1900), Morgan (1906), Washburn (1908), and +Holmes (1911). + + +_Evidences of Ideation in Monkeys_ + +Aside from anecdotal and traveller's notes on the behavior of monkeys +and apes we have only a scanty literature. In fact, the really excellent +articles on the behavior and mental life of these animals may be counted +on one's fingers; and not more than half of these are experimental +studies. I shall, in this brief historical sketch, neglect entirely the +anecdotal literature, since my own work is primarily experimental, and +since its results should naturally be compared with those of other +experimenters. + +Thorndike (1901), the American pioneer in the application of the +experimental method to the study of mind in animals, published the first +notable paper on the psychology of monkeys. His results force the +conclusion that "free ideas" seldom appear in the monkey mind and have a +relatively small part in behavior. That the species of Cebus which he +observed exhibits various forms of ideation he is willing to admit. But +he insists that it is of surprisingly little importance in comparison +with what the general behavior of monkeys as known in captivity and as +described by the anecdotal writers have led us to expect. It is +important to note, however, that Thorndike's observations were limited +to Cebus monkeys which, as contrasted with various old world types, are +now considered of relatively low intelligence. + +In many respects the most thoroughgoing and workmanlike experimental +study of monkeys is that of Kinnaman (1902), who has reported on the +study of various forms of response in _P. rhesus_. He presents valuable +data concerning the learning processes, sensory discrimination, reaction +to number, and to tests of imitation. His results indicate a higher +level of intelligence than that discovered by Thorndike, but this is +almost certainly due to difference in the species observed. Kinnaman +goes so far as to say "We have found evidence, also, of general notions +and reasoning, both of low order" (p. 211). + +The contribution of Hobhouse (1915) to our knowledge of the mental life +of monkeys, although in a measure experimental, is based upon relatively +few and unsystematic observations as contrasted with those of Thorndike +and Kinnaman. It appears, however, that Hobhouse's experiments were +admirably planned to test the ideational capacity of his subjects, and +one can not find a more stimulating discussion of ideation than that +contained in his "Mind in Evolution." The results of his tests made with +a _P. rhesus_ monkey are similar to those of Kinnaman, for almost all of +them indicate the presence and importance of ideas. + +Watson (1908) in tests of the imitative ability of _P. rhesus_ saw +relatively little evidence of other than extremely simple forms of +ideation. But in contrast with his results, those obtained by Haggerty +(1909), in a much more extended investigation in which several species +of monkey were used, obtained more numerous and convincing evidences of +ideation in imitative behavior. Although this author wholly avoids the +use of psychological terms, seeking to limit himself to a strictly +objective presentation of results, it is clear from an unpublished +manuscript (thesis for the Doctorate of Philosophy, deposited in the +Library of Harvard University) that he would attribute to monkeys simple +forms of ideational experience. + +Witmer (1910) reports, in confirmation of Haggerty's results, +intelligently imitative behavior in _P. irus_. + +The work of Shepherd (1910) agrees closely, so far as evidences of +ideation are concerned, with that of Thorndike. He obviously strives for +conservatism in his statements concerning the adaptive intelligence of +his monkeys, all of which belonged to the species _P. rhesus_. At one +point he definitely states that they exhibit ideas of a low order, or +something which corresponds to them. Satisfactory evidences of reasoning +he failed to obtain. + +Franz's (1907, 1911) studies of monkeys, unlike those mentioned above, +have for their chief motive not the accurate description of various +features of behavior but instead knowledge of the functions of various +portions of the brain. His results, therefore, although extremely +interesting and of obvious value to the comparative psychologist, throw +no special light upon the problem of ideation. + +The investigation by Hamilton (1911) of reactive tendencies in _P. +rhesus_ and _irus_ yielded preeminently important data concerning +complex behavior. For the ingenious quadruple-choice method devised by +this observer showed that mature monkeys exhibit fairly adequate types +of response. As Hamilton's interest centered in behavior, he did not +discuss ideation, but this does not prevent the comparison of his data +with those of the present report, and the agreement of his findings with +my own is obvious. + +My work contrasts sharply with that briefly mentioned above in that I +applied systematically and over a period of several months an +experimental method suited to reveal problem solving ability. +Previously, the so-called problem or puzzle-box method had been used as +a means of testing for the presence of ideas. For this I substituted the +multiple-choice method. One of the chief advantages of this new method +is the possibility of obtaining curves of learning for the solution or +attempted solution of relational problems of varying difficultness. I am +confident that these curves of learning will prove far more valuable +than such data as are yielded by the puzzle-box method. + +The Pithecus monkeys, which I studied intensively, yielded relatively +abundant evidences of ideation, but with Thorndike I must agree that of +"free ideas" there is scanty evidence; or rather, I should prefer to +say, that although ideas seem to be in play frequently, they are rather +concrete and definitely attached than "free." Neither in my sustained +multiple-choice experiments nor from my supplementary tests did I obtain +convincing indications of reasoning. What Hobhouse has called articulate +ideas, I believe to appear infrequently in these animals. But on the +whole, I believe that the general conclusions of previous experimental +observers have done no injustice to the ideational ability of monkeys. +It is clearly important, however, that we always should take into +account the species of animal observed, for unquestionably there are +extreme differences in mental development among the monkeys. + +As I view my results in the light of their relations to earlier work, I +am strongly impressed with the importance of the use of improved methods +for the study of complex behavior. The delayed reaction method of +Hunter, the quadruple-choice method of Hamilton, and my multiple-choice +method offer new and promising approaches to forms of activity which +thus far have been only superficially observed. + +The ability exhibited by Skirrl to try a method out and then to abandon +it suddenly is characteristic of animals high in intelligence. Most of +the problems which I presented to my animals would be rated as difficult +by psychologists, for as a rule they involved definite relations and +demanded on the part of the subject both perception of a particular +relation and the ability to remember or re-present it on occasion. + +I was greatly surprised by the slow progress of the monkeys toward the +solution of these problems. It had been my supposition that they would +solve them more quickly than any lower type of mammal, but as a matter +of fact they succeeded less well than did pigs. Their behavior +throughout the work proved that of far greater significance for the +experimenter than the solution of a problem is definite knowledge of the +modes of behavior exhibited from moment to moment, or day to day. This +is true especially of those incidental or accidental modes of response +which so frequently appeared in connection with my work that I came to +look upon them, the surprises of each day, as my chief means of insight. + + +_Evidences of Ideation in Apes_ + +Reliable literature of any sort concerning the behavior and mental life +of the anthropoid apes is difficult to find, and still more rare are +reports concerning experimental studies of these animals. There are, it +is true, a few articles descriptive of tests of mental ability, but even +these are scarcely deserving of being classed as satisfactory +experimental studies of the psychology of the ape. I have the +satisfaction of being able to present in the present report the first +systematic experimental study of any feature of the behavior of an +anthropoid ape. + +Among the most interesting and valuable of the descriptions which may be +classed among accounts of tests of mental ability is Hobhouse's (1915) +study of the chimpanzee. The subject was an untrained animal, so far as +stated, of somewhat unsatisfactory condition because of timidity. +Nevertheless, Hobhouse was able to obtain from him numerous and +interesting responses to novel situations, some of which may be safely +accepted as evidences of ideation of a fairly high order. + +Similar in method and result to the work of Hobhouse is that of Haggerty +(unpublished thesis for the Doctorate of Philosophy, deposited in the +Library of Harvard University). Haggerty's tests of the ability of young +orang utans and chimpanzees to solve simple problems and to use tools in +various ways yielded results which contrast most strikingly with those +obtained in his experimental study of the imitative tendency in monkeys. +His observations, had he committed himself to anything approaching +interpretation, doubtless would have led him to conclusions concerning +the ideational life of these animals very similar to those of Hobhouse. + +Koehler, working in the Canary Islands, has, according to information +which I have received from him by letter, made certain experiments with +orang utans and chimpanzees similar to those of Hobhouse and Haggerty. +His results I am unable to report as I have scanty information +concerning them. They are, presumably, as yet unpublished. + +In his laboratory at Montecito, California, Hamilton has from time to +time kept anthropoid apes, but without special effort to investigate +their ideational behavior. He has most interesting and valuable data +concerning certain habits and instincts, all as yet unpublished. + +To a congress of psychologists Pfungst (1912) briefly reported on work +with anthropoid apes in certain of the German zoölogical gardens. His +preliminary paper does not enable one to make definite statements +concerning either his methods or such results as he may have obtained +concerning ideational behavior. So far as I know, he has not as yet +published further concerning his investigation. + +Möbius (1867) has described interesting observations concerning the +mental life of the chimpanzee. But this, like all of the work previously +mentioned, is rather in the nature of casual testing than thoroughgoing, +systematic, and analytic study. + +In addition to the above reports, there are a few concerning the +behavior of apes which have been especially trained for purposes of +exhibition. Most interesting of these is that of Witmer (1909), who +studied in exhibitions and in his own laboratory the behavior of the +chimpanzee Peter. The varied forms of intelligently adaptive behavior +exhibited by this ape convinced Witmer of ideational experience and even +of an approach to reasoning. In his brief report he expresses especial +interest in the possibility of educating this "genius among apes" to the +use of language. + +A chimpanzee named Consul was observed several years ago by Hirschlaff +(1905), and his tricks were interestingly described from the pedagogical +standpoint. + +Similar in character is Shepherd's (1915) brief description of the stage +behavior of Peter and Consul, both chimpanzees. It is impossible to +determine from the account whether these animals are the same as were +observed by both Witmer and Hirschlaff. As no reference is made in +Shepherd's paper to other descriptions of the behavior of these animals +and as he adds nothing to what had already been presented, the reader +obtains no additional light on ideation. + +I have mentioned only samples of the articles on trained anthropoids. +All are necessarily descriptions of the behavior of individuals who had +been trained not for psychological purposes but for the vaudeville +stage, and although such observations unquestionably have certain value +for comparative psychology, it is well known that unless an observer +knows the history of an act, he is not able to evaluate it in terms of +intelligence and is especially prone to overestimate its value as +evidence of ideation. + +There remain studies of the apes, dealing primarily with behavior and +mental characteristics, which are slightly if at all experimental and +deserve to be ranked as naturalistic accounts. Such is, for example, the +book of Sokolowski (1908), in which attention is given to the +characteristics of young as well as fairly mature specimens of the +gorilla, chimpanzee and orang utan. + +The various publications of Garner (1892, 1896, 1900) deal especially +with the language habits of monkeys and apes, but observations bearing +on ideation are reported. + +Wallace (1869) describes certain features of the behavior of an infant +orang utan whose mother he shot in Borneo. He also reports observations +concerning the behavior of adult orang utans, many specimens of which +were shot by him during his travels. + +Early in the last century, Cuvier (1810) interested himself in studies +of the intellectual characteristics of the orang utan, and his data, +taken with those of Wallace, Sokolowski, and others similarly interested +in the natural history of mind, give one a valuable glimpse of the life +of the anthropoid ape. + +Finally, the data brought together by Brehm (1864, 1875, 1888) in his +famous Tierleben; by Darwin (1859, 1871) in "The Origin of Species," and +other works, by Romanes (1900), especially in his books on mental +evolution, by C. Lloyd Morgan (1906) in his several works on comparative +psychology, and by Holmes (1911) in his discussion of the evolution of +intelligence, contribute not unimportantly to our all too meagre +knowledge of the mental life of the anthropoid apes. + +My own results, viewed in the light of what one may learn from the +literature, stand out as unique because of the method of research. Never +before, so far as I have been able to learn, has any ape been subjected +to observation under systematically controlled conditions for so long a +period as six months. Moreover, my multiple-choice method has the merit +of having yielded the first curve of learning for an anthropoid ape. +This fact is especially interesting when one considers the nature of the +particular curve. For so far as one may say by comparing it with the +curves for various learning processes exhibited by other mammals, it is +indicative of ideation of a high order, and possibly of reasoning. I do +not wish to exaggerate the importance of my results, for as contrasted +with what might be obtained by further study, and with what must be +obtained if we are adequately to describe the mind of the orang utan, +they are meager indeed. + +Especially noteworthy, as evidences of ideation, in the results yielded +by the multiple-choice method are (1) the use by the orang utan of +several different methods in connection with each problem; (2) the +suddenness of transition from method to method; (3) the final and +perfect solution of problem I without diminution of the initial errors; +(4) the dissociation of the act of turning in a circle from that of +standing in front of a particular box. + +To these features of behavior others of minor importance might be added. +But as they have been sufficiently emphasized in the foregoing detailed +descriptions, I need only repeat my conclusion, from the summation of +evidence, that this young orang utan exhibited numerous free ideas and +simple thought processes in connection with the multiple-choice +experiment. His ultimate failure to solve the second problem is +peculiarly interesting, although in the light of other features of his +behavior by no means indicative of inferior intelligence. + +The various supplementary experimental tests which I employed are in no +wise importantly distinguished from those used by other observers. The +box stacking experiment has, according to my private information, been +used by Koehler. It is obviously important that such tests be applied in +the same manner to individuals not only of the different genera of +anthropoid apes, but of different ages, sex, and condition of training. + +The box stacking experiment, although it yielded complete success only +as a result of suggestion on my part, proved far more interesting during +its progress than any other portion of my work. In connection with it, +the orang utan exhibited surprisingly diverse and numerous efforts to +meet the demands of the situation. It is fair to characterize him as +inventive, for of the several possible ways of obtaining the banana +which were evident to the experimenter, the ape voluntarily used all but +two or three, and one of these he subsequently used on the basis of +imitation. + +Had Julius been physically and mentally mature, my results would +undoubtedly have been much more impressively indicative of ideas, but +even as matters stand, the survey of my experimental records and +supplementary notes force me to conclude that as contrasted with the +monkeys and other mammals, the orang utan is capable of expressing free +ideas in considerable number and of using them in ways highly indicative +of thought processes, possibly even of the rational order. But +contrasted with that of man the ideational life of the orang utan seems +poverty stricken. Certainly in this respect Julius was not above the +level of the normal three-year-old child. + +In common with other observers, I have had the experience of being +profoundly impressed by the versatility of the ape, and however much I +might desire to disprove the presence of free ideas and simple reasoning +processes in the orang utan, I should feel bound to accept many of the +results of my tests as evidences of such experience. + +I have attempted to indicate briefly the historical setting of my +investigation. I propose, now, in the concluding section, to look +forward from this initial research and to indicate as well as I may in a +few words the possibilities of results important for mankind from the +thorough study of the monkeys and anthropoid apes. + + + +VII + +PROVISION FOR THE STUDY OF THE PRIMATES, AND ESPECIALLY THE MONKEYS AND +ANTHROPOID APES[1] + +[Footnote 1: Much of the material of this section was published +originally in _Science_ (Yerkes, 1916).] + + +I should neglect an important duty as well as waste an opportunity if in +this report I did not call attention to the status of our knowledge +concerning the monkeys and apes and present the urgent need of adequate +provision for the comparative study of all of the primates. + +Although for centuries students of nature have been keenly interested in +the various primates, the information which has been accumulated is +fragmentary and wholly inadequate for generally recognized scientific +and practical needs. There is a voluminous literature on many aspects of +the organization and lives of the monkeys and apes, but when one +searches in it for reasonably connected and complete descriptions of the +organisms from any biological angle, one, is certain to meet +disappointment. + +Concerning their external characteristics we know much; and our +classifications, if not satisfactory to all, are at least eminently +useful. But when one turns to the morphological sciences of anatomy, +histology, embryology, and pathology, one discovers great gaps, where +knowledge might reasonably be expected. Even gross anatomy has much to +gain from the careful, systematic examination of these organisms. With +still greater force this statement applies to the studies of finer +structural relations. Little is known concerning the embryological +development and life history of certain of the primates, and almost +nothing concerning their pathological anatomy. + +Clearly less satisfactory than our knowledge of structure is the status +of information concerning those functional processes which are the +special concern of physiology and pathology. Certain important +experimental studies have been made on the nervous system, but rarely +indeed have physiologists dealt systematically with the functions of +other systems of organs. There are almost no satisfactory physiological +descriptions of the monkeys, anthropoid apes, or lower primates. + + + +SUB-DIVISIONS OF THE ORDER PRIMATES + +_Order_ _Sub-orders_ _Families_ + + ,- a. PROSIMII (Lemurs and Aye-Ayes) + | + | ,- i. Hapalidae (Marmosets) + | | ii. Cebidae (Howling Monkeys, +PRIMATES -+ | Tee Tees, Squirrel Monkeys, + | | Spider Monkeys, and Capuchin + | | Monkeys) + `- b. ANTHROPOIDEA ... -+ iii. Cercopithecidae (Baboons + | and Macaques) + | iv. Simiidae (Gibbons, Orangs, + | Chimpanzees, and Gorillas) + `- v. Hominidae (Man) + + + + +When we turn to the science of genetics we meet a similar condition, for +the literature reveals only scattered bits of information concerning +heredity in the primates. No important experimental studies along +genetic lines have been made with them, and such general observations +from nature as are on record are of extremely uncertain value. Were one +to insist that we know nothing certainly concerning the relation of +heredity in other primates than man, the statement could not well be +disputed. + +Occasionally in recent years students of human diseases have employed +monkeys or apes for experimental tests, but aside from the isolated +results thus obtained, extremely little is known concerning the diseases +peculiar to the various types of infra-human primates or the significant +relations of their diseases to those of man. + +Next in order of extent to our morphological knowledge of these +organisms is that of their behavior, mental life, and social relations. +But certainly no one who is conversant with the behavioristic, +psychological and sociological literature could do otherwise than +emphasize its incompleteness and inadequacy. For our knowledge of +behavior has come mostly from naturalistic observation, scarcely at all +from experimentation; our knowledge of social relations is obviously +meager and of uncertain value; and finally, our knowledge of mind is +barely more than a collection of carelessly drawn inferences. + +This picture of the status of scientific work on the primates, although +not overdrawn, will doubtless surprise many readers, and even the +biologist may find himself wondering why we are so ignorant concerning +the lives of the organisms most nearly akin to us, and naturally of +deepest interest to us. The reasons are not far to seek. Most scientific +investigators are forced by circumstances to work with organisms which +are readily obtained and easily kept. The primates have neither of these +advantages, for many, if not most of them, are expensive to get and +either difficult or expensive to keep in good condition. Clearly, then, +our ignorance is due not to lack of appreciation of the scientific value +of primate research but instead to its difficultness and costliness. + +Strangely enough, the practical importance of knowledge of the primates +has seldom been dwelt upon even by those biologists who are especially +interested in it. It is, therefore, appropriate to emphasize the +strictly human value of the work for which I am seeking provision. + +During the past few years it has been abundantly and convincingly +demonstrated that knowledge of other organisms may aid directly in the +solution of many of the problems of experimental medicine, of +physiology, genetics, psychology, sociology, and economics. In the light +of these results, it is obviously desirable that all studies of +infrahuman organisms, but especially those of the various primates, +should be made to contribute to the solution of our human problems. + +To me it seems that thoroughgoing knowledge of the lives of the +infrahuman primates would inevitably make for human betterment. Through +the science of genetics, as advanced by experimental studies of the +monkeys and anthropoid apes, practical eugenic procedures should be more +safely based and our ability to predict organic phenomena greatly +increased. Similarly, intensive knowledge of the diseases of the other +primates in their relations to human diseases should contribute +importantly to human welfare. And finally, our careful studies of the +fundamental instincts, forms of habit formation, and social relations in +the monkeys and apes should lead to radical improvements in our +educational methods as well as in other forms of social service. + +Along theoretical lines, no less than practical, systematic research +with the primates should rapidly justify itself, for upon its results +must rest the most significant historical or genetic biological +descriptions. It is beyond doubt that genetic psychology can best be +advanced to-day by such work, and what is obviously true of this science +is not less true of all the biological sciences which take account of +the developmental or genetic relations of their events. + +In view of the probable values of increasingly complete accounts of +primate life, it seems far from extravagant to insist that the securing +of adequate provision for systematic and long continued research is the +most important task for our generation of biologists and the one which +we shall be least excusable for neglecting. Indeed, when one stops to +reflect concerning the situation, it seems almost incredible that the +task has not been accomplished. + +Some ten years ago Professor John B. Watson (1906) entered a plea for +the founding of a station for the experimental study of behavior. He +made no special mention of work with the monkeys and apes, but it is +clear from the problems which he enumerates that he would consider them +most important subjects for observation. Professor Watson's plea has +apparently been forgotten by American biologists, and it seems not +inappropriate to revive it at this time. For surely we have advanced +sufficiently along material and scientific lines during the last ten +years to render possible the realization of his hope. + +To my knowledge, only one definite attempt has thus far been made to +gain special provision for the study of the primates. Somewhere about +the year 1912 there was established on Tenerife, one of the Canary +Islands, a modest station for the study of the anthropoid apes. I have +already referred to it briefly on page 1. The plan and purpose of this +station, which is of German origin, have been presented briefly by +Rothmann (1912). From personal communications I know that a single +investigator has been in residence at the station since its founding and +that psychological and physiological results of value have been +obtained, but no published reports have come to my attention. + +When I first heard of the existence of the German anthropoid station I +naturally thought of the possibility of coöperative work, but the events +of the past two years have rendered the chances of cooperation so remote +that it now seems wholly desirable and indeed imperative to seek the +establishment of an American station, which, unlike the German station, +shall provide adequately not only for the study of the anthropoid apes +but for that of all of the lower primates. It should be the function of +such a station or research institute (1) to bring together and correlate +all the information at present available; (2) to fill in existing gaps +observationally and thus complete and perfect our knowledge of these +organisms; (3) to seek to bring all available information to bear upon +the problems of human life. + +Hitherto the unsatisfactoriness of progress has been due to the lack of +a definite plan and program. Every investigator has gone his own way, +doing what little his personal means and opportunity rendered possible. +The time has at last come when concerted action seems feasible as well +as eminently desirable. I am therefore offering a plan and program +which, if wisely developed, should lead ultimately to fairly complete +and practically invaluable knowledge of the lives of all of the +primates. There should be provided in a suitable locality a station or +research institute which should offer adequate facilities (1) for the +maintenance of various types of primate in normal, healthy condition; +(2) for the successful breeding and rearing of the animals, generation +after generation; (3) for systematic and continuous observation under +reasonably natural conditions; (4) for experimental investigations from +every significant biological point of view; (5) for profitable +cooperation with existing biological institutes or departments of +research throughout the world. + +The station should be located in a region whose climate is highly +favorable to the life of many of the lower primates as well as to that +of man. Such a location is by no means easy to find. Because of my +intense interest in the subject, I have, during the past five years, +prospected in various parts of the world for a satisfactory site. I +shall now attempt to indicate the chief requirements and also the +foremost advantages and disadvantages of several regions which have been +considered. It is first of all requisite that the climate be such as to +agree with the organisms to be studied and such, also, as to render +their breeding normal and dependable. Second in importance is its +satisfactoriness for the life and scientific productiveness of the +observer. While certain tropical localities would meet the first +requirement perfectly, they would prove extremely unsatisfactory for +research activity. It therefore seems essential to find a region whose +climate shall reasonably meet the needs of the experimenter while +adequately meeting those of the animals to be studied. + +A further factor which has important bearing upon the productiveness of +the observer is the degree of isolation from civilization and from other +scientific work. No scientist can long work effectively, even in a +reasonably healthy and stimulating climate, if entirely cut off from +similar interests and activities. It is therefore desirable, if at all +possible, to discover a location in the midst of civilization and with +reasonably good opportunities for scientific associations. + +With these several desiderata before us, I shall call attention to a +number of possible sites for a station, several of which I have visited. +Southern California, and especially the portion of the State between +Santa Barbara and San Diego, promises fairly well. It is definitely +known that certain, if not all, species of monkey will breed there +fairly satisfactorily, and although it has not yet been demonstrated, +there is no reason to suppose that in certain regions the anthropoid +apes might not also be kept in perfect health and successfully bred. The +main advantages of this general region are (a) a climate which promises +to be reasonably satisfactory for many if not all of the primates; (b) +admirable climatic conditions for investigators; (c) wholly satisfactory +scientific and cultural environment for the staff of a station. The most +significant disadvantages are (a) a temperature, which is at times a +trifle too low for the comfort of certain of the monkeys and apes. It is +by no means certain, however, that they would not usually adapt +themselves to it. (b) The necessity of importing all of the animals and +of having to rely upon successful acclimatization. Of course it is to be +assumed that importation would be necessary only at the outset of such +work, since the animals later should replenish themselves within the +confines of the station. + +Florida offers possibilities somewhat similar to those of southern +California, but as I have not had opportunity to examine the conditions +myself, I can say only that in view of such information as is available +the advantage seems to be greatly in favor of the latter. + +Cuba, Jamaica, Porto Rico, and for that matter, several of the West +Indies, offer possible sites for a successful station. I have reasonably +intimate personal knowledge only of the conditions in Jamaica. The major +advantages in the West Indies are (a) suitable climatic conditions and +food supply for the animals; and (b) reasonably satisfactory climatic +conditions for the staff. These are, however, more than counterbalanced +in my opinion by the following serious disadvantages: (a) the relative +isolation of the investigators from their fellow scientists; (b) the +necessity of importing all of the animals originally used; (c) the risk +of destruction of the station by storms. + +It is definitely known that anthropoid apes as well as monkeys can be +successfully kept, bred, and reared in the West Indies. During the past +year, on the estate of Doha Rosalia Abreu, near Havana, Cuba, a +chimpanzee was born in captivity. A valuable account of this important +event and of the young ape has been published by Doctor Louis Montané +(1915). It therefore seems practically certain that regions could be +found readily on Jamaica, Porto Rico, or smaller islands, which would be +eminently satisfactory for the breeding of apes. + +There are obvious reasons why an American station for the study of the +primates should be located on territory controlled by the United States +Government, and if a tropical location proves necessary, it would +probably be difficult to find more satisfactory regions, aside from the +inconveniences and risk of importation and the relative isolation of the +investigators, than are available on Porto Rico. + +I have not seriously considered the possibility of locating an American +station on the continent of Africa, for although two of the most +interesting and important of the anthropoid apes, the gorilla and the +chimpanzee, are African forms, while many species of monkey are either +found there or could readily be imported, it has seemed to me that the +islands of the West and East Indies and the portions of the United +States referred to above are much to be preferred over anything +available in Africa. + +In the East, Borneo, the Philippine Islands, and Hawaii are well worth +considering. Borneo is the home of the gibbon and of at least one +species of orang utan, and in addition to these important assets, it +presents the advantages of (a) a wholly suitable climate and food supply +for monkeys and apes; and (b) climatic conditions for investigators +which, I am informed by scientific friends, are nearly ideal. For +investigators the most serious disadvantage here, as in all other parts +of the East, would be the isolation from other scientific work and +workers. + +The possibilities of Central America I considered several years ago when +it seemed to me possible that work might profitably be done with monkeys +and apes on the Canal Zone. The advantages are (a) a climate which +promises fairly well for the animals; and (b) reasonable accessibility +from the United States. The disadvantages are (a) a far from ideal +climate for long continued scientific work; and (b) an environment which +from the cultural and scientific point of view leaves much to be +desired. + +Were a permanent psycho-biological station for the study of the primates +to be established in southern California, it would, even though wholly +satisfactory conditions for the breeding, rearing, and studying of the +animals were maintained, furnish more or less inadequate opportunity for +the observation of the animals under free, natural conditions. It would +therefore be necessary, to supplement the work of such a station by +field work in Borneo, Sumatra, Africa, India, South America, and such +other regions as the species of organism under consideration happen to +inhabit. + +Considering equally the needs of the experimenter and the demands of the +animals, it seems to me reasonable to conclude that southern California +should be definitely proved unsuitable before a more distant site were +selected. For the information which I have been able to accumulate +convinces me that it would in all probability be possible successfully +to breed and keep the primates there, and it is perfectly clear that in +such event the output of a station would be enormously greater because +of the more favorable conditions for research than in any tropical +region or in a more isolated location. + +Assuming that satisfactory provision in the shape of a scientific +establishment for the study of the primates in their relations to man +were available, the following program might be followed: (1) Systematic +and continuous studies of important forms of individual behavior, of +social relations, and of mind; (2) experimental studies of physiological +processes, normal and pathological, and especially of the diseases of +the lower primates, in their relations to those of man; (3) studies of +heredity, embryology, and life history; (4) research in comparative +anatomy, including gross anatomy, histology, neurology, and pathological +anatomy. + +Each of these several kinds of research should be in progress almost +continuously in order that no materials or opportunities for observation +be needlessly wasted. Because of the nature of the work, it would be +necessary to provide, first of all, for those functional studies which +demand healthy and normally active organisms, whose life history is +intimately and completely known. This is true of all studies in +behavior, whether physiological, psychological, or sociological. +Simultaneously with behavioristic observations and often upon the same +individuals, genetic experiments might be conducted. This would be +extremely desirable because of the relatively long periods between +generations. After the usefulness of an animal in behavioristic or +genetic inquiries had been exhausted, it might be made to render still +further service to science in various experimental physiological, or +medical inquiries. And finally, the same individual might ultimately be +used for various forms of anatomical research. Thus, it is clear that +the scientific usefulness of a lemur, a monkey, or an ape might be +maintained at a high level throughout and even beyond the period of its +life history. + +The program thus briefly sketched would provide either directly or +indirectly for work on every aspect of primate life. Especially +important would be the intimacy of interest and cooperation among +investigators, for the comparative method should be applied consistently +and to the limit of its value. The results of various kinds of +observation should be correlated so that there should ultimately emerge +a unitary and practically valuable account of primate life, to replace +the patchwork of information which we now possess. + +Because of the costliness of maintaining and breeding the monkeys and +apes, it is especially desirable that the several kinds of research +mentioned above should be conducted. Indeed, it would seem inexcusably +wasteful to attempt to maintain a primate or anthropoid station for +psychological observations alone, or for any other narrowly limited +biological inquiry. + +Furthermore, the station should be permanent, since for many kinds of +work it would be essential to have intimate knowledge of the life +history and descent of an individual. With the lower primates, a +generation might be obtained in from two to five years; with the higher, +not more frequently, probably, than from ten to fifteen years. It +therefore seems not improbable that the value of the work done in such a +station would continue to increase for many years and would not reach +its maximum short of fifty or even one hundred years. + +A staff of several highly trained and experienced biologists would be +needed. The following organization is suggested as desirable, although, +as indicated below, not necessarily essential in the beginning: (1) An +expert especially interested in the problems of behavior, psychology, +and sociology, with keen appreciation of practical as well as of +theoretical problems; (2) an assistant trained especially in comparative +physiology; (3) an expert in genetics and experimental zoology; (4) an +assistant with training and interests in comparative anatomy, histology, +and embryology; (5) an expert in experimental medicine, who could +conduct and direct studies of the diseases of man as well as of the +lower primates and of measures for their control; (6) an assistant +trained especially in pathology and neurology. + +To this scientific staff of six highly trained individuals there should +be added a business manager, a clerical force of three individuals, a +skilled mechanician, a carpenter, and at least four laborers. + +The annual expenditures of an institute with such a working staff, would +in southern California, approximate fifty thousand dollars. It would +therefore be necessary that it have an endowment of approximately one +million dollars. + +In the absence of this foundation it would, of course, be possible to +make a reasonably satisfactory beginning on the work which has been +outlined in the following less expensive manner. A working plant might +be established, on ground rented or purchased at a low figure, for about +ten thousand dollars; the salary of a director, assistants, a clerical +helper, and combined mechanic and laborer might be estimated at the same +figure; the cost of animals and of maintenance of the plant would +approximate five thousand dollars. Thus, we should obtain as an estimate +of the expenditures for the first year twenty-five thousand dollars. +Without expansion, the work might be conducted during the second year +for fifteen thousand dollars, and subsequently it might be curtailed or +expanded, resources permitting, according as results achieved and in +prospect justified. + +An institute established on such a modest basis as this still might +render largely important scientific service through its own research and +through organized cooperation with other existing research +establishments. Thus, for example, supposing that behavioristic, +psychological, sociological, and genetic inquiries were conducted in the +institute itself, animals might be supplied on a mutually satisfactory +basis to institutes for experimental medicine, for physiological +research, and for anatomical studies. Under such conditions, it is +conceivable that extremely economical and good use might be made of all +the available primate materials. But it is not improbable that even +coöperative research would prove on the whole more profitable, except +possibly in the case of morphological work, if investigators could +conduct their studies in the institute itself rather than in distant +laboratories. In any event, the idea of coöperation should be prominent +in connection with the organization of a research station for the study +of the primates. For thus, evidently, scientific achievement in +connection with these important types of animal might be vastly +increased over what would be possible in a single relatively small +institution with a limited and necessarily specialized staff of workers. + +Despite the fact that biologists generally recognize the importance of +the work under consideration and are eager to have it done, it is +perfectly certain that we shall accomplish nothing unless we devote +ourselves confidently, determinedly and unitedly, with faith, vision, +and enthusiasm, to the realization of a definite plan. Our vision is +clear,--if we are to gather and place at the service of mankind adequate +comparative knowledge of the life of the primates and if we are to make +this possible harvest of scientific results count for human betterment, +we must bend all our efforts to the establishment of a station or +institute for research. + + + +VIII + +BIBLIOGRAPHY + + + +BREHM, A. Tierleben. + 1888. + +COBURN, C.A. and YERKES, R.M. A study of the behavior of the crow, + 1915. _Corvus Americanus_ Aud. by the multiple-choice method. + _Journal of Animal Behavior_, vol. 5, 75-114. + +CUVIER, FREDERIC. Description d'un orang-outang, et observations sur + 1810. ses facultées intellectuelles. _Annales du Museum d'Histoire + naturelle_, vol. 16, 46-65. + +DARWIN, C. Origin of species. + 1859. + + 1871. The descent of man, and selection in relation to sex. + +ELLIOT, D.G. A review of the primates. New York. + 1913. + +FRANZ, S.I. On the functions of the cerebrum: the frontal lobes. + 1907. _Archives of Psychology_, no. 2, 1-64. + + 1911. On the functions of the cerebrum: the occipital lobes. + _Psychological Monographs_, vol. 13, 1-118. + + 1913. Observations on the preferential use of the right and left + hands by monkeys. Journal of Animal Behavior, 3, 140-144. + +GARNER, R.L. The speech of monkeys. London. + 1892. + + 1896. Gorillas and chimpanzees. London. + + 1900. Apes and monkeys; their life and language. Boston and London. + +HAGGERTY, M.E. Imitation in monkeys. _Journal of Comparative Neurology_ + 1909. _and Psychology_, vol. 19, 337-455. + +HAMILTON, G.V. A study of trial and error reactions in mammals. + 1911. _Journal of Animal Behavior_, vol. 1, 33-66. + + 1914. A study of sexual tendencies in monkeys and baboons. _Journal_ + _of Animal Behavior_, vol. 4, 295-318. + +HIRSCHLAFF, L. Der Schimpanzee Konsul. _Zeit. f. päd. Psy_., vol. 7, 1. + 1905. + +HOBHOUSE, L.T. Mind in evolution. London. + 1915. + +HOLMES, S.J. Evolution of intelligence. New York. + 1911. + +HRDLICKA, A. Anatomical observations on a collection of orang skulls + 1907. from western Borneo; with a bibliography. _Proceedings of + the United States National Museum_, vol. 31, 539-568. + +KINNAMAN, A.J. Mental life of two _Macacus rhesus_ monkeys in captivity. + 1902. _American Journal of Psychology_, vol. 13, 98-148, 173-218. + +LASHLEY, K.S. and WATSON, J.B. Notes on the development of a young + 1913. monkey. _Journal of Animal Behavior_, vol. 3, 114-139. + +MÖBIUS, K. Zur psychologie des Schimpanse. _Zool. Garten_., vol. 8, + 1867. 279-280. + +MONTANÉ, L. Un chimpancé Cubano. Havana, _El Siglo XX_. + 1915. + +MORGAN, C.L. Introduction to comparative psychology. London. + 1906. + +PFUNGST, O. Zur Psychologie der Affen. _Ber. über d. V. Kongress f._ + 1912. _exp. Psychol_., 200-205. + +ROMANES, G.J. Mental evolution in animals. New York. + 1900. + +ROTHMANN, M. Ueber die errichtung einer Station zur psychologischen + 1912. und hirn[?] physiologischen Erforschung der Menschenaffen. + _Berliner klinische Wochenschr_., Nr. 42. + +SHEPHERD, W.T. Some mental processes of the rhesus monkey. + 1910. _Psychologic Monographs_, vol. 12, 1-61. + + 1915. Some observations on the intelligence of the chimpanzee. + _Journal of Animal Behavior_, vol. 5, 391-396. + +SOKOLOWSKY, A. Beobachtungen über die Psyche der Menschenaffen. + 1908. Frankfurt a. M. + +THORNDIKE, E.L. The mental life of the monkeys. _Psychological_ + 1901. _Monograph_, vol. 3, 1-57. + + 1911. Animal intelligence. New York. 1911. + +WALLACE, A.R. The Malay Archipelago. London. + 1869. + +WASHBURN, M.F. The animal mind. New York. + 1908. + +WATSON, J.B. The need of an experimental station for the study of + 1906. certain problems in animal behavior. _Psychological_ + _Bulletin_, vol. 3, 149-156. + + 1908. Imitation in monkeys. _Psychological Bulletin_, vol. 5, + 169-178. + + 1909. Some experiments bearing upon color vision in monkeys. + _Journal of Comparative Neurology and Psychology_, vol. 19, + 1-28. + +WITMER, L. A monkey with a mind. _Psychological Clinic_, vol. 3, 179-205. + 1909. + + 1910. Intelligent imitation and curiosity in a monkey. _Psychological_ + _Clinic_, vol. 3, 225-227. + +YERKES, R.M. The study of human behavior. _Science_, vol. 39, 625-633. + 1914. + + 1910. Maternal instinct in a monkey. _Journal of Animal Behavior_, + vol. 5, 403-405. + + 1916. Provision for the study of the monkeys and apes. _Science_, + vol. 43, 231-234. + +YERKES, R.M. and COBURN, C.A. A study of the behavior of the pig + 1915. _Sus scrofa_ by the multiple-choice method. _Journal of_ + _Animal Behavior_, vol. 5, 185-225. + + + + + +End of the Project Gutenberg EBook of The Mental Life of Monkeys and Apes +by Robert M. 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Yerkes + +Release Date: January 27, 2004 [EBook #10843] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK MENTAL LIFE OF MONKEYS *** + + + + +Produced by Michael Oltz and PG Distributed Proofreaders + + + + +The Mental Life of Monkeys and Apes: + A Study of Ideational Behavior + + + ROBERT M. YERKES + Harvard University + + + + + BEHAVIOR MONOGRAPHS + Volume 3, Number 1, 1916 + Serial Number 12 + Edited by JOHN B. WATSON + The Johns Hopkins University + + +WITH SIX PLATES AND FIVE TEXT FIGURES + + + + + + +CONTENTS + + I. Interests, opportunity and materials + + II. Observational problems and methods + + III. Results of multiple-choice experiments: + + 1. Skirrl, _Pithecus irus_ + 2. Sobke, _Pithecus rhesus_ + 3. Julius, _Pongo pygmaeus_ + + IV. Results of supplementary tests of ideational behavior: + + 1. Julius, _Pongo pygmaeus_: + Box stacking experiment + Box and pole experiment + Draw-in experiment + Lock and key test + 2. Skirrl, _Pithecus irus_: + Box stacking experiment + Box and pole experiment + Draw-in experiment + Hammer and nail test + Other activities + 3. Sobke, _Pithecus rhesus_: + Box stacking experiment + Draw-in experiment + Box and pole experiment + Other activities + + V. Miscellaneous observations: + + 1. Right- and left-handedness + 2. Instinct and emotion: + Maternal instinct + Fear + Sympathy + + VI. Historical and critical discussion of ideational behavior in + monkeys and apes: + + 1. Evidences of ideation in monkeys + 2. Evidences of ideation in apes + + VII. Provision for the study of the primates and especially the monkeys + and anthropoid apes + +VIII. Bibliography + + + +I + +INTERESTS, OPPORTUNITY AND MATERIALS + + +Two strong interests come to expression in this report: the one in the +study of the adaptive or ideational behavior of the monkeys and the +apes; and the other in adequate and permanent provision for the thorough +study of all aspects of the lives of these animals. The values of these +interests and of the tasks which they have led me to undertake are so +widely recognized by biologists that I need not pause to justify or +define them. I shall, instead, attempt to make a contribution of fact on +the score of each interest. + +While recognizing that the task of prospecting for an anthropoid or +primate station may in its outcome prove incomparably more important for +the biological and sociological sciences and for human welfare than my +experimental study of ideational behavior, I give the latter first place +in this report, reserving for the concluding section an account of the +situation regarding our knowledge of the monkeys, apes, and other +primates, and a description of a plan and program for the thorough-going +and long continued study of these organisms in a permanent station or +research institute. + +In 1915, a long desired opportunity came to me to devote myself +undividedly to tasks which I have designated above as "prospecting" for +an anthropoid station and experimenting with monkeys and apes. First of +all, the interruption of my academic duties by sabbatical leave gave me +free time. But in addition to this freedom for research, I needed +animals and equipment. These, too, happily, were most satisfactorily +provided, as I shall now describe. + +When in 1913, while already myself engaged in seeking the establishment +of an anthropoid station, I heard of the founding of such an institution +at Orotava, Tenerife, the Canary Islands, I immediately made inquiries +of the founder of the station, Doctor Max Rothmann of Berlin, concerning +his plans (Rothmann, 1912).[1] As a result of our correspondence, I was +invited to visit and make use of the facilities of the Orotava station +and to consider with its founder the possibility of coöperative work +instead of the establishing of an American station. This invitation I +gratefully accepted with the expectation of spending the greater part of +the year 1915 on the island of Tenerife. But the outbreak of the war +rendered my plan impracticable, while at the same time destroying all +reasonable ground for hope of profitable coöperation with the Germans in +the study of the anthropoids. In August, 1915, Doctor Rothmann died. +Presumably, the station still exists at Orotava in the interests of +certain psychological and physiological research. So far as I know, +there are as yet no published reports of studies made at this station. +It seems from every point of view desirable that American psychologists +should, without regard to this initial attempt of the Germans to provide +for anthropoid research, further the establishment of a well equipped +American station for the study not only of the anthropoid apes but of +all of the lower primates. + +[Footnote 1: See bibliography at end of report.] + +In the early months of the war while I was making every effort to obtain +reliable information concerning conditions in the Canary Islands, I +received an urgent invitation from my friend and former student, Doctor +G. V. Hamilton, to make use of his collection of animals and laboratory +at Montecito, California, during my leave of absence from Harvard. This +invitation I most gladly accepted, and in February, 1915, I established +myself in Santa Barbara, in convenient proximity to Doctor Hamilton's +private laboratory where for more than six months I was able to work +uninterruptedly under nearly ideal conditions. + +Doctor Hamilton without reserve placed at my disposal his entire +collection of animals, laboratory, and equipment, provided innumerable +conveniences for my work, and in addition, bore the entire expense of my +investigation. I cannot adequately thank him for his kindness nor make +satisfactory acknowledgment here of his generous aid. Thanks to his +sympathetic interest and to the courtesy of the McCormick family on +whose estate the laboratory was located, my work was done under wholly +delightful conditions, and with assistance from Ramon Jimenez and Frank +Van Den Bergh, Jr., which was invaluable. The former aided me most +intelligently in the care of the animals and the construction of +apparatus; and the latter, especially, was of very real service in +connection with many of my experiments. + +The collection of animals which Doctor Hamilton placed at my disposal +consisted of ten monkeys and one orang utan. The monkeys represented +either _Pithecus rhesus_ Audebert (_Macacus rhesus_), _Pithecus irus_ F. +Cuvier (_Macacus cynomolgos_), or the hybrid of these two species +(Elliot, 1913). There were two eunuchs, five males, and three females. +All were thoroughly acclimated, having lived in Montecito either from +birth or for several years. The orang utan was a young specimen of +_Pongo pygmaeus_ Hoppius obtained from a San Francisco dealer in +October, 1914 for my use. His age at that time, as judged by his size +and the presence of milk teeth, was not more than five years. So far as +I could discover, he was a perfectly normal, healthy, and active +individual. On June 10, 1915, his weight was thirty-four pounds, his +height thirty-two inches, and his chest girt twenty-three inches. On +August 18 of the same year, the three measurements were thirty-six and +one-half pounds, thirty-three inches, and twenty-five inches. + +For the major portion of my experimental work, only three of the eleven +animals were used. A growing male, _P. rhesus_ monkey, known as Sobke; a +mature male, _P. irus_, called Skirrl; and the young orang utan, which +had been named Julius. Plates I and II present these three subjects of +my experiments in characteristically interesting attitudes. In plate I, +figure 1, Julius appears immediately behind the laboratory seated on a +rock, against a background of live oaks. This figure gives one an +excellent idea of the immediate environment of the laboratory. Figure 2 +of the same plate is a portrait of Julius taken in the latter part of +August. By reason of the heavy growth of hair, he appeared considerably +older as well as larger at this time than when the photograph for figure +1 was taken. In plate II, figure 3, Julius is shown in the woods in the +attitude of reaching for a banana, while in figure 4 of the same plate +he is represented as walking upright in one of the cages. + +Likenesses of Sobke are presented in figures 5 and 6 of plate II. In the +latter of these figures he is shown stretching his mouth, apparently +yawning but actually preparing for an attack on another monkey behind +the wire screen. Figure 7 of this plate indicates Skirrl in an +interesting attitude of attention and with an obvious lack of +self-consciousness. The same monkey is represented again in figures 8 +and 9 of plate II, this time in the act of using hammer and saw. + + +EXPLANATION OF PLATE II + + +FIGURE 3.--Orang utan, Julius, reaching for banana. + +FIGURE 4.--Julius walking across his cage. + +FIGURE 5.--_P. rhesus_, Sobke. + +FIGURE 6.--Sobke stretching his jaws (yawn?) preparatory to a fight. + +FIGURE 7.--_P. irus_, Skirrl. + +FIGURE 8.--Skirrl using hammer and nail. + +FIGURE 9.--Skirrl using a saw. + + + +All of the animals except the orang utan had been used more or less for +experiments on behavior by Doctor Hamilton, but this prior work in no +way interfered with my own investigation. Doctor Hamilton has +accumulated a large mass of the most valuable and interesting +observations on the behavior of monkeys, and he more thoroughly +understands them than any other observer of whom I have knowledge. Much +to my regret and embarrassment in connection with the present report, he +has thus far published only a small portion of his data (Hamilton, 1911, +1914). In his most recent paper on "A study of sexual tendencies in +monkeys and baboons," he has given important information concerning +several of the monkeys which I have observed. For the convenience of +readers who may make use of both his reports and mine, I am designating +the animals by the names previously given them by Hamilton. The +available and essential information concerning the individuals is +presented below. + + + +_List of animals in collection_ + +Skirrl. _Pithecus irus_. Adult male. + +Sobke. _P. rhesus_. Young adult male. + +Gertie. _P. irus-rhesus_. Female. Born November, 1910. + +Maud. _P. rhesus_. Young adult female. + +Jimmy II. _P. irus_. Adult male. + +Scotty. _P. irus_ (?). Adult male. + +Tiny. _P. irus-rhesus_. Female. Born August, 1913. + +Chatters. _P. irus_. Adult eunuch. + +Daddy. _P. irus_. Adult eunuch. + +Mutt. _P. irus_. Young adult male. Born August, 1911. + +Julius. _Pongo pygmaeus_. Male. Age, 4 years to 5 years. + + + +When I arrived in Santa Barbara, Doctor Hamilton was about to remodel, +or rather reconstruct, his animal cages and laboratory. This gave us +opportunity to adapt both to the special needs of my experiments. The +laboratory was finally located and built in a grove of live oaks. From +the front it is well shown by figure 10 of plate III, and from the rear, +by figure 11. Its location was in every way satisfactory for my work, +and in addition, the spot proved a delightful one in which to spend +one's time. + + +[Illustration: FIGURE 12.--Ground plan of Montecito laboratory and +cages. Scale 1/120 + +L, laboratory; C, cages; A, experiment room in which multiple-choice +apparatus was installed; B, E, additional rooms for research; D, store +room and shop; Z, large central cage communicating with the eight +smaller cages 1-8.] + + +Figure 12 is a ground plan, drawn to scale, of the laboratory and the +adjoining cages, showing the relations of the several rooms of the +laboratory among themselves and to the nine cages. Although the +construction was throughout simple, everything was convenient and so +planned as to expedite my experimental work. The large room A, adjoining +the cages, was used exclusively for an experimental study of ideational +behavior by means of my recently devised multiple-choice method. +Additional, and supplementary, experiments were conducted in the large +cage Z. Room D served as a store-room and work-shop. + +The laboratory was forty feet long, twenty-two feet wide, and ten feet +to the plate. Each small cage was six, by six, by twelve feet deep, +while the large compartment into which each of the smaller cages opened +was twenty-four feet long, ten feet wide, and twelve feet deep. + + + +II + +OBSERVATIONAL PROBLEMS AND METHODS + + +My chief observational task in Montecito was the study of ideational +behavior, or of such adaptive behavior in monkeys and apes as +corresponds to the ideational behavior of man. It was my plan to +determine, so far as possible in the time at my disposal, the existence +or absence of ideas and the rôle which they play in the solution of +problems by monkeys and apes. I had in mind the behavioristic form of +the perennial questions: Do these animals think, do they reason, and if +so, what is the nature of these processes as indicated by the +characteristics of their adaptive behavior? + +My work, although obviously preliminary and incomplete, differs from +most of the previous studies of the complex behavior of the infrahuman +primates in that I relied chiefly upon a specially devised method and +applied it systematically over a period of several months. The work was +intensive and quantitative instead of more or less incidental, casual, +and qualitative as has usually been the case. Naturally, during the +course of my special study of ideational behavior observations were made +relative to various other aspects of the life of my subjects. Such, for +example, are my notes on the use of the hands, the instincts, the +emotions, and the natural aptitudes of individuals. It is, indeed, +impossible to observe any of the primates without noting most +interesting and illuminating activities. And although the major portion +of my time was spent in hard and monotonous work with my experimental +apparatus, I found time each day to get into intimate touch with the +free activities of my subjects and to observe their social relations and +varied expressions of individuality. As a result of my close +acquaintance with this band of primates, I feel more keenly than ever +before the necessity of taking into account, in connection with all +experimental analyses of behavior, the temperamental characteristics, +experience, and affective peculiarities of individuals. + +The light which I have obtained on the general problem of ideation has +come, first, through a method which I have rather inaptly named the +multiple-choice method, and second, and more incidentally, through a +variety of supplementary methods which are described in Section IV of +this report. These supplementary methods are simple tests of ideation +rather than systematic modes of research. They differ from my chief +method, among other respects, in that they have been used by various +investigators during the past ten or fifteen years. It was not my aim to +repeat precisely the observations made by others, but instead to verify +some of them, and more especially, to throw additional light on my main +problem and to further the analysis of complex behavior. + +What has been referred to as the multiple-choice method was devised by +me three years ago as a means of obtaining strictly comparable objective +data concerning the problem-solving ability of various types and +conditions of animals. The method was first tried with human subjects in +the Psychopathic Hospital, Boston, with a crude keyboard apparatus +which, however, proved wholly satisfactory as a means of demonstrating +its value. It has since been applied by means of mechanisms especially +adapted to the structure and activities of the organisms, to the study +of the behavior of the crow, pig, rat, and ringdove (Yerkes, 1914; +Coburn and Yerkes, 1915; Yerkes and Coburn, 1915). The method has also +been applied with most gratifying results to the study of the +characteristics of ideational behavior in human defectives,--children, +and adults,--and in subjects afflicted with various forms of mental +disease. It is at present being tried out as a practical test in +connection with vocational guidance and various forms of institutional +examination, such as psychopathic hospital and court examinations. + +As no adequate description of the method has yet been published to which +I can here refer, it will be necessary to present its salient +characteristics along with a description of the special form of +apparatus which was found suitable for use with monkeys and apes. + +The method is so planned as to enable the observer to present to any +type or condition of organism which he wishes to study any one or all of +a series of problems ranging from the extremely simple to the complex +and difficultly soluble. All of the problems, however, are completely +soluble by an organism of excellent ideational ability. For the human +subject, the solution of the easiest problem of all requires almost no +effort, whereas even moderately difficult problems may require many +repetitions of effort and hours or days of application to the task. In +each case, the solution of the problem depends upon the perception of a +certain constant relation among a series of objects to which the subject +is required to attend and respond. Such relations are, for example, +secondness from one end of the group, middleness, simple alternation of +ends, or progressive movement by constant steps from one end of a group +to the other. + +It is possible to present such relational problems by means of +relatively simple reaction-mechanisms. In their essential features, all +of the several types of multiple-choice apparatus designed by the writer +and used either by him or by his students and assistants are the same. +They consist of a series of precisely similar reaction-devices, any one +or all of which may be used in connection with a given observation. +These reaction-mechanisms are so chosen as to be suited to the structure +and action-system of the animal to be studied. For the human being the +mechanism consists of a simple key and the total apparatus is a bank of +keys, with such electrical connections as are necessary to enable the +observer to obtain satisfactory records of the subject's behavior. Let +us suppose the bank of keys, as was actually the case in my first form +of apparatus, to consist of twelve separate reaction-mechanisms; and let +us suppose, further, the constant relation (problem) on the basis of +which the subject is required to react to be that of middleness. It is +evident that in successive trials or experiments the keys must be +presented to the subject in odd groups, the possibilities being groups +of 3, 5, 7, 9, or 11. If for a particular observation the experimenter +wishes to present the first three keys at the left end of the keyboard, +he pushes back the remaining nine keys so that they cannot be operated +and requires the subject to select from the group of three keys the one +which on being pressed causes a signal to appear. It is of course the +clearly understood task of the subject to learn to select the correct +key in the group on first trial. This becomes possible only as the +subject observes the relation of the key which produces the desired +effect to the other keys in the group. On the completion of a subject's +reaction to the group of three keys, a group of seven keys at the +opposite end of the keyboard may, for example, be presented. Similarly, +the subject is required to discover with the minimum number of trials +the correct reaction-mechanism. Thus, time after time, the experimenter +presents a different group of keys so that the subject in no two +successive trials is making use of the same portion of the keyboard. It +is therefore impossible for him to react to spatial relations in the +ordinary sense and manner, and unless he can perceive and appropriately +respond to the particular relation which constitutes the only constant +characteristic of the correct reaction-mechanism for a particular +problem, he cannot solve the problem, or at least cannot solve it +ideationally and on the basis of a small number of observations or +trials. + +For the various infrahuman animals whose ideational behavior has been +studied by means of this method, it has been found eminently +satisfactory to use as reaction-mechanisms a series of similar boxes, +each with an entrance and an exit door. An incentive to the selection of +the right box in a particular test is supplied by food, a small quantity +of which is placed in a covered receptacle beyond the exit door of each +of the boxes. Each time an animal enters a wrong box, it is punished for +its mistake by being confined in that box for a certain period, ranging +from five seconds to as much as two minutes with various individuals or +types of organism. This discourages random, hasty, or careless choices. +When the right box is selected, the exit door is immediately raised, +thus uncovering the food, which serves as a reward. After eating the +food thus provided, the animal, according to training, returns to the +starting point and eagerly awaits an opportunity to attempt once more to +find the reward which it has learned to expect. With this form of the +apparatus, the boxes among which choice may be made are indicated by the +raising (opening) of the front door. + +Since with various birds and mammals the box form of apparatus had +proved most satisfactory, I planned the primate apparatus along similar +lines, aiming simply to adapt it to the somewhat different motor +equipment and destructive tendencies of the monkeys. I shall now briefly +describe this apparatus as it was constructed and used in the Montecito +laboratory. + + + +EXPLANATION OF PLATE IV + +FIGURE 13.--Multiple-choice apparatus, showing observer's bench + and writing stand. +FIGURE 14.--Apparatus as seen from observer's bench. +FIGURE 15.--Entrances to multiple-choice boxes as seen from + the response-compartment. +FIGURE 16.--Apparatus as seen from the rear, showing exit + doors, food receptacles, and covers for same. + + + +The apparatus was built in room A (figure 12), this room having been +especially planned for it with respect to lighting as well as dimensions +and approaches. It was unfortunately impossible to obtain photographs +showing the whole of the apparatus, but it is hoped that the four +partial views of plate IV may aid the reader who is unfamiliar with +previously described similar devices to grasp readily the chief points +of construction. In this plate, figure 13 shows the front of the +complete apparatus, with the alleyway and door by way of which the +experimenter could enter. The investigator's observation-bench and +record-table also appear in this figure, together with weighted cords +used to operate the various doors and the vertically placed levers by +means of which each pair of doors could be locked. Figure 14 is the view +presented to the observer as he stood on the bench or observation stand +of figure 13 and looked over the entire apparatus. Three of the entrance +doors are shown at the right of this figure as raised, whereas the +remainder of the nine entrance doors of the apparatus are closed. Figure +15 is a view of the entrance doors from below the wire roof of the +apparatus. Again, two of the doors are shown as raised, and three +additional ones as closed. The rear of the apparatus appears in figure +16, in which some of the exit doors are closed and others open. In the +latter case, the food receptacles appear, and on the lower part of the +raised doors of the corresponding boxes may be seen metal covers for the +food receptacles projecting at right angles to the doors, while on the +lower edge of each door is an iron staple used to receive a sliding bar +which could be operated from the observer's bench as a means of locking +the doors after they had been closed. The space beyond the exit doors +was used as an alleyway for the return of the animals to the starting +point. + +It will be necessary at various points in later descriptions to refer to +these several figures. But further description of them will be more +readily appreciated after a careful examination of the ground plan of +the apparatus presented as figure 17 In accordance with the labelling of +this figure, the experimenter enters the apparatus room through doorway +16, passes thence through doorways 17 and 10 to the large cage Z, from +which he has direct access to the animals and can bring them into the +apparatus. The multiple-choice mechanism proper, consisting of nine +similar boxes (nine were used instead of twelve as a matter of +convenience of construction, not because this smaller number is +otherwise preferable) is labelled F. These boxes are numbered 1 to 9, +beginning at the left. This numbering was adhered to in the recording of +results throughout the investigation. The other important portions of +the apparatus are the runway D, from which the subject at the +experimenter's pleasure could be admitted through doorway 12 to the +large response-chamber E; the alleyways G, H, and I, by way of which +return to the starting point was possible; the observation bench C, with +its approach step 13; and the observer's writing table A. + +In the construction of this large apparatus, it was necessary to make +provision for the extremely destructive tendencies of monkeys and +anthropoid apes,--hence the apparent cumbersomeness of certain portions. +It was equally necessary to provide for the protection of the observer +and the prevention of escape of the subjects by completely covering the +apparatus and alleyways with a heavy wire netting. + +Each of the eighteen doors of the multiple-choice boxes, and in addition +doors 11, 12, and 15 of the runway D, were operated by the observer from +his bench C by means of weighted window cords which were carried by +pulleys appropriately placed above the apparatus. Each weight was so +chosen as to be just sufficient to hold its door in position after the +experimenter had raised it. For the convenience of the experimenter in +the rapid operation of the twenty-one doors, the weights for the doors +of runway D were painted gray, those for the entrance doors, white, and +those for the exit doors, black. + +In each entrance door, as is shown in figure 15 of plate IV, a window +was cut so that the experimenter might watch the animal after it had +entered a given box, and especially note when it left the box after +having received its reward. This window was covered with wire netting. +No such windows were necessary in the exit doors, but to them were +attached heavy galvanized iron flanges which served to cover the food +receptacles. One of these flanges is labelled o in figure 17. The food +receptacles were provided by boring holes in a 2 by 4 inch timber +securely nailed to the floor immediately outside of the exit doors. Into +these holes aluminum cups fitted snugly, and the iron flanges, when the +doors were closed, fitted so closely over the cups that it was +impossible for the animals to obtain food from them. + + +[Illustration: FIGURE 17.--Ground plan of multiple-choice apparatus in +experiment room A. Scale 1/60 + +A, record stand; C, bench for observer; B, step as approach to C; D, +alleyway leading to E, response-compartment; F, one of the nine (1-9) +similar multiple-choice boxes; G, H, alleyways leading from boxes to +starting point at D; I, alleyway used by experimenter as approach to +rear of apparatus; W, W, windows; P, alleyway; Z, large cage; 16, +entrance to room A; 17, entrance to apparatus and thence via 10 to +cages; 18, entrance to alleyway 1; 11, 15, entrances to D; 12, entrance +to E; 13, entrance door of box 5; 14, exit door of box 5; o, cover for +food receptacle.] + + +As originally constructed, no provision was made in the apparatus for +locking the entrance and exit doors of the several boxes when they were +closed. But as two of the subjects after a time learned to open the +doors from either outside or inside the boxes, it became necessary to +introduce locking devices which could be operated by the experimenter +from the observation bench. This was readily accomplished by cutting +holes in the floor, which permitted an iron staple, screwed to the lower +edge of each door, to project through the floor. Through these staples +by means of a lever for each of the nine boxes, the observer was able to +slide a wooden bar, placed beneath the floor of the room, thus locking +or unlocking either the entrance door, the exit door, or both, in the +case of any one of the nine boxes. + +Since figure 17 is drawn to scale, it will be needless to give more than +a few of the dimensions of the apparatus. Each of the boxes was 42 +inches long, 18 inches wide, and 72 inches deep, inside measurements. +The alleys D, I, and H were 24 inches, and G 30 inches wide, by 6 feet +deep. The doors of the several boxes were 18 inches wide, by 5 feet +high, while those in the alleyways were 24 inches wide by 6 feet high. +The response-compartment E of figure 17 was 14 feet 4 inches, by 8 feet, +by 6 feet in depth. In order that the apparatus might be used with adult +human subjects conveniently, if such use should prove desirable, the +depth throughout was made 6 feet, and it was therefore possible for the +experimenter to walk about erect in it. + +The experimental procedure was briefly as follows: A small quantity of +food having been placed in each of the food cups and covered by the +metal flanges on the exit doors, the experimenter raised door 11 of +figure 17 and then opened door 10 and the door of the cage in which the +desired subject was confined. After the latter, in search of food, had +entered the runway D, the experimenter lowered door 11 to keep it in +this runway, and immediately proceeded to set the reaction-mechanisms +for an experiment (trial). Let us suppose that the first setting to be +tried involved all of the nine boxes. Each of the entrance doors would +therefore be raised. Let us further suppose that the right door is +defined as the middle one of the group. With the apparatus properly set, +the experimenter next raises door 12, thus admitting the animal to the +response-compartment E. Any one of the nine boxes may now be entered by +it. But if any except number 5, the middle member of the group, be +entered, the entrance door is immediately lowered and both the exit and +entrance doors locked in position so that the animal is forced to remain +in the box for a stated period, say thirty seconds. At the expiration of +this time the entrance door is raised and the animal allowed to retrace +its steps and make another choice. When the middle box is chosen, the +entrance door is lowered and the exit door immediately raised, thus +uncovering the food, which the animal eats. As a rule, by my monkeys and +ape the reward was eaten in the alleyway G instead of in the +multiple-choice box. As soon as the food has been eaten, the exit door +is lowered by the experimenter, and the animal returns by way of G and H +to runway D, where it awaits its next trial. + +As rewards, bananas and peanuts were found very satisfactory, and +although occasionally other foods were supplied in small quantities, +they were on the whole less constantly desired than the former. + +Four problems which had previously been presented to other organisms +were in precisely the same form presented to the three primates. These +problems may be described, briefly, by definition of the right reaction +mechanism, thus: problem 1, the first mechanism at the subject's left; +problem 2, the second mechanism at the subject's right (that is, from +the end of the series at the subject's right); problem 3, alternately, +the first mechanism at the subject's left and the first at its right; +problem 4, the middle mechanism of the group. + +It was my intention to present these four problems, in order, to each of +the three animals, proceeding with them as rapidly as they were solved. +But as it happened, only one of the three subjects got as far as the +fourth problem. When observations had to be discontinued, Sobke was well +along with the last, or fourth problem; Skirrl was at work at the third +problem; and Julius had failed to solve the second problem. + +For each of the problems, a series of ten different settings of the +doors was determined upon in advance. These settings differ from those +employed in a similar investigation with the pig only in that the +numbering of the doors is reversed. In the present apparatus, the boxes +as viewed from the front (entrance) are numbered from the left to the +right end, whereas those of the pig apparatus were numbered from the +right end to the left end. + +Below are presented for each of the several problems (1) the numbers of +the settings presented in series; (2) the numbers of the doors open; (3) +the number of doors open in each setting and for the series of ten +settings; and (4) the number of the right door. + + + +PROBLEM 1. First mechanism at left of group + + Doors No. of No. of +Settings open doors open right door + 1..................1.2.3......................3..................1 + 2..................8.9........................2..................8 + 3..................3.4.5.6.7..................5..................3 + 4..................7.8.9......................3..................7 + 5..................2.3.4.5.6..................5..................2 + 6..................6.7.8......................3..................6 + 7..................5.6.7......................3..................5 + 8..................4.5.6.7.8..................5..................4 + 9..................7.8.9......................3..................7 +10..................1.2.3......................3..................1 + -- + Total 35 + + +PROBLEM 2. Second mechanism from the right end of group + + Doors No. of No. of +Settings open doors open right door + 1..................7.8.9......................3..................8 + 2..................1.2.3.4....................4..................3 + 3..................2.3.4.5.6.7................6..................6 + 4..................1.2.3.4.5.6................6..................5 + 5..................4.5.6.7.8..................5..................7 + 6..................1.2.3......................3..................2 + 7..................2.3.4.5....................4..................4 + 8..................1.2.3.4.5.6.7.8.9..........9..................8 + 9..................1.2.3.4....................4..................3 +10..................3.4.5.6.7.8................6..................7 + -- + Total 50 + + +PROBLEM 3. Alternately the first mechanism at the left and the + first at the right end of the group + + Doors No. of No. of +Settings open doors open right door + 1..................5.6.7......................3..................5 + 2..................5.6.7......................3..................7 + 3..................1.2.3.4.5.6................6..................1 + 4..................1.2.3.4.5.6................6..................6 + 5..................4.5.6.7.8..................5..................4 + 6..................4.5.6.7.8..................5..................8 + 7..................2.3.4.5....................4..................2 + 8..................2.3.4.5....................4..................5 + 9..................3.4.5.6.7.8.9..............7..................3 +10..................3.4.5.6.7.8.9..............7..................9 + -- + Total 50 + + +PROBLEM 4. Middle mechanism of the group + + Doors No. of No. of +Settings open doors open right door + 1..................2.3.4......................3..................3 + 2..................5.6.7.8.9..................5..................7 + 3..................1.2.3.4.5.6.7..............7..................4 + 4..................7.8.9......................3..................8 + 5..................4.5.6.7.8..................5..................6 + 6..................1.2.3.4.5.6.7.8.9..........9..................5 + 7..................1.2.3......................3..................2 + 8..................2.3.4.5.6..................5..................4 + 9..................3.4.5.6.7.8.9..............7..................6 +10..................6.7.8......................3..................7 + -- + Total 50 + + + +It was found desirable after a problem had been solved to present a new +and radically different series of settings in order to determine to what +extent the subject had learned to choose the correct door by memorizing +each particular setting. These supplementary observations may be known +as control experiments, and the settings as supplementary settings. In +case of these, as for the original settings, the essential facts are +presented in tabular arrangement. + + + +Settings for Control Experiments + +PROBLEM 1. First at left end + + Doors No. of No. of +Settings open doors open right door + 1..................2.3.4......................3..................2 + 2..................6.7.8.9....................4..................6 + 3..................3.4.5......................3..................3 + 4..................4.5.6.7.8.9................6..................4 + 5..................6.7.8.9....................4..................6 + 6..................1.2.3.4.5..................5..................1 + 7..................2.3.4.5.6.7.8..............7..................2 + 8..................3.4.5.6.7.8................6..................3 + 9..................5.6.7......................3..................5 +10..................1.2.3.4.5.6.7.8.9..........9..................1 + + +PROBLEM 2. Second from right end + + Doors No. of No. of +Settings open doors open right door + 1..................5.6.7.8....................4..................7 + 2..................2.3.4.5.6..................5..................5 + 3..................1.2.3.4.5.6.7.8.9..........9..................8 + 4..................5.6.7......................3..................6 + 5..................1.2.3.4....................4..................3 + 6..................4.5.6......................3..................5 + 7..................2.3.4.5....................4..................4 + 8..................1.2.3......................3..................2 + 9..................1.2.3.4.5.6.7..............7..................6 +10..................2.3.4.5.6.7.8.9............8..................8 + + +PROBLEM 3. Alternate left and right ends + + Doors No. of No. of +Settings open doors open right door + 1..................5.6........................2..................5 + 2..................5.6........................2..................6 + 3..................4.5.6.7.8.9................6..................4 + 4..................4.5.6.7.8.9................6..................9 + 5..................1.2.3.4.5..................5..................1 + 6..................1.2.3.4.5..................5..................5 + 7..................2.3.4.5.6.7................6..................2 + 8..................2.3.4.5.6.7................6..................7 + 9..................3.4.5.6.7.8................6..................3 +10..................3.4.5.6.7.8................6..................8 + + +PROBLEM 4. Middle + + Doors No. of No. of +Settings open doors open right door + 1..................4.5.6.7.8..................5..................6 + 2..................1.2.3......................3..................2 + 3..................1.2.3.4.5.6.7.8.9..........9..................5 + 4..................2.3.4.5.6..................5..................4 + 5..................6.7.8......................3..................7 + 6..................3.4.5.6.7.8.9..............7..................6 + 7..................7.8.9......................3..................8 + 8..................1.2.3.4.5.6.7..............7..................4 + 9..................2.3.4......................3..................3 +10..................3.4.5.6.7..................5..................5 + + + +It was my aim so far as possible to present to a given subject each day +the ten settings under a given problem in order, without interruption. +If for any reason the series of observations had to be interrupted, it +was resumed at the same point subsequently. Occasionally it was found +desirable or necessary to present only five of the series of ten +settings in succession and then to interrupt observations for an +interval of a few minutes or even several hours. But as a rule it was +possible to present the series of ten settings. All things being +considered, it proved more satisfactory to give only ten trials a day to +each subject. Frequently twenty and rarely thirty trials were given on +the same day. In such cases the series of settings was simply repeated. +The only pause between trials was that necessary for resetting the +entrance doors and replenishing the food which served as a reward for +success. + + + +III + +RESULTS OF MULTIPLE-CHOICE EXPERIMENTS + + +1. Skirrl, _Pithecus irus_ + +_Problem 1. First at the Left End_ + + +Systematic work with the multiple-choice apparatus and method described +in the previous section was undertaken early in April with Skirrl, +Sobke, and Julius. The results for each of them are now to be presented +with such measure of detail as their importance seems to justify. + +Skirrl had previously been used by Doctor Hamilton in an experimental +study of reactive tendencies. He proved so remarkably inefficient in the +work that Doctor Hamilton was led to characterize him as feeble-minded, +and to recommend him to me for further study because of his mental +peculiarities. With me he was from the first frank, aggressive, and +inclined to be savage. It was soon possible for me to go into the large +cage, Z, with him and allow him to take food from my hand. He was +without fear of the experimental apparatus and it proved relatively easy +to accustom him to the routine of the experiment. Throughout the work he +was rather slow, inattentive, and erratic. + +Beginning on April 7, I sought to acquaint him with the multiple-choice +apparatus by allowing him to make trips through the several boxes, with +the reward of food each time. Thus, for example, with the entrance and +exit doors of box 7 raised, the monkey was allowed to pass into the +reaction-compartment E and thence through box 7 to the food cup. As soon +as he had finished eating, he was called back to D by the experimenter +and, after a few seconds, allowed, similarly, to make a trip by way of +one of the other boxes. By reason of this preliminary training he soon +came to seek eagerly for the reward of food. + +On April 10 the apparatus was painted white in order to increase the +lightness and thus render it easier for the experimenter to observe the +animal's movements, and when on April 12 Skirrl was again introduced to +it for further preliminary training, he utterly refused to enter the +boxes, giving every indication of extreme fear of the white floors and +even of the sides of the boxes. Finally, the attempts to induce him to +enter the boxes had to be given up, and he was returned to his cage +unfed. The following day I was equally unsuccessful in either driving or +tempting him with food into the apparatus. But on April 14 he was so +hungry that he was finally lured in by the use of food. He cautiously +approached the boxes and attempted to climb through on the sides instead +of walking on the floor. It was perfectly evident that he had an +instinctive or an acquired fear of the white surfaces. As the matter was +of prime importance for the success of my work, I inquired of Doctor +Hamilton, and of the men in charge of the cages, for any incident which +might account for this peculiar behavior, and I learned that some three +months earlier, while the animal cages were being whitewashed, Skirrl +had jumped at one of the laborers who was applying a brush to the +framework of one of the cages and had shaken some lime into his eyes. He +was greatly frightened and enraged. Evidently he experienced extreme +discomfort, if not acute pain, and there resulted an association with +whiteness which was quite sufficient to cause him to avoid the freshly +painted apparatus. + +Having obtained an adequate explanation of this monkey's peculiar +behavior, I proceeded with my efforts to induce him to work smoothly and +rapidly, and on April 15, by covering the floor with sawdust, I so +diminished the influence of the whiteness as to render the preliminary +training fairly satisfactory. At the end of two more days everything was +going so well that it seemed desirable to begin the regular experiment. + +On the morning of April 19, Skirrl was introduced to the apparatus and +given his first series of ten trials on problem 1. This problem demanded +the selection of the first door at the left in any group of open doors. +The procedure was as previously described in that the experimenter +raised the entrance doors of a certain group of boxes, admitted the +animal to the reaction-chamber, punished incorrect choices by confining +the animal for thirty seconds, and rewarded correct choices by raising +the exit door and thus permitting escape and the obtaining of food. The +trials were given in rapid succession, and the total time required for +this first series of ten trials was thirty-five minutes. Skirrl worked +faithfully throughout this interval and exhibited no marked +discouragement. When confined in a box he showed uneasiness and +dissatisfaction by moving about constantly, shaking the doors, and +trying to raise them in order to escape. + +For the series of settings used in connection with problem 1, the reader +is referred to page 18. In the first setting, the doors numbered 1, 2, +and 3, were opened. As it happened, the animal when admitted to the +reaction-chamber immediately chose box l. Having received the reward of +food, he was called back to D, and doors 8 and 9 having been raised in +preparation for the next trial, he was again admitted to the +reaction-chamber. This time he quickly chose box 9 and was confined +therein for thirty seconds. On being released, he chose after an +interval of four minutes, box 8, thus completing the trial. + +As it is highly important, not only in connection with the present +description of behavior, but also for subsequent comparison of the +reactions of different types of organism in this experiment, to present +the detailed records for each trial, tables have been constructed which +offer in brief space the essential data for every trial in connection +with a given problem. + +Table 1 contains the results for Skirrl in problem 1. It is constructed +as follows: the date of a series of trials appears in the first vertical +column; the numbers (and number) of the trials for the series or date +appear in column 2; the following ten columns present respectively the +results of the trials for each of the ten settings. Each number, in +these results, designates a box entered. At the extreme right of the +table are three columns which indicate, first, the number of trials in +which the right box was chosen first, column headed R; and second, the +number of trials in which at least one incorrect choice occurred, column +headed W. In the last column, the daily ratio of these first choices +appears. + +Taking the first line of table 1 below the explanatory headings, we note +on April 19 ten trials, numbered 1 to 10, were given to Skirrl. In trial +1, with setting 1, he chose correctly the first time, and the record is +therefore simply 1. In trial 2, setting 2, he incorrectly chose box 9, +the first time. At his next opportunity, he chose box 8, which was the +right one. The record therefore reads 9.8. In trial 3, setting 3, he +chose incorrectly twice before finally selecting the right box. The +record reads 6.7.3, and so on throughout the ten trials which constitute +a series. The summary for this series indicates three right and seven +wrong first choices, that is, three cases in which the right box was +entered first. The ratio of right to wrong first choices is therefore 1 +to 2.33. Since the total number of doors open in the ten settings is +thirty-five, and since in each of the ten settings one door is +describable as the right door, the probable ratio, apart from the +effects of training, of right to wrong first choices is 1 to 2.50. It is +evident, therefore, that Skirrl in his first series of trials closely +approximated expectation in the number of mistakes. + + + +TABLE 1 + +Results for Skirrl, _P. irus_, in Problem 1 + +========+==========+=========+=========+===========+=============+===========+===========+===========+=============+===========+===========+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | Ratio +Date | of | | | | | | | | | | | R | W | of + | trials | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | R to W +--------+----------+---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- + April | | | | | | | | | | | | | | + 19 | 1- 10 | 1 | 9.8 | 6.7.3 | 9.7 | 6.2 | 7.8.6 | {6.7.7.7 | 4 | 7 | 2.3.3.1 | 3 | 7 | 1:2.33 + | | | | | | | | {6.5 | | | | | | + | | | | | | | | | | | | | | + 20 | 11- 20 | 3.2.1 | 9.8 | 5.3 | 7 | 4.2 | 8.8.6 | 5 | 8.4 | 7 | 3.1 | 3 | 7 | 1:2.33 + 21 | 21- 30 | 3.1 | 8 | 3 | 8.7 | 6.2 | 6 | 5 | 6.4 | 9.7 | 1 | 5 | 5 | 1:1.00 + 22 | 31- 40 | 1 | 9.8 | 3 | 7 | 6.2 | 6 | 6.7.5 | 5.8.4 | 9.8.9.8.7 | 2.1 | 4 | 6 | 1:1.50 + 23 | 41- 50 | 2.3.1 | 8 | 5.7.3 | 7 | 4.2 | 6 | 5 | 7.8.4 | 7 | 3.1 | 5 | 5 | 1:1.00 + 24 | 51- 60 | 1 | 8 | 4.5.7.3 | 9.7 | 5.6.2 | 6 | 6.7.5 | 6.4 | 8.9.7 | 1 | 4 | 6 | 1:1.50 + 26 | 61- 70 | 1 | 8 | 6.7.4.7.3 | 7 | 4.5.6.2 | 6 | 5 | 8.4 | 7 | 3.2.3.1 | 6 | 4 | 1: .67 + 27 | 71- 80 | 3.1 | 8 | 3 | 9.7 | 4.6.2 | 7.6 | 6.5 | 5.8.4 | 7 | 1 | 4 | 6 | 1:1.50 + 28 | 81- 90 | 2.3.1 | 8 | 3 | 7 | 4.5.6.2 | 6 | 5 | 5.8.4 | 7 | 1 | 7 | 3 | 1: .43 + 29 | 91- 100 | 1 | 8 | 3 | 9.7 | 6.2 | 6 | 5 | 4 | 7 | 1 | 8 | 2 | 1: .25 + 30 | 101- 110 | 1 | 8 | 4.3 | 7 | 5.6.2 | 6 | 5 | 4 | 7 | 2.3.1 | 7 | 3 | 1: .43 + May | | | | | | | | | | | | | | + 1 | 111- 120 | 2.3.2.1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: .11 + 3 | 121- 130 | 1 | 8 | 5.6.3 | 7 | 4.5.2 | 6 | 5 | 4 | 7 | 1 | 8 | 2 | 1: .25 +4 and 5 | 131- 140 | 3.2.1 | 8[1] | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: .11 + 5 | 141- 150 | 1 | 8 | 4.3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: .11 +--------+----------+---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- + | | | | | | | | 2.3.4.5 | | | 1.2.3.4.5 | | | + | | 2.3.4 | 6.7.8.9 | 3.4.5 | 4.5.6.7.8.9 | 6.7.8.9 | 1.2.3.4.5 | 6.7.8 | 3.4.5.6.7.8 | 5.6.7 | 6.7.8.9 | | | + | +---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- + 6 | 1- 10 | 2 | 6 | 3 | 4 | 6 | 3.2.1 | 6.2 | 5.6.7.8.3 | 5 | 6.1 | 6 | 4 | 1: .67 +========+==========+=========+=========+===========+=============+===========+===========+===========+=============+===========+===========+===+===+======== + +[Footnote 1: End of series on May 4.] + + + +By reading downward in any particular column of results, one obtains a +description of the changes in the animal's reaction to a particular +setting of the doors. Thus, for instance, in the case of setting 1, +which was presented to the animal in trials numbered 1, 11, 21, and so +on to 141, it is clear from the records that no definite improvement +occurred. But oddly enough, in the case of setting 10, which presented +the same group of open doors, almost all of the reactions are right in +the lower half of the column. For setting 2, it is evident that mistakes +soon disappeared. + +Comparison of the data of table 1 indicates that the number of correct +first choices is inversely proportional to the number of doors in use, +while the number of choices made in a given trial is directly +proportional to the number of doors in use. + +During the first week of work on this problem, Skirrl improved markedly. +His performance was somewhat irregular and unpredictable, but on the +whole the experiment seemed fairly satisfactory. Cold, cloudy, or rainy +days tended to diminish steadiness and to increase the number of +mistakes. Similarly, absence of hunger was unfavorable to continuous +effort to find the right box. + +The period of confinement, as punishment for wrong choices, was +increased from thirty seconds to sixty seconds on April 26. But there is +no satisfactory evidence that this favored the solution of the problem. +Work on May 4 was interrupted by a severe storm, the noise of which so +distracted the monkey that he ceased to work. Consequently, observations +were interrupted on the completion of trial 132, and on May 5, the +series was begun with setting 3. On this date, eighteen trials were +given in succession, and in only one of them did a mistake occur. Since +the ten trials numbered 133 to 142 were correct, Skirrl was considered +to have solved problem 1, and systematic training was discontinued. + +On the following day, as a measure of the extent to which the animal had +learned to select the first door at the left no matter what its position +or the number of doors in the group presented, a control series was +given in which the settings differed from the regular series of +settings. These supplementary settings are presented at the bottom of +table 1 together with the records of reaction in ten trials. + +Since in only six of these ten control settings was the first choice +correct, it is scarcely fair to insist that the animal was reacting on +the basis of an ideational solution of the problem. Rather, it would +seem that he had learned to react to particular settings. A careful +study of all of the data of response, together with notes on the varied +behavior of the animal during the experiments, justifies the statement +that Skirrl's solution of problem 1 was incomplete and unreliable. It +was highly dependent upon the particular situation, or even the +particular door at the left end of the group, and slightly if at all +dependent upon anything comparable to the human idea of first at the +left of the group. + +This particular series of observations has been described and discussed +in some detail in order to make the chief points of method clear. It +will be needless, hereafter, to refer explicitly to many of the +characteristics of reaction or to the important points in the +construction of tables which have been mentioned. + +A graphic representation of Skirrl's learning process in problem 1 is +presented in figure 18. The irregularities are most striking, and fairly +indicate the erraticness of the animal. The curve is based upon the data +in next to the last column of table 1, that is, the column presenting +the errors or wrong first choices in each series of trials. + +Unquestionably, the form of such a curve of learning should be +considered in connection with the method or methods of selecting the +right box employed by the animal during the course of experimentation. +It appears from an analysis of the behavior of Skirrl in problem 1 that +there developed a single definite and persistent method, namely, that of +going to one box in the group, and in case it happened to be a wrong +one, of choosing, on emergence from it, the next toward the right end of +the group, and so on down the line. Having reached the extreme right +end, the tendency was to follow the side of the reaction-chamber around +to the opposite end and to enter the first box at the left end of the +group, which was, of course, the right one. This method appears, with +certain slight variations, in approximately ninety per cent of the +trials which involved incorrect choices. Thus, in the case of trials 121 +to 130, of which eight exhibit right first choices, the remaining two +exhibit the method described above except that the final member at the +right end of the group was in each case omitted. + +[Illustration: FIGURE 18.--Error curves of learning for the solution of +problem 1 (first box at left end).] + +On the whole, Skirrl's behavior in connection with this problem appears +to indicate a low order of intelligence. He persisted in such stupid +acts as that of turning, after emergence from the right box, toward the +right and passing into the blind alley I, instead of toward the left, +through G and H, to D. In contrast with the other animals, he spent much +time before the closed doors of the boxes, instead of going directly to +the open doors, some one of which marked the box in which the reward of +food could be obtained. It is, moreover, obvious that his responses, as +they appear in table 1, are extremely different from those of a human +being who is capable of bringing the idea of first at the left end to +bear upon the problem in question. + + +_Problem 2. Second from the Right End_ + +Following the series of control trials of problem 1 given to Skirrl on +May 6, a period of four days was allowed during which the animal was +merely fed in the boxes each day. This was done in order that he should +partially lose the effects of his previous training to choose the first +box at the left before being presented with the second problem, the +second box from the right. + +On May 11 regular experimentation was begun with problem 2. Naturally +the situation presented unusual difficulties to the monkey because of +his previously acquired habit, and on the first day it was possible to +give only five trials, in all except the first of which Skirrl had to be +aided by the experimenter to find the right box. He persistently, as +appears in the first line of records of table 2, entered the first box +at the left. The series was continued on May 13, but with very +unsatisfactory results, since he apparently had been greatly discouraged +by the unusual difficulties previously met. Only four trials could be +given, and in these the showing made was very poor. It is noteworthy, +however, that in trials 6, 7, and 8, May 13, there was no marked +tendency to choose the first box at the left. Thus quickly had the force +of the previous habit been broken. + +For problem 2, the total number of open doors in the ten settings is +fifty, as appears from the data on page 18, and as ten of these fifty +open doors may be defined as right ones, the expected ratio of right to +wrong first choices in the absence of previous training is 1 to 4. The +actual ratio for the first series given in problem 2 is 1 to 8, while in +the second series it is 0 to 10. + +On the morning of May 13, work was interrupted in the ninth trial by +what seemed at the moment a peculiarly unfortunate accident, but in the +light of later developments, an incident most fruitful of valuable +results. + +Skirrl, in trial 9, directly entered box 1. Since this was not the right +box, he was punished by being confined in it for ten seconds. While in +the box he howled and when the entrance door was raised for him to +retrace his steps, he came out with a rush, showing extreme excitement +and either rage or fear, I could not be sure which. At intervals he +uttered loud cries, which I am now able to identify as cries of alarm. +Repeatedly he went to the open door of box 1 and peered in, or peered +down through the hole in the floor which received the staple on the +door. He refused to enter any one of the open boxes and continued, at +intervals of every half minute or so, his cries. For thirty minutes I +waited, hoping to be able to induce him to complete the series of +trials, but in vain. Although it was obvious that he was eager to escape +from the apparatus, he would not enter any of the boxes even when the +exit doors were raised. Instead, he gnawed at the door (12 in fig. 17) +to the alleyway D and attempted to force his way through, instead of +taking the easy and clear route to the alleys, through one of the boxes. +His behavior was most surprising and puzzling. Finally, I gave up the +attempt to complete the series and returned him to his cage by way of +the entrance door to the response-compartment E. + +I then entered the apparatus to seek some explanation of the animal's +behavior, and my search was rewarded by the finding of two sharp pointed +nails which protruded for an inch or more in the middle of the floor of +box 1. My assistant, who had been charged with the task of installing +the locks for the several doors, had used nails instead of screws for +attaching staples underneath the floor and had neglected to clinch the +nails. Skirrl, in the dim light of the box, doubtless stepped upon one +of the nails and inflicted a painful, although not serious, injury upon +himself. It was impossible for him to see clearly the source of his +injury. He was greatly frightened and expressed the emotion most +vigorously. His behavior strongly suggested a superstitious dread of +some unseen danger. It may be that the instinctive fear of snakes, so +strong in monkeys, was partly responsible for his response. + +The first result of this accident was that more than two weeks were +lost, for it was impossible, during the next few days, to induce the +animal to enter any of the multiple-choice boxes voluntarily. From May +14 to May 24, I labored daily to overcome his newly acquired fear. The +usual procedure was to coax him through one box after another by +standing at the exit door with some tempting morsel of food. After +several days of this treatment, he again trusted himself to the boxes, +although very circumspectly and only when both entrance and exit doors +were raised. Not until May 24 was it possible to resume regular +experimentation, and on that day it was found necessary to indicate the +right box by raising the exit door slightly and then immediately +lowering it. Trials in which this form of aid was given are indicated in +table 2 by a star following the last choice. + +Gradually, Skirrl regained his confidence in the apparatus and began to +work more naturally. For a long time he would not stand punishment, and +it was necessary for the experimenter to be very careful in locking the +doors, since the sound of the bar sliding beneath the floor often +frightened and caused him to quit work. Day after day the tendency to +peer through the holes in the floor at the entrance to the boxes +rendered it clear that the animal feared some danger from beneath the +floor. This behavior was so persistent that much time was wasted in the +experiments. + +On the last day of May, punishment by confinement for ten seconds in +wrong boxes was introduced, but since this tended to discourage the +monkey, there was substituted for it on June 1 the punishment of forcing +him to work his way out of each wrong box by raising the entrance door +which had been closed behind him. This he could fairly readily do, and +his stay in a box rarely measured more than ten seconds. + +As a variation in the mode of procedure, confinement for thirty seconds +was tried on June 5, but it worked unsatisfactorily and had to be +abandoned. During this series, the animal was startled by the sound from +one of the sliding bars under the floor, and in the sixth trial he +refused to work. + +As improvement was very slow, varied modes of rewarding and punishing +the animal were tried in the hope of discovering a means of facilitating +the work. Among the former are the use of banana, grapes, peanuts, and +other eagerly sought foods in varying quantities, and in the latter are +included periods of confinement ranging from ten seconds to sixty +seconds. In the end, confinement of about thirty seconds, combined with +a small quantity of food which was much to the monkey's taste, gave most +favorable results. + +All this time Skirrl's attention to the task in hand was seldom good. He +was easily diverted and even when extremely hungry, often stopped work +in the middle of an early trial, yawned repeatedly and finally sat down +to wait for release from the apparatus. + +The results obtained during the long continued trials with this animal +in problem 2 are presented in table 2, which differs from the previously +described table, first, in that several of the trials are followed by an +asterisk to indicate that aid was given by the experimenter, and second, +in that two additional columns, headed, respectively, R and W, are +presented. These give the right and wrong first choices for each day, +whereas the two columns preceding them give the same data for each +series of ten trials. Similarly, the ratio of right to wrong choices is +presented for each day in table 2, instead of for each series of ten +trials as in table 1. + +From the results of table 2, several peculiarly interesting facts +appear. In the first place the influence of the habit of choosing the +first box at the left disappears with surprising suddenness, and in the +second place, there are remarkable contrasts in the results for +different settings as they appear in their respective vertical columns. +Thus, in the case of setting 1, after the first trial mistakes became +relatively infrequent, whereas in setting 6, which involved the same +number of doors, mistakes continued to be the rule until nearly a +thousand trials had been given. The most likely explanation of this +difference is that for some reason the animal avoided box 9. + +The _reactive tendencies_, or better, the _methods of reaction_ which +manifested themselves during this long series of observations may be +described as follows: (a) choice of the first box at the left; (b) +random choice with tendency to choose first, a box near the middle of +the group; (c) choice of first box at the right followed by the one next +to it on the left; (d) direct choice of the right box. + + + +TABLE 2 + +Results for Skirrl, _P. irus_, in Problem 2 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | 1.2.3.4.5 | | | R | W | R | W | of + | trials | 7.8.9 | 1.2.3.4 | 2.3.4.5.6.7 | 1.2.3.4.5.6 | 4.5.6.7.8 | 1.2.3 | 2.3.4.5 | 6.7.8.9 | 1.2.3.4 | 3.4.5.6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + May | | | | | | | | | | | | | | | | + 11&13 | 1- 9 | 7.7.9.7.8 | {1.2.2.1.4.1 | {2.3.2.3.2.5 | {4.6.1.4.1.1 | 4.4.7 | 3.1.2 | 4 | 4.1.8 | 1 | | 1 | 8 | 1 | 8 | 1: 8.00 + | | | {2.1.2.1.3 | {2.3.2.5.6 | {2.6.1.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 24 | 11- 20 | 8*[1] | 2.4.3* | 4.5.6* | 2.2.5* | 5.6.6.7* | 3.1.2 | {5.2.3.5.3.2 | 4.6.8* | 4.4.3* | 5.5.6.7* | 0 |10 | 0 |10 | 0:10.00 + | | | | | | | | {3.5.2.4* | | | | | | | | + | | | | | | | | | | | | | | | | + 25 | 21- 30 | 8* | 4.4.3* | 5.6 | {6.6.2.3.4 | 6.7 | 2 | 4 | 5.6.3.8 | 4.4.3 | 6.4.6.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | {6.6.5* | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 26 | 31- 40 | 8 | 4.3 | 6 | 4.5 | 6.7 | 3.2 | 5.4 | 5.8 | 4.3 | 5.3.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | | | | | | | | + 27 | 41- 50 | 8 | 4.4.3 | 6 | 5 | 6.8.6.8.7 | 3.3.3.2 | 5.4 | {6.5.4.3 | 4.3 | 5.4.8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | {2.1.5.8 | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 51- 60 | 8 | 4.4.3 | 7.6 | 5 | 5.6.7 | 3.3.3.2 | 4 | {5.4.3 | 4.3 | {5.4.3.3.4.5 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | {3.6.8 | | {6.4.3.5.7 | | | | | + | | | | | | | | | | | | | | | | + 29 | 61- 70 | 8 | 4.3 | 6 | 6.6.5 | 7 | 3.3.3.2 | 5.4 | 7.6.4.7.6.8 | 4.3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 31 | 71- 80 | 8 | 4.4.4.3 | 6 | 6.5 | 6.8.7 | 3.2 | 5.4 | {6.7.6.4.3 | 4.3 | 6.7 | 2 | 8 | 2 | 8 | 1: 4.00 + June | | | | | | | | | {2.6.3.7.8 | | | | | | | + | | | | | | {6.8.6.5.4 | | | | | | | | | | + 1 | 81- 90 | 8 | 4.3 | 6 | 5 | {6.5.6.5.8 | 3.1.3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | | | + | | | | | | {5.4.6.4.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 91- 100 | 9.7.8 | 4.2.4.3 | 7.5.6 | 5 | 6.8.7 | 3.3.1.2 | 5.3.4 | 8 | 4.3 | 6.8.7 | 2 | 8 | 7 |13 | 1: 1.86 + 2 | 101- 110 | 8 | 4.3 | 6 | 5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 6.8.6.5.7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + " | 111- 120 | 8 | 4.3 | 7.3.5.7.6 | {6.2.3.6.4 | 7 | 3.2 | {5.2.3.5.3.2 | 9.6.4.7.8 | {4.1.2 | 6.8.7 | 2 | 8 | 6 |14 | 1: 2.33 + | | | | | {3.6.2.5 | | | {3.5.2.3.4 | | {4.2.3 | | | | | | + | | | | | | | | | | | {6.8.6.3 | | | | | + 3 | 121- 130 | 8 | 4.4.3 | 6 | 5 | 6.7 | 3.2 | {5.3.2.3 | 8 | 4.2.3 | {5.4.5.8.8 | 4 | 6 | | | + | | | | | | | | {5.2.5.4 | | | {6.3.8.7 | | | | | + | | | | | | | | | | | | | | | | + " | 131- 140 | 8 | 4.3 | 5.7.3.2.6 | 4.5 | 5.7 | 1.3.2 | 5.3.4 | 6.7.8 | 4.2.1.3 | 7 | 2 | 8 | 6 |14 | 1: 2.33 + | | | | | | | | | | | | | | | | + 4 | 141- 150 | 8 | 4.3 | 7.6 | 6.5 | 7 | 2 | {5.3.2.3 | 6.8 | 4.1.3 | 5.6.7 | 3 | 7 | | | + | | | | | | | | {5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | + " | 151- 160 | 8 | 4.3 | 6 | 5 | 6.7 | 2 | 4 | 5.6.7.8 | 4.3 | 5.6.8.7 | 5 | 5 | 8 |12 | 1: 1.50 + 5 | 161- 170 | 8 | 4.3 | 7.6 | 6.5 | 6.8.7 | 3.2 | 5.3.2.3.5.4 | 8 | 4.3 | 6.7 | 2 | 8 | | | + " | 171- 176 | 8 | 2.4.3 | 7.6 | 6.5* | 8.7 | 3.2* | | | | | 1 | 5 | 3 |13 | 1: 4.33 + 7 | 177- 180 | | | | | | | 5.4 | 8 | 4.4.3 | 8.7 | 1 | 3 | | | + " | 181- 190 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.3.2.5.4 | 8 | 4.3 | 7 | 4 | 6 | 5 | 9 | 1: 1.80 + 8 | 191- 200 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 | | | + " | 201- 210 | 8 | 4.3 | 6 | 6.4.6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 6 |14 | 1: 2.33 + 9 | 211- 220 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.6.7 | 2 | 8 | | | + " | 221- 230 | 9.8 | 4.3 | 7.6 | 6.5 | 6.7 | 3.2 | 5.4 | 7.6.8 | 4.3 | 7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | | | | | | | | | | | + 10 | 231- 240 | 8 | 4.3 | 7.6 | 6.5 | 6.7 | 3.2 | 5.4 | {3.2.3.2.4.3 | 4.3 | 7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | {2.5.4.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + 11 | 241- 250 | 8 | 4.3 | 7.6 | 6.6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | | | | | | | | 12 | 251- 260 | 8 | 4.3 | 6 | 6.5 | 6.7 | 3.3.2 | 5.4 | {7.6.7.7 | 3 | 3.7* | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | {6.9.8* | | | | | | | + | | | | | | | | | | | | | | | | 14 | 261- 270 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | {5.3.4.3 | 3 | {3.3.3.3.4 | 5 | 5 | 5 | 5 | 1: 1.00 + | | | | | | | | | {9.8* | | {4.6.4.7* | | | | | + | | | | | | | | | | | | | | | | 15 | 271- 280 | 7.9.8 | 4.2.3 | 3.4.3.7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 1 | 9 | | | + " | 281- 290 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 3 | 7 | 4 |16 | 1: 4.00 + | | | | | | | | | | | | | | | | | | | | | | | | | {4.3.2.3 | | | | | | | + 16 | 291- 300 | 7.8 | {4.4.4 | 6 | 6.5 | 7 | 3.3.2 | 5.4 | {6.5.4.3 | 4.3 | 6.7 | 2 | 8 | | | + | | | {4.4.3 | | | | | | {5.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | " | 301- 310 | 8 | 4.4.3 | 7.6 | 6.5 | 7 | 3.3.2 | 5.5.4 | {7.6.5.4.6 | 4.3 | 7 | 3 | 7 | 5 |15 | 1: 3.00 + | | | | | | | | | {5.7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | 17 | 311- 320 | 7.8 | 4.3 | 7.6 | 6.6.5 | 7 | 3.2 | 5.4 | 7.6.7.6.7.8 | 4.3 | 7 | 2 | 8 | | | + " | 321- 330 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 6.7 | 2 | 8 | 4 |16 | 1: 4.00 + 18 | 331- 340 | 7.7.8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | | | + " | 341- 350 | 8 | 4.3 | 7.6 | 6.6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | 7 |13 | 1: 1.86 + 19 | 351- 360 | 8 | 4.3 | 7.6 | 6.5 | 6.5.6.5.7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 361- 370 | 8 | 4.3 | 7.6 | 6.4.3.6.5 | 7 | 3.2 | 5.4 | 9.8 | 4.3 | 7 | 3 | 7 | 6 |14 | 1: 2.33 + 21 | 371- 380 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 8.7 | 2 | 8 | | | + " | 381- 390 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 6 |14 | 1: 2.33 + 22 | 391- 400 | 8 | 4.3 | 7.6 | 6.5 | 6.5.4.6.7 | 3.3.3.2 | 5.4 | 6.7.8 | 4.4.3 | 7 | 2 | 8 | | | + " | 401- 410 | 8 | 3 | 7.6 | 6.5 | 8.7 | 2 | 5.4 | 6.7.7.8 | 3 | 7 | 5 | 5 | 7 |13 | 1: 1.86 + | | | | | | | | | | | | | | | | 23 | 411- 420 | 8 | 4.4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | {7.6.7.6 | 4.3 | 7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | {6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | 24 | 421- 430 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 6 | 4 | | | + " | 431- 440 | 8 | 3 | 7.6 | 6.5 | 7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 |11 | 9 | 1: 0.82 + 25 | 441- 450 | 7.8 | 4.4.3 | 7.6 | 6.5 | 6.5.7 | 3.3.2 | 5.5.4 | 7.8 | 4.3 | 7 | 1 | 9 | 1 | 9 | 1: 9.00 + 26 | 451- 460 | 7.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 461- 470 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 6 |14 | 1: 2.33 + 28 | 471- 480 | 8 | 4.4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 9.8 | 3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + 29 | 481- 490 | 8 | 4.3 | 7.7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + 30 | 491- 500 | 7.9.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 501- 510 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.4.3 | 8.7 | 2 | 8 | 5 |15 | 1: 3.00 + July | | | | | | | | | | | | | | | | + 1 | 511- 520 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | 2 | 521- 530 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | {7.6.5.6.5 | 4.4.3 | 7 | 3 | 7 | | | + | | | | | | | | | {6.5.6.8 | | | | | | | + | | | | | | | | | | | | | | | | " | 531- 540 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 7 |13 | 1: 1.86 + 3 | 541- 550 | 7.8 | 4.4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 5.5.7 | 3 | 7 | | | + " | 551- 560 | 7.8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 5 | 5 | 8 |12 | 1: 1.50 + 5 | 561- 570 | 7.7.8 | 4.3 | 6 | 6.5 | 6.7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 571- 580 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 4 | 6 | 7 |13 | 1: 1.86 + | | | | | | | | | | | | | | | | | | | | | | {6.5.4.6.5 | | | | | | | | | | + 6 | 581- 590 | 7.8 | 4.3 | 7.6 | 6.6.5 | {5.4.5.4.4 | 2 | 3.4 | 6.5.4.3.7.8 | 3 | 7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | {6.5.6.5.8.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | 7 | 591- 600 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 8.7 | 3 | 7 | | | + " | 601- 610 | 7.8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 1 | 9 | 4 |16 | 1: 4.00 + 8 | 611- 620 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 | | | + " | 621- 630 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 9.8 | 4.3 | 8.7 | 1 | 9 | | | + " | 631- 640 | 8 | 4.4.3 | 7.7.6 | 6.5 | 8.7 | 3.2 | 4 | 8 | 4.3 | 8.7 | 3 | 7 | 6 |24 | 1: 4.00 + | | | | | | | | | | | | | | | | 9 | 641- 650 | 7.8 | 4.3 | 7.6 | 6.5 | 6.7 | 3.2 | {3.2.5.3 | 7.6.5.4.8 | 3 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | {2.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | | | | | | | | | | {6.5.4.3.7 | | | | | | | + 10 | 651- 660 | 7.8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | {6.5.4.7.6 | 4.3 | 7 | 3 | 7 | | | + | | | | | | | | | {5.4.8 | | | | | | | + | | | | | | | | | | | | | | | | 10 | 661- 670 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 6 | 4 | 9 |11 | 1: 1.22 + 12 | 671- 680 | 7.8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 6.5.4.7.8 | 4.3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | | | | | | | | 13 | 681- 690 | 8 | 3 | 7.6 | 6.5 | {6.5.4 | 3.2 | 4 | 6.7.8 | 3 | {6.5.4.5 | 4 | 6 | | | + | | | | | | {6.5.7 | | | | | {6.5.8.7 | | | | | + | | | | | | | | | | | | | | | | " | 691- 700 | 8 | 3 | 6 | 5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 8 | 2 |12 | 8 | 1: 0.67 + | | | | | | | | | | | | | | | | 14 | 701- 710 | 8 | 3 | 7.6 | 6.5 | {6.5.4.5 | 2 | 3.5.4 | 8 | 3 | 7 | 6 | 4 | | | + | | | | | | {4.6.8.7 | | | | | | | | | | + " | 711- 720 | 8 | 3 | 6 | 5 | 7 | 2 | 5.4 | 6.5.4.8 | 3 | 6.5.7 | 7 | 3 |13 | 7 | 1: 0.54 + 15 | 721- 730 | 7.8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | | | + " | 731- 740 | 8 | 3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 6 | 4 |11 | 9 | 1: 0.82 + 16 | 741- 750 | 7.8 | 3 | 6 | 6.5 | 7 | 3.2 | 4 | 8 | 3 | 7 | 7 | 3 | | | + " | 751- 760 | 7.8 | 3 | 7.6 | 6.5 | 7 | 2 | 4 | 7.8 | 4.3 | 7 | 5 | 5 |12 | 8 | 1: 0.67 + 17 | 761- 770 | 8 | 4.3 | 6 | 5 | 8.7 | 3.2 | 5.4 | 8 | 4 | 7 | 6 | 4 | | | + " | 771- 780 | 8 | 2.2.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 3 | 7 | 9 |11 | 1: 1.22 + 19 | 781- 790 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 3.4 | 7.6.5.8 | 3 | 7 | 6 | 4 | | | + " | 791- 800 | 7.8 | 3 | 6 | 5 | 7 | 2 | 5.4 | 8 | 3 | 6.5.6.7 | 7 | 3 | | | + " | 801- 810 | 8 | 2.3 | 6 | 5 | 6.5.7 | 2 | 5.4 | 8 | 3 | 7 | 7 | 3 |20 |10 | 1: 0.50 + 20 | 811- 820 | 7.8 | 3 | 7.6 | 5 | 7 | 3.3.2 | 5.4 | 8 | 2.2.3 | 7 | 5 | 5 | | | + " | 821- 830 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 4 | 8 | 2.3 | 8.7 | 6 | 4 |11 | 9 | 1: 0.82 + 21 | 831- 840 | 8 | 3 | 5.4.5.6 | 5 | 7 | 2 | 4 | 6.7.8 | 3 | 8.7 | 7 | 3 | | | + " | 841- 850 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 3.2.4 | 8 | 3 | 7 | 7 | 3 |14 | 6 | 1: 0.43 + 22 | 851- 860 | 8 | 4.3 | 6 | 5 | 7 | 3.2 | 3.5.4 | 8 | 3 | 8.7 | 6 | 4 | | | + " | 861- 870 | 7.8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 4 | 8 | 3 | 8.7 | 3 | 7 | | | + " | 871- 880 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 |11 |19 | 1: 1.73 + 23 | 881- 890 | 8 | 3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | | | + " | 891- 900 | 8 | 3 | 7.6 | 6.5 | 7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | 9 |11 | 1: 1.22 + 24 | 901- 910 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | | | + " | 911- 920 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 7 | 3 |11 | 9 | 1: 0.82 + 26 | 921- 930 | 7.8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 8 | 2.2.3 | 8.7 | 4 | 6 | | | + " | 931- 940 | 8 | 3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 7 |13 | 1: 1.86 + 27 | 941- 950 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + 28 | 951- 960 | 8 | 3 | 7.6 | 6.5 | 5.4.7 | 2 | 5.5.4 | 8 | 3 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 29 | 961- 970 | 8 | 3 | 7.6 | 5 | 8.7 | 2 | 4 | 8 | 3 | 7 | 8 | 2 | 8 | 2 | 1: 0.25 + | | | | | | | | | | | | | | | | 30 | 971- 980 | 8 | 3 | 4.3.2.6 | 5 | {6.5.4.6 | 2 | 5.5.4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | {6.5.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | 31 | 981- 990 | 8 | 3 | 6 | 6.5 | 8.7 | 2 | 4 | 8 | 3 | 7 | 8 | 2 | 8 | 2 | 1: 0.25 + August | | | | | | | | | | | | | | | | + 2 | 991-1000 | 8 | 3 | 7.6 | 5 | 7 | 2 | {2.3.5.3 | 7.6.8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | | | {2.3.3.4 | | | | | | | | + | | | | | | | | | | | | | | | | 3 | 1001-1010 | 8 | 3 | 7.6 | 5 | 7 | 2 | 4 | 7.6.5.6.7.8 | 3 | 5.4.3.4.3.7 | 7 | 3 | | | + " | 1011-1020 | 8 | 2.3 | 5.6 | 3.2.3.6.5 | 7 | 2 | 5.4 | 9.8 | 2.1.3 | 7 | 4 | 6 |11 | 9 | 1: 0.82 + | | | | | | | | | | | | | | | | 4 | 1021-1030 | 7.8 | 3 | 5.4.3.7.6 | 6.5 | {6.5.6 | 3.2 | 5.4 | 8 | {2.2.4.2 | 8.7 | 2 | 8 | | | + | | | | | | {5.6.7 | | | | {4.2.3 | | | | | | + | | | | | | | | | | | | | | | | " | 1031-1040 | 7.8 | 3 | 6 | 6.4.3.6.5 | 7 | 2 | 3.5.4 | 8 | 2.3 | 8.7 | 5 | 5 | 7 |13 | 1: 1.86 + | | | | | | | | | | | | | | | | 5 | 1041-1050 | 8 | 3 | 6 | 2.3.2.6.5 | 8.7 | 2 | 4 | 8 | 2.2.4.3 | {8.8.6.8.4 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | {6.5.8.7 | | | | | + | | | | | | | | | | | | | | | | 6 | 1051-1060 | 8 | 3 | 6 | 4.2.6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | | | | | | 7 | 1061-1070 | 8 | 3 | 5.4.3.6 | 4.5 | {6.5.6.5 | 2 | 4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | {4.8.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | 9 | 1071-1080 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 7 |10 | 0 |10 | 0 | 1: 0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 1.2.3.4.5 | | | | | | 1.2.3.4 | 2.3.4.5 | | | | | + | | 5.6.7.8 | 2.3.4.5.6 | 6.7.8.9 | 5.6.7 | 1.2.3.4 | 4.5.6 | 2.3.4.5 | 1.2.3 | 5.6.7 | 6.7.8.9 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 10 | 1- 10 | 6.5.7 | 3.2.6.5 | 8 | 6 | 2.4.3 | 5 | 5.4 | 2 | 7.5.2.7.6 | 8 | 5 | 5 | 5 | 5 | 1: 1.00 + 11 | 11- 20 | 7 | 3.6.5 | 8 | 6 | 3 | 6.5 | 4 | 3.2 | 7.6 | 8 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | | | | | | | | | | | | | | {3.2.3.5.3 | | | | | | | | + 12 | 21- 30 | 7 | 2.2.6.5 | 7.8 | 6 | 3 | 5 | {2.5.3.2 | 2 | 6 | 8 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | | | {5.3.2.5 | | | | | | | | + | | | | | | | | {2.5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote 1: First choices correct by reason of aid from the experimenter +are not counted as correct (R) in the summary.] + +[Footnote *: Aided by experimenter.] + + +The method of choosing the first box at the right end and then the one +next to it developed in the case of all except two of the ten settings. +The time of appearance is worth noting. In setting 1, it failed to +appear; in setting 2, it developed early,--after about one hundred +trials; in setting 3, after about one hundred and fifty trials; in +setting 4, after about one hundred and fifty trials; in setting 5, after +about one hundred and seventy trials; in setting 6, after about one +hundred trials; in setting 7, after about fifty trials; in setting 8, it +never developed; in setting 9, after about fifty trials; and in setting +10, it developed very late,--after about four hundred and seventy +trials. + +This method of reaction, although inadequate, proved remarkably +persistent, and it is doubtful whether it had been wholly overcome at +the conclusion of the experiment. In the case of the series of trials +given on June 8, numbered 191 to 200, the method used was either that of +the first at the right and then the next, or direct choice of the right +box. + +Throughout the trials with this problem, the end boxes, numbers 1 and 9, +were avoided. This is at least partially explained by the fact that they +never existed, and obviously never could appear, in problem 2, as right +boxes. In trials 601 to 610, given on July 7, there occurred partial +return to the formerly established method of choosing the first door at +the right. This relapse was characteristic of what happened during the +many days which intervened between the definite appearance of this habit +and the final solution of the problem. + +Especially in connection with such relapses, Skirrl showed extreme +fatigue or ennui and often would refuse to work and simply sit before +the open doors yawning. This happened even when he was extremely hungry +and evidently eager enough for food. + +From July 12 on the hunger motive was increased by feeding the monkey +only in the apparatus and by so regulating the amount of food given in +each trial that he should obtain barely enough to keep him in good +physical condition. An increase in the number of correct choices +promptly resulted, and continued until on July 14 the ratio of choices +was 1 to .54. It appeared from these data that a relatively small number +of choices, say not more than ten a day, the rewards in connection with +which supplied the only food received by the animal, yielded most +favorable results. + +On July 16, the period of confinement in wrong boxes was increased to +sixty seconds, and it was so continued for a number of days. But in the +end, it became clear that the period of thirty seconds, combined with a +liberal reward in the shape of desired food and a single series of ten +trials per day, was most satisfactory. The detailed data of table 2 +indicate that at this time Skirrl was making his choices by memory of +the particular setting. + +Skirrl, on July 17 was evidently hungry and eager to locate food, but +seemingly unable to select the right box. In trial 5 (765th) of the +series, he was punished by confinement in box 8. When the doors were +unlocked in order that the entrance door might be raised to release him, +the lock-bar, sliding under the floor, made a slight grating noise, and +the instant the entrance door was opened, he jumped out excitedly. _He +made no outcry, but as soon as he was out of the box, sat down, and +taking up his right hind foot, examined it for a few seconds._ Having +apparently assured himself that nothing serious had happened, he went on +unconcernedly about his task. The presumption is that the sound of the +lock-bar, associated as it was with his painful experience in box 1, +revived the strongly affective experience of stepping on the nail. +Psychologically described, the sound induced an imaginal complex +equivalent to the earlier painful experience. The behavior seems to the +writer a most important bit of evidence of imagery in the monkey. +Finally, on August 9, after ten hundred and seventy trials, Skirrl +succeeded in choosing correctly in the ten trials of a series, and he +was therefore considered to have solved the problem of the second door +from the right end of the group. + +On the following day, he was given a control series with the settings +which are presented on page 19 and also at the bottom of table 2. In +this series he chose correctly five times,--in other words, as often +correctly as incorrectly. An analysis of the choices indicates, however, +that two of the five correct choices were made in box 8, which, as it +happened, had proved a peculiarly easy one for him throughout the +training, since from the first he tended to avoid door 9. Consequently, +it is only fair to conclude, from the results for this control series +and for those given on August 11 and 12, that the animal chose not on +the basis of anything remotely resembling a general idea of secondness +from the right end, but instead on the basis of gradually acquired modes +of reaction to the particular settings. This conclusion is strengthened +by the fact that he had failed to learn to react appropriately and +readily to most of the settings of the regular series. + +The curve which represents the course of the learning process in this +problem is presented in figure 19. For this and all other curves which +involve more than a single series of observations a day, the method of +construction was as follows: The first series for each day of training +is indicated on the curve by a dot, while the second or third series on +a given day, although space is allowed for them, are not so indicated. +Consequently, the form of the curve is determined chiefly by the first +series per day. The extreme irregularities of this curve are most +interesting and puzzling, as are also the variations in the daily ratios +of right to wrong first choices. Three times in the course of the +training, this ratio rose to 1 to 9, or higher. The causes for such +extreme variations are not easily enumerated, but a few of the most +obvious contributory causes are variations in the weather, especially +cloudiness or fogginess, which rendered the apparatus dark; variations +in the degree of hunger or eagerness for food; differences in the +activities of the animals in the cages outside of the laboratory +(sometimes they were noisy and distracted the subject), and finally, +differences in the physical fitness and attitude of the animal from day +to day. + +The more or less incidental behavior in connection with this experiment +more strongly than the statistical results of the work on problem 2 +indicate the existence of imagery. That ideas played a part in the +solution of the problem is probable, but at best they functioned very +ineffectively. The small number of methods used in the selection of the +right box, and the slight variations from the chief method, that of +choosing the first box at the right end and then the one next to it, +apparently justify Doctor Hamilton's characterization of this monkey as +defective. + + +[Illustration: FIGURE 19.--Error curves of learning for the solution of +problem 2 (second box from right end).] + + +_Problem 3. Alternately First at Left and First at Right_ + +Following the control series given in connection with problem 1, an +interval of rest lasting from August 12 to August 19 was allowed in +order that Skirrl might in part at least lose the effects of his +training and regain his customary interest in the apparatus by being +allowed to obtain food easily instead of by dint of hard labor,--labor +which was harder by far, apparently, than physical activity because it +demanded of the animal certain mental processes which were either +lacking or but imperfectly functional. The difficultness of the daily +tasks appears to be reliably indicated by the tendency to yawn. + +Systematic work on problem 3, which has been defined as alternately the +first door at the left and the first door at the right of the group, was +begun August 19, and for nine days a single series of ten trials per day +was given. Work then had to cease because of the experimenter's return +to Cambridge. + +The results of the work on this problem demand but brief analysis and +comment. The expected ratio of one right to four wrong choices per +series appears (see table 3) for the first series of trials, and _this +in spite of the fact that Skirrl had been trained for several weeks to +choose the second door from the right end_. One would ordinarily have +predicted a much larger number of incorrect choices. The right choices +were due to the monkey's strong tendency to go first to the first door +at the right and thence to the one next to it. Indeed in the series +given on August 24; this method was followed without variation. In other +words, in every one of the ten trials Skirrl entered first the box at +the extreme right end of the group. This necessarily resulted in as many +right as wrong first choices. Consequently, the ratio reads 1 to 1. But +the method was not adhered to, and at no time either before or after +that date did he succeed in equalling this achievement. There was, as a +matter of fact, no steady improvement, and so far as one may judge from +the records which were obtained, the course of events in the solution of +this problem would have been similar to those in problem 2. + + + +TABLE 3 + +Results for Skirrl, _P. irus_, in Problem 3 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + Date | No. of | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | R | W | R | W |Ratio of + | trials | 5.6.7 | 5.6.7 | 1.2.3.4.5.6 | 1.2.3.4.5.6 | 4.5.6.7.8 | 4.5.6.7.8 | 2.3.4.5 | 2.3.4.5 | 3.4.5.6.7.8.9| 3.4.5.6.7.8.9| | | | |R to W +________|___________|______________|______________|______________|______________|______________|______________|______________|______________|______________|______________|___|___|___|___|________ +August | | | | | | | | | | | | | | | | + | | | | {6.5.4.6 | | | | | | | {8.7.6.5 | | | | | + 19 | 1- 10 | 7.5 | 6.7 | {3.2.6.4 | 5.3.6 | {7.8.7.6 | 8 | 4.3.5.4.5.2 | 5 | 9.8.7.6.4.3 | {4.5.8.7 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | {3.6.1* | | {8.6.4 | | | | | {6.5.9* | | | | | + | | | | | | | | | | | | | | | | + | | | | {5.4.6.5 | | {8.7.6.7 | | | | | | | | | | + 20 | 11- 20 | 7.6.5 | {6.5.6.5 | {4.6.5.3 | 5.3.2.4.6 | {7.5.8.8 | 8 | 5.4.3.2 | 4.5 | 8.7.6.5.4.3 | {8.7.6.8.3 | 1 | 9 | 1 | 9 | 1:9.00 + | | | {7 | {2.5.1* | | {7.6.4* | | | | | {7.6.4.3.9 | | | | | + | | | | | | | | | | | | | | | | + | | | | {6.2.5.6 | | | | {5.3.5.4 | | | | | | | | + 21 | 21- 30 | 7.6.7.6.5 | 7 | {5.3.6.5 | 2.5.5.6 | 8.6.5.4 | 8 | {3.5.3.5 | 5 | {9.8.7.6 | 8.9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | {4.3.1* | | | | {4.3.2* | | {5.4.3 | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 23 | 31- 40 | 7.6.5 | 6.5.7 | {6.4.3.2 | 3.2.6 | 8.7.6.4 | 8 | 5.4.5.3.2 | 5.2 | 8.7.3 | 9 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | {5.6.2.1 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 24 | 41- 50 | 7.6.5 | 7 | {6.2.5 | 6 | {8.7.8.7 | 8 | 5.3.2 | 5 | {9.8.7.6 | 9 | 5 | 5 | 5 | 5 | 1:1.00 + | | | | {4.3.1 | | {5.7.5.4 | | | | {5.4.3 | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | {8.7.3.6 | | | | | + 25 | 51- 60 | 7.6.5 | 6.5.7 | 5.2.1 | 6 | 8.5.4 | 8 | 2 | 2.5 | 9.8.7.4.3 | {8.7.5.3 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | {8.7.9* | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 26 | 61- 70 | 7.6.5 | 6.5.7 | 1 | 2.1.6 | 8.7.6.4 | 8 | 2 | 3.2.5 | 9.8.7.5.3 | {3.6.8.3 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | {4.7.9 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | {8.6.3.3 | | | | | + 27 | 71- 80 | 7.6.5 | 7 | 2.1 | 1.5.6 | 8.7.6.4 | 8 | 2 | 5 | 9.8.7.6.3 | {7.5.3.8 | 4 | 6 | 4 | 6 | 1:1.50 + | | | | | | | | | | | {3.6.9* | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 81- 90 | 7.6.7.5 | 7 | 3.1 | 6 | 8.6.4 | 4.8 | 2 | 2.4.5 | 8.7.4.3 | 3.8.9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + + + + +2. Sobke, _Pithecus rhesus_ + + +_Problem 1. First at the Left End_ + +Sobke was somewhat afraid of the experimenter when the investigation was +undertaken, and instead of willingly coming out of his cage when the +door was raised, he often had to be coaxed out and lured into the +apparatus with food. Whereas Skirrl was frank and rather aggressive, +Sobke was stealthy in his movements, furtive, and evidently suspicious +of the experimenter as well as of the apparatus. He was perfectly safe +to approach, but would not permit anyone to touch him. After a few days, +he began to take food from the hands of the experimenter. + +Preliminary work to acquaint this monkey with the routine of the +experiment was begun on April 13. As in the case of Skirrl, he was lured +into the apparatus and was taught the route through the boxes to the +starting point by being allowed to obtain food once each day in each of +the nine boxes. The procedure was simple. The entrance door and the exit +door of a particular box were raised and the animal admitted to the +reaction-compartment and permitted to pass through the box whose doors +stood open, take its food, and return to the starting point. Sobke very +quickly learned the route perfectly and came to work steadily and +rapidly. After five days of preliminary work of this sort, he was so +thoroughly accustomed to the apparatus that it was evidently desirable +to begin with regular training experiments. + +The first series of trials was given on April 19. Both punishment and +reward were employed from the first. The punishment consisted of +confinement for thirty seconds in each wrong box, and the reward of a +small piece of banana, usually not more than a tenth of a medium sized +banana for each correct choice. The total time for the first series of +trials was fourteen minutes. This indicates that Sobke worked rapidly. +My notes record that he worked quickly though shyly, wasted almost no +time, made few errors of choice, and waited quietly during confinement +in the boxes. In this, also, he differed radically from Skirrl who was +restless and always tried to escape from confinement. + +Throughout the work on problem 1, punishment and reward were kept +constant. Everything progressed smoothly; there were no such +irregularities of behavior as appeared in the case of Skirrl, and +consequently the description of results is a relatively simple matter. +Sobke invariably chose the end boxes. His performance was in every way +superior to that of Skirrl. + +As previously, the detailed results are presented in tabular form (table +4). From this table it appears that, whereas the expected ratio of right +to wrong first choices for this problem is 1 to 2.5, the actual ratio +for Sobke's first series was 1 to .67. This surprisingly good showing is +unquestionably due to his marked tendency to choose the end box of a +group; and this tendency, in turn, may in part be the result of the +preliminary training, for during that only one box was open each time. +But, if the preliminary training were responsible for Sobke's tendency, +it should be noted that it had very different effect upon Skirrl, and, +as will be seen later, upon Julius. + +The results for the ten different settings of the doors for problem 1 as +they appear in table 4 are of interest for a number of reasons. In the +first place, the setting 1. 2. 3 appearing twice,--at the beginning of +the series and again at the end--yielded markedly different results in +the two positions. For whereas no mistakes were made in the case of +setting 1, there were fifty per cent of incorrect first choices for +setting 10. Again, satisfactory explanation is impossible. It is +conceivable that fatigue or approaching satiety may have had something +to do with the failures at the end of the series, but as a rule, as is +indicated by settings 1, 2, and 6, if correct choices were made at the +beginning, they continued throughout the day's work. + +In this problem, Sobke's improvement was steady and fairly rapid, and in +the eighth series, trials 71 to 80, only correct first choices appear. +Consequently, seventy trials were required for the solution of the +problem. This number is in marked contrast with Skirrl's one hundred and +thirty-two trials. + +Immediately following the first perfect series, Sobke was given two +series of control tests on April 28. Conditions were unfavorable, since +the day was stormy and the rain pattering on the sheet-iron roof made a +great din. Nevertheless, he worked steadily and well up to the sixth +trial, which was preceded by a slight delay because of the necessity of +refilling some of the food boxes. After this interruption, wrong choices +occurred in trial 6. And again after trial 9, there was brief +interruption, followed by wrong choices in trial 10. The ratio of right +to wrong choices for this first control series was therefore 1 to .25. + + + +TABLE 4 + +Results for Sobke, _P. rhesus_, in Problem 1 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | | | R | W | R | W | of + | trials | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + April | | | | | | | | | | | | | | | | + 19 | 1-10 | 1 | 8 | 3 | 9.7 | 6.2 | 6 | 7.5 | 4 | 9.7 | 1 | 6 | 4 | 6 | 4 | 1:0.67 + 20 | 11-20 | 1 | 8 | 3 | 7 | 2 | 6 | 7.5 | 8.4 | 9.9.7 | 1 | 7 | 3 | 7 | 3 | 1:0.43 + 21 | 21-30 | 1 | 8 | 4.3 | 9.7 | 2 | 6 | 5 | 8.4 | 7 | 1 | 7 | 3 | 7 | 3 | 1:0.43 + 22 | 31-40 | 1 | 8 | 3 | 7 | 6.2 | 6 | 6.5 | 4 | 7 | 3.1 | 7 | 3 | 7 | 3 | 1:0.43 + 23 | 41-50 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 9.7 | 3.1 | 8 | 2 | 8 | 2 | 1:0.25 + 24 | 51-60 | 1 | 8 | 3 | 9.7 | 2 | 6 | 5 | 4 | 7 | 2.1 | 8 | 2 | 8 | 2 | 1:0.25 + 26 | 61-70 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 3.1 | 9 | 1 | 9 | 1 | 1:0.11 + 27 | 71-80 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 |10 | 0 |10 | 0 | 1:0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | 2.3.4 | | | 1.2.3.4.5 | | | | | + | | 2.3.4 | 6.7.8.9 | 3.4.5 | 4.5.6.7.8.9 | 6.7.8.9 | 1.2.3.4.5 | 5.6.7.8 | 3.4.5.6.7.8 | 5.6.7 | 6.7.8.9 | | | | | + | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ | | | | + 28 | 1-10 | 2 | 6 | 3 | 4 | 6 | 5.4.1 | 2 | 3 | 5 | 5.4.2.1 | 8 | 2 | | | + " | 11-20 | 2 | 6 | 3 | 4 | 6 | 2.1 | 2 | 3 | 5 | 1 | 9 | 1 |17 | 3 | 1:0.18 + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + + + +Six minutes after completion of the first control series, a second was +given under slightly more favorable conditions, and in this only a +single wrong choice occurred, in that box 2 was first chosen in trial 6 +instead of box 1. From the results of these two control series, it is +evident that Sobke's solution of problem 1 is reasonably adequate. He is +easily diverted or disturbed in his work by any unusual circumstances, +but so long as everything goes smoothly, he chooses with ease and +certainty. Whether it is fair to describe the behavior as involving an +idea of the relation of the right box to the other members of the group +would be difficult to decide. I hesitate to infer definite ideation from +the available evidence, but I strongly suspect the presence of images +and relatively ineffective or inadequate ideation. + +It is perfectly evident that Sobke is much more intelligent than Skirrl. +In practically every respect, he adapted himself more quickly to the +experimental procedure and progressed more steadily toward the solution +of the problem than did Skirrl. The contrast in the learning processes +of the two monkeys could scarcely be better exhibited than by the curves +of learning which are presented in figure 18. The first, that for Sobke, +is surprisingly regular; the second, that for Skirrl, is quite as +surprisingly irregular. These results correlate perfectly with the +steadiness and predictability of the former's responses and the +irregularity and erraticness of the latter's. + + +_Problem 2. Second from the Right End_ + +On the completion of problem 1 Sobke was in perfect condition, as to +health and training, for experimental work. He had come to work quietly, +fairly deliberately, and very steadily. His timidity had diminished and +he would readily come to the experimenter for food, although still he +was somewhat distrustful at times and became timid when anything unusual +occurred in the apparatus. + +As preparation for problem 2, a break in regular experimentation +covering four days followed the control series of problem 1. On each of +these four days the monkey was allowed to get food once from each of the +nine boxes, both doors of a given box being open for the trial and all +other doors closed. For this feeding experiment, the doors were opened +in irregular order, and this order was changed from day to day. + +Systematic work with problem 2 began on May 3, with punishment of thirty +seconds for mistakes and a liberal reward of food for each success. +Early in the series of trials it was discovered that Sobke was likely to +become discouraged and waste a great deal of time unless certain aid +were given by the experimenter. On this account, after the first two +trials, the method was adopted of punishing the animal by confinement +for the first ten mistakes in a trial, and of then, if need be, +indicating the right box by slightly and momentarily raising the exit +door. Every trial in which aid was thus given by the experimenter is +indicated in table 5 by an asterisk following the last choice. In the +first series of trials for this problem, aid had to be given in seven of +the ten trials, and even so the series occupied seventy-one minutes. It +is possible that had no aid been given, the work might have been +continued successfully with a smaller number of trials than ten per day. +But under the circumstances it seemed wiser to avoid the risk of +discouraging and thus spoiling the animal for use in the experiment. It +should be stated, also, that it proved impossible to adhere to the +period of thirty seconds as punishment in this series. For the majority +of the wrong choices confinement of not more than ten seconds was used. + +For the second series, given on May 4, the conditions were unfavorable +in that it was dark and rainy, and the noise of the rain on the roof +frightened Sobke. He refused to work after the fourth trial, and the +series had to be completed on the following day. The total time required +for this series was seventy-eight minutes. + +The work on May 6 was distinctly better, and the animal's behavior +indicated, in a number of trials, definite recognition of the right +door. He might, for example, make a number of incorrect choices, then +pause for a few seconds to look steadily at the doors, and having +apparently found some cue, run directly to the right box. No aid from +the experimenter was needed in this series. + +On the following day improvement continued and the animal's method of +choosing became definite and fairly precise. He was deliberate, quiet, +and extremely business-like. The time for the series was thirty-one +minutes. + +The period of punishment was increased on May 12 to thirty seconds. +Previously, for the greater number of the trials, it had been ten to +fifteen seconds. This increase apparently did not disturb the monkey, +for he continued to work perfectly throughout the series, although +making many mistakes in spite of deliberate choices and the refusal of +certain boxes in each trial. + +An interesting and significant incident occurred on May 13 when at the +conclusion of trial 5, Doctor Hamilton came into the experiment room for +a few minutes. Sobke immediately stopped working, and he could not be +induced to make any choices until Doctor Hamilton had left the room. +This well indicates his sensitiveness to his surroundings, and his +inclination to timidity or nervousness even in the presence of +conditions not in themselves startling. + +Work was continued thus steadily until May 28 when, because of the +failure of the animal to improve, it seemed wise to increase the period +of confinement as punishment to sixty seconds. In the meantime, it had +sometimes been evident that Sobke was near to the solution of his +problem. He would often make correct choices in three or four trials in +succession and then apparently lose his cue and fail utterly for a +number of trials. + +After June 1, in order to hasten the solution of the problem, two series +per day were given. In some instances the second series was given almost +immediately after the first, while in others an interval of an hour or +more intervened. It was further found desirable to give Sobke all of his +food in the apparatus. When the rewards obtained in the several trials +did not satisfy his hunger, additional food was presented, on the +completion of the series of experiments, in one or more of the food +cups. On days marked by unwillingness or refusal to work, very little +food was given. Thus, the eagerness of the monkey to locate the right +box was increased and, as a matter of observation, his deliberateness +and care in choice increased correspondingly. Sixty seconds punishment +was found satisfactory, and it was therefore continued throughout the +work on this problem. + +It was evident, on June 9, from the behavior of the monkey as well as +from the score, that the perfect solution of the problem was near at +hand. This fact the experimenter recorded in his daily notes, and sure +enough, on the following day Sobke chose correctly throughout the series +of ten trials. The time for this series was only ten minutes. The +choices were made deliberately and readily. + +An analysis of the data of table 5 reveals five methods or reactive +tendencies which appeared more or less definitely in the following +order: (a) Choice of first box at the left, because of experience in +problem 1. This tendency was very quickly suppressed by the requirements +in connection with problem 2. Indeed one of the most significant +differences which I have discovered between the behavior of the primates +and that of other mammals is the time required for the suppression of +such an acquired tendency. The monkey seems to learn almost immediately +that it is not worth while to persist in a tendency which although +previously profitable no longer yields satisfaction, whereas in the +crow, pig, rat, and ring dove, the unprofitable mode of response tends +to persist during a relatively large number of trials. (b) The tendency +to choose, first, a box near the left end of the group, to go from that +to the box at the extreme right end of the group, thence to the one next +in order, which was, of course, the right box. This tendency appears +fairly clearly from May 7th on. (c) The box at the extreme right was +first chosen and then the one next to it. For example, in setting 2, box +4 would be chosen first, then box 3. Or, if this did not occur, the +method previously described under (b) was likely to be employed, as for +example, in setting 8, where such choices as 7.6.5.1.8 appear. (d) In +certain series there appeared a marked preference for a particular box, +usually box 3 (see results for May 24). This was doubtless due in a +measure, if not wholly, to the fact that box 3 was the right box twice +in each series of ten settings. But it should be added that the same is +true of box 7, for which no preference was manifested at any time. (e) +Direct choice of the right box. + +The five reactive methods or tendencies enumerated above roughly +appeared in the order named, but there were certain irregularities and +the order as well as the time of appearance varied somewhat from setting +to setting. In general, method c was the most frequently used prior to +the development of method e, the direct choice of the right box. + + + +TABLE 5 + +Results for Sobke, _P. rhesus_, in Problem 2 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | 1.2.3.4.5 | | | R | W | R | W | of + | trials | 7.8.9 | 1.2.3.4 | 2.3.4.5.6.7 | 1.2.3.4.5.6 | 4.5.6.7.8 | 1.2.3 | 2.3.4.5 | 6.7.8.9 | 1.2.3.4 | 3.4.5.6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + May | | {7.7.9.7.7 | {1.2.4.1 | {3.2.7.2 | {4.6.1.6 | | {3.1.3.3 | | | {4.1.4.1 | {3.8.3.3 | | | | | + 3 | 1-10 | {9.7.9.7.9 | {1.4.1.1 | {7.7.7.5 | {1.6.1.1 | 5.8.6.7 | {3.3.1.1 | 3.5.4 | 9.1.8 | {4.1.4.2 | {3.8.6.3 | 0 |10 | 0 |10 | 0:10.00 + | | {7.9.9.7.8* | {4.3* | {2.7.6* | {1.3.5* | | {1.1.2* | | | {1.4.3* | {8.3.7* | | | | | + | | | | | | | | | | | | | | | | + | | | | {4.7.2.7 | | (8.8.4.8 | | {5.5.5.5 | {9.5.5.9 | | | | | | | +4 and 5 | 11-20 | (7.9.7.9.9 | 1.4.1.3 | {2.7.3.2 | 1.6.5 | {8.8.4.8 | {3.3.1.1.3 | {5.5.5.3 | {7.1.6.6 | {4.4.4.4 | {8.8.6.8 | 0 |10 | 0 |10 | 0:10.00 + | | {9.7.7.9.8 | | {7.2.6* | | {4.8.7* | {3.3.1.2 | {5.5.4* | {6.5.8* | {4.4.4.3 | {8.7 | | | | | + | | | | | | | | | | | | | | | | + 6 | 21-30 | 9.7.9.7.8 | 4.3 | 7.2.3.7.6 | {6.3.1.6 | 6.8.7 | 3.1.2 | {5.3.5.3 | {6.9.4.6.1 | {4.1.2.4 | {3.4.5.3 | 0 |10 | 0 |10 | 0:10.00 + | | | | | {6.2.6.5 | | | {2.4 | {7.9.7.8 | {4.2.3 | {8.6.7 | | | | | + | | | | | | | | | | | | | | | | + 7 | 31-40 | 7.9.7.8 | 1.4.3 | 2.7.6 | 3.5 | 4.8.7 | 3.1.2 | 3.2.3.5.4 | 8 | 4.3 | 5.8.3.4.8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + 8 | 41-50 | 7.9.7.8 | (4.2.4.1.4 | 6 | 5 | 6.5.4.8.7 | {3.1.3.1 | 5.3.5.4 | {7.4.2.1 | {4.2.4.1 | 5.3.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | {4.2.2.4.3 | | | | {3.1.3.2 | | {9.8 | {4.3 | | | | | | + | | | | | | | | {5.3.5.3 | | | | | | | | + 10 | 51-60 | 7.7.8 | 3 | 7.3.2.7.6 | 6.4.6.5 | (6.4.8.5 | 3.1.3.2 | {2.5.3.5 | 5.9.8 | 4.2.4.3 | {6.5.4 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | {4.8.7 | | {2.5.4 | | | {3.8.7 | | | | | + | | | | | | | | | | | | | | | | + 11 | 61-70 | 7.9.7.8 | 1.4.3 | 4.3.2.7.6 | 6.5 | {5.4.8.6 | 3.2 | 5.4 | 6.5.2.3.1.8 | 3 | 6.5.3.8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | {5.4.8.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + 12 | 71-80 | 7.9.8 | 3 | 7.3.2.7.6 | 6.5 | 5.4.8.7 | 1.2 | 5.4 | 8 | 4.3 | 5.4.3.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + 13 | 81-90 | 7.8 | 4.3 | 3.7.6 | 6.5 | 8.7 | 1.3.2 | 2.5.2.5.4 | 7.6.5.9.8 | 3 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | | | | | | | | | + | | | | | | | | | | {1.2.1.2.2 | | | | | | + 14 | 91-100 | 7.8 | 3 | 6 | 5 | 6.5.4.7 | 1.3.2 | 5.4 | 9.8 | {1.4.2.2.1 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | {4.1.4.3 | | | | | | + | | | | | | | | | | | | | | | | + 15 | 101-110 | 7.8 | 3 | 7.6 | 5 | 5.4.5.7 | 3.2 | 5.4 | 8 | 2.1.3 | 8.8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | | | | | | | | + 17 | 111-120 | 7.8 | 4.3 | 7.6 | {2.1.2.1.2 | 8.7 | 3.2 | 5.4 | 7.6.5.1.8 | 3 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | {1.3.2.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 18 | 121-130 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.6.5.2.8 | 3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | | | | | | | | + | | | | | | | | {5.3.2.5.3 | | | | | | | | + | | | | | | | | {2.5.2.5.3 | | | | | | | | + 19 | 131-140 | 8 | 3 | 3.2.6 | 5 | 7 | 3.2 | {5.5.2.5.5 | 7.6.9.8 | 3 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | {3.2.5.5.3 | | | | | | | | + | | | | | | | | {2.5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | + 20 | 141-150 | 7.8 | 3 | 3.2.7.6 | 6.5 | 5.4.7 | 3.2 | 3.2.5.4 | 6.5.4.3.8 | 3 | 7 | 3 | 7 | 3 | 7 | 1: 2.33 + 21 | 151-160 | 7.8 | 3 | 5.7.5.3.7.6 | 5 | 7 | 3.2 | 5.3.5.2.5.4 | 7.6.5.9.8 | 3 | 6.4.3.8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 22 | 161-170 | 7.8 | 3 | 7.6 | 3.2.6.5 | 7 | 3.2 | {5.2.5.3 | 7.6.5.8 | 3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | {2.5.4 | | | | | | | | + | | | | | | | {3.1.3 | | | | | | | | | + 24 | 171-180 | 8 | 3 | {3.2.7.5 | {3.6.4 | 8.7 | {1.3.3 | {3.5.4 | 8 | {4.4.2.1 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | {7.3.6 | {3.6.5 | | {3.2 | | | {4.3 | | | | | | + | | | | | | | | | | | | | | | | + 25 | 181-190 | 7.9.7.9.8 | 3 | 3.7.6 | 5 | 8.7 | 3.2 | 5.4 | 4.3.8 | 4.3 | 8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + 26 | 191-200 | 8 | 3 | 6 | 5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 5 | 5 | 5 | 5 | 1: 1.00 + 27 | 201-210 | 7.9.8 | 3 | 3.2.7.6 | 5 | 8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + 28 | 211-220 | 8 | 3 | 3.7.6 | 4.3.2.6.5 | 8.7 | 3.2 | 5.4 | 7.6.5.9.8 | 3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + 29 | 221-230 | 7.8 | 3 | 5.4.3.7.6 | 6.5 | 7 | 2 | 3.2.5.4 | 7.6.5.8 | 3 | 3.8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + 31 | 231-240 | 7.7.8 | 3 | 3.7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 9.8 | 3 | 3.7 | 2 | 8 | 2 | 8 | 1: 4.00 + June | | | | | | | | | | | | | | | | + 1 | 241-250 | 8 | 3 | 5.4.7.6 | 3.2.6.5 | 8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + " | 251-260 | 7.9.8 | 3 | 3.7.6 | 5 | 6.5.4.8.7 | 3.2 | 4 | 5.4.3.8 | {4.2.1.4 | 7 | 4 | 6 | 8 |12 | 1: 1.50 + | | | | | | | | | | {2.4.4.3 | | | | | | + | | | | | | | | | | | | | | | | + 2 | 261-270 | 7.8 | 3 | 6 | 3.2.6.5 | 7 | 3.2 | 3.4 | 8 | 3 | 6.5.3.8.7 | 5 | 5 | | | + " | 271-280 | 7.8 | 3 | 3.7.6 | 3.6.5 | 7 | 3.2 | 5.4 | 7.6.5.4.3.8 | 3 | 7 | 4 | 6 | 9 |11 | 1: 1.22 + 3 | 281-290 | 7.8 | 3 | 7.6 | 3.6.5 | 8.7 | 3.2 | 4 | 7.8 | 3 | 7 | 4 | 6 | | | + " | 291-300 | 9.8 | 3 | 3.6 | 4.3.6.5 | 8.7 | 2 | 3.5.4 | 7.6.5.9.8 | 3 | 8.7 | 3 | 7 | 7 |13 | 1: 1.86 + 4 | 301-310 | 8 | 3 | 7.6 | 3.4.3.6.5 | 8.7 | 2 | 3.2.5.4 | 7.6.5.8 | 3 | 3.8.7 | 4 | 6 | | | + " | 311-320 | 8 | 3 | 5.4.7.6 | 3.2.6.5 | 7 | 2 | 3.2.5.4 | 8 | 3 | 7 | 7 | 3 |11 | 9 | 1: 0.82 + 5 | 321-330 | 8 | 3 | 6 | 4.6.5 | 7 | 2 | 3.5.4 | 8 | 4.3 | 7 | 7 | 3 | | | + " | 331-340 | 8 | 3 | 7.4.7.6 | 3.2.4.6.5 | 7 | 3.2 | 3.5.4 | 8 | 3 | 7 | 6 | 4 |13 | 7 | 1: 0.54 + 7 | 341-350 | 8 | 3 | 7.6 | 5 | 8.7 | 1.3.1.2 | 3.5.4 | 8 | 3 | 7 | 6 | 4 | | | + " | 351-360 | 8 | 3 | 7.6 | 5 | 8.7 | 2 | 3.5.4 | 8 | 3 | 7 | 7 | 3 |13 | 7 | 1: 0.54 + 8 | 361-370 | 7.8 | 3 | 4.7.6 | 3.5 | 8.7 | 2 | 3.4 | 9.8 | 3 | 7 | 4 | 6 | | | + | 371-380 | 8 | 3 | 7.6 | 3.4.4.3.5 | 8.7 | 3.2 | 3.4 | 8 | 3 | 7 | 5 | 5 | 9 |11 | 1: 1.22 + 9 | 381-390 | 8 | 3 | 6 | 4.2.1.5 | 7 | 2 | 3.4 | 8 | 3 | 8.7 | 7 | 3 | | | + " | 391-400 | 8 | 3 | 6 | 5 | 7 | 2 | 3.4 | 8 | 3 | 7 | 9 | 1 |16 | 4 | 1: 0.25 + 10 | 401-410 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 7 |10 | 0 |10 | 0 | 1: 0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 1.2.3.4.5 | | | | | | 1.2.3.4 | 2.3.4.5 | | | | | + | | 5.6.7.8 | 2.3.4.5.6 | 6.7.8.9 | 5.6.7 | 1.2.3.4 | 4.5.6 | 2.3.4.5 | 1.2.3 | 5.6.7 | 6.7.8.9 | | | | | + | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 11 | 1-10 | 6.7 | 3.5 | 8 | 6 | 3 | 5 | 3.4 | 3.2 | 7.7.2.6 | 8 | 5 | 5 | 5 | 5 | 1: 1.00 + 12 | 11-20 | 7 | 3.6.6.2.5 | 8 | 6 | 3 | 4.5 | 4 | 2 | 7.6 | 8 | 7 | 3 | 7 | 3 | 1: 0.43 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +Examination of table 5 indicates that some of the settings proved very +easy for Sobke; others, extremely difficult. Consequently, the number of +methods which were tried and rejected for a given setting varies from +two to five. Setting 2 proved a fairly simple one, and after the +inhibition of the tendency to choose the first box at the left, the only +definite tendency to appear was that of choosing the first box at the +right, and then the one next to it. After one hundred and thirty trials, +this method suddenly gave place to direct choice of the right box, and +during the following twenty-eight series, no error occurred for this +setting. Setting 4, on the contrary, proved extremely difficult, and a +variety of methods is more or less definitely indicated by the records. + +It is needless to lengthen the description by analyzing the data for +each setting, since the reader by carefully scanning the columns of data +in table 5 may observe for himself the various tendencies and their +mutual relations. + +Sobke's curve of learning (figure 19) in problem 2, is extremely +irregular, as was that of Skirrl. Similar irregularities appear in the +daily ratios of right to wrong first choices presented in the last +column of table 5. Most of these irregularities were due, I have +discovered, to unfavorable external conditions. Thus, dark rainy days +and disturbing noises outside the laboratory were obviously conditions +of poor work. + +On the day following the final and correct series for problem 2, a +control series was given. In this Sobke seemed greatly surprised by the +new situations which presented themselves. Repeatedly he exhibited +impulses to enter the box which would have been the correct one in the +regular series of settings. He frequently inhibited such impulses and +chose correctly, but at other times he reacted quickly and made +mistakes. It was evident from his behavior that he was not guided by +anything like a definite idea of the relation of the right box to the +other members of the group. + +In a second control series given on the following day, June 12, +confusion appeared, but less markedly. For the first setting, a correct +choice was made with deliberation. For the second setting, box 3 was +immediately chosen, as should have been the case in the regular series +of settings. Sobke seemed confused when he emerged from this box and had +difficulty in locating the right one. Then followed direct correct +choices for settings 3, 4, and 5. For setting 6, there is recorded a +deliberately made wrong choice, and so on throughout the series, the +choices being characterized by deliberateness and definite search for +the right box. Uncertainty was plainly indicated, and in this the +behavior of the animal differed markedly from that in the concluding +series of the regular experiment. + +It seems safe to conclude from the results of these control series that +Sobke has no free idea of the relation of secondness from the right and +is chiefly dependent upon memory of the particular settings for cues +which lead to correct choice. + + +_Problem 3. Alternately First at Left and First at Right_ + +For four successive days after the last control series in connection +with problem 2, Sobke was merely fed in the apparatus according to +previous description (p. 43). He exhibited a wonderfully keen appetite +and was well fed during this interval between problems. + +The method of experimentation chosen for problem 3 in the light of +previous experience was that of confining the monkey for a short time, +ten to fifteen seconds, in the wrong box, in each of the first ten +mistakes for a given trial, and of then aiding him to find the right box +by the slight and momentary raising of the exit door. Aid proved +necessary in a few of the trials during the first four days. Then he +worked independently. As work progressed it was found possible and also +desirable to increase the period of confinement, and in the end, sixty +seconds proved satisfactory. It was also thought desirable to increase +the number of trials per day from a single series during the early days +to two or even three series from June 29 on. Often three series could be +given in succession without difficulty. During the early trials on this +problem Sobke worked remarkably well, but later his willingness +diminished, evidently because of his failure readily to solve the +problem, and it became extremely difficult to coax him into the +apparatus. On days when he entered only reluctantly and as it seemed +against his will, he was likely to be nervous, erratic, and often slow +in making his choices, but above all he tended to waste time by not +returning to the starting point, preferring rather to loiter in the +alleyways or run back and forth. + + + +TABLE 6 + +Results for Sobke, _P. rhesus_, in Problem 3 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | 3.4.5.6 | 3.4.5.6 | R | W | R | W | of + | trials | 5.6.7 | 5.6.7 | 1.2.3.4.5.6 | 1.2.3.4.5.6 | 4.5.6.7.8 | 4.5.6.7.8 | 2.3.4.5 | 2.3.4.5 | 7.8.9 | 7.8.9 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + June | | | | | {3.1.2.1 | {7.8.7.8 | | | | {9.8.7.9 | | | | | | + 17 | 1--10 | {6.6.7.6 | 5.7 | {4.4.3.5.4 | {4.4.2.1 | {8.8.7.8 | 8 | 2 | 3.2.5 | {8.7.6.9 | 3.8.9 | 2 | 8 | 2 | 8 | 1:4.00 + | | {6.5 | | {5.4.2.1 | {5.4.6* | {7.7.4* | | | | {8.7.3* | | | | | | + | | | | | | | | | | | | | | | | + | | | | {3.4.2.5 | | {8.7.7.5 | | | | | | | | | | + 18 | 11--20 | 6.6.6.5 | 5.7 | {4.5.6.4 | 3.1.4.3.6 | {8.8.7.8 | 8 | 3.2 | (3.4.2.4 | 9.8.8.7.3 | 8.6.9 | 1 | 9 | 1 | 9 | 1:9.00 + | | | | {2.3.1* | | {7.8.4* | | | {4.5 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | {3.6.5.4 | | {8.8.7.7 | | | | | | | | | | + 19 | 21--30 | 6.5 | 7 | {2.5.2.6 | 3.6 | {7.8.8.8 | 8 | 4.3.2 | {3.2.4.2 | {9.8.7.9.7 | 9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | {3.5.1* | | {8.4 | | | {2.5 | {6.5.4.3 | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | (8.8.8.8 | | | | {9.9.8.9 | | | | | | + 21 | 31--40 | 6.5 | 5.6.5.7 | {3.5.4.6 | 2.5.3.6 | {7.8.3.8 | 8 | 4.2 | 2.5 | {9.5.9.9 | 9 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | {4.3.5.1 | | {8.7.4* | | | | {9.9.3* | | | | | | + | | | | | | | | | | | | | | | | + 22 | 41--50 | 7.6.5 | 6.5.5.7 | 1 | 2.1.3.6 | {8.8.8.8 | 8 | 2 | 2.3.2.2.5 | {9.8.9.8.7 | 9 | 4 | 6 | 4 | 6 | 1:1.50 + | | | | | | {7.8.4 | | | | {6.5.9.3 | | | | | | + | | | | | | | | | | | | | | | | + 23 | 51--60 | 5 | 6.5.7 | 1 | {1.2.1.1 | 8.5.4 | 8 | 5.4.2 | 2.4.2.5 | {9.8.4.9 | 9 | 4 | 6 | 4 | 6 | 1:1.50 + | | | | | {3.2.6 | | | | | {7.3 | | | | | | + | | | | | | | | | | | | | | | | + 24 | 61--70 | 7.6.5 | 7 | 2.3.1 | 2.1.5.4.2.6 | 8.7.8.4 | 8 | 4.5.4.3.2 | 2.2.4.5 | 9.7.6.8.3 | 9 | 3 | 7 | 3 | 7 | 1:2.33 + 25 | 71--80 | 6.5 | 5.7 | 3.1 | 6 | 8.5.4 | 8 | 2 | 3.2.5 | 9.8.7.3 | 3.9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | | | | | | + 26 | 81--90 | 7.7.6.5 | 6.5.7 | 3.1 | {1.4.1.1 | 8.4 | 8 | 5.4.2 | 2.5 | 9.8.9.6.3 | 9 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | | {5.1.6 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 91--100 | 7.6.5 | 7 | 1 | 1.2.4.6 | 8.4 | 8 | 2 | 3.2.2.2.5 | 9.8.8.7.9.3 | 9 | 5 | 5 | 5 | 5 | 1:1.00 + | | | | | | | | | | | | | | | | + 29 | 101--110 | 7.6.5 | 5.7 | 1 | {1.1.5.3 | 8.4 | 8 | 2 | 4.2.5 | {9.9.8.9.4 | 9 | 4 | 6 | | | + | | | | | {2.1.6 | | | | | {9.7.6.3 | | | | | | + | | | | | | | | | | | | | | | | + " | 111--120 | 6.5 | 6.5.7 | 1 | 2.1.1.3.6 | 8.5.4 | 8 | 2 | 3.2.5 | 9.8.7.6.4.3 | 9 | 4 | 6 | 8 |12 | 1:1.50 + 30 | 121--130 | 5 | 6.5.6.5.5.7 | 1 | 3.1.6 | 8.7.6.8.5.4 | 8 | 2 | 4.2.4.2.5 | 9.3 | 9 | 5 | 5 | | | + " | 131--140 | 5 | 7 | 1 | 2.3.6 | 8.5.6.4 | 8 | 2 | 5 | 9.8.3 | 3.9 | 6 | 4 |11 | 9 | 1:0.82 + July | | | | | | | | | | | | | | | | + 1 | 141--150 | 5 | 7 | 1 | 1.6 | 8.7.4 | 8 | 2 | 3.2.5 | 9.8.6.9.3 | 9 | 6 | 4 | | | + " | 151--160 | 5 | 7 | 1 | 2.5.3.6 | 8.4 | 8 | 2 | 2.5 | 9.3 | 8.8.7.5.4.9 | 5 | 5 |11 | 9 | 1:0.82 + 2 | 161--170 | 6.5 | 7 | 1 | 2.6 | 8.4 | 8 | 2 | 3.5 | 9.3 | 9 | 5 | 5 | 5 | 5 | 1:1.00 + 3 | 171--180 | 6.5 | 7 | 1 | 1.5.6 | 8.4 | 8 | 2 | 3.5 | 9.3 | 9 | 5 | 5 | | | + " | 181--190 | 5 | 7 | 1 | 4.6 | 8.6.4 | 8 | 2 | 5 | 9.8.4.8.5.3 | 9 | 7 | 3 |12 | 8 | 1:0.67 + 5 | 191--200 | 6.5 | 5.7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 9.5.3 | 9 | 6 | 4 | | | + " | 201--210 | 5 | 7 | 6.1 | 2.6 | 8.6.4 | 8 | 5.3.5.4.3.2 | 4.3.5 | 9.7.3 | 9 | 4 | 6 |10 |10 | 1:1.00 + | | | | | | | | | | | | | | | | + 6 | 211--220 | 5 | 5.7 | 1 | 2.6 | 8.6.4 | 8 | 2 | 4.3.5 | 9.3 | {5.4.8.3 | 4 | 6 | | | + | | | | | | | | | | | {8.5.4.9 | | | | | + | | | | | | | | | | | | | | | | + " | 221--230 | 5 | 7 | 1 | 5.3.6 | 8.6.8.4 | 8 | 4.2 | 3.2.5 | 9.3 | 9 | 5 | 5 | 9 |11 | 1:1.22 + 7 | 231--240 | 5 | 7 | 1 | 2.6 | 8.4 | 7.4.8 | 2 | 4.3.5 | 8.3 | 9 | 5 | 5 | | | + " | 241--250 | 5 | 7 | 2.6.3.5.1 | 6 | 8.4 | 8 | 2 | 5 | 9.3 | 9 | 7 | 3 | | | + | | | | | | | | | | | | | | | | + | | | | {2.6.2.6.4 | | | | | | | | | | | | + " | 251--260 | 5 | 7 | {6.3.2.6 | 6 | 8.4 | 8 | 2 | 5 | 9.5.3 | 9 | 7 | 3 |19 |11 | 1:0.58 + | | | | {5.4.3.1 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 8 | 261--270 | 7.5 | 7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 8.3 | 8.5.4.9 | 5 | 5 | | | + " | 271--280 | 5 | 7 | 2.6.4.6.1 | 6 | 8.5.8.4 | 7.4.8 | 5.5.3.5.2 | 5 | 9.3 | 9 | 5 | 5 |10 |10 | 1:1.00 + | | | | | | | | | | | | | | | | + 9 | 281--290 | 5 | 5.7 | 1 | 6 | 8.4 | 8 | 2 | 2.5 | 8.3 | {7.3.8.6.8 | 5 | 5 | | | + | | | | | | | | | | | {4.7.3.9 | | | | | + | | | | | | | | | | | | | | | | + " | 291--300 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 9.3 | 9 | 8 | 2 | | | + " | 301--310 | 5 | 7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 9.5.3 | 9 | 7 | 3 |20 |10 | 1:0.50 + 10 | 311--320 | 5 | 7 | 1 | 6 | 8.4 | 7.4.8 | 2 | 5 | 9.3 | 9 | 7 | 3 | | | + " | 321--330 | 5 | 7 | 1 | 5.2.6 | 8.7.4 | 8 | 2 | 5 | 9.3 | 9 | 7 | 3 |14 | 6 | 1:0.43 + 12 | 331--340 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 8.3 | 9 | 8 | 2 | | | + " | 341--350 | 5 | 7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 9.3 | 9 | 7 | 3 |15 | 5 | 1:0.33 + 13 | 351--360 | 5 | 5.7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 3 | 9 | 7 | 3 | | | + " | 361--370 | 5 | 7 | 6.1 | 6 | 4 | 8 | 5.2 | 3.2.5 | 9.3 | 9 | 6 | 4 |13 | 7 | 1:0.54 + 14 | 371--380 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 7.4.3.9 | 8 | 2 | | | + " | 381--390 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 9.3 | 4.7.3.9 | 7 | 3 |15 | 5 | 1:0.33 + 15 | 391--400 | 5 | 5.5.7 | 1 | 3.6 | 8.4 | 8 | 3.2 | 5 | 8.3 | 9 | 5 | 5 | | | + " | 401--410 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 7.3 | 6.5.3.9 | 7 | 3 |12 | 8 | 1:0.67 + 16 | 411--420 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 9 | 9 | 1 | | | + " | 421--430 | 5 | 7 | 1 | 6 | 4 | 8 | 2 | 5 | 3 | 4.7.4.9 | 9 | 1 | | | + " | 431--440 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 5.7.3.9 | 8 | 2 |26 | 4 | 1:0.15 + 17 | 441--450 | 5 | 7 | 1 | 6 | 4 | 4.8 | 2 | 5 | 4.3 | 3.5.9 | 7 | 3 | | | + " | 451--460 | 5 | 7 | 1 | 3.6 | 4 | 5.4.8 | 2 | 5 | 9.3 | 9 | 7 | 3 | | | + " | 461--470 | 5 | 7 | 1 | 6 | 4 | 8 | 2 | 5 | 3 | 9 |10 | 0 |24 | 6 | 1:0.25 + 19 | 471--480 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 9 | 9 | 1 | 9 | 1 | 1:0.11 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + | | 5.6 | 5.6 | 4.5.6.7.8.9 | 4.5.6.7.8.9 | 1.2.3.4.5 | 1.2.3.4.5 | 2.3.4.5.6.7 | 2.3.4.5.6.7 | 3.4.5.6.7.8 | 3.4.5.6.7.8 | | | | | + | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 19 | 1--10 | 5 | 6 | 4 | 9 | 1 | 5 | 3.7.2 | 7 | 3 | 8 | 9 | 1 | 9 | 1 | 1:0.11 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +The data of table 6 indicate for this problem only three pronounced +reactive tendencies: (a) As the initial tendency, the choice of the +second box from the right end. This proved surprisingly weak, in view of +the animal's long training on problem 2, and it disappeared quickly. (b) +Choice of the end boxes, and (c) direct choice of the right box. + +For this, as for the other problems, extreme differences in method and +in time and degree of success appear for the different settings. Thus, +while settings 1, 2, 3, 6, 7, and 10 proved to be easy, settings 4, 5, +8, and 9 were evidently more difficult. + +[Illustration: FIGURE 20.--Error curve of learning for the solution of +problem 3 (alternately the first box at the left end and the first at +the right end) by Sobke.] + +From the first this problem promised to be much easier for Sobke than +problem 2, and although the actual number of trials necessary for the +solution is greater by sixty for problem 3 than for problem 2, +comparison of the data of the tables justifies the statement that the +third problem was both easier and more nearly adequately solved than the +second. This is not surprising when the nature of the two problems is +considered, for whereas problem 2 requires choice by perception of the +relationship of secondness from the right end of the group, problem 3 +requires, instead, the choice of the end member of the group each time, +with the additional variation of alternation of ends. Now as it happens, +the end member is easily selected by the monkey, and it appears further +that alternation was relatively easy for Sobke to acquire. Consequently, +the combination of end and alternation proved easier than the choice of +the second from the right end of the group. + +The above statements are supported by comparison of the curves of +learning. The curve for problem 2, figure 19, is extremely irregular; +that for problem 3, figure 20, much more regular. Similarly, the daily +ratios of right to wrong choices as exhibited in tables 5 and 6 indicate +smaller variations for the third problem than for the second. + +Sobke made ten correct first choices in the third series for July 17, +but he was working very uncertainly and it seemed rather a matter of +good luck than good management that he succeeded in presenting this +perfect series: For this reason and also because it did not seem +feasible to have Sunday intervene between the final and perfect regular +series and the control series, an additional regular series was given on +July 19, in which, as the table indicates, a single mistake occurred, in +trial 5. The monkey was working perfectly. The series of trials required +only ten minutes, and it was evident that carelessness and eagerness to +obtain food were chiefly responsible for the mistake. + +The control series given on July 19 immediately after the series just +described resulted similarly in one failure and nine successes. The +choices were made easily and with certainty, and the only mistake, that +of setting 7, was apparently due to carelessness. + +This excellent showing for the control series wholly justifies the +comparison of problems 2 and 3 as to difficultness, made above. Whereas +in both problems 1 and 2 the control trials caused confusion, in the +case of problem 3, they did not essentially alter the behavior of the +animal. The fact seems to be that for this problem the particular +setting is of relatively little importance; while turning alternately to +the extreme left and the extreme right is of prime importance. That +Sobke had the idea of alternation or of the end box, there seems no more +reason for insisting than that he had the idea of secondness from the +right end in problem 2. It is possible, even probable, that these ideas +existed rather vaguely in his consciousness, but there is obviously no +necessity for insisting that the solution of the problems depended upon +them. + + +_Problem 4. Middle_ + +As the available time for the continuation of the experiment was +limited, it was decided to proceed with work on problem 4 immediately +upon the completion of problem 3, and on July 20, the problem of the +middle door was presented to Sobke. Since it was anticipated that this +sudden change would confuse and discourage him greatly, the only form of +punishment administered was the momentary lowering of the entrance door +of the wrong box. As in the previous problem, he was aided after ten +successive wrong choices. As might have been anticipated, he +persistently entered the end boxes of the groups, and this in some +instances probably would have been kept up for many minutes had not the +experimenter lured him into the right box by slightly raising the exit +door. In the first series, he had to be aided in five of the ten trials. +The total time for the series was forty-five minutes, the total number +of choices, eighty-eight. In the second series, he was aided in four of +the trials. The total time required was seventy-two minutes, and the +total number of choices was seventy-six. + +Throughout the first series, Sobke worked hard, but with evidently +increasing dissatisfaction. He clung persistently to his acquired +tendency to choose the end boxes, and after each trial he returned less +willingly to the starting point. Up to this time his attitude toward the +experimenter had been perfectly friendly, if not wholly trustful. But +when on July 21 he was brought into the apparatus for the second series, +he exhibited a wholly new form of behavior, for instead of attending +diligently to the open doors and devoting his energies to trying to find +the right box, he instead, after gazing at them for a few seconds, +turned toward the experimenter and jumped for him savagely, throwing +himself against the wire netting with great force. This was repeated a +number of times during the first two or three trials, and it occurred +less frequently later in the series. Since nothing unusual had happened +outside of the experiment room, the suggested explanation of this sudden +change in attitude and behavior is that the monkey resented and blamed +on the experimenter the difficulty which he was having in obtaining +food. + +From this time on until the end of my work, Sobke was always savage and +both in and out of the apparatus he was constantly on the watch for an +opportunity to spring upon me. Previously, it had been possible for me +to coax him into the apparatus by offering him food and to return him to +his cage by walking after him. But on and after the twenty-first of +July, it was impossible for me to approach him without extreme risk of +being bitten. + +Doctor Hamilton when told of this behavior, reported that several times +monkeys have shown resentment toward him when they were having trouble +in the experiment. I therefore feel fairly confident that I have not +misinterpreted Sobke's behavior. When on July 22 I gave Sobke an +opportunity to enter the apparatus, he refused, and it was impossible to +lure him in with food. Two hours later, having waited meantime for his +breakfast, he entered readily and worked steadily and persistently +through his third series of trials, but in no one of these trials did he +choose correctly. Neither on this day nor the following did he exhibit +resentment while at work. He apparently had regained his affective poise +and was able to attend as formerly to the task of locating his rewards. + +During these first three series, although the ratio of right to wrong +choices stood 0 to 10, there occurred a marked reduction in the number +of trials in which aid was necessary as well as in the total number of +choices, and on July 23 correct reactions began to appear. Improvement +during the next hundred trials was steady and fairly rapid, and on July +31, a record of seven right to three wrong trials was obtained. This was +surprising to the experimenter, as well as gratifying, since he was +eager to have the animal complete this problem before work should have +to be discontinued. + +Everything went smoothly until August 2, when my assistant, who had been +left in charge of the experimental work for a week, attempted to +increase the number of trials per day to two series. Sobke apparently +was not quite ready for this increase in the amount of his day's labor +and refused to work at the end of the first series. In this series he +did less well than on the previous day. The following day, August 3, +unfortunately and contrary to the wishes of the experimenter, the +laboratory was painted and there was necessarily considerable +disturbance because of the presence of the workmen, and in addition, the +pervasive odor of fresh paint. Sobke chose still less successfully on +this date, and on August 4, he refused to work after the eighth trial. +It is true that during these bad days the total number of choices +steadily diminished while the successes, also, diminished, or at best, +failed to increase. When on August 9, I returned to the laboratory to +take charge, I found that Sobke was no longer trying to solve the +problem as when I had gone away. His attitude had changed in that he had +become indifferent, careless, and obviously discouraged with his task. + + + +TABLE 7 + +Results for Sobke, _P. rhesus_, in Problem 4 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | 1.2.3.4 | | | 1.2.3.4.5 | | | 3.4.5.6 | | R | W | R | W | of + | trials | 2.3.4 | 5.6.7.8.9 | 5.6.7 | 7.8.9 | 4.5.6.7.8 | 6.7.8.9 | 1.2.3 | 2.3.4.5.6 | 7.8.9 | 6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + July | | | {5.9.5.5 | {1.7.1.3 | {9.7.9.7 | | {1.9.3.1 | | {6.3.2.6 | | | | | | | + 20 | 1- 10 | 2.4.2.4.3 | {5.9.5.6 | {1.7.1.7 | {7.9.7.9 | {8.4.8.4 | {9.2.9.3 | 3.1.3.2 | {3.6.3.2 | {9.3.4.3 | {8.6.6.8.6 | 0 |10 | 0 |10 | 0:10.00 + | | | {5.8.7* | {1.7.4* | {7.7.8 | {4.6 | {9.1.5* | | {6.3.4* | {3.9.3.6 | {8.6.8.6.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | {7.9.7.7 | {4.8.5.5 | {1.4.3.2 | | | {3.9.3.8 | | | | | | + 21 | 11- 20 | 2.3 | {5.6.5.5 | {1.2.7.1 | {7.9.7.7 | {8.4.8.4 | {8.9.1.9 | 3.1.2 | {6.2.3.2.6 | {4.3.3.5 | 6.7 | 0 |10 | 0 |10 | 0:10.00 + | | | {9.5.5.7 | {7.3.7.4 | {9.7.8* | {5.4.6* | {1.9.5* | | {3.5.2.4 | {3.4.6* | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | {3.7.4.8 | | | | | | + 22 | 21- 30 | 2.3 | 5.6.5.6.7 | 1.7.4 | {7.9.7 | 4.7.4.6 | {1.4.6.3 | 3.1.2 | 5.2.6.4 | {4.3.5.8 | 6.6.7 | 0 |10 | 0 |10 | 0:10.00 + | | | | | {7.7.8 | | {2.7.5 | | | {3.7.6* | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | {5.4.7.4 | | | | | | + 23 | 31- 40 | 2.4.3 | 5.6.8.7 | 1.7.4 | {7.7.7.7 | 4.7.6 | 2.7.5 | 3.1.2 | 6.4 | {7.5.4.3 | 7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | {7.7.8 | | | | | {7.3.6 | | | | | | + | | | | | | | | | | | | | | | | + 24 | 41- 50 | 3 | 5.6.7 | 1.6.4 | 7.7.7.8 | 4.7.6 | {2.7.6.4 | 3.2 | 6.5.4 | 5.3.8.6.6 | 7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | {2.7.3.8 | | | | | | | | | + | | | | | | | {9.6.5* | | | | | | | | | + | | | | | | | | | | | | | | | | + 26 | 51- 60 | 4.3 | 6.5.7 | 2.7.4 | 7.8 | 6 | {6.4.2.7 | 3.2 | {6.5.3.5.2 | 7.6 | 7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | {4.8.6.5 | | {6.5.6.4 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | {4.7.3.7 | | | | | | | | | + 27 | 61- 70 | 3 | 6.5.7 | 2.5.4 | 7.7.8 | 5.7.6 | {4.6.1.4 | 2 | 6.5.4 | 5.7.6 | 6.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | {7.3.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 71- 80 | 3 | 7 | 6.5.4 | 7.8 | 5.4.7.6 | 2.7.6.5 | 2 | 5.5.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 29 | 81- 90 | 3 | 6.5.7 | 2.4 | 7.7.8 | 5.4.6 | {2.7.7.6 | 2 | 4 | 5.4.7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | {2.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 30 | 91-100 | 3 | 7 | 2.6.5.4 | 7.8 | 6 | 5 | 2 | 5.4 | 5.4.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 31 | 101-110 | 3 | 7 | 2.4 | 7.8 | 6 | 5 | 2 | 4 | 7.6 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + August | | | | | | | | | | | | | | | | + 2 | 111-120 | 3 | 7 | 6.5.7.6.4 | 7.8 | 6 | 4.2.7.6.5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 3 | 121-130 | 3 | 6.5.7 | 7.6.5.4 | 7.8 | 7.6 | 5 | 2 | 6.5.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 4 | 131-140 | 3 | 7 | 6.5.7.6.4 | 7.8 | 6 | {2.7.6.4 | 2 | 6.4 | 3.5.4.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + | | | | | | | {8.7.6.5 | | | | | | | | | + | | {2.4.4.4 | | | | | | | | | | | | | | + 5 | 141-150 | {2.4.4.2 | 6.5.7 | {2.7.6.7 | 8 | 7.6 | {2.8.7.6 | 3.2 | 6.4 | 7.6 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | {4.3* | | {5.4 | | | {8.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 6 | 151-160 | 2.4.4.3 | 7 | 2.6.5.4 | 7.8 | 7.6 | 7.6.5 | 2 | 6.4 | 6 | 7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + | | {4.4.2.4 | | | | | | | | | | | | | | + " | 161-170 | {4.2.4.2 | 7 | 6.5.4 | 7.8 | 7.6 | 7.6.5 | 3.2 | 5.4 | 7.6 | 7 | 2 | 8 | 6 |14 | 1: 2.33 + | | {4.4.3 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 7 | 171-180 | 4.3 | 7 | 6.5.4 | 8 | 7.6 | 5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | | | + | | | | | | | | | | | | | | | | + " | 181-190 | {4.2.4.4 | 7 | 7.6.5.4 | 7.8 | 6 | 6.5 | 2 | 6.5.4 | 7.6 | 7 | 4 | 6 | 9 |11 | 1: 1.22 + | | {2.4.3 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 9 | 191-200 | 3 | 7 | 5.4 | 8 | 8.7.6 | 6.5 | 2 | 6.5.4 | 7.6 | 8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 10 | 201-210 | 3 | 7 | 2.5.4 | 7.8 | 7.6 | {2.8.7.6 | 2 | 6.5.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | {8.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 11 | 211-220 | 3 | 7 | 6.5.4 | 7.8 | 6 | {7.6.4.3 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + | | | | | | | {2.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 12 | 221-230 | 3 | 7 | 2.4 | 7.8 | 6 | 7.6.5 | 2 | 6.5.4 | 8.7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 19 | 231-240 | 3 | 7 | 2.4 | 7.8 | 6 | 5 | 2 | 6.4 | 8.7.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | | | | | | + 20 | 241-250 | 3 | 7 | 5.4 | 8 | 7.6 | {2.4.1.2.7 | 3.2 | 6.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | {8.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 21 | 251-260 | 3 | 7 | 6.5.4 | 7.8 | {7.4.5.4 | {6.4.3.2 | 2 | 6.5.4 | 8.7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | {8.7.6 | {7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 23 | 261-270 | 3 | 7 | 6.5.4 | 7.8 | 6 | 6.5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 24 | 271-280 | 3 | 7 | 6.4 | 7.8 | 7.6 | 2.5 | 2 | 4 | 7.4.3.8.7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 25 | 281-290 | 3 | 7 | 2.5.4 | 8 | 7.6 | 5 | 2 | 6.4 | 7.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 26 | 291-300 | 3 | 7 | 6.5.4 | 8 | 7.6 | 7.6.5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 27 | 301-310 | 3 | 7 | 2.6.5.4 | 8 | 7.6 | 5 | 2 | 6.5.4 | 7.5.4.9.8.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 28 | 311-320 | 3 | 7 | 2.5.4 | 8 | 6 | 9.8.7.5 | 2 | 3.4 | 8.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +I immediately set about reinstating the former attitude by lessening the +number of trials and the punishment, and by increasing the value of the +reward, but my best efforts, continuing up to August 28, failed markedly +to improve the condition. The number of correct choices did somewhat +increase, but at no time did the animal attain the degree of success +which he had achieved as early as July 31 in the eleventh series of +trials. + +During the last two weeks of experimentation, all possible efforts were +put forth to discover the best combination of rewards and punishments. +Punishment was varied from 0 to confinement of sixty seconds, and many +kinds of food in different amounts were tried as rewards, but in spite +of everything Sobke failed to improve markedly. From time to time, +notably on August 12 and 21, he exhibited peculiarly strong resentment +toward me and repeatedly attempted to attack me. + +The outcome of my experiments with problem 4 is peculiarly interesting +in that it indicates the importance of a favorable attitude toward the +work and the extreme risk from disturbing or discouraging conditions. It +seems not improbable that had the work progressed without change in +experimenter, or method of procedure, and above all without the +disturbance of the painting, Sobke might have solved problem 4 within a +few days. This is by no means certain, however, for in problems 2 and 3 +the ratio of right to wrong choices instead of increasing steadily +increased very irregularly. + +The detailed results for this problem are given in table 7. Reactive +tendencies which appear are: (a) persistent choice of the end boxes +followed, subsequently, by (b) the tendency to locate the middle box +directly. This proved fairly easy when the number of boxes involved was +only three as in settings 1, 4, 7, and 10. Setting 4 was most difficult +of all, because box 9 was avoided or ignored. When the number of open +boxes was as great as five, as in settings 2 and 8, the task was +obviously more difficult, but whereas success in setting 2 appeared +early, in setting 8 it failed to appear during the course of +experimentation. For the settings 3, 6, and 9, involving either seven or +nine open boxes, the direct choice of the middle box was next to +impossible, and Sobke tended to choose, first of all, a particular box +toward one end of the series, for example, box 2, in setting 3, and box +7 in setting 9. To the experimenter, as he watched the animal's +behavior, it looked as though effort each time were being made to locate +the middle member of the group. This appeared relatively easy for groups +of three boxes, extremely difficult for as many as five boxes, and +almost impossible for seven or nine. + + +3. Julius, _Pongo pygmaeus_ + +_Problem 1. First at the Left End_ + +The orang utan, Julius, was gentle, docile, and friendly with the +experimenter throughout the period of investigation. He at no time +showed inclination to bite and could be handled safely. As contrasted +with Skirrl and even with Sobke, he adapted himself to the +multiple-choice apparatus very promptly, and only slight effort on the +part of the observer was necessary to prepare him, by preliminary +trials, for the regular experiments. But in order to facilitate work, he +was familiarized with the apparatus by means of regular route training +and feeding in the several boxes from April 5 to April 9. + +On April 10 the apparatus was painted white as has been stated +previously, and on the following Monday, April 12, Julius when again +introduced to it gave no indications of fear, uneasiness, or dislike, +but worked as formerly, making his round trips quickly and eagerly +entering any box which happened to be open, in order to obtain the +reward of food. + +The regular experimentation was undertaken on April 13, and the results +of the first series of trials with Julius are sharply contrasted with +those obtained with the monkeys in that fewer choices were necessary. +Instead of the expected ratio of right to wrong first choices, 1 to 2.5, +the orang utan gave a ratio of 1 to 1. An additional markedly different +result from that obtained with the monkeys is indicated below in the +total time required for a series of trials. As examples, the data for +the first, second, fifth, and tenth series are presented. + + + +TIME FOR SERIES OF TRIALS + + 1st series 2nd series 5th series 10th series +Skirrl 35 min. 20 min. 14 min. 10 min. +Sobke 14 " 17 " 10 " 9 " (8th series) +Julius 12 " 11 " 14 " 9 " + + + +It is also noteworthy that Julius in the presence of visitors or under +other unusual conditions worked steadily and well, whereas the monkeys, +and especially Sobke, tended to be distracted and often refused to work +at all. + +Almost from the beginning of his work on problem l, Julius began to +develop the tendency to enter immediately the open door nearest the +starting point. In case the group of open doors lay to the right of the +middle of the apparatus, this method naturally yielded success; whereas +if the group included doors to the left of the middle, it resulted in +failure. Obviously it was a most unsatisfactory method, and although it +enabled him to make more right than wrong first choices, it prevented +him from increasing the number of right choices, and as table 1 +indicates, it maintained the ratio of 1 right to .67 wrong first choices +for eight successive days. + +On April 23 a break occurred in which the number of correct choices was +reduced from six to five. Julius worked very rapidly and with almost no +hesitation in choosing. My notes record "he seems to miss the point +wholly. It is doubtful whether the punishment is sufficiently severe." +At this time he was being punished by thirty seconds confinement in each +wrong box, the interval having been held fairly steadily from the first +series of experiments. On April 26 it was increased to sixty seconds, in +an effort to break him of the habit of choosing the "nearest" door. But +he became extremely restless under the longer confinement and tried his +best to raise the entrance and exit doors. Since there was at this time +no mechanism for locking them when closed, it was difficult for the +experimenter to prevent him from escaping by way of the entrance door or +from raising the exit door sufficiently to obtain the food. Indeed, the +longer confinement worked so unsatisfactorily that on the following day +I substituted for it the punishment of forcing him to raise the entrance +door of the wrong box in order to escape for a new choice. He was +rewarded with food in the alleyway H, beside door 15 (figure 17), only +when he chose correctly on first attempt. + +This method discouraged him extremely and proved wasteful of time. +Consequently, in a second series on the same date return was made to the +former method, and he was rewarded with food whenever he found the right +box. But on April 28, the two methods were again employed, the first in +the initial series and the second in a final series of trials. The +animal's persistent attempts to raise the doors gave the experimenter so +much trouble that on April 29 barbed wire was nailed over the windows of +the entrance doors with the hope that it might prevent him from working +at them. But he quickly learned to place his fingers between the barbs +and raise the doors as effectively as ever. + +On April 30 the reward of food was given only when the first choice was +that of the right box and in that event it was placed in the alleyway H +as stated above. + +As it seemed absolutely essential to break the unprofitable habit of +choosing the nearest door, on May 3 a new series of settings was +presented, in which only the doors to the left of the middle of the row +of nine boxes were used as right doors. That is, in this new series, +doors 1 to 4 occur as right doors; 5 to 9 do not. As punishment for +wrong choices on this date, Julius was confined in the wrong box from +one to five minutes. It was difficult to keep him in, but by means of +cords which had been attached to the doors, this was successfully +accomplished. Yet another and slightly different series of settings was +employed on May 4, and this, proving satisfactory, was continued in use +until the end of the experiment, with punishment ranging from sixty to +one hundred and twenty seconds for each mistake. + +Naturally the modification of settings introduced May 3 greatly +increased the proportion of wrong first choices. Indeed, as appears in +table 8, the ratio of right to wrong immediately changed from 1:0.67 to +1:4.00. Between May 3 and May 10, no steady and consistent improvement +in method or in the number of correct first choices occurred, and on the +last named date, Julius chose correctly only three times in his ten +trials. At this time there was, as my notes record, no satisfactory +indication of progress, and the status of the experiment seemed +extremely unsatisfactory in as much as in spite of the experimenter's +best efforts to break up the habit of choosing the nearest door, the +orang utan still persisted, to a considerable extent, in the use of this +method. The only encouraging feature of the results was an evident +tendency to choose somewhat nearer the left end of a group than +previously. + + + + +TABLE 8 + +Results for Orang utan in Problem 1 + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | | | R | W | R | W | of + | trials | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + April | | | | | | | | | | | | | | | | + 13 | 1- 10 | 3.1 | 8 | 4.3 | 7 | 4.2 | 7.6 | 5 | 4 | 7 | 3.1 | 5 | 5 | 5 | 5 | 1:1.00 + 14 | 11- 20 | 3.2.1 | 8 | 4.3 | 7 | 4.4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 15 | 21- 30 | 3.2.1 | 8 | 4.3 | 7 | 4.5.5.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 16 | 31- 40 | 3.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | 6 | 4 | 1:0.67 + 17 | 41- 50 | 3.2.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 19 | 51- 60 | 3.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 20 | 61- 70 | 2.1 | 8 | 4.3 | 7 | 5.3.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 21 | 71- 80 | 3.1 | 8 | 4.3 | 7 | 5.4.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | 6 | 4 | 1:0.67 + 22 | 81- 90 | 3.1 | 8 | 5.3 | 7 | 6.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | 6 | 4 | 1:0.67 + 23 | 91-100 | 3.2.1 | 8 | 5.3 | 7 | 4.3.2 | 6 | 5 | 5.4 | 7 | 3.2.1 | 5 | 5 | 5 | 5 | 1:1.00 + 24 | 101-110 | 3.2.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 26 | 111-120 | 3.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 5.4 | 7 | 3.1 | 5 | 5 | 5 | 5 | 1:1.00 + 27 | 121-130 | 3.2.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 6.5 | 5.8.6.4 | 7 | 3.3.3.1 | 4 | 6 | | | + " | 131-140 | 3.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 |10 |10 | 1:1.00 + 28 | 141-150 | 3.2.1 | 8 | 3 | 7 | 5.4.2 | 6 | 5 | 4 | 7 | 3.1 | 7 | 3 | | | + " | 151-160 | 3.1 | 8 | 3 | 7 | 3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 7 | 3 |14 | 6 | 1:0.43 + 29 | 161-170 | 3.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | | | + " | 171-180 | 3.2.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 |12 | 8 | 1:0.67 + | | | | | | | | | | | | | | | | + 30 | 181-190 | 3.1 | 8 | 4.3 | 7 | {4.5.6.4 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | | | + | | | | | | {5.6.4.2 | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 191-200 | 3.1 | 8 | 4.5.6.7.3 | 7 | 4.5.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 |12 | 8 | 1:0.67 + May | | | | | | | | | | | | | | | | + 1 | 201-210 | 3.1 | 8 | 4.3 | 7 | 3.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | | | + " | 211-220 | 3.2.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 |12 | 8 | 1:0.67 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 2.3.4.5 | | | | | | | 2.3.4.5 | | | | | + | | 1.2.3 | 3.4.5.6.7 | 6.7.8 | 1.2.3 | 3.4.5.6.7 | 4.5.6.7.8.9 | 2.3.4.5 | 1.2.3 | 4.5.6.7.8.9 | 6.7.8.9 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 3 | 221-230 | 3.1 | 4.3 | 4.2 | 3.1 | 4.3 | 4 | 4.3.2 | 3.1 | 4 | 4.3.2 | 2 | 8 | 2 | 8 | 1:4.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 2.3.4.5 | 4.5.6.7 | | | | | 2.3.4.5 | | | | | | + | | 1.2.3 | 3.4.5.6.7 | 6.7.8 | 8.9 | 2.3.4.5 | 3.4.5.6 | 1.2.3 | 4.5.6.7.8 | 6.7.8.9 | 1.2.3 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 4 | 231-240 | 3.2.1 | 4.3 | 4.2 | 4 | 4.3.2 | 4.3 | 3.2.1 | 4 | 3.2 | 3.2.1 | 2 | 8 | 2 | 8 | 1:4.00 + 5 | 241-250 | 2.1 | 3 | 3.2 | 4 | 3.2 | 4.3 | 3.2.1 | 4 | 3.2 | 3.2.1 | 3 | 7 | 3 | 7 | 1:2.33 + 6 | 251-260 | 2.1 | 3 | 2 | 4 | 3.2 | 3 | 2.1 | 4 | 3.2 | 2.1 | 5 | 5 | 5 | 5 | 1:1.00 + 7 | 261-270 | 2.1 | 3 | 3.2 | 4 | 3.2 | 3 | 2.1 | 4 | 4.2 | 2.1 | 4 | 6 | 4 | 6 | 1:1.50 + 8 | 271-280 | 2.1 | 4.3 | 4.3.2 | 4 | 3.2 | 4.3 | 3.1 | 4 | 3.2 | 2.1 | 2 | 8 | 2 | 8 | 1:4.00 + 10 | 281-290 | 1 | 4.3 | 4.2 | 4 | 3.2 | 4.3 | 2.1 | 4 | 3.2 | 2.1 | 3 | 7 | 3 | 7 | 1:2.33 + 11 | 291-300 | 1 | 3 | 2 | 4 | 2 | 3 | 1 | 4 | 2 | 1 |10 | 0 |10 | 0 | 1:0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + | | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 12 | 301-310 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 |10 | 0 |10 | 0 | 1:0.00 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + + + +A series of correct first choices was obtained on May 11, greatly to the +surprise of the experimenter, for no indication had previously appeared +of this approaching solution of the problem. It seemed possible, +however, that the successes were accidental, and it was anticipated that +in a control series Julius would again make mistakes. But on the +following day, May 12, the presentation of the original series of ten +settings, which, of course, differed radically from the settings used +from May 4 to May 11 was responded to promptly, readily, and without a +single mistake. Julius had solved his problem suddenly and, in all +probability, ideationally. + +Only three reactive tendencies or methods appeared during Julius's work +on this problem: (a) choice of the open door nearest to the starting +point (sometimes the adjacent boxes were entered); (b) a tendency to +avoid the "nearest" door and select instead one further toward the left +end of the group; (c) direct choice of the first door on the left. + +The curve of learning plotted from the daily wrong choices and presented +in figure 18, had it been obtained with a human subject, would +undoubtedly be described as an ideational, and possibly even as a +rational curve; for its sudden drop from near the maximum to the base +line strongly suggests, if it does not actually prove, insight. + +Never before has a curve of learning like this been obtained from an +infrahuman animal. I feel wholly justified in concluding from the +evidences at hand, which have been presented as adequately as is +possible without going into minutely detailed description, that the +orang utan solved this simple problem ideationally. As a matter of fact, +for the solution he required about four times the number of trials which +Sobke required and twice as many as were necessary for Skirrl. Were we +to measure the intelligence of these three animals by the number of +trials needed in problem 1, Sobke clearly would rank first, Skirrl +second, and Julius last of all. But other facts clearly indicate that +Julius is far superior to the monkeys in intelligence. We therefore must +conclude that _where very different methods of learning appear, the +number of trials is not a safe criterion of intelligence._ The +importance of this conclusion for comparative and genetic psychology +needs no emphasis. + + +_Problem 2. Second from the Right End_ + +Julius was given four days' rest before being presented with problem 2. +He was occasionally fed in the apparatus, but regular continuation of +training was not necessary to keep him in good form. During this rest +interval, locks were attached to the doors of the apparatus so that the +experimenter by moving a lever directly in front of him could fasten +either one or both of the doors of a given box by a single movement. On +May 13 Julius was given opportunity to obtain food from each of the +boxes in turn, and trial of the locks was made in order to familiarize +him with the new situation. He very quickly discovered that the doors +could not be raised when closed, and after two days of preliminary work, +he practically abandoned his formerly persistent efforts to open them. +The locks worked satisfactorily from a mechanical point of view as well +as from that of the adaptation of the animal to the modified situation. + +Problem 2 was regularly presented for the first time on May 17, on which +day a single series was given. The period of punishment adopted was +twenty seconds, and for each successful choice a small piece of banana +was given as a reward. After the first trial in this series, in which +Julius repeatedly entered the first box at the left, that is box 7, +there was but slight tendency to reënter the first box at the left of +the group. Instead, Julius developed the method of moving box by box +toward the right end of the group. The choices were made promptly, and +their systematic character enabled the animal to obtain his reward +fairly quickly, in spite of the large number of mistakes. + +In the second series, the orang utan developed the interesting trick of +quickly dodging out of the wrong box before the experimenter could lower +the door behind him. This he did only after having been punished for +many wrong choices to the point of discouragement. The trick was easily +broken up by the sudden lowering of the entrance door as soon as he had +passed under it. + +There appeared on May 21 an unfavorable physical condition which +manifested itself, first of all through the eyes which appeared dull and +bloodshot. On the following day they were inflamed and the lids nearly +closed. Julius refused to eat, and experimentation was impossible. Until +June 2 careful treatment and regulation of diet was necessary. He passed +through what at the time seemed a rather startling condition, but +rapidly regained his usual good health, and on June 3, although somewhat +weak and listless, he again worked fairly steadily. + +Since it was now possible to lock the doors and confine the animal for +any desired period, on June 5 the interval of punishment was made sixty +seconds, and a liberal quantity of banana, beet, or carrot was offered +as reward. No increase in the number of successful choices appeared, and +Julius showed discouragement. Sawdust had been strewn on the floor, and +in the intervals between trials as well as during confinement in wrong +boxes, he took to playing with the sawdust. He would take it up in one +hand and pour it from hand to hand until all had slipped through his +fingers, then he would scrape together another handful and go through +the same process. Often he became so intent on this form of amusement +that even when the exit door was raised, he would not immediately go to +get the food. + +The reactive tendencies which appeared in the work on problem 2 will now +be presented in order, since I shall have to refer to them repeatedly, +and the list will be more useful to the reader at this point than at the +conclusion of the presentation of daily results. The following is not an +exhaustive list but includes only the most important and conspicuous +tendencies or methods together with the dates on which they were most +apparent. + +(a) May 17, choice of first box at left of group or near it, then the +next in order, and so on, until the second from the right was reached. +This method with irregularities and certain definite skipping was used +at various times, sometimes over periods of several days, during the +course of the work. + +(b) June 3, preference for number 3 and number 4 developed immediately +after the orang utan's illness and when he was working rather +listlessly. + +On June 9 and 10, the original tendency (a) reappeared and persisted for +a number of series. + +(c) June 14, a tendency to choose the box at or near the right end of a +group, and then the one next to it. In connection with this tendency, +which of course required only two choices in any given trial, interest +in playing with the sawdust on the floor developed. + +Again on June 21, the animal returned to the use of tendency (a). + +(d) June 29, movement to box at right end of group, hesitation before +it, and turning through a complete circle so that the second box from +the right was faced. This, the correct box, was often promptly entered. +This method, if persisted in, would obviously have yielded solution of +the problem. + +(e) July 5, approach to and pretense to enter the box next to the right +end (right one), and then choice of some other box. This _feint_ is +peculiarly interesting, and its origin and persistence are difficult to +account for. + +(f) In connection with the tendency to pretend that he was going to +enter the second box from the right end, Julius developed also the +tendency to turn around in front of the box at the right end, starting +sometimes to back into it, and then to enter, instead, the box second +from the end. + +(g) July, 6 and 7, a fairly definite tendency to take the one next in +order or, instead, to go directly to the right box. + +(h) July 10, direct first choices without approach to other boxes +appeared for the first time on this date. + +For this problem, it proved impossible to establish and maintain uniform +conditions of experimentation. Instead, because of the failure of the +animal to improve and the tendency to discouragement, both punishment +and reward had to be altered from time to time, and other and more +radical changes were occasionally made in the experimental procedure. +Below for the sake of condensed and consecutive presentation, the most +important conditions from day to day are arranged in tabular form: + + + +CONDITIONS OF EXPERIMENT FROM DAY To DAY FOR PROBLEM 2 + +Date Punishment Reward + +May 17 ............. 20 sec. confinement ........ Food in right box for each + (Aid after 10 trials) trial + + " 18 to 21 ........ 30 sec. confinement ........ Food (banana) in right box + for each trial + + " 22 to June 2 .... Illness, no experiments + +June 3 ............... 15 sec. confinement ........ Food (banana) in right box + for each trial + + " 4 ............... 30 " " ............. Food (banana) in right box + for each trial + + " 5-10 ............ 60 " " ............. Beet, carrot and loquat, in + addition to banana + + " 11 .............. 10 to 30 sec. confinement .. Beet, carrot and loquat, in + addition to banana + + " 12 to 15 ........ 60 sec. confinement ........ Beet, carrot and loquat, in + addition to banana + + " 16 .............. 60 " " ............. Banana and sweet corn--former + preferred + + " 17 (1st series). 60 sec. confinement ........ Food (banana, as in early + series) + + " 17 (2nd series). No confinement in wrong box; Food only for correct first + but instead, return to choices + starting point by way of + alleys + + " 18 to 22 ........ No confinement in wrong box; Food only for correct first + but instead, return to choices + starting point by way of + alleys + + " 22 (2nd series). No punishment; allowed to Food for each trial + enter boxes until right + one was found + " 23 .............. Return to starting point. + After five wrong choices + of a given box the animal + was held for 60 secs. in + one of the boxes and was + then released by way of + the exit door and rewarded + when the right one was + chosen + + " 23 (2nd series). No punishment .............. Reward for each trial + + " 24 (1st series). Return to starting point. .. Food only for correct first + choices + + " 24 (2nd series). No punishment .............. Reward for each trial + + " 25-30 ........... Same as on 24th ............ + +July 1 (1st series). No punishment .............. " " " " + + " 1 (2nd series). Return to starting point ... Reward only for correct first + choices + " 2-8 ............. Same as on July 1 .......... + + " 8 (2nd series). No punishment .............. Reward for each trial + + " 8 (3rd series). Return to starting point ... Reward only for correct first + choices + + " 9-10 ............ Same as for July 8 (3rd series) + + " 10 (2nd series). Momentary confinement in ..... Reward for each correct choice + wrong boxes + + " 12 .............. Return to starting point ..... Reward for correct first choice + + " 12 (2nd series). 30 sec. confinement .......... Reward for each correct choice + + " 12 (3rd series). 5 " " ............... " " " " " + + " 13 .............. 30 " " ............... " " " " " + + " 14-17 ........... Return to starting point ..... Reward for correct first choices + + " 17 (2nd series). 60 sec. confinement .......... Reward for each correct choice + + " 19 .............. 30 " " ............... " " " " " + + " 20-26 ........... 10 " " ............... " " " " " + + " 27-30 ........... Right box indicated by slight Reward in each right box + raising of exit door + momentarily. + No punishment + + " 30 (2nd series). Return to starting point ..... Reward for correct first choices + + " 31 .............. " " " " ..... " " " " " + + " 31 (2nd series) + to Aug. 10 .... 10 to 60 sec. confinement .... Reward for each correct choice + +Aug. 10 (2nd series). Threatened with whip ......... " " " " " + + " 11 (1st series). " " " ........... " " " " " + + " 11 (2nd series). 10 sec. confinement .......... " " " " " + + " 12 .............. Threatened with whip ......... " " " " " + + " 12 (2nd series). 10 sec. confinement .......... " " " " " + + " 19 .............. 10 " " ............... " " " " " + + " 19 (2nd series). Threatened with whip ......... " " " " " + + + + +With the above reactive tendencies and modifications of method in mind +we may continue our description of results. On June 9 there developed a +tendency to increase the magnitude of the original error by choosing +nearer the left end of the groups. This is odd, since one would +naturally suppose that an animal as intelligent as the orang utan would +tend to avoid the general region in which success was never obtained and +to focus attention on the right, as contrasted with the wrong end of +each group. _It obviously contradicts the law of the gradual elimination +of use less activities._ In other words, it is wholly at variance with +the principle of trial and error exhibited by many infrahuman organisms. +Julius, although making many mistakes, worked diligently and, for the +most part, fairly rapidly. The day's work proved most important because +of the change in method and also because of the appearance of +hesitation, the rejection of certain boxes, and the definite choice of +others. My notes record "this is a most important day for Julius in +problem 2;" but subsequent results do not clearly justify this prophecy. + +The method of choosing the first box at the left and then of moving down +the line until the right one was reached was so consistently followed +that during a number of days it was possible for me to predict almost +every choice. Indeed, to satisfy my curiosity in this matter during a +number of series I guessed in advance the box which would be chosen. The +percentages of correct guesses ranged from ninety to one hundred. June +10, for example, yielded two series for which the ratio of right to +wrong first choices was 0 to 10, and in which the method described above +was used consistently throughout. + +It was inevitable that punishment by confinement and the discouragement +resulting therefrom should interfere with the regularity of work and +make it extremely difficult to obtain strictly comparable results from +series to series and from day to day. The data for this problem, as +presented in table 9, have values quite different from those for the +monkeys, chiefly because of the more variable conditions of observation. + +It was occasionally noted that the disintegration of a definite method +and the disappearance of the tendency on which it depended occurred +rather suddenly. Frequently it happened that having used an inadequate +method fairly persistently on a given day, the animal would on the +following day exhibit a wholly different method. Even over night a new +method might develop. In the monkeys, although there was occasionally +something comparable with this, it was by no means so evident. + + + +TABLE 9 + +Results for Orang utan in Problem 2 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | 1.2.3.4.5 | | | R | W | R | W | of + | trials | 7.8.9 | 1.2.3.4 | 2.3.4.5.6.7 | 1.2.3.4.5.6 | 4.5.6.7.8 | 1.2.3 | 2.3.4.5 | 6.7.8.9 | 1.2.3.4 | 3.4.5.6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + May | | {7.7.7.7 | | | | | | | | | | | | | | + 17 | 1- 10 | {7.7.7.7 | 1.1.3 | 2.4.6 | 2.3.4.5 | 4.5.7 | 3.2 | 2.3.4 | {2.3.4.5 | 1.2.3 | 3.4.5.6.7 | 0 |10 | 0 |10 | 0:10.00 + | | {7.7.8 | | | | | | | {6.7.8 | | | | | | | + | | | | | | | | | | | {4.5.6.8 | | | | | + 18 | 11- 20 | 7.8 | 1.3 | 3.4.5.6 | 2.4.5 | 4.5.6.7 | 2 | 2.3.4 | {2.3.4.5 | 1.2.3 | {8.8.8.3 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | | {6.7.8 | | {4.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | {2.4.7.7.2 | | | | | | | {5.3.4.5 | | | | | + 19 | 21- 30 | 7.8 | 1.3 | {5.7.7.2 | 5 | 4.6.8.4.7 | 1.2 | 2.3.4 | 5.8 | 3 | {6.8.4.5 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | {3.2.4.6 | | | | | | | {3.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + 20 | 31- 40 | {7.9.7.7 | 3 | 4.5.6 | 4.5 | 5.6.7 | 2 | 4 | 5.6.7.8 | 3 | 5.6.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | {9.7.8 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 21 | 41- 50 | 7.8 | 3 | 3.4.5.6 | 4.5 | 4.5.6.7 | 2 | 3.4 | 4.5.6.8 | 3 | 4.5.6.7 | 3 | 7 | 3 | 7 | 1: 2.33 + June | | | | | | | | | | | | | | | | + 3 | 51- 60 | 7.8 | 3 | 4.5.6 | 3.4.5 | 4.5.6.7 | 3.1.2 | 3.4 | {3.7.9.7 | 3 | 4.5.6.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | {9.7.6.8 | | | | | | | + | | | | | | | | | | | | | | | | + 4 | 61- 70 | 7.8 | 3 | 4.5.6 | 4.5 | 4.5.6.7 | 3.3.1.2 | 4 | 4.5.6.7.8 | 3 | 4.5.6.7 | 3 | 7 | 3 | 7 | 1: 2.33 + 5 | 71- 80 | 7.9.7.8 | 3 | 3.4.5.6 | 3.6.3.4.5 | 4.7 | 3.1.2 | 4 | 3.4.5.6.7.8 | 3 | 4.5.6.7 | 3 | 7 | | | + " | 81- 90 | 7.8 | 3 | 3.4.5.6 | 3.4.5 | 4.5.6.7 | 2 | 3.4 | 3.4.5.6.7.8 | 2.3 | 4.5.6.7 | 2 | 8 | 5 |15 | 1: 3.00 + | | | | | | | | | | | | | | | | + 7 | 91- 100 | 7.8 | 3 | 4.5.6 | 4.5 | 4.5.6.7 | 1.2 | 3.4 | {3.4.5.6 | 2.3 | {3.4.5.6 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | | {7.8 | | {8.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + 8 | 101- 110 | 7.8 | 3 | 4.5.6 | 4.5 | 4.5.6.7 | 2 | 3.4 | 4.5.6.7.8 | 3 | 4.5.6.7 | 3 | 7 | | | + " | 111- 120 | 7.8 | 3 | 4.5.6 | 3.4.5 | 5.6.7 | 2 | 5.5.2.3.4 | 4.5.6.7.8 | 4.4.1.2.3 | 4.5.6.7 | 2 | 8 | 5 |15 | 1: 3.00 + | | | | | | | | | | | | | | | | + 9 | 121- 130 | 7.8 | 2.3 | 4.5.6 | 4.5 | 4.5.6.7 | 2 | 3.4 | {2.3.4.5 | 1.2.3 | 3.4.5.6.7 | 1 | 9 | | | + | | | | | | | | | {6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 131- 140 | 7.8 | 1.2.3 | 2.3.4.5.6 | 5 | 4.5.6.7 | 1.2 | 2.3.4 | 6.7.8 | 2.3 | 3.4.5.6.7 | 1 | 9 | 2 |18 | 1: 9.00 + | | | | | | | | | | | | | | | | + 10 | 141- 150 | 7.8 | 1.2.3 | 2.3.4.5.6 | 1.2.3.4.5 | 4.5.6.7 | 1.2 | 2.3.4 | {1.2.3.4 | 1.2.3 | 3.4.5.6.7 | 0 |10 | | | + | | | | | | | | | {5.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 151- 160 | 7.8 | 1.2.3 | 2.3.4.5.6 | 1.2.3.4.5 | 4.5.6.7 | 1.2 | 2.3.4 | {1.2.3.4 | 1.2.3 | 3.4.5.6.7 | 0 |10 | 0 |10 | 0:10.00 + | | | | | | | | | {5.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + 11 | 161- 170 | 8 | {4.1.2.4.1 | 2.3.4.5.6 | 5 | 6.7 | {3.1.3.1 | 5.2.3.4 | 2.6.7.8 | 4.1.2.3 | 8.5.6.7 | 2 | 8 | | | + | | | {4.1.4.1.3 | | | | {3.1.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 171- 180 | 9.7.8 | 4.3 | 5.6 | 4.5 | 7 | 3.1.2 | 5.4 | 8 | 4.2.3 | 7 | 3 | 7 | 5 |15 | 1: 3.00 + 12 | 181- 190 | 7.9.7.9.8 | 1.2.3 | 3.4.5.6 | 6.4.5 | 5.6.7 | 2 | 5.3.4 | 7.8 | 4.1.2.3 | 4.5.6.7 | 1 | 9 | 1 | 9 | 1: 9.00 + 14 | 191- 200 | 9.8 | 3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 6.7.8 | 4.2.3 | 7 | 2 | 8 | | | + " | 201- 210 | 8 | 2.3 | 7.6 | 6.5 | 8.7 | 3.1.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | 5 |15 | 1: 3.00 + | | | | | | | | | | | | | | | | + 15 | 211- 220 | {7.9.7.9 | 4.2.3 | 6 | 5 | 8.7 | 3.2 | 5.4 | 9.8 | 4.3 | 7 | 3 | 7 | | | + | | {7.9.8 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 221- 230 | 9.8 | 4.3 | 7.6 | 6.5 | 5.6.7 | 1.2 | 2.3.4 | 3.4.5.6.7.8 | 4.3 | 7 | 1 | 9 | 4 |16 | 1: 4.00 + 16 | 231- 240 | 7.9.8 | 3 | 7.6 | 6.5 | 8.7 | 2 | 5.4 | 5.6.7.8 | 4.1.4.3 | 8.7 | 2 | 8 | | | + " | 241- 250 | 9.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 6.7.8 | 4.3 | 6.7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | | | | | | | | | | | + 17 | 251- 260 | 9.8 | 4.3 | 7.6 | 6.5 | {6.5.4.6 | 3.2 | 5.4 | 6.5.6.7.8 | 3 | 5.6.7 | 1 | 9 | | | + | | | | | | {5.4.5.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | {6.6.6.5.6 | | | | | | | | | | + | | | | | | {5.5.5.6.6 | | | | | | | | | | + " | 261- 270 | {9.7.7.7 | 4.4.4.4.3 | 6 | 5 | {6.6.6.6.6 | {3.3.3.3 | 4 | {4.5.4.5.4 | 3 | {5.5.5.5 | 4 | 6 | 5 |15 | 1: 3.00 + | | {7.7.7.8 | | | | {6.5.4.5 | {3.3.2 | | {5.6.7.8 | | {5.5.8.7 | | | | | + | | | | | | {6.5.5.4 | | | | | | | | | | + | | | | | | {4.5.6.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + 18 | 271- 280 | {7.7.7.7 | 4.4.4.4.3 | 5.5.5.5.6 | 5 | {5.5.5.6 | {3.3.3. | 4 | {4.6.5.6 | 4.4.3 | 5.6.4.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | {7.7.8 | | | | {5.5.6 | {3.3.2 | | {6.7.4.8 | | | | | | | + | | | | | | | | | | | | | | | | + | | {7.7.7.9 | | | | | | | | | | | | | | + 19 | 281- 290 | {9.9.9.7 | {4.4.4 | {5.7.7 | 5 | 5.7 | {3.3.3.3 | 4 | 5.8 | {4.4.4.4 | {6.5.6.5 | 2 | 8 | | | + | | {7.7.8 | {4.4.3 | {7.4.6 | | | {3.3.2 | | | {4.4.3 | {5.5.7 | | | | | + | | | | | | | | | | | | | | | | + " | 291- 300 | 7.7.7.7.8 | 4.4.4.4.3 | 5.5.6 | 5 | {5.6.6.5.6 | 3.3.2 | {5.5.5.5 | 5.6.8 | 4.4.3 | 6.6.6.7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | {6.6.6.7 | | {3.4 | | | | | | | | + | | | | | | | | | {5.6.6.6.7 | | | | | | | + 21 | 301- 310 | 7.7.8 | 4.4.3 | 5.6 | 5 | {6.6.6.5 | {3.3.3.3 | 5.5.5.2.4 | {3.4.3.5.5 | {4.2.2.4 | 5.3.7 | 1 | 9 | | | + | | | | | | {5.6.5.7 | {3.2 | | {1.1.2.4.7 | {4.3 | | | | | | + | | | | | | | | | {2.3.2.2.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 311- 320 | {7.7.7.7 | 1.1.1.2.3 | {5.5.4.2 | 1.1.6.5 | 4.6.7 | 1.3.2 | {2.2.2.2 | {1.1.2.3 | {2.2.2.4 | {6.3.3.8 | 0 |10 | 1 |19 | 1:19.00 + | | {7.7.8 | | {2.5.6 | | | | {2.2.3.4 | {6.6.6.8 | {2.3 | {4.8.7 | | | | | + | | | | | | | | | | | | | | | | + 22 | 321- 330 | 7.8 | {2.4.2.1.4 | 6 | 5 | 6.6.8.7 | 3.2 | 5.5.3.3.4 | 3.3.7.7.8 | 4.4.4.2.3 | 6.7 | 2 | 8 | | | + | | | {4.4.4.3 | | | | | | | | | | | | | + " | 331- 340 | 7.8 | 3 | 6 | 5 | 6.7 | 3.2 | 5.4 | 6.7.8 | 3 | 5.6.7 | 4 | 6 | 6 |14 | 1: 2.33 + | | | | | | | | | | | | | | | | + 23 | 341- 350 | 7.8 | 4.2.4.3 | 6 | 5 | 6.7 | {3.3.3.1 | 5.5.4 | {7.5.4.3 | 4.4.4.3 | {6.6.3.6 | 2 | 8 | | | + | | | | | | | {3.3.3.2 | | {6.7.7.8 | | {8.6.8.7 | | | | | + | | | | | | | | | | | | | | | | + " | 351- 360 | 7.8 | 4.4.3 | 6 | 6.5 | 6.7 | 3.3.2 | 5.4 | {6.7.6.5 | 4.3 | 5.6.7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | | | | {7.6.8 | | | | | | | + | | | | | | | | | | | | | | | | + 24 | 361- 370 | 7.8 | 4.4.2.3 | 7.7.6 | 6.6.4.5 | 7 | {3.3.3.3 | 5.4 | 8 | 4.4.3 | 5.6.7 | 2 | 8 | | | + | | | | | | | {3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 371- 380 | 8 | 4.3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 7.6.8 | 4.3 | 7 | 4 | 6 | 6 |14 | 1: 2.33 + | | | | | | | | | | | | | | | | + 25 | 381- 390 | 8 | 4.4.3 | 7.7.7.6 | {6.6.6.6 | 8.6.7 | 3.1.2 | 5.3.5.4 | 8 | 3 | 7 | 4 | 6 | | | + | | | | | {6.4.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 391- 400 | 8 | 4.3 | 6 | 5 | 6.5.8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 5 | 5 | 9 |11 | 1: 1.22 + | | | | | | | | | | | | | | | | + 26 | 401- 410 | 9.9.9.8 | 3 | {7.7.7.7.3 | {6.6.6.6 | 8.8.8.7 | 3.2 | {5.5.5.5 | 7.8 | {4.4.4.4 | 6.6.8.8.7 | 1 | 9 | | | + | | | | {3.7.7.6 | {6.6.5 | | | {5.5.4 | | {4.4.3 | | | | | | + | | | | | | | | | | | | | | | | + " | 411- 420 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 4 |16 | 1: 4.00 + | | | | | | | | | | | | | | | | + 28 | 421- 430 | 8 | {4.4.4.4 | 7.6 | {6.6.3.6 | 7 | {3.3.3.3 | 5.5.5.4 | 9.7.7.5.8 | 4.4.4.3 | 8.7 | 2 | 8 | | | + | | | {4.4.3 | | {6.6.6.5 | | {3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 431- 440 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {7.6.5.4 | | | | | | | + " | 441- 450 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | {3.2.1.5 | 4.3 | 7 | 2 | 8 | 8 |22 | 1: 2.75 + | | | | | | | | | {7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + 29 | 451- 460 | 8 | 3 | 6 | 6.6.6.5 | 8.6.7 | {3.3.3.3 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | | | + | | | | | | | {3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 461- 470 | 8 | 4.3 | 6 | 5 | 8.7 | 3.2 | 3.2.3.4 | 7.8 | 4.3 | 7 | 4 | 6 | | | + " | 471- 480 | 8 | 4.4.3 | 7.7.6 | 6.6.5 | 7 | 2 | 5.5.5.5.5.4 | 7.8 | 4.4.3 | 7 | 4 | 6 |13 |17 | 1: 1.31 + | | | | | | | | | | | | | | | | + 30 | 481- 490 | 8 | {4.4.4.4 | 7.7.6 | 6.6.6.5 | 8.6.6.5.7 | {3.1.3.3 | 5.5.5.4 | 8 | 4.4.4.3 | 7 | 3 | 7 | | | + | | | {4.4.3 | | | | {3.3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 491- 500 | 8 | 4.3 | 7.7.7.6 | 6.6.5 | 8.8.7 | 3.3.3.3.2 | 5.4 | {9.9.7.4 | 3 | 8.8.7 | 2 | 8 | 5 |15 | 1: 3.00 + | | | | | | | | | {9.6.8 | | | | | | | + July | | | | | | | | | | | | | | | | + 1 | 501- 510 | 9.7.9.8 | 4.3 | 6 | 6.5 | 8.6.7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 511- 520 | {9.7.7.7 | 4.3 | 7.6 | 6.4.5 | 7 | 3.2 | 4 | 8 | 4.4.4.3 | 8.6.5.6.7 | 3 | 7 | 6 |14 | 1: 2.33 + | | {7.9.8 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 2 | 521- 530 | 9.8 | 3 | 7.5.7.6 | 6.4.5 | 8.7 | 2 | 4 | 8 | 3 | 7 | 6 | 4 | | | + | | | | | | | | | | | | | | | | + " | 531- 540 | 9.9.7.8 | 3 | 7.4.6 | 5 | 6.6.7 | 3.3.2 | 3.4 | 7.3.5.4.8 | 4.3 | {8.8.6.5 | 2 | 8 | 8 |12 | 1: 1.50 + | | | | | | | | | | | {4.5.7 | | | | | + | | | | | | | | | | | | | | | | + 3 | 541- 550 | 8 | 4.3 | 6 | {6.6.6.6 | 6.8.7 | 3.3.3.2 | 5.5.4 | 9.6.9.6.8 | 4.3 | 7 | 3 | 7 | | | + | | | | | {6.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 551- 560 | 9.9.7.8 | 4.3 | 6 | 5 | 8.6.5.7 | {3.3.3.3 | 5.4 | {7.6.5.7 | 3 | 7 | 4 | 6 | 7 |13 | 1: 1.86 + | | | | | | | {3.2 | | {9.7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + 5 | 561- 570 | 8 | 4.3 | 7.6 | 6.5 | {8.8.8.8 | {3.3.3.3 | 5.5.5.5.4 | 8 | 4.4.4.3 | 8.8.8.8.7 | 2 | 8 | | | + | | | | | | {8.8.7 | {3.3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 571- 580 | 9.8 | 4.4.4.3 | 6 | 6.5 | 8.8.7 | {3.3.3.3.3 | {5.5.5.5.5 | 7.6.8 | 4.4.3 | 7 | 2 | 8 | 4 |16 | 1: 4.00 + | | | | | | | {3.3.3.2 | {5.5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | + 6 | 581- 590 | 9.8 | 4.3 | 7.7.6 | 6.6.5 | 7 | 2 | 5.4 | 7.8 | 4.3 | 7 | 3 | 7 | | | + " | 591- 600 | 8 | 3 | 6 | 4.5 | 6.6.6.7 | 2 | 5.3.5.4 | 8 | 4.4.3 | 8.8.8.7 | 5 | 5 | 8 |12 | 1: 1.50 + 7 | 601- 610 | 8 | 1.3 | 6 | 5 | 6.5.7 | 2 | 5.4 | 5.6.6.6.7.8 | 4.3 | 7 | 5 | 5 | | | + | | | | | | | | | | | | | | | | + " | 611- 620 | {9.7.7.7.9 | 3 | 6 | 5 | 6.5.6.5.7 | 3.2 | 5.4 | 7.9.7.9.8 | {4.4.4.4 | 8.7 | 3 | 7 | 8 |12 | 1: 1.50 + | | {7.7.7.8 | | | | | | | | {4.4.4.3 | | | | | | + | | | | | | | | | | | | | | | | + 8 | 621- 630 | {9.9.9.7.9 | 4.3 | 6 | 6.6.6.5 | {8.8.8.8 | 3.2 | 5.4 | 7.6.8 | 3 | 7 | 3 | 7 | | | + | | {9.9.8 | | | | {5.6.5.7 | | | | | | | | | | + | | | | | | | | | {7.6.5.7 | | | | | | | + " | 631- 640 | 9.8 | 3 | 6 | 6.5 | 7 | 3.2 | 4 | {6.5.4.6 | 3 | 7 | 6 | 4 | | | + | | | | | | | | | {9.7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 641- 650 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 7.9.6.7.9.8 | 3 | 8.6.8.7 | 8 | 2 |17 |13 | 1: 0.76 + 9 | 651- 660 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 7.6.7.6.8 | 3 | 8.6.8.8.4.7 | 8 | 2 | | | + " | 661- 670 | 9.9.8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 7.6.7.6.8 | 4.3 | 5.6.8 | 3 | 7 |11 | 9 | 1: 0.82 + | | | | | | | | | | | | | | | | + 10 | 671- 680 | 9.8 | 3 | 5.4.5.6 | 5 | 6.4.8.6.7 | 3.2 | {3.5.3.2.3 | {7.6.5.6 | 3 | 5.4.3.7 | 3 | 7 | | | + | | | | | | | | {5.3.5.2.4 | {5.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 681- 690 | 8 | 4.3 | 6 | 5 | 7 | 2 | 5.4 | 8 | 3 | 6.8.7 | 7 | 3 |10 |10 | 1: 1.00 + 12 | 691- 700 | 7.8 | 3 | 5.6 | 5 | 7 | 3.2 | 3.4 | 7.7.7.7.8 | 4.2.2.3 | 8.7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 701- 710 | 9.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | {7.6.5.4.3 | 3 | 8.7 | 2 | 8 | | | + | | | | | | | | | {2.1.4.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 711- 720 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | {7.6.5.4.3 | 3 | {6.5.4.3.6 | 4 | 6 | 9 |21 | 1: 2.33 + | | | | | | | | | {2.5.9.8 | | {5.4.3.8.7 | | | | | + | | | | | | | | | | | | | | | | + 13 | 721- 730 | 7.8 | 4.3 | 6 | 4.3.6.5 | 4.6.5.4.7 | 2 | 4 | {6.5.4.3 | 3 | {5.4.3.6 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | {2.1.8 | | {8.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {4.7.5.4 | | | | | | | + 14 | 731- 740 | 8 | 3 | 5.5.6 | 5 | {5.6.5.5 | 3.2 | 4 | {7.7.4.6 | 3 | 4.6.7 | 5 | 5 | | | + | | | | | | {8.8.7 | | | {5.6.8 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {5.4.5.5.4 | | {4.4.4.5.5 | | | | | + " | 741- 750 | 8 | 3 | 5.6 | 5 | {6.5.6.6 | 2 | 4 | {5.6.4.4.4 | 3 | {5.4.8.8.4 | 6 | 4 |11 | 9 | 1: 0.82 + | | | | | | {6.8.4.7 | | | {7.6.8 | | {5.5.6.4.7 | | | | | + | | | | | | | | | | | | | | | | + 15 | 751- 760 | 7.7.9.7.8 | 3 | 6 | 5 | 6.6.7 | 2 | 4 | 6.6.8 | 3 | {6.6.6.8 | 6 | 4 | | | + | | | | | | | | | | | {5.6.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | {5.4.6.6.5 | | | | | + " | 761- 770 | 8 | 3 | 5.6 | 5 | 6.6.6.6.7 | 2 | 3.4 | 5.4.7.8 | 3 | {5.3.5.8.5 | 5 | 5 |11 | 9 | 1: 0.82 + | | | | | | | | | | | {5.5.7 | | | | | + | | | | | | | | | {4.6.7.6.9 | | | | | | | + 16 | 771- 780 | 7.7.7.8 | 3 | 6 | 4.5 | 5.7 | 2 | 3.4 | {7.7.5.5 | 3 | (5.6.8.5 | 4 | 6 | | | + | | | | | | | | | {6.6.6.8 | | {3.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {6.6.7.2 | | | | | | | + " | 781- 790 | 7.8 | 3 | {4.5.4.3 | {4.6.4.4 | {4.4.6.8 | 2 | 3.4 | {3.4.4.4 | 3 | 6.7 | 3 | 7 | 7 |13 | 1: 1.86 + | | | | {2.6 | {1.4.3.5 | {5.7 | | | {9.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + 17 | 791- 800 | 7.8 | 2.3 | 6 | {4.4.4.3.6 | 4.8.4.6.7 | 2 | 4 | {5.7.6.6.1 | 3 | 5.7 | 4 | 6 | | | + | | | | | {2.4.2.5 | | | | {7.4.4.8 | | | | | | | + | | | {2.4.4.4.2 | | | | | | | | | | | | | + " | 801- 810 | 7.8 | {4.2.4.1.4 | 5.7.6 | 5 | 5.7 | 2 | 3.5.5.4 | 6.8 | {2.4.4.2 | 6.8.7 | 2 | 8 | 6 |14 | 1: 2.33 + | | | {2.4.3 | | | | | | | {4.2.4 3 | | | | | | + | | | | | | | | | | | | | | | | + 19 | 811- 820 | 7.9.7.8 | 2.4.2.4.3 | 5.7.6 | 3.6.4.6.5 | 7 | 2 | 3.5.4 | 6.8 | 4.4.3 | 6.8.7 | 2 | 8 | | | + " | 821- 830 | 7.8 | 2.4.4.3 | 6 | 4.6.6.6.5 | 6.8.7 | 2 | 3.5.5.5.4 | 6.8 | 2.4.3 | 6.5.7 | 2 | 8 | | | + " | 831- 840 | 7.9.8 | 2.4.4.2.4.3 | 7.6 | 5 | 7 | 2 | 4 | 7.6.4.6.8 | 2.4.3 | 6.8.7 | 4 | 6 | 8 |22 | 1: 2.75 + 20 | 841- 850 | 7.8 | 3 | 5.7.6 | 4.6.5 | 6.8.7 | 2 | 3.5.4 | 3.5.8 | 2.4.3 | 6.8.6.8.7 | 2 | 8 | | | + " | 851- 860 | 8 | 2.4.3 | 6 | 3.6.5 | 5.7 | 2 | 2.5.4 | 4.7.8 | 2.4.3 | 4.4.6.7 | 3 | 7 | | | + " | 861- 870 | 7.8 | 2.4.3 | 6 | 5 | 7 | 2 | 2.4 | 6.8 | 2.4.3 | 4.7 | 4 | 6 | 9 |21 | 1: 2.33 + 21 | 871- 880 | 7.9.8 | 2.4.3 | 5.7.6 | {4.6.4.6 | 4.6.7 | 2 | 3.5.3.5.4 | 5.7.8 | 2.4.3 | 5.7 | 1 | 9 | | | + | | | | | {3.2.4.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 881- 890 | 7.8 | 2.4.2.3 | 3.5.7.6 | 3.4.6.4.6.5 | 4.6.5.6.7 | 2 | 4 | 6.8 | 3 | 4.6.5.7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 891- 900 | 7.8 | 2.4.3 | 5.7.6 | 4.5 | 5.7 | 3.3.3.2 | 4 | {4.6.5.7.6 | 2.4.3 | 5.7 | 1 | 9 | 5 |25 | 1: 5.00 + | | | | | | | | | {4.2.4.8 | | | | | | | + | | | | | | | | | | | | | | | | + 22 | 901- 910 | 7.8 | 2.4.3 | 5.7.6 | 4.6.5 | 6.8.7 | 2 | 2.5.4 | 5.6.8 | 2.3 | 6.7 | 1 | 9 | | | + " | 911- 920 | 7.8 | 2.3 | 5.6 | 4.5 | 5.7 | 2 | 3.4 | 4.6.8 | 2.3 | 5.6.7 | 1 | 9 | 2 |18 | 1: 9.00 + | | | | | | | | | | | | | | | | + 23 | 921- 930 | 7.8 | 2.3 | {3.2.4.4 | 5 | 4.6.5.6.7 | 2 | 3.2.4 | 5.4.6.8 | 2.3 | {4.5.4.3.5 | 2 | 8 | | | + | | | | {5.6 | | | | | | | {6.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + 23 | 931- 940 | 7.9.7.8 | 3 | 5.4.6 | 5 | 5.7 | 2 | 4 | 6.7.8 | 3 | 6.8.7 | 5 | 5 | | | + " | 941- 950 | 7.8 | 3 | 5.6 | 4.6.5 | 7 | 2 | 3.5.4 | 5.6.8 | 2.3 | 6.7 | 3 | 7 |10 |20 | 1: 2.00 + | | | | | | | | | | | | | | | | + 24 | 951- 960 | 7.8 | 2.3 | {2.7.7.4 | 4.6.5 | 5.7 | 2 | 4 | 4.6.8 | 3 | 6.8.7 | 3 | 7 | | | + | | | | {5.7.4.6 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 961- 970 | 7.9.7.8 | 3 | 6 | 5 | (6.8.6.8 | 2 | 5.5.3.4 | 7.8 | 3 | 7 | 6 | 4 | 9 |11 | 1: 1.22 + | | | | | | {6.7 | | | | | | | | | | + | | | | | {4.2.6.4 | | | | | | | | | | | + 26 | 971- 980 | 7.9.7.8 | 3 | 6 | {6.4.6.4 | 7 | 2 | 4 | 6.8 | 3 | 6.8.7 | 6 | 4 | | | + | | | | | {6.1.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 981- 990 | 7.9.7.8 | 3 | 6 | 5 | 7 | 2 | 4 | 7.6.8 | 3 | 6.8.7 | 7 | 3 | | | + | 991-1000 | 7.8 | 3 | 6 | 5 | 6.8.5.7 | 2 | 4 | 6.8 | 4.2.3 | 6.5.7 | 5 | 5 |18 |12 | 1: 0.67 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + In |trials 1001| to 1100 the | right door |was indicated | by being |raised before | the choice | was made. | | | | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 30 | 1101-1110 | 8 | 4.3 | 7.6 | 6.6.5 | 7 | 2 | 5.4 | {7.7.7.7.7 | 3 | 6.6.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | {7.6.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {7.7.6.7 | | | | | | | + 31 | 1111-1120 | 7.7.8 | 3 | 7.6 | 5 | 6.7 | 3.3.2 | 4 | {7.6.6.7 | 4.4.4.3 | 7 | 4 | 6 | | | + | | | | | | | | | {6.6.8* | | | | | | | + | | | | | | | | | | | | | | | | + " | 1121-1130 | 8 | 4.3 | 6 | 6.5 | 8.7 | 3.2 | 5.4 | 7.8 | 3 | 7 | 4 | 6 | 8 |12 | 1: 1.50 + August | | | | | | | | | | | | | | | | + 2 | 1131-1140 | 8 | 4.4.3 | 6 | 5 | 7 | 3.3.3.2 | 4 | 7.8 | 4.3 | 7 | 6 | 4 | | | + " | 1141-1150 | 7.8 | 4.4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | 9 |11 | 1: 1.22 + 3 | 1151-1160 | 7.9.8 | 4.3 | 7.6 | 5 | 6.7 | 2 | 5.4 | 7.6.7.8 | 4.3 | 6.7 | 2 | 8 | | | + " | 1161-1170 | 8 | 4.3 | 6 | 5 | 7 | 2 | 5.4 | 7.8 | 4.3 | 7 | 6 | 4 | 8 |12 | 1: 1.50 + 4 | 1171-1180 | 8 | 4.3 | 6 | 6.5 | 6.7 | 3.2 | 5.4 | 7.8 | 4.3 | 6.5.6.7 | 2 | 8 | | | + " | 1181-1190 | 8 | 3 | 6 | 5 | 7 | 3.3.2 | 4 | 7.8 | 3 | 7 | 8 | 2 |10 |10 | 1: 1.00 + 5 | 1191-1200 | 7.8 | 4.4.3 | 6 | 5 | 6.7 | 3.3.3.2 | 4 | 6.7.8 | 3 | 7 | 5 | 5 | | | + | 1201-1210 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 3 | 7 | 5 | 5 | | | + " | 1211-1220 | 7.8 | 3 | 7.6.5 | 5 | 7 | 2 | 4 | 7.7.6.7.8 | 3 | 7 | 7 | 3 |17 |13 | 1: 0.76 + | | | | | | | | | | | | | | | | + 6 | 1221-1230 | 8 | 3 | 6 | 5 | {6.5.6.6 | 2 | 4 | {5.6.5.7 | 3 | 6.8.6.7 | 7 | 3 | | | + | | | | | | {5.6.5.7 | | | {9.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 1231-1240 | 7.8 | 3 | 6 | 4.5 | 7 | 2 | 4 | 6.7.8 | 3 | 6.7 | 6 | 4 |13 | 7 | 1: 0.54 + 7 | 1241-1250 | 7.8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 8.7 | 8 | 2 | | | + " | 1251-1260 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 7 | 3 | | | + " | 1261-1270 | 8 | 3 | 6 | 5 | 7 | 3.2 | 5.3.4 | 8 | 3 | 7 | 8 | 2 |23 | 7 | 1: 0.30 + 9 | 1271-1280 | 8 | 3 | 6 | 5 | 7 | 2 | 5.4 | 9.7.8 | 3 | 7 | 8 | 2 | | | + " | 1281-1290 | 8 | 3 | 6 | 5 | 7 | 3.2 | 4 | 7.8 | 3 | 7 | 8 | 2 |16 | 4 | 1: 0.25 + 10 | 1291-1300 | 7.8 | 3 | 7.6 | 5 | 6.7 | 3.2 | 4 | 6.7.8 | 3 | 7 | 5 | 5 | | | + " | 1301-1310 | 7.8 | 4.3 | 5.6 | 4.5 | 6.7 | 2 | 4 | 6.8 | 3 | 6.8.7 | 3 | 7 | | | + " | 1311-1320 | 7.8 | 3 | 6 | 5 | 5.7 | 2 | 4 | 5.7.8 | 3 | 4.6.8.7 | 6 | 4 |14 |16 | 1: 1.14 + 11 | 1321-1330 | 7.8 | 3 | 6 | 5 | 6.7 | 3.2 | 4 | 4.6.7.8 | 2.3 | 5.7 | 4 | 6 | | | + " | 1331-1340 | 7.8 | 3 | 6 | 4.5 | 6.7 | 2 | 4 | 6.7.8 | 3 | 7 | 6 | 4 |10 |10 | 1: 1.00 + 12 | 1341-1350 | 9.8 | 3 | 6 | 5 | 6.7 | 2 | 4 | 6.7.8 | 3 | 6.7 | 6 | 4 | | | + " | 1351-1360 | 7.8 | 3 | 6 | 5 | 6.7 | 2 | 4 | 7.8 | 3 | 6.7 | 6 | 4 |12 | 8 | 1: 0.67 + 19 | 1361-1370 | 7.8 | 3 | 6 | 5 | 6.7 | 2 | 4 | 6.7.8 | 3 | 6.7 | 6 | 4 | | | + | 1371-1380 | 9.8 | 3 | 6 | 5 | 7 | 3.2 | 4 | 7.9.8 | 3 | 6.8.7 | 6 | 4 |12 | 8 | 1: 0.67 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +After two hundred and fifty trials on problem 2 had been given Julius, +it seemed desirable to introduce a radical change in method in order to +stimulate him to maximal effort. It was therefore decided to force him +to make a round trip through the apparatus in connection with each +choice, and to let this forced labor serve, in the place of confinement, +as punishment for mistakes. This new method yielded peculiar and +characteristic results. They differ from those previously obtained +largely because of the orang utan's remarkably strong tendency to +reenter the box through which he had just passed. This occurred so +persistently, as may be seen in table 9 (June 17, second series, June +18, etc.), that a further modification of method was introduced in that +after the same wrong box had been entered five times in succession, the +experimenter on the next choice of the box confined the animal for a +stated interval, say sixty seconds, in it, and then allowed it to escape +by way of the exit door and choose repeatedly until it finally located +the right box. Were it not for this particular feature of the method, +the number of choices recorded after June 17 would unquestionably be +very much greater than the table indicates. + +The new method proved a severe test of the orang utan's patience and +perseverance, for he had to work much harder than formerly for his +reward, and often became much fatigued before completing the regular +series of ten trials. Early in the use of this method, he developed the +habit of rolling around from exit door to starting point by a series of +somersaults. When especially discouraged he would often bump his head +against the floor so hard that I could hear the dull thud. As has been +noted, I found it desirable to vary the procedure repeatedly. It proved +especially interesting to give one series per day with the round trip as +punishment and another series with confinement as punishment. + +Day after day, as the experiment progressed, slight or great +fluctuations of the ratios of right to wrong choices appeared, but +without consistent improvement. There was, to be sure, as the last +column of table 9 shows, a radical improvement during the first six +hundred and fifty trials, for the number of right choices per series +increased from 0 to 8. But, as the observations were continued from day +to day, it became more and more evident that the animal was merely +passing from tendency to tendency--method to method--mixing tendencies, +and occasionally developing new ones, without approach to the solution +of the problem. This fact would have led me to discontinue the work much +earlier than I actually did had it not been for the peculiarity of the +results obtained with problem 1. It seemed not improbable that at any +time Julius might succeed in perfectly solving this problem over night +precisely as he had solved the first problem. + +A curiously interesting bit of behavior appeared for the first time on +June 29. Julius had gone to the first box at the right end of the group, +and instead of entering, he had wheeled around toward his right, and +turning a complete circle, faced the right box, which he promptly +entered. Subsequently, the tendency developed and the method was used +with increasing frequency. On June 30, it appeared in the first series, +four times, in the second series, six times; on July 1, in the first +series, three times, and in the second series, four times; on July 2, in +the first series, five times, and in the second series, nine times. It +was indeed only by accident that the animal failed to fulfill the +technical requirement for perfect solution of the problem in this +series. Yet, had he done so, his subsequent trials would doubtless have +revealed the lack of any other idea than that of turning completely +around before entering a box. + +This odd bit of behavior proved peculiarly interesting and significant +in that the tendency to turn became dissociated from the position (in +front of the first box at the right end of the group) in connection with +which it originally developed. After a few days, Julius would enter the +reaction-chamber and instead of proceeding directly to the right end of +the group, would stop suddenly wherever he happened to be, turn toward +his right in a complete circle, and hasten into the box nearest to him +which, as often as not, proved to be the wrong one. Thus the idea of +turning completely about, which had it continued its association with +the idea of facing the first box at the right, would have yielded +success, instead became useless because of its dissociation. That the +orang utan is capable of using free ideas seems clear enough in the +light of this behavior. That he proved incapable of getting the idea of +second from the right end is as clearly shown by the detailed results of +table 9,--the fruits of weeks of experimenting. + +Certain other interesting tricks developed in Julius's behavior. Thus, +on July 5, there appeared the tendency to move as though about to enter +the right box (feint), then to stop suddenly and promptly enter another +box, which was, of course, a wrong one. The reason for the development +of this tendency could not be discovered, but in connection with it, +there appeared another tendency which possibly can be explained. Julius +took to backing into the chosen box so that he could face the +experimenter. He would then, after a period of hesitation, come out and +promptly enter one of the other boxes. This tendency was apparently due +to the fact that during one or two series the experimenter growled at +the orang utan every time he made a mistake. The growl startled him and +caused him to look around. He evidently felt the need of keeping his +eyes on the experimenter,--Hence the backing into the open box. The +tendency disappeared shortly after the experimenter gave up the use of +the growl as a method of punishing the animal for what were suspected to +be careless choices. + +Curiously enough, it was not until July 10 that direct choice of the +right box was made at all frequently. Previously, selection of it had +been made almost invariably after approach to other boxes. But in the +second series for July 10 there was an extraordinary improvement in +method. This developed in the presence of two visitors, and it is +therefore all the more surprising. The choices were made not only +directly, but with decision and evident certainty that was quite at +variance with the previous behavior of the animal. + +All the while through variation of methods, I was seeking to discover +the best means of holding the orang utan to his maximum effort and care +in attempting to select the right box. One day it would seem as though +forcing him to make round trips with rewards only for correct first +choices proved most satisfactory, and the next it might seem equally +clear that punishment by confinement for thirty seconds or sixty +seconds, with reward for correct choice in every trial, yielded better +results. In the end I had to admit that no best method had been +demonstrated and that I had failed to develop conditions which served to +compel the animal's attention to the problem and to lead him to work +without discouragement. There were, it is true, days on which it seemed +practically certain that the problem would be solved, but as it turned +out, Julius never succeeded in choosing correctly--throughout a series +of ten trials. + +As a last resort, in order to make perfectly sure that the orang utan +was doing his best, I decided to introduce corporal punishment in a mild +form. For this purpose, I placed my assistant in charge of the apparatus +and the series of trials, and stationed myself in one corner of the +reaction-chamber with a whip in my hand. Whenever Julius entered a wrong +box, I approached him with the whip and struck at him, being careful not +to injure him and rarely striking him at all, for the threat was more +effective than a blow. He was extremely afraid of the whip and would +begin to whine and attempt to get out of the way as soon as he saw it. + +This method was introduced on August 10, but no improvement resulted, +and in the end there was no reason to consider it more satisfactory than +the other procedures. I am now wholly convinced that Julius did his best +to choose correctly in the majority of the numerous series which were +given him in connection with problem 2. + +From trials 1001 to 1100, a radical departure from the previous methods +was introduced in that the right box was indicated to the animal by the +slight and momentary raising of its exit door. Of course no records of +the choices for this group of one hundred trials appear in table 9, for +the simple reason that the animal inevitably and immediately entered the +right box. It was thought that this method might serve to break up the +previously developed tendencies toward inadequate forms of response and +so encourage the animal that he would later solve the problem when given +opportunity to select the right box without aid from the experimenter. +But as a matter of fact, while the ratio of right to wrong first choices +was 1 to .67 in the series preceding this change of method, it was 1 to +1.50 in the first series following its use. There is no satisfactory +evidence that Julius profited by this experience, though as a matter of +fact he did succeed in making his best daily record, eight right to two +wrong choices, on August 4, after 1190 trials. + +The curve of learning for this problem has been plotted and is presented +in figure 19. It is of course incomplete and it is offered only to +indicate the extreme irregularity in performance. + + +_Problem 1a. First at the Right End_ + +It was decided on August 19 that the further continuation of the work of +Julius on problem 2 was not worth while. He had become much discouraged, +and although willing to work for food, gave no indications whatever of +improvement and seemed to have exhausted his methods. It seemed wise +instead of giving up work with him in the multiple-choice method to +return to a form of problem 1. We may designate it as problem 1a. The +right box is definable as the first at the right end of the series +instead of the first at the left end as in the original problem 1. It +was thought possible that Julius might quickly solve this problem by a +process similar to that used for problem 1. + +Work was begun on problem 1a, August 20, and for six successive days two +series of trials per day were given, the settings for which as well as +the resulting choices are given in table 10. Most notable in these +results is the large number of cases in which Julius chose first the +second box from the right end of the series, or in other words that box +which had been the right one in problem 2. Contrary to expectation, he +showed no inclination to abandon this tendency to choose the second from +the right end, and the ratio of right to wrong choices changed in the +direction opposite from expectation, beginning with 1 to 4 and ending on +the sixth day with 0 to 20. + +It was obviously useless to continue the experiment further since Julius +had given up his attempts to locate the right box in the first choice +and was apparently satisfied to discover it by a process of trial and +error. He had, it would seem, satisfied himself that the problem was +insoluble. These results obtained in problem 1a constitute a most +interesting comment on the effects of problem 2 on the orang utan. +Behavior similar to that which he developed well might have been +obtained from a child of three to four years placed in a like situation +and forced to strive, day after day, to solve a problem beyond its +ideational capacity. + +In many respects the most interesting and to the experimenter the most +surprising result of this long series of observations with Julius was +the lack of consistent improvement. It seemed almost incredible that he +should continue, day after day, to make incorrect choices in a +particular setting while choosing correctly in some other setting which +from the standpoint of the experimenter was not more difficult. + + + +TABLE 10 + +Results for Orang utan in problem 1a + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | | 1.2.3.4 | R | W | R | W | of + | trials | 5.63 | 1.2.3.4 | 6.7.8.9 | 2.3.4.5 | 3.4.5.6.7 | 1.2.3 | 5.6.7.8 | 1.2 | 2.3.4.5.6 | 5.6.7 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + August | | | | | | | | | | | | | | | | + 20 | 1- 10 | 6 | 3.4 | 6.7.8.9 | 4.5 | 6.7 | 3 | 7.8 | 2 | 5.5.6 | 6.7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 11- 20 | 5.6 | 3.4 | {7.8.7.8 | 4.5 | 6.7 | 2.3 | {7.6.7.7 | 2 | 5.6 | 6.7 | 1 | 9 | 4 |16 | 1: 4.00 + | | | | {8.7.8.9 | | | | {6.7.7.8 | | | | | | | | + | | | | | | | | | | | | | | | | + 21 | 21- 30 | 5.6 | 3.4 | {7.8.7.6 | 4.5 | 6.7 | 2.3 | 7.8 | 2 | 5.6 | 5.7 | 1 | 9 | | | + | | | | {8.7.9 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 31- 40 | 5.6 | 3.4 | 7.7.6.8.9 | 4.5 | 6.7 | 3 | 6.7.8 | 2 | 6 | 6.7 | 3 | 7 | 4 |16 | 1: 4.00 + 23 | 41- 50 | 5.6 | 3.4 | 7.8.9 | 4.5 | 6.7 | 2.3 | 6.7.8 | 2 | 5.6 | 5.6.7 | 1 | 9 | | | + " | 51- 60 | 5.6 | 3.4 | 7.8.9 | 4.5 | 6.7 | 2.3 | 6.8 | 2 | 5.6 | 6.7 | 1 | 9 | 2 |18 | 1: 9.00 + 24 | 61- 70 | 5.6 | 3.4 | 6.8.9 | 4.5 | 5.7 | 2.3 | 6.7.8 | 1.2 | 5.6 | 6.7 | 0 |10 | | | + " | 71- 80 | 5.6 | 3.4 | 6.7.8.9 | 4.5 | 5.7 | 2.3 | 5.7.8 | 2 | 5.6 | 6.7 | 1 | 9 | 1 |19 | 1:19.00 + 25 | 81- 90 | 5.6 | 3.4 | 6.7.8.9 | 5 | 5.6.7 | 2.3 | 7.8 | 1.2 | 5.6 | 4.5.6.7 | 1 | 9 | | | + " | 91-100 | 5.6 | 3.4 | 6.7.8.9 | 3.4.5 | 6.6.7 | 2.3 | 6.7.8 | 1.2 | 5.6 | 6.7 | 0 |10 | 1 |19 | 1:19.00 + | | | | | | | | | | | | | | | | + 26 | 101-110 | 5.6 | 3.4 | {6.7.8.8 | 3.5 | 5.6.7 | 2.3 | 5.6.7.6.7.8 | 1.2 | 5.6 | 6.7 | 0 |10 | | | + | | | | {6.7.6.9 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + | | | | {6.7.8.8 | | | | | | | | | | | | + " | 111-120 | 5.6 | 2.3.4 | {6.7.8.7 | 3.4.5 | 5.6.7 | 2.3 | 7.8 | 1.2 | 5.6 | 4.5.6.7 | 0 |10 | 0 |20 | 0:20.00 + | | | | {6.7.9* | | | | | | | | | | | | + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + + +[Footnote *: Aided by experimenter.] + + + +The evidence suggests that in this young orang utan ideational learning +tended to replace the simpler mode of problem solution by trial and +error. Seemingly incapable of solving his problems by the lower grade +process, he strove persistently, and often vainly, to gain insight. He +used ideas ineffectively. Animals far lower in intelligence (e.g., the +pig), surpass him in ability to solve these relational problems because +they use the method of elimination by trial consistently and +effectively. Julius, in these experiments, made a poor showing because +his substitute for trial and error is only slightly developed. Would he +have succeeded better with the same problems if mentally mature? + +There are many important features of the results which, for lack of +space, have not been indicated or discussed. They can be developed from +later comparative studies of the data, for in the tables appear all of +the essential facts of response apart from those mentioned in the text. + + + +IV + +RESULTS OF SUPPLEMENTARY TESTS OF IDEATIONAL BEHAVIOR + + +1. Julius, _Pongo pygmaeus_ + + +_Box Stacking Experiment_ + +In addition to the multiple-choice experiments which have been described +in detail in the previous section, it was possible to conduct certain +less systematic tests of ideational behavior in the monkeys and the +orang utan. From the technical standpoint these tests were relatively +unsatisfactory because only inexactly describable. But their results are +in many respects more interesting, if not also more important, in the +light which they throw on ideation than are those previously presented. +First, in order of time, comes a test which may be designated as the box +stacking experiment. The method will now be described in connection with +an account of the behavior of Julius as contrasted with that of a child +of three years and four months of age. + +In the large central cage labelled Z, figure 12, which was twenty-four +feet long, ten feet wide, and ten to twelve feet deep, the following +situation was arranged. From the center of the wire covering of the +cage, a banana was suspended on a string so that it was approximately +six feet from the floor, five feet from either side of the cage, and +twelve feet from either end. From all approaches it was far beyond the +reach of Julius, since it was impossible for him to climb along the wire +roof and thus reach the string. Two boxes were placed on the floor of +the cage several feet from the point directly under the banana. The one +of these boxes was heavy and irregular in shape, as is shown in figures +21, 23 and 24 of plate V. Its greatest height was twenty-one inches; its +least height, eighteen inches; its other dimensions, twelve and sixteen +inches respectively. The smaller and lighter box measured twenty-two by +twelve by ten inches. According to the experimenter's calculations, the +only way in which Julius could obtain the banana was by placing the +smaller box upon the larger and then climbing upon them. + +At 10 a.m. on March 5, Julius was admitted to the large cage, and the +banana was pointed out to him by the experimenter. He immediately set +about trying to get it, and worked diligently during the whole of the +period of observation, which, because of the unfinished condition of +some of the cages, was limited to slightly over ten minutes. Within this +period he made upward of a dozen fairly well directed attempts to obtain +the food. Chief among them were three attempts to reach the banana from +different positions on the left wall of the cage (as the experimenter +faced the laboratory); two attempts to reach it from different positions +on the right wall; two from the large box in positions nearly under the +banana; two from the large box with the aid of the experimenter's hand; +and one from the distant end of the cage(?). There occurred, also, less +definite and easily describable efforts to get at the reward. + +On account of the unfinished condition of the cages, the experimenter +had to remain in the large cage with Julius during the test. This +interfered with the experiment because the animal tended both to try to +escape and to get the experimenter to help him with his task. +Particularly interesting is the latter sort of behavior. After the orang +utan had made two or three futile attempts to obtain the food he came to +the experimenter, who was standing in one corner of the cage, took him +by the hand, and led him to a point directly under the banana. He then +looked up toward the banana, grasped the experimenter's arm, raised it, +and then tried to pull himself up. He was not allowed to get the food by +climbing up on the experimenter. A few minutes later, he again led the +experimenter toward the banana, but receiving discouragement in this +activity, he proceeded to devote himself to other methods. + +Apart from the distractions which have been mentioned above, Julius's +attention to the food was surprisingly constant. Whatever his position +with respect to it, he seemed not for an instant to lose his motive, and +to whatever part of the cage he went and whatever he did during the +interval of observation was evidently guided by the strong desire to +obtain the banana. Frequently he would look directly at it for a few +seconds and then try some new method of reaching it. His gaze was +deliberate and in the handling of the boxes he accurately gauged +distances. Several times he succeeded in placing the larger box almost +directly under the banana, and repeatedly he located that portion of the +side wall from which he could most nearly reach the coveted prize. + + + +EXPLANATION OF PLATE V + +Orang utan, Julius, obtaining banana by piling boxes +or by using pole + +FIGURE 21.--Julius in act of setting larger box on end. + +FIGURE 22.--Placing smaller box on larger. + +FIGURE 23.--Balancing on larger box preparatory to reaching for banana. + +FIGURE 24.--Balancing and reaching to the utmost. + +FIGURE 25.--Standing on three boxes (after stacking them) and +reaching for reward. + +FIGURE 26.--Lifting smaller box up toward banana. + +FIGURE 27.--The act of stacking the boxes. + +FIGURE 28.--Sequel to figure 27. + +FIGURE 29.--Box and pole experiment. Pushing the second pole +into the box. + +FIGURE 30.--Pushing pole into box. + +FIGURE 31.--Enjoying the reward of success. + + + +From my notes I quote the following comment on the results of the +initial experiment: "Despite all that has been written concerning the +intelligent behavior of the orang utan, I was amazed by Julius's +behavior this morning, for it was far more deliberate and apparently +reflective as well as more persistently directed toward the goal than I +had anticipated. I had looked for sporadic attempts to obtain the +banana, with speedy discouragement and such fluctuations of attention as +would be exhibited by a child of two to four years. But in less than ten +minutes Julius made at least ten obvious and well directed attempts to +reach the food. There were also wanderings, efforts to obtain aid from +the experimenter, and varied attempts to escape from the cage." + +Before proceeding further with the description of the behavior of Julius +in the box stacking test, I shall describe for contrast the behavior of +a boy three years four months of age when confronted with a situation +practically identical with that which the ape was given an opportunity +to meet. For the child, the banana was suspended, as previously +described, from the roof of the cage. The same two boxes were placed on +the floor at considerable distances from the banana, and in addition, a +light stick, about six feet long, and a piece of board, the latter by +accident, were on the floor. The child was asked to get the banana for +Julius, and he eagerly and confidently volunteered to do so. + +His behavior may best be described by enumeration of the several +attempts made. They include (1) placing the larger box nearly under the +banana and reaching from it. (2) Standing of the larger box on end with +resulting failure because the child could not stand on the sloping edges +of the top of the box. (3) The larger box was turned on its side and the +lighter box drawn up opposite it and stood on end. The child then +mounted the larger box and from it stepped to the top of the smaller. +But the boxes had not been placed beneath the banana, and when the child +reached for it, he found himself several feet away from his prize. (4) +The boxes were moved to a position nearly under the banana and another +futile attempt was made to reach it without placing the smaller box on +top of the larger one, the only position from which the child could +readily obtain it. (5) The piece of board was placed on top of the +larger box and from this height the child again reached upward. (6) The +six-foot stick was taken up and an attempt was made to strike the banana +and thus dislodge it, but it was too securely fastened to be obtained +thus. (7) Attention shifted to other things, and the child played for a +time with the board. Reminded of the banana by the experimenter, he +again tried method (3). (8) He again used the stick on the banana. (9) +The effort to knock the prize to the floor having failed, he became +discouraged and said that he must go home. (10) When told that Julius +was very hungry and wanted the banana, he repeated efforts similar to +those described in (3) and (6). + +Up to this time the observations had covered a period of twenty minutes. +The child was now taken from the cage and allowed to play about for +fifteen minutes. Asked then whether he would go back and try to get the +banana, he replied, "No, 'cause I don't want to get it," thus indicating +his discouragement with the situation. When taken into the cage, he, +nevertheless, made the additional attempts indicated below: (11) Use of +one of the boxes. (12) He remarked, "Now I know, I'll get it," and after +so saying, repeated (3). (13) Failing, he turned to me and said, "I +could get it if I was on your head," but he did not, as Julius had done, +lead me to the proper place and try to reach the banana by climbing up +or by urging me to lift him. (14) Later, he played in the boxes, +apparently forgetful of his task. Finally he remarked: "I'll get the +banana," but he made no attempt to do so, and instead, watched the +monkeys intently. Thereafter, he showed no further interest in the +solution of the problem, and the experiment, after a total period of +fifty-five minutes, was discontinued. + +Comparison of the behavior of the ape with that of the child indicates a +greater variety of ideas for the latter. Julius gauged his distances +much more accurately than the child, attended more steadily, and worked +more persistently to obtain the reward, but he did not so nearly +approach the idea of stacking the boxes as did the child, for the +latter, in placing the board on one of the boxes, exhibited in +ineffective form the idea which should have yielded the solution of the +problem. + +The child was given no further opportunity to work at the problem, +whereas Julius, as I shall now describe, continued his efforts on +subsequent days under somewhat different conditions. On Wednesday, March +10, the banana was suspended as formerly, and three boxes, all of them +small and light enough to be readily handled by the ape, were placed in +distant parts of the cage. The six-foot stick which had been present in +the test with the child, but not in the first test with Julius, was also +placed in the cage. + +Julius was allowed to work for about an hour. As formerly, he was +sufficiently hungry to be eager to get the food and evidently tried all +of the possible ways which occurred to him. Chief among these were (1) +the use of the various boxes separately or in pairs in very varied +positions but never with one upon another,--the only way in which the +banana could be reached; (2) climbing to various points on the sides of +the cage, with infrequent attempts to reach the banana. Usually his eyes +saved him the vain effort. + +Unlike the child, Julius paid little attention to the six-foot stick. +Two or three times he took it up and seemingly reached for the banana, +but in no case did he try persistently to strike it and knock it from +the string. It is but fair, however, to remark that such an act is very +difficult for the young orang utan, as compared with the child, because +of the weakness of the legs and the awkwardness of striking from a +sitting posture. As previously, the steadiness of attention and the +persistence of effort toward the end in view were most surprising. At +one time Julius walked to the end of the cage and there happened to see +one of the monkeys eating. He watched intently a few seconds and then +hastened back to the banana as if his task had been suggested to him by +the sight of the feeding animal. Most interesting and significant in +this behavior was the suddenness with which he would turn to a new +method. It often looked precisely as though a new idea had come to him, +and he was all eagerness to try it out. + +On March 11, Julius was given another opportunity to obtain the banana +by the use of the three boxes. Although he used them together he made no +effort to place one upon another. Certain of his methods are shown in +plate V, especially by figures 21, 23 and 24. + +This experiment was continued on April 2 under yet different conditions, +for this time only two boxes were placed in the cage, the one of them +the heavy, irregularly-shaped box and the other the smaller, lighter one +originally used. On the end of the heavier box had been nailed a two by +two inch wooden block in order to increase the difficulty in using this +box alone. As previously, Julius made varied attempts to obtain the +banana, but on the whole his interest and attention seemed somewhat +weaker than previously and there were indications of discouragement +because of repeated failures. + +He handled the boxes conspicuously well, and it seemed at times that he +would certainly succeed in placing the one upon the other and in +reaching the food. + +After one series of attempts from the sides of the cage and from the +large box, he deliberately turned away from the box and neatly executed +a somersault on the floor of the cage, as much as to say, "I am +disgusted with the whole situation." Again, later on the same day, after +falling from the top of the larger box, which tilted over very easily, +he rolled himself into a ball, and childlike, played with his feet. An +additional evidence of his changed affective attitude toward his task, +especially in connection with definite failures, appeared in his rough +handling and biting of the boxes. When most impatient, he worked very +roughly. + +Julius was allowed to work for the reward from thirty to ninety minutes, +or, as a rule, until he had become completely discouraged on April 3, 5, +6, 7, 8, 9 and 13. His behavior was interesting and significant, but +nothing new appeared except that his willingness to work gradually +disappeared, and on April 13, although previously hungry, he made only a +single attempt to obtain the banana and then paid no further attention +to it. + +The prolonged and varied efforts to obtain the banana were due in a +measure at least to three accidental successes. Thus on April 2, 3 and +again on the 5th, by fortunate combinations of circumstances, he +succeeded in getting the banana, contrary to the intention of the +experimenter. + +Although active at first on April 6, he soon wearied of his task and +quit work. The same was true on April 7, and again on the 8th and 9th. +On these days, although hungry, he did not care to enter the large cage +and worked only a few minutes each day, seldom making more than two or +three half-hearted attempts to obtain the banana. His attitude toward +the task had changed completely, in that hopelessness had taken the +place of eager expectancy. By the 13th of April he had so nearly given +up voluntary efforts to solve the problem that it seemed worth while to +test his ability to get the idea by watching the experimenter. For this +purpose the following test of imitation was made. + +On the morning of April 14, having placed a banana in the usual +position, I took Julius into the large cage, dragged the two boxes to +the proper position beneath the banana, placed the smaller one upon the +larger one and then climbed up on them to show the ape that I could +reach the banana. I then stepped down and gave him a chance to climb on +the boxes. He did so immediately and obtained the food. + +Another piece of banana was supplied, the boxes were placed in distant +corners of the cage, and fifteen minutes were allowed Julius so to place +them that he could obtain his reward. He gave no indications of having +profited by my demonstration, but worked with the boxes singly, usually +with the larger one. On April 16, with the banana in position and the +two boxes also in the cage, Julius was admitted and allowed to work for +five minutes, but again without success. I then placed the boxes +properly for him and he immediately climbed up and got the banana. While +he was eating, the boxes were carried to distant corners of the cage and +another banana placed in position. Now thirty minutes were allowed him +for unaided work on the problem. As formerly, the larger box was used +repeatedly and attempts to reach from the side of the cage appeared, but +there was no tendency to try to use the two boxes together. He worked +fairly persistently, however, and showed clearly the stimulating and +encouraging effect of aid from the experimenter. Once more, on April 17, +Julius was taken into the cage and allowed to watch me place the boxes +in proper position. He then climbed up and obtained the desired food. +After the bait had been renewed and the boxes displaced, he immediately +tried to use the larger one, then he reached for the small one as though +to use both together. But the impulse died out and he turned again to +the larger box as usual, standing it on end, and persistently trying to +balance himself on it. Nothing else of special interest happened during +the interval of unaided effort. + +Similarly, I placed the boxes for the ape on April 19, allowed him to +get the banana and then gave him opportunity to try for himself after +the boxes had been displaced. This time he immediately reached for the +smaller box and moved it about a little, thus indicating a new +association. He next turned to the larger box and worked with it +persistently. Later, he once more worked with the smaller box in an +unusual manner. He repeatedly stood on it, but made no attempt to lift +it or to place it on the larger box. Clearly the usually neglected +smaller box had become associated with the satisfaction of obtaining the +banana. The same method was carried out on April 20. As I placed the +boxes in position beneath the banana, Julius watched with unusual +intentness, and when it came his turn to try to obtain the food by the +use of the boxes, he began at once to work with the smaller box, but as +on April 19, he soon abandoned it and turned to the other. While I was +making note of this particular feature of his behavior, he suddenly +seized the smaller box by two corners with his hands and by one edge +with his teeth, and after a few attempts placed it on top of the larger +box, climbed up, and obtained the banana. + +Because of bad weather on April 21, the next test was made on April 22, +with everything as usual. Unaided, the ape was given an opportunity to +obtain the coveted reward, while I stood ready to obtain records of his +behavior with my camera. He wasted no time, but piled the smaller box on +top of the larger one immediately, and obtained his reward. As soon as +opportunity was offered, he repeated the performance. The same thing +happened on April 23 and several succeeding dates. + +Julius had got the idea, and the only further improvement possible was +in skill in manipulating the boxes. + +One of the curious performances which appeared during the imitative +period is pictured in figure 26, plate V, where the ape is seen lifting +the smaller box into the air. This he did three or four times one day, +raising it toward the banana each time as though he expected thus to +obtain the reward. As he did not go up with the box (according to his +expectation?), he abandoned this method, and looking about, discovered +the larger box in a distant corner. Thereupon, he promptly pulled the +boxes to their proper position beneath the banana, stacked them, and +obtained his food. + +After considerable skill had been acquired in the placing of the boxes, +the one upon the other, the height of the banana above the floor was +increased so that three boxes were necessary. Figure 25 of plate V shows +him standing on three boxes and reaching upward, and figures 22, 27 and +28 show various modes of handling the boxes and of reaching from them. +He was not at all particular as to the stability of his perch, and often +mounted the boxes when it seemed to the experimenter inevitable that +they should topple over and precipitate him to the floor. Only once, +however, during the several days of experimentation did he thus fall. + +Obviously important is the evident change in the animal's attention on +April 20. He watched with a keenness of interest which betokened a +dawning idea. Before he had succeeded in stacking the boxes, I had +written in my note-book, "He seemed much interested today, in my placing +of the boxes." Interesting, and important also, is the ease and +efficiency with which he met the situation time after time, after this +first success. "Trial and error" had no obvious part in the development +of the really essential features of the behavior. The ape had the idea +and upon it depended for guidance. + +Except for the fact that Julius was immature, probably under five years +of age, it is likely that he would have stacked the boxes spontaneously +instead of by suggestion from the experimenter or imitatively. + +No unprejudiced psychologist would be likely to interpret the activities +of the orang utan in the box-stacking experiment as other than imaginal +or ideational. He went directly, and in the most business-like way from +point to point, from method to method, trying in turn and more or less +persistently or repeatedly, almost all of the possible ways of obtaining +the coveted food. The fact that he did not happen upon the only certain +road to success is surprising indeed in view of the many ineffective +methods which he used. It seemed almost as though he avoided the easy +method. + +It is especially important, in connection with these results, to point +out the risk of misinterpretation of observations on the anthropoid +apes. If they can imitate human activities as readily and effectively as +Julius did in this particular experiment, we can never be sure of the +spontaneity of their ideational behavior unless we definitely know that +they have had no opportunity to see human beings perform similar acts. + +Of all the methods of eliciting ideational or allied forms of behavior +used in my study of the monkeys and ape, none yielded such illuminating +results as the box stacking test, and although from the technical +standpoint, it has many shortcomings, as a means to qualitative results +it has proved invaluable. + + +_Other Methods of Obtaining the Reward_ + +Some weeks later, I tried to discover how Julius would obtain the much +desired banana when the boxes were absent. I placed in the large cage a +stick about six feet long and an old broom. When admitted, he looked +about for the boxes, but not seeing them, picked up the broom and +placing it with the splints down, beneath the banana, he tried to climb +it, but as it fell over with him, he abandoned this after a few trials, +went to his cage, and picking up some old bags which he used at night as +covers, he dragged them out and placed them on the floor beneath the +banana. He next put the broom upon them and tried to climb up. This +general type of behavior persisted for several minutes, everything +within reach being used as were the bags, as a means of raising him in +the desired direction. Finally, he placed his feet on the broom where +the handle joins the splints, seized the handle near the top with his +hands, drew himself up as far as possible, and then launched himself in +the air and tried to seize the banana. On the third attempt he +succeeded. + +Later, he was given a plain stick about five feet long. Figure 32 of +plate VI shows him using this to obtain the banana in the manner +described above. He would grasp it with one or both feet, usually one, +ten to fifteen inches from the floor of the cage, meanwhile holding with +his hands near the top of the stick. He would then, with all his +strength, draw himself up suddenly and jump toward the banana. Often he +came down rather hard on the cement floor, much to his disgust. + +Yet another method of obtaining the reward developed a day or two later. +A light red-wood stick about five feet long and an inch in its other +dimensions was the only object in the cage which could possibly be of +use in obtaining the banana. The aim of the experimenter was to discover +whether Julius would use this as a club. + +Previously, in connection with the use of the boxes, he had taken up the +same stick two or three times and reached for the banana with it, but in +no case had he struck at it or clearly tried to knock it from the +string, as did the child most readily and naturally. When provided with +this same stick, and it alone, as a means of obtaining the food, he hit +upon the following interesting method. Placing one end of the stick +between a wooden brace and the wire side of the cage, he climbed up to a +level with the banana as is shown in figure 33 of plate VI. Then holding +with one hand and one foot to a timber of the cage and to the stick with +his other foot, he swung outward as far as possible and reached the +banana with his free hand. Having once succeeded by the method, he used +it whenever given an opportunity. It was impossible for him to make the +reach without the use of the small stick, while with it he succeeded +fairly easily and regularly. + + +_Box and Pole Experiment_ + +Following the box stacking test, Julius was given an opportunity to +exhibit ideation in another type of experiment. This may be designated +the box and pole test. The conditions are describable thus. A strong +wooden box eighty-four inches long, by four inches wide, by four inches +deep, with open ends, was built with one side hinged. Hasps and padlocks +enabled the experimenter to lock this "lid" after food had been placed +in the center of the box. This box could be placed in the center of the +large cage and there fastened by means of cross bars. It is well shown +in position in figure 29, plate V. Two poles each eight feet long and +approximately one and a half inches in their other dimensions were the +only additional materials in the experiment. + +On May 1, Julius was allowed to see the experimenter place a half banana +in this box, close the lid, lock it in position, and securely fasten the +box by means of the cross bars. He was then given opportunity to try to +get the banana. The two poles lay on opposite sides of the box and near +the edges of the cage. Doctor Hamilton and the writer were in the cage +watching. Julius looked into the box through one end, and seeing the +banana, reached for it. He could not obtain it in this way, so he began +to bite at the box and to pull at it with all his strength. During the +fifteen minutes allowed him, he worked at the box in a great variety of +ways, fooling with the locks which had been attached to the hasps as +well as with the cross bars and continually reaching in at the one or +the other end. He was somewhat distracted by the presence of the two +observers and attended rather unsatisfactorily to the task in hand. Not +once did he touch the poles, and it is doubtful whether he even noticed +them. He was not very hungry at this time, and after a few minutes +active work he virtually gave up trying to get the food. + +Two days later, on May 3, the box was once more placed in position, this +time with a half banana in the middle and a small piece of banana near +each open end. The two poles lay on the floor of the cage, each several +feet distant from the box. Julius was eager for food. When released he +went immediately to the box, reached in and obtained a piece of banana +from the end nearer the laboratory. He then looked in and saw the piece +near the middle of the box. His next move was to pick up the eight foot +pole and push it into the box, but before pushing it all the way +through, he stopped and began to pull at the box in various ways. +Shortly he returned to the pole and twice thrust it in as far as he +could reach. The first time, after thrusting it all the way through, he +pulled it out and examined the end as though expecting the banana to +come out with it. After a third attempt he looked into the box, +presumably seeing the banana, then turned a backward somersault, came to +the end of the cage, and looked at me. Had it been at all possible, he +would have taken me by the hand and led me to the box as a helper. After +a few seconds, he returned to the pole, pried the lid of the box with +it, then gnawed at the pole. For about five minutes he worked fairly +rapidly and steadily, using the poles, pulling, gnawing, and walking +about. + +His next move was to go to the opposite end of the box, look in, take +the piece of banana which was near the opening, then pick up the second +pole, which had not previously been noticed, and after a number of +attempts, push it into and through the box, looking after it and then +pulling it out and looking into the box. Having done this he again came +to my end of the cage, and from there returned to try once more with the +pole which he had first used. He pushed this pole all the way through, +then walked to the other end of the box, looked in and reaching in, +obtained the banana which had been pushed far enough along to be within +his grasp. Figures 29, 30 and 31 of plate V show stages of this process. + +Julius had worked twenty-four minutes with relatively little lost time +before succeeding. He had shown almost from the start the idea of using +the pole as an instrument, and his sole difficulty was in making the +pole serve the desired purpose. + +The experiment was rendered still more crucial on May 5 by the placing +of the two poles upright in opposite corners of the large cage. For a +few minutes after he entered the cage, Julius did not see them, and his +time was spent pulling and gnawing at the box. Then he discovered one of +the poles, seized it, and pushed it into the box. He tried four times, +then went and got the other pole and pushed it into the opposite end of +the box. Twice he did this, then he returned to the original pole, +bringing the second one with him. He pushed it in beside the first, and +as it happened, shoved the banana out of the opposite end of the box. +But he did not see this, and only after several seconds when he happened +to walk to that end of the box did he discover the banana. The total +time until success was fifteen minutes. + +Subsequently the ape became very expert in using the pole to obtain the +banana, and often only a minute or two sufficed for success. It was not +possible for him to direct the stick very accurately, for when he was in +such a position that he could look through the box, he could not work +the stick itself. It was, therefore, always a matter of chance whether +he obtained the banana immediately or only after a number of trials. + +Although it is possible that the use of the poles in this experiment was +due to observation of human activities, it seems probable in the light +of what we know of the natural behavior of the anthropoid apes that +Julius would have solved this problem independently of human influence. +It was the expectation of the experimenter that the pole would be used +to push the banana through the box, but as a matter of fact the ape used +it, first of all, to pull the food toward him, thus indicating a natural +tendency which is important in connection with the statements just made. +Subsequently he learned that the banana must be pushed through and +obtained at the farther end of the box. I am not prepared to accept the +solution of this problem as satisfactory evidence of ideation, but I do +know that few observers could have watched the behavior of the orang +utan without being convinced that he was acting ideationally. + + +_Draw-in Experiment_ + +An interesting contrast with the box and pole test is furnished by what +may be called the draw-in experiment. This was planned as a simple test +of Julius's ability to use a stick to draw things into his cage from +beyond the wire side. A board was placed, as is shown in figure 34 of +plate VI, with sides to hold a banana, carrot, or some other bit of +food, in position. In the actual test either a carrot or a banana was +placed about two feet from the wire netting and a stick two feet long +was then put into the cage with the ape. + +When this situation was first presented to Julius, he looked at the +banana, reached for it, and failing, picked up a bag from the floor of +the cage and tried to push it through the wire mesh toward the banana. +He also used a bit of wire in the same way, but was unable thus to get +the food. As soon as a stick was placed in his cage, he grasped it and +used it in a very definite, although unskillful, way to pull the banana +toward him. He was extremely eager and impatient, but nevertheless +persistent in his efforts, and within five minutes from the beginning of +the first trial, he had succeeded in getting two pieces of banana, using +always his left hand to manipulate the stick. This test was repeated a +number of times with similar results. He had from the first the ability +to use a stick in this way, and the only difficulty with the test as a +means of obtaining evidence of ideational behavior is that the +possibility of imitation of man cannot be certainly excluded. + + +_Lock and Key Test_ + +By my assistant it was reported on May 5 that the orang utan had been +seen to place a splinter of wood in a padlock which was used on the +cages and to work with it persistently. It looked very much like +imitation of the human act of using the key, and I therefore planned a +test to ascertain whether Julius could readily and skillfully use a key +or could learn quickly to do so by watching me. + +The first test was made on May 15 with a heavy box whose hinged lid was +held securely in position by means of a hasp and a padlock. The key, +which was not more than an inch in length, was fastened to a six inch +piece of wire so that Julius could not readily lose it. With the animal +opposite me, I placed a piece of banana in the box, then closed the lid +and snapped the padlock. I next handed Julius the key. He immediately +laid it on the floor opposite him and began biting the box, rolling it +around, and occasionally biting also at the lock and pulling at it. +During these activities he had pulled the box toward his cage. Now he +suddenly looked up to the position where the banana had been suspended +in the box experiment. Evidently the box had suggested to him the +banana. For thirty minutes he struggled with the box almost +continuously, chewing persistently at the hinges, the hasp, or the lock. +Then he took the key in his teeth and tried to push it into one of the +hinges, then into the crack beneath the lid of the box. + +Subsequently I allowed him to see me use the key repeatedly, and as a +result, he came to use it himself now and then on the edge of the box, +but he never succeeded in placing it in the lock, and the outcome of the +experiment was total failure on the part of the animal to unfasten the +lock of his own initiative or to learn to use the key by watching me do +so. I did not make any special attempt to teach him to use the key, but +merely gave him opportunity to imitate, and it is by no means impossible +that he would have succeeded had the key been larger and had the +situation required less accurately coordinated movements. However, it is +fair to say that the evidence of the idea of using the key in the lock +was unconvincing. My assistant's observation was, perhaps, misleading in +so far as it suggested that idea. It may and probably was purely by +accident that the animal used the splinter on the padlock. + + +2. Skirrl, _Pithecus irus_ + + +_Box Stacking Experiment_ + +The monkey Skirrl was tested by means of the box stacking experiment +much as Julius had been. On August 23, with a carrot suspended six feet +from the floor of the large cage and three boxes in distant corners, the +animal was admitted and his behavior noted. + +The boxes, which were made of light, thin material, ranged in size from +one six inches in its several dimensions to one twenty inches long, +thirteen inches wide, and eleven inches deep. Only by using at least two +of these boxes was it possible for the animal to reach the carrot. + +Immediately on admission to the cage, Skirrl began to gnaw at the boxes, +trying with all his might to tear them to pieces. After some thirty +minutes of such effort, interrupted by wanderings about the cage and +attempts to get at the other monkeys, he suddenly went to the largest +box of all, set it up on end almost directly under the carrot, mounted +it, and looked up at the food. It was still beyond his reach and he made +no effort to get it, but instead, he reached from his perch on the big +box for the next smaller box, which was approximately sixteen inches, by +fourteen, by twelve. This he succeeded in pulling toward him, at the +same time raising it slightly from the floor, but his efforts caused the +large box to topple over and he quit work. The experiment was +discontinued after a few minutes, the total period of observation having +been thirty-five minutes. + +Skirrl handled the boxes with ease and with evident pleasure and +interest. He also noticed the carrot at various times during the +interval, but his attention was fixed on it only for short periods. + +The test was continued on August 24 when, instead of a carrot, a half +banana was used as bait. It was placed only five feet from the floor, +and three boxes were as formerly placed in distant corners of the cage. +When admitted, Skirrl looked at the banana, then pulled one of the boxes +toward it, but instead of mounting, he went to the smallest box and +began to gnaw it. Shortly, he mounted the middle sized box and looked up +toward the banana, but the box was not directly under the bait, and in +any event, it would have been impossible for him to reach it. He next +went to the largest box, gnawed it vigorously, turned it over several +times, and then abandoned it for the middle sized box, from which by +skillful use of his teeth and hands, he quickly tore off one side. + +By this time, apparently without very definitely directed effort on the +part of the monkey, all three of the boxes were in the center of the +cage and almost directly beneath the banana. Skirrl climbed up on the +largest box and made efforts to pull the middle sized one up on to it, +the while looking at the banana every few seconds. He did not succeed in +getting the boxes properly placed, and after a time began moving them +about restlessly. + +His behavior plainly indicated that hunger was not his chief motive. He +was more interested in playing with things or in working with them than +in eating, and the satisfaction of tearing a box to pieces seemed even +greater than that of food. It is especially noteworthy that when Skirrl +attempts to dismember a box, instead of starting at random, he searches +carefully for a favorable starting point, a place where a board is +slightly loosened or where a slight crack or hole enables him to insert +his hand or use his teeth effectively. Many times during this experiment +he was observed to examine the boxes on all sides in search of some weak +point. If no such weak point were found, he shortly left the box; but if +he did find a favorable spot, he usually succeeded, before he gave up +the attempt, in doing considerable damage to the box. + +Following the behavior described above, Skirrl returned to the middle +sized box, placed it on end under the banana, mounted, and looked upward +at the bait, but as it was a few inches beyond his reach, he made no +attempt to get it, but instead, after a few seconds, went to the +smallest box, and finding a weak point, began to tear it to pieces. + +Later he rolled what was left of the smallest box close to the other two +boxes, nearly under the banana, and the remainder of his time was spent +gnawing at the boxes and playing with pieces which he had succeeded in +tearing from them. During the remainder of the thirty minute interval of +observation, no further attention was given the bait. + +Again, on August 25, the test was tried, but this time with boxes whose +edges had been bound with tin so that it was impossible for the monkey +to destroy them. He spent several minutes searching for a starting point +on the middle sized box, but finding none, he dragged it under the +banana, looked up, mounted the box, but, as previously, did not reach +for the bait because it was beyond his reach. He then played with the +boxes for several minutes. Finally he worked the two smaller boxes to a +position directly under the banana, put the middle sized one on end, +mounted it, and looked at the bait, but again abandoned the attempt +without reaching. + +During the thirty minutes of observation he made no definite effort to +place one box upon another. Three times he mounted one or another of the +boxes when it was under the banana or nearly so, but in no case was it +possible for him to reach the bait. + +From the above description of this monkey's behavior, it seems fairly +certain that with sufficient opportunity, under strong hunger, he would +ultimately succeed in obtaining the bait by the use of two or more +boxes. For his somewhat abortive and never long continued efforts to +drag two boxes together or to place the one upon the other clearly +enough indicate a tendency which would ultimately yield success. The +possibility of imitation is not excluded, for Skirrl had opportunities +to see Julius and the experimenter handle the boxes. + +Because of the other work which seemed more important at the time, this +experiment was not continued further. The results obtained suggest the +desirability of testing thoroughly the ability of monkeys to use objects +as only the anthropoid apes and man have heretofore been thought capable +of using them. + + +_Box and Pole Experiment_ + +Skirrl was first tested with the box and pole experiment on August 12. +As in the case of Julius, a half banana was placed in the middle of the +long box and the attention of the monkey was attracted to the bait by +small pieces of carrot placed near each open end. Two poles were placed +near the box on the floor of the cage. When admitted to the cage Skirrl +went almost directly to the ends of the box, took the pieces of carrot +which were in sight, but apparently failed to perceive the bait in the +middle of the box. For a while he played with the locks on the box, +shoved it about, and amused himself with it, showing no interest in +obtaining the food. Later he looked through the box and saw the banana. +He then dragged the box about, apparently trying to get it into his +cage, but he gave no attention to the poles nor did he make any evident +effort to obtain the banana which was easily visible in the center of +the box. The period of observation was only twelve minutes. + +On August 24 this experiment was repeated with an important modification +of the apparatus in that the wooden lid of the long box had been +replaced by a wire cover through which the animal could see the bait. +Two poles were as formerly on the floor of the cage, not far from the +box. Skirrl almost immediately noticed the banana and tried to get it by +gnawing at the box. He did not once reach in at the ends of the box, but +he did handle the poles, throwing them about and pounding with them. +There was not the slightest attempt to use them in obtaining the bait. + +This experiment was later repeated three times at intervals of a number +of days, but in no case did Skirrl show any tendency to use the poles as +means of obtaining the food. + + +_Draw-in Experiment_ + +This also was arranged in the same manner as for Julius, and on each of +five days Skirrl was allowed at least thirty minutes to work for the +bait. Either a banana or a carrot was each day placed on the board well +beyond his reach, and one or two, usually two, small sticks were put +into his cage. Not once during the several periods of observation did +Skirrl make any attempt to use a stick or any other object as a means of +drawing the food to him. Instead, he reached persistently with his arm, +pulled and gnawed at the wires which were in his way, and occasionally +picked up and gnawed or pounded with the sticks in the cage. His +attention every now and then would come back to the food, but it tended +to fluctuate rather rapidly, and in the regular period of observation, +thirty minutes, it is unlikely that he attended to the bait itself for +as much as five minutes. In this respect as well as many others, +Skirrl's behavior contrasts sharply with that of the orang utan. + +The results of this experiment indicate the lack in the monkey of any +tendency or ability, apart from training, to use objects as means of +obtaining food. Ways of using objects as tools which apparently are +perfectly natural to the anthropoid apes and to man are rarely employed +by the lower primates. + + +_Hammer and Nail Test_ + +One day I happened to observe Skirrl playing with a staple in his cage. +He had found it on the floor where it had fallen and was intently +prodding himself with the sharp points, apparently enjoying the unusual +sensations which he got from sticking the staple into the skin in +various portions of his body, and especially into the prepuce. + +A few days later I saw him playing in similar fashion with a nail which +he had found, and still later he was seen to be using a stick to pound +the nail with. This suggested to me the hammer and nail test. + +A heavy spike was driven into an old hammer to serve as an +indestructible handle. This hammer, along with a number of large wire +nails and a piece of redwood board, was then placed in the monkey's +cage. Skirrl immediately took up the hammer, grasping the middle of the +handle with his left hand, and with his right hand taking up a nail. He +then sat down on the board, examined the nail, placed the pointed end on +the board, and with well directed strokes by the use of the head of the +hammer drove the nail into the board for the distance of at least an +inch. He then tried to pull it out, but was forced to knock it several +times with the hammer before he could do so. + +This performance, during the next few minutes, was repeated several +times with variations. Often the side of the hammer was used instead of +the head, and occasionally, as is shown in figure 8 of plate II, he +seized the hammer well up toward the juncture of the same with the +spike. This figure does justice to the performance. At the moment the +picture was taken, Skirrl's attention had been attracted by a monkey in +an adjoining cage, and he had momentarily looked up from his task, the +while holding nail and hammer perfectly still. + +This test was repeated on various days, and almost uniformly Skirrl +showed intense interest in hammer and nails and used them more or less +persistently in the manner described. Occasionally, apparently for the +sake of variety, he would put the blunt end of the nail on the board and +hammer on the point. Again, he would try persistently to drive the nail +into the cement floor, and once by accident, when hammer and nails were +left in his cage over night, he succeeded in making several holes in the +bottom of his sheet iron water pan. There was no doubting the keen +satisfaction which the animal took in this form of activity. + +It is impossible to say that the behavior was not imitative of man, for +Skirrl, along with all of the other monkeys, had had abundant +opportunity to see carpenters working. But this much can be said against +the idea of imitation,--no one of the other animals, not excepting the +orang utan, showed any interest whatever in hammer and nails. +Occasionally they would be played with momentarily or pushed about, but +Sobke, Jimmie, Gertie, Julius, although given several opportunities to +exhibit any ability which they might have to drive nails, made not the +least attempt to do so. Evidently we must either conclude that Skirrl +had a peculiarly strong imitative tendency in this direction, or +instead, a pronounced disposition or instinct for the use of objects as +tools. It would seem fair to speak of it as an instinct for mechanical +activity. + +Under this same heading may be described Skirrl's reactions to such +objects as a handsaw, a padlock, and a water faucet. The saw was given +to him in order to test his ability to use it in human fashion, for if +he could so expertly imitate the carpenter driving nails, it seems +likely that he might also imitate the use of the saw. + +As a matter of fact, he showed no tendency to use the saw as we do. +Instead, he persistently played with it in various ways, at first using +it as a sort of plane to scrape with, later often rubbing the teeth over +a board so that they cut fairly well, but never as effectively as in the +hands of a man. After two or three days' practice with the saw, Skirrl +hit upon a method which is, as I understand, used by man in certain +countries, namely, that of placing the saw with the teeth up, holding it +rigid, and then rubbing the object which is to be sawed over it. This +Skirrl succeeded in doing very skillfully, for he would sit down on the +floor of the cage, grip with both feet the handle of the saw, with the +teeth directed upward, then holding either end in his hands, he would +repeatedly rub a stick over the teeth. In this way, of course, he could +make the saw cut fairly well. But still more to his liking was the use +of a spike instead of a stick as an object to rub over the teeth, for +with this he was able to make a noise that would have satisfied even a +small boy. + +Further light is shed on the force of the tendency to imitate man by the +saw test. After Skirrl had been given an opportunity to show what he +could do with the tool spontaneously, I demonstrated to him the approved +human way of sawing. Often he would watch my performance intently as +though fascinated by the sound and motion, but when given the tool he +invariably followed his own methods. Although I repeated this test of +imitation several times on three different days, the results were wholly +negative. + + +_Other Activities_ + +One day as Skirrl was being returned to his own cage by way of the +larger cage, he picked up an unfastened padlock and carried it into the +cage with him. For more than an hour he amused himself almost without +interruption by playing with this lock. The things which he did with it +during that time would require pages to describe. His interest in it was +very similar to that which he had exhibited in hammer and nails, saw, +and indeed any objects which he could play with. The lock was pounded in +various ways, bitten, poked with nails, hooked into the wires of the +cage, used to pull on, pounded with a stick, used to hammer on the floor +of the cage with, and in fine, manipulated in quite as great a variety +of ways as a human being could have discovered. Finally it was hooked to +the side of the cage and snapped shut, and as Skirrl was unable to +dislodge it from this position, he shortly gave up playing with it. + +At the end of the large cage and just outside the wire netting was a +faucet to which a hose was usually attached. The valve could be opened +by turning a wheel-shaped hand piece. Both Skirrl and Julius learned to +turn this wheel in order to get water to play with, but usually the +former's strength was not sufficient to turn on the water. The latter +could do it readily. The indications are that both animals profited by +seeing human beings turn on the water. This unquestionably attracted +their attention to the faucet, and probably by playing with it they +accidentally happened upon the proper movement. At any rate, Skirrl's +behavior was significant in this connection, for he would pick up the +hose to see if water were flowing, and if it were not, he would throw it +down, go directly to the faucet, and try to turn the wheel. The +association of the wheel with the desired flow of water was therefore +definitely established. Shall we describe the act as ideational? It +seems the natural thing to do. + + +3. Sobke, _Pithecus rhesus_ + + +_Box Stacking Experiment_ + +For this test, in the case of Sobke, three light boxes made of redwood +about one-third of an inch thick were used. The smallest, box 1, was six +inches in each direction, the next larger, box 2, was twelve inches, and +the third, box 3, eighteen inches. As in the case of the other animals, +bait, either banana or carrot, was suspended from the middle of the roof +of the large cage at such distance from the floor as to be reached by +the animal only by the use of the boxes. + +The first observations on Sobke were made on June 14. The three boxes +had been placed in the form of a pyramid directly under the banana, +which hung about eighteen inches above the uppermost box. Sobke's +attention while in his cage had been attracted to the bait by seeing me +fastening it in position, but when admitted to the large cage, he simply +glanced at it and then wandered about the cage, picking up bits of food +and struggling to get at the other monkeys. This he did for about five +minutes. He then went to the boxes, placed his hands on top of the +bottom one, but did not climb up on it. A few minutes later he returned +to the box again, climbed up, and readily reached the food, which he ate +while resting on boxes 1 and 2. + +I now replaced the bait and gave the monkey a second chance to obtain +it. Almost immediately he climbed up as far as the second box, but +although he could reach the banana only from the uppermost box, he +deliberately shoved it off to the ground and sat down upon box 2. As he +was unable to obtain the banana from this, he soon began to gnaw and +pull at it, and as he was succeeding all too well in his efforts to tear +the box to pieces, he had to be returned to his cage. + +The most important features of his behavior were, first, his stealthy +and indirect manner, and second, his failure to use other means of +obtaining the bait than that supplied by the observer. Instead of +looking straight at the experimenter, or at the object which he wished +to obtain, he apparently looked and attended elsewhere. For this reason +it was often difficult to decide whether or not he had noticed the bait +or the boxes. Finally I was led to conclude that he usually knew exactly +what was going on and had in his furtive way noted all of the essential +features of the situation, and that his manner was extremely indicative +of his mental attitude of limited trust. Both Julius and Skirrl went to +the opposite extreme in the matter of directness, or as we should say in +human relations, frankness. They would look the experimenter directly in +the eye, and they usually gazed intently at anything, such for example +as the bait, that interested them. Sobke, even when very hungry, instead +of going directly toward the bait, and trying to obtain it, usually did +various other things as though pretending that he had no interest in +food. + +On the following day, June 15, the three boxes were again placed nearly +under the banana, but this time the two smaller boxes, numbers 1 and 2, +were pushed to the extreme end of the lower box and so far from the bait +that it could not be reached from box 1. It was necessary then for the +animal to push boxes 1 and 2 along on box 3 until they were nearer the +bait. + +Sobke, when admitted to the cage, evidently noticed the banana, but as +formerly, he made no immediate effort to obtain it. After wandering in +search of food and quarreling with the other monkeys for several +minutes, he went to the boxes, pushed the topmost one, number 1, off on +to the floor, and then carried it into his cage where he quickly tore +one side off. He next returned to the large cage, climbed up on box 2, +and he was able, by jumping, to reach and obtain the banana. + +As Sobke was very good at jumping, his new method rendered the box +stacking experiment of uncertain value, since it was next to impossible +so to arrange the spatial relations of bait and boxes that he should be +neither discouraged by too great a distance nor encouraged to jump by +too small a distance. Evidently it would be more satisfactory to +simplify the conditions by trying to discover, first of all, whether he +would use a single box as a means of reaching the reward. + +In pursuance of this idea, I suspended a piece of bread five feet from +the floor of the cage, and a few feet to one side of it, I placed a box +from which it could be reached, or at least easily seized by jumping. +Sobke shortly walked to a point beneath the bait and leaping into the +air, seized it. + +I then replaced the bait, raising it to a height of five feet ten inches +from the floor of the cage. When I had retired, Sobke placed himself in +the proper position beneath, looked up at it, but went away without +jumping for it. During the remaining ten minutes of observation, he paid +no further attention to the bait, having satisfied himself evidently +that it was beyond his reach. + +My use of this test was concluded on June 16 when once more I suspended +a piece of bread six feet from the floor and placed a few feet to one +side the eighteen inch box, number 3, from which had the monkey pushed +it to a point directly under the bread, he could have obtained the food +easily. Sobke noticed the food promptly, and from time to time as he +wandered about, he glanced at it out of the corner of his eye, but not +once did he sit down and look at it steadily and directly as Julius and +Skirrl might have done. + +In the first twenty minutes of observation the monkey made no attempt +either to use the box or to reach the food by jumping. I then placed the +box directly under the bait, and scarcely had I withdrawn from the cage +before Sobke climbed up on it and looked toward the food. He could not +reach it without jumping, and he made no effort to get it. I had left a +second box in the cage,--one which I had been using as a seat. Sobke now +went to this box, placed his hands on it, looked toward the bait, and +then went to a distant part of the cage. No further indications were +obtained during the remainder of the period of observation of interest +in the boxes as possible means of obtaining the desired food. + +It is of course obvious that this experiment was not long enough +continued to justify the conclusion that either Sobke or Skirrl could +not use the boxes or even learn to place one box upon another in order +to obtain the bait. The experiment, like several others which are being +described briefly, was used to supplement the multiple-choice +experiment, and the experimenter's chief interest was to discover the +number and variety of methods which would be used by the animal in +the first few presentations of a situation. It is practically certain +that both of these monkeys would have succeeded ultimately in solving +the problem of obtaining the food had they been left in the cage with a +number of boxes, for Skirrl very early indicated interest in moving the +boxes about, and Sobke showed a tendency in that direction which perhaps +was inhibited partially by his distrust of the experimenter. + + +_Draw-in Experiment_ + +For Sobke, as for Julius and Skirrl, the draw-in test was made by +putting food on a shelf outside the cage, beyond the reach of the +animal, and placing in the cage with the animal one or two sticks long +enough to be used for drawing in the bait. + +Sobke was first given this test on July 24. He tried persistently to +reach the banana with his hand, seized the box which supported the bait, +shook it, picked up one or other of the sticks, and chewed at it +repeatedly, but not once did he make any move to use a stick to draw the +food toward him. + +This experiment was repeated on July 27, 29, 30 and 31, a period of +thirty minutes being allowed on each day for observation. At no time did +Sobke show any inclination to use either a stick or any other object as +a means of reaching the bait. Instead, he confined himself strictly to +the use of hands and teeth. + +This test makes it fairly certain that Sobke had no natural tendency to +use objects as tools. In so far as he attended to things about the cage +or laboratory, it seemed to be rather to play with them in a general way +than to use them ideationally or otherwise for definite purposes. + +The definitely negative result of the draw-in experiment rendered +needless prolonged observation with the box and pole test, whose results +are now to be presented. + + +_Box and Pole Experiment_ + +The eighty-four inch box, previously used for a similar test with +Julius, was presented to Sobke on August 24, the wooden cover having +been replaced by a wire one so that the monkey could readily see the +bait in the middle of the box. Sobke, when admitted to the large cage, +went directly to the box and at once discovered the banana which was +midway between the ends. He evidently desired it. Shortly, he went to +one end of the box and looked in. This he repeated later. He also shook +the box and tried to pull it about and tear it with his teeth, but to +the two poles lying nearby on the floor of the cage he gave not the +slightest attention during a thirty minute period of observation. + +The experiment was not repeated because of more important work. + + +_Other Activities_ + +In more respects than I have taken time to enumerate in the above +descriptions of behavior, the relations of Sobke to objects differed +from those of Skirrl, and still more from those of Julius. Hammer, +nails, saw, stones, sticks, locks, and various other objects received +relatively little attention from Sobke unless they happened to come in +his way; then they were usually pushed aside with but scant notice. +Rarely he would carry something to the shelf of his cage with him, but +as a rule only to lay it down and attend to something else. Skirrl, on +the contrary, attended persistently to anything new in the shape of a +movable object. He was extremely partial to objects which could be +manipulated by him in various ways, and especially to any thing with +which he could make a noise. His interest in hammer and nails, saw, +locks, etc., seemed never to wane. I have seen him play for an hour +almost uninterruptedly with a hammer and a nail, or even with a big +spike which he could use to pry about his cage. In the absence of +anything more interesting, even a staple or a small nail might receive +his undivided attention for minutes at a time. How important is the +species difference in this connection, I have no means to judge, but if +we may not consider these different modes of behavior characteristic of +_P. rhesus_ as contrasted with _P. irus_, we must conclude that +remarkable individual differences exist among monkeys, for whereas +Skirrl is by nature a mechanical genius, Sobke has apparently no such +disposition. I can imagine no more fascinating task than the careful +analytical study of the temperaments of these two animals. Skirrl's +behavior has importantly modified my conception of genius. + + + +V + +MISCELLANEOUS OBSERVATIONS + + +1. _Right- and left-handedness_ + +Several years ago Doctor Hamilton reported to me observations which he +had made on preference for the right or left paw in dogs. He has not, I +believe, published an account of his work. Subsequently, Franz observed +a similar preference in monkeys which, according to his report, exhibit +marked tendency to be right-handed, left-handed, or ambidextrous. + +My own observations, although they are wholly incidental to my other +work, seem worthy of description at this point. I noted, first of all, +that the orang utan Julius tended to use his left hand. He by no means +limited himself to this, but in difficult situations he almost +invariably reached for food or manipulated objects in connection with +food getting with the left hand. Figures 23 and 24 of plate V, show him +reaching for a banana with the left hand. Likewise, figure 34 exhibits +the use of the left hand in the draw-in experiment. + +So marked was Julius's preference for his left hand that I became +interested in observing similar phenomena in the monkeys. Skirrl, when +driving nails, held the hammer with his left hand and the nail with his +right hand. The fact that he never was observed to reverse the use of +the hands is surprising, for other observations indicate that he +preferred the right hand for certain acts. + +Stimulated by the obvious left-handedness, in certain connections, of +Julius and Skirrl, I tested the preference of several of the monkeys in +the following simple way. Standing outside the cage I would hold out a +peanut to a hungry animal, keeping it so far from the cage that the +monkey could barely reach it with its fingers. I noted the hand which +was used to grasp the food. Next I varied the procedure by placing the +peanut on a board in order to make sure that I was not definitely +directing the animal's attention. + +With Sobke the following results were obtained. In forty trials given on +two different days, he reached for and obtained the food each time with +his left hand. Only by holding the bait well toward the right side of +his body was it possible to induce him to use the right hand. So far as +may be judged from these observations and from others in connection with +the experiments, this animal is definitely left-handed. + +With Skirrl the results are strikingly different. As stated above, he +used the hammer consistently with his left hand, but in twenty attempts +to obtain food by reaching, he used his right hand seventeen times and +his left only three times. It was quite as difficult to induce him to +use his left hand for this purpose as it was to induce Sobke to use his +right. We must therefore conclude that Skirrl is right-handed in +connection with certain movements and left-handed in others. + +The monkey named Gertie in the reaching experiment consistently used her +left hand, never once using the right. + +Jimmie, so far as it was possible to make tests with him, also used his +left hand, but it should be said that the results are unsatisfactory +because he was at the time extremely pugnacious and paid attention to +the experimenter rather than to the food. + +Scotty, in the first series of ten trials, used his right hand eight +times, his left twice. In the second series, given the following day, he +used the right hand three times and the left seven times. From this we +should have to infer that he is ambidextrous. + +A female _rhesus_ monkey which had been brought to the laboratory only a +few days previously showed a preference for the right hand by the use of +it fourteen times to six. + +In connection with these data which are, I should repeat, too scanty to +be of any considerable value, I wish to describe my own experience. +Although naturally left-handed, I am by training right-handed to the +extent of having been able to use my hands in writing and in various +other activities equally well at the age of twelve. I am at present +ambidextrous in that there are many things which I do with equal +readiness and skill with either hand. Delicate, exact, and finely +coordinated movements, such as those of writing and using surgical +instruments, I perform always with my left hand while grosser movements +involving the whole hand or arm, I am rather likely to perform with my +right hand. + +It seems not improbable in the light of my own experience that we shall +find some specialization among the lower animals with respect to +preference for right and left hand or arm. I should not be at all +surprised to discover that it is the rule for animals to possess or to +develop readily definite preference for one hand in connection with a +given act of skill and to have quite as definite a preference for the +other hand in connection with a radically different kind of act. + + +2. _Instinct and emotion_ + +Of the many presumably instinctive modes of behavior which were +observed, only those which have to do with social relations seem +especially worth reporting. From among them I shall select for +description a few which have already been referred to in connection with +the experimental observations. + + +_Maternal Instinct_ + +Aspects of the maternal instinct I had opportunity to observe in Gertie, +who on February 27 gave birth to a male infant, I present below the +substance of a previously published note on her behavior (Yerkes, 1915). + +"On February 27 one of the monkeys of our collection gave birth, in the +cages at Montecito, to a male infant. The mother is a _Macacus +cynomolgus rhesus_ (_P. irus rhesus_) who has been described by Hamilton +(1914, p. 298) as 'Monkey 9, Gertie, _M. cynomolgus rhesus_ (_P. irus +rhesus_). Age, 3 years 2 months. (She is now, May 1, 1915, 4 years and 6 +months.) Daughter of monkeys 3 and 10. First pregnancy began September, +1913.' The result of this pregnancy was, I am informed, a still-birth. + +"The second pregnancy, which shall now especially concern us, resulted +likewise in a still-birth. Parturition occurred Saturday night, and the +writer first observed the behavior of the mother the following Monday +morning. In the meantime the laboratory attendant had obtained the data +upon which I base the above statements. + +"At the time of parturition Gertie was in a 6 by 6 by 12 foot out-door +cage containing a small shelter box, with an exceptionally quiet and +gentle male (not the father of the infant) who is designated in +Hamilton's paper as Monkey 28, Scotty. + +"My notes record the following exceptionally interesting and genetically +important behavior. On March 1, when I approached her cage, Gertie was +sitting on the floor with the infant held in one hand while she fingered +its eyelids and eyes with the other. Scotty sat close beside her +watching intently. When disturbed by me the mother carried her infant to +a shelf at the top of the cage. Repeatedly attempts were made to remove +the dead baby, but they were futile because Gertie either held it in her +hands or sat close beside it ready to seize it at the slightest +disturbance. + +"Especially noteworthy on this, the second day after the birth of the +infant, are the male's, as well as the female's, keen interest in the +body and their frequent examinations of the eyes, as if in attempts to +open them. Often, also, the mother searched the body for fleas. + +"Observations were made from day to day, and each day opportunity was +sought to remove the body without seriously frightening or exciting the +female. No such opportunity came, and during the second week the corpse +so far decomposed that, with constant handling and licking by the +adults, it rapidly wore away. By the third week there remained only the +shriveled skin covering a few fragments of bone, and the open skull from +the cavity of which the brain had been removed. This the mother never +lost sight of: even when eating she either held it in one hand or foot, +or laid it beside her within easy reach. + +"Gradually this remnant became still further reduced until on March 31 +there existed only a strip of dry skin about four inches long with a +tail-like appendage of nearly the same length. + +"The male, Scotty, on this date was removed to another cage. Gertie made +a great fuss, jumping about excitedly and uttering plaintive cries when +she discovered that her mate was gone. Whenever I approached her cage +she scurried into the shelter box and stayed there while I was near. +This behavior I never before had observed. It continued for two days. On +April 2, it was noted that she had lost her recently acquired shyness +and she no longer made any attempts to avoid me. As usual, on this date, +she was carrying the remnant about with her. + +"The following day, April 3, Gertie was lured from her cage to a large +adjoining compartment for certain experimental observations. After she +had been returned to her own cage the remnant was noticed on the floor +of the large cage. I picked it up. Gertie evidently noticed my act; for +although at a distance of at least ten feet from me, she made a sharp +outcry and sprang to the side of the cage nearest me. I held the piece +of skin (it looked more like a bit of rat skin than the remains of a +monkey) out to her and she immediately seized it and rushed with it to +the shelf at the top of the cage. + +"Two days later the remnant was missing, and careful search failed to +discover it in the cage. It is probable that Gertie had carelessly left +it lying on the floor whence it was washed out when the cages were +cleaned. On this date Gertie seemed quieter than for weeks previously. + +"Thus it appears that during a period of five weeks the instinct to +protect her offspring impelled this monkey to carry its gradually +vanishing remains about with her and to watch over them so assiduously +that it was utterly impossible to take them from her except by force. + +"After reading this note in manuscript, Doctor Hamilton informed me that +Gertie had behaved toward her first still-birth as toward her second. +And, further, that Grace, a baboon, also carried a still-birth about for +weeks. + +"I am now heartily glad that my early efforts to remove the corpse were +futile, for this record of the persistence of maternal behavior seems to +me of very unusual interest to the genetic psychologist." + + +_Fear_ + +In connection with the multiple-choice experiments Skirrl exhibited what +seemed to be instinctive fear as a result of his unfortunate experience +with nails in the floor of box 1. He seemingly referred his misadventure +to some unseen enemy under the floor, and this in spite of the fact that +he was given abundant opportunity to examine the floor of the box, but +not until after the dangerous nails had been clinched. His long +continued avoidance of the experiment boxes and his still more +persistent hesitancy in entering them, coupled with his almost ludicrous +efforts to see beneath the floor through the holes cut for the staples +on the doors, gave me the impression of superstitious fear of the +unseen. As I watched and recorded his behavior day after day during the +period of most pronounced fear, I could not avoid the thought that the +instinctive fear of snakes had something to do with his peculiar +actions, and although I have never studied either the natural or the +acquired responses of monkeys to snakes, I suspect that lacking such +instinctive equipment, Skirrl would have behaved differently as a result +of the pricks which he received from the nails. It is needless to +redescribe his acquired fear of whiteness as it manifested itself in the +freshly painted apparatus. Accompanying these instructive modes of +response and their emotions are suggestions of peculiarly interesting +problems as well as of modes of attacking them. As a matter of fact, +Skirrl's fear-reactions did much to alter my conception of the +constitution of his mind. I should not have been surprised by the +features of behavior exhibited, but I was by no means prepared for their +persistence, and for the highly emotional attitude toward the particular +situation. Only an organism of complexly constituted nervous system and +fairly highly developed affective life could be expected to respond as +did this monkey. As has been suggested above, I find the appeal to +instinct, modified by experience, a natural mode of accounting for the +unexpected features of Skirrl's behavior. + + +_Sympathy_ + +The instinctive playfulness of the young monkey Tiny contrasted most +strikingly with the more serious, if not more sedate, modes of behavior +of the older individuals. + +During the greater part of my period of observation Tiny was cage-mate +of Scotty, the most calm and apparently lazy of all the monkeys. Tiny +delighted in teasing Scotty, and her varied modes of mildly tormenting +him and of stirring him to pursuit or to retaliation were as interesting +as they were amusing. Her most common trick was to steal up behind him +and pull the hair of his back, or seize his tail with her hands or +teeth. Often when he was asleep she would suddenly run to him, give a +sudden jerk at a handful of hairs, and leap away. He was surprisingly +patient, and I never saw him treat her roughly in retaliation. + +Another of Tiny's favorite forms of amusement was that of trying to stir +up the other monkeys to attacks on one another. She very cleverly did +this by pretending that she herself was being attacked. The instant the +older animals began to show hostility toward one another she would leap +out of the way and watch the disturbance with evident satisfaction. It +was this mode of behavior in the little animal which ultimately provided +opportunity for the observations which I wish now to report as +indicative of sympathetic, possibly I may say altruistic, emotions. + +Tiny was confined with Scotty in a cage adjoining the one in which +Jimmie and Gertie were being kept. The cages were separated by wire +netting of half-inch mesh. + +One morning as I was watching the behavior of the animals in the several +cages, I noticed Tiny dressing with her teeth a wounded finger. It had +evidently been bitten by one of the other animals, in all probability +either by Jimmie or Gertie. Tiny was trimming away the loose bits of +skin very neatly and cleansing the wound. After working at this task for +a few minutes, she quickly climbed up to the shelf near the top of her +cage, and by rushing to the partition wire between the two cages, she +lured Gertie to an attempted attack on her. Gertie sprang up to the +partition, placed her hands on it, with the fingers projecting through +the meshes, and attempted to seize Tiny's fingers with her teeth. But +the latter was too quick for her, and withdrawing her hands, like a +flash seized in her teeth the middle finger of Gertie's left hand. She +then bit it severely and with all her might, at the same time pulling +and twisting violently, often placing the entire weight of her body on +the finger. Her sharp teeth cut to the bone, and it was impossible for +the larger and stronger monkey to tear away. For several seconds this +continued, then Gertie succeeded in escaping, whereupon she at once +retreated to the opposite end of her shelf and proceeded to attend to +her injured finger. She cried, wrung her hands, and from time to time +placed the finger in her mouth as though in an effort to relieve the +pain. By this time Jimmie's attention had been attracted by the +disturbance and he rushed up to the shelf, and facing Gertie, watched +her intently for a few seconds. The look of puzzled concern on his face +was most amusing. Apparently he felt dimly that something in which he +should have intelligent interest was going on, but was unable wholly to +understand the situation. After watching Gertie for a time and trying to +discover what she was doing, which was rendered difficult by her +tendency to turn away from him, in order to shield her injured finger, +he rushed over to the wire partition and made strenuous efforts to seize +Tiny with his hands and teeth. But although she continued close to the +partition and often crowded against it with face and hands flattened on +the wires, he was not able to get hold of her, and after a few vain +attempts he returned to his mate, and again with evident solicitousness +and the most troubled expression, watched her wringing her hands and +chewing or sucking at her injured finger. Shortly he again returned to +the partition and renewed his attempts to seize the young monkey. Thus +he went back and forth from one place of interest to the other several +times, but being unable to achieve anything at either point, he finally +gave up and returned to his breakfast on the floor of the cage. + +I report this incident fully because the behavior of Jimmie was in +marked contrast with the usual behavior of the monkeys. Selfishness +seemed everywhere dominant, while clear indications of sympathetic +emotions were rare indeed. The above is undoubtedly the best evidence of +anything altruistic that I obtained. + +It is possible that Tiny's action was retaliatory, but although it is +practically certain that either Gertie or Jimmie inflicted the wound on +her finger, I of course cannot be sure that the spirit of revenge +stirred her to punish Gertie so severely. Jimmie's part in the whole +affair is, however, perfectly intelligible from our human point of view, +and there seems no reason to doubt that he did experience something like +a feeling of sympathy with his mate, coupled with a feeling of +resentment or anger against Tiny. + + + +VI + +HISTORICAL AND CRITICAL DISCUSSION OF IDEATIONAL BEHAVIOR IN MONKEYS AND +APES + + +It is my purpose in this section to indicate the relations of my work on +monkeys and apes to that of other investigators. Although throughout the +report I have used freely the psychological terms idea and ideation, it +has been my aim to describe the behavior of my animals rather than to +interpret it or speculate concerning its accompaniments. Certain acts I +have designated as ideational simply because they seemed to exhibit the +essential features of what we call ideational behavior in man. Further +study may, and probably will, modify my opinion concerning this matter. +It is of prime importance to analyze ideational behavior so that it may +be accurately described and satisfactorily defined in terms of its +distinguishing characteristics. I had hoped to be able to present a +tentative analysis in this report, but the results of my efforts are so +unsatisfactory that I do not feel justified in publishing them. + +The terms idea and ideation have been used to designate contents of +consciousness which are primarily representative. Nowhere have I +attempted to indicate different types or grades of ideational behavior +and nowhere have I found it necessary to emphasize differences between +image and idea. In general, the acts which I have called ideational have +been highly adaptive, and the learning processes in connection with +which they have appeared have differed strikingly from those of the +selective sort in their abruptness of appearance. + +Extremely interesting and valuable definitions of ideation and +discussions of the characteristics of different sorts of ideas in the +light of original observations on monkeys have been presented by +Thorndike (1901, pp. 1, 2; 1911, p. 174); Kinnaman (1902, p. 200); and +Hobhouse (1915, p. 270). As these authors have contributed importantly +to our knowledge of the behavior of monkeys, their discussions of the +meaning of terms are especially valuable. Serviceable definitions are to +be found, also, in Romanes (1900), Morgan (1906), Washburn (1908), and +Holmes (1911). + + +_Evidences of Ideation in Monkeys_ + +Aside from anecdotal and traveller's notes on the behavior of monkeys +and apes we have only a scanty literature. In fact, the really excellent +articles on the behavior and mental life of these animals may be counted +on one's fingers; and not more than half of these are experimental +studies. I shall, in this brief historical sketch, neglect entirely the +anecdotal literature, since my own work is primarily experimental, and +since its results should naturally be compared with those of other +experimenters. + +Thorndike (1901), the American pioneer in the application of the +experimental method to the study of mind in animals, published the first +notable paper on the psychology of monkeys. His results force the +conclusion that "free ideas" seldom appear in the monkey mind and have a +relatively small part in behavior. That the species of Cebus which he +observed exhibits various forms of ideation he is willing to admit. But +he insists that it is of surprisingly little importance in comparison +with what the general behavior of monkeys as known in captivity and as +described by the anecdotal writers have led us to expect. It is +important to note, however, that Thorndike's observations were limited +to Cebus monkeys which, as contrasted with various old world types, are +now considered of relatively low intelligence. + +In many respects the most thoroughgoing and workmanlike experimental +study of monkeys is that of Kinnaman (1902), who has reported on the +study of various forms of response in _P. rhesus_. He presents valuable +data concerning the learning processes, sensory discrimination, reaction +to number, and to tests of imitation. His results indicate a higher +level of intelligence than that discovered by Thorndike, but this is +almost certainly due to difference in the species observed. Kinnaman +goes so far as to say "We have found evidence, also, of general notions +and reasoning, both of low order" (p. 211). + +The contribution of Hobhouse (1915) to our knowledge of the mental life +of monkeys, although in a measure experimental, is based upon relatively +few and unsystematic observations as contrasted with those of Thorndike +and Kinnaman. It appears, however, that Hobhouse's experiments were +admirably planned to test the ideational capacity of his subjects, and +one can not find a more stimulating discussion of ideation than that +contained in his "Mind in Evolution." The results of his tests made with +a _P. rhesus_ monkey are similar to those of Kinnaman, for almost all of +them indicate the presence and importance of ideas. + +Watson (1908) in tests of the imitative ability of _P. rhesus_ saw +relatively little evidence of other than extremely simple forms of +ideation. But in contrast with his results, those obtained by Haggerty +(1909), in a much more extended investigation in which several species +of monkey were used, obtained more numerous and convincing evidences of +ideation in imitative behavior. Although this author wholly avoids the +use of psychological terms, seeking to limit himself to a strictly +objective presentation of results, it is clear from an unpublished +manuscript (thesis for the Doctorate of Philosophy, deposited in the +Library of Harvard University) that he would attribute to monkeys simple +forms of ideational experience. + +Witmer (1910) reports, in confirmation of Haggerty's results, +intelligently imitative behavior in _P. irus_. + +The work of Shepherd (1910) agrees closely, so far as evidences of +ideation are concerned, with that of Thorndike. He obviously strives for +conservatism in his statements concerning the adaptive intelligence of +his monkeys, all of which belonged to the species _P. rhesus_. At one +point he definitely states that they exhibit ideas of a low order, or +something which corresponds to them. Satisfactory evidences of reasoning +he failed to obtain. + +Franz's (1907, 1911) studies of monkeys, unlike those mentioned above, +have for their chief motive not the accurate description of various +features of behavior but instead knowledge of the functions of various +portions of the brain. His results, therefore, although extremely +interesting and of obvious value to the comparative psychologist, throw +no special light upon the problem of ideation. + +The investigation by Hamilton (1911) of reactive tendencies in _P. +rhesus_ and _irus_ yielded preeminently important data concerning +complex behavior. For the ingenious quadruple-choice method devised by +this observer showed that mature monkeys exhibit fairly adequate types +of response. As Hamilton's interest centered in behavior, he did not +discuss ideation, but this does not prevent the comparison of his data +with those of the present report, and the agreement of his findings with +my own is obvious. + +My work contrasts sharply with that briefly mentioned above in that I +applied systematically and over a period of several months an +experimental method suited to reveal problem solving ability. +Previously, the so-called problem or puzzle-box method had been used as +a means of testing for the presence of ideas. For this I substituted the +multiple-choice method. One of the chief advantages of this new method +is the possibility of obtaining curves of learning for the solution or +attempted solution of relational problems of varying difficultness. I am +confident that these curves of learning will prove far more valuable +than such data as are yielded by the puzzle-box method. + +The Pithecus monkeys, which I studied intensively, yielded relatively +abundant evidences of ideation, but with Thorndike I must agree that of +"free ideas" there is scanty evidence; or rather, I should prefer to +say, that although ideas seem to be in play frequently, they are rather +concrete and definitely attached than "free." Neither in my sustained +multiple-choice experiments nor from my supplementary tests did I obtain +convincing indications of reasoning. What Hobhouse has called articulate +ideas, I believe to appear infrequently in these animals. But on the +whole, I believe that the general conclusions of previous experimental +observers have done no injustice to the ideational ability of monkeys. +It is clearly important, however, that we always should take into +account the species of animal observed, for unquestionably there are +extreme differences in mental development among the monkeys. + +As I view my results in the light of their relations to earlier work, I +am strongly impressed with the importance of the use of improved methods +for the study of complex behavior. The delayed reaction method of +Hunter, the quadruple-choice method of Hamilton, and my multiple-choice +method offer new and promising approaches to forms of activity which +thus far have been only superficially observed. + +The ability exhibited by Skirrl to try a method out and then to abandon +it suddenly is characteristic of animals high in intelligence. Most of +the problems which I presented to my animals would be rated as difficult +by psychologists, for as a rule they involved definite relations and +demanded on the part of the subject both perception of a particular +relation and the ability to remember or re-present it on occasion. + +I was greatly surprised by the slow progress of the monkeys toward the +solution of these problems. It had been my supposition that they would +solve them more quickly than any lower type of mammal, but as a matter +of fact they succeeded less well than did pigs. Their behavior +throughout the work proved that of far greater significance for the +experimenter than the solution of a problem is definite knowledge of the +modes of behavior exhibited from moment to moment, or day to day. This +is true especially of those incidental or accidental modes of response +which so frequently appeared in connection with my work that I came to +look upon them, the surprises of each day, as my chief means of insight. + + +_Evidences of Ideation in Apes_ + +Reliable literature of any sort concerning the behavior and mental life +of the anthropoid apes is difficult to find, and still more rare are +reports concerning experimental studies of these animals. There are, it +is true, a few articles descriptive of tests of mental ability, but even +these are scarcely deserving of being classed as satisfactory +experimental studies of the psychology of the ape. I have the +satisfaction of being able to present in the present report the first +systematic experimental study of any feature of the behavior of an +anthropoid ape. + +Among the most interesting and valuable of the descriptions which may be +classed among accounts of tests of mental ability is Hobhouse's (1915) +study of the chimpanzee. The subject was an untrained animal, so far as +stated, of somewhat unsatisfactory condition because of timidity. +Nevertheless, Hobhouse was able to obtain from him numerous and +interesting responses to novel situations, some of which may be safely +accepted as evidences of ideation of a fairly high order. + +Similar in method and result to the work of Hobhouse is that of Haggerty +(unpublished thesis for the Doctorate of Philosophy, deposited in the +Library of Harvard University). Haggerty's tests of the ability of young +orang utans and chimpanzees to solve simple problems and to use tools in +various ways yielded results which contrast most strikingly with those +obtained in his experimental study of the imitative tendency in monkeys. +His observations, had he committed himself to anything approaching +interpretation, doubtless would have led him to conclusions concerning +the ideational life of these animals very similar to those of Hobhouse. + +Koehler, working in the Canary Islands, has, according to information +which I have received from him by letter, made certain experiments with +orang utans and chimpanzees similar to those of Hobhouse and Haggerty. +His results I am unable to report as I have scanty information +concerning them. They are, presumably, as yet unpublished. + +In his laboratory at Montecito, California, Hamilton has from time to +time kept anthropoid apes, but without special effort to investigate +their ideational behavior. He has most interesting and valuable data +concerning certain habits and instincts, all as yet unpublished. + +To a congress of psychologists Pfungst (1912) briefly reported on work +with anthropoid apes in certain of the German zoölogical gardens. His +preliminary paper does not enable one to make definite statements +concerning either his methods or such results as he may have obtained +concerning ideational behavior. So far as I know, he has not as yet +published further concerning his investigation. + +Möbius (1867) has described interesting observations concerning the +mental life of the chimpanzee. But this, like all of the work previously +mentioned, is rather in the nature of casual testing than thoroughgoing, +systematic, and analytic study. + +In addition to the above reports, there are a few concerning the +behavior of apes which have been especially trained for purposes of +exhibition. Most interesting of these is that of Witmer (1909), who +studied in exhibitions and in his own laboratory the behavior of the +chimpanzee Peter. The varied forms of intelligently adaptive behavior +exhibited by this ape convinced Witmer of ideational experience and even +of an approach to reasoning. In his brief report he expresses especial +interest in the possibility of educating this "genius among apes" to the +use of language. + +A chimpanzee named Consul was observed several years ago by Hirschlaff +(1905), and his tricks were interestingly described from the pedagogical +standpoint. + +Similar in character is Shepherd's (1915) brief description of the stage +behavior of Peter and Consul, both chimpanzees. It is impossible to +determine from the account whether these animals are the same as were +observed by both Witmer and Hirschlaff. As no reference is made in +Shepherd's paper to other descriptions of the behavior of these animals +and as he adds nothing to what had already been presented, the reader +obtains no additional light on ideation. + +I have mentioned only samples of the articles on trained anthropoids. +All are necessarily descriptions of the behavior of individuals who had +been trained not for psychological purposes but for the vaudeville +stage, and although such observations unquestionably have certain value +for comparative psychology, it is well known that unless an observer +knows the history of an act, he is not able to evaluate it in terms of +intelligence and is especially prone to overestimate its value as +evidence of ideation. + +There remain studies of the apes, dealing primarily with behavior and +mental characteristics, which are slightly if at all experimental and +deserve to be ranked as naturalistic accounts. Such is, for example, the +book of Sokolowski (1908), in which attention is given to the +characteristics of young as well as fairly mature specimens of the +gorilla, chimpanzee and orang utan. + +The various publications of Garner (1892, 1896, 1900) deal especially +with the language habits of monkeys and apes, but observations bearing +on ideation are reported. + +Wallace (1869) describes certain features of the behavior of an infant +orang utan whose mother he shot in Borneo. He also reports observations +concerning the behavior of adult orang utans, many specimens of which +were shot by him during his travels. + +Early in the last century, Cuvier (1810) interested himself in studies +of the intellectual characteristics of the orang utan, and his data, +taken with those of Wallace, Sokolowski, and others similarly interested +in the natural history of mind, give one a valuable glimpse of the life +of the anthropoid ape. + +Finally, the data brought together by Brehm (1864, 1875, 1888) in his +famous Tierleben; by Darwin (1859, 1871) in "The Origin of Species," and +other works, by Romanes (1900), especially in his books on mental +evolution, by C. Lloyd Morgan (1906) in his several works on comparative +psychology, and by Holmes (1911) in his discussion of the evolution of +intelligence, contribute not unimportantly to our all too meagre +knowledge of the mental life of the anthropoid apes. + +My own results, viewed in the light of what one may learn from the +literature, stand out as unique because of the method of research. Never +before, so far as I have been able to learn, has any ape been subjected +to observation under systematically controlled conditions for so long a +period as six months. Moreover, my multiple-choice method has the merit +of having yielded the first curve of learning for an anthropoid ape. +This fact is especially interesting when one considers the nature of the +particular curve. For so far as one may say by comparing it with the +curves for various learning processes exhibited by other mammals, it is +indicative of ideation of a high order, and possibly of reasoning. I do +not wish to exaggerate the importance of my results, for as contrasted +with what might be obtained by further study, and with what must be +obtained if we are adequately to describe the mind of the orang utan, +they are meager indeed. + +Especially noteworthy, as evidences of ideation, in the results yielded +by the multiple-choice method are (1) the use by the orang utan of +several different methods in connection with each problem; (2) the +suddenness of transition from method to method; (3) the final and +perfect solution of problem I without diminution of the initial errors; +(4) the dissociation of the act of turning in a circle from that of +standing in front of a particular box. + +To these features of behavior others of minor importance might be added. +But as they have been sufficiently emphasized in the foregoing detailed +descriptions, I need only repeat my conclusion, from the summation of +evidence, that this young orang utan exhibited numerous free ideas and +simple thought processes in connection with the multiple-choice +experiment. His ultimate failure to solve the second problem is +peculiarly interesting, although in the light of other features of his +behavior by no means indicative of inferior intelligence. + +The various supplementary experimental tests which I employed are in no +wise importantly distinguished from those used by other observers. The +box stacking experiment has, according to my private information, been +used by Koehler. It is obviously important that such tests be applied in +the same manner to individuals not only of the different genera of +anthropoid apes, but of different ages, sex, and condition of training. + +The box stacking experiment, although it yielded complete success only +as a result of suggestion on my part, proved far more interesting during +its progress than any other portion of my work. In connection with it, +the orang utan exhibited surprisingly diverse and numerous efforts to +meet the demands of the situation. It is fair to characterize him as +inventive, for of the several possible ways of obtaining the banana +which were evident to the experimenter, the ape voluntarily used all but +two or three, and one of these he subsequently used on the basis of +imitation. + +Had Julius been physically and mentally mature, my results would +undoubtedly have been much more impressively indicative of ideas, but +even as matters stand, the survey of my experimental records and +supplementary notes force me to conclude that as contrasted with the +monkeys and other mammals, the orang utan is capable of expressing free +ideas in considerable number and of using them in ways highly indicative +of thought processes, possibly even of the rational order. But +contrasted with that of man the ideational life of the orang utan seems +poverty stricken. Certainly in this respect Julius was not above the +level of the normal three-year-old child. + +In common with other observers, I have had the experience of being +profoundly impressed by the versatility of the ape, and however much I +might desire to disprove the presence of free ideas and simple reasoning +processes in the orang utan, I should feel bound to accept many of the +results of my tests as evidences of such experience. + +I have attempted to indicate briefly the historical setting of my +investigation. I propose, now, in the concluding section, to look +forward from this initial research and to indicate as well as I may in a +few words the possibilities of results important for mankind from the +thorough study of the monkeys and anthropoid apes. + + + +VII + +PROVISION FOR THE STUDY OF THE PRIMATES, AND ESPECIALLY THE MONKEYS AND +ANTHROPOID APES[1] + +[Footnote 1: Much of the material of this section was published +originally in _Science_ (Yerkes, 1916).] + + +I should neglect an important duty as well as waste an opportunity if in +this report I did not call attention to the status of our knowledge +concerning the monkeys and apes and present the urgent need of adequate +provision for the comparative study of all of the primates. + +Although for centuries students of nature have been keenly interested in +the various primates, the information which has been accumulated is +fragmentary and wholly inadequate for generally recognized scientific +and practical needs. There is a voluminous literature on many aspects of +the organization and lives of the monkeys and apes, but when one +searches in it for reasonably connected and complete descriptions of the +organisms from any biological angle, one, is certain to meet +disappointment. + +Concerning their external characteristics we know much; and our +classifications, if not satisfactory to all, are at least eminently +useful. But when one turns to the morphological sciences of anatomy, +histology, embryology, and pathology, one discovers great gaps, where +knowledge might reasonably be expected. Even gross anatomy has much to +gain from the careful, systematic examination of these organisms. With +still greater force this statement applies to the studies of finer +structural relations. Little is known concerning the embryological +development and life history of certain of the primates, and almost +nothing concerning their pathological anatomy. + +Clearly less satisfactory than our knowledge of structure is the status +of information concerning those functional processes which are the +special concern of physiology and pathology. Certain important +experimental studies have been made on the nervous system, but rarely +indeed have physiologists dealt systematically with the functions of +other systems of organs. There are almost no satisfactory physiological +descriptions of the monkeys, anthropoid apes, or lower primates. + + + +SUB-DIVISIONS OF THE ORDER PRIMATES + +_Order_ _Sub-orders_ _Families_ + + ,- a. PROSIMII (Lemurs and Aye-Ayes) + | + | ,- i. Hapalidae (Marmosets) + | | ii. Cebidae (Howling Monkeys, +PRIMATES -+ | Tee Tees, Squirrel Monkeys, + | | Spider Monkeys, and Capuchin + | | Monkeys) + `- b. ANTHROPOIDEA ... -+ iii. Cercopithecidae (Baboons + | and Macaques) + | iv. Simiidae (Gibbons, Orangs, + | Chimpanzees, and Gorillas) + `- v. Hominidae (Man) + + + + +When we turn to the science of genetics we meet a similar condition, for +the literature reveals only scattered bits of information concerning +heredity in the primates. No important experimental studies along +genetic lines have been made with them, and such general observations +from nature as are on record are of extremely uncertain value. Were one +to insist that we know nothing certainly concerning the relation of +heredity in other primates than man, the statement could not well be +disputed. + +Occasionally in recent years students of human diseases have employed +monkeys or apes for experimental tests, but aside from the isolated +results thus obtained, extremely little is known concerning the diseases +peculiar to the various types of infra-human primates or the significant +relations of their diseases to those of man. + +Next in order of extent to our morphological knowledge of these +organisms is that of their behavior, mental life, and social relations. +But certainly no one who is conversant with the behavioristic, +psychological and sociological literature could do otherwise than +emphasize its incompleteness and inadequacy. For our knowledge of +behavior has come mostly from naturalistic observation, scarcely at all +from experimentation; our knowledge of social relations is obviously +meager and of uncertain value; and finally, our knowledge of mind is +barely more than a collection of carelessly drawn inferences. + +This picture of the status of scientific work on the primates, although +not overdrawn, will doubtless surprise many readers, and even the +biologist may find himself wondering why we are so ignorant concerning +the lives of the organisms most nearly akin to us, and naturally of +deepest interest to us. The reasons are not far to seek. Most scientific +investigators are forced by circumstances to work with organisms which +are readily obtained and easily kept. The primates have neither of these +advantages, for many, if not most of them, are expensive to get and +either difficult or expensive to keep in good condition. Clearly, then, +our ignorance is due not to lack of appreciation of the scientific value +of primate research but instead to its difficultness and costliness. + +Strangely enough, the practical importance of knowledge of the primates +has seldom been dwelt upon even by those biologists who are especially +interested in it. It is, therefore, appropriate to emphasize the +strictly human value of the work for which I am seeking provision. + +During the past few years it has been abundantly and convincingly +demonstrated that knowledge of other organisms may aid directly in the +solution of many of the problems of experimental medicine, of +physiology, genetics, psychology, sociology, and economics. In the light +of these results, it is obviously desirable that all studies of +infrahuman organisms, but especially those of the various primates, +should be made to contribute to the solution of our human problems. + +To me it seems that thoroughgoing knowledge of the lives of the +infrahuman primates would inevitably make for human betterment. Through +the science of genetics, as advanced by experimental studies of the +monkeys and anthropoid apes, practical eugenic procedures should be more +safely based and our ability to predict organic phenomena greatly +increased. Similarly, intensive knowledge of the diseases of the other +primates in their relations to human diseases should contribute +importantly to human welfare. And finally, our careful studies of the +fundamental instincts, forms of habit formation, and social relations in +the monkeys and apes should lead to radical improvements in our +educational methods as well as in other forms of social service. + +Along theoretical lines, no less than practical, systematic research +with the primates should rapidly justify itself, for upon its results +must rest the most significant historical or genetic biological +descriptions. It is beyond doubt that genetic psychology can best be +advanced to-day by such work, and what is obviously true of this science +is not less true of all the biological sciences which take account of +the developmental or genetic relations of their events. + +In view of the probable values of increasingly complete accounts of +primate life, it seems far from extravagant to insist that the securing +of adequate provision for systematic and long continued research is the +most important task for our generation of biologists and the one which +we shall be least excusable for neglecting. Indeed, when one stops to +reflect concerning the situation, it seems almost incredible that the +task has not been accomplished. + +Some ten years ago Professor John B. Watson (1906) entered a plea for +the founding of a station for the experimental study of behavior. He +made no special mention of work with the monkeys and apes, but it is +clear from the problems which he enumerates that he would consider them +most important subjects for observation. Professor Watson's plea has +apparently been forgotten by American biologists, and it seems not +inappropriate to revive it at this time. For surely we have advanced +sufficiently along material and scientific lines during the last ten +years to render possible the realization of his hope. + +To my knowledge, only one definite attempt has thus far been made to +gain special provision for the study of the primates. Somewhere about +the year 1912 there was established on Tenerife, one of the Canary +Islands, a modest station for the study of the anthropoid apes. I have +already referred to it briefly on page 1. The plan and purpose of this +station, which is of German origin, have been presented briefly by +Rothmann (1912). From personal communications I know that a single +investigator has been in residence at the station since its founding and +that psychological and physiological results of value have been +obtained, but no published reports have come to my attention. + +When I first heard of the existence of the German anthropoid station I +naturally thought of the possibility of coöperative work, but the events +of the past two years have rendered the chances of cooperation so remote +that it now seems wholly desirable and indeed imperative to seek the +establishment of an American station, which, unlike the German station, +shall provide adequately not only for the study of the anthropoid apes +but for that of all of the lower primates. It should be the function of +such a station or research institute (1) to bring together and correlate +all the information at present available; (2) to fill in existing gaps +observationally and thus complete and perfect our knowledge of these +organisms; (3) to seek to bring all available information to bear upon +the problems of human life. + +Hitherto the unsatisfactoriness of progress has been due to the lack of +a definite plan and program. Every investigator has gone his own way, +doing what little his personal means and opportunity rendered possible. +The time has at last come when concerted action seems feasible as well +as eminently desirable. I am therefore offering a plan and program +which, if wisely developed, should lead ultimately to fairly complete +and practically invaluable knowledge of the lives of all of the +primates. There should be provided in a suitable locality a station or +research institute which should offer adequate facilities (1) for the +maintenance of various types of primate in normal, healthy condition; +(2) for the successful breeding and rearing of the animals, generation +after generation; (3) for systematic and continuous observation under +reasonably natural conditions; (4) for experimental investigations from +every significant biological point of view; (5) for profitable +cooperation with existing biological institutes or departments of +research throughout the world. + +The station should be located in a region whose climate is highly +favorable to the life of many of the lower primates as well as to that +of man. Such a location is by no means easy to find. Because of my +intense interest in the subject, I have, during the past five years, +prospected in various parts of the world for a satisfactory site. I +shall now attempt to indicate the chief requirements and also the +foremost advantages and disadvantages of several regions which have been +considered. It is first of all requisite that the climate be such as to +agree with the organisms to be studied and such, also, as to render +their breeding normal and dependable. Second in importance is its +satisfactoriness for the life and scientific productiveness of the +observer. While certain tropical localities would meet the first +requirement perfectly, they would prove extremely unsatisfactory for +research activity. It therefore seems essential to find a region whose +climate shall reasonably meet the needs of the experimenter while +adequately meeting those of the animals to be studied. + +A further factor which has important bearing upon the productiveness of +the observer is the degree of isolation from civilization and from other +scientific work. No scientist can long work effectively, even in a +reasonably healthy and stimulating climate, if entirely cut off from +similar interests and activities. It is therefore desirable, if at all +possible, to discover a location in the midst of civilization and with +reasonably good opportunities for scientific associations. + +With these several desiderata before us, I shall call attention to a +number of possible sites for a station, several of which I have visited. +Southern California, and especially the portion of the State between +Santa Barbara and San Diego, promises fairly well. It is definitely +known that certain, if not all, species of monkey will breed there +fairly satisfactorily, and although it has not yet been demonstrated, +there is no reason to suppose that in certain regions the anthropoid +apes might not also be kept in perfect health and successfully bred. The +main advantages of this general region are (a) a climate which promises +to be reasonably satisfactory for many if not all of the primates; (b) +admirable climatic conditions for investigators; (c) wholly satisfactory +scientific and cultural environment for the staff of a station. The most +significant disadvantages are (a) a temperature, which is at times a +trifle too low for the comfort of certain of the monkeys and apes. It is +by no means certain, however, that they would not usually adapt +themselves to it. (b) The necessity of importing all of the animals and +of having to rely upon successful acclimatization. Of course it is to be +assumed that importation would be necessary only at the outset of such +work, since the animals later should replenish themselves within the +confines of the station. + +Florida offers possibilities somewhat similar to those of southern +California, but as I have not had opportunity to examine the conditions +myself, I can say only that in view of such information as is available +the advantage seems to be greatly in favor of the latter. + +Cuba, Jamaica, Porto Rico, and for that matter, several of the West +Indies, offer possible sites for a successful station. I have reasonably +intimate personal knowledge only of the conditions in Jamaica. The major +advantages in the West Indies are (a) suitable climatic conditions and +food supply for the animals; and (b) reasonably satisfactory climatic +conditions for the staff. These are, however, more than counterbalanced +in my opinion by the following serious disadvantages: (a) the relative +isolation of the investigators from their fellow scientists; (b) the +necessity of importing all of the animals originally used; (c) the risk +of destruction of the station by storms. + +It is definitely known that anthropoid apes as well as monkeys can be +successfully kept, bred, and reared in the West Indies. During the past +year, on the estate of Doha Rosalia Abreu, near Havana, Cuba, a +chimpanzee was born in captivity. A valuable account of this important +event and of the young ape has been published by Doctor Louis Montané +(1915). It therefore seems practically certain that regions could be +found readily on Jamaica, Porto Rico, or smaller islands, which would be +eminently satisfactory for the breeding of apes. + +There are obvious reasons why an American station for the study of the +primates should be located on territory controlled by the United States +Government, and if a tropical location proves necessary, it would +probably be difficult to find more satisfactory regions, aside from the +inconveniences and risk of importation and the relative isolation of the +investigators, than are available on Porto Rico. + +I have not seriously considered the possibility of locating an American +station on the continent of Africa, for although two of the most +interesting and important of the anthropoid apes, the gorilla and the +chimpanzee, are African forms, while many species of monkey are either +found there or could readily be imported, it has seemed to me that the +islands of the West and East Indies and the portions of the United +States referred to above are much to be preferred over anything +available in Africa. + +In the East, Borneo, the Philippine Islands, and Hawaii are well worth +considering. Borneo is the home of the gibbon and of at least one +species of orang utan, and in addition to these important assets, it +presents the advantages of (a) a wholly suitable climate and food supply +for monkeys and apes; and (b) climatic conditions for investigators +which, I am informed by scientific friends, are nearly ideal. For +investigators the most serious disadvantage here, as in all other parts +of the East, would be the isolation from other scientific work and +workers. + +The possibilities of Central America I considered several years ago when +it seemed to me possible that work might profitably be done with monkeys +and apes on the Canal Zone. The advantages are (a) a climate which +promises fairly well for the animals; and (b) reasonable accessibility +from the United States. The disadvantages are (a) a far from ideal +climate for long continued scientific work; and (b) an environment which +from the cultural and scientific point of view leaves much to be +desired. + +Were a permanent psycho-biological station for the study of the primates +to be established in southern California, it would, even though wholly +satisfactory conditions for the breeding, rearing, and studying of the +animals were maintained, furnish more or less inadequate opportunity for +the observation of the animals under free, natural conditions. It would +therefore be necessary, to supplement the work of such a station by +field work in Borneo, Sumatra, Africa, India, South America, and such +other regions as the species of organism under consideration happen to +inhabit. + +Considering equally the needs of the experimenter and the demands of the +animals, it seems to me reasonable to conclude that southern California +should be definitely proved unsuitable before a more distant site were +selected. For the information which I have been able to accumulate +convinces me that it would in all probability be possible successfully +to breed and keep the primates there, and it is perfectly clear that in +such event the output of a station would be enormously greater because +of the more favorable conditions for research than in any tropical +region or in a more isolated location. + +Assuming that satisfactory provision in the shape of a scientific +establishment for the study of the primates in their relations to man +were available, the following program might be followed: (1) Systematic +and continuous studies of important forms of individual behavior, of +social relations, and of mind; (2) experimental studies of physiological +processes, normal and pathological, and especially of the diseases of +the lower primates, in their relations to those of man; (3) studies of +heredity, embryology, and life history; (4) research in comparative +anatomy, including gross anatomy, histology, neurology, and pathological +anatomy. + +Each of these several kinds of research should be in progress almost +continuously in order that no materials or opportunities for observation +be needlessly wasted. Because of the nature of the work, it would be +necessary to provide, first of all, for those functional studies which +demand healthy and normally active organisms, whose life history is +intimately and completely known. This is true of all studies in +behavior, whether physiological, psychological, or sociological. +Simultaneously with behavioristic observations and often upon the same +individuals, genetic experiments might be conducted. This would be +extremely desirable because of the relatively long periods between +generations. After the usefulness of an animal in behavioristic or +genetic inquiries had been exhausted, it might be made to render still +further service to science in various experimental physiological, or +medical inquiries. And finally, the same individual might ultimately be +used for various forms of anatomical research. Thus, it is clear that +the scientific usefulness of a lemur, a monkey, or an ape might be +maintained at a high level throughout and even beyond the period of its +life history. + +The program thus briefly sketched would provide either directly or +indirectly for work on every aspect of primate life. Especially +important would be the intimacy of interest and cooperation among +investigators, for the comparative method should be applied consistently +and to the limit of its value. The results of various kinds of +observation should be correlated so that there should ultimately emerge +a unitary and practically valuable account of primate life, to replace +the patchwork of information which we now possess. + +Because of the costliness of maintaining and breeding the monkeys and +apes, it is especially desirable that the several kinds of research +mentioned above should be conducted. Indeed, it would seem inexcusably +wasteful to attempt to maintain a primate or anthropoid station for +psychological observations alone, or for any other narrowly limited +biological inquiry. + +Furthermore, the station should be permanent, since for many kinds of +work it would be essential to have intimate knowledge of the life +history and descent of an individual. With the lower primates, a +generation might be obtained in from two to five years; with the higher, +not more frequently, probably, than from ten to fifteen years. It +therefore seems not improbable that the value of the work done in such a +station would continue to increase for many years and would not reach +its maximum short of fifty or even one hundred years. + +A staff of several highly trained and experienced biologists would be +needed. The following organization is suggested as desirable, although, +as indicated below, not necessarily essential in the beginning: (1) An +expert especially interested in the problems of behavior, psychology, +and sociology, with keen appreciation of practical as well as of +theoretical problems; (2) an assistant trained especially in comparative +physiology; (3) an expert in genetics and experimental zoology; (4) an +assistant with training and interests in comparative anatomy, histology, +and embryology; (5) an expert in experimental medicine, who could +conduct and direct studies of the diseases of man as well as of the +lower primates and of measures for their control; (6) an assistant +trained especially in pathology and neurology. + +To this scientific staff of six highly trained individuals there should +be added a business manager, a clerical force of three individuals, a +skilled mechanician, a carpenter, and at least four laborers. + +The annual expenditures of an institute with such a working staff, would +in southern California, approximate fifty thousand dollars. It would +therefore be necessary that it have an endowment of approximately one +million dollars. + +In the absence of this foundation it would, of course, be possible to +make a reasonably satisfactory beginning on the work which has been +outlined in the following less expensive manner. A working plant might +be established, on ground rented or purchased at a low figure, for about +ten thousand dollars; the salary of a director, assistants, a clerical +helper, and combined mechanic and laborer might be estimated at the same +figure; the cost of animals and of maintenance of the plant would +approximate five thousand dollars. Thus, we should obtain as an estimate +of the expenditures for the first year twenty-five thousand dollars. +Without expansion, the work might be conducted during the second year +for fifteen thousand dollars, and subsequently it might be curtailed or +expanded, resources permitting, according as results achieved and in +prospect justified. + +An institute established on such a modest basis as this still might +render largely important scientific service through its own research and +through organized cooperation with other existing research +establishments. Thus, for example, supposing that behavioristic, +psychological, sociological, and genetic inquiries were conducted in the +institute itself, animals might be supplied on a mutually satisfactory +basis to institutes for experimental medicine, for physiological +research, and for anatomical studies. Under such conditions, it is +conceivable that extremely economical and good use might be made of all +the available primate materials. But it is not improbable that even +coöperative research would prove on the whole more profitable, except +possibly in the case of morphological work, if investigators could +conduct their studies in the institute itself rather than in distant +laboratories. In any event, the idea of coöperation should be prominent +in connection with the organization of a research station for the study +of the primates. For thus, evidently, scientific achievement in +connection with these important types of animal might be vastly +increased over what would be possible in a single relatively small +institution with a limited and necessarily specialized staff of workers. + +Despite the fact that biologists generally recognize the importance of +the work under consideration and are eager to have it done, it is +perfectly certain that we shall accomplish nothing unless we devote +ourselves confidently, determinedly and unitedly, with faith, vision, +and enthusiasm, to the realization of a definite plan. Our vision is +clear,--if we are to gather and place at the service of mankind adequate +comparative knowledge of the life of the primates and if we are to make +this possible harvest of scientific results count for human betterment, +we must bend all our efforts to the establishment of a station or +institute for research. + + + +VIII + +BIBLIOGRAPHY + + + +BREHM, A. 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For +example an eBook of filename 10234 would be found at: + + https://www.gutenberg.org/1/0/2/3/10234 + +or filename 24689 would be found at: + https://www.gutenberg.org/2/4/6/8/24689 + +An alternative method of locating eBooks: + https://www.gutenberg.org/GUTINDEX.ALL + + diff --git a/old/10843-8.zip b/old/10843-8.zip Binary files differnew file mode 100644 index 0000000..29db86f --- /dev/null +++ b/old/10843-8.zip diff --git a/old/10843.txt b/old/10843.txt new file mode 100644 index 0000000..cc9bb0d --- /dev/null +++ b/old/10843.txt @@ -0,0 +1,6330 @@ +Project Gutenberg's The Mental Life of Monkeys and Apes, by Robert M. Yerkes + +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: The Mental Life of Monkeys and Apes + A Study of Ideational Behavior + +Author: Robert M. Yerkes + +Release Date: January 27, 2004 [EBook #10843] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK MENTAL LIFE OF MONKEYS *** + + + + +Produced by Michael Oltz and PG Distributed Proofreaders + + + + +The Mental Life of Monkeys and Apes: + A Study of Ideational Behavior + + + ROBERT M. YERKES + Harvard University + + + + + BEHAVIOR MONOGRAPHS + Volume 3, Number 1, 1916 + Serial Number 12 + Edited by JOHN B. WATSON + The Johns Hopkins University + + +WITH SIX PLATES AND FIVE TEXT FIGURES + + + + + + +CONTENTS + + I. Interests, opportunity and materials + + II. Observational problems and methods + + III. Results of multiple-choice experiments: + + 1. Skirrl, _Pithecus irus_ + 2. Sobke, _Pithecus rhesus_ + 3. Julius, _Pongo pygmaeus_ + + IV. Results of supplementary tests of ideational behavior: + + 1. Julius, _Pongo pygmaeus_: + Box stacking experiment + Box and pole experiment + Draw-in experiment + Lock and key test + 2. Skirrl, _Pithecus irus_: + Box stacking experiment + Box and pole experiment + Draw-in experiment + Hammer and nail test + Other activities + 3. Sobke, _Pithecus rhesus_: + Box stacking experiment + Draw-in experiment + Box and pole experiment + Other activities + + V. Miscellaneous observations: + + 1. Right- and left-handedness + 2. Instinct and emotion: + Maternal instinct + Fear + Sympathy + + VI. Historical and critical discussion of ideational behavior in + monkeys and apes: + + 1. Evidences of ideation in monkeys + 2. Evidences of ideation in apes + + VII. Provision for the study of the primates and especially the monkeys + and anthropoid apes + +VIII. Bibliography + + + +I + +INTERESTS, OPPORTUNITY AND MATERIALS + + +Two strong interests come to expression in this report: the one in the +study of the adaptive or ideational behavior of the monkeys and the +apes; and the other in adequate and permanent provision for the thorough +study of all aspects of the lives of these animals. The values of these +interests and of the tasks which they have led me to undertake are so +widely recognized by biologists that I need not pause to justify or +define them. I shall, instead, attempt to make a contribution of fact on +the score of each interest. + +While recognizing that the task of prospecting for an anthropoid or +primate station may in its outcome prove incomparably more important for +the biological and sociological sciences and for human welfare than my +experimental study of ideational behavior, I give the latter first place +in this report, reserving for the concluding section an account of the +situation regarding our knowledge of the monkeys, apes, and other +primates, and a description of a plan and program for the thorough-going +and long continued study of these organisms in a permanent station or +research institute. + +In 1915, a long desired opportunity came to me to devote myself +undividedly to tasks which I have designated above as "prospecting" for +an anthropoid station and experimenting with monkeys and apes. First of +all, the interruption of my academic duties by sabbatical leave gave me +free time. But in addition to this freedom for research, I needed +animals and equipment. These, too, happily, were most satisfactorily +provided, as I shall now describe. + +When in 1913, while already myself engaged in seeking the establishment +of an anthropoid station, I heard of the founding of such an institution +at Orotava, Tenerife, the Canary Islands, I immediately made inquiries +of the founder of the station, Doctor Max Rothmann of Berlin, concerning +his plans (Rothmann, 1912).[1] As a result of our correspondence, I was +invited to visit and make use of the facilities of the Orotava station +and to consider with its founder the possibility of cooeperative work +instead of the establishing of an American station. This invitation I +gratefully accepted with the expectation of spending the greater part of +the year 1915 on the island of Tenerife. But the outbreak of the war +rendered my plan impracticable, while at the same time destroying all +reasonable ground for hope of profitable cooeperation with the Germans in +the study of the anthropoids. In August, 1915, Doctor Rothmann died. +Presumably, the station still exists at Orotava in the interests of +certain psychological and physiological research. So far as I know, +there are as yet no published reports of studies made at this station. +It seems from every point of view desirable that American psychologists +should, without regard to this initial attempt of the Germans to provide +for anthropoid research, further the establishment of a well equipped +American station for the study not only of the anthropoid apes but of +all of the lower primates. + +[Footnote 1: See bibliography at end of report.] + +In the early months of the war while I was making every effort to obtain +reliable information concerning conditions in the Canary Islands, I +received an urgent invitation from my friend and former student, Doctor +G. V. Hamilton, to make use of his collection of animals and laboratory +at Montecito, California, during my leave of absence from Harvard. This +invitation I most gladly accepted, and in February, 1915, I established +myself in Santa Barbara, in convenient proximity to Doctor Hamilton's +private laboratory where for more than six months I was able to work +uninterruptedly under nearly ideal conditions. + +Doctor Hamilton without reserve placed at my disposal his entire +collection of animals, laboratory, and equipment, provided innumerable +conveniences for my work, and in addition, bore the entire expense of my +investigation. I cannot adequately thank him for his kindness nor make +satisfactory acknowledgment here of his generous aid. Thanks to his +sympathetic interest and to the courtesy of the McCormick family on +whose estate the laboratory was located, my work was done under wholly +delightful conditions, and with assistance from Ramon Jimenez and Frank +Van Den Bergh, Jr., which was invaluable. The former aided me most +intelligently in the care of the animals and the construction of +apparatus; and the latter, especially, was of very real service in +connection with many of my experiments. + +The collection of animals which Doctor Hamilton placed at my disposal +consisted of ten monkeys and one orang utan. The monkeys represented +either _Pithecus rhesus_ Audebert (_Macacus rhesus_), _Pithecus irus_ F. +Cuvier (_Macacus cynomolgos_), or the hybrid of these two species +(Elliot, 1913). There were two eunuchs, five males, and three females. +All were thoroughly acclimated, having lived in Montecito either from +birth or for several years. The orang utan was a young specimen of +_Pongo pygmaeus_ Hoppius obtained from a San Francisco dealer in +October, 1914 for my use. His age at that time, as judged by his size +and the presence of milk teeth, was not more than five years. So far as +I could discover, he was a perfectly normal, healthy, and active +individual. On June 10, 1915, his weight was thirty-four pounds, his +height thirty-two inches, and his chest girt twenty-three inches. On +August 18 of the same year, the three measurements were thirty-six and +one-half pounds, thirty-three inches, and twenty-five inches. + +For the major portion of my experimental work, only three of the eleven +animals were used. A growing male, _P. rhesus_ monkey, known as Sobke; a +mature male, _P. irus_, called Skirrl; and the young orang utan, which +had been named Julius. Plates I and II present these three subjects of +my experiments in characteristically interesting attitudes. In plate I, +figure 1, Julius appears immediately behind the laboratory seated on a +rock, against a background of live oaks. This figure gives one an +excellent idea of the immediate environment of the laboratory. Figure 2 +of the same plate is a portrait of Julius taken in the latter part of +August. By reason of the heavy growth of hair, he appeared considerably +older as well as larger at this time than when the photograph for figure +1 was taken. In plate II, figure 3, Julius is shown in the woods in the +attitude of reaching for a banana, while in figure 4 of the same plate +he is represented as walking upright in one of the cages. + +Likenesses of Sobke are presented in figures 5 and 6 of plate II. In the +latter of these figures he is shown stretching his mouth, apparently +yawning but actually preparing for an attack on another monkey behind +the wire screen. Figure 7 of this plate indicates Skirrl in an +interesting attitude of attention and with an obvious lack of +self-consciousness. The same monkey is represented again in figures 8 +and 9 of plate II, this time in the act of using hammer and saw. + + +EXPLANATION OF PLATE II + + +FIGURE 3.--Orang utan, Julius, reaching for banana. + +FIGURE 4.--Julius walking across his cage. + +FIGURE 5.--_P. rhesus_, Sobke. + +FIGURE 6.--Sobke stretching his jaws (yawn?) preparatory to a fight. + +FIGURE 7.--_P. irus_, Skirrl. + +FIGURE 8.--Skirrl using hammer and nail. + +FIGURE 9.--Skirrl using a saw. + + + +All of the animals except the orang utan had been used more or less for +experiments on behavior by Doctor Hamilton, but this prior work in no +way interfered with my own investigation. Doctor Hamilton has +accumulated a large mass of the most valuable and interesting +observations on the behavior of monkeys, and he more thoroughly +understands them than any other observer of whom I have knowledge. Much +to my regret and embarrassment in connection with the present report, he +has thus far published only a small portion of his data (Hamilton, 1911, +1914). In his most recent paper on "A study of sexual tendencies in +monkeys and baboons," he has given important information concerning +several of the monkeys which I have observed. For the convenience of +readers who may make use of both his reports and mine, I am designating +the animals by the names previously given them by Hamilton. The +available and essential information concerning the individuals is +presented below. + + + +_List of animals in collection_ + +Skirrl. _Pithecus irus_. Adult male. + +Sobke. _P. rhesus_. Young adult male. + +Gertie. _P. irus-rhesus_. Female. Born November, 1910. + +Maud. _P. rhesus_. Young adult female. + +Jimmy II. _P. irus_. Adult male. + +Scotty. _P. irus_ (?). Adult male. + +Tiny. _P. irus-rhesus_. Female. Born August, 1913. + +Chatters. _P. irus_. Adult eunuch. + +Daddy. _P. irus_. Adult eunuch. + +Mutt. _P. irus_. Young adult male. Born August, 1911. + +Julius. _Pongo pygmaeus_. Male. Age, 4 years to 5 years. + + + +When I arrived in Santa Barbara, Doctor Hamilton was about to remodel, +or rather reconstruct, his animal cages and laboratory. This gave us +opportunity to adapt both to the special needs of my experiments. The +laboratory was finally located and built in a grove of live oaks. From +the front it is well shown by figure 10 of plate III, and from the rear, +by figure 11. Its location was in every way satisfactory for my work, +and in addition, the spot proved a delightful one in which to spend +one's time. + + +[Illustration: FIGURE 12.--Ground plan of Montecito laboratory and +cages. Scale 1/120 + +L, laboratory; C, cages; A, experiment room in which multiple-choice +apparatus was installed; B, E, additional rooms for research; D, store +room and shop; Z, large central cage communicating with the eight +smaller cages 1-8.] + + +Figure 12 is a ground plan, drawn to scale, of the laboratory and the +adjoining cages, showing the relations of the several rooms of the +laboratory among themselves and to the nine cages. Although the +construction was throughout simple, everything was convenient and so +planned as to expedite my experimental work. The large room A, adjoining +the cages, was used exclusively for an experimental study of ideational +behavior by means of my recently devised multiple-choice method. +Additional, and supplementary, experiments were conducted in the large +cage Z. Room D served as a store-room and work-shop. + +The laboratory was forty feet long, twenty-two feet wide, and ten feet +to the plate. Each small cage was six, by six, by twelve feet deep, +while the large compartment into which each of the smaller cages opened +was twenty-four feet long, ten feet wide, and twelve feet deep. + + + +II + +OBSERVATIONAL PROBLEMS AND METHODS + + +My chief observational task in Montecito was the study of ideational +behavior, or of such adaptive behavior in monkeys and apes as +corresponds to the ideational behavior of man. It was my plan to +determine, so far as possible in the time at my disposal, the existence +or absence of ideas and the role which they play in the solution of +problems by monkeys and apes. I had in mind the behavioristic form of +the perennial questions: Do these animals think, do they reason, and if +so, what is the nature of these processes as indicated by the +characteristics of their adaptive behavior? + +My work, although obviously preliminary and incomplete, differs from +most of the previous studies of the complex behavior of the infrahuman +primates in that I relied chiefly upon a specially devised method and +applied it systematically over a period of several months. The work was +intensive and quantitative instead of more or less incidental, casual, +and qualitative as has usually been the case. Naturally, during the +course of my special study of ideational behavior observations were made +relative to various other aspects of the life of my subjects. Such, for +example, are my notes on the use of the hands, the instincts, the +emotions, and the natural aptitudes of individuals. It is, indeed, +impossible to observe any of the primates without noting most +interesting and illuminating activities. And although the major portion +of my time was spent in hard and monotonous work with my experimental +apparatus, I found time each day to get into intimate touch with the +free activities of my subjects and to observe their social relations and +varied expressions of individuality. As a result of my close +acquaintance with this band of primates, I feel more keenly than ever +before the necessity of taking into account, in connection with all +experimental analyses of behavior, the temperamental characteristics, +experience, and affective peculiarities of individuals. + +The light which I have obtained on the general problem of ideation has +come, first, through a method which I have rather inaptly named the +multiple-choice method, and second, and more incidentally, through a +variety of supplementary methods which are described in Section IV of +this report. These supplementary methods are simple tests of ideation +rather than systematic modes of research. They differ from my chief +method, among other respects, in that they have been used by various +investigators during the past ten or fifteen years. It was not my aim to +repeat precisely the observations made by others, but instead to verify +some of them, and more especially, to throw additional light on my main +problem and to further the analysis of complex behavior. + +What has been referred to as the multiple-choice method was devised by +me three years ago as a means of obtaining strictly comparable objective +data concerning the problem-solving ability of various types and +conditions of animals. The method was first tried with human subjects in +the Psychopathic Hospital, Boston, with a crude keyboard apparatus +which, however, proved wholly satisfactory as a means of demonstrating +its value. It has since been applied by means of mechanisms especially +adapted to the structure and activities of the organisms, to the study +of the behavior of the crow, pig, rat, and ringdove (Yerkes, 1914; +Coburn and Yerkes, 1915; Yerkes and Coburn, 1915). The method has also +been applied with most gratifying results to the study of the +characteristics of ideational behavior in human defectives,--children, +and adults,--and in subjects afflicted with various forms of mental +disease. It is at present being tried out as a practical test in +connection with vocational guidance and various forms of institutional +examination, such as psychopathic hospital and court examinations. + +As no adequate description of the method has yet been published to which +I can here refer, it will be necessary to present its salient +characteristics along with a description of the special form of +apparatus which was found suitable for use with monkeys and apes. + +The method is so planned as to enable the observer to present to any +type or condition of organism which he wishes to study any one or all of +a series of problems ranging from the extremely simple to the complex +and difficultly soluble. All of the problems, however, are completely +soluble by an organism of excellent ideational ability. For the human +subject, the solution of the easiest problem of all requires almost no +effort, whereas even moderately difficult problems may require many +repetitions of effort and hours or days of application to the task. In +each case, the solution of the problem depends upon the perception of a +certain constant relation among a series of objects to which the subject +is required to attend and respond. Such relations are, for example, +secondness from one end of the group, middleness, simple alternation of +ends, or progressive movement by constant steps from one end of a group +to the other. + +It is possible to present such relational problems by means of +relatively simple reaction-mechanisms. In their essential features, all +of the several types of multiple-choice apparatus designed by the writer +and used either by him or by his students and assistants are the same. +They consist of a series of precisely similar reaction-devices, any one +or all of which may be used in connection with a given observation. +These reaction-mechanisms are so chosen as to be suited to the structure +and action-system of the animal to be studied. For the human being the +mechanism consists of a simple key and the total apparatus is a bank of +keys, with such electrical connections as are necessary to enable the +observer to obtain satisfactory records of the subject's behavior. Let +us suppose the bank of keys, as was actually the case in my first form +of apparatus, to consist of twelve separate reaction-mechanisms; and let +us suppose, further, the constant relation (problem) on the basis of +which the subject is required to react to be that of middleness. It is +evident that in successive trials or experiments the keys must be +presented to the subject in odd groups, the possibilities being groups +of 3, 5, 7, 9, or 11. If for a particular observation the experimenter +wishes to present the first three keys at the left end of the keyboard, +he pushes back the remaining nine keys so that they cannot be operated +and requires the subject to select from the group of three keys the one +which on being pressed causes a signal to appear. It is of course the +clearly understood task of the subject to learn to select the correct +key in the group on first trial. This becomes possible only as the +subject observes the relation of the key which produces the desired +effect to the other keys in the group. On the completion of a subject's +reaction to the group of three keys, a group of seven keys at the +opposite end of the keyboard may, for example, be presented. Similarly, +the subject is required to discover with the minimum number of trials +the correct reaction-mechanism. Thus, time after time, the experimenter +presents a different group of keys so that the subject in no two +successive trials is making use of the same portion of the keyboard. It +is therefore impossible for him to react to spatial relations in the +ordinary sense and manner, and unless he can perceive and appropriately +respond to the particular relation which constitutes the only constant +characteristic of the correct reaction-mechanism for a particular +problem, he cannot solve the problem, or at least cannot solve it +ideationally and on the basis of a small number of observations or +trials. + +For the various infrahuman animals whose ideational behavior has been +studied by means of this method, it has been found eminently +satisfactory to use as reaction-mechanisms a series of similar boxes, +each with an entrance and an exit door. An incentive to the selection of +the right box in a particular test is supplied by food, a small quantity +of which is placed in a covered receptacle beyond the exit door of each +of the boxes. Each time an animal enters a wrong box, it is punished for +its mistake by being confined in that box for a certain period, ranging +from five seconds to as much as two minutes with various individuals or +types of organism. This discourages random, hasty, or careless choices. +When the right box is selected, the exit door is immediately raised, +thus uncovering the food, which serves as a reward. After eating the +food thus provided, the animal, according to training, returns to the +starting point and eagerly awaits an opportunity to attempt once more to +find the reward which it has learned to expect. With this form of the +apparatus, the boxes among which choice may be made are indicated by the +raising (opening) of the front door. + +Since with various birds and mammals the box form of apparatus had +proved most satisfactory, I planned the primate apparatus along similar +lines, aiming simply to adapt it to the somewhat different motor +equipment and destructive tendencies of the monkeys. I shall now briefly +describe this apparatus as it was constructed and used in the Montecito +laboratory. + + + +EXPLANATION OF PLATE IV + +FIGURE 13.--Multiple-choice apparatus, showing observer's bench + and writing stand. +FIGURE 14.--Apparatus as seen from observer's bench. +FIGURE 15.--Entrances to multiple-choice boxes as seen from + the response-compartment. +FIGURE 16.--Apparatus as seen from the rear, showing exit + doors, food receptacles, and covers for same. + + + +The apparatus was built in room A (figure 12), this room having been +especially planned for it with respect to lighting as well as dimensions +and approaches. It was unfortunately impossible to obtain photographs +showing the whole of the apparatus, but it is hoped that the four +partial views of plate IV may aid the reader who is unfamiliar with +previously described similar devices to grasp readily the chief points +of construction. In this plate, figure 13 shows the front of the +complete apparatus, with the alleyway and door by way of which the +experimenter could enter. The investigator's observation-bench and +record-table also appear in this figure, together with weighted cords +used to operate the various doors and the vertically placed levers by +means of which each pair of doors could be locked. Figure 14 is the view +presented to the observer as he stood on the bench or observation stand +of figure 13 and looked over the entire apparatus. Three of the entrance +doors are shown at the right of this figure as raised, whereas the +remainder of the nine entrance doors of the apparatus are closed. Figure +15 is a view of the entrance doors from below the wire roof of the +apparatus. Again, two of the doors are shown as raised, and three +additional ones as closed. The rear of the apparatus appears in figure +16, in which some of the exit doors are closed and others open. In the +latter case, the food receptacles appear, and on the lower part of the +raised doors of the corresponding boxes may be seen metal covers for the +food receptacles projecting at right angles to the doors, while on the +lower edge of each door is an iron staple used to receive a sliding bar +which could be operated from the observer's bench as a means of locking +the doors after they had been closed. The space beyond the exit doors +was used as an alleyway for the return of the animals to the starting +point. + +It will be necessary at various points in later descriptions to refer to +these several figures. But further description of them will be more +readily appreciated after a careful examination of the ground plan of +the apparatus presented as figure 17 In accordance with the labelling of +this figure, the experimenter enters the apparatus room through doorway +16, passes thence through doorways 17 and 10 to the large cage Z, from +which he has direct access to the animals and can bring them into the +apparatus. The multiple-choice mechanism proper, consisting of nine +similar boxes (nine were used instead of twelve as a matter of +convenience of construction, not because this smaller number is +otherwise preferable) is labelled F. These boxes are numbered 1 to 9, +beginning at the left. This numbering was adhered to in the recording of +results throughout the investigation. The other important portions of +the apparatus are the runway D, from which the subject at the +experimenter's pleasure could be admitted through doorway 12 to the +large response-chamber E; the alleyways G, H, and I, by way of which +return to the starting point was possible; the observation bench C, with +its approach step 13; and the observer's writing table A. + +In the construction of this large apparatus, it was necessary to make +provision for the extremely destructive tendencies of monkeys and +anthropoid apes,--hence the apparent cumbersomeness of certain portions. +It was equally necessary to provide for the protection of the observer +and the prevention of escape of the subjects by completely covering the +apparatus and alleyways with a heavy wire netting. + +Each of the eighteen doors of the multiple-choice boxes, and in addition +doors 11, 12, and 15 of the runway D, were operated by the observer from +his bench C by means of weighted window cords which were carried by +pulleys appropriately placed above the apparatus. Each weight was so +chosen as to be just sufficient to hold its door in position after the +experimenter had raised it. For the convenience of the experimenter in +the rapid operation of the twenty-one doors, the weights for the doors +of runway D were painted gray, those for the entrance doors, white, and +those for the exit doors, black. + +In each entrance door, as is shown in figure 15 of plate IV, a window +was cut so that the experimenter might watch the animal after it had +entered a given box, and especially note when it left the box after +having received its reward. This window was covered with wire netting. +No such windows were necessary in the exit doors, but to them were +attached heavy galvanized iron flanges which served to cover the food +receptacles. One of these flanges is labelled o in figure 17. The food +receptacles were provided by boring holes in a 2 by 4 inch timber +securely nailed to the floor immediately outside of the exit doors. Into +these holes aluminum cups fitted snugly, and the iron flanges, when the +doors were closed, fitted so closely over the cups that it was +impossible for the animals to obtain food from them. + + +[Illustration: FIGURE 17.--Ground plan of multiple-choice apparatus in +experiment room A. Scale 1/60 + +A, record stand; C, bench for observer; B, step as approach to C; D, +alleyway leading to E, response-compartment; F, one of the nine (1-9) +similar multiple-choice boxes; G, H, alleyways leading from boxes to +starting point at D; I, alleyway used by experimenter as approach to +rear of apparatus; W, W, windows; P, alleyway; Z, large cage; 16, +entrance to room A; 17, entrance to apparatus and thence via 10 to +cages; 18, entrance to alleyway 1; 11, 15, entrances to D; 12, entrance +to E; 13, entrance door of box 5; 14, exit door of box 5; o, cover for +food receptacle.] + + +As originally constructed, no provision was made in the apparatus for +locking the entrance and exit doors of the several boxes when they were +closed. But as two of the subjects after a time learned to open the +doors from either outside or inside the boxes, it became necessary to +introduce locking devices which could be operated by the experimenter +from the observation bench. This was readily accomplished by cutting +holes in the floor, which permitted an iron staple, screwed to the lower +edge of each door, to project through the floor. Through these staples +by means of a lever for each of the nine boxes, the observer was able to +slide a wooden bar, placed beneath the floor of the room, thus locking +or unlocking either the entrance door, the exit door, or both, in the +case of any one of the nine boxes. + +Since figure 17 is drawn to scale, it will be needless to give more than +a few of the dimensions of the apparatus. Each of the boxes was 42 +inches long, 18 inches wide, and 72 inches deep, inside measurements. +The alleys D, I, and H were 24 inches, and G 30 inches wide, by 6 feet +deep. The doors of the several boxes were 18 inches wide, by 5 feet +high, while those in the alleyways were 24 inches wide by 6 feet high. +The response-compartment E of figure 17 was 14 feet 4 inches, by 8 feet, +by 6 feet in depth. In order that the apparatus might be used with adult +human subjects conveniently, if such use should prove desirable, the +depth throughout was made 6 feet, and it was therefore possible for the +experimenter to walk about erect in it. + +The experimental procedure was briefly as follows: A small quantity of +food having been placed in each of the food cups and covered by the +metal flanges on the exit doors, the experimenter raised door 11 of +figure 17 and then opened door 10 and the door of the cage in which the +desired subject was confined. After the latter, in search of food, had +entered the runway D, the experimenter lowered door 11 to keep it in +this runway, and immediately proceeded to set the reaction-mechanisms +for an experiment (trial). Let us suppose that the first setting to be +tried involved all of the nine boxes. Each of the entrance doors would +therefore be raised. Let us further suppose that the right door is +defined as the middle one of the group. With the apparatus properly set, +the experimenter next raises door 12, thus admitting the animal to the +response-compartment E. Any one of the nine boxes may now be entered by +it. But if any except number 5, the middle member of the group, be +entered, the entrance door is immediately lowered and both the exit and +entrance doors locked in position so that the animal is forced to remain +in the box for a stated period, say thirty seconds. At the expiration of +this time the entrance door is raised and the animal allowed to retrace +its steps and make another choice. When the middle box is chosen, the +entrance door is lowered and the exit door immediately raised, thus +uncovering the food, which the animal eats. As a rule, by my monkeys and +ape the reward was eaten in the alleyway G instead of in the +multiple-choice box. As soon as the food has been eaten, the exit door +is lowered by the experimenter, and the animal returns by way of G and H +to runway D, where it awaits its next trial. + +As rewards, bananas and peanuts were found very satisfactory, and +although occasionally other foods were supplied in small quantities, +they were on the whole less constantly desired than the former. + +Four problems which had previously been presented to other organisms +were in precisely the same form presented to the three primates. These +problems may be described, briefly, by definition of the right reaction +mechanism, thus: problem 1, the first mechanism at the subject's left; +problem 2, the second mechanism at the subject's right (that is, from +the end of the series at the subject's right); problem 3, alternately, +the first mechanism at the subject's left and the first at its right; +problem 4, the middle mechanism of the group. + +It was my intention to present these four problems, in order, to each of +the three animals, proceeding with them as rapidly as they were solved. +But as it happened, only one of the three subjects got as far as the +fourth problem. When observations had to be discontinued, Sobke was well +along with the last, or fourth problem; Skirrl was at work at the third +problem; and Julius had failed to solve the second problem. + +For each of the problems, a series of ten different settings of the +doors was determined upon in advance. These settings differ from those +employed in a similar investigation with the pig only in that the +numbering of the doors is reversed. In the present apparatus, the boxes +as viewed from the front (entrance) are numbered from the left to the +right end, whereas those of the pig apparatus were numbered from the +right end to the left end. + +Below are presented for each of the several problems (1) the numbers of +the settings presented in series; (2) the numbers of the doors open; (3) +the number of doors open in each setting and for the series of ten +settings; and (4) the number of the right door. + + + +PROBLEM 1. First mechanism at left of group + + Doors No. of No. of +Settings open doors open right door + 1..................1.2.3......................3..................1 + 2..................8.9........................2..................8 + 3..................3.4.5.6.7..................5..................3 + 4..................7.8.9......................3..................7 + 5..................2.3.4.5.6..................5..................2 + 6..................6.7.8......................3..................6 + 7..................5.6.7......................3..................5 + 8..................4.5.6.7.8..................5..................4 + 9..................7.8.9......................3..................7 +10..................1.2.3......................3..................1 + -- + Total 35 + + +PROBLEM 2. Second mechanism from the right end of group + + Doors No. of No. of +Settings open doors open right door + 1..................7.8.9......................3..................8 + 2..................1.2.3.4....................4..................3 + 3..................2.3.4.5.6.7................6..................6 + 4..................1.2.3.4.5.6................6..................5 + 5..................4.5.6.7.8..................5..................7 + 6..................1.2.3......................3..................2 + 7..................2.3.4.5....................4..................4 + 8..................1.2.3.4.5.6.7.8.9..........9..................8 + 9..................1.2.3.4....................4..................3 +10..................3.4.5.6.7.8................6..................7 + -- + Total 50 + + +PROBLEM 3. Alternately the first mechanism at the left and the + first at the right end of the group + + Doors No. of No. of +Settings open doors open right door + 1..................5.6.7......................3..................5 + 2..................5.6.7......................3..................7 + 3..................1.2.3.4.5.6................6..................1 + 4..................1.2.3.4.5.6................6..................6 + 5..................4.5.6.7.8..................5..................4 + 6..................4.5.6.7.8..................5..................8 + 7..................2.3.4.5....................4..................2 + 8..................2.3.4.5....................4..................5 + 9..................3.4.5.6.7.8.9..............7..................3 +10..................3.4.5.6.7.8.9..............7..................9 + -- + Total 50 + + +PROBLEM 4. Middle mechanism of the group + + Doors No. of No. of +Settings open doors open right door + 1..................2.3.4......................3..................3 + 2..................5.6.7.8.9..................5..................7 + 3..................1.2.3.4.5.6.7..............7..................4 + 4..................7.8.9......................3..................8 + 5..................4.5.6.7.8..................5..................6 + 6..................1.2.3.4.5.6.7.8.9..........9..................5 + 7..................1.2.3......................3..................2 + 8..................2.3.4.5.6..................5..................4 + 9..................3.4.5.6.7.8.9..............7..................6 +10..................6.7.8......................3..................7 + -- + Total 50 + + + +It was found desirable after a problem had been solved to present a new +and radically different series of settings in order to determine to what +extent the subject had learned to choose the correct door by memorizing +each particular setting. These supplementary observations may be known +as control experiments, and the settings as supplementary settings. In +case of these, as for the original settings, the essential facts are +presented in tabular arrangement. + + + +Settings for Control Experiments + +PROBLEM 1. First at left end + + Doors No. of No. of +Settings open doors open right door + 1..................2.3.4......................3..................2 + 2..................6.7.8.9....................4..................6 + 3..................3.4.5......................3..................3 + 4..................4.5.6.7.8.9................6..................4 + 5..................6.7.8.9....................4..................6 + 6..................1.2.3.4.5..................5..................1 + 7..................2.3.4.5.6.7.8..............7..................2 + 8..................3.4.5.6.7.8................6..................3 + 9..................5.6.7......................3..................5 +10..................1.2.3.4.5.6.7.8.9..........9..................1 + + +PROBLEM 2. Second from right end + + Doors No. of No. of +Settings open doors open right door + 1..................5.6.7.8....................4..................7 + 2..................2.3.4.5.6..................5..................5 + 3..................1.2.3.4.5.6.7.8.9..........9..................8 + 4..................5.6.7......................3..................6 + 5..................1.2.3.4....................4..................3 + 6..................4.5.6......................3..................5 + 7..................2.3.4.5....................4..................4 + 8..................1.2.3......................3..................2 + 9..................1.2.3.4.5.6.7..............7..................6 +10..................2.3.4.5.6.7.8.9............8..................8 + + +PROBLEM 3. Alternate left and right ends + + Doors No. of No. of +Settings open doors open right door + 1..................5.6........................2..................5 + 2..................5.6........................2..................6 + 3..................4.5.6.7.8.9................6..................4 + 4..................4.5.6.7.8.9................6..................9 + 5..................1.2.3.4.5..................5..................1 + 6..................1.2.3.4.5..................5..................5 + 7..................2.3.4.5.6.7................6..................2 + 8..................2.3.4.5.6.7................6..................7 + 9..................3.4.5.6.7.8................6..................3 +10..................3.4.5.6.7.8................6..................8 + + +PROBLEM 4. Middle + + Doors No. of No. of +Settings open doors open right door + 1..................4.5.6.7.8..................5..................6 + 2..................1.2.3......................3..................2 + 3..................1.2.3.4.5.6.7.8.9..........9..................5 + 4..................2.3.4.5.6..................5..................4 + 5..................6.7.8......................3..................7 + 6..................3.4.5.6.7.8.9..............7..................6 + 7..................7.8.9......................3..................8 + 8..................1.2.3.4.5.6.7..............7..................4 + 9..................2.3.4......................3..................3 +10..................3.4.5.6.7..................5..................5 + + + +It was my aim so far as possible to present to a given subject each day +the ten settings under a given problem in order, without interruption. +If for any reason the series of observations had to be interrupted, it +was resumed at the same point subsequently. Occasionally it was found +desirable or necessary to present only five of the series of ten +settings in succession and then to interrupt observations for an +interval of a few minutes or even several hours. But as a rule it was +possible to present the series of ten settings. All things being +considered, it proved more satisfactory to give only ten trials a day to +each subject. Frequently twenty and rarely thirty trials were given on +the same day. In such cases the series of settings was simply repeated. +The only pause between trials was that necessary for resetting the +entrance doors and replenishing the food which served as a reward for +success. + + + +III + +RESULTS OF MULTIPLE-CHOICE EXPERIMENTS + + +1. Skirrl, _Pithecus irus_ + +_Problem 1. First at the Left End_ + + +Systematic work with the multiple-choice apparatus and method described +in the previous section was undertaken early in April with Skirrl, +Sobke, and Julius. The results for each of them are now to be presented +with such measure of detail as their importance seems to justify. + +Skirrl had previously been used by Doctor Hamilton in an experimental +study of reactive tendencies. He proved so remarkably inefficient in the +work that Doctor Hamilton was led to characterize him as feeble-minded, +and to recommend him to me for further study because of his mental +peculiarities. With me he was from the first frank, aggressive, and +inclined to be savage. It was soon possible for me to go into the large +cage, Z, with him and allow him to take food from my hand. He was +without fear of the experimental apparatus and it proved relatively easy +to accustom him to the routine of the experiment. Throughout the work he +was rather slow, inattentive, and erratic. + +Beginning on April 7, I sought to acquaint him with the multiple-choice +apparatus by allowing him to make trips through the several boxes, with +the reward of food each time. Thus, for example, with the entrance and +exit doors of box 7 raised, the monkey was allowed to pass into the +reaction-compartment E and thence through box 7 to the food cup. As soon +as he had finished eating, he was called back to D by the experimenter +and, after a few seconds, allowed, similarly, to make a trip by way of +one of the other boxes. By reason of this preliminary training he soon +came to seek eagerly for the reward of food. + +On April 10 the apparatus was painted white in order to increase the +lightness and thus render it easier for the experimenter to observe the +animal's movements, and when on April 12 Skirrl was again introduced to +it for further preliminary training, he utterly refused to enter the +boxes, giving every indication of extreme fear of the white floors and +even of the sides of the boxes. Finally, the attempts to induce him to +enter the boxes had to be given up, and he was returned to his cage +unfed. The following day I was equally unsuccessful in either driving or +tempting him with food into the apparatus. But on April 14 he was so +hungry that he was finally lured in by the use of food. He cautiously +approached the boxes and attempted to climb through on the sides instead +of walking on the floor. It was perfectly evident that he had an +instinctive or an acquired fear of the white surfaces. As the matter was +of prime importance for the success of my work, I inquired of Doctor +Hamilton, and of the men in charge of the cages, for any incident which +might account for this peculiar behavior, and I learned that some three +months earlier, while the animal cages were being whitewashed, Skirrl +had jumped at one of the laborers who was applying a brush to the +framework of one of the cages and had shaken some lime into his eyes. He +was greatly frightened and enraged. Evidently he experienced extreme +discomfort, if not acute pain, and there resulted an association with +whiteness which was quite sufficient to cause him to avoid the freshly +painted apparatus. + +Having obtained an adequate explanation of this monkey's peculiar +behavior, I proceeded with my efforts to induce him to work smoothly and +rapidly, and on April 15, by covering the floor with sawdust, I so +diminished the influence of the whiteness as to render the preliminary +training fairly satisfactory. At the end of two more days everything was +going so well that it seemed desirable to begin the regular experiment. + +On the morning of April 19, Skirrl was introduced to the apparatus and +given his first series of ten trials on problem 1. This problem demanded +the selection of the first door at the left in any group of open doors. +The procedure was as previously described in that the experimenter +raised the entrance doors of a certain group of boxes, admitted the +animal to the reaction-chamber, punished incorrect choices by confining +the animal for thirty seconds, and rewarded correct choices by raising +the exit door and thus permitting escape and the obtaining of food. The +trials were given in rapid succession, and the total time required for +this first series of ten trials was thirty-five minutes. Skirrl worked +faithfully throughout this interval and exhibited no marked +discouragement. When confined in a box he showed uneasiness and +dissatisfaction by moving about constantly, shaking the doors, and +trying to raise them in order to escape. + +For the series of settings used in connection with problem 1, the reader +is referred to page 18. In the first setting, the doors numbered 1, 2, +and 3, were opened. As it happened, the animal when admitted to the +reaction-chamber immediately chose box l. Having received the reward of +food, he was called back to D, and doors 8 and 9 having been raised in +preparation for the next trial, he was again admitted to the +reaction-chamber. This time he quickly chose box 9 and was confined +therein for thirty seconds. On being released, he chose after an +interval of four minutes, box 8, thus completing the trial. + +As it is highly important, not only in connection with the present +description of behavior, but also for subsequent comparison of the +reactions of different types of organism in this experiment, to present +the detailed records for each trial, tables have been constructed which +offer in brief space the essential data for every trial in connection +with a given problem. + +Table 1 contains the results for Skirrl in problem 1. It is constructed +as follows: the date of a series of trials appears in the first vertical +column; the numbers (and number) of the trials for the series or date +appear in column 2; the following ten columns present respectively the +results of the trials for each of the ten settings. Each number, in +these results, designates a box entered. At the extreme right of the +table are three columns which indicate, first, the number of trials in +which the right box was chosen first, column headed R; and second, the +number of trials in which at least one incorrect choice occurred, column +headed W. In the last column, the daily ratio of these first choices +appears. + +Taking the first line of table 1 below the explanatory headings, we note +on April 19 ten trials, numbered 1 to 10, were given to Skirrl. In trial +1, with setting 1, he chose correctly the first time, and the record is +therefore simply 1. In trial 2, setting 2, he incorrectly chose box 9, +the first time. At his next opportunity, he chose box 8, which was the +right one. The record therefore reads 9.8. In trial 3, setting 3, he +chose incorrectly twice before finally selecting the right box. The +record reads 6.7.3, and so on throughout the ten trials which constitute +a series. The summary for this series indicates three right and seven +wrong first choices, that is, three cases in which the right box was +entered first. The ratio of right to wrong first choices is therefore 1 +to 2.33. Since the total number of doors open in the ten settings is +thirty-five, and since in each of the ten settings one door is +describable as the right door, the probable ratio, apart from the +effects of training, of right to wrong first choices is 1 to 2.50. It is +evident, therefore, that Skirrl in his first series of trials closely +approximated expectation in the number of mistakes. + + + +TABLE 1 + +Results for Skirrl, _P. irus_, in Problem 1 + +========+==========+=========+=========+===========+=============+===========+===========+===========+=============+===========+===========+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | Ratio +Date | of | | | | | | | | | | | R | W | of + | trials | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | R to W +--------+----------+---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- + April | | | | | | | | | | | | | | + 19 | 1- 10 | 1 | 9.8 | 6.7.3 | 9.7 | 6.2 | 7.8.6 | {6.7.7.7 | 4 | 7 | 2.3.3.1 | 3 | 7 | 1:2.33 + | | | | | | | | {6.5 | | | | | | + | | | | | | | | | | | | | | + 20 | 11- 20 | 3.2.1 | 9.8 | 5.3 | 7 | 4.2 | 8.8.6 | 5 | 8.4 | 7 | 3.1 | 3 | 7 | 1:2.33 + 21 | 21- 30 | 3.1 | 8 | 3 | 8.7 | 6.2 | 6 | 5 | 6.4 | 9.7 | 1 | 5 | 5 | 1:1.00 + 22 | 31- 40 | 1 | 9.8 | 3 | 7 | 6.2 | 6 | 6.7.5 | 5.8.4 | 9.8.9.8.7 | 2.1 | 4 | 6 | 1:1.50 + 23 | 41- 50 | 2.3.1 | 8 | 5.7.3 | 7 | 4.2 | 6 | 5 | 7.8.4 | 7 | 3.1 | 5 | 5 | 1:1.00 + 24 | 51- 60 | 1 | 8 | 4.5.7.3 | 9.7 | 5.6.2 | 6 | 6.7.5 | 6.4 | 8.9.7 | 1 | 4 | 6 | 1:1.50 + 26 | 61- 70 | 1 | 8 | 6.7.4.7.3 | 7 | 4.5.6.2 | 6 | 5 | 8.4 | 7 | 3.2.3.1 | 6 | 4 | 1: .67 + 27 | 71- 80 | 3.1 | 8 | 3 | 9.7 | 4.6.2 | 7.6 | 6.5 | 5.8.4 | 7 | 1 | 4 | 6 | 1:1.50 + 28 | 81- 90 | 2.3.1 | 8 | 3 | 7 | 4.5.6.2 | 6 | 5 | 5.8.4 | 7 | 1 | 7 | 3 | 1: .43 + 29 | 91- 100 | 1 | 8 | 3 | 9.7 | 6.2 | 6 | 5 | 4 | 7 | 1 | 8 | 2 | 1: .25 + 30 | 101- 110 | 1 | 8 | 4.3 | 7 | 5.6.2 | 6 | 5 | 4 | 7 | 2.3.1 | 7 | 3 | 1: .43 + May | | | | | | | | | | | | | | + 1 | 111- 120 | 2.3.2.1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: .11 + 3 | 121- 130 | 1 | 8 | 5.6.3 | 7 | 4.5.2 | 6 | 5 | 4 | 7 | 1 | 8 | 2 | 1: .25 +4 and 5 | 131- 140 | 3.2.1 | 8[1] | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: .11 + 5 | 141- 150 | 1 | 8 | 4.3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 | 9 | 1 | 1: .11 +--------+----------+---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- + | | | | | | | | 2.3.4.5 | | | 1.2.3.4.5 | | | + | | 2.3.4 | 6.7.8.9 | 3.4.5 | 4.5.6.7.8.9 | 6.7.8.9 | 1.2.3.4.5 | 6.7.8 | 3.4.5.6.7.8 | 5.6.7 | 6.7.8.9 | | | + | +---------+---------+-----------+-------------+-----------+-----------+-----------+-------------+-----------+-----------+---+---+-------- + 6 | 1- 10 | 2 | 6 | 3 | 4 | 6 | 3.2.1 | 6.2 | 5.6.7.8.3 | 5 | 6.1 | 6 | 4 | 1: .67 +========+==========+=========+=========+===========+=============+===========+===========+===========+=============+===========+===========+===+===+======== + +[Footnote 1: End of series on May 4.] + + + +By reading downward in any particular column of results, one obtains a +description of the changes in the animal's reaction to a particular +setting of the doors. Thus, for instance, in the case of setting 1, +which was presented to the animal in trials numbered 1, 11, 21, and so +on to 141, it is clear from the records that no definite improvement +occurred. But oddly enough, in the case of setting 10, which presented +the same group of open doors, almost all of the reactions are right in +the lower half of the column. For setting 2, it is evident that mistakes +soon disappeared. + +Comparison of the data of table 1 indicates that the number of correct +first choices is inversely proportional to the number of doors in use, +while the number of choices made in a given trial is directly +proportional to the number of doors in use. + +During the first week of work on this problem, Skirrl improved markedly. +His performance was somewhat irregular and unpredictable, but on the +whole the experiment seemed fairly satisfactory. Cold, cloudy, or rainy +days tended to diminish steadiness and to increase the number of +mistakes. Similarly, absence of hunger was unfavorable to continuous +effort to find the right box. + +The period of confinement, as punishment for wrong choices, was +increased from thirty seconds to sixty seconds on April 26. But there is +no satisfactory evidence that this favored the solution of the problem. +Work on May 4 was interrupted by a severe storm, the noise of which so +distracted the monkey that he ceased to work. Consequently, observations +were interrupted on the completion of trial 132, and on May 5, the +series was begun with setting 3. On this date, eighteen trials were +given in succession, and in only one of them did a mistake occur. Since +the ten trials numbered 133 to 142 were correct, Skirrl was considered +to have solved problem 1, and systematic training was discontinued. + +On the following day, as a measure of the extent to which the animal had +learned to select the first door at the left no matter what its position +or the number of doors in the group presented, a control series was +given in which the settings differed from the regular series of +settings. These supplementary settings are presented at the bottom of +table 1 together with the records of reaction in ten trials. + +Since in only six of these ten control settings was the first choice +correct, it is scarcely fair to insist that the animal was reacting on +the basis of an ideational solution of the problem. Rather, it would +seem that he had learned to react to particular settings. A careful +study of all of the data of response, together with notes on the varied +behavior of the animal during the experiments, justifies the statement +that Skirrl's solution of problem 1 was incomplete and unreliable. It +was highly dependent upon the particular situation, or even the +particular door at the left end of the group, and slightly if at all +dependent upon anything comparable to the human idea of first at the +left of the group. + +This particular series of observations has been described and discussed +in some detail in order to make the chief points of method clear. It +will be needless, hereafter, to refer explicitly to many of the +characteristics of reaction or to the important points in the +construction of tables which have been mentioned. + +A graphic representation of Skirrl's learning process in problem 1 is +presented in figure 18. The irregularities are most striking, and fairly +indicate the erraticness of the animal. The curve is based upon the data +in next to the last column of table 1, that is, the column presenting +the errors or wrong first choices in each series of trials. + +Unquestionably, the form of such a curve of learning should be +considered in connection with the method or methods of selecting the +right box employed by the animal during the course of experimentation. +It appears from an analysis of the behavior of Skirrl in problem 1 that +there developed a single definite and persistent method, namely, that of +going to one box in the group, and in case it happened to be a wrong +one, of choosing, on emergence from it, the next toward the right end of +the group, and so on down the line. Having reached the extreme right +end, the tendency was to follow the side of the reaction-chamber around +to the opposite end and to enter the first box at the left end of the +group, which was, of course, the right one. This method appears, with +certain slight variations, in approximately ninety per cent of the +trials which involved incorrect choices. Thus, in the case of trials 121 +to 130, of which eight exhibit right first choices, the remaining two +exhibit the method described above except that the final member at the +right end of the group was in each case omitted. + +[Illustration: FIGURE 18.--Error curves of learning for the solution of +problem 1 (first box at left end).] + +On the whole, Skirrl's behavior in connection with this problem appears +to indicate a low order of intelligence. He persisted in such stupid +acts as that of turning, after emergence from the right box, toward the +right and passing into the blind alley I, instead of toward the left, +through G and H, to D. In contrast with the other animals, he spent much +time before the closed doors of the boxes, instead of going directly to +the open doors, some one of which marked the box in which the reward of +food could be obtained. It is, moreover, obvious that his responses, as +they appear in table 1, are extremely different from those of a human +being who is capable of bringing the idea of first at the left end to +bear upon the problem in question. + + +_Problem 2. Second from the Right End_ + +Following the series of control trials of problem 1 given to Skirrl on +May 6, a period of four days was allowed during which the animal was +merely fed in the boxes each day. This was done in order that he should +partially lose the effects of his previous training to choose the first +box at the left before being presented with the second problem, the +second box from the right. + +On May 11 regular experimentation was begun with problem 2. Naturally +the situation presented unusual difficulties to the monkey because of +his previously acquired habit, and on the first day it was possible to +give only five trials, in all except the first of which Skirrl had to be +aided by the experimenter to find the right box. He persistently, as +appears in the first line of records of table 2, entered the first box +at the left. The series was continued on May 13, but with very +unsatisfactory results, since he apparently had been greatly discouraged +by the unusual difficulties previously met. Only four trials could be +given, and in these the showing made was very poor. It is noteworthy, +however, that in trials 6, 7, and 8, May 13, there was no marked +tendency to choose the first box at the left. Thus quickly had the force +of the previous habit been broken. + +For problem 2, the total number of open doors in the ten settings is +fifty, as appears from the data on page 18, and as ten of these fifty +open doors may be defined as right ones, the expected ratio of right to +wrong first choices in the absence of previous training is 1 to 4. The +actual ratio for the first series given in problem 2 is 1 to 8, while in +the second series it is 0 to 10. + +On the morning of May 13, work was interrupted in the ninth trial by +what seemed at the moment a peculiarly unfortunate accident, but in the +light of later developments, an incident most fruitful of valuable +results. + +Skirrl, in trial 9, directly entered box 1. Since this was not the right +box, he was punished by being confined in it for ten seconds. While in +the box he howled and when the entrance door was raised for him to +retrace his steps, he came out with a rush, showing extreme excitement +and either rage or fear, I could not be sure which. At intervals he +uttered loud cries, which I am now able to identify as cries of alarm. +Repeatedly he went to the open door of box 1 and peered in, or peered +down through the hole in the floor which received the staple on the +door. He refused to enter any one of the open boxes and continued, at +intervals of every half minute or so, his cries. For thirty minutes I +waited, hoping to be able to induce him to complete the series of +trials, but in vain. Although it was obvious that he was eager to escape +from the apparatus, he would not enter any of the boxes even when the +exit doors were raised. Instead, he gnawed at the door (12 in fig. 17) +to the alleyway D and attempted to force his way through, instead of +taking the easy and clear route to the alleys, through one of the boxes. +His behavior was most surprising and puzzling. Finally, I gave up the +attempt to complete the series and returned him to his cage by way of +the entrance door to the response-compartment E. + +I then entered the apparatus to seek some explanation of the animal's +behavior, and my search was rewarded by the finding of two sharp pointed +nails which protruded for an inch or more in the middle of the floor of +box 1. My assistant, who had been charged with the task of installing +the locks for the several doors, had used nails instead of screws for +attaching staples underneath the floor and had neglected to clinch the +nails. Skirrl, in the dim light of the box, doubtless stepped upon one +of the nails and inflicted a painful, although not serious, injury upon +himself. It was impossible for him to see clearly the source of his +injury. He was greatly frightened and expressed the emotion most +vigorously. His behavior strongly suggested a superstitious dread of +some unseen danger. It may be that the instinctive fear of snakes, so +strong in monkeys, was partly responsible for his response. + +The first result of this accident was that more than two weeks were +lost, for it was impossible, during the next few days, to induce the +animal to enter any of the multiple-choice boxes voluntarily. From May +14 to May 24, I labored daily to overcome his newly acquired fear. The +usual procedure was to coax him through one box after another by +standing at the exit door with some tempting morsel of food. After +several days of this treatment, he again trusted himself to the boxes, +although very circumspectly and only when both entrance and exit doors +were raised. Not until May 24 was it possible to resume regular +experimentation, and on that day it was found necessary to indicate the +right box by raising the exit door slightly and then immediately +lowering it. Trials in which this form of aid was given are indicated in +table 2 by a star following the last choice. + +Gradually, Skirrl regained his confidence in the apparatus and began to +work more naturally. For a long time he would not stand punishment, and +it was necessary for the experimenter to be very careful in locking the +doors, since the sound of the bar sliding beneath the floor often +frightened and caused him to quit work. Day after day the tendency to +peer through the holes in the floor at the entrance to the boxes +rendered it clear that the animal feared some danger from beneath the +floor. This behavior was so persistent that much time was wasted in the +experiments. + +On the last day of May, punishment by confinement for ten seconds in +wrong boxes was introduced, but since this tended to discourage the +monkey, there was substituted for it on June 1 the punishment of forcing +him to work his way out of each wrong box by raising the entrance door +which had been closed behind him. This he could fairly readily do, and +his stay in a box rarely measured more than ten seconds. + +As a variation in the mode of procedure, confinement for thirty seconds +was tried on June 5, but it worked unsatisfactorily and had to be +abandoned. During this series, the animal was startled by the sound from +one of the sliding bars under the floor, and in the sixth trial he +refused to work. + +As improvement was very slow, varied modes of rewarding and punishing +the animal were tried in the hope of discovering a means of facilitating +the work. Among the former are the use of banana, grapes, peanuts, and +other eagerly sought foods in varying quantities, and in the latter are +included periods of confinement ranging from ten seconds to sixty +seconds. In the end, confinement of about thirty seconds, combined with +a small quantity of food which was much to the monkey's taste, gave most +favorable results. + +All this time Skirrl's attention to the task in hand was seldom good. He +was easily diverted and even when extremely hungry, often stopped work +in the middle of an early trial, yawned repeatedly and finally sat down +to wait for release from the apparatus. + +The results obtained during the long continued trials with this animal +in problem 2 are presented in table 2, which differs from the previously +described table, first, in that several of the trials are followed by an +asterisk to indicate that aid was given by the experimenter, and second, +in that two additional columns, headed, respectively, R and W, are +presented. These give the right and wrong first choices for each day, +whereas the two columns preceding them give the same data for each +series of ten trials. Similarly, the ratio of right to wrong choices is +presented for each day in table 2, instead of for each series of ten +trials as in table 1. + +From the results of table 2, several peculiarly interesting facts +appear. In the first place the influence of the habit of choosing the +first box at the left disappears with surprising suddenness, and in the +second place, there are remarkable contrasts in the results for +different settings as they appear in their respective vertical columns. +Thus, in the case of setting 1, after the first trial mistakes became +relatively infrequent, whereas in setting 6, which involved the same +number of doors, mistakes continued to be the rule until nearly a +thousand trials had been given. The most likely explanation of this +difference is that for some reason the animal avoided box 9. + +The _reactive tendencies_, or better, the _methods of reaction_ which +manifested themselves during this long series of observations may be +described as follows: (a) choice of the first box at the left; (b) +random choice with tendency to choose first, a box near the middle of +the group; (c) choice of first box at the right followed by the one next +to it on the left; (d) direct choice of the right box. + + + +TABLE 2 + +Results for Skirrl, _P. irus_, in Problem 2 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | 1.2.3.4.5 | | | R | W | R | W | of + | trials | 7.8.9 | 1.2.3.4 | 2.3.4.5.6.7 | 1.2.3.4.5.6 | 4.5.6.7.8 | 1.2.3 | 2.3.4.5 | 6.7.8.9 | 1.2.3.4 | 3.4.5.6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + May | | | | | | | | | | | | | | | | + 11&13 | 1- 9 | 7.7.9.7.8 | {1.2.2.1.4.1 | {2.3.2.3.2.5 | {4.6.1.4.1.1 | 4.4.7 | 3.1.2 | 4 | 4.1.8 | 1 | | 1 | 8 | 1 | 8 | 1: 8.00 + | | | {2.1.2.1.3 | {2.3.2.5.6 | {2.6.1.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 24 | 11- 20 | 8*[1] | 2.4.3* | 4.5.6* | 2.2.5* | 5.6.6.7* | 3.1.2 | {5.2.3.5.3.2 | 4.6.8* | 4.4.3* | 5.5.6.7* | 0 |10 | 0 |10 | 0:10.00 + | | | | | | | | {3.5.2.4* | | | | | | | | + | | | | | | | | | | | | | | | | + 25 | 21- 30 | 8* | 4.4.3* | 5.6 | {6.6.2.3.4 | 6.7 | 2 | 4 | 5.6.3.8 | 4.4.3 | 6.4.6.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | {6.6.5* | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 26 | 31- 40 | 8 | 4.3 | 6 | 4.5 | 6.7 | 3.2 | 5.4 | 5.8 | 4.3 | 5.3.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | | | | | | | | + 27 | 41- 50 | 8 | 4.4.3 | 6 | 5 | 6.8.6.8.7 | 3.3.3.2 | 5.4 | {6.5.4.3 | 4.3 | 5.4.8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | {2.1.5.8 | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 51- 60 | 8 | 4.4.3 | 7.6 | 5 | 5.6.7 | 3.3.3.2 | 4 | {5.4.3 | 4.3 | {5.4.3.3.4.5 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | {3.6.8 | | {6.4.3.5.7 | | | | | + | | | | | | | | | | | | | | | | + 29 | 61- 70 | 8 | 4.3 | 6 | 6.6.5 | 7 | 3.3.3.2 | 5.4 | 7.6.4.7.6.8 | 4.3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 31 | 71- 80 | 8 | 4.4.4.3 | 6 | 6.5 | 6.8.7 | 3.2 | 5.4 | {6.7.6.4.3 | 4.3 | 6.7 | 2 | 8 | 2 | 8 | 1: 4.00 + June | | | | | | | | | {2.6.3.7.8 | | | | | | | + | | | | | | {6.8.6.5.4 | | | | | | | | | | + 1 | 81- 90 | 8 | 4.3 | 6 | 5 | {6.5.6.5.8 | 3.1.3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | | | + | | | | | | {5.4.6.4.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 91- 100 | 9.7.8 | 4.2.4.3 | 7.5.6 | 5 | 6.8.7 | 3.3.1.2 | 5.3.4 | 8 | 4.3 | 6.8.7 | 2 | 8 | 7 |13 | 1: 1.86 + 2 | 101- 110 | 8 | 4.3 | 6 | 5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 6.8.6.5.7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + " | 111- 120 | 8 | 4.3 | 7.3.5.7.6 | {6.2.3.6.4 | 7 | 3.2 | {5.2.3.5.3.2 | 9.6.4.7.8 | {4.1.2 | 6.8.7 | 2 | 8 | 6 |14 | 1: 2.33 + | | | | | {3.6.2.5 | | | {3.5.2.3.4 | | {4.2.3 | | | | | | + | | | | | | | | | | | {6.8.6.3 | | | | | + 3 | 121- 130 | 8 | 4.4.3 | 6 | 5 | 6.7 | 3.2 | {5.3.2.3 | 8 | 4.2.3 | {5.4.5.8.8 | 4 | 6 | | | + | | | | | | | | {5.2.5.4 | | | {6.3.8.7 | | | | | + | | | | | | | | | | | | | | | | + " | 131- 140 | 8 | 4.3 | 5.7.3.2.6 | 4.5 | 5.7 | 1.3.2 | 5.3.4 | 6.7.8 | 4.2.1.3 | 7 | 2 | 8 | 6 |14 | 1: 2.33 + | | | | | | | | | | | | | | | | + 4 | 141- 150 | 8 | 4.3 | 7.6 | 6.5 | 7 | 2 | {5.3.2.3 | 6.8 | 4.1.3 | 5.6.7 | 3 | 7 | | | + | | | | | | | | {5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | + " | 151- 160 | 8 | 4.3 | 6 | 5 | 6.7 | 2 | 4 | 5.6.7.8 | 4.3 | 5.6.8.7 | 5 | 5 | 8 |12 | 1: 1.50 + 5 | 161- 170 | 8 | 4.3 | 7.6 | 6.5 | 6.8.7 | 3.2 | 5.3.2.3.5.4 | 8 | 4.3 | 6.7 | 2 | 8 | | | + " | 171- 176 | 8 | 2.4.3 | 7.6 | 6.5* | 8.7 | 3.2* | | | | | 1 | 5 | 3 |13 | 1: 4.33 + 7 | 177- 180 | | | | | | | 5.4 | 8 | 4.4.3 | 8.7 | 1 | 3 | | | + " | 181- 190 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.3.2.5.4 | 8 | 4.3 | 7 | 4 | 6 | 5 | 9 | 1: 1.80 + 8 | 191- 200 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 | | | + " | 201- 210 | 8 | 4.3 | 6 | 6.4.6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 6 |14 | 1: 2.33 + 9 | 211- 220 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.6.7 | 2 | 8 | | | + " | 221- 230 | 9.8 | 4.3 | 7.6 | 6.5 | 6.7 | 3.2 | 5.4 | 7.6.8 | 4.3 | 7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | | | | | | | | | | | + 10 | 231- 240 | 8 | 4.3 | 7.6 | 6.5 | 6.7 | 3.2 | 5.4 | {3.2.3.2.4.3 | 4.3 | 7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | {2.5.4.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + 11 | 241- 250 | 8 | 4.3 | 7.6 | 6.6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | | | | | | | | 12 | 251- 260 | 8 | 4.3 | 6 | 6.5 | 6.7 | 3.3.2 | 5.4 | {7.6.7.7 | 3 | 3.7* | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | {6.9.8* | | | | | | | + | | | | | | | | | | | | | | | | 14 | 261- 270 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | {5.3.4.3 | 3 | {3.3.3.3.4 | 5 | 5 | 5 | 5 | 1: 1.00 + | | | | | | | | | {9.8* | | {4.6.4.7* | | | | | + | | | | | | | | | | | | | | | | 15 | 271- 280 | 7.9.8 | 4.2.3 | 3.4.3.7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 1 | 9 | | | + " | 281- 290 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 3 | 7 | 4 |16 | 1: 4.00 + | | | | | | | | | | | | | | | | | | | | | | | | | {4.3.2.3 | | | | | | | + 16 | 291- 300 | 7.8 | {4.4.4 | 6 | 6.5 | 7 | 3.3.2 | 5.4 | {6.5.4.3 | 4.3 | 6.7 | 2 | 8 | | | + | | | {4.4.3 | | | | | | {5.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | " | 301- 310 | 8 | 4.4.3 | 7.6 | 6.5 | 7 | 3.3.2 | 5.5.4 | {7.6.5.4.6 | 4.3 | 7 | 3 | 7 | 5 |15 | 1: 3.00 + | | | | | | | | | {5.7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | 17 | 311- 320 | 7.8 | 4.3 | 7.6 | 6.6.5 | 7 | 3.2 | 5.4 | 7.6.7.6.7.8 | 4.3 | 7 | 2 | 8 | | | + " | 321- 330 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 6.7 | 2 | 8 | 4 |16 | 1: 4.00 + 18 | 331- 340 | 7.7.8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | | | + " | 341- 350 | 8 | 4.3 | 7.6 | 6.6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | 7 |13 | 1: 1.86 + 19 | 351- 360 | 8 | 4.3 | 7.6 | 6.5 | 6.5.6.5.7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 361- 370 | 8 | 4.3 | 7.6 | 6.4.3.6.5 | 7 | 3.2 | 5.4 | 9.8 | 4.3 | 7 | 3 | 7 | 6 |14 | 1: 2.33 + 21 | 371- 380 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 8.7 | 2 | 8 | | | + " | 381- 390 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 6 |14 | 1: 2.33 + 22 | 391- 400 | 8 | 4.3 | 7.6 | 6.5 | 6.5.4.6.7 | 3.3.3.2 | 5.4 | 6.7.8 | 4.4.3 | 7 | 2 | 8 | | | + " | 401- 410 | 8 | 3 | 7.6 | 6.5 | 8.7 | 2 | 5.4 | 6.7.7.8 | 3 | 7 | 5 | 5 | 7 |13 | 1: 1.86 + | | | | | | | | | | | | | | | | 23 | 411- 420 | 8 | 4.4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | {7.6.7.6 | 4.3 | 7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | {6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | 24 | 421- 430 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 6 | 4 | | | + " | 431- 440 | 8 | 3 | 7.6 | 6.5 | 7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 |11 | 9 | 1: 0.82 + 25 | 441- 450 | 7.8 | 4.4.3 | 7.6 | 6.5 | 6.5.7 | 3.3.2 | 5.5.4 | 7.8 | 4.3 | 7 | 1 | 9 | 1 | 9 | 1: 9.00 + 26 | 451- 460 | 7.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 461- 470 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 6 |14 | 1: 2.33 + 28 | 471- 480 | 8 | 4.4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 9.8 | 3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + 29 | 481- 490 | 8 | 4.3 | 7.7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + 30 | 491- 500 | 7.9.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 501- 510 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.4.3 | 8.7 | 2 | 8 | 5 |15 | 1: 3.00 + July | | | | | | | | | | | | | | | | + 1 | 511- 520 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | 2 | 521- 530 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | {7.6.5.6.5 | 4.4.3 | 7 | 3 | 7 | | | + | | | | | | | | | {6.5.6.8 | | | | | | | + | | | | | | | | | | | | | | | | " | 531- 540 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 4 | 6 | 7 |13 | 1: 1.86 + 3 | 541- 550 | 7.8 | 4.4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 5.5.7 | 3 | 7 | | | + " | 551- 560 | 7.8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 5 | 5 | 8 |12 | 1: 1.50 + 5 | 561- 570 | 7.7.8 | 4.3 | 6 | 6.5 | 6.7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + " | 571- 580 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 4 | 6 | 7 |13 | 1: 1.86 + | | | | | | | | | | | | | | | | | | | | | | {6.5.4.6.5 | | | | | | | | | | + 6 | 581- 590 | 7.8 | 4.3 | 7.6 | 6.6.5 | {5.4.5.4.4 | 2 | 3.4 | 6.5.4.3.7.8 | 3 | 7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | {6.5.6.5.8.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | 7 | 591- 600 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 8.7 | 3 | 7 | | | + " | 601- 610 | 7.8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 1 | 9 | 4 |16 | 1: 4.00 + 8 | 611- 620 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 | | | + " | 621- 630 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 9.8 | 4.3 | 8.7 | 1 | 9 | | | + " | 631- 640 | 8 | 4.4.3 | 7.7.6 | 6.5 | 8.7 | 3.2 | 4 | 8 | 4.3 | 8.7 | 3 | 7 | 6 |24 | 1: 4.00 + | | | | | | | | | | | | | | | | 9 | 641- 650 | 7.8 | 4.3 | 7.6 | 6.5 | 6.7 | 3.2 | {3.2.5.3 | 7.6.5.4.8 | 3 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | {2.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | | | | | | | | | | {6.5.4.3.7 | | | | | | | + 10 | 651- 660 | 7.8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | {6.5.4.7.6 | 4.3 | 7 | 3 | 7 | | | + | | | | | | | | | {5.4.8 | | | | | | | + | | | | | | | | | | | | | | | | 10 | 661- 670 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 6 | 4 | 9 |11 | 1: 1.22 + 12 | 671- 680 | 7.8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 6.5.4.7.8 | 4.3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | | | | | | | | 13 | 681- 690 | 8 | 3 | 7.6 | 6.5 | {6.5.4 | 3.2 | 4 | 6.7.8 | 3 | {6.5.4.5 | 4 | 6 | | | + | | | | | | {6.5.7 | | | | | {6.5.8.7 | | | | | + | | | | | | | | | | | | | | | | " | 691- 700 | 8 | 3 | 6 | 5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 8 | 2 |12 | 8 | 1: 0.67 + | | | | | | | | | | | | | | | | 14 | 701- 710 | 8 | 3 | 7.6 | 6.5 | {6.5.4.5 | 2 | 3.5.4 | 8 | 3 | 7 | 6 | 4 | | | + | | | | | | {4.6.8.7 | | | | | | | | | | + " | 711- 720 | 8 | 3 | 6 | 5 | 7 | 2 | 5.4 | 6.5.4.8 | 3 | 6.5.7 | 7 | 3 |13 | 7 | 1: 0.54 + 15 | 721- 730 | 7.8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | | | + " | 731- 740 | 8 | 3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 6 | 4 |11 | 9 | 1: 0.82 + 16 | 741- 750 | 7.8 | 3 | 6 | 6.5 | 7 | 3.2 | 4 | 8 | 3 | 7 | 7 | 3 | | | + " | 751- 760 | 7.8 | 3 | 7.6 | 6.5 | 7 | 2 | 4 | 7.8 | 4.3 | 7 | 5 | 5 |12 | 8 | 1: 0.67 + 17 | 761- 770 | 8 | 4.3 | 6 | 5 | 8.7 | 3.2 | 5.4 | 8 | 4 | 7 | 6 | 4 | | | + " | 771- 780 | 8 | 2.2.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 3 | 7 | 9 |11 | 1: 1.22 + 19 | 781- 790 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 3.4 | 7.6.5.8 | 3 | 7 | 6 | 4 | | | + " | 791- 800 | 7.8 | 3 | 6 | 5 | 7 | 2 | 5.4 | 8 | 3 | 6.5.6.7 | 7 | 3 | | | + " | 801- 810 | 8 | 2.3 | 6 | 5 | 6.5.7 | 2 | 5.4 | 8 | 3 | 7 | 7 | 3 |20 |10 | 1: 0.50 + 20 | 811- 820 | 7.8 | 3 | 7.6 | 5 | 7 | 3.3.2 | 5.4 | 8 | 2.2.3 | 7 | 5 | 5 | | | + " | 821- 830 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 4 | 8 | 2.3 | 8.7 | 6 | 4 |11 | 9 | 1: 0.82 + 21 | 831- 840 | 8 | 3 | 5.4.5.6 | 5 | 7 | 2 | 4 | 6.7.8 | 3 | 8.7 | 7 | 3 | | | + " | 841- 850 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 3.2.4 | 8 | 3 | 7 | 7 | 3 |14 | 6 | 1: 0.43 + 22 | 851- 860 | 8 | 4.3 | 6 | 5 | 7 | 3.2 | 3.5.4 | 8 | 3 | 8.7 | 6 | 4 | | | + " | 861- 870 | 7.8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 4 | 8 | 3 | 8.7 | 3 | 7 | | | + " | 871- 880 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 2 | 8 |11 |19 | 1: 1.73 + 23 | 881- 890 | 8 | 3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | | | + " | 891- 900 | 8 | 3 | 7.6 | 6.5 | 7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | 9 |11 | 1: 1.22 + 24 | 901- 910 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | | | + " | 911- 920 | 8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 7 | 3 |11 | 9 | 1: 0.82 + 26 | 921- 930 | 7.8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 8 | 2.2.3 | 8.7 | 4 | 6 | | | + " | 931- 940 | 8 | 3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 7 |13 | 1: 1.86 + 27 | 941- 950 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + 28 | 951- 960 | 8 | 3 | 7.6 | 6.5 | 5.4.7 | 2 | 5.5.4 | 8 | 3 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 29 | 961- 970 | 8 | 3 | 7.6 | 5 | 8.7 | 2 | 4 | 8 | 3 | 7 | 8 | 2 | 8 | 2 | 1: 0.25 + | | | | | | | | | | | | | | | | 30 | 971- 980 | 8 | 3 | 4.3.2.6 | 5 | {6.5.4.6 | 2 | 5.5.4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | {6.5.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | 31 | 981- 990 | 8 | 3 | 6 | 6.5 | 8.7 | 2 | 4 | 8 | 3 | 7 | 8 | 2 | 8 | 2 | 1: 0.25 + August | | | | | | | | | | | | | | | | + 2 | 991-1000 | 8 | 3 | 7.6 | 5 | 7 | 2 | {2.3.5.3 | 7.6.8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | | | {2.3.3.4 | | | | | | | | + | | | | | | | | | | | | | | | | 3 | 1001-1010 | 8 | 3 | 7.6 | 5 | 7 | 2 | 4 | 7.6.5.6.7.8 | 3 | 5.4.3.4.3.7 | 7 | 3 | | | + " | 1011-1020 | 8 | 2.3 | 5.6 | 3.2.3.6.5 | 7 | 2 | 5.4 | 9.8 | 2.1.3 | 7 | 4 | 6 |11 | 9 | 1: 0.82 + | | | | | | | | | | | | | | | | 4 | 1021-1030 | 7.8 | 3 | 5.4.3.7.6 | 6.5 | {6.5.6 | 3.2 | 5.4 | 8 | {2.2.4.2 | 8.7 | 2 | 8 | | | + | | | | | | {5.6.7 | | | | {4.2.3 | | | | | | + | | | | | | | | | | | | | | | | " | 1031-1040 | 7.8 | 3 | 6 | 6.4.3.6.5 | 7 | 2 | 3.5.4 | 8 | 2.3 | 8.7 | 5 | 5 | 7 |13 | 1: 1.86 + | | | | | | | | | | | | | | | | 5 | 1041-1050 | 8 | 3 | 6 | 2.3.2.6.5 | 8.7 | 2 | 4 | 8 | 2.2.4.3 | {8.8.6.8.4 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | {6.5.8.7 | | | | | + | | | | | | | | | | | | | | | | 6 | 1051-1060 | 8 | 3 | 6 | 4.2.6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | | | | | | 7 | 1061-1070 | 8 | 3 | 5.4.3.6 | 4.5 | {6.5.6.5 | 2 | 4 | 8 | 3 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | {4.8.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | 9 | 1071-1080 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 7 |10 | 0 |10 | 0 | 1: 0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 1.2.3.4.5 | | | | | | 1.2.3.4 | 2.3.4.5 | | | | | + | | 5.6.7.8 | 2.3.4.5.6 | 6.7.8.9 | 5.6.7 | 1.2.3.4 | 4.5.6 | 2.3.4.5 | 1.2.3 | 5.6.7 | 6.7.8.9 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 10 | 1- 10 | 6.5.7 | 3.2.6.5 | 8 | 6 | 2.4.3 | 5 | 5.4 | 2 | 7.5.2.7.6 | 8 | 5 | 5 | 5 | 5 | 1: 1.00 + 11 | 11- 20 | 7 | 3.6.5 | 8 | 6 | 3 | 6.5 | 4 | 3.2 | 7.6 | 8 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | | | | | | | | | | | | | | {3.2.3.5.3 | | | | | | | | + 12 | 21- 30 | 7 | 2.2.6.5 | 7.8 | 6 | 3 | 5 | {2.5.3.2 | 2 | 6 | 8 | 7 | 3 | 7 | 3 | 1: 0.43 + | | | | | | | | {5.3.2.5 | | | | | | | | + | | | | | | | | {2.5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote 1: First choices correct by reason of aid from the experimenter +are not counted as correct (R) in the summary.] + +[Footnote *: Aided by experimenter.] + + +The method of choosing the first box at the right end and then the one +next to it developed in the case of all except two of the ten settings. +The time of appearance is worth noting. In setting 1, it failed to +appear; in setting 2, it developed early,--after about one hundred +trials; in setting 3, after about one hundred and fifty trials; in +setting 4, after about one hundred and fifty trials; in setting 5, after +about one hundred and seventy trials; in setting 6, after about one +hundred trials; in setting 7, after about fifty trials; in setting 8, it +never developed; in setting 9, after about fifty trials; and in setting +10, it developed very late,--after about four hundred and seventy +trials. + +This method of reaction, although inadequate, proved remarkably +persistent, and it is doubtful whether it had been wholly overcome at +the conclusion of the experiment. In the case of the series of trials +given on June 8, numbered 191 to 200, the method used was either that of +the first at the right and then the next, or direct choice of the right +box. + +Throughout the trials with this problem, the end boxes, numbers 1 and 9, +were avoided. This is at least partially explained by the fact that they +never existed, and obviously never could appear, in problem 2, as right +boxes. In trials 601 to 610, given on July 7, there occurred partial +return to the formerly established method of choosing the first door at +the right. This relapse was characteristic of what happened during the +many days which intervened between the definite appearance of this habit +and the final solution of the problem. + +Especially in connection with such relapses, Skirrl showed extreme +fatigue or ennui and often would refuse to work and simply sit before +the open doors yawning. This happened even when he was extremely hungry +and evidently eager enough for food. + +From July 12 on the hunger motive was increased by feeding the monkey +only in the apparatus and by so regulating the amount of food given in +each trial that he should obtain barely enough to keep him in good +physical condition. An increase in the number of correct choices +promptly resulted, and continued until on July 14 the ratio of choices +was 1 to .54. It appeared from these data that a relatively small number +of choices, say not more than ten a day, the rewards in connection with +which supplied the only food received by the animal, yielded most +favorable results. + +On July 16, the period of confinement in wrong boxes was increased to +sixty seconds, and it was so continued for a number of days. But in the +end, it became clear that the period of thirty seconds, combined with a +liberal reward in the shape of desired food and a single series of ten +trials per day, was most satisfactory. The detailed data of table 2 +indicate that at this time Skirrl was making his choices by memory of +the particular setting. + +Skirrl, on July 17 was evidently hungry and eager to locate food, but +seemingly unable to select the right box. In trial 5 (765th) of the +series, he was punished by confinement in box 8. When the doors were +unlocked in order that the entrance door might be raised to release him, +the lock-bar, sliding under the floor, made a slight grating noise, and +the instant the entrance door was opened, he jumped out excitedly. _He +made no outcry, but as soon as he was out of the box, sat down, and +taking up his right hind foot, examined it for a few seconds._ Having +apparently assured himself that nothing serious had happened, he went on +unconcernedly about his task. The presumption is that the sound of the +lock-bar, associated as it was with his painful experience in box 1, +revived the strongly affective experience of stepping on the nail. +Psychologically described, the sound induced an imaginal complex +equivalent to the earlier painful experience. The behavior seems to the +writer a most important bit of evidence of imagery in the monkey. +Finally, on August 9, after ten hundred and seventy trials, Skirrl +succeeded in choosing correctly in the ten trials of a series, and he +was therefore considered to have solved the problem of the second door +from the right end of the group. + +On the following day, he was given a control series with the settings +which are presented on page 19 and also at the bottom of table 2. In +this series he chose correctly five times,--in other words, as often +correctly as incorrectly. An analysis of the choices indicates, however, +that two of the five correct choices were made in box 8, which, as it +happened, had proved a peculiarly easy one for him throughout the +training, since from the first he tended to avoid door 9. Consequently, +it is only fair to conclude, from the results for this control series +and for those given on August 11 and 12, that the animal chose not on +the basis of anything remotely resembling a general idea of secondness +from the right end, but instead on the basis of gradually acquired modes +of reaction to the particular settings. This conclusion is strengthened +by the fact that he had failed to learn to react appropriately and +readily to most of the settings of the regular series. + +The curve which represents the course of the learning process in this +problem is presented in figure 19. For this and all other curves which +involve more than a single series of observations a day, the method of +construction was as follows: The first series for each day of training +is indicated on the curve by a dot, while the second or third series on +a given day, although space is allowed for them, are not so indicated. +Consequently, the form of the curve is determined chiefly by the first +series per day. The extreme irregularities of this curve are most +interesting and puzzling, as are also the variations in the daily ratios +of right to wrong first choices. Three times in the course of the +training, this ratio rose to 1 to 9, or higher. The causes for such +extreme variations are not easily enumerated, but a few of the most +obvious contributory causes are variations in the weather, especially +cloudiness or fogginess, which rendered the apparatus dark; variations +in the degree of hunger or eagerness for food; differences in the +activities of the animals in the cages outside of the laboratory +(sometimes they were noisy and distracted the subject), and finally, +differences in the physical fitness and attitude of the animal from day +to day. + +The more or less incidental behavior in connection with this experiment +more strongly than the statistical results of the work on problem 2 +indicate the existence of imagery. That ideas played a part in the +solution of the problem is probable, but at best they functioned very +ineffectively. The small number of methods used in the selection of the +right box, and the slight variations from the chief method, that of +choosing the first box at the right end and then the one next to it, +apparently justify Doctor Hamilton's characterization of this monkey as +defective. + + +[Illustration: FIGURE 19.--Error curves of learning for the solution of +problem 2 (second box from right end).] + + +_Problem 3. Alternately First at Left and First at Right_ + +Following the control series given in connection with problem 1, an +interval of rest lasting from August 12 to August 19 was allowed in +order that Skirrl might in part at least lose the effects of his +training and regain his customary interest in the apparatus by being +allowed to obtain food easily instead of by dint of hard labor,--labor +which was harder by far, apparently, than physical activity because it +demanded of the animal certain mental processes which were either +lacking or but imperfectly functional. The difficultness of the daily +tasks appears to be reliably indicated by the tendency to yawn. + +Systematic work on problem 3, which has been defined as alternately the +first door at the left and the first door at the right of the group, was +begun August 19, and for nine days a single series of ten trials per day +was given. Work then had to cease because of the experimenter's return +to Cambridge. + +The results of the work on this problem demand but brief analysis and +comment. The expected ratio of one right to four wrong choices per +series appears (see table 3) for the first series of trials, and _this +in spite of the fact that Skirrl had been trained for several weeks to +choose the second door from the right end_. One would ordinarily have +predicted a much larger number of incorrect choices. The right choices +were due to the monkey's strong tendency to go first to the first door +at the right and thence to the one next to it. Indeed in the series +given on August 24; this method was followed without variation. In other +words, in every one of the ten trials Skirrl entered first the box at +the extreme right end of the group. This necessarily resulted in as many +right as wrong first choices. Consequently, the ratio reads 1 to 1. But +the method was not adhered to, and at no time either before or after +that date did he succeed in equalling this achievement. There was, as a +matter of fact, no steady improvement, and so far as one may judge from +the records which were obtained, the course of events in the solution of +this problem would have been similar to those in problem 2. + + + +TABLE 3 + +Results for Skirrl, _P. irus_, in Problem 3 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + Date | No. of | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | R | W | R | W |Ratio of + | trials | 5.6.7 | 5.6.7 | 1.2.3.4.5.6 | 1.2.3.4.5.6 | 4.5.6.7.8 | 4.5.6.7.8 | 2.3.4.5 | 2.3.4.5 | 3.4.5.6.7.8.9| 3.4.5.6.7.8.9| | | | |R to W +________|___________|______________|______________|______________|______________|______________|______________|______________|______________|______________|______________|___|___|___|___|________ +August | | | | | | | | | | | | | | | | + | | | | {6.5.4.6 | | | | | | | {8.7.6.5 | | | | | + 19 | 1- 10 | 7.5 | 6.7 | {3.2.6.4 | 5.3.6 | {7.8.7.6 | 8 | 4.3.5.4.5.2 | 5 | 9.8.7.6.4.3 | {4.5.8.7 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | {3.6.1* | | {8.6.4 | | | | | {6.5.9* | | | | | + | | | | | | | | | | | | | | | | + | | | | {5.4.6.5 | | {8.7.6.7 | | | | | | | | | | + 20 | 11- 20 | 7.6.5 | {6.5.6.5 | {4.6.5.3 | 5.3.2.4.6 | {7.5.8.8 | 8 | 5.4.3.2 | 4.5 | 8.7.6.5.4.3 | {8.7.6.8.3 | 1 | 9 | 1 | 9 | 1:9.00 + | | | {7 | {2.5.1* | | {7.6.4* | | | | | {7.6.4.3.9 | | | | | + | | | | | | | | | | | | | | | | + | | | | {6.2.5.6 | | | | {5.3.5.4 | | | | | | | | + 21 | 21- 30 | 7.6.7.6.5 | 7 | {5.3.6.5 | 2.5.5.6 | 8.6.5.4 | 8 | {3.5.3.5 | 5 | {9.8.7.6 | 8.9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | {4.3.1* | | | | {4.3.2* | | {5.4.3 | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 23 | 31- 40 | 7.6.5 | 6.5.7 | {6.4.3.2 | 3.2.6 | 8.7.6.4 | 8 | 5.4.5.3.2 | 5.2 | 8.7.3 | 9 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | {5.6.2.1 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 24 | 41- 50 | 7.6.5 | 7 | {6.2.5 | 6 | {8.7.8.7 | 8 | 5.3.2 | 5 | {9.8.7.6 | 9 | 5 | 5 | 5 | 5 | 1:1.00 + | | | | {4.3.1 | | {5.7.5.4 | | | | {5.4.3 | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | {8.7.3.6 | | | | | + 25 | 51- 60 | 7.6.5 | 6.5.7 | 5.2.1 | 6 | 8.5.4 | 8 | 2 | 2.5 | 9.8.7.4.3 | {8.7.5.3 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | {8.7.9* | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 26 | 61- 70 | 7.6.5 | 6.5.7 | 1 | 2.1.6 | 8.7.6.4 | 8 | 2 | 3.2.5 | 9.8.7.5.3 | {3.6.8.3 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | {4.7.9 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | {8.6.3.3 | | | | | + 27 | 71- 80 | 7.6.5 | 7 | 2.1 | 1.5.6 | 8.7.6.4 | 8 | 2 | 5 | 9.8.7.6.3 | {7.5.3.8 | 4 | 6 | 4 | 6 | 1:1.50 + | | | | | | | | | | | {3.6.9* | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 81- 90 | 7.6.7.5 | 7 | 3.1 | 6 | 8.6.4 | 4.8 | 2 | 2.4.5 | 8.7.4.3 | 3.8.9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + + + + +2. Sobke, _Pithecus rhesus_ + + +_Problem 1. First at the Left End_ + +Sobke was somewhat afraid of the experimenter when the investigation was +undertaken, and instead of willingly coming out of his cage when the +door was raised, he often had to be coaxed out and lured into the +apparatus with food. Whereas Skirrl was frank and rather aggressive, +Sobke was stealthy in his movements, furtive, and evidently suspicious +of the experimenter as well as of the apparatus. He was perfectly safe +to approach, but would not permit anyone to touch him. After a few days, +he began to take food from the hands of the experimenter. + +Preliminary work to acquaint this monkey with the routine of the +experiment was begun on April 13. As in the case of Skirrl, he was lured +into the apparatus and was taught the route through the boxes to the +starting point by being allowed to obtain food once each day in each of +the nine boxes. The procedure was simple. The entrance door and the exit +door of a particular box were raised and the animal admitted to the +reaction-compartment and permitted to pass through the box whose doors +stood open, take its food, and return to the starting point. Sobke very +quickly learned the route perfectly and came to work steadily and +rapidly. After five days of preliminary work of this sort, he was so +thoroughly accustomed to the apparatus that it was evidently desirable +to begin with regular training experiments. + +The first series of trials was given on April 19. Both punishment and +reward were employed from the first. The punishment consisted of +confinement for thirty seconds in each wrong box, and the reward of a +small piece of banana, usually not more than a tenth of a medium sized +banana for each correct choice. The total time for the first series of +trials was fourteen minutes. This indicates that Sobke worked rapidly. +My notes record that he worked quickly though shyly, wasted almost no +time, made few errors of choice, and waited quietly during confinement +in the boxes. In this, also, he differed radically from Skirrl who was +restless and always tried to escape from confinement. + +Throughout the work on problem 1, punishment and reward were kept +constant. Everything progressed smoothly; there were no such +irregularities of behavior as appeared in the case of Skirrl, and +consequently the description of results is a relatively simple matter. +Sobke invariably chose the end boxes. His performance was in every way +superior to that of Skirrl. + +As previously, the detailed results are presented in tabular form (table +4). From this table it appears that, whereas the expected ratio of right +to wrong first choices for this problem is 1 to 2.5, the actual ratio +for Sobke's first series was 1 to .67. This surprisingly good showing is +unquestionably due to his marked tendency to choose the end box of a +group; and this tendency, in turn, may in part be the result of the +preliminary training, for during that only one box was open each time. +But, if the preliminary training were responsible for Sobke's tendency, +it should be noted that it had very different effect upon Skirrl, and, +as will be seen later, upon Julius. + +The results for the ten different settings of the doors for problem 1 as +they appear in table 4 are of interest for a number of reasons. In the +first place, the setting 1. 2. 3 appearing twice,--at the beginning of +the series and again at the end--yielded markedly different results in +the two positions. For whereas no mistakes were made in the case of +setting 1, there were fifty per cent of incorrect first choices for +setting 10. Again, satisfactory explanation is impossible. It is +conceivable that fatigue or approaching satiety may have had something +to do with the failures at the end of the series, but as a rule, as is +indicated by settings 1, 2, and 6, if correct choices were made at the +beginning, they continued throughout the day's work. + +In this problem, Sobke's improvement was steady and fairly rapid, and in +the eighth series, trials 71 to 80, only correct first choices appear. +Consequently, seventy trials were required for the solution of the +problem. This number is in marked contrast with Skirrl's one hundred and +thirty-two trials. + +Immediately following the first perfect series, Sobke was given two +series of control tests on April 28. Conditions were unfavorable, since +the day was stormy and the rain pattering on the sheet-iron roof made a +great din. Nevertheless, he worked steadily and well up to the sixth +trial, which was preceded by a slight delay because of the necessity of +refilling some of the food boxes. After this interruption, wrong choices +occurred in trial 6. And again after trial 9, there was brief +interruption, followed by wrong choices in trial 10. The ratio of right +to wrong choices for this first control series was therefore 1 to .25. + + + +TABLE 4 + +Results for Sobke, _P. rhesus_, in Problem 1 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | | | R | W | R | W | of + | trials | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + April | | | | | | | | | | | | | | | | + 19 | 1-10 | 1 | 8 | 3 | 9.7 | 6.2 | 6 | 7.5 | 4 | 9.7 | 1 | 6 | 4 | 6 | 4 | 1:0.67 + 20 | 11-20 | 1 | 8 | 3 | 7 | 2 | 6 | 7.5 | 8.4 | 9.9.7 | 1 | 7 | 3 | 7 | 3 | 1:0.43 + 21 | 21-30 | 1 | 8 | 4.3 | 9.7 | 2 | 6 | 5 | 8.4 | 7 | 1 | 7 | 3 | 7 | 3 | 1:0.43 + 22 | 31-40 | 1 | 8 | 3 | 7 | 6.2 | 6 | 6.5 | 4 | 7 | 3.1 | 7 | 3 | 7 | 3 | 1:0.43 + 23 | 41-50 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 9.7 | 3.1 | 8 | 2 | 8 | 2 | 1:0.25 + 24 | 51-60 | 1 | 8 | 3 | 9.7 | 2 | 6 | 5 | 4 | 7 | 2.1 | 8 | 2 | 8 | 2 | 1:0.25 + 26 | 61-70 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 3.1 | 9 | 1 | 9 | 1 | 1:0.11 + 27 | 71-80 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 |10 | 0 |10 | 0 | 1:0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | 2.3.4 | | | 1.2.3.4.5 | | | | | + | | 2.3.4 | 6.7.8.9 | 3.4.5 | 4.5.6.7.8.9 | 6.7.8.9 | 1.2.3.4.5 | 5.6.7.8 | 3.4.5.6.7.8 | 5.6.7 | 6.7.8.9 | | | | | + | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ | | | | + 28 | 1-10 | 2 | 6 | 3 | 4 | 6 | 5.4.1 | 2 | 3 | 5 | 5.4.2.1 | 8 | 2 | | | + " | 11-20 | 2 | 6 | 3 | 4 | 6 | 2.1 | 2 | 3 | 5 | 1 | 9 | 1 |17 | 3 | 1:0.18 + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + + + +Six minutes after completion of the first control series, a second was +given under slightly more favorable conditions, and in this only a +single wrong choice occurred, in that box 2 was first chosen in trial 6 +instead of box 1. From the results of these two control series, it is +evident that Sobke's solution of problem 1 is reasonably adequate. He is +easily diverted or disturbed in his work by any unusual circumstances, +but so long as everything goes smoothly, he chooses with ease and +certainty. Whether it is fair to describe the behavior as involving an +idea of the relation of the right box to the other members of the group +would be difficult to decide. I hesitate to infer definite ideation from +the available evidence, but I strongly suspect the presence of images +and relatively ineffective or inadequate ideation. + +It is perfectly evident that Sobke is much more intelligent than Skirrl. +In practically every respect, he adapted himself more quickly to the +experimental procedure and progressed more steadily toward the solution +of the problem than did Skirrl. The contrast in the learning processes +of the two monkeys could scarcely be better exhibited than by the curves +of learning which are presented in figure 18. The first, that for Sobke, +is surprisingly regular; the second, that for Skirrl, is quite as +surprisingly irregular. These results correlate perfectly with the +steadiness and predictability of the former's responses and the +irregularity and erraticness of the latter's. + + +_Problem 2. Second from the Right End_ + +On the completion of problem 1 Sobke was in perfect condition, as to +health and training, for experimental work. He had come to work quietly, +fairly deliberately, and very steadily. His timidity had diminished and +he would readily come to the experimenter for food, although still he +was somewhat distrustful at times and became timid when anything unusual +occurred in the apparatus. + +As preparation for problem 2, a break in regular experimentation +covering four days followed the control series of problem 1. On each of +these four days the monkey was allowed to get food once from each of the +nine boxes, both doors of a given box being open for the trial and all +other doors closed. For this feeding experiment, the doors were opened +in irregular order, and this order was changed from day to day. + +Systematic work with problem 2 began on May 3, with punishment of thirty +seconds for mistakes and a liberal reward of food for each success. +Early in the series of trials it was discovered that Sobke was likely to +become discouraged and waste a great deal of time unless certain aid +were given by the experimenter. On this account, after the first two +trials, the method was adopted of punishing the animal by confinement +for the first ten mistakes in a trial, and of then, if need be, +indicating the right box by slightly and momentarily raising the exit +door. Every trial in which aid was thus given by the experimenter is +indicated in table 5 by an asterisk following the last choice. In the +first series of trials for this problem, aid had to be given in seven of +the ten trials, and even so the series occupied seventy-one minutes. It +is possible that had no aid been given, the work might have been +continued successfully with a smaller number of trials than ten per day. +But under the circumstances it seemed wiser to avoid the risk of +discouraging and thus spoiling the animal for use in the experiment. It +should be stated, also, that it proved impossible to adhere to the +period of thirty seconds as punishment in this series. For the majority +of the wrong choices confinement of not more than ten seconds was used. + +For the second series, given on May 4, the conditions were unfavorable +in that it was dark and rainy, and the noise of the rain on the roof +frightened Sobke. He refused to work after the fourth trial, and the +series had to be completed on the following day. The total time required +for this series was seventy-eight minutes. + +The work on May 6 was distinctly better, and the animal's behavior +indicated, in a number of trials, definite recognition of the right +door. He might, for example, make a number of incorrect choices, then +pause for a few seconds to look steadily at the doors, and having +apparently found some cue, run directly to the right box. No aid from +the experimenter was needed in this series. + +On the following day improvement continued and the animal's method of +choosing became definite and fairly precise. He was deliberate, quiet, +and extremely business-like. The time for the series was thirty-one +minutes. + +The period of punishment was increased on May 12 to thirty seconds. +Previously, for the greater number of the trials, it had been ten to +fifteen seconds. This increase apparently did not disturb the monkey, +for he continued to work perfectly throughout the series, although +making many mistakes in spite of deliberate choices and the refusal of +certain boxes in each trial. + +An interesting and significant incident occurred on May 13 when at the +conclusion of trial 5, Doctor Hamilton came into the experiment room for +a few minutes. Sobke immediately stopped working, and he could not be +induced to make any choices until Doctor Hamilton had left the room. +This well indicates his sensitiveness to his surroundings, and his +inclination to timidity or nervousness even in the presence of +conditions not in themselves startling. + +Work was continued thus steadily until May 28 when, because of the +failure of the animal to improve, it seemed wise to increase the period +of confinement as punishment to sixty seconds. In the meantime, it had +sometimes been evident that Sobke was near to the solution of his +problem. He would often make correct choices in three or four trials in +succession and then apparently lose his cue and fail utterly for a +number of trials. + +After June 1, in order to hasten the solution of the problem, two series +per day were given. In some instances the second series was given almost +immediately after the first, while in others an interval of an hour or +more intervened. It was further found desirable to give Sobke all of his +food in the apparatus. When the rewards obtained in the several trials +did not satisfy his hunger, additional food was presented, on the +completion of the series of experiments, in one or more of the food +cups. On days marked by unwillingness or refusal to work, very little +food was given. Thus, the eagerness of the monkey to locate the right +box was increased and, as a matter of observation, his deliberateness +and care in choice increased correspondingly. Sixty seconds punishment +was found satisfactory, and it was therefore continued throughout the +work on this problem. + +It was evident, on June 9, from the behavior of the monkey as well as +from the score, that the perfect solution of the problem was near at +hand. This fact the experimenter recorded in his daily notes, and sure +enough, on the following day Sobke chose correctly throughout the series +of ten trials. The time for this series was only ten minutes. The +choices were made deliberately and readily. + +An analysis of the data of table 5 reveals five methods or reactive +tendencies which appeared more or less definitely in the following +order: (a) Choice of first box at the left, because of experience in +problem 1. This tendency was very quickly suppressed by the requirements +in connection with problem 2. Indeed one of the most significant +differences which I have discovered between the behavior of the primates +and that of other mammals is the time required for the suppression of +such an acquired tendency. The monkey seems to learn almost immediately +that it is not worth while to persist in a tendency which although +previously profitable no longer yields satisfaction, whereas in the +crow, pig, rat, and ring dove, the unprofitable mode of response tends +to persist during a relatively large number of trials. (b) The tendency +to choose, first, a box near the left end of the group, to go from that +to the box at the extreme right end of the group, thence to the one next +in order, which was, of course, the right box. This tendency appears +fairly clearly from May 7th on. (c) The box at the extreme right was +first chosen and then the one next to it. For example, in setting 2, box +4 would be chosen first, then box 3. Or, if this did not occur, the +method previously described under (b) was likely to be employed, as for +example, in setting 8, where such choices as 7.6.5.1.8 appear. (d) In +certain series there appeared a marked preference for a particular box, +usually box 3 (see results for May 24). This was doubtless due in a +measure, if not wholly, to the fact that box 3 was the right box twice +in each series of ten settings. But it should be added that the same is +true of box 7, for which no preference was manifested at any time. (e) +Direct choice of the right box. + +The five reactive methods or tendencies enumerated above roughly +appeared in the order named, but there were certain irregularities and +the order as well as the time of appearance varied somewhat from setting +to setting. In general, method c was the most frequently used prior to +the development of method e, the direct choice of the right box. + + + +TABLE 5 + +Results for Sobke, _P. rhesus_, in Problem 2 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | 1.2.3.4.5 | | | R | W | R | W | of + | trials | 7.8.9 | 1.2.3.4 | 2.3.4.5.6.7 | 1.2.3.4.5.6 | 4.5.6.7.8 | 1.2.3 | 2.3.4.5 | 6.7.8.9 | 1.2.3.4 | 3.4.5.6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + May | | {7.7.9.7.7 | {1.2.4.1 | {3.2.7.2 | {4.6.1.6 | | {3.1.3.3 | | | {4.1.4.1 | {3.8.3.3 | | | | | + 3 | 1-10 | {9.7.9.7.9 | {1.4.1.1 | {7.7.7.5 | {1.6.1.1 | 5.8.6.7 | {3.3.1.1 | 3.5.4 | 9.1.8 | {4.1.4.2 | {3.8.6.3 | 0 |10 | 0 |10 | 0:10.00 + | | {7.9.9.7.8* | {4.3* | {2.7.6* | {1.3.5* | | {1.1.2* | | | {1.4.3* | {8.3.7* | | | | | + | | | | | | | | | | | | | | | | + | | | | {4.7.2.7 | | (8.8.4.8 | | {5.5.5.5 | {9.5.5.9 | | | | | | | +4 and 5 | 11-20 | (7.9.7.9.9 | 1.4.1.3 | {2.7.3.2 | 1.6.5 | {8.8.4.8 | {3.3.1.1.3 | {5.5.5.3 | {7.1.6.6 | {4.4.4.4 | {8.8.6.8 | 0 |10 | 0 |10 | 0:10.00 + | | {9.7.7.9.8 | | {7.2.6* | | {4.8.7* | {3.3.1.2 | {5.5.4* | {6.5.8* | {4.4.4.3 | {8.7 | | | | | + | | | | | | | | | | | | | | | | + 6 | 21-30 | 9.7.9.7.8 | 4.3 | 7.2.3.7.6 | {6.3.1.6 | 6.8.7 | 3.1.2 | {5.3.5.3 | {6.9.4.6.1 | {4.1.2.4 | {3.4.5.3 | 0 |10 | 0 |10 | 0:10.00 + | | | | | {6.2.6.5 | | | {2.4 | {7.9.7.8 | {4.2.3 | {8.6.7 | | | | | + | | | | | | | | | | | | | | | | + 7 | 31-40 | 7.9.7.8 | 1.4.3 | 2.7.6 | 3.5 | 4.8.7 | 3.1.2 | 3.2.3.5.4 | 8 | 4.3 | 5.8.3.4.8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + 8 | 41-50 | 7.9.7.8 | (4.2.4.1.4 | 6 | 5 | 6.5.4.8.7 | {3.1.3.1 | 5.3.5.4 | {7.4.2.1 | {4.2.4.1 | 5.3.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | {4.2.2.4.3 | | | | {3.1.3.2 | | {9.8 | {4.3 | | | | | | + | | | | | | | | {5.3.5.3 | | | | | | | | + 10 | 51-60 | 7.7.8 | 3 | 7.3.2.7.6 | 6.4.6.5 | (6.4.8.5 | 3.1.3.2 | {2.5.3.5 | 5.9.8 | 4.2.4.3 | {6.5.4 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | {4.8.7 | | {2.5.4 | | | {3.8.7 | | | | | + | | | | | | | | | | | | | | | | + 11 | 61-70 | 7.9.7.8 | 1.4.3 | 4.3.2.7.6 | 6.5 | {5.4.8.6 | 3.2 | 5.4 | 6.5.2.3.1.8 | 3 | 6.5.3.8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | {5.4.8.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + 12 | 71-80 | 7.9.8 | 3 | 7.3.2.7.6 | 6.5 | 5.4.8.7 | 1.2 | 5.4 | 8 | 4.3 | 5.4.3.8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + 13 | 81-90 | 7.8 | 4.3 | 3.7.6 | 6.5 | 8.7 | 1.3.2 | 2.5.2.5.4 | 7.6.5.9.8 | 3 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | | | | | | | | | + | | | | | | | | | | {1.2.1.2.2 | | | | | | + 14 | 91-100 | 7.8 | 3 | 6 | 5 | 6.5.4.7 | 1.3.2 | 5.4 | 9.8 | {1.4.2.2.1 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | {4.1.4.3 | | | | | | + | | | | | | | | | | | | | | | | + 15 | 101-110 | 7.8 | 3 | 7.6 | 5 | 5.4.5.7 | 3.2 | 5.4 | 8 | 2.1.3 | 8.8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | | | | | | | | + 17 | 111-120 | 7.8 | 4.3 | 7.6 | {2.1.2.1.2 | 8.7 | 3.2 | 5.4 | 7.6.5.1.8 | 3 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | {1.3.2.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 18 | 121-130 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 7.6.5.2.8 | 3 | 8.7 | 3 | 7 | 3 | 7 | 1: 2.33 + | | | | | | | | | | | | | | | | + | | | | | | | | {5.3.2.5.3 | | | | | | | | + | | | | | | | | {2.5.2.5.3 | | | | | | | | + 19 | 131-140 | 8 | 3 | 3.2.6 | 5 | 7 | 3.2 | {5.5.2.5.5 | 7.6.9.8 | 3 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | {3.2.5.5.3 | | | | | | | | + | | | | | | | | {2.5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | + 20 | 141-150 | 7.8 | 3 | 3.2.7.6 | 6.5 | 5.4.7 | 3.2 | 3.2.5.4 | 6.5.4.3.8 | 3 | 7 | 3 | 7 | 3 | 7 | 1: 2.33 + 21 | 151-160 | 7.8 | 3 | 5.7.5.3.7.6 | 5 | 7 | 3.2 | 5.3.5.2.5.4 | 7.6.5.9.8 | 3 | 6.4.3.8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 22 | 161-170 | 7.8 | 3 | 7.6 | 3.2.6.5 | 7 | 3.2 | {5.2.5.3 | 7.6.5.8 | 3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | {2.5.4 | | | | | | | | + | | | | | | | {3.1.3 | | | | | | | | | + 24 | 171-180 | 8 | 3 | {3.2.7.5 | {3.6.4 | 8.7 | {1.3.3 | {3.5.4 | 8 | {4.4.2.1 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | {7.3.6 | {3.6.5 | | {3.2 | | | {4.3 | | | | | | + | | | | | | | | | | | | | | | | + 25 | 181-190 | 7.9.7.9.8 | 3 | 3.7.6 | 5 | 8.7 | 3.2 | 5.4 | 4.3.8 | 4.3 | 8.7 | 2 | 8 | 2 | 8 | 1: 4.00 + 26 | 191-200 | 8 | 3 | 6 | 5 | 8.7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 5 | 5 | 5 | 5 | 1: 1.00 + 27 | 201-210 | 7.9.8 | 3 | 3.2.7.6 | 5 | 8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + 28 | 211-220 | 8 | 3 | 3.7.6 | 4.3.2.6.5 | 8.7 | 3.2 | 5.4 | 7.6.5.9.8 | 3 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + 29 | 221-230 | 7.8 | 3 | 5.4.3.7.6 | 6.5 | 7 | 2 | 3.2.5.4 | 7.6.5.8 | 3 | 3.8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + 31 | 231-240 | 7.7.8 | 3 | 3.7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 9.8 | 3 | 3.7 | 2 | 8 | 2 | 8 | 1: 4.00 + June | | | | | | | | | | | | | | | | + 1 | 241-250 | 8 | 3 | 5.4.7.6 | 3.2.6.5 | 8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + " | 251-260 | 7.9.8 | 3 | 3.7.6 | 5 | 6.5.4.8.7 | 3.2 | 4 | 5.4.3.8 | {4.2.1.4 | 7 | 4 | 6 | 8 |12 | 1: 1.50 + | | | | | | | | | | {2.4.4.3 | | | | | | + | | | | | | | | | | | | | | | | + 2 | 261-270 | 7.8 | 3 | 6 | 3.2.6.5 | 7 | 3.2 | 3.4 | 8 | 3 | 6.5.3.8.7 | 5 | 5 | | | + " | 271-280 | 7.8 | 3 | 3.7.6 | 3.6.5 | 7 | 3.2 | 5.4 | 7.6.5.4.3.8 | 3 | 7 | 4 | 6 | 9 |11 | 1: 1.22 + 3 | 281-290 | 7.8 | 3 | 7.6 | 3.6.5 | 8.7 | 3.2 | 4 | 7.8 | 3 | 7 | 4 | 6 | | | + " | 291-300 | 9.8 | 3 | 3.6 | 4.3.6.5 | 8.7 | 2 | 3.5.4 | 7.6.5.9.8 | 3 | 8.7 | 3 | 7 | 7 |13 | 1: 1.86 + 4 | 301-310 | 8 | 3 | 7.6 | 3.4.3.6.5 | 8.7 | 2 | 3.2.5.4 | 7.6.5.8 | 3 | 3.8.7 | 4 | 6 | | | + " | 311-320 | 8 | 3 | 5.4.7.6 | 3.2.6.5 | 7 | 2 | 3.2.5.4 | 8 | 3 | 7 | 7 | 3 |11 | 9 | 1: 0.82 + 5 | 321-330 | 8 | 3 | 6 | 4.6.5 | 7 | 2 | 3.5.4 | 8 | 4.3 | 7 | 7 | 3 | | | + " | 331-340 | 8 | 3 | 7.4.7.6 | 3.2.4.6.5 | 7 | 3.2 | 3.5.4 | 8 | 3 | 7 | 6 | 4 |13 | 7 | 1: 0.54 + 7 | 341-350 | 8 | 3 | 7.6 | 5 | 8.7 | 1.3.1.2 | 3.5.4 | 8 | 3 | 7 | 6 | 4 | | | + " | 351-360 | 8 | 3 | 7.6 | 5 | 8.7 | 2 | 3.5.4 | 8 | 3 | 7 | 7 | 3 |13 | 7 | 1: 0.54 + 8 | 361-370 | 7.8 | 3 | 4.7.6 | 3.5 | 8.7 | 2 | 3.4 | 9.8 | 3 | 7 | 4 | 6 | | | + | 371-380 | 8 | 3 | 7.6 | 3.4.4.3.5 | 8.7 | 3.2 | 3.4 | 8 | 3 | 7 | 5 | 5 | 9 |11 | 1: 1.22 + 9 | 381-390 | 8 | 3 | 6 | 4.2.1.5 | 7 | 2 | 3.4 | 8 | 3 | 8.7 | 7 | 3 | | | + " | 391-400 | 8 | 3 | 6 | 5 | 7 | 2 | 3.4 | 8 | 3 | 7 | 9 | 1 |16 | 4 | 1: 0.25 + 10 | 401-410 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 7 |10 | 0 |10 | 0 | 1: 0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 1.2.3.4.5 | | | | | | 1.2.3.4 | 2.3.4.5 | | | | | + | | 5.6.7.8 | 2.3.4.5.6 | 6.7.8.9 | 5.6.7 | 1.2.3.4 | 4.5.6 | 2.3.4.5 | 1.2.3 | 5.6.7 | 6.7.8.9 | | | | | + | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 11 | 1-10 | 6.7 | 3.5 | 8 | 6 | 3 | 5 | 3.4 | 3.2 | 7.7.2.6 | 8 | 5 | 5 | 5 | 5 | 1: 1.00 + 12 | 11-20 | 7 | 3.6.6.2.5 | 8 | 6 | 3 | 4.5 | 4 | 2 | 7.6 | 8 | 7 | 3 | 7 | 3 | 1: 0.43 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +Examination of table 5 indicates that some of the settings proved very +easy for Sobke; others, extremely difficult. Consequently, the number of +methods which were tried and rejected for a given setting varies from +two to five. Setting 2 proved a fairly simple one, and after the +inhibition of the tendency to choose the first box at the left, the only +definite tendency to appear was that of choosing the first box at the +right, and then the one next to it. After one hundred and thirty trials, +this method suddenly gave place to direct choice of the right box, and +during the following twenty-eight series, no error occurred for this +setting. Setting 4, on the contrary, proved extremely difficult, and a +variety of methods is more or less definitely indicated by the records. + +It is needless to lengthen the description by analyzing the data for +each setting, since the reader by carefully scanning the columns of data +in table 5 may observe for himself the various tendencies and their +mutual relations. + +Sobke's curve of learning (figure 19) in problem 2, is extremely +irregular, as was that of Skirrl. Similar irregularities appear in the +daily ratios of right to wrong first choices presented in the last +column of table 5. Most of these irregularities were due, I have +discovered, to unfavorable external conditions. Thus, dark rainy days +and disturbing noises outside the laboratory were obviously conditions +of poor work. + +On the day following the final and correct series for problem 2, a +control series was given. In this Sobke seemed greatly surprised by the +new situations which presented themselves. Repeatedly he exhibited +impulses to enter the box which would have been the correct one in the +regular series of settings. He frequently inhibited such impulses and +chose correctly, but at other times he reacted quickly and made +mistakes. It was evident from his behavior that he was not guided by +anything like a definite idea of the relation of the right box to the +other members of the group. + +In a second control series given on the following day, June 12, +confusion appeared, but less markedly. For the first setting, a correct +choice was made with deliberation. For the second setting, box 3 was +immediately chosen, as should have been the case in the regular series +of settings. Sobke seemed confused when he emerged from this box and had +difficulty in locating the right one. Then followed direct correct +choices for settings 3, 4, and 5. For setting 6, there is recorded a +deliberately made wrong choice, and so on throughout the series, the +choices being characterized by deliberateness and definite search for +the right box. Uncertainty was plainly indicated, and in this the +behavior of the animal differed markedly from that in the concluding +series of the regular experiment. + +It seems safe to conclude from the results of these control series that +Sobke has no free idea of the relation of secondness from the right and +is chiefly dependent upon memory of the particular settings for cues +which lead to correct choice. + + +_Problem 3. Alternately First at Left and First at Right_ + +For four successive days after the last control series in connection +with problem 2, Sobke was merely fed in the apparatus according to +previous description (p. 43). He exhibited a wonderfully keen appetite +and was well fed during this interval between problems. + +The method of experimentation chosen for problem 3 in the light of +previous experience was that of confining the monkey for a short time, +ten to fifteen seconds, in the wrong box, in each of the first ten +mistakes for a given trial, and of then aiding him to find the right box +by the slight and momentary raising of the exit door. Aid proved +necessary in a few of the trials during the first four days. Then he +worked independently. As work progressed it was found possible and also +desirable to increase the period of confinement, and in the end, sixty +seconds proved satisfactory. It was also thought desirable to increase +the number of trials per day from a single series during the early days +to two or even three series from June 29 on. Often three series could be +given in succession without difficulty. During the early trials on this +problem Sobke worked remarkably well, but later his willingness +diminished, evidently because of his failure readily to solve the +problem, and it became extremely difficult to coax him into the +apparatus. On days when he entered only reluctantly and as it seemed +against his will, he was likely to be nervous, erratic, and often slow +in making his choices, but above all he tended to waste time by not +returning to the starting point, preferring rather to loiter in the +alleyways or run back and forth. + + + +TABLE 6 + +Results for Sobke, _P. rhesus_, in Problem 3 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | 3.4.5.6 | 3.4.5.6 | R | W | R | W | of + | trials | 5.6.7 | 5.6.7 | 1.2.3.4.5.6 | 1.2.3.4.5.6 | 4.5.6.7.8 | 4.5.6.7.8 | 2.3.4.5 | 2.3.4.5 | 7.8.9 | 7.8.9 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + June | | | | | {3.1.2.1 | {7.8.7.8 | | | | {9.8.7.9 | | | | | | + 17 | 1--10 | {6.6.7.6 | 5.7 | {4.4.3.5.4 | {4.4.2.1 | {8.8.7.8 | 8 | 2 | 3.2.5 | {8.7.6.9 | 3.8.9 | 2 | 8 | 2 | 8 | 1:4.00 + | | {6.5 | | {5.4.2.1 | {5.4.6* | {7.7.4* | | | | {8.7.3* | | | | | | + | | | | | | | | | | | | | | | | + | | | | {3.4.2.5 | | {8.7.7.5 | | | | | | | | | | + 18 | 11--20 | 6.6.6.5 | 5.7 | {4.5.6.4 | 3.1.4.3.6 | {8.8.7.8 | 8 | 3.2 | (3.4.2.4 | 9.8.8.7.3 | 8.6.9 | 1 | 9 | 1 | 9 | 1:9.00 + | | | | {2.3.1* | | {7.8.4* | | | {4.5 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | {3.6.5.4 | | {8.8.7.7 | | | | | | | | | | + 19 | 21--30 | 6.5 | 7 | {2.5.2.6 | 3.6 | {7.8.8.8 | 8 | 4.3.2 | {3.2.4.2 | {9.8.7.9.7 | 9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | {3.5.1* | | {8.4 | | | {2.5 | {6.5.4.3 | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | (8.8.8.8 | | | | {9.9.8.9 | | | | | | + 21 | 31--40 | 6.5 | 5.6.5.7 | {3.5.4.6 | 2.5.3.6 | {7.8.3.8 | 8 | 4.2 | 2.5 | {9.5.9.9 | 9 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | {4.3.5.1 | | {8.7.4* | | | | {9.9.3* | | | | | | + | | | | | | | | | | | | | | | | + 22 | 41--50 | 7.6.5 | 6.5.5.7 | 1 | 2.1.3.6 | {8.8.8.8 | 8 | 2 | 2.3.2.2.5 | {9.8.9.8.7 | 9 | 4 | 6 | 4 | 6 | 1:1.50 + | | | | | | {7.8.4 | | | | {6.5.9.3 | | | | | | + | | | | | | | | | | | | | | | | + 23 | 51--60 | 5 | 6.5.7 | 1 | {1.2.1.1 | 8.5.4 | 8 | 5.4.2 | 2.4.2.5 | {9.8.4.9 | 9 | 4 | 6 | 4 | 6 | 1:1.50 + | | | | | {3.2.6 | | | | | {7.3 | | | | | | + | | | | | | | | | | | | | | | | + 24 | 61--70 | 7.6.5 | 7 | 2.3.1 | 2.1.5.4.2.6 | 8.7.8.4 | 8 | 4.5.4.3.2 | 2.2.4.5 | 9.7.6.8.3 | 9 | 3 | 7 | 3 | 7 | 1:2.33 + 25 | 71--80 | 6.5 | 5.7 | 3.1 | 6 | 8.5.4 | 8 | 2 | 3.2.5 | 9.8.7.3 | 3.9 | 3 | 7 | 3 | 7 | 1:2.33 + | | | | | | | | | | | | | | | | + 26 | 81--90 | 7.7.6.5 | 6.5.7 | 3.1 | {1.4.1.1 | 8.4 | 8 | 5.4.2 | 2.5 | 9.8.9.6.3 | 9 | 2 | 8 | 2 | 8 | 1:4.00 + | | | | | {5.1.6 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 91--100 | 7.6.5 | 7 | 1 | 1.2.4.6 | 8.4 | 8 | 2 | 3.2.2.2.5 | 9.8.8.7.9.3 | 9 | 5 | 5 | 5 | 5 | 1:1.00 + | | | | | | | | | | | | | | | | + 29 | 101--110 | 7.6.5 | 5.7 | 1 | {1.1.5.3 | 8.4 | 8 | 2 | 4.2.5 | {9.9.8.9.4 | 9 | 4 | 6 | | | + | | | | | {2.1.6 | | | | | {9.7.6.3 | | | | | | + | | | | | | | | | | | | | | | | + " | 111--120 | 6.5 | 6.5.7 | 1 | 2.1.1.3.6 | 8.5.4 | 8 | 2 | 3.2.5 | 9.8.7.6.4.3 | 9 | 4 | 6 | 8 |12 | 1:1.50 + 30 | 121--130 | 5 | 6.5.6.5.5.7 | 1 | 3.1.6 | 8.7.6.8.5.4 | 8 | 2 | 4.2.4.2.5 | 9.3 | 9 | 5 | 5 | | | + " | 131--140 | 5 | 7 | 1 | 2.3.6 | 8.5.6.4 | 8 | 2 | 5 | 9.8.3 | 3.9 | 6 | 4 |11 | 9 | 1:0.82 + July | | | | | | | | | | | | | | | | + 1 | 141--150 | 5 | 7 | 1 | 1.6 | 8.7.4 | 8 | 2 | 3.2.5 | 9.8.6.9.3 | 9 | 6 | 4 | | | + " | 151--160 | 5 | 7 | 1 | 2.5.3.6 | 8.4 | 8 | 2 | 2.5 | 9.3 | 8.8.7.5.4.9 | 5 | 5 |11 | 9 | 1:0.82 + 2 | 161--170 | 6.5 | 7 | 1 | 2.6 | 8.4 | 8 | 2 | 3.5 | 9.3 | 9 | 5 | 5 | 5 | 5 | 1:1.00 + 3 | 171--180 | 6.5 | 7 | 1 | 1.5.6 | 8.4 | 8 | 2 | 3.5 | 9.3 | 9 | 5 | 5 | | | + " | 181--190 | 5 | 7 | 1 | 4.6 | 8.6.4 | 8 | 2 | 5 | 9.8.4.8.5.3 | 9 | 7 | 3 |12 | 8 | 1:0.67 + 5 | 191--200 | 6.5 | 5.7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 9.5.3 | 9 | 6 | 4 | | | + " | 201--210 | 5 | 7 | 6.1 | 2.6 | 8.6.4 | 8 | 5.3.5.4.3.2 | 4.3.5 | 9.7.3 | 9 | 4 | 6 |10 |10 | 1:1.00 + | | | | | | | | | | | | | | | | + 6 | 211--220 | 5 | 5.7 | 1 | 2.6 | 8.6.4 | 8 | 2 | 4.3.5 | 9.3 | {5.4.8.3 | 4 | 6 | | | + | | | | | | | | | | | {8.5.4.9 | | | | | + | | | | | | | | | | | | | | | | + " | 221--230 | 5 | 7 | 1 | 5.3.6 | 8.6.8.4 | 8 | 4.2 | 3.2.5 | 9.3 | 9 | 5 | 5 | 9 |11 | 1:1.22 + 7 | 231--240 | 5 | 7 | 1 | 2.6 | 8.4 | 7.4.8 | 2 | 4.3.5 | 8.3 | 9 | 5 | 5 | | | + " | 241--250 | 5 | 7 | 2.6.3.5.1 | 6 | 8.4 | 8 | 2 | 5 | 9.3 | 9 | 7 | 3 | | | + | | | | | | | | | | | | | | | | + | | | | {2.6.2.6.4 | | | | | | | | | | | | + " | 251--260 | 5 | 7 | {6.3.2.6 | 6 | 8.4 | 8 | 2 | 5 | 9.5.3 | 9 | 7 | 3 |19 |11 | 1:0.58 + | | | | {5.4.3.1 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 8 | 261--270 | 7.5 | 7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 8.3 | 8.5.4.9 | 5 | 5 | | | + " | 271--280 | 5 | 7 | 2.6.4.6.1 | 6 | 8.5.8.4 | 7.4.8 | 5.5.3.5.2 | 5 | 9.3 | 9 | 5 | 5 |10 |10 | 1:1.00 + | | | | | | | | | | | | | | | | + 9 | 281--290 | 5 | 5.7 | 1 | 6 | 8.4 | 8 | 2 | 2.5 | 8.3 | {7.3.8.6.8 | 5 | 5 | | | + | | | | | | | | | | | {4.7.3.9 | | | | | + | | | | | | | | | | | | | | | | + " | 291--300 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 9.3 | 9 | 8 | 2 | | | + " | 301--310 | 5 | 7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 9.5.3 | 9 | 7 | 3 |20 |10 | 1:0.50 + 10 | 311--320 | 5 | 7 | 1 | 6 | 8.4 | 7.4.8 | 2 | 5 | 9.3 | 9 | 7 | 3 | | | + " | 321--330 | 5 | 7 | 1 | 5.2.6 | 8.7.4 | 8 | 2 | 5 | 9.3 | 9 | 7 | 3 |14 | 6 | 1:0.43 + 12 | 331--340 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 8.3 | 9 | 8 | 2 | | | + " | 341--350 | 5 | 7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 9.3 | 9 | 7 | 3 |15 | 5 | 1:0.33 + 13 | 351--360 | 5 | 5.7 | 1 | 6 | 8.4 | 8 | 5.2 | 5 | 3 | 9 | 7 | 3 | | | + " | 361--370 | 5 | 7 | 6.1 | 6 | 4 | 8 | 5.2 | 3.2.5 | 9.3 | 9 | 6 | 4 |13 | 7 | 1:0.54 + 14 | 371--380 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 7.4.3.9 | 8 | 2 | | | + " | 381--390 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 9.3 | 4.7.3.9 | 7 | 3 |15 | 5 | 1:0.33 + 15 | 391--400 | 5 | 5.5.7 | 1 | 3.6 | 8.4 | 8 | 3.2 | 5 | 8.3 | 9 | 5 | 5 | | | + " | 401--410 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 7.3 | 6.5.3.9 | 7 | 3 |12 | 8 | 1:0.67 + 16 | 411--420 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 9 | 9 | 1 | | | + " | 421--430 | 5 | 7 | 1 | 6 | 4 | 8 | 2 | 5 | 3 | 4.7.4.9 | 9 | 1 | | | + " | 431--440 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 5.7.3.9 | 8 | 2 |26 | 4 | 1:0.15 + 17 | 441--450 | 5 | 7 | 1 | 6 | 4 | 4.8 | 2 | 5 | 4.3 | 3.5.9 | 7 | 3 | | | + " | 451--460 | 5 | 7 | 1 | 3.6 | 4 | 5.4.8 | 2 | 5 | 9.3 | 9 | 7 | 3 | | | + " | 461--470 | 5 | 7 | 1 | 6 | 4 | 8 | 2 | 5 | 3 | 9 |10 | 0 |24 | 6 | 1:0.25 + 19 | 471--480 | 5 | 7 | 1 | 6 | 8.4 | 8 | 2 | 5 | 3 | 9 | 9 | 1 | 9 | 1 | 1:0.11 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + | | 5.6 | 5.6 | 4.5.6.7.8.9 | 4.5.6.7.8.9 | 1.2.3.4.5 | 1.2.3.4.5 | 2.3.4.5.6.7 | 2.3.4.5.6.7 | 3.4.5.6.7.8 | 3.4.5.6.7.8 | | | | | + | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 19 | 1--10 | 5 | 6 | 4 | 9 | 1 | 5 | 3.7.2 | 7 | 3 | 8 | 9 | 1 | 9 | 1 | 1:0.11 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +The data of table 6 indicate for this problem only three pronounced +reactive tendencies: (a) As the initial tendency, the choice of the +second box from the right end. This proved surprisingly weak, in view of +the animal's long training on problem 2, and it disappeared quickly. (b) +Choice of the end boxes, and (c) direct choice of the right box. + +For this, as for the other problems, extreme differences in method and +in time and degree of success appear for the different settings. Thus, +while settings 1, 2, 3, 6, 7, and 10 proved to be easy, settings 4, 5, +8, and 9 were evidently more difficult. + +[Illustration: FIGURE 20.--Error curve of learning for the solution of +problem 3 (alternately the first box at the left end and the first at +the right end) by Sobke.] + +From the first this problem promised to be much easier for Sobke than +problem 2, and although the actual number of trials necessary for the +solution is greater by sixty for problem 3 than for problem 2, +comparison of the data of the tables justifies the statement that the +third problem was both easier and more nearly adequately solved than the +second. This is not surprising when the nature of the two problems is +considered, for whereas problem 2 requires choice by perception of the +relationship of secondness from the right end of the group, problem 3 +requires, instead, the choice of the end member of the group each time, +with the additional variation of alternation of ends. Now as it happens, +the end member is easily selected by the monkey, and it appears further +that alternation was relatively easy for Sobke to acquire. Consequently, +the combination of end and alternation proved easier than the choice of +the second from the right end of the group. + +The above statements are supported by comparison of the curves of +learning. The curve for problem 2, figure 19, is extremely irregular; +that for problem 3, figure 20, much more regular. Similarly, the daily +ratios of right to wrong choices as exhibited in tables 5 and 6 indicate +smaller variations for the third problem than for the second. + +Sobke made ten correct first choices in the third series for July 17, +but he was working very uncertainly and it seemed rather a matter of +good luck than good management that he succeeded in presenting this +perfect series: For this reason and also because it did not seem +feasible to have Sunday intervene between the final and perfect regular +series and the control series, an additional regular series was given on +July 19, in which, as the table indicates, a single mistake occurred, in +trial 5. The monkey was working perfectly. The series of trials required +only ten minutes, and it was evident that carelessness and eagerness to +obtain food were chiefly responsible for the mistake. + +The control series given on July 19 immediately after the series just +described resulted similarly in one failure and nine successes. The +choices were made easily and with certainty, and the only mistake, that +of setting 7, was apparently due to carelessness. + +This excellent showing for the control series wholly justifies the +comparison of problems 2 and 3 as to difficultness, made above. Whereas +in both problems 1 and 2 the control trials caused confusion, in the +case of problem 3, they did not essentially alter the behavior of the +animal. The fact seems to be that for this problem the particular +setting is of relatively little importance; while turning alternately to +the extreme left and the extreme right is of prime importance. That +Sobke had the idea of alternation or of the end box, there seems no more +reason for insisting than that he had the idea of secondness from the +right end in problem 2. It is possible, even probable, that these ideas +existed rather vaguely in his consciousness, but there is obviously no +necessity for insisting that the solution of the problems depended upon +them. + + +_Problem 4. Middle_ + +As the available time for the continuation of the experiment was +limited, it was decided to proceed with work on problem 4 immediately +upon the completion of problem 3, and on July 20, the problem of the +middle door was presented to Sobke. Since it was anticipated that this +sudden change would confuse and discourage him greatly, the only form of +punishment administered was the momentary lowering of the entrance door +of the wrong box. As in the previous problem, he was aided after ten +successive wrong choices. As might have been anticipated, he +persistently entered the end boxes of the groups, and this in some +instances probably would have been kept up for many minutes had not the +experimenter lured him into the right box by slightly raising the exit +door. In the first series, he had to be aided in five of the ten trials. +The total time for the series was forty-five minutes, the total number +of choices, eighty-eight. In the second series, he was aided in four of +the trials. The total time required was seventy-two minutes, and the +total number of choices was seventy-six. + +Throughout the first series, Sobke worked hard, but with evidently +increasing dissatisfaction. He clung persistently to his acquired +tendency to choose the end boxes, and after each trial he returned less +willingly to the starting point. Up to this time his attitude toward the +experimenter had been perfectly friendly, if not wholly trustful. But +when on July 21 he was brought into the apparatus for the second series, +he exhibited a wholly new form of behavior, for instead of attending +diligently to the open doors and devoting his energies to trying to find +the right box, he instead, after gazing at them for a few seconds, +turned toward the experimenter and jumped for him savagely, throwing +himself against the wire netting with great force. This was repeated a +number of times during the first two or three trials, and it occurred +less frequently later in the series. Since nothing unusual had happened +outside of the experiment room, the suggested explanation of this sudden +change in attitude and behavior is that the monkey resented and blamed +on the experimenter the difficulty which he was having in obtaining +food. + +From this time on until the end of my work, Sobke was always savage and +both in and out of the apparatus he was constantly on the watch for an +opportunity to spring upon me. Previously, it had been possible for me +to coax him into the apparatus by offering him food and to return him to +his cage by walking after him. But on and after the twenty-first of +July, it was impossible for me to approach him without extreme risk of +being bitten. + +Doctor Hamilton when told of this behavior, reported that several times +monkeys have shown resentment toward him when they were having trouble +in the experiment. I therefore feel fairly confident that I have not +misinterpreted Sobke's behavior. When on July 22 I gave Sobke an +opportunity to enter the apparatus, he refused, and it was impossible to +lure him in with food. Two hours later, having waited meantime for his +breakfast, he entered readily and worked steadily and persistently +through his third series of trials, but in no one of these trials did he +choose correctly. Neither on this day nor the following did he exhibit +resentment while at work. He apparently had regained his affective poise +and was able to attend as formerly to the task of locating his rewards. + +During these first three series, although the ratio of right to wrong +choices stood 0 to 10, there occurred a marked reduction in the number +of trials in which aid was necessary as well as in the total number of +choices, and on July 23 correct reactions began to appear. Improvement +during the next hundred trials was steady and fairly rapid, and on July +31, a record of seven right to three wrong trials was obtained. This was +surprising to the experimenter, as well as gratifying, since he was +eager to have the animal complete this problem before work should have +to be discontinued. + +Everything went smoothly until August 2, when my assistant, who had been +left in charge of the experimental work for a week, attempted to +increase the number of trials per day to two series. Sobke apparently +was not quite ready for this increase in the amount of his day's labor +and refused to work at the end of the first series. In this series he +did less well than on the previous day. The following day, August 3, +unfortunately and contrary to the wishes of the experimenter, the +laboratory was painted and there was necessarily considerable +disturbance because of the presence of the workmen, and in addition, the +pervasive odor of fresh paint. Sobke chose still less successfully on +this date, and on August 4, he refused to work after the eighth trial. +It is true that during these bad days the total number of choices +steadily diminished while the successes, also, diminished, or at best, +failed to increase. When on August 9, I returned to the laboratory to +take charge, I found that Sobke was no longer trying to solve the +problem as when I had gone away. His attitude had changed in that he had +become indifferent, careless, and obviously discouraged with his task. + + + +TABLE 7 + +Results for Sobke, _P. rhesus_, in Problem 4 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | 1.2.3.4 | | | 1.2.3.4.5 | | | 3.4.5.6 | | R | W | R | W | of + | trials | 2.3.4 | 5.6.7.8.9 | 5.6.7 | 7.8.9 | 4.5.6.7.8 | 6.7.8.9 | 1.2.3 | 2.3.4.5.6 | 7.8.9 | 6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + July | | | {5.9.5.5 | {1.7.1.3 | {9.7.9.7 | | {1.9.3.1 | | {6.3.2.6 | | | | | | | + 20 | 1- 10 | 2.4.2.4.3 | {5.9.5.6 | {1.7.1.7 | {7.9.7.9 | {8.4.8.4 | {9.2.9.3 | 3.1.3.2 | {3.6.3.2 | {9.3.4.3 | {8.6.6.8.6 | 0 |10 | 0 |10 | 0:10.00 + | | | {5.8.7* | {1.7.4* | {7.7.8 | {4.6 | {9.1.5* | | {6.3.4* | {3.9.3.6 | {8.6.8.6.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | {7.9.7.7 | {4.8.5.5 | {1.4.3.2 | | | {3.9.3.8 | | | | | | + 21 | 11- 20 | 2.3 | {5.6.5.5 | {1.2.7.1 | {7.9.7.7 | {8.4.8.4 | {8.9.1.9 | 3.1.2 | {6.2.3.2.6 | {4.3.3.5 | 6.7 | 0 |10 | 0 |10 | 0:10.00 + | | | {9.5.5.7 | {7.3.7.4 | {9.7.8* | {5.4.6* | {1.9.5* | | {3.5.2.4 | {3.4.6* | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | {3.7.4.8 | | | | | | + 22 | 21- 30 | 2.3 | 5.6.5.6.7 | 1.7.4 | {7.9.7 | 4.7.4.6 | {1.4.6.3 | 3.1.2 | 5.2.6.4 | {4.3.5.8 | 6.6.7 | 0 |10 | 0 |10 | 0:10.00 + | | | | | {7.7.8 | | {2.7.5 | | | {3.7.6* | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | {5.4.7.4 | | | | | | + 23 | 31- 40 | 2.4.3 | 5.6.8.7 | 1.7.4 | {7.7.7.7 | 4.7.6 | 2.7.5 | 3.1.2 | 6.4 | {7.5.4.3 | 7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | {7.7.8 | | | | | {7.3.6 | | | | | | + | | | | | | | | | | | | | | | | + 24 | 41- 50 | 3 | 5.6.7 | 1.6.4 | 7.7.7.8 | 4.7.6 | {2.7.6.4 | 3.2 | 6.5.4 | 5.3.8.6.6 | 7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | {2.7.3.8 | | | | | | | | | + | | | | | | | {9.6.5* | | | | | | | | | + | | | | | | | | | | | | | | | | + 26 | 51- 60 | 4.3 | 6.5.7 | 2.7.4 | 7.8 | 6 | {6.4.2.7 | 3.2 | {6.5.3.5.2 | 7.6 | 7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | {4.8.6.5 | | {6.5.6.4 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | {4.7.3.7 | | | | | | | | | + 27 | 61- 70 | 3 | 6.5.7 | 2.5.4 | 7.7.8 | 5.7.6 | {4.6.1.4 | 2 | 6.5.4 | 5.7.6 | 6.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | {7.3.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 28 | 71- 80 | 3 | 7 | 6.5.4 | 7.8 | 5.4.7.6 | 2.7.6.5 | 2 | 5.5.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 29 | 81- 90 | 3 | 6.5.7 | 2.4 | 7.7.8 | 5.4.6 | {2.7.7.6 | 2 | 4 | 5.4.7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | {2.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 30 | 91-100 | 3 | 7 | 2.6.5.4 | 7.8 | 6 | 5 | 2 | 5.4 | 5.4.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 31 | 101-110 | 3 | 7 | 2.4 | 7.8 | 6 | 5 | 2 | 4 | 7.6 | 7 | 7 | 3 | 7 | 3 | 1: 0.43 + August | | | | | | | | | | | | | | | | + 2 | 111-120 | 3 | 7 | 6.5.7.6.4 | 7.8 | 6 | 4.2.7.6.5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 3 | 121-130 | 3 | 6.5.7 | 7.6.5.4 | 7.8 | 7.6 | 5 | 2 | 6.5.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 4 | 131-140 | 3 | 7 | 6.5.7.6.4 | 7.8 | 6 | {2.7.6.4 | 2 | 6.4 | 3.5.4.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + | | | | | | | {8.7.6.5 | | | | | | | | | + | | {2.4.4.4 | | | | | | | | | | | | | | + 5 | 141-150 | {2.4.4.2 | 6.5.7 | {2.7.6.7 | 8 | 7.6 | {2.8.7.6 | 3.2 | 6.4 | 7.6 | 8.7 | 1 | 9 | 1 | 9 | 1: 9.00 + | | {4.3* | | {5.4 | | | {8.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 6 | 151-160 | 2.4.4.3 | 7 | 2.6.5.4 | 7.8 | 7.6 | 7.6.5 | 2 | 6.4 | 6 | 7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + | | {4.4.2.4 | | | | | | | | | | | | | | + " | 161-170 | {4.2.4.2 | 7 | 6.5.4 | 7.8 | 7.6 | 7.6.5 | 3.2 | 5.4 | 7.6 | 7 | 2 | 8 | 6 |14 | 1: 2.33 + | | {4.4.3 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 7 | 171-180 | 4.3 | 7 | 6.5.4 | 8 | 7.6 | 5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | | | + | | | | | | | | | | | | | | | | + " | 181-190 | {4.2.4.4 | 7 | 7.6.5.4 | 7.8 | 6 | 6.5 | 2 | 6.5.4 | 7.6 | 7 | 4 | 6 | 9 |11 | 1: 1.22 + | | {2.4.3 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 9 | 191-200 | 3 | 7 | 5.4 | 8 | 8.7.6 | 6.5 | 2 | 6.5.4 | 7.6 | 8.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | | | | | | | | + 10 | 201-210 | 3 | 7 | 2.5.4 | 7.8 | 7.6 | {2.8.7.6 | 2 | 6.5.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | {8.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 11 | 211-220 | 3 | 7 | 6.5.4 | 7.8 | 6 | {7.6.4.3 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + | | | | | | | {2.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 12 | 221-230 | 3 | 7 | 2.4 | 7.8 | 6 | 7.6.5 | 2 | 6.5.4 | 8.7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 19 | 231-240 | 3 | 7 | 2.4 | 7.8 | 6 | 5 | 2 | 6.4 | 8.7.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + | | | | | | | | | | | | | | | | + 20 | 241-250 | 3 | 7 | 5.4 | 8 | 7.6 | {2.4.1.2.7 | 3.2 | 6.4 | 7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | {8.7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 21 | 251-260 | 3 | 7 | 6.5.4 | 7.8 | {7.4.5.4 | {6.4.3.2 | 2 | 6.5.4 | 8.7.6 | 7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | {8.7.6 | {7.6.5 | | | | | | | | | + | | | | | | | | | | | | | | | | + 23 | 261-270 | 3 | 7 | 6.5.4 | 7.8 | 6 | 6.5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 24 | 271-280 | 3 | 7 | 6.4 | 7.8 | 7.6 | 2.5 | 2 | 4 | 7.4.3.8.7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 25 | 281-290 | 3 | 7 | 2.5.4 | 8 | 7.6 | 5 | 2 | 6.4 | 7.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 26 | 291-300 | 3 | 7 | 6.5.4 | 8 | 7.6 | 7.6.5 | 2 | 6.5.4 | 7.6 | 7 | 5 | 5 | 5 | 5 | 1: 1.00 + 27 | 301-310 | 3 | 7 | 2.6.5.4 | 8 | 7.6 | 5 | 2 | 6.5.4 | 7.5.4.9.8.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 + 28 | 311-320 | 3 | 7 | 2.5.4 | 8 | 6 | 9.8.7.5 | 2 | 3.4 | 8.6 | 7 | 6 | 4 | 6 | 4 | 1: 0.67 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +I immediately set about reinstating the former attitude by lessening the +number of trials and the punishment, and by increasing the value of the +reward, but my best efforts, continuing up to August 28, failed markedly +to improve the condition. The number of correct choices did somewhat +increase, but at no time did the animal attain the degree of success +which he had achieved as early as July 31 in the eleventh series of +trials. + +During the last two weeks of experimentation, all possible efforts were +put forth to discover the best combination of rewards and punishments. +Punishment was varied from 0 to confinement of sixty seconds, and many +kinds of food in different amounts were tried as rewards, but in spite +of everything Sobke failed to improve markedly. From time to time, +notably on August 12 and 21, he exhibited peculiarly strong resentment +toward me and repeatedly attempted to attack me. + +The outcome of my experiments with problem 4 is peculiarly interesting +in that it indicates the importance of a favorable attitude toward the +work and the extreme risk from disturbing or discouraging conditions. It +seems not improbable that had the work progressed without change in +experimenter, or method of procedure, and above all without the +disturbance of the painting, Sobke might have solved problem 4 within a +few days. This is by no means certain, however, for in problems 2 and 3 +the ratio of right to wrong choices instead of increasing steadily +increased very irregularly. + +The detailed results for this problem are given in table 7. Reactive +tendencies which appear are: (a) persistent choice of the end boxes +followed, subsequently, by (b) the tendency to locate the middle box +directly. This proved fairly easy when the number of boxes involved was +only three as in settings 1, 4, 7, and 10. Setting 4 was most difficult +of all, because box 9 was avoided or ignored. When the number of open +boxes was as great as five, as in settings 2 and 8, the task was +obviously more difficult, but whereas success in setting 2 appeared +early, in setting 8 it failed to appear during the course of +experimentation. For the settings 3, 6, and 9, involving either seven or +nine open boxes, the direct choice of the middle box was next to +impossible, and Sobke tended to choose, first of all, a particular box +toward one end of the series, for example, box 2, in setting 3, and box +7 in setting 9. To the experimenter, as he watched the animal's +behavior, it looked as though effort each time were being made to locate +the middle member of the group. This appeared relatively easy for groups +of three boxes, extremely difficult for as many as five boxes, and +almost impossible for seven or nine. + + +3. Julius, _Pongo pygmaeus_ + +_Problem 1. First at the Left End_ + +The orang utan, Julius, was gentle, docile, and friendly with the +experimenter throughout the period of investigation. He at no time +showed inclination to bite and could be handled safely. As contrasted +with Skirrl and even with Sobke, he adapted himself to the +multiple-choice apparatus very promptly, and only slight effort on the +part of the observer was necessary to prepare him, by preliminary +trials, for the regular experiments. But in order to facilitate work, he +was familiarized with the apparatus by means of regular route training +and feeding in the several boxes from April 5 to April 9. + +On April 10 the apparatus was painted white as has been stated +previously, and on the following Monday, April 12, Julius when again +introduced to it gave no indications of fear, uneasiness, or dislike, +but worked as formerly, making his round trips quickly and eagerly +entering any box which happened to be open, in order to obtain the +reward of food. + +The regular experimentation was undertaken on April 13, and the results +of the first series of trials with Julius are sharply contrasted with +those obtained with the monkeys in that fewer choices were necessary. +Instead of the expected ratio of right to wrong first choices, 1 to 2.5, +the orang utan gave a ratio of 1 to 1. An additional markedly different +result from that obtained with the monkeys is indicated below in the +total time required for a series of trials. As examples, the data for +the first, second, fifth, and tenth series are presented. + + + +TIME FOR SERIES OF TRIALS + + 1st series 2nd series 5th series 10th series +Skirrl 35 min. 20 min. 14 min. 10 min. +Sobke 14 " 17 " 10 " 9 " (8th series) +Julius 12 " 11 " 14 " 9 " + + + +It is also noteworthy that Julius in the presence of visitors or under +other unusual conditions worked steadily and well, whereas the monkeys, +and especially Sobke, tended to be distracted and often refused to work +at all. + +Almost from the beginning of his work on problem l, Julius began to +develop the tendency to enter immediately the open door nearest the +starting point. In case the group of open doors lay to the right of the +middle of the apparatus, this method naturally yielded success; whereas +if the group included doors to the left of the middle, it resulted in +failure. Obviously it was a most unsatisfactory method, and although it +enabled him to make more right than wrong first choices, it prevented +him from increasing the number of right choices, and as table 1 +indicates, it maintained the ratio of 1 right to .67 wrong first choices +for eight successive days. + +On April 23 a break occurred in which the number of correct choices was +reduced from six to five. Julius worked very rapidly and with almost no +hesitation in choosing. My notes record "he seems to miss the point +wholly. It is doubtful whether the punishment is sufficiently severe." +At this time he was being punished by thirty seconds confinement in each +wrong box, the interval having been held fairly steadily from the first +series of experiments. On April 26 it was increased to sixty seconds, in +an effort to break him of the habit of choosing the "nearest" door. But +he became extremely restless under the longer confinement and tried his +best to raise the entrance and exit doors. Since there was at this time +no mechanism for locking them when closed, it was difficult for the +experimenter to prevent him from escaping by way of the entrance door or +from raising the exit door sufficiently to obtain the food. Indeed, the +longer confinement worked so unsatisfactorily that on the following day +I substituted for it the punishment of forcing him to raise the entrance +door of the wrong box in order to escape for a new choice. He was +rewarded with food in the alleyway H, beside door 15 (figure 17), only +when he chose correctly on first attempt. + +This method discouraged him extremely and proved wasteful of time. +Consequently, in a second series on the same date return was made to the +former method, and he was rewarded with food whenever he found the right +box. But on April 28, the two methods were again employed, the first in +the initial series and the second in a final series of trials. The +animal's persistent attempts to raise the doors gave the experimenter so +much trouble that on April 29 barbed wire was nailed over the windows of +the entrance doors with the hope that it might prevent him from working +at them. But he quickly learned to place his fingers between the barbs +and raise the doors as effectively as ever. + +On April 30 the reward of food was given only when the first choice was +that of the right box and in that event it was placed in the alleyway H +as stated above. + +As it seemed absolutely essential to break the unprofitable habit of +choosing the nearest door, on May 3 a new series of settings was +presented, in which only the doors to the left of the middle of the row +of nine boxes were used as right doors. That is, in this new series, +doors 1 to 4 occur as right doors; 5 to 9 do not. As punishment for +wrong choices on this date, Julius was confined in the wrong box from +one to five minutes. It was difficult to keep him in, but by means of +cords which had been attached to the doors, this was successfully +accomplished. Yet another and slightly different series of settings was +employed on May 4, and this, proving satisfactory, was continued in use +until the end of the experiment, with punishment ranging from sixty to +one hundred and twenty seconds for each mistake. + +Naturally the modification of settings introduced May 3 greatly +increased the proportion of wrong first choices. Indeed, as appears in +table 8, the ratio of right to wrong immediately changed from 1:0.67 to +1:4.00. Between May 3 and May 10, no steady and consistent improvement +in method or in the number of correct first choices occurred, and on the +last named date, Julius chose correctly only three times in his ten +trials. At this time there was, as my notes record, no satisfactory +indication of progress, and the status of the experiment seemed +extremely unsatisfactory in as much as in spite of the experimenter's +best efforts to break up the habit of choosing the nearest door, the +orang utan still persisted, to a considerable extent, in the use of this +method. The only encouraging feature of the results was an evident +tendency to choose somewhat nearer the left end of a group than +previously. + + + + +TABLE 8 + +Results for Orang utan in Problem 1 + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | | | R | W | R | W | of + | trials | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + April | | | | | | | | | | | | | | | | + 13 | 1- 10 | 3.1 | 8 | 4.3 | 7 | 4.2 | 7.6 | 5 | 4 | 7 | 3.1 | 5 | 5 | 5 | 5 | 1:1.00 + 14 | 11- 20 | 3.2.1 | 8 | 4.3 | 7 | 4.4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 15 | 21- 30 | 3.2.1 | 8 | 4.3 | 7 | 4.5.5.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 16 | 31- 40 | 3.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | 6 | 4 | 1:0.67 + 17 | 41- 50 | 3.2.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 19 | 51- 60 | 3.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 20 | 61- 70 | 2.1 | 8 | 4.3 | 7 | 5.3.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 21 | 71- 80 | 3.1 | 8 | 4.3 | 7 | 5.4.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | 6 | 4 | 1:0.67 + 22 | 81- 90 | 3.1 | 8 | 5.3 | 7 | 6.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | 6 | 4 | 1:0.67 + 23 | 91-100 | 3.2.1 | 8 | 5.3 | 7 | 4.3.2 | 6 | 5 | 5.4 | 7 | 3.2.1 | 5 | 5 | 5 | 5 | 1:1.00 + 24 | 101-110 | 3.2.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | 6 | 4 | 1:0.67 + 26 | 111-120 | 3.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 5.4 | 7 | 3.1 | 5 | 5 | 5 | 5 | 1:1.00 + 27 | 121-130 | 3.2.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 6.5 | 5.8.6.4 | 7 | 3.3.3.1 | 4 | 6 | | | + " | 131-140 | 3.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 |10 |10 | 1:1.00 + 28 | 141-150 | 3.2.1 | 8 | 3 | 7 | 5.4.2 | 6 | 5 | 4 | 7 | 3.1 | 7 | 3 | | | + " | 151-160 | 3.1 | 8 | 3 | 7 | 3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 7 | 3 |14 | 6 | 1:0.43 + 29 | 161-170 | 3.1 | 8 | 4.3 | 7 | 4.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 | | | + " | 171-180 | 3.2.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 |12 | 8 | 1:0.67 + | | | | | | | | | | | | | | | | + 30 | 181-190 | 3.1 | 8 | 4.3 | 7 | {4.5.6.4 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | | | + | | | | | | {5.6.4.2 | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 191-200 | 3.1 | 8 | 4.5.6.7.3 | 7 | 4.5.3.2 | 6 | 5 | 4 | 7 | 3.2.1 | 6 | 4 |12 | 8 | 1:0.67 + May | | | | | | | | | | | | | | | | + 1 | 201-210 | 3.1 | 8 | 4.3 | 7 | 3.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 | | | + " | 211-220 | 3.2.1 | 8 | 4.3 | 7 | 4.2 | 6 | 5 | 4 | 7 | 3.1 | 6 | 4 |12 | 8 | 1:0.67 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 2.3.4.5 | | | | | | | 2.3.4.5 | | | | | + | | 1.2.3 | 3.4.5.6.7 | 6.7.8 | 1.2.3 | 3.4.5.6.7 | 4.5.6.7.8.9 | 2.3.4.5 | 1.2.3 | 4.5.6.7.8.9 | 6.7.8.9 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 3 | 221-230 | 3.1 | 4.3 | 4.2 | 3.1 | 4.3 | 4 | 4.3.2 | 3.1 | 4 | 4.3.2 | 2 | 8 | 2 | 8 | 1:4.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | 2.3.4.5 | 4.5.6.7 | | | | | 2.3.4.5 | | | | | | + | | 1.2.3 | 3.4.5.6.7 | 6.7.8 | 8.9 | 2.3.4.5 | 3.4.5.6 | 1.2.3 | 4.5.6.7.8 | 6.7.8.9 | 1.2.3 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 4 | 231-240 | 3.2.1 | 4.3 | 4.2 | 4 | 4.3.2 | 4.3 | 3.2.1 | 4 | 3.2 | 3.2.1 | 2 | 8 | 2 | 8 | 1:4.00 + 5 | 241-250 | 2.1 | 3 | 3.2 | 4 | 3.2 | 4.3 | 3.2.1 | 4 | 3.2 | 3.2.1 | 3 | 7 | 3 | 7 | 1:2.33 + 6 | 251-260 | 2.1 | 3 | 2 | 4 | 3.2 | 3 | 2.1 | 4 | 3.2 | 2.1 | 5 | 5 | 5 | 5 | 1:1.00 + 7 | 261-270 | 2.1 | 3 | 3.2 | 4 | 3.2 | 3 | 2.1 | 4 | 4.2 | 2.1 | 4 | 6 | 4 | 6 | 1:1.50 + 8 | 271-280 | 2.1 | 4.3 | 4.3.2 | 4 | 3.2 | 4.3 | 3.1 | 4 | 3.2 | 2.1 | 2 | 8 | 2 | 8 | 1:4.00 + 10 | 281-290 | 1 | 4.3 | 4.2 | 4 | 3.2 | 4.3 | 2.1 | 4 | 3.2 | 2.1 | 3 | 7 | 3 | 7 | 1:2.33 + 11 | 291-300 | 1 | 3 | 2 | 4 | 2 | 3 | 1 | 4 | 2 | 1 |10 | 0 |10 | 0 | 1:0.00 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + | | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 12 | 301-310 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 |10 | 0 |10 | 0 | 1:0.00 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + + + +A series of correct first choices was obtained on May 11, greatly to the +surprise of the experimenter, for no indication had previously appeared +of this approaching solution of the problem. It seemed possible, +however, that the successes were accidental, and it was anticipated that +in a control series Julius would again make mistakes. But on the +following day, May 12, the presentation of the original series of ten +settings, which, of course, differed radically from the settings used +from May 4 to May 11 was responded to promptly, readily, and without a +single mistake. Julius had solved his problem suddenly and, in all +probability, ideationally. + +Only three reactive tendencies or methods appeared during Julius's work +on this problem: (a) choice of the open door nearest to the starting +point (sometimes the adjacent boxes were entered); (b) a tendency to +avoid the "nearest" door and select instead one further toward the left +end of the group; (c) direct choice of the first door on the left. + +The curve of learning plotted from the daily wrong choices and presented +in figure 18, had it been obtained with a human subject, would +undoubtedly be described as an ideational, and possibly even as a +rational curve; for its sudden drop from near the maximum to the base +line strongly suggests, if it does not actually prove, insight. + +Never before has a curve of learning like this been obtained from an +infrahuman animal. I feel wholly justified in concluding from the +evidences at hand, which have been presented as adequately as is +possible without going into minutely detailed description, that the +orang utan solved this simple problem ideationally. As a matter of fact, +for the solution he required about four times the number of trials which +Sobke required and twice as many as were necessary for Skirrl. Were we +to measure the intelligence of these three animals by the number of +trials needed in problem 1, Sobke clearly would rank first, Skirrl +second, and Julius last of all. But other facts clearly indicate that +Julius is far superior to the monkeys in intelligence. We therefore must +conclude that _where very different methods of learning appear, the +number of trials is not a safe criterion of intelligence._ The +importance of this conclusion for comparative and genetic psychology +needs no emphasis. + + +_Problem 2. Second from the Right End_ + +Julius was given four days' rest before being presented with problem 2. +He was occasionally fed in the apparatus, but regular continuation of +training was not necessary to keep him in good form. During this rest +interval, locks were attached to the doors of the apparatus so that the +experimenter by moving a lever directly in front of him could fasten +either one or both of the doors of a given box by a single movement. On +May 13 Julius was given opportunity to obtain food from each of the +boxes in turn, and trial of the locks was made in order to familiarize +him with the new situation. He very quickly discovered that the doors +could not be raised when closed, and after two days of preliminary work, +he practically abandoned his formerly persistent efforts to open them. +The locks worked satisfactorily from a mechanical point of view as well +as from that of the adaptation of the animal to the modified situation. + +Problem 2 was regularly presented for the first time on May 17, on which +day a single series was given. The period of punishment adopted was +twenty seconds, and for each successful choice a small piece of banana +was given as a reward. After the first trial in this series, in which +Julius repeatedly entered the first box at the left, that is box 7, +there was but slight tendency to reenter the first box at the left of +the group. Instead, Julius developed the method of moving box by box +toward the right end of the group. The choices were made promptly, and +their systematic character enabled the animal to obtain his reward +fairly quickly, in spite of the large number of mistakes. + +In the second series, the orang utan developed the interesting trick of +quickly dodging out of the wrong box before the experimenter could lower +the door behind him. This he did only after having been punished for +many wrong choices to the point of discouragement. The trick was easily +broken up by the sudden lowering of the entrance door as soon as he had +passed under it. + +There appeared on May 21 an unfavorable physical condition which +manifested itself, first of all through the eyes which appeared dull and +bloodshot. On the following day they were inflamed and the lids nearly +closed. Julius refused to eat, and experimentation was impossible. Until +June 2 careful treatment and regulation of diet was necessary. He passed +through what at the time seemed a rather startling condition, but +rapidly regained his usual good health, and on June 3, although somewhat +weak and listless, he again worked fairly steadily. + +Since it was now possible to lock the doors and confine the animal for +any desired period, on June 5 the interval of punishment was made sixty +seconds, and a liberal quantity of banana, beet, or carrot was offered +as reward. No increase in the number of successful choices appeared, and +Julius showed discouragement. Sawdust had been strewn on the floor, and +in the intervals between trials as well as during confinement in wrong +boxes, he took to playing with the sawdust. He would take it up in one +hand and pour it from hand to hand until all had slipped through his +fingers, then he would scrape together another handful and go through +the same process. Often he became so intent on this form of amusement +that even when the exit door was raised, he would not immediately go to +get the food. + +The reactive tendencies which appeared in the work on problem 2 will now +be presented in order, since I shall have to refer to them repeatedly, +and the list will be more useful to the reader at this point than at the +conclusion of the presentation of daily results. The following is not an +exhaustive list but includes only the most important and conspicuous +tendencies or methods together with the dates on which they were most +apparent. + +(a) May 17, choice of first box at left of group or near it, then the +next in order, and so on, until the second from the right was reached. +This method with irregularities and certain definite skipping was used +at various times, sometimes over periods of several days, during the +course of the work. + +(b) June 3, preference for number 3 and number 4 developed immediately +after the orang utan's illness and when he was working rather +listlessly. + +On June 9 and 10, the original tendency (a) reappeared and persisted for +a number of series. + +(c) June 14, a tendency to choose the box at or near the right end of a +group, and then the one next to it. In connection with this tendency, +which of course required only two choices in any given trial, interest +in playing with the sawdust on the floor developed. + +Again on June 21, the animal returned to the use of tendency (a). + +(d) June 29, movement to box at right end of group, hesitation before +it, and turning through a complete circle so that the second box from +the right was faced. This, the correct box, was often promptly entered. +This method, if persisted in, would obviously have yielded solution of +the problem. + +(e) July 5, approach to and pretense to enter the box next to the right +end (right one), and then choice of some other box. This _feint_ is +peculiarly interesting, and its origin and persistence are difficult to +account for. + +(f) In connection with the tendency to pretend that he was going to +enter the second box from the right end, Julius developed also the +tendency to turn around in front of the box at the right end, starting +sometimes to back into it, and then to enter, instead, the box second +from the end. + +(g) July, 6 and 7, a fairly definite tendency to take the one next in +order or, instead, to go directly to the right box. + +(h) July 10, direct first choices without approach to other boxes +appeared for the first time on this date. + +For this problem, it proved impossible to establish and maintain uniform +conditions of experimentation. Instead, because of the failure of the +animal to improve and the tendency to discouragement, both punishment +and reward had to be altered from time to time, and other and more +radical changes were occasionally made in the experimental procedure. +Below for the sake of condensed and consecutive presentation, the most +important conditions from day to day are arranged in tabular form: + + + +CONDITIONS OF EXPERIMENT FROM DAY To DAY FOR PROBLEM 2 + +Date Punishment Reward + +May 17 ............. 20 sec. confinement ........ Food in right box for each + (Aid after 10 trials) trial + + " 18 to 21 ........ 30 sec. confinement ........ Food (banana) in right box + for each trial + + " 22 to June 2 .... Illness, no experiments + +June 3 ............... 15 sec. confinement ........ Food (banana) in right box + for each trial + + " 4 ............... 30 " " ............. Food (banana) in right box + for each trial + + " 5-10 ............ 60 " " ............. Beet, carrot and loquat, in + addition to banana + + " 11 .............. 10 to 30 sec. confinement .. Beet, carrot and loquat, in + addition to banana + + " 12 to 15 ........ 60 sec. confinement ........ Beet, carrot and loquat, in + addition to banana + + " 16 .............. 60 " " ............. Banana and sweet corn--former + preferred + + " 17 (1st series). 60 sec. confinement ........ Food (banana, as in early + series) + + " 17 (2nd series). No confinement in wrong box; Food only for correct first + but instead, return to choices + starting point by way of + alleys + + " 18 to 22 ........ No confinement in wrong box; Food only for correct first + but instead, return to choices + starting point by way of + alleys + + " 22 (2nd series). No punishment; allowed to Food for each trial + enter boxes until right + one was found + " 23 .............. Return to starting point. + After five wrong choices + of a given box the animal + was held for 60 secs. in + one of the boxes and was + then released by way of + the exit door and rewarded + when the right one was + chosen + + " 23 (2nd series). No punishment .............. Reward for each trial + + " 24 (1st series). Return to starting point. .. Food only for correct first + choices + + " 24 (2nd series). No punishment .............. Reward for each trial + + " 25-30 ........... Same as on 24th ............ + +July 1 (1st series). No punishment .............. " " " " + + " 1 (2nd series). Return to starting point ... Reward only for correct first + choices + " 2-8 ............. Same as on July 1 .......... + + " 8 (2nd series). No punishment .............. Reward for each trial + + " 8 (3rd series). Return to starting point ... Reward only for correct first + choices + + " 9-10 ............ Same as for July 8 (3rd series) + + " 10 (2nd series). Momentary confinement in ..... Reward for each correct choice + wrong boxes + + " 12 .............. Return to starting point ..... Reward for correct first choice + + " 12 (2nd series). 30 sec. confinement .......... Reward for each correct choice + + " 12 (3rd series). 5 " " ............... " " " " " + + " 13 .............. 30 " " ............... " " " " " + + " 14-17 ........... Return to starting point ..... Reward for correct first choices + + " 17 (2nd series). 60 sec. confinement .......... Reward for each correct choice + + " 19 .............. 30 " " ............... " " " " " + + " 20-26 ........... 10 " " ............... " " " " " + + " 27-30 ........... Right box indicated by slight Reward in each right box + raising of exit door + momentarily. + No punishment + + " 30 (2nd series). Return to starting point ..... Reward for correct first choices + + " 31 .............. " " " " ..... " " " " " + + " 31 (2nd series) + to Aug. 10 .... 10 to 60 sec. confinement .... Reward for each correct choice + +Aug. 10 (2nd series). Threatened with whip ......... " " " " " + + " 11 (1st series). " " " ........... " " " " " + + " 11 (2nd series). 10 sec. confinement .......... " " " " " + + " 12 .............. Threatened with whip ......... " " " " " + + " 12 (2nd series). 10 sec. confinement .......... " " " " " + + " 19 .............. 10 " " ............... " " " " " + + " 19 (2nd series). Threatened with whip ......... " " " " " + + + + +With the above reactive tendencies and modifications of method in mind +we may continue our description of results. On June 9 there developed a +tendency to increase the magnitude of the original error by choosing +nearer the left end of the groups. This is odd, since one would +naturally suppose that an animal as intelligent as the orang utan would +tend to avoid the general region in which success was never obtained and +to focus attention on the right, as contrasted with the wrong end of +each group. _It obviously contradicts the law of the gradual elimination +of use less activities._ In other words, it is wholly at variance with +the principle of trial and error exhibited by many infrahuman organisms. +Julius, although making many mistakes, worked diligently and, for the +most part, fairly rapidly. The day's work proved most important because +of the change in method and also because of the appearance of +hesitation, the rejection of certain boxes, and the definite choice of +others. My notes record "this is a most important day for Julius in +problem 2;" but subsequent results do not clearly justify this prophecy. + +The method of choosing the first box at the left and then of moving down +the line until the right one was reached was so consistently followed +that during a number of days it was possible for me to predict almost +every choice. Indeed, to satisfy my curiosity in this matter during a +number of series I guessed in advance the box which would be chosen. The +percentages of correct guesses ranged from ninety to one hundred. June +10, for example, yielded two series for which the ratio of right to +wrong first choices was 0 to 10, and in which the method described above +was used consistently throughout. + +It was inevitable that punishment by confinement and the discouragement +resulting therefrom should interfere with the regularity of work and +make it extremely difficult to obtain strictly comparable results from +series to series and from day to day. The data for this problem, as +presented in table 9, have values quite different from those for the +monkeys, chiefly because of the more variable conditions of observation. + +It was occasionally noted that the disintegration of a definite method +and the disappearance of the tendency on which it depended occurred +rather suddenly. Frequently it happened that having used an inadequate +method fairly persistently on a given day, the animal would on the +following day exhibit a wholly different method. Even over night a new +method might develop. In the monkeys, although there was occasionally +something comparable with this, it was by no means so evident. + + + +TABLE 9 + +Results for Orang utan in Problem 2 + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | 1.2.3.4.5 | | | R | W | R | W | of + | trials | 7.8.9 | 1.2.3.4 | 2.3.4.5.6.7 | 1.2.3.4.5.6 | 4.5.6.7.8 | 1.2.3 | 2.3.4.5 | 6.7.8.9 | 1.2.3.4 | 3.4.5.6.7.8 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + May | | {7.7.7.7 | | | | | | | | | | | | | | + 17 | 1- 10 | {7.7.7.7 | 1.1.3 | 2.4.6 | 2.3.4.5 | 4.5.7 | 3.2 | 2.3.4 | {2.3.4.5 | 1.2.3 | 3.4.5.6.7 | 0 |10 | 0 |10 | 0:10.00 + | | {7.7.8 | | | | | | | {6.7.8 | | | | | | | + | | | | | | | | | | | {4.5.6.8 | | | | | + 18 | 11- 20 | 7.8 | 1.3 | 3.4.5.6 | 2.4.5 | 4.5.6.7 | 2 | 2.3.4 | {2.3.4.5 | 1.2.3 | {8.8.8.3 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | | {6.7.8 | | {4.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | {2.4.7.7.2 | | | | | | | {5.3.4.5 | | | | | + 19 | 21- 30 | 7.8 | 1.3 | {5.7.7.2 | 5 | 4.6.8.4.7 | 1.2 | 2.3.4 | 5.8 | 3 | {6.8.4.5 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | {3.2.4.6 | | | | | | | {3.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + 20 | 31- 40 | {7.9.7.7 | 3 | 4.5.6 | 4.5 | 5.6.7 | 2 | 4 | 5.6.7.8 | 3 | 5.6.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | {9.7.8 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 21 | 41- 50 | 7.8 | 3 | 3.4.5.6 | 4.5 | 4.5.6.7 | 2 | 3.4 | 4.5.6.8 | 3 | 4.5.6.7 | 3 | 7 | 3 | 7 | 1: 2.33 + June | | | | | | | | | | | | | | | | + 3 | 51- 60 | 7.8 | 3 | 4.5.6 | 3.4.5 | 4.5.6.7 | 3.1.2 | 3.4 | {3.7.9.7 | 3 | 4.5.6.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | | | | | | | | {9.7.6.8 | | | | | | | + | | | | | | | | | | | | | | | | + 4 | 61- 70 | 7.8 | 3 | 4.5.6 | 4.5 | 4.5.6.7 | 3.3.1.2 | 4 | 4.5.6.7.8 | 3 | 4.5.6.7 | 3 | 7 | 3 | 7 | 1: 2.33 + 5 | 71- 80 | 7.9.7.8 | 3 | 3.4.5.6 | 3.6.3.4.5 | 4.7 | 3.1.2 | 4 | 3.4.5.6.7.8 | 3 | 4.5.6.7 | 3 | 7 | | | + " | 81- 90 | 7.8 | 3 | 3.4.5.6 | 3.4.5 | 4.5.6.7 | 2 | 3.4 | 3.4.5.6.7.8 | 2.3 | 4.5.6.7 | 2 | 8 | 5 |15 | 1: 3.00 + | | | | | | | | | | | | | | | | + 7 | 91- 100 | 7.8 | 3 | 4.5.6 | 4.5 | 4.5.6.7 | 1.2 | 3.4 | {3.4.5.6 | 2.3 | {3.4.5.6 | 1 | 9 | 1 | 9 | 1: 9.00 + | | | | | | | | | {7.8 | | {8.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + 8 | 101- 110 | 7.8 | 3 | 4.5.6 | 4.5 | 4.5.6.7 | 2 | 3.4 | 4.5.6.7.8 | 3 | 4.5.6.7 | 3 | 7 | | | + " | 111- 120 | 7.8 | 3 | 4.5.6 | 3.4.5 | 5.6.7 | 2 | 5.5.2.3.4 | 4.5.6.7.8 | 4.4.1.2.3 | 4.5.6.7 | 2 | 8 | 5 |15 | 1: 3.00 + | | | | | | | | | | | | | | | | + 9 | 121- 130 | 7.8 | 2.3 | 4.5.6 | 4.5 | 4.5.6.7 | 2 | 3.4 | {2.3.4.5 | 1.2.3 | 3.4.5.6.7 | 1 | 9 | | | + | | | | | | | | | {6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 131- 140 | 7.8 | 1.2.3 | 2.3.4.5.6 | 5 | 4.5.6.7 | 1.2 | 2.3.4 | 6.7.8 | 2.3 | 3.4.5.6.7 | 1 | 9 | 2 |18 | 1: 9.00 + | | | | | | | | | | | | | | | | + 10 | 141- 150 | 7.8 | 1.2.3 | 2.3.4.5.6 | 1.2.3.4.5 | 4.5.6.7 | 1.2 | 2.3.4 | {1.2.3.4 | 1.2.3 | 3.4.5.6.7 | 0 |10 | | | + | | | | | | | | | {5.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 151- 160 | 7.8 | 1.2.3 | 2.3.4.5.6 | 1.2.3.4.5 | 4.5.6.7 | 1.2 | 2.3.4 | {1.2.3.4 | 1.2.3 | 3.4.5.6.7 | 0 |10 | 0 |10 | 0:10.00 + | | | | | | | | | {5.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + 11 | 161- 170 | 8 | {4.1.2.4.1 | 2.3.4.5.6 | 5 | 6.7 | {3.1.3.1 | 5.2.3.4 | 2.6.7.8 | 4.1.2.3 | 8.5.6.7 | 2 | 8 | | | + | | | {4.1.4.1.3 | | | | {3.1.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 171- 180 | 9.7.8 | 4.3 | 5.6 | 4.5 | 7 | 3.1.2 | 5.4 | 8 | 4.2.3 | 7 | 3 | 7 | 5 |15 | 1: 3.00 + 12 | 181- 190 | 7.9.7.9.8 | 1.2.3 | 3.4.5.6 | 6.4.5 | 5.6.7 | 2 | 5.3.4 | 7.8 | 4.1.2.3 | 4.5.6.7 | 1 | 9 | 1 | 9 | 1: 9.00 + 14 | 191- 200 | 9.8 | 3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | 6.7.8 | 4.2.3 | 7 | 2 | 8 | | | + " | 201- 210 | 8 | 2.3 | 7.6 | 6.5 | 8.7 | 3.1.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | 5 |15 | 1: 3.00 + | | | | | | | | | | | | | | | | + 15 | 211- 220 | {7.9.7.9 | 4.2.3 | 6 | 5 | 8.7 | 3.2 | 5.4 | 9.8 | 4.3 | 7 | 3 | 7 | | | + | | {7.9.8 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 221- 230 | 9.8 | 4.3 | 7.6 | 6.5 | 5.6.7 | 1.2 | 2.3.4 | 3.4.5.6.7.8 | 4.3 | 7 | 1 | 9 | 4 |16 | 1: 4.00 + 16 | 231- 240 | 7.9.8 | 3 | 7.6 | 6.5 | 8.7 | 2 | 5.4 | 5.6.7.8 | 4.1.4.3 | 8.7 | 2 | 8 | | | + " | 241- 250 | 9.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 6.7.8 | 4.3 | 6.7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | | | | | | | | | | | + 17 | 251- 260 | 9.8 | 4.3 | 7.6 | 6.5 | {6.5.4.6 | 3.2 | 5.4 | 6.5.6.7.8 | 3 | 5.6.7 | 1 | 9 | | | + | | | | | | {5.4.5.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | {6.6.6.5.6 | | | | | | | | | | + | | | | | | {5.5.5.6.6 | | | | | | | | | | + " | 261- 270 | {9.7.7.7 | 4.4.4.4.3 | 6 | 5 | {6.6.6.6.6 | {3.3.3.3 | 4 | {4.5.4.5.4 | 3 | {5.5.5.5 | 4 | 6 | 5 |15 | 1: 3.00 + | | {7.7.7.8 | | | | {6.5.4.5 | {3.3.2 | | {5.6.7.8 | | {5.5.8.7 | | | | | + | | | | | | {6.5.5.4 | | | | | | | | | | + | | | | | | {4.5.6.7 | | | | | | | | | | + | | | | | | | | | | | | | | | | + 18 | 271- 280 | {7.7.7.7 | 4.4.4.4.3 | 5.5.5.5.6 | 5 | {5.5.5.6 | {3.3.3. | 4 | {4.6.5.6 | 4.4.3 | 5.6.4.7 | 2 | 8 | 2 | 8 | 1: 4.00 + | | {7.7.8 | | | | {5.5.6 | {3.3.2 | | {6.7.4.8 | | | | | | | + | | | | | | | | | | | | | | | | + | | {7.7.7.9 | | | | | | | | | | | | | | + 19 | 281- 290 | {9.9.9.7 | {4.4.4 | {5.7.7 | 5 | 5.7 | {3.3.3.3 | 4 | 5.8 | {4.4.4.4 | {6.5.6.5 | 2 | 8 | | | + | | {7.7.8 | {4.4.3 | {7.4.6 | | | {3.3.2 | | | {4.4.3 | {5.5.7 | | | | | + | | | | | | | | | | | | | | | | + " | 291- 300 | 7.7.7.7.8 | 4.4.4.4.3 | 5.5.6 | 5 | {5.6.6.5.6 | 3.3.2 | {5.5.5.5 | 5.6.8 | 4.4.3 | 6.6.6.7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | {6.6.6.7 | | {3.4 | | | | | | | | + | | | | | | | | | {5.6.6.6.7 | | | | | | | + 21 | 301- 310 | 7.7.8 | 4.4.3 | 5.6 | 5 | {6.6.6.5 | {3.3.3.3 | 5.5.5.2.4 | {3.4.3.5.5 | {4.2.2.4 | 5.3.7 | 1 | 9 | | | + | | | | | | {5.6.5.7 | {3.2 | | {1.1.2.4.7 | {4.3 | | | | | | + | | | | | | | | | {2.3.2.2.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 311- 320 | {7.7.7.7 | 1.1.1.2.3 | {5.5.4.2 | 1.1.6.5 | 4.6.7 | 1.3.2 | {2.2.2.2 | {1.1.2.3 | {2.2.2.4 | {6.3.3.8 | 0 |10 | 1 |19 | 1:19.00 + | | {7.7.8 | | {2.5.6 | | | | {2.2.3.4 | {6.6.6.8 | {2.3 | {4.8.7 | | | | | + | | | | | | | | | | | | | | | | + 22 | 321- 330 | 7.8 | {2.4.2.1.4 | 6 | 5 | 6.6.8.7 | 3.2 | 5.5.3.3.4 | 3.3.7.7.8 | 4.4.4.2.3 | 6.7 | 2 | 8 | | | + | | | {4.4.4.3 | | | | | | | | | | | | | + " | 331- 340 | 7.8 | 3 | 6 | 5 | 6.7 | 3.2 | 5.4 | 6.7.8 | 3 | 5.6.7 | 4 | 6 | 6 |14 | 1: 2.33 + | | | | | | | | | | | | | | | | + 23 | 341- 350 | 7.8 | 4.2.4.3 | 6 | 5 | 6.7 | {3.3.3.1 | 5.5.4 | {7.5.4.3 | 4.4.4.3 | {6.6.3.6 | 2 | 8 | | | + | | | | | | | {3.3.3.2 | | {6.7.7.8 | | {8.6.8.7 | | | | | + | | | | | | | | | | | | | | | | + " | 351- 360 | 7.8 | 4.4.3 | 6 | 6.5 | 6.7 | 3.3.2 | 5.4 | {6.7.6.5 | 4.3 | 5.6.7 | 1 | 9 | 3 |17 | 1: 5.67 + | | | | | | | | | {7.6.8 | | | | | | | + | | | | | | | | | | | | | | | | + 24 | 361- 370 | 7.8 | 4.4.2.3 | 7.7.6 | 6.6.4.5 | 7 | {3.3.3.3 | 5.4 | 8 | 4.4.3 | 5.6.7 | 2 | 8 | | | + | | | | | | | {3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 371- 380 | 8 | 4.3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 7.6.8 | 4.3 | 7 | 4 | 6 | 6 |14 | 1: 2.33 + | | | | | | | | | | | | | | | | + 25 | 381- 390 | 8 | 4.4.3 | 7.7.7.6 | {6.6.6.6 | 8.6.7 | 3.1.2 | 5.3.5.4 | 8 | 3 | 7 | 4 | 6 | | | + | | | | | {6.4.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 391- 400 | 8 | 4.3 | 6 | 5 | 6.5.8.7 | 3.2 | 5.4 | 8 | 3 | 8.7 | 5 | 5 | 9 |11 | 1: 1.22 + | | | | | | | | | | | | | | | | + 26 | 401- 410 | 9.9.9.8 | 3 | {7.7.7.7.3 | {6.6.6.6 | 8.8.8.7 | 3.2 | {5.5.5.5 | 7.8 | {4.4.4.4 | 6.6.8.8.7 | 1 | 9 | | | + | | | | {3.7.7.6 | {6.6.5 | | | {5.5.4 | | {4.4.3 | | | | | | + | | | | | | | | | | | | | | | | + " | 411- 420 | 8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 8.7 | 3 | 7 | 4 |16 | 1: 4.00 + | | | | | | | | | | | | | | | | + 28 | 421- 430 | 8 | {4.4.4.4 | 7.6 | {6.6.3.6 | 7 | {3.3.3.3 | 5.5.5.4 | 9.7.7.5.8 | 4.4.4.3 | 8.7 | 2 | 8 | | | + | | | {4.4.3 | | {6.6.6.5 | | {3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 431- 440 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 4.3 | 7 | 4 | 6 | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {7.6.5.4 | | | | | | | + " | 441- 450 | 8 | 4.3 | 7.6 | 6.5 | 8.7 | 3.2 | 5.4 | {3.2.1.5 | 4.3 | 7 | 2 | 8 | 8 |22 | 1: 2.75 + | | | | | | | | | {7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + 29 | 451- 460 | 8 | 3 | 6 | 6.6.6.5 | 8.6.7 | {3.3.3.3 | 5.4 | 8 | 4.3 | 7 | 5 | 5 | | | + | | | | | | | {3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 461- 470 | 8 | 4.3 | 6 | 5 | 8.7 | 3.2 | 3.2.3.4 | 7.8 | 4.3 | 7 | 4 | 6 | | | + " | 471- 480 | 8 | 4.4.3 | 7.7.6 | 6.6.5 | 7 | 2 | 5.5.5.5.5.4 | 7.8 | 4.4.3 | 7 | 4 | 6 |13 |17 | 1: 1.31 + | | | | | | | | | | | | | | | | + 30 | 481- 490 | 8 | {4.4.4.4 | 7.7.6 | 6.6.6.5 | 8.6.6.5.7 | {3.1.3.3 | 5.5.5.4 | 8 | 4.4.4.3 | 7 | 3 | 7 | | | + | | | {4.4.3 | | | | {3.3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 491- 500 | 8 | 4.3 | 7.7.7.6 | 6.6.5 | 8.8.7 | 3.3.3.3.2 | 5.4 | {9.9.7.4 | 3 | 8.8.7 | 2 | 8 | 5 |15 | 1: 3.00 + | | | | | | | | | {9.6.8 | | | | | | | + July | | | | | | | | | | | | | | | | + 1 | 501- 510 | 9.7.9.8 | 4.3 | 6 | 6.5 | 8.6.7 | 3.3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 511- 520 | {9.7.7.7 | 4.3 | 7.6 | 6.4.5 | 7 | 3.2 | 4 | 8 | 4.4.4.3 | 8.6.5.6.7 | 3 | 7 | 6 |14 | 1: 2.33 + | | {7.9.8 | | | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + 2 | 521- 530 | 9.8 | 3 | 7.5.7.6 | 6.4.5 | 8.7 | 2 | 4 | 8 | 3 | 7 | 6 | 4 | | | + | | | | | | | | | | | | | | | | + " | 531- 540 | 9.9.7.8 | 3 | 7.4.6 | 5 | 6.6.7 | 3.3.2 | 3.4 | 7.3.5.4.8 | 4.3 | {8.8.6.5 | 2 | 8 | 8 |12 | 1: 1.50 + | | | | | | | | | | | {4.5.7 | | | | | + | | | | | | | | | | | | | | | | + 3 | 541- 550 | 8 | 4.3 | 6 | {6.6.6.6 | 6.8.7 | 3.3.3.2 | 5.5.4 | 9.6.9.6.8 | 4.3 | 7 | 3 | 7 | | | + | | | | | {6.6.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 551- 560 | 9.9.7.8 | 4.3 | 6 | 5 | 8.6.5.7 | {3.3.3.3 | 5.4 | {7.6.5.7 | 3 | 7 | 4 | 6 | 7 |13 | 1: 1.86 + | | | | | | | {3.2 | | {9.7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + 5 | 561- 570 | 8 | 4.3 | 7.6 | 6.5 | {8.8.8.8 | {3.3.3.3 | 5.5.5.5.4 | 8 | 4.4.4.3 | 8.8.8.8.7 | 2 | 8 | | | + | | | | | | {8.8.7 | {3.3.3.2 | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 571- 580 | 9.8 | 4.4.4.3 | 6 | 6.5 | 8.8.7 | {3.3.3.3.3 | {5.5.5.5.5 | 7.6.8 | 4.4.3 | 7 | 2 | 8 | 4 |16 | 1: 4.00 + | | | | | | | {3.3.3.2 | {5.5.5.4 | | | | | | | | + | | | | | | | | | | | | | | | | + 6 | 581- 590 | 9.8 | 4.3 | 7.7.6 | 6.6.5 | 7 | 2 | 5.4 | 7.8 | 4.3 | 7 | 3 | 7 | | | + " | 591- 600 | 8 | 3 | 6 | 4.5 | 6.6.6.7 | 2 | 5.3.5.4 | 8 | 4.4.3 | 8.8.8.7 | 5 | 5 | 8 |12 | 1: 1.50 + 7 | 601- 610 | 8 | 1.3 | 6 | 5 | 6.5.7 | 2 | 5.4 | 5.6.6.6.7.8 | 4.3 | 7 | 5 | 5 | | | + | | | | | | | | | | | | | | | | + " | 611- 620 | {9.7.7.7.9 | 3 | 6 | 5 | 6.5.6.5.7 | 3.2 | 5.4 | 7.9.7.9.8 | {4.4.4.4 | 8.7 | 3 | 7 | 8 |12 | 1: 1.50 + | | {7.7.7.8 | | | | | | | | {4.4.4.3 | | | | | | + | | | | | | | | | | | | | | | | + 8 | 621- 630 | {9.9.9.7.9 | 4.3 | 6 | 6.6.6.5 | {8.8.8.8 | 3.2 | 5.4 | 7.6.8 | 3 | 7 | 3 | 7 | | | + | | {9.9.8 | | | | {5.6.5.7 | | | | | | | | | | + | | | | | | | | | {7.6.5.7 | | | | | | | + " | 631- 640 | 9.8 | 3 | 6 | 6.5 | 7 | 3.2 | 4 | {6.5.4.6 | 3 | 7 | 6 | 4 | | | + | | | | | | | | | {9.7.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 641- 650 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 7.9.6.7.9.8 | 3 | 8.6.8.7 | 8 | 2 |17 |13 | 1: 0.76 + 9 | 651- 660 | 8 | 3 | 6 | 5 | 7 | 2 | 4 | 7.6.7.6.8 | 3 | 8.6.8.8.4.7 | 8 | 2 | | | + " | 661- 670 | 9.9.8 | 3 | 7.6 | 5 | 7 | 3.2 | 5.4 | 7.6.7.6.8 | 4.3 | 5.6.8 | 3 | 7 |11 | 9 | 1: 0.82 + | | | | | | | | | | | | | | | | + 10 | 671- 680 | 9.8 | 3 | 5.4.5.6 | 5 | 6.4.8.6.7 | 3.2 | {3.5.3.2.3 | {7.6.5.6 | 3 | 5.4.3.7 | 3 | 7 | | | + | | | | | | | | {5.3.5.2.4 | {5.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 681- 690 | 8 | 4.3 | 6 | 5 | 7 | 2 | 5.4 | 8 | 3 | 6.8.7 | 7 | 3 |10 |10 | 1: 1.00 + 12 | 691- 700 | 7.8 | 3 | 5.6 | 5 | 7 | 3.2 | 3.4 | 7.7.7.7.8 | 4.2.2.3 | 8.7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 701- 710 | 9.8 | 4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | {7.6.5.4.3 | 3 | 8.7 | 2 | 8 | | | + | | | | | | | | | {2.1.4.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 711- 720 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | {7.6.5.4.3 | 3 | {6.5.4.3.6 | 4 | 6 | 9 |21 | 1: 2.33 + | | | | | | | | | {2.5.9.8 | | {5.4.3.8.7 | | | | | + | | | | | | | | | | | | | | | | + 13 | 721- 730 | 7.8 | 4.3 | 6 | 4.3.6.5 | 4.6.5.4.7 | 2 | 4 | {6.5.4.3 | 3 | {5.4.3.6 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | {2.1.8 | | {8.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {4.7.5.4 | | | | | | | + 14 | 731- 740 | 8 | 3 | 5.5.6 | 5 | {5.6.5.5 | 3.2 | 4 | {7.7.4.6 | 3 | 4.6.7 | 5 | 5 | | | + | | | | | | {8.8.7 | | | {5.6.8 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {5.4.5.5.4 | | {4.4.4.5.5 | | | | | + " | 741- 750 | 8 | 3 | 5.6 | 5 | {6.5.6.6 | 2 | 4 | {5.6.4.4.4 | 3 | {5.4.8.8.4 | 6 | 4 |11 | 9 | 1: 0.82 + | | | | | | {6.8.4.7 | | | {7.6.8 | | {5.5.6.4.7 | | | | | + | | | | | | | | | | | | | | | | + 15 | 751- 760 | 7.7.9.7.8 | 3 | 6 | 5 | 6.6.7 | 2 | 4 | 6.6.8 | 3 | {6.6.6.8 | 6 | 4 | | | + | | | | | | | | | | | {5.6.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | | | {5.4.6.6.5 | | | | | + " | 761- 770 | 8 | 3 | 5.6 | 5 | 6.6.6.6.7 | 2 | 3.4 | 5.4.7.8 | 3 | {5.3.5.8.5 | 5 | 5 |11 | 9 | 1: 0.82 + | | | | | | | | | | | {5.5.7 | | | | | + | | | | | | | | | {4.6.7.6.9 | | | | | | | + 16 | 771- 780 | 7.7.7.8 | 3 | 6 | 4.5 | 5.7 | 2 | 3.4 | {7.7.5.5 | 3 | (5.6.8.5 | 4 | 6 | | | + | | | | | | | | | {6.6.6.8 | | {3.7 | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {6.6.7.2 | | | | | | | + " | 781- 790 | 7.8 | 3 | {4.5.4.3 | {4.6.4.4 | {4.4.6.8 | 2 | 3.4 | {3.4.4.4 | 3 | 6.7 | 3 | 7 | 7 |13 | 1: 1.86 + | | | | {2.6 | {1.4.3.5 | {5.7 | | | {9.9.8 | | | | | | | + | | | | | | | | | | | | | | | | + 17 | 791- 800 | 7.8 | 2.3 | 6 | {4.4.4.3.6 | 4.8.4.6.7 | 2 | 4 | {5.7.6.6.1 | 3 | 5.7 | 4 | 6 | | | + | | | | | {2.4.2.5 | | | | {7.4.4.8 | | | | | | | + | | | {2.4.4.4.2 | | | | | | | | | | | | | + " | 801- 810 | 7.8 | {4.2.4.1.4 | 5.7.6 | 5 | 5.7 | 2 | 3.5.5.4 | 6.8 | {2.4.4.2 | 6.8.7 | 2 | 8 | 6 |14 | 1: 2.33 + | | | {2.4.3 | | | | | | | {4.2.4 3 | | | | | | + | | | | | | | | | | | | | | | | + 19 | 811- 820 | 7.9.7.8 | 2.4.2.4.3 | 5.7.6 | 3.6.4.6.5 | 7 | 2 | 3.5.4 | 6.8 | 4.4.3 | 6.8.7 | 2 | 8 | | | + " | 821- 830 | 7.8 | 2.4.4.3 | 6 | 4.6.6.6.5 | 6.8.7 | 2 | 3.5.5.5.4 | 6.8 | 2.4.3 | 6.5.7 | 2 | 8 | | | + " | 831- 840 | 7.9.8 | 2.4.4.2.4.3 | 7.6 | 5 | 7 | 2 | 4 | 7.6.4.6.8 | 2.4.3 | 6.8.7 | 4 | 6 | 8 |22 | 1: 2.75 + 20 | 841- 850 | 7.8 | 3 | 5.7.6 | 4.6.5 | 6.8.7 | 2 | 3.5.4 | 3.5.8 | 2.4.3 | 6.8.6.8.7 | 2 | 8 | | | + " | 851- 860 | 8 | 2.4.3 | 6 | 3.6.5 | 5.7 | 2 | 2.5.4 | 4.7.8 | 2.4.3 | 4.4.6.7 | 3 | 7 | | | + " | 861- 870 | 7.8 | 2.4.3 | 6 | 5 | 7 | 2 | 2.4 | 6.8 | 2.4.3 | 4.7 | 4 | 6 | 9 |21 | 1: 2.33 + 21 | 871- 880 | 7.9.8 | 2.4.3 | 5.7.6 | {4.6.4.6 | 4.6.7 | 2 | 3.5.3.5.4 | 5.7.8 | 2.4.3 | 5.7 | 1 | 9 | | | + | | | | | {3.2.4.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 881- 890 | 7.8 | 2.4.2.3 | 3.5.7.6 | 3.4.6.4.6.5 | 4.6.5.6.7 | 2 | 4 | 6.8 | 3 | 4.6.5.7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 891- 900 | 7.8 | 2.4.3 | 5.7.6 | 4.5 | 5.7 | 3.3.3.2 | 4 | {4.6.5.7.6 | 2.4.3 | 5.7 | 1 | 9 | 5 |25 | 1: 5.00 + | | | | | | | | | {4.2.4.8 | | | | | | | + | | | | | | | | | | | | | | | | + 22 | 901- 910 | 7.8 | 2.4.3 | 5.7.6 | 4.6.5 | 6.8.7 | 2 | 2.5.4 | 5.6.8 | 2.3 | 6.7 | 1 | 9 | | | + " | 911- 920 | 7.8 | 2.3 | 5.6 | 4.5 | 5.7 | 2 | 3.4 | 4.6.8 | 2.3 | 5.6.7 | 1 | 9 | 2 |18 | 1: 9.00 + | | | | | | | | | | | | | | | | + 23 | 921- 930 | 7.8 | 2.3 | {3.2.4.4 | 5 | 4.6.5.6.7 | 2 | 3.2.4 | 5.4.6.8 | 2.3 | {4.5.4.3.5 | 2 | 8 | | | + | | | | {5.6 | | | | | | | {6.5.6.7 | | | | | + | | | | | | | | | | | | | | | | + 23 | 931- 940 | 7.9.7.8 | 3 | 5.4.6 | 5 | 5.7 | 2 | 4 | 6.7.8 | 3 | 6.8.7 | 5 | 5 | | | + " | 941- 950 | 7.8 | 3 | 5.6 | 4.6.5 | 7 | 2 | 3.5.4 | 5.6.8 | 2.3 | 6.7 | 3 | 7 |10 |20 | 1: 2.00 + | | | | | | | | | | | | | | | | + 24 | 951- 960 | 7.8 | 2.3 | {2.7.7.4 | 4.6.5 | 5.7 | 2 | 4 | 4.6.8 | 3 | 6.8.7 | 3 | 7 | | | + | | | | {5.7.4.6 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 961- 970 | 7.9.7.8 | 3 | 6 | 5 | (6.8.6.8 | 2 | 5.5.3.4 | 7.8 | 3 | 7 | 6 | 4 | 9 |11 | 1: 1.22 + | | | | | | {6.7 | | | | | | | | | | + | | | | | {4.2.6.4 | | | | | | | | | | | + 26 | 971- 980 | 7.9.7.8 | 3 | 6 | {6.4.6.4 | 7 | 2 | 4 | 6.8 | 3 | 6.8.7 | 6 | 4 | | | + | | | | | {6.1.5 | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 981- 990 | 7.9.7.8 | 3 | 6 | 5 | 7 | 2 | 4 | 7.6.8 | 3 | 6.8.7 | 7 | 3 | | | + | 991-1000 | 7.8 | 3 | 6 | 5 | 6.8.5.7 | 2 | 4 | 6.8 | 4.2.3 | 6.5.7 | 5 | 5 |18 |12 | 1: 0.67 +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + In |trials 1001| to 1100 the | right door |was indicated | by being |raised before | the choice | was made. | | | | | | | | +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + 30 | 1101-1110 | 8 | 4.3 | 7.6 | 6.6.5 | 7 | 2 | 5.4 | {7.7.7.7.7 | 3 | 6.6.7 | 4 | 6 | 4 | 6 | 1: 1.50 + | | | | | | | | | {7.6.6.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + | | | | | | | | | {7.7.6.7 | | | | | | | + 31 | 1111-1120 | 7.7.8 | 3 | 7.6 | 5 | 6.7 | 3.3.2 | 4 | {7.6.6.7 | 4.4.4.3 | 7 | 4 | 6 | | | + | | | | | | | | | {6.6.8* | | | | | | | + | | | | | | | | | | | | | | | | + " | 1121-1130 | 8 | 4.3 | 6 | 6.5 | 8.7 | 3.2 | 5.4 | 7.8 | 3 | 7 | 4 | 6 | 8 |12 | 1: 1.50 + August | | | | | | | | | | | | | | | | + 2 | 1131-1140 | 8 | 4.4.3 | 6 | 5 | 7 | 3.3.3.2 | 4 | 7.8 | 4.3 | 7 | 6 | 4 | | | + " | 1141-1150 | 7.8 | 4.4.3 | 7.6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 4.3 | 7 | 3 | 7 | 9 |11 | 1: 1.22 + 3 | 1151-1160 | 7.9.8 | 4.3 | 7.6 | 5 | 6.7 | 2 | 5.4 | 7.6.7.8 | 4.3 | 6.7 | 2 | 8 | | | + " | 1161-1170 | 8 | 4.3 | 6 | 5 | 7 | 2 | 5.4 | 7.8 | 4.3 | 7 | 6 | 4 | 8 |12 | 1: 1.50 + 4 | 1171-1180 | 8 | 4.3 | 6 | 6.5 | 6.7 | 3.2 | 5.4 | 7.8 | 4.3 | 6.5.6.7 | 2 | 8 | | | + " | 1181-1190 | 8 | 3 | 6 | 5 | 7 | 3.3.2 | 4 | 7.8 | 3 | 7 | 8 | 2 |10 |10 | 1: 1.00 + 5 | 1191-1200 | 7.8 | 4.4.3 | 6 | 5 | 6.7 | 3.3.3.2 | 4 | 6.7.8 | 3 | 7 | 5 | 5 | | | + | 1201-1210 | 8 | 4.3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 7.8 | 3 | 7 | 5 | 5 | | | + " | 1211-1220 | 7.8 | 3 | 7.6.5 | 5 | 7 | 2 | 4 | 7.7.6.7.8 | 3 | 7 | 7 | 3 |17 |13 | 1: 0.76 + | | | | | | | | | | | | | | | | + 6 | 1221-1230 | 8 | 3 | 6 | 5 | {6.5.6.6 | 2 | 4 | {5.6.5.7 | 3 | 6.8.6.7 | 7 | 3 | | | + | | | | | | {5.6.5.7 | | | {9.7.8 | | | | | | | + | | | | | | | | | | | | | | | | + " | 1231-1240 | 7.8 | 3 | 6 | 4.5 | 7 | 2 | 4 | 6.7.8 | 3 | 6.7 | 6 | 4 |13 | 7 | 1: 0.54 + 7 | 1241-1250 | 7.8 | 3 | 6 | 5 | 7 | 2 | 4 | 8 | 3 | 8.7 | 8 | 2 | | | + " | 1251-1260 | 8 | 3 | 6 | 6.5 | 7 | 3.2 | 5.4 | 8 | 3 | 7 | 7 | 3 | | | + " | 1261-1270 | 8 | 3 | 6 | 5 | 7 | 3.2 | 5.3.4 | 8 | 3 | 7 | 8 | 2 |23 | 7 | 1: 0.30 + 9 | 1271-1280 | 8 | 3 | 6 | 5 | 7 | 2 | 5.4 | 9.7.8 | 3 | 7 | 8 | 2 | | | + " | 1281-1290 | 8 | 3 | 6 | 5 | 7 | 3.2 | 4 | 7.8 | 3 | 7 | 8 | 2 |16 | 4 | 1: 0.25 + 10 | 1291-1300 | 7.8 | 3 | 7.6 | 5 | 6.7 | 3.2 | 4 | 6.7.8 | 3 | 7 | 5 | 5 | | | + " | 1301-1310 | 7.8 | 4.3 | 5.6 | 4.5 | 6.7 | 2 | 4 | 6.8 | 3 | 6.8.7 | 3 | 7 | | | + " | 1311-1320 | 7.8 | 3 | 6 | 5 | 5.7 | 2 | 4 | 5.7.8 | 3 | 4.6.8.7 | 6 | 4 |14 |16 | 1: 1.14 + 11 | 1321-1330 | 7.8 | 3 | 6 | 5 | 6.7 | 3.2 | 4 | 4.6.7.8 | 2.3 | 5.7 | 4 | 6 | | | + " | 1331-1340 | 7.8 | 3 | 6 | 4.5 | 6.7 | 2 | 4 | 6.7.8 | 3 | 7 | 6 | 4 |10 |10 | 1: 1.00 + 12 | 1341-1350 | 9.8 | 3 | 6 | 5 | 6.7 | 2 | 4 | 6.7.8 | 3 | 6.7 | 6 | 4 | | | + " | 1351-1360 | 7.8 | 3 | 6 | 5 | 6.7 | 2 | 4 | 7.8 | 3 | 6.7 | 6 | 4 |12 | 8 | 1: 0.67 + 19 | 1361-1370 | 7.8 | 3 | 6 | 5 | 6.7 | 2 | 4 | 6.7.8 | 3 | 6.7 | 6 | 4 | | | + | 1371-1380 | 9.8 | 3 | 6 | 5 | 7 | 3.2 | 4 | 7.9.8 | 3 | 6.8.7 | 6 | 4 |12 | 8 | 1: 0.67 +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + +[Footnote *: Aided by experimenter.] + + + +After two hundred and fifty trials on problem 2 had been given Julius, +it seemed desirable to introduce a radical change in method in order to +stimulate him to maximal effort. It was therefore decided to force him +to make a round trip through the apparatus in connection with each +choice, and to let this forced labor serve, in the place of confinement, +as punishment for mistakes. This new method yielded peculiar and +characteristic results. They differ from those previously obtained +largely because of the orang utan's remarkably strong tendency to +reenter the box through which he had just passed. This occurred so +persistently, as may be seen in table 9 (June 17, second series, June +18, etc.), that a further modification of method was introduced in that +after the same wrong box had been entered five times in succession, the +experimenter on the next choice of the box confined the animal for a +stated interval, say sixty seconds, in it, and then allowed it to escape +by way of the exit door and choose repeatedly until it finally located +the right box. Were it not for this particular feature of the method, +the number of choices recorded after June 17 would unquestionably be +very much greater than the table indicates. + +The new method proved a severe test of the orang utan's patience and +perseverance, for he had to work much harder than formerly for his +reward, and often became much fatigued before completing the regular +series of ten trials. Early in the use of this method, he developed the +habit of rolling around from exit door to starting point by a series of +somersaults. When especially discouraged he would often bump his head +against the floor so hard that I could hear the dull thud. As has been +noted, I found it desirable to vary the procedure repeatedly. It proved +especially interesting to give one series per day with the round trip as +punishment and another series with confinement as punishment. + +Day after day, as the experiment progressed, slight or great +fluctuations of the ratios of right to wrong choices appeared, but +without consistent improvement. There was, to be sure, as the last +column of table 9 shows, a radical improvement during the first six +hundred and fifty trials, for the number of right choices per series +increased from 0 to 8. But, as the observations were continued from day +to day, it became more and more evident that the animal was merely +passing from tendency to tendency--method to method--mixing tendencies, +and occasionally developing new ones, without approach to the solution +of the problem. This fact would have led me to discontinue the work much +earlier than I actually did had it not been for the peculiarity of the +results obtained with problem 1. It seemed not improbable that at any +time Julius might succeed in perfectly solving this problem over night +precisely as he had solved the first problem. + +A curiously interesting bit of behavior appeared for the first time on +June 29. Julius had gone to the first box at the right end of the group, +and instead of entering, he had wheeled around toward his right, and +turning a complete circle, faced the right box, which he promptly +entered. Subsequently, the tendency developed and the method was used +with increasing frequency. On June 30, it appeared in the first series, +four times, in the second series, six times; on July 1, in the first +series, three times, and in the second series, four times; on July 2, in +the first series, five times, and in the second series, nine times. It +was indeed only by accident that the animal failed to fulfill the +technical requirement for perfect solution of the problem in this +series. Yet, had he done so, his subsequent trials would doubtless have +revealed the lack of any other idea than that of turning completely +around before entering a box. + +This odd bit of behavior proved peculiarly interesting and significant +in that the tendency to turn became dissociated from the position (in +front of the first box at the right end of the group) in connection with +which it originally developed. After a few days, Julius would enter the +reaction-chamber and instead of proceeding directly to the right end of +the group, would stop suddenly wherever he happened to be, turn toward +his right in a complete circle, and hasten into the box nearest to him +which, as often as not, proved to be the wrong one. Thus the idea of +turning completely about, which had it continued its association with +the idea of facing the first box at the right, would have yielded +success, instead became useless because of its dissociation. That the +orang utan is capable of using free ideas seems clear enough in the +light of this behavior. That he proved incapable of getting the idea of +second from the right end is as clearly shown by the detailed results of +table 9,--the fruits of weeks of experimenting. + +Certain other interesting tricks developed in Julius's behavior. Thus, +on July 5, there appeared the tendency to move as though about to enter +the right box (feint), then to stop suddenly and promptly enter another +box, which was, of course, a wrong one. The reason for the development +of this tendency could not be discovered, but in connection with it, +there appeared another tendency which possibly can be explained. Julius +took to backing into the chosen box so that he could face the +experimenter. He would then, after a period of hesitation, come out and +promptly enter one of the other boxes. This tendency was apparently due +to the fact that during one or two series the experimenter growled at +the orang utan every time he made a mistake. The growl startled him and +caused him to look around. He evidently felt the need of keeping his +eyes on the experimenter,--Hence the backing into the open box. The +tendency disappeared shortly after the experimenter gave up the use of +the growl as a method of punishing the animal for what were suspected to +be careless choices. + +Curiously enough, it was not until July 10 that direct choice of the +right box was made at all frequently. Previously, selection of it had +been made almost invariably after approach to other boxes. But in the +second series for July 10 there was an extraordinary improvement in +method. This developed in the presence of two visitors, and it is +therefore all the more surprising. The choices were made not only +directly, but with decision and evident certainty that was quite at +variance with the previous behavior of the animal. + +All the while through variation of methods, I was seeking to discover +the best means of holding the orang utan to his maximum effort and care +in attempting to select the right box. One day it would seem as though +forcing him to make round trips with rewards only for correct first +choices proved most satisfactory, and the next it might seem equally +clear that punishment by confinement for thirty seconds or sixty +seconds, with reward for correct choice in every trial, yielded better +results. In the end I had to admit that no best method had been +demonstrated and that I had failed to develop conditions which served to +compel the animal's attention to the problem and to lead him to work +without discouragement. There were, it is true, days on which it seemed +practically certain that the problem would be solved, but as it turned +out, Julius never succeeded in choosing correctly--throughout a series +of ten trials. + +As a last resort, in order to make perfectly sure that the orang utan +was doing his best, I decided to introduce corporal punishment in a mild +form. For this purpose, I placed my assistant in charge of the apparatus +and the series of trials, and stationed myself in one corner of the +reaction-chamber with a whip in my hand. Whenever Julius entered a wrong +box, I approached him with the whip and struck at him, being careful not +to injure him and rarely striking him at all, for the threat was more +effective than a blow. He was extremely afraid of the whip and would +begin to whine and attempt to get out of the way as soon as he saw it. + +This method was introduced on August 10, but no improvement resulted, +and in the end there was no reason to consider it more satisfactory than +the other procedures. I am now wholly convinced that Julius did his best +to choose correctly in the majority of the numerous series which were +given him in connection with problem 2. + +From trials 1001 to 1100, a radical departure from the previous methods +was introduced in that the right box was indicated to the animal by the +slight and momentary raising of its exit door. Of course no records of +the choices for this group of one hundred trials appear in table 9, for +the simple reason that the animal inevitably and immediately entered the +right box. It was thought that this method might serve to break up the +previously developed tendencies toward inadequate forms of response and +so encourage the animal that he would later solve the problem when given +opportunity to select the right box without aid from the experimenter. +But as a matter of fact, while the ratio of right to wrong first choices +was 1 to .67 in the series preceding this change of method, it was 1 to +1.50 in the first series following its use. There is no satisfactory +evidence that Julius profited by this experience, though as a matter of +fact he did succeed in making his best daily record, eight right to two +wrong choices, on August 4, after 1190 trials. + +The curve of learning for this problem has been plotted and is presented +in figure 19. It is of course incomplete and it is offered only to +indicate the extreme irregularity in performance. + + +_Problem 1a. First at the Right End_ + +It was decided on August 19 that the further continuation of the work of +Julius on problem 2 was not worth while. He had become much discouraged, +and although willing to work for food, gave no indications whatever of +improvement and seemed to have exhausted his methods. It seemed wise +instead of giving up work with him in the multiple-choice method to +return to a form of problem 1. We may designate it as problem 1a. The +right box is definable as the first at the right end of the series +instead of the first at the left end as in the original problem 1. It +was thought possible that Julius might quickly solve this problem by a +process similar to that used for problem 1. + +Work was begun on problem 1a, August 20, and for six successive days two +series of trials per day were given, the settings for which as well as +the resulting choices are given in table 10. Most notable in these +results is the large number of cases in which Julius chose first the +second box from the right end of the series, or in other words that box +which had been the right one in problem 2. Contrary to expectation, he +showed no inclination to abandon this tendency to choose the second from +the right end, and the ratio of right to wrong choices changed in the +direction opposite from expectation, beginning with 1 to 4 and ending on +the sixth day with 0 to 20. + +It was obviously useless to continue the experiment further since Julius +had given up his attempts to locate the right box in the first choice +and was apparently satisfied to discover it by a process of trial and +error. He had, it would seem, satisfied himself that the problem was +insoluble. These results obtained in problem 1a constitute a most +interesting comment on the effects of problem 2 on the orang utan. +Behavior similar to that which he developed well might have been +obtained from a child of three to four years placed in a like situation +and forced to strive, day after day, to solve a problem beyond its +ideational capacity. + +In many respects the most interesting and to the experimenter the most +surprising result of this long series of observations with Julius was +the lack of consistent improvement. It seemed almost incredible that he +should continue, day after day, to make incorrect choices in a +particular setting while choosing correctly in some other setting which +from the standpoint of the experimenter was not more difficult. + + + +TABLE 10 + +Results for Orang utan in problem 1a + + +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + | No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio + Date | of | | | | | | | | | | 1.2.3.4 | R | W | R | W | of + | trials | 5.63 | 1.2.3.4 | 6.7.8.9 | 2.3.4.5 | 3.4.5.6.7 | 1.2.3 | 5.6.7.8 | 1.2 | 2.3.4.5.6 | 5.6.7 | | | | | R to W +--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+-------- + | | | | | | | | | | | | | | | | + August | | | | | | | | | | | | | | | | + 20 | 1- 10 | 6 | 3.4 | 6.7.8.9 | 4.5 | 6.7 | 3 | 7.8 | 2 | 5.5.6 | 6.7 | 3 | 7 | | | + | | | | | | | | | | | | | | | | + " | 11- 20 | 5.6 | 3.4 | {7.8.7.8 | 4.5 | 6.7 | 2.3 | {7.6.7.7 | 2 | 5.6 | 6.7 | 1 | 9 | 4 |16 | 1: 4.00 + | | | | {8.7.8.9 | | | | {6.7.7.8 | | | | | | | | + | | | | | | | | | | | | | | | | + 21 | 21- 30 | 5.6 | 3.4 | {7.8.7.6 | 4.5 | 6.7 | 2.3 | 7.8 | 2 | 5.6 | 5.7 | 1 | 9 | | | + | | | | {8.7.9 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + " | 31- 40 | 5.6 | 3.4 | 7.7.6.8.9 | 4.5 | 6.7 | 3 | 6.7.8 | 2 | 6 | 6.7 | 3 | 7 | 4 |16 | 1: 4.00 + 23 | 41- 50 | 5.6 | 3.4 | 7.8.9 | 4.5 | 6.7 | 2.3 | 6.7.8 | 2 | 5.6 | 5.6.7 | 1 | 9 | | | + " | 51- 60 | 5.6 | 3.4 | 7.8.9 | 4.5 | 6.7 | 2.3 | 6.8 | 2 | 5.6 | 6.7 | 1 | 9 | 2 |18 | 1: 9.00 + 24 | 61- 70 | 5.6 | 3.4 | 6.8.9 | 4.5 | 5.7 | 2.3 | 6.7.8 | 1.2 | 5.6 | 6.7 | 0 |10 | | | + " | 71- 80 | 5.6 | 3.4 | 6.7.8.9 | 4.5 | 5.7 | 2.3 | 5.7.8 | 2 | 5.6 | 6.7 | 1 | 9 | 1 |19 | 1:19.00 + 25 | 81- 90 | 5.6 | 3.4 | 6.7.8.9 | 5 | 5.6.7 | 2.3 | 7.8 | 1.2 | 5.6 | 4.5.6.7 | 1 | 9 | | | + " | 91-100 | 5.6 | 3.4 | 6.7.8.9 | 3.4.5 | 6.6.7 | 2.3 | 6.7.8 | 1.2 | 5.6 | 6.7 | 0 |10 | 1 |19 | 1:19.00 + | | | | | | | | | | | | | | | | + 26 | 101-110 | 5.6 | 3.4 | {6.7.8.8 | 3.5 | 5.6.7 | 2.3 | 5.6.7.6.7.8 | 1.2 | 5.6 | 6.7 | 0 |10 | | | + | | | | {6.7.6.9 | | | | | | | | | | | | + | | | | | | | | | | | | | | | | + | | | | {6.7.8.8 | | | | | | | | | | | | + " | 111-120 | 5.6 | 2.3.4 | {6.7.8.7 | 3.4.5 | 5.6.7 | 2.3 | 7.8 | 1.2 | 5.6 | 4.5.6.7 | 0 |10 | 0 |20 | 0:20.00 + | | | | {6.7.9* | | | | | | | | | | | | + | | | | | | | | | | | | | | | | +========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+======== + + +[Footnote *: Aided by experimenter.] + + + +The evidence suggests that in this young orang utan ideational learning +tended to replace the simpler mode of problem solution by trial and +error. Seemingly incapable of solving his problems by the lower grade +process, he strove persistently, and often vainly, to gain insight. He +used ideas ineffectively. Animals far lower in intelligence (e.g., the +pig), surpass him in ability to solve these relational problems because +they use the method of elimination by trial consistently and +effectively. Julius, in these experiments, made a poor showing because +his substitute for trial and error is only slightly developed. Would he +have succeeded better with the same problems if mentally mature? + +There are many important features of the results which, for lack of +space, have not been indicated or discussed. They can be developed from +later comparative studies of the data, for in the tables appear all of +the essential facts of response apart from those mentioned in the text. + + + +IV + +RESULTS OF SUPPLEMENTARY TESTS OF IDEATIONAL BEHAVIOR + + +1. Julius, _Pongo pygmaeus_ + + +_Box Stacking Experiment_ + +In addition to the multiple-choice experiments which have been described +in detail in the previous section, it was possible to conduct certain +less systematic tests of ideational behavior in the monkeys and the +orang utan. From the technical standpoint these tests were relatively +unsatisfactory because only inexactly describable. But their results are +in many respects more interesting, if not also more important, in the +light which they throw on ideation than are those previously presented. +First, in order of time, comes a test which may be designated as the box +stacking experiment. The method will now be described in connection with +an account of the behavior of Julius as contrasted with that of a child +of three years and four months of age. + +In the large central cage labelled Z, figure 12, which was twenty-four +feet long, ten feet wide, and ten to twelve feet deep, the following +situation was arranged. From the center of the wire covering of the +cage, a banana was suspended on a string so that it was approximately +six feet from the floor, five feet from either side of the cage, and +twelve feet from either end. From all approaches it was far beyond the +reach of Julius, since it was impossible for him to climb along the wire +roof and thus reach the string. Two boxes were placed on the floor of +the cage several feet from the point directly under the banana. The one +of these boxes was heavy and irregular in shape, as is shown in figures +21, 23 and 24 of plate V. Its greatest height was twenty-one inches; its +least height, eighteen inches; its other dimensions, twelve and sixteen +inches respectively. The smaller and lighter box measured twenty-two by +twelve by ten inches. According to the experimenter's calculations, the +only way in which Julius could obtain the banana was by placing the +smaller box upon the larger and then climbing upon them. + +At 10 a.m. on March 5, Julius was admitted to the large cage, and the +banana was pointed out to him by the experimenter. He immediately set +about trying to get it, and worked diligently during the whole of the +period of observation, which, because of the unfinished condition of +some of the cages, was limited to slightly over ten minutes. Within this +period he made upward of a dozen fairly well directed attempts to obtain +the food. Chief among them were three attempts to reach the banana from +different positions on the left wall of the cage (as the experimenter +faced the laboratory); two attempts to reach it from different positions +on the right wall; two from the large box in positions nearly under the +banana; two from the large box with the aid of the experimenter's hand; +and one from the distant end of the cage(?). There occurred, also, less +definite and easily describable efforts to get at the reward. + +On account of the unfinished condition of the cages, the experimenter +had to remain in the large cage with Julius during the test. This +interfered with the experiment because the animal tended both to try to +escape and to get the experimenter to help him with his task. +Particularly interesting is the latter sort of behavior. After the orang +utan had made two or three futile attempts to obtain the food he came to +the experimenter, who was standing in one corner of the cage, took him +by the hand, and led him to a point directly under the banana. He then +looked up toward the banana, grasped the experimenter's arm, raised it, +and then tried to pull himself up. He was not allowed to get the food by +climbing up on the experimenter. A few minutes later, he again led the +experimenter toward the banana, but receiving discouragement in this +activity, he proceeded to devote himself to other methods. + +Apart from the distractions which have been mentioned above, Julius's +attention to the food was surprisingly constant. Whatever his position +with respect to it, he seemed not for an instant to lose his motive, and +to whatever part of the cage he went and whatever he did during the +interval of observation was evidently guided by the strong desire to +obtain the banana. Frequently he would look directly at it for a few +seconds and then try some new method of reaching it. His gaze was +deliberate and in the handling of the boxes he accurately gauged +distances. Several times he succeeded in placing the larger box almost +directly under the banana, and repeatedly he located that portion of the +side wall from which he could most nearly reach the coveted prize. + + + +EXPLANATION OF PLATE V + +Orang utan, Julius, obtaining banana by piling boxes +or by using pole + +FIGURE 21.--Julius in act of setting larger box on end. + +FIGURE 22.--Placing smaller box on larger. + +FIGURE 23.--Balancing on larger box preparatory to reaching for banana. + +FIGURE 24.--Balancing and reaching to the utmost. + +FIGURE 25.--Standing on three boxes (after stacking them) and +reaching for reward. + +FIGURE 26.--Lifting smaller box up toward banana. + +FIGURE 27.--The act of stacking the boxes. + +FIGURE 28.--Sequel to figure 27. + +FIGURE 29.--Box and pole experiment. Pushing the second pole +into the box. + +FIGURE 30.--Pushing pole into box. + +FIGURE 31.--Enjoying the reward of success. + + + +From my notes I quote the following comment on the results of the +initial experiment: "Despite all that has been written concerning the +intelligent behavior of the orang utan, I was amazed by Julius's +behavior this morning, for it was far more deliberate and apparently +reflective as well as more persistently directed toward the goal than I +had anticipated. I had looked for sporadic attempts to obtain the +banana, with speedy discouragement and such fluctuations of attention as +would be exhibited by a child of two to four years. But in less than ten +minutes Julius made at least ten obvious and well directed attempts to +reach the food. There were also wanderings, efforts to obtain aid from +the experimenter, and varied attempts to escape from the cage." + +Before proceeding further with the description of the behavior of Julius +in the box stacking test, I shall describe for contrast the behavior of +a boy three years four months of age when confronted with a situation +practically identical with that which the ape was given an opportunity +to meet. For the child, the banana was suspended, as previously +described, from the roof of the cage. The same two boxes were placed on +the floor at considerable distances from the banana, and in addition, a +light stick, about six feet long, and a piece of board, the latter by +accident, were on the floor. The child was asked to get the banana for +Julius, and he eagerly and confidently volunteered to do so. + +His behavior may best be described by enumeration of the several +attempts made. They include (1) placing the larger box nearly under the +banana and reaching from it. (2) Standing of the larger box on end with +resulting failure because the child could not stand on the sloping edges +of the top of the box. (3) The larger box was turned on its side and the +lighter box drawn up opposite it and stood on end. The child then +mounted the larger box and from it stepped to the top of the smaller. +But the boxes had not been placed beneath the banana, and when the child +reached for it, he found himself several feet away from his prize. (4) +The boxes were moved to a position nearly under the banana and another +futile attempt was made to reach it without placing the smaller box on +top of the larger one, the only position from which the child could +readily obtain it. (5) The piece of board was placed on top of the +larger box and from this height the child again reached upward. (6) The +six-foot stick was taken up and an attempt was made to strike the banana +and thus dislodge it, but it was too securely fastened to be obtained +thus. (7) Attention shifted to other things, and the child played for a +time with the board. Reminded of the banana by the experimenter, he +again tried method (3). (8) He again used the stick on the banana. (9) +The effort to knock the prize to the floor having failed, he became +discouraged and said that he must go home. (10) When told that Julius +was very hungry and wanted the banana, he repeated efforts similar to +those described in (3) and (6). + +Up to this time the observations had covered a period of twenty minutes. +The child was now taken from the cage and allowed to play about for +fifteen minutes. Asked then whether he would go back and try to get the +banana, he replied, "No, 'cause I don't want to get it," thus indicating +his discouragement with the situation. When taken into the cage, he, +nevertheless, made the additional attempts indicated below: (11) Use of +one of the boxes. (12) He remarked, "Now I know, I'll get it," and after +so saying, repeated (3). (13) Failing, he turned to me and said, "I +could get it if I was on your head," but he did not, as Julius had done, +lead me to the proper place and try to reach the banana by climbing up +or by urging me to lift him. (14) Later, he played in the boxes, +apparently forgetful of his task. Finally he remarked: "I'll get the +banana," but he made no attempt to do so, and instead, watched the +monkeys intently. Thereafter, he showed no further interest in the +solution of the problem, and the experiment, after a total period of +fifty-five minutes, was discontinued. + +Comparison of the behavior of the ape with that of the child indicates a +greater variety of ideas for the latter. Julius gauged his distances +much more accurately than the child, attended more steadily, and worked +more persistently to obtain the reward, but he did not so nearly +approach the idea of stacking the boxes as did the child, for the +latter, in placing the board on one of the boxes, exhibited in +ineffective form the idea which should have yielded the solution of the +problem. + +The child was given no further opportunity to work at the problem, +whereas Julius, as I shall now describe, continued his efforts on +subsequent days under somewhat different conditions. On Wednesday, March +10, the banana was suspended as formerly, and three boxes, all of them +small and light enough to be readily handled by the ape, were placed in +distant parts of the cage. The six-foot stick which had been present in +the test with the child, but not in the first test with Julius, was also +placed in the cage. + +Julius was allowed to work for about an hour. As formerly, he was +sufficiently hungry to be eager to get the food and evidently tried all +of the possible ways which occurred to him. Chief among these were (1) +the use of the various boxes separately or in pairs in very varied +positions but never with one upon another,--the only way in which the +banana could be reached; (2) climbing to various points on the sides of +the cage, with infrequent attempts to reach the banana. Usually his eyes +saved him the vain effort. + +Unlike the child, Julius paid little attention to the six-foot stick. +Two or three times he took it up and seemingly reached for the banana, +but in no case did he try persistently to strike it and knock it from +the string. It is but fair, however, to remark that such an act is very +difficult for the young orang utan, as compared with the child, because +of the weakness of the legs and the awkwardness of striking from a +sitting posture. As previously, the steadiness of attention and the +persistence of effort toward the end in view were most surprising. At +one time Julius walked to the end of the cage and there happened to see +one of the monkeys eating. He watched intently a few seconds and then +hastened back to the banana as if his task had been suggested to him by +the sight of the feeding animal. Most interesting and significant in +this behavior was the suddenness with which he would turn to a new +method. It often looked precisely as though a new idea had come to him, +and he was all eagerness to try it out. + +On March 11, Julius was given another opportunity to obtain the banana +by the use of the three boxes. Although he used them together he made no +effort to place one upon another. Certain of his methods are shown in +plate V, especially by figures 21, 23 and 24. + +This experiment was continued on April 2 under yet different conditions, +for this time only two boxes were placed in the cage, the one of them +the heavy, irregularly-shaped box and the other the smaller, lighter one +originally used. On the end of the heavier box had been nailed a two by +two inch wooden block in order to increase the difficulty in using this +box alone. As previously, Julius made varied attempts to obtain the +banana, but on the whole his interest and attention seemed somewhat +weaker than previously and there were indications of discouragement +because of repeated failures. + +He handled the boxes conspicuously well, and it seemed at times that he +would certainly succeed in placing the one upon the other and in +reaching the food. + +After one series of attempts from the sides of the cage and from the +large box, he deliberately turned away from the box and neatly executed +a somersault on the floor of the cage, as much as to say, "I am +disgusted with the whole situation." Again, later on the same day, after +falling from the top of the larger box, which tilted over very easily, +he rolled himself into a ball, and childlike, played with his feet. An +additional evidence of his changed affective attitude toward his task, +especially in connection with definite failures, appeared in his rough +handling and biting of the boxes. When most impatient, he worked very +roughly. + +Julius was allowed to work for the reward from thirty to ninety minutes, +or, as a rule, until he had become completely discouraged on April 3, 5, +6, 7, 8, 9 and 13. His behavior was interesting and significant, but +nothing new appeared except that his willingness to work gradually +disappeared, and on April 13, although previously hungry, he made only a +single attempt to obtain the banana and then paid no further attention +to it. + +The prolonged and varied efforts to obtain the banana were due in a +measure at least to three accidental successes. Thus on April 2, 3 and +again on the 5th, by fortunate combinations of circumstances, he +succeeded in getting the banana, contrary to the intention of the +experimenter. + +Although active at first on April 6, he soon wearied of his task and +quit work. The same was true on April 7, and again on the 8th and 9th. +On these days, although hungry, he did not care to enter the large cage +and worked only a few minutes each day, seldom making more than two or +three half-hearted attempts to obtain the banana. His attitude toward +the task had changed completely, in that hopelessness had taken the +place of eager expectancy. By the 13th of April he had so nearly given +up voluntary efforts to solve the problem that it seemed worth while to +test his ability to get the idea by watching the experimenter. For this +purpose the following test of imitation was made. + +On the morning of April 14, having placed a banana in the usual +position, I took Julius into the large cage, dragged the two boxes to +the proper position beneath the banana, placed the smaller one upon the +larger one and then climbed up on them to show the ape that I could +reach the banana. I then stepped down and gave him a chance to climb on +the boxes. He did so immediately and obtained the food. + +Another piece of banana was supplied, the boxes were placed in distant +corners of the cage, and fifteen minutes were allowed Julius so to place +them that he could obtain his reward. He gave no indications of having +profited by my demonstration, but worked with the boxes singly, usually +with the larger one. On April 16, with the banana in position and the +two boxes also in the cage, Julius was admitted and allowed to work for +five minutes, but again without success. I then placed the boxes +properly for him and he immediately climbed up and got the banana. While +he was eating, the boxes were carried to distant corners of the cage and +another banana placed in position. Now thirty minutes were allowed him +for unaided work on the problem. As formerly, the larger box was used +repeatedly and attempts to reach from the side of the cage appeared, but +there was no tendency to try to use the two boxes together. He worked +fairly persistently, however, and showed clearly the stimulating and +encouraging effect of aid from the experimenter. Once more, on April 17, +Julius was taken into the cage and allowed to watch me place the boxes +in proper position. He then climbed up and obtained the desired food. +After the bait had been renewed and the boxes displaced, he immediately +tried to use the larger one, then he reached for the small one as though +to use both together. But the impulse died out and he turned again to +the larger box as usual, standing it on end, and persistently trying to +balance himself on it. Nothing else of special interest happened during +the interval of unaided effort. + +Similarly, I placed the boxes for the ape on April 19, allowed him to +get the banana and then gave him opportunity to try for himself after +the boxes had been displaced. This time he immediately reached for the +smaller box and moved it about a little, thus indicating a new +association. He next turned to the larger box and worked with it +persistently. Later, he once more worked with the smaller box in an +unusual manner. He repeatedly stood on it, but made no attempt to lift +it or to place it on the larger box. Clearly the usually neglected +smaller box had become associated with the satisfaction of obtaining the +banana. The same method was carried out on April 20. As I placed the +boxes in position beneath the banana, Julius watched with unusual +intentness, and when it came his turn to try to obtain the food by the +use of the boxes, he began at once to work with the smaller box, but as +on April 19, he soon abandoned it and turned to the other. While I was +making note of this particular feature of his behavior, he suddenly +seized the smaller box by two corners with his hands and by one edge +with his teeth, and after a few attempts placed it on top of the larger +box, climbed up, and obtained the banana. + +Because of bad weather on April 21, the next test was made on April 22, +with everything as usual. Unaided, the ape was given an opportunity to +obtain the coveted reward, while I stood ready to obtain records of his +behavior with my camera. He wasted no time, but piled the smaller box on +top of the larger one immediately, and obtained his reward. As soon as +opportunity was offered, he repeated the performance. The same thing +happened on April 23 and several succeeding dates. + +Julius had got the idea, and the only further improvement possible was +in skill in manipulating the boxes. + +One of the curious performances which appeared during the imitative +period is pictured in figure 26, plate V, where the ape is seen lifting +the smaller box into the air. This he did three or four times one day, +raising it toward the banana each time as though he expected thus to +obtain the reward. As he did not go up with the box (according to his +expectation?), he abandoned this method, and looking about, discovered +the larger box in a distant corner. Thereupon, he promptly pulled the +boxes to their proper position beneath the banana, stacked them, and +obtained his food. + +After considerable skill had been acquired in the placing of the boxes, +the one upon the other, the height of the banana above the floor was +increased so that three boxes were necessary. Figure 25 of plate V shows +him standing on three boxes and reaching upward, and figures 22, 27 and +28 show various modes of handling the boxes and of reaching from them. +He was not at all particular as to the stability of his perch, and often +mounted the boxes when it seemed to the experimenter inevitable that +they should topple over and precipitate him to the floor. Only once, +however, during the several days of experimentation did he thus fall. + +Obviously important is the evident change in the animal's attention on +April 20. He watched with a keenness of interest which betokened a +dawning idea. Before he had succeeded in stacking the boxes, I had +written in my note-book, "He seemed much interested today, in my placing +of the boxes." Interesting, and important also, is the ease and +efficiency with which he met the situation time after time, after this +first success. "Trial and error" had no obvious part in the development +of the really essential features of the behavior. The ape had the idea +and upon it depended for guidance. + +Except for the fact that Julius was immature, probably under five years +of age, it is likely that he would have stacked the boxes spontaneously +instead of by suggestion from the experimenter or imitatively. + +No unprejudiced psychologist would be likely to interpret the activities +of the orang utan in the box-stacking experiment as other than imaginal +or ideational. He went directly, and in the most business-like way from +point to point, from method to method, trying in turn and more or less +persistently or repeatedly, almost all of the possible ways of obtaining +the coveted food. The fact that he did not happen upon the only certain +road to success is surprising indeed in view of the many ineffective +methods which he used. It seemed almost as though he avoided the easy +method. + +It is especially important, in connection with these results, to point +out the risk of misinterpretation of observations on the anthropoid +apes. If they can imitate human activities as readily and effectively as +Julius did in this particular experiment, we can never be sure of the +spontaneity of their ideational behavior unless we definitely know that +they have had no opportunity to see human beings perform similar acts. + +Of all the methods of eliciting ideational or allied forms of behavior +used in my study of the monkeys and ape, none yielded such illuminating +results as the box stacking test, and although from the technical +standpoint, it has many shortcomings, as a means to qualitative results +it has proved invaluable. + + +_Other Methods of Obtaining the Reward_ + +Some weeks later, I tried to discover how Julius would obtain the much +desired banana when the boxes were absent. I placed in the large cage a +stick about six feet long and an old broom. When admitted, he looked +about for the boxes, but not seeing them, picked up the broom and +placing it with the splints down, beneath the banana, he tried to climb +it, but as it fell over with him, he abandoned this after a few trials, +went to his cage, and picking up some old bags which he used at night as +covers, he dragged them out and placed them on the floor beneath the +banana. He next put the broom upon them and tried to climb up. This +general type of behavior persisted for several minutes, everything +within reach being used as were the bags, as a means of raising him in +the desired direction. Finally, he placed his feet on the broom where +the handle joins the splints, seized the handle near the top with his +hands, drew himself up as far as possible, and then launched himself in +the air and tried to seize the banana. On the third attempt he +succeeded. + +Later, he was given a plain stick about five feet long. Figure 32 of +plate VI shows him using this to obtain the banana in the manner +described above. He would grasp it with one or both feet, usually one, +ten to fifteen inches from the floor of the cage, meanwhile holding with +his hands near the top of the stick. He would then, with all his +strength, draw himself up suddenly and jump toward the banana. Often he +came down rather hard on the cement floor, much to his disgust. + +Yet another method of obtaining the reward developed a day or two later. +A light red-wood stick about five feet long and an inch in its other +dimensions was the only object in the cage which could possibly be of +use in obtaining the banana. The aim of the experimenter was to discover +whether Julius would use this as a club. + +Previously, in connection with the use of the boxes, he had taken up the +same stick two or three times and reached for the banana with it, but in +no case had he struck at it or clearly tried to knock it from the +string, as did the child most readily and naturally. When provided with +this same stick, and it alone, as a means of obtaining the food, he hit +upon the following interesting method. Placing one end of the stick +between a wooden brace and the wire side of the cage, he climbed up to a +level with the banana as is shown in figure 33 of plate VI. Then holding +with one hand and one foot to a timber of the cage and to the stick with +his other foot, he swung outward as far as possible and reached the +banana with his free hand. Having once succeeded by the method, he used +it whenever given an opportunity. It was impossible for him to make the +reach without the use of the small stick, while with it he succeeded +fairly easily and regularly. + + +_Box and Pole Experiment_ + +Following the box stacking test, Julius was given an opportunity to +exhibit ideation in another type of experiment. This may be designated +the box and pole test. The conditions are describable thus. A strong +wooden box eighty-four inches long, by four inches wide, by four inches +deep, with open ends, was built with one side hinged. Hasps and padlocks +enabled the experimenter to lock this "lid" after food had been placed +in the center of the box. This box could be placed in the center of the +large cage and there fastened by means of cross bars. It is well shown +in position in figure 29, plate V. Two poles each eight feet long and +approximately one and a half inches in their other dimensions were the +only additional materials in the experiment. + +On May 1, Julius was allowed to see the experimenter place a half banana +in this box, close the lid, lock it in position, and securely fasten the +box by means of the cross bars. He was then given opportunity to try to +get the banana. The two poles lay on opposite sides of the box and near +the edges of the cage. Doctor Hamilton and the writer were in the cage +watching. Julius looked into the box through one end, and seeing the +banana, reached for it. He could not obtain it in this way, so he began +to bite at the box and to pull at it with all his strength. During the +fifteen minutes allowed him, he worked at the box in a great variety of +ways, fooling with the locks which had been attached to the hasps as +well as with the cross bars and continually reaching in at the one or +the other end. He was somewhat distracted by the presence of the two +observers and attended rather unsatisfactorily to the task in hand. Not +once did he touch the poles, and it is doubtful whether he even noticed +them. He was not very hungry at this time, and after a few minutes +active work he virtually gave up trying to get the food. + +Two days later, on May 3, the box was once more placed in position, this +time with a half banana in the middle and a small piece of banana near +each open end. The two poles lay on the floor of the cage, each several +feet distant from the box. Julius was eager for food. When released he +went immediately to the box, reached in and obtained a piece of banana +from the end nearer the laboratory. He then looked in and saw the piece +near the middle of the box. His next move was to pick up the eight foot +pole and push it into the box, but before pushing it all the way +through, he stopped and began to pull at the box in various ways. +Shortly he returned to the pole and twice thrust it in as far as he +could reach. The first time, after thrusting it all the way through, he +pulled it out and examined the end as though expecting the banana to +come out with it. After a third attempt he looked into the box, +presumably seeing the banana, then turned a backward somersault, came to +the end of the cage, and looked at me. Had it been at all possible, he +would have taken me by the hand and led me to the box as a helper. After +a few seconds, he returned to the pole, pried the lid of the box with +it, then gnawed at the pole. For about five minutes he worked fairly +rapidly and steadily, using the poles, pulling, gnawing, and walking +about. + +His next move was to go to the opposite end of the box, look in, take +the piece of banana which was near the opening, then pick up the second +pole, which had not previously been noticed, and after a number of +attempts, push it into and through the box, looking after it and then +pulling it out and looking into the box. Having done this he again came +to my end of the cage, and from there returned to try once more with the +pole which he had first used. He pushed this pole all the way through, +then walked to the other end of the box, looked in and reaching in, +obtained the banana which had been pushed far enough along to be within +his grasp. Figures 29, 30 and 31 of plate V show stages of this process. + +Julius had worked twenty-four minutes with relatively little lost time +before succeeding. He had shown almost from the start the idea of using +the pole as an instrument, and his sole difficulty was in making the +pole serve the desired purpose. + +The experiment was rendered still more crucial on May 5 by the placing +of the two poles upright in opposite corners of the large cage. For a +few minutes after he entered the cage, Julius did not see them, and his +time was spent pulling and gnawing at the box. Then he discovered one of +the poles, seized it, and pushed it into the box. He tried four times, +then went and got the other pole and pushed it into the opposite end of +the box. Twice he did this, then he returned to the original pole, +bringing the second one with him. He pushed it in beside the first, and +as it happened, shoved the banana out of the opposite end of the box. +But he did not see this, and only after several seconds when he happened +to walk to that end of the box did he discover the banana. The total +time until success was fifteen minutes. + +Subsequently the ape became very expert in using the pole to obtain the +banana, and often only a minute or two sufficed for success. It was not +possible for him to direct the stick very accurately, for when he was in +such a position that he could look through the box, he could not work +the stick itself. It was, therefore, always a matter of chance whether +he obtained the banana immediately or only after a number of trials. + +Although it is possible that the use of the poles in this experiment was +due to observation of human activities, it seems probable in the light +of what we know of the natural behavior of the anthropoid apes that +Julius would have solved this problem independently of human influence. +It was the expectation of the experimenter that the pole would be used +to push the banana through the box, but as a matter of fact the ape used +it, first of all, to pull the food toward him, thus indicating a natural +tendency which is important in connection with the statements just made. +Subsequently he learned that the banana must be pushed through and +obtained at the farther end of the box. I am not prepared to accept the +solution of this problem as satisfactory evidence of ideation, but I do +know that few observers could have watched the behavior of the orang +utan without being convinced that he was acting ideationally. + + +_Draw-in Experiment_ + +An interesting contrast with the box and pole test is furnished by what +may be called the draw-in experiment. This was planned as a simple test +of Julius's ability to use a stick to draw things into his cage from +beyond the wire side. A board was placed, as is shown in figure 34 of +plate VI, with sides to hold a banana, carrot, or some other bit of +food, in position. In the actual test either a carrot or a banana was +placed about two feet from the wire netting and a stick two feet long +was then put into the cage with the ape. + +When this situation was first presented to Julius, he looked at the +banana, reached for it, and failing, picked up a bag from the floor of +the cage and tried to push it through the wire mesh toward the banana. +He also used a bit of wire in the same way, but was unable thus to get +the food. As soon as a stick was placed in his cage, he grasped it and +used it in a very definite, although unskillful, way to pull the banana +toward him. He was extremely eager and impatient, but nevertheless +persistent in his efforts, and within five minutes from the beginning of +the first trial, he had succeeded in getting two pieces of banana, using +always his left hand to manipulate the stick. This test was repeated a +number of times with similar results. He had from the first the ability +to use a stick in this way, and the only difficulty with the test as a +means of obtaining evidence of ideational behavior is that the +possibility of imitation of man cannot be certainly excluded. + + +_Lock and Key Test_ + +By my assistant it was reported on May 5 that the orang utan had been +seen to place a splinter of wood in a padlock which was used on the +cages and to work with it persistently. It looked very much like +imitation of the human act of using the key, and I therefore planned a +test to ascertain whether Julius could readily and skillfully use a key +or could learn quickly to do so by watching me. + +The first test was made on May 15 with a heavy box whose hinged lid was +held securely in position by means of a hasp and a padlock. The key, +which was not more than an inch in length, was fastened to a six inch +piece of wire so that Julius could not readily lose it. With the animal +opposite me, I placed a piece of banana in the box, then closed the lid +and snapped the padlock. I next handed Julius the key. He immediately +laid it on the floor opposite him and began biting the box, rolling it +around, and occasionally biting also at the lock and pulling at it. +During these activities he had pulled the box toward his cage. Now he +suddenly looked up to the position where the banana had been suspended +in the box experiment. Evidently the box had suggested to him the +banana. For thirty minutes he struggled with the box almost +continuously, chewing persistently at the hinges, the hasp, or the lock. +Then he took the key in his teeth and tried to push it into one of the +hinges, then into the crack beneath the lid of the box. + +Subsequently I allowed him to see me use the key repeatedly, and as a +result, he came to use it himself now and then on the edge of the box, +but he never succeeded in placing it in the lock, and the outcome of the +experiment was total failure on the part of the animal to unfasten the +lock of his own initiative or to learn to use the key by watching me do +so. I did not make any special attempt to teach him to use the key, but +merely gave him opportunity to imitate, and it is by no means impossible +that he would have succeeded had the key been larger and had the +situation required less accurately coordinated movements. However, it is +fair to say that the evidence of the idea of using the key in the lock +was unconvincing. My assistant's observation was, perhaps, misleading in +so far as it suggested that idea. It may and probably was purely by +accident that the animal used the splinter on the padlock. + + +2. Skirrl, _Pithecus irus_ + + +_Box Stacking Experiment_ + +The monkey Skirrl was tested by means of the box stacking experiment +much as Julius had been. On August 23, with a carrot suspended six feet +from the floor of the large cage and three boxes in distant corners, the +animal was admitted and his behavior noted. + +The boxes, which were made of light, thin material, ranged in size from +one six inches in its several dimensions to one twenty inches long, +thirteen inches wide, and eleven inches deep. Only by using at least two +of these boxes was it possible for the animal to reach the carrot. + +Immediately on admission to the cage, Skirrl began to gnaw at the boxes, +trying with all his might to tear them to pieces. After some thirty +minutes of such effort, interrupted by wanderings about the cage and +attempts to get at the other monkeys, he suddenly went to the largest +box of all, set it up on end almost directly under the carrot, mounted +it, and looked up at the food. It was still beyond his reach and he made +no effort to get it, but instead, he reached from his perch on the big +box for the next smaller box, which was approximately sixteen inches, by +fourteen, by twelve. This he succeeded in pulling toward him, at the +same time raising it slightly from the floor, but his efforts caused the +large box to topple over and he quit work. The experiment was +discontinued after a few minutes, the total period of observation having +been thirty-five minutes. + +Skirrl handled the boxes with ease and with evident pleasure and +interest. He also noticed the carrot at various times during the +interval, but his attention was fixed on it only for short periods. + +The test was continued on August 24 when, instead of a carrot, a half +banana was used as bait. It was placed only five feet from the floor, +and three boxes were as formerly placed in distant corners of the cage. +When admitted, Skirrl looked at the banana, then pulled one of the boxes +toward it, but instead of mounting, he went to the smallest box and +began to gnaw it. Shortly, he mounted the middle sized box and looked up +toward the banana, but the box was not directly under the bait, and in +any event, it would have been impossible for him to reach it. He next +went to the largest box, gnawed it vigorously, turned it over several +times, and then abandoned it for the middle sized box, from which by +skillful use of his teeth and hands, he quickly tore off one side. + +By this time, apparently without very definitely directed effort on the +part of the monkey, all three of the boxes were in the center of the +cage and almost directly beneath the banana. Skirrl climbed up on the +largest box and made efforts to pull the middle sized one up on to it, +the while looking at the banana every few seconds. He did not succeed in +getting the boxes properly placed, and after a time began moving them +about restlessly. + +His behavior plainly indicated that hunger was not his chief motive. He +was more interested in playing with things or in working with them than +in eating, and the satisfaction of tearing a box to pieces seemed even +greater than that of food. It is especially noteworthy that when Skirrl +attempts to dismember a box, instead of starting at random, he searches +carefully for a favorable starting point, a place where a board is +slightly loosened or where a slight crack or hole enables him to insert +his hand or use his teeth effectively. Many times during this experiment +he was observed to examine the boxes on all sides in search of some weak +point. If no such weak point were found, he shortly left the box; but if +he did find a favorable spot, he usually succeeded, before he gave up +the attempt, in doing considerable damage to the box. + +Following the behavior described above, Skirrl returned to the middle +sized box, placed it on end under the banana, mounted, and looked upward +at the bait, but as it was a few inches beyond his reach, he made no +attempt to get it, but instead, after a few seconds, went to the +smallest box, and finding a weak point, began to tear it to pieces. + +Later he rolled what was left of the smallest box close to the other two +boxes, nearly under the banana, and the remainder of his time was spent +gnawing at the boxes and playing with pieces which he had succeeded in +tearing from them. During the remainder of the thirty minute interval of +observation, no further attention was given the bait. + +Again, on August 25, the test was tried, but this time with boxes whose +edges had been bound with tin so that it was impossible for the monkey +to destroy them. He spent several minutes searching for a starting point +on the middle sized box, but finding none, he dragged it under the +banana, looked up, mounted the box, but, as previously, did not reach +for the bait because it was beyond his reach. He then played with the +boxes for several minutes. Finally he worked the two smaller boxes to a +position directly under the banana, put the middle sized one on end, +mounted it, and looked at the bait, but again abandoned the attempt +without reaching. + +During the thirty minutes of observation he made no definite effort to +place one box upon another. Three times he mounted one or another of the +boxes when it was under the banana or nearly so, but in no case was it +possible for him to reach the bait. + +From the above description of this monkey's behavior, it seems fairly +certain that with sufficient opportunity, under strong hunger, he would +ultimately succeed in obtaining the bait by the use of two or more +boxes. For his somewhat abortive and never long continued efforts to +drag two boxes together or to place the one upon the other clearly +enough indicate a tendency which would ultimately yield success. The +possibility of imitation is not excluded, for Skirrl had opportunities +to see Julius and the experimenter handle the boxes. + +Because of the other work which seemed more important at the time, this +experiment was not continued further. The results obtained suggest the +desirability of testing thoroughly the ability of monkeys to use objects +as only the anthropoid apes and man have heretofore been thought capable +of using them. + + +_Box and Pole Experiment_ + +Skirrl was first tested with the box and pole experiment on August 12. +As in the case of Julius, a half banana was placed in the middle of the +long box and the attention of the monkey was attracted to the bait by +small pieces of carrot placed near each open end. Two poles were placed +near the box on the floor of the cage. When admitted to the cage Skirrl +went almost directly to the ends of the box, took the pieces of carrot +which were in sight, but apparently failed to perceive the bait in the +middle of the box. For a while he played with the locks on the box, +shoved it about, and amused himself with it, showing no interest in +obtaining the food. Later he looked through the box and saw the banana. +He then dragged the box about, apparently trying to get it into his +cage, but he gave no attention to the poles nor did he make any evident +effort to obtain the banana which was easily visible in the center of +the box. The period of observation was only twelve minutes. + +On August 24 this experiment was repeated with an important modification +of the apparatus in that the wooden lid of the long box had been +replaced by a wire cover through which the animal could see the bait. +Two poles were as formerly on the floor of the cage, not far from the +box. Skirrl almost immediately noticed the banana and tried to get it by +gnawing at the box. He did not once reach in at the ends of the box, but +he did handle the poles, throwing them about and pounding with them. +There was not the slightest attempt to use them in obtaining the bait. + +This experiment was later repeated three times at intervals of a number +of days, but in no case did Skirrl show any tendency to use the poles as +means of obtaining the food. + + +_Draw-in Experiment_ + +This also was arranged in the same manner as for Julius, and on each of +five days Skirrl was allowed at least thirty minutes to work for the +bait. Either a banana or a carrot was each day placed on the board well +beyond his reach, and one or two, usually two, small sticks were put +into his cage. Not once during the several periods of observation did +Skirrl make any attempt to use a stick or any other object as a means of +drawing the food to him. Instead, he reached persistently with his arm, +pulled and gnawed at the wires which were in his way, and occasionally +picked up and gnawed or pounded with the sticks in the cage. His +attention every now and then would come back to the food, but it tended +to fluctuate rather rapidly, and in the regular period of observation, +thirty minutes, it is unlikely that he attended to the bait itself for +as much as five minutes. In this respect as well as many others, +Skirrl's behavior contrasts sharply with that of the orang utan. + +The results of this experiment indicate the lack in the monkey of any +tendency or ability, apart from training, to use objects as means of +obtaining food. Ways of using objects as tools which apparently are +perfectly natural to the anthropoid apes and to man are rarely employed +by the lower primates. + + +_Hammer and Nail Test_ + +One day I happened to observe Skirrl playing with a staple in his cage. +He had found it on the floor where it had fallen and was intently +prodding himself with the sharp points, apparently enjoying the unusual +sensations which he got from sticking the staple into the skin in +various portions of his body, and especially into the prepuce. + +A few days later I saw him playing in similar fashion with a nail which +he had found, and still later he was seen to be using a stick to pound +the nail with. This suggested to me the hammer and nail test. + +A heavy spike was driven into an old hammer to serve as an +indestructible handle. This hammer, along with a number of large wire +nails and a piece of redwood board, was then placed in the monkey's +cage. Skirrl immediately took up the hammer, grasping the middle of the +handle with his left hand, and with his right hand taking up a nail. He +then sat down on the board, examined the nail, placed the pointed end on +the board, and with well directed strokes by the use of the head of the +hammer drove the nail into the board for the distance of at least an +inch. He then tried to pull it out, but was forced to knock it several +times with the hammer before he could do so. + +This performance, during the next few minutes, was repeated several +times with variations. Often the side of the hammer was used instead of +the head, and occasionally, as is shown in figure 8 of plate II, he +seized the hammer well up toward the juncture of the same with the +spike. This figure does justice to the performance. At the moment the +picture was taken, Skirrl's attention had been attracted by a monkey in +an adjoining cage, and he had momentarily looked up from his task, the +while holding nail and hammer perfectly still. + +This test was repeated on various days, and almost uniformly Skirrl +showed intense interest in hammer and nails and used them more or less +persistently in the manner described. Occasionally, apparently for the +sake of variety, he would put the blunt end of the nail on the board and +hammer on the point. Again, he would try persistently to drive the nail +into the cement floor, and once by accident, when hammer and nails were +left in his cage over night, he succeeded in making several holes in the +bottom of his sheet iron water pan. There was no doubting the keen +satisfaction which the animal took in this form of activity. + +It is impossible to say that the behavior was not imitative of man, for +Skirrl, along with all of the other monkeys, had had abundant +opportunity to see carpenters working. But this much can be said against +the idea of imitation,--no one of the other animals, not excepting the +orang utan, showed any interest whatever in hammer and nails. +Occasionally they would be played with momentarily or pushed about, but +Sobke, Jimmie, Gertie, Julius, although given several opportunities to +exhibit any ability which they might have to drive nails, made not the +least attempt to do so. Evidently we must either conclude that Skirrl +had a peculiarly strong imitative tendency in this direction, or +instead, a pronounced disposition or instinct for the use of objects as +tools. It would seem fair to speak of it as an instinct for mechanical +activity. + +Under this same heading may be described Skirrl's reactions to such +objects as a handsaw, a padlock, and a water faucet. The saw was given +to him in order to test his ability to use it in human fashion, for if +he could so expertly imitate the carpenter driving nails, it seems +likely that he might also imitate the use of the saw. + +As a matter of fact, he showed no tendency to use the saw as we do. +Instead, he persistently played with it in various ways, at first using +it as a sort of plane to scrape with, later often rubbing the teeth over +a board so that they cut fairly well, but never as effectively as in the +hands of a man. After two or three days' practice with the saw, Skirrl +hit upon a method which is, as I understand, used by man in certain +countries, namely, that of placing the saw with the teeth up, holding it +rigid, and then rubbing the object which is to be sawed over it. This +Skirrl succeeded in doing very skillfully, for he would sit down on the +floor of the cage, grip with both feet the handle of the saw, with the +teeth directed upward, then holding either end in his hands, he would +repeatedly rub a stick over the teeth. In this way, of course, he could +make the saw cut fairly well. But still more to his liking was the use +of a spike instead of a stick as an object to rub over the teeth, for +with this he was able to make a noise that would have satisfied even a +small boy. + +Further light is shed on the force of the tendency to imitate man by the +saw test. After Skirrl had been given an opportunity to show what he +could do with the tool spontaneously, I demonstrated to him the approved +human way of sawing. Often he would watch my performance intently as +though fascinated by the sound and motion, but when given the tool he +invariably followed his own methods. Although I repeated this test of +imitation several times on three different days, the results were wholly +negative. + + +_Other Activities_ + +One day as Skirrl was being returned to his own cage by way of the +larger cage, he picked up an unfastened padlock and carried it into the +cage with him. For more than an hour he amused himself almost without +interruption by playing with this lock. The things which he did with it +during that time would require pages to describe. His interest in it was +very similar to that which he had exhibited in hammer and nails, saw, +and indeed any objects which he could play with. The lock was pounded in +various ways, bitten, poked with nails, hooked into the wires of the +cage, used to pull on, pounded with a stick, used to hammer on the floor +of the cage with, and in fine, manipulated in quite as great a variety +of ways as a human being could have discovered. Finally it was hooked to +the side of the cage and snapped shut, and as Skirrl was unable to +dislodge it from this position, he shortly gave up playing with it. + +At the end of the large cage and just outside the wire netting was a +faucet to which a hose was usually attached. The valve could be opened +by turning a wheel-shaped hand piece. Both Skirrl and Julius learned to +turn this wheel in order to get water to play with, but usually the +former's strength was not sufficient to turn on the water. The latter +could do it readily. The indications are that both animals profited by +seeing human beings turn on the water. This unquestionably attracted +their attention to the faucet, and probably by playing with it they +accidentally happened upon the proper movement. At any rate, Skirrl's +behavior was significant in this connection, for he would pick up the +hose to see if water were flowing, and if it were not, he would throw it +down, go directly to the faucet, and try to turn the wheel. The +association of the wheel with the desired flow of water was therefore +definitely established. Shall we describe the act as ideational? It +seems the natural thing to do. + + +3. Sobke, _Pithecus rhesus_ + + +_Box Stacking Experiment_ + +For this test, in the case of Sobke, three light boxes made of redwood +about one-third of an inch thick were used. The smallest, box 1, was six +inches in each direction, the next larger, box 2, was twelve inches, and +the third, box 3, eighteen inches. As in the case of the other animals, +bait, either banana or carrot, was suspended from the middle of the roof +of the large cage at such distance from the floor as to be reached by +the animal only by the use of the boxes. + +The first observations on Sobke were made on June 14. The three boxes +had been placed in the form of a pyramid directly under the banana, +which hung about eighteen inches above the uppermost box. Sobke's +attention while in his cage had been attracted to the bait by seeing me +fastening it in position, but when admitted to the large cage, he simply +glanced at it and then wandered about the cage, picking up bits of food +and struggling to get at the other monkeys. This he did for about five +minutes. He then went to the boxes, placed his hands on top of the +bottom one, but did not climb up on it. A few minutes later he returned +to the box again, climbed up, and readily reached the food, which he ate +while resting on boxes 1 and 2. + +I now replaced the bait and gave the monkey a second chance to obtain +it. Almost immediately he climbed up as far as the second box, but +although he could reach the banana only from the uppermost box, he +deliberately shoved it off to the ground and sat down upon box 2. As he +was unable to obtain the banana from this, he soon began to gnaw and +pull at it, and as he was succeeding all too well in his efforts to tear +the box to pieces, he had to be returned to his cage. + +The most important features of his behavior were, first, his stealthy +and indirect manner, and second, his failure to use other means of +obtaining the bait than that supplied by the observer. Instead of +looking straight at the experimenter, or at the object which he wished +to obtain, he apparently looked and attended elsewhere. For this reason +it was often difficult to decide whether or not he had noticed the bait +or the boxes. Finally I was led to conclude that he usually knew exactly +what was going on and had in his furtive way noted all of the essential +features of the situation, and that his manner was extremely indicative +of his mental attitude of limited trust. Both Julius and Skirrl went to +the opposite extreme in the matter of directness, or as we should say in +human relations, frankness. They would look the experimenter directly in +the eye, and they usually gazed intently at anything, such for example +as the bait, that interested them. Sobke, even when very hungry, instead +of going directly toward the bait, and trying to obtain it, usually did +various other things as though pretending that he had no interest in +food. + +On the following day, June 15, the three boxes were again placed nearly +under the banana, but this time the two smaller boxes, numbers 1 and 2, +were pushed to the extreme end of the lower box and so far from the bait +that it could not be reached from box 1. It was necessary then for the +animal to push boxes 1 and 2 along on box 3 until they were nearer the +bait. + +Sobke, when admitted to the cage, evidently noticed the banana, but as +formerly, he made no immediate effort to obtain it. After wandering in +search of food and quarreling with the other monkeys for several +minutes, he went to the boxes, pushed the topmost one, number 1, off on +to the floor, and then carried it into his cage where he quickly tore +one side off. He next returned to the large cage, climbed up on box 2, +and he was able, by jumping, to reach and obtain the banana. + +As Sobke was very good at jumping, his new method rendered the box +stacking experiment of uncertain value, since it was next to impossible +so to arrange the spatial relations of bait and boxes that he should be +neither discouraged by too great a distance nor encouraged to jump by +too small a distance. Evidently it would be more satisfactory to +simplify the conditions by trying to discover, first of all, whether he +would use a single box as a means of reaching the reward. + +In pursuance of this idea, I suspended a piece of bread five feet from +the floor of the cage, and a few feet to one side of it, I placed a box +from which it could be reached, or at least easily seized by jumping. +Sobke shortly walked to a point beneath the bait and leaping into the +air, seized it. + +I then replaced the bait, raising it to a height of five feet ten inches +from the floor of the cage. When I had retired, Sobke placed himself in +the proper position beneath, looked up at it, but went away without +jumping for it. During the remaining ten minutes of observation, he paid +no further attention to the bait, having satisfied himself evidently +that it was beyond his reach. + +My use of this test was concluded on June 16 when once more I suspended +a piece of bread six feet from the floor and placed a few feet to one +side the eighteen inch box, number 3, from which had the monkey pushed +it to a point directly under the bread, he could have obtained the food +easily. Sobke noticed the food promptly, and from time to time as he +wandered about, he glanced at it out of the corner of his eye, but not +once did he sit down and look at it steadily and directly as Julius and +Skirrl might have done. + +In the first twenty minutes of observation the monkey made no attempt +either to use the box or to reach the food by jumping. I then placed the +box directly under the bait, and scarcely had I withdrawn from the cage +before Sobke climbed up on it and looked toward the food. He could not +reach it without jumping, and he made no effort to get it. I had left a +second box in the cage,--one which I had been using as a seat. Sobke now +went to this box, placed his hands on it, looked toward the bait, and +then went to a distant part of the cage. No further indications were +obtained during the remainder of the period of observation of interest +in the boxes as possible means of obtaining the desired food. + +It is of course obvious that this experiment was not long enough +continued to justify the conclusion that either Sobke or Skirrl could +not use the boxes or even learn to place one box upon another in order +to obtain the bait. The experiment, like several others which are being +described briefly, was used to supplement the multiple-choice +experiment, and the experimenter's chief interest was to discover the +number and variety of methods which would be used by the animal in +the first few presentations of a situation. It is practically certain +that both of these monkeys would have succeeded ultimately in solving +the problem of obtaining the food had they been left in the cage with a +number of boxes, for Skirrl very early indicated interest in moving the +boxes about, and Sobke showed a tendency in that direction which perhaps +was inhibited partially by his distrust of the experimenter. + + +_Draw-in Experiment_ + +For Sobke, as for Julius and Skirrl, the draw-in test was made by +putting food on a shelf outside the cage, beyond the reach of the +animal, and placing in the cage with the animal one or two sticks long +enough to be used for drawing in the bait. + +Sobke was first given this test on July 24. He tried persistently to +reach the banana with his hand, seized the box which supported the bait, +shook it, picked up one or other of the sticks, and chewed at it +repeatedly, but not once did he make any move to use a stick to draw the +food toward him. + +This experiment was repeated on July 27, 29, 30 and 31, a period of +thirty minutes being allowed on each day for observation. At no time did +Sobke show any inclination to use either a stick or any other object as +a means of reaching the bait. Instead, he confined himself strictly to +the use of hands and teeth. + +This test makes it fairly certain that Sobke had no natural tendency to +use objects as tools. In so far as he attended to things about the cage +or laboratory, it seemed to be rather to play with them in a general way +than to use them ideationally or otherwise for definite purposes. + +The definitely negative result of the draw-in experiment rendered +needless prolonged observation with the box and pole test, whose results +are now to be presented. + + +_Box and Pole Experiment_ + +The eighty-four inch box, previously used for a similar test with +Julius, was presented to Sobke on August 24, the wooden cover having +been replaced by a wire one so that the monkey could readily see the +bait in the middle of the box. Sobke, when admitted to the large cage, +went directly to the box and at once discovered the banana which was +midway between the ends. He evidently desired it. Shortly, he went to +one end of the box and looked in. This he repeated later. He also shook +the box and tried to pull it about and tear it with his teeth, but to +the two poles lying nearby on the floor of the cage he gave not the +slightest attention during a thirty minute period of observation. + +The experiment was not repeated because of more important work. + + +_Other Activities_ + +In more respects than I have taken time to enumerate in the above +descriptions of behavior, the relations of Sobke to objects differed +from those of Skirrl, and still more from those of Julius. Hammer, +nails, saw, stones, sticks, locks, and various other objects received +relatively little attention from Sobke unless they happened to come in +his way; then they were usually pushed aside with but scant notice. +Rarely he would carry something to the shelf of his cage with him, but +as a rule only to lay it down and attend to something else. Skirrl, on +the contrary, attended persistently to anything new in the shape of a +movable object. He was extremely partial to objects which could be +manipulated by him in various ways, and especially to any thing with +which he could make a noise. His interest in hammer and nails, saw, +locks, etc., seemed never to wane. I have seen him play for an hour +almost uninterruptedly with a hammer and a nail, or even with a big +spike which he could use to pry about his cage. In the absence of +anything more interesting, even a staple or a small nail might receive +his undivided attention for minutes at a time. How important is the +species difference in this connection, I have no means to judge, but if +we may not consider these different modes of behavior characteristic of +_P. rhesus_ as contrasted with _P. irus_, we must conclude that +remarkable individual differences exist among monkeys, for whereas +Skirrl is by nature a mechanical genius, Sobke has apparently no such +disposition. I can imagine no more fascinating task than the careful +analytical study of the temperaments of these two animals. Skirrl's +behavior has importantly modified my conception of genius. + + + +V + +MISCELLANEOUS OBSERVATIONS + + +1. _Right- and left-handedness_ + +Several years ago Doctor Hamilton reported to me observations which he +had made on preference for the right or left paw in dogs. He has not, I +believe, published an account of his work. Subsequently, Franz observed +a similar preference in monkeys which, according to his report, exhibit +marked tendency to be right-handed, left-handed, or ambidextrous. + +My own observations, although they are wholly incidental to my other +work, seem worthy of description at this point. I noted, first of all, +that the orang utan Julius tended to use his left hand. He by no means +limited himself to this, but in difficult situations he almost +invariably reached for food or manipulated objects in connection with +food getting with the left hand. Figures 23 and 24 of plate V, show him +reaching for a banana with the left hand. Likewise, figure 34 exhibits +the use of the left hand in the draw-in experiment. + +So marked was Julius's preference for his left hand that I became +interested in observing similar phenomena in the monkeys. Skirrl, when +driving nails, held the hammer with his left hand and the nail with his +right hand. The fact that he never was observed to reverse the use of +the hands is surprising, for other observations indicate that he +preferred the right hand for certain acts. + +Stimulated by the obvious left-handedness, in certain connections, of +Julius and Skirrl, I tested the preference of several of the monkeys in +the following simple way. Standing outside the cage I would hold out a +peanut to a hungry animal, keeping it so far from the cage that the +monkey could barely reach it with its fingers. I noted the hand which +was used to grasp the food. Next I varied the procedure by placing the +peanut on a board in order to make sure that I was not definitely +directing the animal's attention. + +With Sobke the following results were obtained. In forty trials given on +two different days, he reached for and obtained the food each time with +his left hand. Only by holding the bait well toward the right side of +his body was it possible to induce him to use the right hand. So far as +may be judged from these observations and from others in connection with +the experiments, this animal is definitely left-handed. + +With Skirrl the results are strikingly different. As stated above, he +used the hammer consistently with his left hand, but in twenty attempts +to obtain food by reaching, he used his right hand seventeen times and +his left only three times. It was quite as difficult to induce him to +use his left hand for this purpose as it was to induce Sobke to use his +right. We must therefore conclude that Skirrl is right-handed in +connection with certain movements and left-handed in others. + +The monkey named Gertie in the reaching experiment consistently used her +left hand, never once using the right. + +Jimmie, so far as it was possible to make tests with him, also used his +left hand, but it should be said that the results are unsatisfactory +because he was at the time extremely pugnacious and paid attention to +the experimenter rather than to the food. + +Scotty, in the first series of ten trials, used his right hand eight +times, his left twice. In the second series, given the following day, he +used the right hand three times and the left seven times. From this we +should have to infer that he is ambidextrous. + +A female _rhesus_ monkey which had been brought to the laboratory only a +few days previously showed a preference for the right hand by the use of +it fourteen times to six. + +In connection with these data which are, I should repeat, too scanty to +be of any considerable value, I wish to describe my own experience. +Although naturally left-handed, I am by training right-handed to the +extent of having been able to use my hands in writing and in various +other activities equally well at the age of twelve. I am at present +ambidextrous in that there are many things which I do with equal +readiness and skill with either hand. Delicate, exact, and finely +coordinated movements, such as those of writing and using surgical +instruments, I perform always with my left hand while grosser movements +involving the whole hand or arm, I am rather likely to perform with my +right hand. + +It seems not improbable in the light of my own experience that we shall +find some specialization among the lower animals with respect to +preference for right and left hand or arm. I should not be at all +surprised to discover that it is the rule for animals to possess or to +develop readily definite preference for one hand in connection with a +given act of skill and to have quite as definite a preference for the +other hand in connection with a radically different kind of act. + + +2. _Instinct and emotion_ + +Of the many presumably instinctive modes of behavior which were +observed, only those which have to do with social relations seem +especially worth reporting. From among them I shall select for +description a few which have already been referred to in connection with +the experimental observations. + + +_Maternal Instinct_ + +Aspects of the maternal instinct I had opportunity to observe in Gertie, +who on February 27 gave birth to a male infant, I present below the +substance of a previously published note on her behavior (Yerkes, 1915). + +"On February 27 one of the monkeys of our collection gave birth, in the +cages at Montecito, to a male infant. The mother is a _Macacus +cynomolgus rhesus_ (_P. irus rhesus_) who has been described by Hamilton +(1914, p. 298) as 'Monkey 9, Gertie, _M. cynomolgus rhesus_ (_P. irus +rhesus_). Age, 3 years 2 months. (She is now, May 1, 1915, 4 years and 6 +months.) Daughter of monkeys 3 and 10. First pregnancy began September, +1913.' The result of this pregnancy was, I am informed, a still-birth. + +"The second pregnancy, which shall now especially concern us, resulted +likewise in a still-birth. Parturition occurred Saturday night, and the +writer first observed the behavior of the mother the following Monday +morning. In the meantime the laboratory attendant had obtained the data +upon which I base the above statements. + +"At the time of parturition Gertie was in a 6 by 6 by 12 foot out-door +cage containing a small shelter box, with an exceptionally quiet and +gentle male (not the father of the infant) who is designated in +Hamilton's paper as Monkey 28, Scotty. + +"My notes record the following exceptionally interesting and genetically +important behavior. On March 1, when I approached her cage, Gertie was +sitting on the floor with the infant held in one hand while she fingered +its eyelids and eyes with the other. Scotty sat close beside her +watching intently. When disturbed by me the mother carried her infant to +a shelf at the top of the cage. Repeatedly attempts were made to remove +the dead baby, but they were futile because Gertie either held it in her +hands or sat close beside it ready to seize it at the slightest +disturbance. + +"Especially noteworthy on this, the second day after the birth of the +infant, are the male's, as well as the female's, keen interest in the +body and their frequent examinations of the eyes, as if in attempts to +open them. Often, also, the mother searched the body for fleas. + +"Observations were made from day to day, and each day opportunity was +sought to remove the body without seriously frightening or exciting the +female. No such opportunity came, and during the second week the corpse +so far decomposed that, with constant handling and licking by the +adults, it rapidly wore away. By the third week there remained only the +shriveled skin covering a few fragments of bone, and the open skull from +the cavity of which the brain had been removed. This the mother never +lost sight of: even when eating she either held it in one hand or foot, +or laid it beside her within easy reach. + +"Gradually this remnant became still further reduced until on March 31 +there existed only a strip of dry skin about four inches long with a +tail-like appendage of nearly the same length. + +"The male, Scotty, on this date was removed to another cage. Gertie made +a great fuss, jumping about excitedly and uttering plaintive cries when +she discovered that her mate was gone. Whenever I approached her cage +she scurried into the shelter box and stayed there while I was near. +This behavior I never before had observed. It continued for two days. On +April 2, it was noted that she had lost her recently acquired shyness +and she no longer made any attempts to avoid me. As usual, on this date, +she was carrying the remnant about with her. + +"The following day, April 3, Gertie was lured from her cage to a large +adjoining compartment for certain experimental observations. After she +had been returned to her own cage the remnant was noticed on the floor +of the large cage. I picked it up. Gertie evidently noticed my act; for +although at a distance of at least ten feet from me, she made a sharp +outcry and sprang to the side of the cage nearest me. I held the piece +of skin (it looked more like a bit of rat skin than the remains of a +monkey) out to her and she immediately seized it and rushed with it to +the shelf at the top of the cage. + +"Two days later the remnant was missing, and careful search failed to +discover it in the cage. It is probable that Gertie had carelessly left +it lying on the floor whence it was washed out when the cages were +cleaned. On this date Gertie seemed quieter than for weeks previously. + +"Thus it appears that during a period of five weeks the instinct to +protect her offspring impelled this monkey to carry its gradually +vanishing remains about with her and to watch over them so assiduously +that it was utterly impossible to take them from her except by force. + +"After reading this note in manuscript, Doctor Hamilton informed me that +Gertie had behaved toward her first still-birth as toward her second. +And, further, that Grace, a baboon, also carried a still-birth about for +weeks. + +"I am now heartily glad that my early efforts to remove the corpse were +futile, for this record of the persistence of maternal behavior seems to +me of very unusual interest to the genetic psychologist." + + +_Fear_ + +In connection with the multiple-choice experiments Skirrl exhibited what +seemed to be instinctive fear as a result of his unfortunate experience +with nails in the floor of box 1. He seemingly referred his misadventure +to some unseen enemy under the floor, and this in spite of the fact that +he was given abundant opportunity to examine the floor of the box, but +not until after the dangerous nails had been clinched. His long +continued avoidance of the experiment boxes and his still more +persistent hesitancy in entering them, coupled with his almost ludicrous +efforts to see beneath the floor through the holes cut for the staples +on the doors, gave me the impression of superstitious fear of the +unseen. As I watched and recorded his behavior day after day during the +period of most pronounced fear, I could not avoid the thought that the +instinctive fear of snakes had something to do with his peculiar +actions, and although I have never studied either the natural or the +acquired responses of monkeys to snakes, I suspect that lacking such +instinctive equipment, Skirrl would have behaved differently as a result +of the pricks which he received from the nails. It is needless to +redescribe his acquired fear of whiteness as it manifested itself in the +freshly painted apparatus. Accompanying these instructive modes of +response and their emotions are suggestions of peculiarly interesting +problems as well as of modes of attacking them. As a matter of fact, +Skirrl's fear-reactions did much to alter my conception of the +constitution of his mind. I should not have been surprised by the +features of behavior exhibited, but I was by no means prepared for their +persistence, and for the highly emotional attitude toward the particular +situation. Only an organism of complexly constituted nervous system and +fairly highly developed affective life could be expected to respond as +did this monkey. As has been suggested above, I find the appeal to +instinct, modified by experience, a natural mode of accounting for the +unexpected features of Skirrl's behavior. + + +_Sympathy_ + +The instinctive playfulness of the young monkey Tiny contrasted most +strikingly with the more serious, if not more sedate, modes of behavior +of the older individuals. + +During the greater part of my period of observation Tiny was cage-mate +of Scotty, the most calm and apparently lazy of all the monkeys. Tiny +delighted in teasing Scotty, and her varied modes of mildly tormenting +him and of stirring him to pursuit or to retaliation were as interesting +as they were amusing. Her most common trick was to steal up behind him +and pull the hair of his back, or seize his tail with her hands or +teeth. Often when he was asleep she would suddenly run to him, give a +sudden jerk at a handful of hairs, and leap away. He was surprisingly +patient, and I never saw him treat her roughly in retaliation. + +Another of Tiny's favorite forms of amusement was that of trying to stir +up the other monkeys to attacks on one another. She very cleverly did +this by pretending that she herself was being attacked. The instant the +older animals began to show hostility toward one another she would leap +out of the way and watch the disturbance with evident satisfaction. It +was this mode of behavior in the little animal which ultimately provided +opportunity for the observations which I wish now to report as +indicative of sympathetic, possibly I may say altruistic, emotions. + +Tiny was confined with Scotty in a cage adjoining the one in which +Jimmie and Gertie were being kept. The cages were separated by wire +netting of half-inch mesh. + +One morning as I was watching the behavior of the animals in the several +cages, I noticed Tiny dressing with her teeth a wounded finger. It had +evidently been bitten by one of the other animals, in all probability +either by Jimmie or Gertie. Tiny was trimming away the loose bits of +skin very neatly and cleansing the wound. After working at this task for +a few minutes, she quickly climbed up to the shelf near the top of her +cage, and by rushing to the partition wire between the two cages, she +lured Gertie to an attempted attack on her. Gertie sprang up to the +partition, placed her hands on it, with the fingers projecting through +the meshes, and attempted to seize Tiny's fingers with her teeth. But +the latter was too quick for her, and withdrawing her hands, like a +flash seized in her teeth the middle finger of Gertie's left hand. She +then bit it severely and with all her might, at the same time pulling +and twisting violently, often placing the entire weight of her body on +the finger. Her sharp teeth cut to the bone, and it was impossible for +the larger and stronger monkey to tear away. For several seconds this +continued, then Gertie succeeded in escaping, whereupon she at once +retreated to the opposite end of her shelf and proceeded to attend to +her injured finger. She cried, wrung her hands, and from time to time +placed the finger in her mouth as though in an effort to relieve the +pain. By this time Jimmie's attention had been attracted by the +disturbance and he rushed up to the shelf, and facing Gertie, watched +her intently for a few seconds. The look of puzzled concern on his face +was most amusing. Apparently he felt dimly that something in which he +should have intelligent interest was going on, but was unable wholly to +understand the situation. After watching Gertie for a time and trying to +discover what she was doing, which was rendered difficult by her +tendency to turn away from him, in order to shield her injured finger, +he rushed over to the wire partition and made strenuous efforts to seize +Tiny with his hands and teeth. But although she continued close to the +partition and often crowded against it with face and hands flattened on +the wires, he was not able to get hold of her, and after a few vain +attempts he returned to his mate, and again with evident solicitousness +and the most troubled expression, watched her wringing her hands and +chewing or sucking at her injured finger. Shortly he again returned to +the partition and renewed his attempts to seize the young monkey. Thus +he went back and forth from one place of interest to the other several +times, but being unable to achieve anything at either point, he finally +gave up and returned to his breakfast on the floor of the cage. + +I report this incident fully because the behavior of Jimmie was in +marked contrast with the usual behavior of the monkeys. Selfishness +seemed everywhere dominant, while clear indications of sympathetic +emotions were rare indeed. The above is undoubtedly the best evidence of +anything altruistic that I obtained. + +It is possible that Tiny's action was retaliatory, but although it is +practically certain that either Gertie or Jimmie inflicted the wound on +her finger, I of course cannot be sure that the spirit of revenge +stirred her to punish Gertie so severely. Jimmie's part in the whole +affair is, however, perfectly intelligible from our human point of view, +and there seems no reason to doubt that he did experience something like +a feeling of sympathy with his mate, coupled with a feeling of +resentment or anger against Tiny. + + + +VI + +HISTORICAL AND CRITICAL DISCUSSION OF IDEATIONAL BEHAVIOR IN MONKEYS AND +APES + + +It is my purpose in this section to indicate the relations of my work on +monkeys and apes to that of other investigators. Although throughout the +report I have used freely the psychological terms idea and ideation, it +has been my aim to describe the behavior of my animals rather than to +interpret it or speculate concerning its accompaniments. Certain acts I +have designated as ideational simply because they seemed to exhibit the +essential features of what we call ideational behavior in man. Further +study may, and probably will, modify my opinion concerning this matter. +It is of prime importance to analyze ideational behavior so that it may +be accurately described and satisfactorily defined in terms of its +distinguishing characteristics. I had hoped to be able to present a +tentative analysis in this report, but the results of my efforts are so +unsatisfactory that I do not feel justified in publishing them. + +The terms idea and ideation have been used to designate contents of +consciousness which are primarily representative. Nowhere have I +attempted to indicate different types or grades of ideational behavior +and nowhere have I found it necessary to emphasize differences between +image and idea. In general, the acts which I have called ideational have +been highly adaptive, and the learning processes in connection with +which they have appeared have differed strikingly from those of the +selective sort in their abruptness of appearance. + +Extremely interesting and valuable definitions of ideation and +discussions of the characteristics of different sorts of ideas in the +light of original observations on monkeys have been presented by +Thorndike (1901, pp. 1, 2; 1911, p. 174); Kinnaman (1902, p. 200); and +Hobhouse (1915, p. 270). As these authors have contributed importantly +to our knowledge of the behavior of monkeys, their discussions of the +meaning of terms are especially valuable. Serviceable definitions are to +be found, also, in Romanes (1900), Morgan (1906), Washburn (1908), and +Holmes (1911). + + +_Evidences of Ideation in Monkeys_ + +Aside from anecdotal and traveller's notes on the behavior of monkeys +and apes we have only a scanty literature. In fact, the really excellent +articles on the behavior and mental life of these animals may be counted +on one's fingers; and not more than half of these are experimental +studies. I shall, in this brief historical sketch, neglect entirely the +anecdotal literature, since my own work is primarily experimental, and +since its results should naturally be compared with those of other +experimenters. + +Thorndike (1901), the American pioneer in the application of the +experimental method to the study of mind in animals, published the first +notable paper on the psychology of monkeys. His results force the +conclusion that "free ideas" seldom appear in the monkey mind and have a +relatively small part in behavior. That the species of Cebus which he +observed exhibits various forms of ideation he is willing to admit. But +he insists that it is of surprisingly little importance in comparison +with what the general behavior of monkeys as known in captivity and as +described by the anecdotal writers have led us to expect. It is +important to note, however, that Thorndike's observations were limited +to Cebus monkeys which, as contrasted with various old world types, are +now considered of relatively low intelligence. + +In many respects the most thoroughgoing and workmanlike experimental +study of monkeys is that of Kinnaman (1902), who has reported on the +study of various forms of response in _P. rhesus_. He presents valuable +data concerning the learning processes, sensory discrimination, reaction +to number, and to tests of imitation. His results indicate a higher +level of intelligence than that discovered by Thorndike, but this is +almost certainly due to difference in the species observed. Kinnaman +goes so far as to say "We have found evidence, also, of general notions +and reasoning, both of low order" (p. 211). + +The contribution of Hobhouse (1915) to our knowledge of the mental life +of monkeys, although in a measure experimental, is based upon relatively +few and unsystematic observations as contrasted with those of Thorndike +and Kinnaman. It appears, however, that Hobhouse's experiments were +admirably planned to test the ideational capacity of his subjects, and +one can not find a more stimulating discussion of ideation than that +contained in his "Mind in Evolution." The results of his tests made with +a _P. rhesus_ monkey are similar to those of Kinnaman, for almost all of +them indicate the presence and importance of ideas. + +Watson (1908) in tests of the imitative ability of _P. rhesus_ saw +relatively little evidence of other than extremely simple forms of +ideation. But in contrast with his results, those obtained by Haggerty +(1909), in a much more extended investigation in which several species +of monkey were used, obtained more numerous and convincing evidences of +ideation in imitative behavior. Although this author wholly avoids the +use of psychological terms, seeking to limit himself to a strictly +objective presentation of results, it is clear from an unpublished +manuscript (thesis for the Doctorate of Philosophy, deposited in the +Library of Harvard University) that he would attribute to monkeys simple +forms of ideational experience. + +Witmer (1910) reports, in confirmation of Haggerty's results, +intelligently imitative behavior in _P. irus_. + +The work of Shepherd (1910) agrees closely, so far as evidences of +ideation are concerned, with that of Thorndike. He obviously strives for +conservatism in his statements concerning the adaptive intelligence of +his monkeys, all of which belonged to the species _P. rhesus_. At one +point he definitely states that they exhibit ideas of a low order, or +something which corresponds to them. Satisfactory evidences of reasoning +he failed to obtain. + +Franz's (1907, 1911) studies of monkeys, unlike those mentioned above, +have for their chief motive not the accurate description of various +features of behavior but instead knowledge of the functions of various +portions of the brain. His results, therefore, although extremely +interesting and of obvious value to the comparative psychologist, throw +no special light upon the problem of ideation. + +The investigation by Hamilton (1911) of reactive tendencies in _P. +rhesus_ and _irus_ yielded preeminently important data concerning +complex behavior. For the ingenious quadruple-choice method devised by +this observer showed that mature monkeys exhibit fairly adequate types +of response. As Hamilton's interest centered in behavior, he did not +discuss ideation, but this does not prevent the comparison of his data +with those of the present report, and the agreement of his findings with +my own is obvious. + +My work contrasts sharply with that briefly mentioned above in that I +applied systematically and over a period of several months an +experimental method suited to reveal problem solving ability. +Previously, the so-called problem or puzzle-box method had been used as +a means of testing for the presence of ideas. For this I substituted the +multiple-choice method. One of the chief advantages of this new method +is the possibility of obtaining curves of learning for the solution or +attempted solution of relational problems of varying difficultness. I am +confident that these curves of learning will prove far more valuable +than such data as are yielded by the puzzle-box method. + +The Pithecus monkeys, which I studied intensively, yielded relatively +abundant evidences of ideation, but with Thorndike I must agree that of +"free ideas" there is scanty evidence; or rather, I should prefer to +say, that although ideas seem to be in play frequently, they are rather +concrete and definitely attached than "free." Neither in my sustained +multiple-choice experiments nor from my supplementary tests did I obtain +convincing indications of reasoning. What Hobhouse has called articulate +ideas, I believe to appear infrequently in these animals. But on the +whole, I believe that the general conclusions of previous experimental +observers have done no injustice to the ideational ability of monkeys. +It is clearly important, however, that we always should take into +account the species of animal observed, for unquestionably there are +extreme differences in mental development among the monkeys. + +As I view my results in the light of their relations to earlier work, I +am strongly impressed with the importance of the use of improved methods +for the study of complex behavior. The delayed reaction method of +Hunter, the quadruple-choice method of Hamilton, and my multiple-choice +method offer new and promising approaches to forms of activity which +thus far have been only superficially observed. + +The ability exhibited by Skirrl to try a method out and then to abandon +it suddenly is characteristic of animals high in intelligence. Most of +the problems which I presented to my animals would be rated as difficult +by psychologists, for as a rule they involved definite relations and +demanded on the part of the subject both perception of a particular +relation and the ability to remember or re-present it on occasion. + +I was greatly surprised by the slow progress of the monkeys toward the +solution of these problems. It had been my supposition that they would +solve them more quickly than any lower type of mammal, but as a matter +of fact they succeeded less well than did pigs. Their behavior +throughout the work proved that of far greater significance for the +experimenter than the solution of a problem is definite knowledge of the +modes of behavior exhibited from moment to moment, or day to day. This +is true especially of those incidental or accidental modes of response +which so frequently appeared in connection with my work that I came to +look upon them, the surprises of each day, as my chief means of insight. + + +_Evidences of Ideation in Apes_ + +Reliable literature of any sort concerning the behavior and mental life +of the anthropoid apes is difficult to find, and still more rare are +reports concerning experimental studies of these animals. There are, it +is true, a few articles descriptive of tests of mental ability, but even +these are scarcely deserving of being classed as satisfactory +experimental studies of the psychology of the ape. I have the +satisfaction of being able to present in the present report the first +systematic experimental study of any feature of the behavior of an +anthropoid ape. + +Among the most interesting and valuable of the descriptions which may be +classed among accounts of tests of mental ability is Hobhouse's (1915) +study of the chimpanzee. The subject was an untrained animal, so far as +stated, of somewhat unsatisfactory condition because of timidity. +Nevertheless, Hobhouse was able to obtain from him numerous and +interesting responses to novel situations, some of which may be safely +accepted as evidences of ideation of a fairly high order. + +Similar in method and result to the work of Hobhouse is that of Haggerty +(unpublished thesis for the Doctorate of Philosophy, deposited in the +Library of Harvard University). Haggerty's tests of the ability of young +orang utans and chimpanzees to solve simple problems and to use tools in +various ways yielded results which contrast most strikingly with those +obtained in his experimental study of the imitative tendency in monkeys. +His observations, had he committed himself to anything approaching +interpretation, doubtless would have led him to conclusions concerning +the ideational life of these animals very similar to those of Hobhouse. + +Koehler, working in the Canary Islands, has, according to information +which I have received from him by letter, made certain experiments with +orang utans and chimpanzees similar to those of Hobhouse and Haggerty. +His results I am unable to report as I have scanty information +concerning them. They are, presumably, as yet unpublished. + +In his laboratory at Montecito, California, Hamilton has from time to +time kept anthropoid apes, but without special effort to investigate +their ideational behavior. He has most interesting and valuable data +concerning certain habits and instincts, all as yet unpublished. + +To a congress of psychologists Pfungst (1912) briefly reported on work +with anthropoid apes in certain of the German zooelogical gardens. His +preliminary paper does not enable one to make definite statements +concerning either his methods or such results as he may have obtained +concerning ideational behavior. So far as I know, he has not as yet +published further concerning his investigation. + +Moebius (1867) has described interesting observations concerning the +mental life of the chimpanzee. But this, like all of the work previously +mentioned, is rather in the nature of casual testing than thoroughgoing, +systematic, and analytic study. + +In addition to the above reports, there are a few concerning the +behavior of apes which have been especially trained for purposes of +exhibition. Most interesting of these is that of Witmer (1909), who +studied in exhibitions and in his own laboratory the behavior of the +chimpanzee Peter. The varied forms of intelligently adaptive behavior +exhibited by this ape convinced Witmer of ideational experience and even +of an approach to reasoning. In his brief report he expresses especial +interest in the possibility of educating this "genius among apes" to the +use of language. + +A chimpanzee named Consul was observed several years ago by Hirschlaff +(1905), and his tricks were interestingly described from the pedagogical +standpoint. + +Similar in character is Shepherd's (1915) brief description of the stage +behavior of Peter and Consul, both chimpanzees. It is impossible to +determine from the account whether these animals are the same as were +observed by both Witmer and Hirschlaff. As no reference is made in +Shepherd's paper to other descriptions of the behavior of these animals +and as he adds nothing to what had already been presented, the reader +obtains no additional light on ideation. + +I have mentioned only samples of the articles on trained anthropoids. +All are necessarily descriptions of the behavior of individuals who had +been trained not for psychological purposes but for the vaudeville +stage, and although such observations unquestionably have certain value +for comparative psychology, it is well known that unless an observer +knows the history of an act, he is not able to evaluate it in terms of +intelligence and is especially prone to overestimate its value as +evidence of ideation. + +There remain studies of the apes, dealing primarily with behavior and +mental characteristics, which are slightly if at all experimental and +deserve to be ranked as naturalistic accounts. Such is, for example, the +book of Sokolowski (1908), in which attention is given to the +characteristics of young as well as fairly mature specimens of the +gorilla, chimpanzee and orang utan. + +The various publications of Garner (1892, 1896, 1900) deal especially +with the language habits of monkeys and apes, but observations bearing +on ideation are reported. + +Wallace (1869) describes certain features of the behavior of an infant +orang utan whose mother he shot in Borneo. He also reports observations +concerning the behavior of adult orang utans, many specimens of which +were shot by him during his travels. + +Early in the last century, Cuvier (1810) interested himself in studies +of the intellectual characteristics of the orang utan, and his data, +taken with those of Wallace, Sokolowski, and others similarly interested +in the natural history of mind, give one a valuable glimpse of the life +of the anthropoid ape. + +Finally, the data brought together by Brehm (1864, 1875, 1888) in his +famous Tierleben; by Darwin (1859, 1871) in "The Origin of Species," and +other works, by Romanes (1900), especially in his books on mental +evolution, by C. Lloyd Morgan (1906) in his several works on comparative +psychology, and by Holmes (1911) in his discussion of the evolution of +intelligence, contribute not unimportantly to our all too meagre +knowledge of the mental life of the anthropoid apes. + +My own results, viewed in the light of what one may learn from the +literature, stand out as unique because of the method of research. Never +before, so far as I have been able to learn, has any ape been subjected +to observation under systematically controlled conditions for so long a +period as six months. Moreover, my multiple-choice method has the merit +of having yielded the first curve of learning for an anthropoid ape. +This fact is especially interesting when one considers the nature of the +particular curve. For so far as one may say by comparing it with the +curves for various learning processes exhibited by other mammals, it is +indicative of ideation of a high order, and possibly of reasoning. I do +not wish to exaggerate the importance of my results, for as contrasted +with what might be obtained by further study, and with what must be +obtained if we are adequately to describe the mind of the orang utan, +they are meager indeed. + +Especially noteworthy, as evidences of ideation, in the results yielded +by the multiple-choice method are (1) the use by the orang utan of +several different methods in connection with each problem; (2) the +suddenness of transition from method to method; (3) the final and +perfect solution of problem I without diminution of the initial errors; +(4) the dissociation of the act of turning in a circle from that of +standing in front of a particular box. + +To these features of behavior others of minor importance might be added. +But as they have been sufficiently emphasized in the foregoing detailed +descriptions, I need only repeat my conclusion, from the summation of +evidence, that this young orang utan exhibited numerous free ideas and +simple thought processes in connection with the multiple-choice +experiment. His ultimate failure to solve the second problem is +peculiarly interesting, although in the light of other features of his +behavior by no means indicative of inferior intelligence. + +The various supplementary experimental tests which I employed are in no +wise importantly distinguished from those used by other observers. The +box stacking experiment has, according to my private information, been +used by Koehler. It is obviously important that such tests be applied in +the same manner to individuals not only of the different genera of +anthropoid apes, but of different ages, sex, and condition of training. + +The box stacking experiment, although it yielded complete success only +as a result of suggestion on my part, proved far more interesting during +its progress than any other portion of my work. In connection with it, +the orang utan exhibited surprisingly diverse and numerous efforts to +meet the demands of the situation. It is fair to characterize him as +inventive, for of the several possible ways of obtaining the banana +which were evident to the experimenter, the ape voluntarily used all but +two or three, and one of these he subsequently used on the basis of +imitation. + +Had Julius been physically and mentally mature, my results would +undoubtedly have been much more impressively indicative of ideas, but +even as matters stand, the survey of my experimental records and +supplementary notes force me to conclude that as contrasted with the +monkeys and other mammals, the orang utan is capable of expressing free +ideas in considerable number and of using them in ways highly indicative +of thought processes, possibly even of the rational order. But +contrasted with that of man the ideational life of the orang utan seems +poverty stricken. Certainly in this respect Julius was not above the +level of the normal three-year-old child. + +In common with other observers, I have had the experience of being +profoundly impressed by the versatility of the ape, and however much I +might desire to disprove the presence of free ideas and simple reasoning +processes in the orang utan, I should feel bound to accept many of the +results of my tests as evidences of such experience. + +I have attempted to indicate briefly the historical setting of my +investigation. I propose, now, in the concluding section, to look +forward from this initial research and to indicate as well as I may in a +few words the possibilities of results important for mankind from the +thorough study of the monkeys and anthropoid apes. + + + +VII + +PROVISION FOR THE STUDY OF THE PRIMATES, AND ESPECIALLY THE MONKEYS AND +ANTHROPOID APES[1] + +[Footnote 1: Much of the material of this section was published +originally in _Science_ (Yerkes, 1916).] + + +I should neglect an important duty as well as waste an opportunity if in +this report I did not call attention to the status of our knowledge +concerning the monkeys and apes and present the urgent need of adequate +provision for the comparative study of all of the primates. + +Although for centuries students of nature have been keenly interested in +the various primates, the information which has been accumulated is +fragmentary and wholly inadequate for generally recognized scientific +and practical needs. There is a voluminous literature on many aspects of +the organization and lives of the monkeys and apes, but when one +searches in it for reasonably connected and complete descriptions of the +organisms from any biological angle, one, is certain to meet +disappointment. + +Concerning their external characteristics we know much; and our +classifications, if not satisfactory to all, are at least eminently +useful. But when one turns to the morphological sciences of anatomy, +histology, embryology, and pathology, one discovers great gaps, where +knowledge might reasonably be expected. Even gross anatomy has much to +gain from the careful, systematic examination of these organisms. With +still greater force this statement applies to the studies of finer +structural relations. Little is known concerning the embryological +development and life history of certain of the primates, and almost +nothing concerning their pathological anatomy. + +Clearly less satisfactory than our knowledge of structure is the status +of information concerning those functional processes which are the +special concern of physiology and pathology. Certain important +experimental studies have been made on the nervous system, but rarely +indeed have physiologists dealt systematically with the functions of +other systems of organs. There are almost no satisfactory physiological +descriptions of the monkeys, anthropoid apes, or lower primates. + + + +SUB-DIVISIONS OF THE ORDER PRIMATES + +_Order_ _Sub-orders_ _Families_ + + ,- a. PROSIMII (Lemurs and Aye-Ayes) + | + | ,- i. Hapalidae (Marmosets) + | | ii. Cebidae (Howling Monkeys, +PRIMATES -+ | Tee Tees, Squirrel Monkeys, + | | Spider Monkeys, and Capuchin + | | Monkeys) + `- b. ANTHROPOIDEA ... -+ iii. Cercopithecidae (Baboons + | and Macaques) + | iv. Simiidae (Gibbons, Orangs, + | Chimpanzees, and Gorillas) + `- v. Hominidae (Man) + + + + +When we turn to the science of genetics we meet a similar condition, for +the literature reveals only scattered bits of information concerning +heredity in the primates. No important experimental studies along +genetic lines have been made with them, and such general observations +from nature as are on record are of extremely uncertain value. Were one +to insist that we know nothing certainly concerning the relation of +heredity in other primates than man, the statement could not well be +disputed. + +Occasionally in recent years students of human diseases have employed +monkeys or apes for experimental tests, but aside from the isolated +results thus obtained, extremely little is known concerning the diseases +peculiar to the various types of infra-human primates or the significant +relations of their diseases to those of man. + +Next in order of extent to our morphological knowledge of these +organisms is that of their behavior, mental life, and social relations. +But certainly no one who is conversant with the behavioristic, +psychological and sociological literature could do otherwise than +emphasize its incompleteness and inadequacy. For our knowledge of +behavior has come mostly from naturalistic observation, scarcely at all +from experimentation; our knowledge of social relations is obviously +meager and of uncertain value; and finally, our knowledge of mind is +barely more than a collection of carelessly drawn inferences. + +This picture of the status of scientific work on the primates, although +not overdrawn, will doubtless surprise many readers, and even the +biologist may find himself wondering why we are so ignorant concerning +the lives of the organisms most nearly akin to us, and naturally of +deepest interest to us. The reasons are not far to seek. Most scientific +investigators are forced by circumstances to work with organisms which +are readily obtained and easily kept. The primates have neither of these +advantages, for many, if not most of them, are expensive to get and +either difficult or expensive to keep in good condition. Clearly, then, +our ignorance is due not to lack of appreciation of the scientific value +of primate research but instead to its difficultness and costliness. + +Strangely enough, the practical importance of knowledge of the primates +has seldom been dwelt upon even by those biologists who are especially +interested in it. It is, therefore, appropriate to emphasize the +strictly human value of the work for which I am seeking provision. + +During the past few years it has been abundantly and convincingly +demonstrated that knowledge of other organisms may aid directly in the +solution of many of the problems of experimental medicine, of +physiology, genetics, psychology, sociology, and economics. In the light +of these results, it is obviously desirable that all studies of +infrahuman organisms, but especially those of the various primates, +should be made to contribute to the solution of our human problems. + +To me it seems that thoroughgoing knowledge of the lives of the +infrahuman primates would inevitably make for human betterment. Through +the science of genetics, as advanced by experimental studies of the +monkeys and anthropoid apes, practical eugenic procedures should be more +safely based and our ability to predict organic phenomena greatly +increased. Similarly, intensive knowledge of the diseases of the other +primates in their relations to human diseases should contribute +importantly to human welfare. And finally, our careful studies of the +fundamental instincts, forms of habit formation, and social relations in +the monkeys and apes should lead to radical improvements in our +educational methods as well as in other forms of social service. + +Along theoretical lines, no less than practical, systematic research +with the primates should rapidly justify itself, for upon its results +must rest the most significant historical or genetic biological +descriptions. It is beyond doubt that genetic psychology can best be +advanced to-day by such work, and what is obviously true of this science +is not less true of all the biological sciences which take account of +the developmental or genetic relations of their events. + +In view of the probable values of increasingly complete accounts of +primate life, it seems far from extravagant to insist that the securing +of adequate provision for systematic and long continued research is the +most important task for our generation of biologists and the one which +we shall be least excusable for neglecting. Indeed, when one stops to +reflect concerning the situation, it seems almost incredible that the +task has not been accomplished. + +Some ten years ago Professor John B. Watson (1906) entered a plea for +the founding of a station for the experimental study of behavior. He +made no special mention of work with the monkeys and apes, but it is +clear from the problems which he enumerates that he would consider them +most important subjects for observation. Professor Watson's plea has +apparently been forgotten by American biologists, and it seems not +inappropriate to revive it at this time. For surely we have advanced +sufficiently along material and scientific lines during the last ten +years to render possible the realization of his hope. + +To my knowledge, only one definite attempt has thus far been made to +gain special provision for the study of the primates. Somewhere about +the year 1912 there was established on Tenerife, one of the Canary +Islands, a modest station for the study of the anthropoid apes. I have +already referred to it briefly on page 1. The plan and purpose of this +station, which is of German origin, have been presented briefly by +Rothmann (1912). From personal communications I know that a single +investigator has been in residence at the station since its founding and +that psychological and physiological results of value have been +obtained, but no published reports have come to my attention. + +When I first heard of the existence of the German anthropoid station I +naturally thought of the possibility of cooeperative work, but the events +of the past two years have rendered the chances of cooperation so remote +that it now seems wholly desirable and indeed imperative to seek the +establishment of an American station, which, unlike the German station, +shall provide adequately not only for the study of the anthropoid apes +but for that of all of the lower primates. It should be the function of +such a station or research institute (1) to bring together and correlate +all the information at present available; (2) to fill in existing gaps +observationally and thus complete and perfect our knowledge of these +organisms; (3) to seek to bring all available information to bear upon +the problems of human life. + +Hitherto the unsatisfactoriness of progress has been due to the lack of +a definite plan and program. Every investigator has gone his own way, +doing what little his personal means and opportunity rendered possible. +The time has at last come when concerted action seems feasible as well +as eminently desirable. I am therefore offering a plan and program +which, if wisely developed, should lead ultimately to fairly complete +and practically invaluable knowledge of the lives of all of the +primates. There should be provided in a suitable locality a station or +research institute which should offer adequate facilities (1) for the +maintenance of various types of primate in normal, healthy condition; +(2) for the successful breeding and rearing of the animals, generation +after generation; (3) for systematic and continuous observation under +reasonably natural conditions; (4) for experimental investigations from +every significant biological point of view; (5) for profitable +cooperation with existing biological institutes or departments of +research throughout the world. + +The station should be located in a region whose climate is highly +favorable to the life of many of the lower primates as well as to that +of man. Such a location is by no means easy to find. Because of my +intense interest in the subject, I have, during the past five years, +prospected in various parts of the world for a satisfactory site. I +shall now attempt to indicate the chief requirements and also the +foremost advantages and disadvantages of several regions which have been +considered. It is first of all requisite that the climate be such as to +agree with the organisms to be studied and such, also, as to render +their breeding normal and dependable. Second in importance is its +satisfactoriness for the life and scientific productiveness of the +observer. While certain tropical localities would meet the first +requirement perfectly, they would prove extremely unsatisfactory for +research activity. It therefore seems essential to find a region whose +climate shall reasonably meet the needs of the experimenter while +adequately meeting those of the animals to be studied. + +A further factor which has important bearing upon the productiveness of +the observer is the degree of isolation from civilization and from other +scientific work. No scientist can long work effectively, even in a +reasonably healthy and stimulating climate, if entirely cut off from +similar interests and activities. It is therefore desirable, if at all +possible, to discover a location in the midst of civilization and with +reasonably good opportunities for scientific associations. + +With these several desiderata before us, I shall call attention to a +number of possible sites for a station, several of which I have visited. +Southern California, and especially the portion of the State between +Santa Barbara and San Diego, promises fairly well. It is definitely +known that certain, if not all, species of monkey will breed there +fairly satisfactorily, and although it has not yet been demonstrated, +there is no reason to suppose that in certain regions the anthropoid +apes might not also be kept in perfect health and successfully bred. The +main advantages of this general region are (a) a climate which promises +to be reasonably satisfactory for many if not all of the primates; (b) +admirable climatic conditions for investigators; (c) wholly satisfactory +scientific and cultural environment for the staff of a station. The most +significant disadvantages are (a) a temperature, which is at times a +trifle too low for the comfort of certain of the monkeys and apes. It is +by no means certain, however, that they would not usually adapt +themselves to it. (b) The necessity of importing all of the animals and +of having to rely upon successful acclimatization. Of course it is to be +assumed that importation would be necessary only at the outset of such +work, since the animals later should replenish themselves within the +confines of the station. + +Florida offers possibilities somewhat similar to those of southern +California, but as I have not had opportunity to examine the conditions +myself, I can say only that in view of such information as is available +the advantage seems to be greatly in favor of the latter. + +Cuba, Jamaica, Porto Rico, and for that matter, several of the West +Indies, offer possible sites for a successful station. I have reasonably +intimate personal knowledge only of the conditions in Jamaica. The major +advantages in the West Indies are (a) suitable climatic conditions and +food supply for the animals; and (b) reasonably satisfactory climatic +conditions for the staff. These are, however, more than counterbalanced +in my opinion by the following serious disadvantages: (a) the relative +isolation of the investigators from their fellow scientists; (b) the +necessity of importing all of the animals originally used; (c) the risk +of destruction of the station by storms. + +It is definitely known that anthropoid apes as well as monkeys can be +successfully kept, bred, and reared in the West Indies. During the past +year, on the estate of Doha Rosalia Abreu, near Havana, Cuba, a +chimpanzee was born in captivity. A valuable account of this important +event and of the young ape has been published by Doctor Louis Montane +(1915). It therefore seems practically certain that regions could be +found readily on Jamaica, Porto Rico, or smaller islands, which would be +eminently satisfactory for the breeding of apes. + +There are obvious reasons why an American station for the study of the +primates should be located on territory controlled by the United States +Government, and if a tropical location proves necessary, it would +probably be difficult to find more satisfactory regions, aside from the +inconveniences and risk of importation and the relative isolation of the +investigators, than are available on Porto Rico. + +I have not seriously considered the possibility of locating an American +station on the continent of Africa, for although two of the most +interesting and important of the anthropoid apes, the gorilla and the +chimpanzee, are African forms, while many species of monkey are either +found there or could readily be imported, it has seemed to me that the +islands of the West and East Indies and the portions of the United +States referred to above are much to be preferred over anything +available in Africa. + +In the East, Borneo, the Philippine Islands, and Hawaii are well worth +considering. Borneo is the home of the gibbon and of at least one +species of orang utan, and in addition to these important assets, it +presents the advantages of (a) a wholly suitable climate and food supply +for monkeys and apes; and (b) climatic conditions for investigators +which, I am informed by scientific friends, are nearly ideal. For +investigators the most serious disadvantage here, as in all other parts +of the East, would be the isolation from other scientific work and +workers. + +The possibilities of Central America I considered several years ago when +it seemed to me possible that work might profitably be done with monkeys +and apes on the Canal Zone. The advantages are (a) a climate which +promises fairly well for the animals; and (b) reasonable accessibility +from the United States. The disadvantages are (a) a far from ideal +climate for long continued scientific work; and (b) an environment which +from the cultural and scientific point of view leaves much to be +desired. + +Were a permanent psycho-biological station for the study of the primates +to be established in southern California, it would, even though wholly +satisfactory conditions for the breeding, rearing, and studying of the +animals were maintained, furnish more or less inadequate opportunity for +the observation of the animals under free, natural conditions. It would +therefore be necessary, to supplement the work of such a station by +field work in Borneo, Sumatra, Africa, India, South America, and such +other regions as the species of organism under consideration happen to +inhabit. + +Considering equally the needs of the experimenter and the demands of the +animals, it seems to me reasonable to conclude that southern California +should be definitely proved unsuitable before a more distant site were +selected. For the information which I have been able to accumulate +convinces me that it would in all probability be possible successfully +to breed and keep the primates there, and it is perfectly clear that in +such event the output of a station would be enormously greater because +of the more favorable conditions for research than in any tropical +region or in a more isolated location. + +Assuming that satisfactory provision in the shape of a scientific +establishment for the study of the primates in their relations to man +were available, the following program might be followed: (1) Systematic +and continuous studies of important forms of individual behavior, of +social relations, and of mind; (2) experimental studies of physiological +processes, normal and pathological, and especially of the diseases of +the lower primates, in their relations to those of man; (3) studies of +heredity, embryology, and life history; (4) research in comparative +anatomy, including gross anatomy, histology, neurology, and pathological +anatomy. + +Each of these several kinds of research should be in progress almost +continuously in order that no materials or opportunities for observation +be needlessly wasted. Because of the nature of the work, it would be +necessary to provide, first of all, for those functional studies which +demand healthy and normally active organisms, whose life history is +intimately and completely known. This is true of all studies in +behavior, whether physiological, psychological, or sociological. +Simultaneously with behavioristic observations and often upon the same +individuals, genetic experiments might be conducted. This would be +extremely desirable because of the relatively long periods between +generations. After the usefulness of an animal in behavioristic or +genetic inquiries had been exhausted, it might be made to render still +further service to science in various experimental physiological, or +medical inquiries. And finally, the same individual might ultimately be +used for various forms of anatomical research. Thus, it is clear that +the scientific usefulness of a lemur, a monkey, or an ape might be +maintained at a high level throughout and even beyond the period of its +life history. + +The program thus briefly sketched would provide either directly or +indirectly for work on every aspect of primate life. Especially +important would be the intimacy of interest and cooperation among +investigators, for the comparative method should be applied consistently +and to the limit of its value. The results of various kinds of +observation should be correlated so that there should ultimately emerge +a unitary and practically valuable account of primate life, to replace +the patchwork of information which we now possess. + +Because of the costliness of maintaining and breeding the monkeys and +apes, it is especially desirable that the several kinds of research +mentioned above should be conducted. Indeed, it would seem inexcusably +wasteful to attempt to maintain a primate or anthropoid station for +psychological observations alone, or for any other narrowly limited +biological inquiry. + +Furthermore, the station should be permanent, since for many kinds of +work it would be essential to have intimate knowledge of the life +history and descent of an individual. With the lower primates, a +generation might be obtained in from two to five years; with the higher, +not more frequently, probably, than from ten to fifteen years. It +therefore seems not improbable that the value of the work done in such a +station would continue to increase for many years and would not reach +its maximum short of fifty or even one hundred years. + +A staff of several highly trained and experienced biologists would be +needed. The following organization is suggested as desirable, although, +as indicated below, not necessarily essential in the beginning: (1) An +expert especially interested in the problems of behavior, psychology, +and sociology, with keen appreciation of practical as well as of +theoretical problems; (2) an assistant trained especially in comparative +physiology; (3) an expert in genetics and experimental zoology; (4) an +assistant with training and interests in comparative anatomy, histology, +and embryology; (5) an expert in experimental medicine, who could +conduct and direct studies of the diseases of man as well as of the +lower primates and of measures for their control; (6) an assistant +trained especially in pathology and neurology. + +To this scientific staff of six highly trained individuals there should +be added a business manager, a clerical force of three individuals, a +skilled mechanician, a carpenter, and at least four laborers. + +The annual expenditures of an institute with such a working staff, would +in southern California, approximate fifty thousand dollars. It would +therefore be necessary that it have an endowment of approximately one +million dollars. + +In the absence of this foundation it would, of course, be possible to +make a reasonably satisfactory beginning on the work which has been +outlined in the following less expensive manner. A working plant might +be established, on ground rented or purchased at a low figure, for about +ten thousand dollars; the salary of a director, assistants, a clerical +helper, and combined mechanic and laborer might be estimated at the same +figure; the cost of animals and of maintenance of the plant would +approximate five thousand dollars. Thus, we should obtain as an estimate +of the expenditures for the first year twenty-five thousand dollars. +Without expansion, the work might be conducted during the second year +for fifteen thousand dollars, and subsequently it might be curtailed or +expanded, resources permitting, according as results achieved and in +prospect justified. + +An institute established on such a modest basis as this still might +render largely important scientific service through its own research and +through organized cooperation with other existing research +establishments. Thus, for example, supposing that behavioristic, +psychological, sociological, and genetic inquiries were conducted in the +institute itself, animals might be supplied on a mutually satisfactory +basis to institutes for experimental medicine, for physiological +research, and for anatomical studies. Under such conditions, it is +conceivable that extremely economical and good use might be made of all +the available primate materials. But it is not improbable that even +cooeperative research would prove on the whole more profitable, except +possibly in the case of morphological work, if investigators could +conduct their studies in the institute itself rather than in distant +laboratories. In any event, the idea of cooeperation should be prominent +in connection with the organization of a research station for the study +of the primates. For thus, evidently, scientific achievement in +connection with these important types of animal might be vastly +increased over what would be possible in a single relatively small +institution with a limited and necessarily specialized staff of workers. + +Despite the fact that biologists generally recognize the importance of +the work under consideration and are eager to have it done, it is +perfectly certain that we shall accomplish nothing unless we devote +ourselves confidently, determinedly and unitedly, with faith, vision, +and enthusiasm, to the realization of a definite plan. Our vision is +clear,--if we are to gather and place at the service of mankind adequate +comparative knowledge of the life of the primates and if we are to make +this possible harvest of scientific results count for human betterment, +we must bend all our efforts to the establishment of a station or +institute for research. + + + +VIII + +BIBLIOGRAPHY + + + +BREHM, A. 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