Chapter 6 GENESIS OF THE REACTION OF THE HORSE

In the preceding discussion we have regarded the achievements of the horse as well as Mr. von Osten's explanation of them, as matters of fact. Let us now consider the question: How did the horse come by these achievements, and how did its master arrive at his curious theory in explanation of them? Did he indeed seek to instill in the horse's mind the rudiments of human culture through long years of painstaking instruction in accordance with the method described in Supplement I (page 245)? If that is the case, then, of course his hoped-for success was only seeming, not real.

Or did he, as so many critics aver, systematically train the horse to respond automatically to certain cues, and propound his theory merely for the purpose of misleading the public? There might possibly be another alternative, viz.: was there a mixture of instruction and of training to respond to cues?

The production of the horse's achievements would not require a great deal of explanation, if it were a case of mere training for the purpose of establishing certain responses to certain cues. It might be desirable, however, before deciding in favor of one of these possibilities, to indicate briefly the process of development, as it might occur, if the point of view is taken that bona fide instruction was given.

This development would probably be as follows:-Mr. von Osten, as the result of theoretical speculation or of a misinterpretation of the facts of experience, having arrived at the conclusion that the horse possessed extraordinary capacity, finally undertook to instruct a certain horse for a period covering three years. This one having died, he, nothing daunted, undertook the education of another one. What it was that influenced this old teacher of mathematics to deprive humankind of the benefit of his extraordinary pedagogical ability and love of teaching, we do not know. It may be that he had had bitter experience in that line, or again, mayhap the newness and tremendousness of this other task stimulated him. His first problem must have been to arouse the interest of the animal in this process of education. It was hardly to be believed that Hans would eagerly co?perate in a process which promised to yield him no immediate benefit. The teacher sought to overcome this lack of immediate interest by the means of rewards. To Hans the sweet carrot was as toothsome a bite as candy is to the child. And since the horse was furthermore kept on low rations on account of the relatively low amount of physical exercise he took, the anticipation of the carrots was doubly enticing.

The first thing that Mr. von Osten sought to teach the horse, according to his own statement, was the significance of the names of colors and of the spatial directions such as "up", "down", etc. In the case of children there is a simple test by means of which we may discover if they have put any content into these words. The test is: Do they, themselves, use them correctly? Do they call the blue, blue, and the red, red? Since the horse could not speak, his instructor had to give him some means by which he could make himself understood. He taught Hans to approach the colors and select the cloth of the color wanted. He also taught him to make those movements of the head or body which correspond with the expressions: "up", "down", etc.

First of all, Hans had to be taught to bring the cloths. Then began the pointing out of the different colors, accompanied each time by their proper names. It is very probable that at first Hans had to be led each time to each separate colored cloth and taught to raise it or to touch it with his nose. Later, Mr. von Osten, after having pronounced the name of the color, remained at his place, with his head and body directed to the cloth in question and gazing intently at it, in order to see whether or not the horse was pointing out the right one. Naturally Hans would, at first, fail a hundred times where he would succeed but once, but since the horse would receive the anticipated reward in case of success, he gradually became conscious that this reward was attached to executions which had some special mark. This special mark would be expressed in human speech by the statement that the horse would go in the direction indicated by the position of the instructor's body. For Hans, of course, this would not take the form of an abstract statement, but simply of a definite way of seeing and of going and a correlation of the two in a certain definite manner,-the whole being a process, the elements of which remained unanalyzed and unaccounted for by Hans. Owing to the position of the eye, it was possible for him to keep his master within his field of vision, while he was approaching the cloths. And only when he had correlated his approach in a certain definite manner with his visual perception of the master, i. e., only when he had felt his way, as it were, along the latter's line of vision, did he receive his reward. A sufficient number of repetitions was all that was necessary to establish an association in the psychological sense of the term. In the same manner, dogs will learn, as was indicated on page 177, to bring an object upon which the master has fixed his gaze, it mattering little whether or not the name of the object be enunciated. There is only this difference, that, in the case of the dog it is not possible to keep the image of the master within the field of vision; but neither is it necessary, for he has recognized the object before he has started for it. We must remember, however, that it does not simplify an attempt at explanation to assume that Mr. von Osten consciously trained the animal to respond to certain bodily positions of the questioner. For, even in this case, it would be necessary to explain how it was possible for him to train the horse to heed the cues.-In the course of time, the instructor may have noticed that whenever he moved during the course of a test the horse invariably failed. But he may have regarded this merely as an incidental distraction and afterward was careful to remain quiet. As soon as he increased the number of cloths upon the floor, it was no longer possible for him to give the horse such accurate directive signs, and the number of errors consequently increased. Ascribing them to the inattentiveness of his pupil, he sought to encourage him by such calls as "look out", "look there", "see there", believing that, thus, he was directing the horse's attention to the desired color. Without understanding the meaning of the calls, Hans learned, however, to keep moving just as long as the calling continued, for if he did this he was regularly rewarded. An association was established between the call and the impulse to move on. And with these two associations established, Hans gave the impression of having grasped the meaning of the color terms.

The origin of the proper movements in response to the terms "up" and "down" may be explained by the fact that the movements themselves were practised in a purely external fashion. Thus, whenever the word "left" was pronounced, the horse's head was pulled to the left by means of the bridle or the reward was held off to that side. Later, Mr. von Osten, who looked expectantly at the horse's head, whenever he pronounced the word would unconsciously move his own head in the direction in which he desired the horse to turn. This is quite in accord with the words of Darwin to the effect that whenever we wish an object to move in a certain direction it is well-nigh impossible for us to inhibit an unconscious, involuntary movement in that direction. Proof for this may be found on all sides, in daily experience.[97] Imagine, for instance, the strain sensations of the bowler or billiard player as he follows the moving ball. It is impossible to decide whether Mr. von Osten, consciously continued to image the head movements which he expected the horse to make or whether these anticipatory images later remained below the threshold as was always the case with Mr. Schillings and myself (see page 100). But this question is of little significance, for even assuming that he always thought of the movement he expected on the part of the horse, this by no means implies that he was conscious of the movements on his part, which were associated with the thought process.

Everything up to this point might be explained as the working of simple memory association, but when we come to problems in counting and arithmetical calculation, we are in the field of conceptual thought. Here, again, it was necessary for Mr. von Osten to invent a suitable means of expression for the horse, and once more this had to be borrowed from the treasury of gesture-language. Tapping with the hoof was naturally hit upon as one of the normal, expressive movements of the horse. This has long been used by trainers, in preparing horses for show purposes. The method used in training the horse to make this response is of no import, whether it was by touching his foot with the hand, or tapping his leg, or by any other means.

It is possible that many will declare, as being nonsensical, any attempt to introduce number-concepts[AJ] into an animal's mind, because the necessary motor basis is lacking. We will not, just at this point, stop to discuss whether or not it was not possible to develop number-concepts from purely auditory or visual representations. It is evident, however, that Mr. von Osten believed that a motor basis of some sort was essential. In the case of man this basis is found in the enunciation of the number names (or in the manipulation of the fingers). Mr. von Osten seemed to think that he was justified in assuming that, even in the case of the horse, some form of inner articulation of the word-sounds was possible;-at the same time, in so doing, he did not blink at the psychological difficulty of this hypothesis. The tapping of the foot was to be regarded merely as the expression of the process of inner counting, but not as the motor basis of the process. For this latter purpose tapping would be quite inadequate, for the number complexes which arise in the summation process of counting, could not be differentiated by mere tapping with the foot, any more than a child could learn to count by employing only one finger. Mr. von Osten evidently imagined the process was somewhat like this: Whenever Hans was about to count 5, he would enunciate inwardly the numbers from 1 to 5, and would accompany each word with a tap of the foot. Since, furthermore, wooden pins and balls could be used-as in the case of children-for giving visual content in learning the significance of the number-terms, it seemed as if all the conditions necessary for the formation of number-concepts were supplied. However, the most essential thing had to be presupposed, viz.: that the horse virtually possessed the general power of forming concepts,[AK] and that all that had been lacking was the suitable conditions for its development. Mr. von Osten held tenaciously to this conviction, and it was this conviction that was the basis for the infinite patience with which the tests had been pursued.

To come now to the learning process itself;-we may assume that, at first, whenever the horse began to tap in response to commands, he would receive a reward for this purely mechanical feat. Wooden pins were then planted on the ground and designated as: one, one two, etc., and each time someone would raise the horse's foot as many times as the count demanded (see Supplement I). Then Mr. von Osten would take his stand at the horse's side and would command him, let us say, to tap 3. Hans noting merely (from his master's position) that he was expected to tap, would begin. The instructor, who had bent forward in order to watch the horse tapping,[AL] would involuntarily straighten up again at the third tap, without being conscious of it and quite unaware that he was thus giving a signal. The horse would be startled, and sometimes he would immediately cease tapping and sometimes not. But it was only in the first case that he would receive a reward. Thus, unknown to the instructor, an association became established between the sight of the upward jerk of the instructor and the act of ceasing to tap. To be sure, the animal would receive sundry visual impressions from the wooden pins set up before him and the auditory stimulations of the spoken number names, on the basis of which, the concepts were to be formed in his mind. But in this chaos of visual impressions (at times there were two wooden pins, then three, then four, sometimes there were the pins, at others, the balls of the counting-machine)-and in the babel of word-sounds-which evidently meant nothing but noise to him-amidst all this there was but one constant element: the final movement of the instructor's body. The moment the horse reacted to this, he would receive the tidbit at the hands of his overjoyed master, and thus he became more and more accustomed to attend to this jerk, even after it had gradually decreased in scope. And the reason again, why this jerk tended to become less pronounced was that the tests were gradually becoming more and more successful. For, corresponding to the degree in which the horse began to react properly, the instructor's tenseness and excitement tended to decrease, and with this decrease of the emotional element in the man's consciousness, the accompanying non-voluntary, expressive movement gradually became less pronounced until it attained that extraordinary refinement which it possesses to-day. We noticed also, that whenever the horse, for any reason, had to be trained anew, Mr. von Osten's movements would, on the whole, become somewhat more gross, as for instance after the tests with the blinders. There is not a shadow of a doubt that this increase in the movement's extent was entirely unintentional, since the horse could not see his master at all on account of the blinders which had been attached to the trappings.

In the same way it is possible to explain the details. Mr. von Osten himself said that at first Hans had tapped at times with his left foot, at times with his right, just as he pleased. But later his master taught him to tap only with the right. Whenever he began with the left, Mr. von Osten would immediately interrupt him, and he was allowed to add only a final tap with his left foot. Thus, this additional tap which was sometimes made with the left foot was but the vestige of an earlier rudimentary habit. The signal for it was the stooping posture in which the master remained after the head-jerk had been made. Whenever Mr. von Osten had given Hans a small number to tap, he would bend forward only a little. But when he expected a larger number he would bend forward somewhat more, owing to the desire to observe the tapping more carefully. From the slight inclination of the master's body the horse would get the cue that he was expected to tap for a short time only, by the greater degree of inclination he would know that he was to tap for a longer period. In the second case he tapped rapidly and did not raise his foot as high from the ground-evincing a regard for the saving of energy, which may well be attributed to a horse. And thus arose the connection between the degree of inclination of the instructor's body and the horse's rate of tapping.

So, now that the ability to count and solve problems had become fixed-as the old gentleman thought-he began to instruct the horse in other branches. Since everything had been translated into terms which were to be expressed by means of tapping with the foot, and thus really put into terms of number-which was perhaps natural for an old teacher of mathematics-the same mechanism was involved in these accomplishments as in those of counting, etc. Mr. von Osten saw the animal's intelligence steadily increase, without having the slightest notion that between his words and the responsive movements of the horse, there were interpolated his own unconscious movements-and that thus instead of the much desired intellectual feats on the part of the horse, there was merely a motor reaction to a purely sensory stimulus. It has been a common custom of man to posit some extraneous cause for movements resulting from certain involuntary motions of his own, of which he is not aware, (witness the divining-rod).[AM] And furthermore, when these results appear to be rational, the tendency is to seek their cause in some extraneous intelligence, not his own. Just as the spiritualists ascribe the "messages" which are revealed to them through table-rapping, to certain rational spirits, so Mr. von Osten credited the intelligence of the horse with the result produced by his own involuntary signs-i. e., with the proper solution of problems.

Two other phenomena may have tended to strengthen Mr. von Osten's belief in Hans's intelligence. One was the misleading similarity with which the horse's supposed errors in computation and the poorly adjusted concentration of the questioner, were expressed. We recall the difficulty in the case of very high numbers. This might easily be considered as being due to the horse's ability to work more readily with small, rather than with large numbers, whereas, as a matter of fact, it was due solely to the difficulty of the questioner to keep his attention concentrated upon the number for so long a time. We recall also the frequency of errors of one unit too few and one unit too many. These were easily interpreted as miscounts on the part of Hans, but in truth were the result of the poorly concentrated attention of the questioner. Added to this was the seeming independence and self-sufficiency of the horse. Often the number given by him was other than that desired by his master. Usually Hans was in the wrong in such cases, but sometimes, too, he was right. At any rate, this served to give the impression of independence of thought which his master so thoroughly believed he possessed, and which was the goal of his endeavors-though as a matter of fact he was farther removed than ever from that goal.

Some may ask: Does not this whole process partake of the essentials of all training, (though cumbersome and misunderstood, to be sure), and is there any need of investigating whether or not the actual development was of the sort here outlined, or whether it actually took the course common to all training?

In order to answer this question we must determine more specifically what we mean by the term "training". Usually we take it to mean the establishment in the animal, of definite habits of motor reaction in response to certain stimuli purposely selected by the trainer, and without involving any process of animal consciousness other than association. Such a conception may be applied also to man, if we assume that the higher thought processes can be eliminated. If that were the case, the above definition would not have to be changed, not even with regard to the word "animal", for we must take it in the antique sense of "zoon", a signification readopted by modern zoology. The concept may be widened, however, by omitting the differentia of "purpose", or even more, by including the habitual association of ideas or images (instead of movements) with certain sensory stimuli. But in so doing, we must bear in mind that we are going beyond the usual content which in everyday practice is put into the term "training". Especially, when we cease to regard the presence of purpose in the trainer's mind (both in giving the stimulus as well as in the habituation of the animal to them) as essential. When this is done, the conception of training really resolves itself into the much wider conception of habit-building, and the whole discussion becomes merely a quarrel over words. In order to obviate this, let us bear in mind that in the following, the word "training" is always taken in the usual and narrower sense. The term then is still ambiguous only in so far as it has not merely its original significance of the act of purposely habituating (a person or an animal) to perform certain definite movements, but by transference is also used to denote the effect, i. e., the occurrence of the movements in question. But this does not really detract from the clearness of the concept itself.

Having cleared up the question of definition, let us return to our original problem: Does the hypothetical account of the probable development of the horse's reactions, which is given on pages 213 to 220, represent a case of training? This must be denied decidedly with regard to the tapping of numbers and the solution of arithmetical problems. For here the sensory stimuli which were purposely given, i. e., the wooden pins, the balls, and the spoken words, were intended to subserve the function of arousing not movement, but thought processes in the horse; whereas the function of the horse's movements was to give expression to these thought processes. Of the really effective stimuli-the slight movements on his part-the master was never conscious, much less were they purposely made. The same holds true for the "up" and "down", "yes" and "no", etc., for here also Mr. von Osten counted upon the rise of the corresponding concepts, and not merely upon a purely external, mechanical association of meaningless sounds with certain movement-responses on the part of the horse. This might also explain the genesis of Mr. von Osten's belief that Hans was able mentally to put himself in the place of the questioner, (page 19). At any rate it is very improbable that he, Mr. von Osten himself, clearly distinguished between the concept: "up" and the sound of the word "up". When we come to consider the horse's selection of the colored cloths, and even more his leaping and rearing, we find that the distinction between "training" and "instruction" vanishes. If we had to deal only with this class of achievements, we might perhaps say, without fear of going very far wrong, that the only difference between this and the ordinary form of training was that Mr. von Osten had intended to train the horse to respond to auditory signs (words), but had unintentionally trained him to respond to visual signs instead. But it is not this type of performance that has become the bone of contention. Just as it would be misleading to maintain that Mr. von Osten's effort was nothing other than a case of training, so it also would be unjustifiable to designate the results of his effort by that name, since the really effective stimuli were not, as has been pointed out just now, given intentionally.

As far as the horse is concerned, it is a matter of indifference whether or not really effective stimuli were given intentionally by the questioner. The animal knows nothing of human purposes and if he were transferred to a circus, he would find nothing new in the method employed there, except the use of the whip. We, however, define our concepts from the human and not from the horse's point of view. We may definitely say, therefore, that the method described cannot be regarded as that of training, neither in its application nor in the effect produced, though in the latter it closely simulates the effects of the training method.

Having thus differentiated between the methods of instruction and training, let us now attempt to decide on the basis of such indications as we may possess, which of the two was actually represented by the development of the horse's attainments. Surveying the facts which we have at hand, we may say that there are hosts of reasons why we cannot assume that it was a case of training. Everything that we know from our own observation and from the well-attested statements of others, with regard to the actual process of instruction, weighs against the assumption. Another evidence of this is the long period of time which Mr. von Osten required (both in the case of Hans, as well as with his predecessor), whereas the same end would have been much more speedily attained if it had been a case of training. A further argument is the fact that a large horse was selected for the purpose, whereas a small mare would have been far more suitable, (c. f., "Clever Rosa", page 7). Again, the whip, that sorcerer's rod of all professional trainers, was here absent. And finally, many traits of character of Mr. von Osten, as well as his conduct during the whole course of events, militate against such an assumption. He generously turned the horse over to us, as he had given it over to Count zu Castell, Count Matuschka and Mr. Schillings. He eagerly besought a scientific investigation. He had made several reports to different ministries. All of these acts could only hasten the denouément. What could have been his motive? Some thought they detected an effort at pecuniary speculation, and an advertisement of June, 1902, in the "Milit?rwochenblatt", in which Hans was offered for sale, seemed to confirm the conjecture. Mr. von Osten says that this occurred at a time when he himself was sick and had become tired of the job. And why should he not be willing to sell even a thinking horse, since he had become convinced that any other could be instructed in the same way? Besides, I have it on good authority that after the publication of the September report he received several exorbitant offers; to mention only one of them: a local vaudeville company was ready to pay him 30,000 to 60,000 marks per month. He refused every one of these offers. Some may say that perhaps he wanted still more. But if he knew that the day of judgment was close at hand, he also knew that before then, if ever, was the sunshiny day on which to make his hay. A more auspicious time he could never hope to see again.-Let us add, once more, that he never charged admission to any of Hans's performances, although there were many who were anxious to see the horse, and many enthusiasts had come from a great distance. And finally, he was an old man, unmarried and entirely alone, a property owner, but a man whose wants were few and very simple-and his Hans was almost his sole companion. Is it possible that such a man, one who had all the pride of gentle birth, would become a trickster in his old age, all for the love of money?

The unreliability of Mr. von Osten's signs is good proof of their involuntary nature. Anyone who had seen him work with the horse could not have helped noticing that he certainly did not have complete control over the animal, and was not able, at a given moment, to make Hans perform a certain feat, as would have been the case if the process had been one of "training". Again and again Hans failed to make the right count. Before a large audience, one time, it took four tests to get him to tap properly up to 20, and in all four I could note clearly that it was Mr. von Osten who, by his involuntary premature movements, was the innocent cause of the failure. On another occasion, after Hans had done some beautiful work in fractions, in the presence of a large number of spectators, the master asked him the simple question: "Where is the numerator in a fraction?"-The answer was first: "to the left", and then, after a severe reprimand: "down" (below), and finally: "up" (above). He often made just such incorrect movements of the head. In the color-selecting tests the average of error was quite unpredictable. With an equal number of tests, on one day, half would be successful, on another, four fifths, on a third, one-tenth. Often Hans appeared to be "indisposed" for days at a time. The color tests would often end in expressions of rage on the part of Mr. von Osten and in consequence Hans would become startled and would then storm about the courtyard so that it was dangerous to try to approach him. Some may object that all this was mere comedy and that possibly Mr. von Osten prevented some of the tests from turning out successfully. But this objection is to be met by the statement that very often failure would occur just when it was particularly desirable to have the tests appear in a favorable light before a large and enthusiastic assemblage of visitors. After such failures he would be downcast on account of Hans's contrariness. It is also significant that Mr. von Osten's percentage of error, corresponds very closely with my percentage of error in the "non-voluntary" tests, (page 84f.), whereas he never was able to obtain the errorless results which I obtained in my "voluntary" experiments.

But we must be careful not to confuse non-voluntary movement and lack of knowledge of the movement. And again we must distinguish between knowledge of the grosser and the finer signals. Mr. von Osten was aware of the grosser movements, and talked quite freely concerning them, but in so doing, showed that he was quite unaware of their true function. He undertook to show us what we already knew-that, when he remained standing perfectly erect, he could elicit no sort of response from Hans. Furthermore, that whenever he continued to bend forward, Hans would always respond incorrectly and with very high numbers. He knew, also, that Hans was distracted in his operations every time the questioner resumed the erect posture while the tapping was in progress. This he demonstrated to us on one occasion in the following manner. He said to Hans: "You are to count to 7; I will stand erect at 5". He repeated the test five times, and each time Hans stopped tapping when the master raised his body. Several such tests resulted in the same way. Mr. von Osten, however, believed this to be a caprice of the horse and at first declared that he would yet be able to eliminate it, but later became resigned to it as an irremediable evil. Mr. von Osten was also aware that the questioner ought not move while the horse was approaching a colored cloth, and cautioned me in regard to it, though I had already noted as much. And finally, he also knew what influence his calls had while the horse was selecting the cloth, and he told me that it was of great assistance to Hans to be admonished frequently, since thus his attention was brought to bear upon the proper cloth. Yet, when we requested Mr. von Osten to desist calling, since he was thereby influencing the horse in the choice of the cloth, he answered: "Why that's just what I wish to do!"-But though the statement that he was aware of the nature of these grosser signs is thus seen to be true, it by no means necessarily implies that he had purposely trained the animal to respond to them. In these observations of his he had builded better than he knew-he evidently had no notion of their scientific significance. But the same thing might happen to those who were supposed to be somewhat less na?ve, as is shown by the experience of Mr. Schillings, who quite unconsciously, for many months had been giving not only the finer, but also the grosser signs, and never guessed the true nature of affairs until I explained it to him. Nor was it an easy matter for me to get at the facts involved in the process, although it now all appears so very simple.

On the other hand, it is also true that Mr. von Osten knew nothing whatever of the finer, more minute signals, such as the final jerk, the head-movement upward, downward, etc., and it is difficult to conceive how he might have gained any knowledge of them. We might perhaps conceive of four possible sources. He might have come upon them by chance. But it is extremely improbable that in the million of possible forms of signaling he should have hit upon those that at the same time represent the natural expressive movements. Or he might have derived a knowledge of them through a study of the pertinent literature. I have searched diligently for such a source, in both the old and the modern literature, but in vain. From the sixteenth century on, there is a series of accounts of horses that were able to spell and to solve problems in arithmetic, and the reports on learned dogs go back even to the time of Justinian, in the middle of the sixth century.[107] All of these animals were kept for purpose of speculation and were exhibited for pecuniary reasons only. Nor does one read that any person could work with these animals off-hand, which was the characteristic feature of the Osten horse.[AN] In many cases we find mention made of the signs to which the animals reacted. Thus for the beginning or stopping of the animal's scraping or tapping, the signals were respectively raising and lowering of the eyes on the part of the trainer,[113] lowering and raising of the whip[114] or of the arm, stepping forward and backward,[115] and as a closing signal a slight bending forward.[116] The signals for beginning and ceasing to bark in the case of dogs, were the trainer's commands to "speak", and, at the same time, his looking at the dog, and then looking away for a closing sign;[117] or a mouth-movement on the part of the trainer and then a withdrawing of the left hand which had been resting on the hip.[118] Among the signals for nodding and shaking the head we find the following mentioned: raising and lowering the hand or arm[119] or the whip;[120] a movement of the hand toward the horse's nose, as a signal for nodding, and an arm-movement as a signal for shaking the head.[121] For this last, we find recommended also a slight breathing upon the animal,[122] and-in the case of dogs-a mouth-movement simulating blowing, or a turn of the fingers.[123] (We will not dwell upon the many signals for selecting objects, which are mentioned, since we have already discussed this point on page 230f). In all these instances it is plain that we have to do with purely voluntary and "artificial" signals. The only example of involuntary signs which Mr. von Osten could have found in literature, was that of Huggins's dog, which need not be considered here, since, as was said on page 177, the really effective signs in that case were not discovered. A third means by which Mr. von Osten might have gained a knowledge of the involuntary, natural expressive signs, would have been by observing others. If he had had opportunity of observing another von Osten and another Hans, he might have gotten at the secret. But since this was not the case, this possibility vanishes. A fourth possibility is self-observation. We would then have to assume that Mr. von Osten at first really tried to educate the horse to think, but soon recognized the fruitlessness of such an attempt. At the same time, he then would have noticed his own involuntary movements and their effect upon the horse, and having noted them, voluntarily reduced their extent and utilized them in the training process. But here also there is much that militates against this assumption when we consider how great is the difficulty of consciously refining movements which at first were rather coarse, unless it be by the adjustment of the proper degree of concentration of attention, a subtlety of method of which we could hardly believed Mr. von Osten capable. We must remember, also, that in the first publication regarding Hans which, by the way, marks the beginning of his career, ("Das lesende und rechnende Pferd," by Major-General E. Zobel, in the "Weltspiegel" of July 7, 1904), we may read the following: "He (Mr. von Osten) is always willing to have the horse undergo an examination on the part of a stranger, and promises that after Hans has become fairly well acquainted he will display the same degree of efficiency as he displays with the master, himself." This occurred at a time when Mr. Schillings, the man who was destined to prove the truth of the statement, had not yet appeared on the scene. How was Mr. von Osten to know beforehand that every questioner, who might appear, would execute the same movements that he himself had used? We would recall also that not one in the great multitude of persons who worked successfully with the horse in the absence of Mr. von Osten, had noticed, even in the slightest measure, any of these movements in themselves. The position and repute of these persons vouches for their veracity,-among them were the writer of the article just mentioned, the Count zu Castell, Count Matuschka, Count von Eickstedt-Peterswaldt, General K?ring, Dr. Sander, Mr. H. Suermondt and Mr. H. von Tepper-Laski. Some of these gentlemen were quite unwilling to believe that they executed such movements. This happened in the case of Mr. von Tepper-Laski, who had visited Hans ten times and who had, during the course of these visits, frequently worked alone with the horse and had received correct responses. Count Eickstedt, too, although he was one of those who had been made acquainted with the nature of the movements involved before being allowed to visit the horse, was unable to note them either in his observation of Mr. von Osten, or of himself, when, in compliance with his own wish, he was left alone with Hans. Nor did any of the laboratory subjects, some of whom were well trained in introspection, discover the true nature of affairs. They were thoroughly astonished when the facts of the case were explained to them. And I, also, as was mentioned on page 100, did not become aware of my own movements, until I had noted those of Mr. von Osten. In fine, everything would indicate that we have here not an intention to deceive the public, but a case of pure self-deception.[AO]

This self-deception is easily understood when we consider the two predominent characteristics of the man: the pedantry of the pedagogue, and his proneness to be possessed by a single idea, which is a peculiarity of those of an inventive turn of mind. Adhering closely to a preformed plan, he carefully and narrowly circumscribed the scope and order of instruction. He would not go on to the number 5 if he were not thoroughly convinced that the 4 had been completely mastered, nor would he go on to a more difficult problem in multiplication, until he felt certain that Hans was entirely proficient in the problems of the simpler sort. If he had ever put a question to Hans before its regular order, he would have discovered, to his amazement, that there really existed no difficulties for Hans, and also that the horse really required no appreciable time to acquire new material. Mr. von Osten would have had a like experience if he had asked Hans concerning the value of Chinese coins or the logarithm of 1000. However, he never did anything of the kind, but always adhered closely to his plan. He required the questioner to say: "2 and 2", and never "2 plus 2". Nor were capitals or Latin script to be used in the written material. And if upon request he did so, he did it, without faith in the result, and hence there was failure. And so he declared that "if you use Latin script Hans becomes confused and will be out of sorts for several weeks thereafter." Mr. von Osten is, and ever will remain, the schoolmaster, and will never become the psychologist, the "soul-vivisectionist". Who would work a child with such puzzling questions? and Hans was to him like a child. Thus the old man believed himself to be a witness of a continuous, organic development of the animal soul-a development which in reality had no other existence than in his own imagination.

Added to this pedantry was an extraordinary uncritical attitude of mind, induced by his obsession by one favorite idea, which blinded him to all objections. He met objectionable observations on the part of others in one of two ways. One method was by attributing to Hans certain remarkable qualities, such as an extraordinary keenness of hearing and a wonderful power of memory, or again, certain defects, such as moodiness and stubbornness,-which as a matter of fact, were only so many back-doors by which he might escape from the necessity of offering adequate explanations. When Hans was able to give off-hand a gentleman's name which he had heard years before, it was called a case of extraordinary memory. When the horse insisted that 2 times 2 was 5, he maintained that it was an example of animal stubbornness. There was still a simpler method of overcoming inconvenient objections and that was by ignoring them altogether. The number 1, the simplest and most fundamental in the system of numbers, was one of the most difficult for Hans. (Page 67f.). Mr. von Osten was aware of this, but thought little of it. During the very first visit of Professor Stumpf, Mr. von Osten asked the horse: "By how much must you increase the numerator of the fraction 7/8, in order to get a whole number?" Hans repeatedly answered incorrectly and always tapped numbers that were too great. The same question was then asked concerning the fraction 5/8, and immediately there was a correct response, (the favorite number 3). Mr. von Osten said very na?vely: "In the case of the difference of 1, he always goes wrong. It was just what I expected." Mr. von Osten still relates that the distinction between right and left created far greater difficulty for Hans than all of the work in fractions, and that even to-day it is not thoroughly established; also, that the selection of colored cloths is often a failure still, although it was one of the first things in which he was given instruction. It appears never to have dawned upon Mr. von Osten that the arts in which Hans seemed to excel, also formed the standing repertoire of so many trained horses, regarding whom it was well-known that they owed all of their cleverness to the training given them by their masters. This fact alone should have induced him to make some form of critical investigation.

When Hans suddenly became a celebrity, and he, himself, the object of an enthusiastic following, the whole affair evidently took Mr. von Osten off his feet. Strangers took the further instruction of the horse in charge, and the rate and degree of Hans's progress became disconcerting. One day it came to pass that the horse even understood French, and the old gentleman, whose apostolic exterior had always exerted a high degree of suggestion upon his admirers, in turn fell captive to the spell of retroactive mass-suggestion. He no longer was uneasy concerning the most glaring kinds of failure. On one occasion he even insisted upon the completion of a series of tests in which procedure was "without knowledge", which promised no results whatever. "The animal's stubbornness must be broken," he commented. On the other hand, he regarded every criticism as a form of personal insult. And once he showed a member of the committee of the Society for the Protection of Animals the door, because the man, without having looked at his watch, wanted to show it to Hans and ask him the time. Many other critics had similar experiences.

Summarizing the remarks of this chapter, our judgment must be as follows: It is in the highest degree improbable that Mr. von Osten purposely trained the horse to respond to certain cues. It is also improbable that he knew that in every test he was giving signals, (although I can form no judgment concerning what happened after the publication of the latest report). To assume the contrary would land us in the midst of insoluble contradictions of the many ascertained facts in the case. The explanation here essayed, however, should prevent that. To be sure, we, must then reckon with curious inner contradictions in Mr. von Osten's character. But such contradictions are to be found, upon earnest analysis, in nearly every human character. And Mr. von Osten may say with the poet: "Ich bin kein ausgeklügelt Buch. Ich bin ein Mensch mit seinem Widerspruch."

FOOTNOTES:

[AJ] The author intends to take up the problem of counting, so-called, on the part of animals and of the principle involved, in another work soon to be forthcoming.

[AK] There are some who believe they are warranted in concluding the opposite from the structure of the animal's brain alone. We may say that the brain of the horse, compared with that of the ape, or even that of the dog, represents a relatively low type of development. But owing to the rapid changes in the views, often contradictory, concerning the nature of the nervous structures and processes underlying the thought process, any conclusion based on such views would be premature. For this reason we cannot agree with the French physiologist who was dissecting the brain of a horse and, struck by its smallness of size, exclaimed: "When I saw your proud look and beautiful neck, I hesitated a moment before mounting upon your back. But now that I have seen how small is your brain, I no longer have any qualm about using you."[98]

[AL] This natural and close connection between the process of attention and the movement toward the object attended to is clearly expressed in our English and French terms, derived from the Latin "tendere ad-," to reach toward-.

[AM] G. Franzius,[99] privy counselor of the admiralty, master of the dry-dock at Kiel, is responsible for the undeserved revival of the ancient belief, long buried by science, that the divining branch is put into motion solely as the result of the influence of hidden springs or treasures, and without any agency in the person who is holding it. The untenability of this theory comes home to us most forcibly when we recall how various are the kinds of things which have been discovered by means of the branch. First there is gold and water, which are the only ones mentioned by Mr. Franzius. The water can be thus discovered only when it flows below ground, say that which is passing through the mains of a city, whereas the water of the Rhine or the Elbe would have no effect on the branch. Besides gold, every other kind of metal has been supposedly located by the branch,-as well as coal, gypsum, ochre, red-chalk sulphur and petroleum,-according to the desire of the one searching. Thus, the very same branch that just a moment ago was influenced by the least bit of underground water, may remain unaffected by the presence of a large body of water, if in the meantime I have changed my plan and decide to search for coal or for gold. But that is not all. The branch will point out a murderer or the place where a murder has been committed, it will discover the thief or his trail, as well as the things stolen or merely touched by him. It will indicate where the boundary-stone that has been moved, ought to stand. The branch further discloses the sins of the persons concerning whom it is consulted, as well as their talents and abilities, the journeys they have made and the wounds they have received. It will indicate whether or not a person has money and how much. It can announce what absent persons are doing and what apparel they are wearing, and of what color it is. It will give information on theological, medical, zoological, and botanical questions. In fine, no matter what the question, it will never fail of an answer.[100, 101]

The impossibility of explaining the phenomena in a purely physical way was recognized at a very early date. For a long time the activity of the users of the divining rod seems to have been restricted to the search for metals. The first (or one of the first) to raise his voice against it was the learned G. Agricola[102] (1556), and after him there were many who all wrote more or less independently of one another. Aside from swindle and chance, it was usually believed that sorcery of the agency of Beelzebub was involved, and for that reason the Church has repeatedly forbidden the use of the divining-rod. But even in the 17th century we find some who believed that it was imagination alone that moved the person's hand, and with it the rod,[103, 104] ("fortassis etiam phantasia manum in motum concitante"); and that points out the essentials of the solution of the phenomenon, and we will not go into the matter here in detail. A number of complex psychological problems arising in connection with it are still waiting to be solved, but this much appears certain; the staff or branch plays no other part in the whole process than that which is served by the three levers in the tests described in Chapter IV (pages 116 ff.),-they simply magnify the expressive movements of the diviner. And so we can understand why the instruments serving as rod might be so varied. Hay-forks, pickets, clock-springs and pendulums, scissors and pliers have been used. A knife and fork or two pipes, fastened together, an open book, and even a sausage, grasped at both ends and thus bent together somewhat,-all have served the purpose equally well. We can understand, too, how some adepts are able to achieve the same degree of success-for they do succeed beyond a doubt-without any rod whatever, but simply by placing the index fingers end to end and bending them somewhat, and even by merely groping about with hands outstretched or folded before them.[106]

[AN] There is only one, and I believe it is only a seeming exception to be found in the literature on the subject. We are told that about the year 1840 a French revenue official named Léonard had two hunting dogs that, besides other things, were able to play at dominoes, and this not only with their master, but with anyone and without the master's assistance. The owner had educated them simply for the fun of it, and not for pecuniary gain. This statement is made by both writers who, apparently independently of one another, have discussed the case, Youatt[108] and de Tarade.[109] De Tarade himself played with them, and gives directions how to teach dogs to play the game. But his exposition is so na?ve, and even ridiculous, for those who know anything about the subject, that we do not believe it necessary to attempt a detailed refutation. Youatt never saw the animals. But he tells us that not only the dog's partner, but also the master, sat at the game. Youatt's assertion, however, that "not the slightest intimation could have been given by Mr. Leonard to the dog," but that the animal carried on the game by means of its own observation and calculation, appears to me a rather bold statement. After my own experience with dogs, I firmly believe this to have been impossible. Hachet-Souplet,[110] who shares my conviction, explains the matter as follows: the dog would simply place a domino having the number of eyes named by his partner, thus the 6 adjacent to the 6, the 3 to the 3, etc. But even so a great deal would have to be attributed to the dog, (although in that case real counting would by no means be absolutely necessary, for an association between the number term and the total picture of the corresponding group of eyes would suffice.) But we must note that neither of the writers mentions that the numbers were always called aloud by the partner. After the failure of the experiments of Sir John Lubbock,[111] we must doubt very much if a dog is able to match one domino with another having the same number of eyes. We are therefore inclined to believe that this dog continually received signs from its master. These signs probably were visual, perhaps also auditory, and they were by no means involuntary. For in a book on the training of animals, which Léonard, the owner of the dogs, has published, and in which he describes minutely the method by which they had been trained in their various accomplishments, he does not mention with so much as a syllable the game of dominoes, a thing which he certainly would have dwelt upon, if he had believed in the animals' power of independent thought. He would not have remained silent concerning this greatest-though only apparent-achievement of his educational endeavors. But his whole book is evidence that he was too wise to have thus deceived himself, and our only alternative is to believe that he was playing a joke on his credulous admirers.

[AO] P. Wasmann, S. J. in the third edition of his book, "Instinkt und Intelligenz im Tierreich" (Freiburg, Herder, 1905), discusses the case of Hans and quotes from a letter I wrote him concerning the matter. In the quotation an error has crept in, which I would here correct. The statement is ascribed to me that "Hans differs from other horses only in his extraordinary power of observation, an unintentional by-product of intentional training," whereas in my letter I said: "unintentional by-product of intentional education."

* * *

CONCLUSION

If we would make a brief summary of the status of Mr. von Osten's horse in the light of these investigations and try to understand what is the bearing upon the question of animal psychology in general, we may make the following statements.

Hans's accomplishments are founded first upon a one-sided development of the power of perceiving the slightest movements of the questioner, secondly upon the intense and continued, but equally one-sided, power of attention, and lastly upon a rather limited memory, by means of which the animal is able to associate perceptions of movement with a small number of movements of its own which have become thoroughly habitual.

The horse's ability to perceive movements greatly exceeds that of the average man. This superiority is probably due to a different constitution of the retina, and perhaps also of the brain.

Only a diminishingly small number of auditory stimuli are involved.

All conclusions with regard to the presence of emotional reactions, such as stubbornness, etc., have been shown to be without warrant. With regard to the emotional life we are justified in concluding from the behavior of the horse, that the desire for food is the only effective spring to action.

The gradual formation of the associations mentioned above, between the perception of movement and the movements of the horse himself, is in all probability not to be regarded as the result of a training-process, but as an unintentional by-product of an unsuccessful attempt at real education, which, though in no sense a training-process, still produced results equivalent to those of such a process.

All higher psychic processes which find expression in the horse's behavior, are those of the questioner. His relationship to the horse is brought about almost wholly by involuntary movements of the most minute kind. The interrelation existing between ideas having a high degree of affective coloring and the musculature of the body, (which is brought to light in this process), is by no means a novel fact for us. Nevertheless, it is possible that this case may be of no small value, on account of the great difficulties which are usually met in the attempt to establish experimentally the more delicate details in this field.

And, returning to the considerations of the first chapter, if we ask what contributions does this case make toward a solution of the problem of animal consciousness, we may state the following: The proof which was expected by so many, that animals possess the power of thought, was not furnished by Hans. He has served to weaken, rather than strengthen, the position of these enthusiasts. But we must generalize this negative conclusion of ours with care,-for Hans cannot without further qualification be regarded as normal. Hans is a domesticated animal. It is possible (though the opposite is usually assumed), that our animals have suffered in the development of their mental life, as a result of the process of domestication. To be sure, in some respects they have become more specialized than their wild kin, (e. g., our hunting dogs), and in their habits they have become adapted largely to suit our needs. This latter is shown by all the anecdotes concerning "clever" dogs, horses, etc. But with the loss of their freedom they have also gradually been deprived of the urgent need of self-preservation and of the preservation of their species, and thus lack one of the greatest forces that make for psychic development. And often their artificial selection and culture has been with a view to the development of muscle and sinew, fat and wool, all at the expense of brain development.[AP] Our horses are, as a rule, sentenced to an especially dull mode of life. Chained in stalls (and usually dark stalls at that,) during three-fourths of their lives, and more than any other domestic animal, enslaved for thousands of years by reins and whip, they have become estranged from their natural impulses, and owing to continued confinement they may perhaps have suffered even in their sensory life. A gregarious animal, yet kept constantly in isolation, intended by nature to range over vast areas, yet confined to his narrow courtyard, and deprived of opportunity for sexual activity,-he has been forced by a process of education to develop along lines quite opposite to his native characteristics. Nevertheless, I believe that it is very doubtful if it would have been possible by other methods, even, to call forth in the horse the ability to think. Presumably, however, it might be possible, under conditions and with methods of instruction more in accord with the life-needs of the horse, to awaken in a fuller measure those mental activities which would be called into play to meet those needs.

Though our investigations do not give support to the fantastic accounts of animal intelligence given by Brehms, they by no means warrant a return to Descartes and his theory of the animal-machine (as is advocated by a number of over-critical investigators). We cannot deny the validity of conclusions from analogy without denying at the same time the possibility of an animal psychology-indeed of all psychology. And all such conclusions indicate that the lower forms possess the power of sense-perception, that they, like us, presumably have at their disposal certain images, and that their psychic life is to a large extent also constituted of mere image-associations, and that they too, learn by experience. Also that they are susceptible to feelings of pleasure and of pain and also to emotions, as jealousy, fear, etc., though these may be only of the kind which have a direct relation to their life-needs. We are in no position to deny a priori the possibility of traces of conceptual thought in those forms nearest man in the scale-whether living in their natural manner or under artificial conditions. And even less so since the final word has not yet been spoken regarding the nature of conceptual thinking itself. All that is certain is that nothing of the kind has been proven to occur in the lower forms, and that as yet not even a suitable method of discovering its existence has been suggested. But the community of those elementary processes of mental life which we have mentioned above is in itself enough to connect the life of the lower forms with ours, and imposes upon us the duty of regarding them not as objects for exploitation and mistreatment, but as worthy of rational care and affection.

FOOTNOTES:

[AP] Buffon,[124] the great naturalist, expresses himself not less pessimistically in his own brilliant manner: "Un animal domestique est un esclave dont on s'amuse, dont on se sert, dont on abuse, qu'on altère, qu'on dépa?se et que l'on dénature."

* * *

SUPPLEMENTS

* * *

SUPPLEMENT I

MR. VON OSTEN'S METHOD OF INSTRUCTION

[By C. Stumpf]

The following is a report of the account, which Mr. von Osten gave Professor Schumann and me, of the method which he had used in the instruction of the horse, and which was illustrated by actual demonstrations. I cannot testify, of course, that Mr. von Osten really did adhere to this method throughout the four years in which he tutored the horse, but I will say that I have several good reasons for believing that it was impossible for him to have trumped up this make-believe scheme afterward, merely to mislead us. Among the reasons are the following: He was always ready to give a detailed explanation of any question which we might interpose; the written statements of Major von Keller, who has known Mr. von Osten for a period of fifteen years; the testimony of General Zobel, who became acquainted with the whole process fully a year before any public exhibitions were given; the accounts given by the tenants in Mr. von Osten's house, who for years saw the process of instruction going on in the courtyard of the apartment building,-according to their account his intercourse with the horse was like that with a child at school,-he made much use of the apparatus and never did they notice anything like an habituation to respond to certain signals; and finally the appearance of the apparatus itself-some of which could not be bought at second hand-was most convincing.

The apparatus used for the work in arithmetic consisted mainly of a set of large wooden pins, a set of smaller ones (such as are to be had in toy-shops), a counting-machine, such as is commonly used in the schools, a chart upon which were pasted the numbers from 1 to 100, and finally the digits, cut large and in brass and suspended from a string. For the work in reading Mr. von Osten used the chart shown in the frontispiece of this book. Here we have the letters of the alphabet in small German script with numbers written below which serve to indicate the row, and what place in that row, the letters occupy. For tones, a small, child's organ was used with the diatonic scale C^1 to C^2, and for instruction in colors, a number of colored cloths were used.

The work in arithmetic began by placing a single wooden pin in front of Hans and then commanding him: "Raise the foot!-One!" Here we must assume that the horse had learned to respond to the command to raise the foot during the preceding period, when tapping in general had been taught. In order to get the horse to learn that he was to give only one tap, Mr. von Osten tried to control the tapping by means of holding the animal's foot, just as a teacher tries to aid a pupil in learning to write by guiding his hand. He repeated this exercise so often that finally the single tap was made. And always the right foot was insisted upon. Bread and carrots were the constant rewards.

Two of the pins were now set up and the command given: "Raise the foot!-One, two!" Mr. von Osten again aided the establishment of the proper association by using his hand as before. At the same time the two pins were pointed out, and the order was always without exception from left to right. Gradually it became unnecessary to touch the foot or to point to the pins, and instead the question was introduced: "How many are there?", in order that the horse should become accustomed to these words as an invitation to give the taps when he saw the wooden pins before him.

Then three pins were taken and the words "one, two, three" were spoken, and so on. In naming a number the preceding ones were always named along with it, in order that the normal order might thus be learned at the same time. Later the number alone, without the preceding ones, sufficed to elicit the proper number of taps. The last word of the series thus becomes characteristic of the series as a whole. It differs from all the others, and thus becomes the sign for the whole series of numbers thus named, each of which arises as a memory image at the proper place in the series and is accompanied by a tap of the foot. Thus, Mr. von Osten at any rate had accounted to himself for his success.

But Hans was not to acquire merely this relatively mechanical process of counting (hardly to be called counting), but he was to acquire also some meaning content for the number terms. For this purpose everything depended upon the concept "and". Only he who can grasp its meaning will be able to understand a number. 2 is 1 and 1, 3 is 2 and 1. Mr. von Osten had someone hold a large cloth before the horse, where the wooden pins usually were placed. He then had the cloth taken up and he would pronounce emphatically the word "and". After this had been done a number of times, he put up two of the pins and obscured them by the cloth. The cloth was again raised and the word "and" pronounced. Then Hans, as a result of his previous instruction (so Mr. von Osten thought) would give two taps at sight of the pins. The thing was repeated with three pins, then with one, and so on, and the horse would always execute the proper number of taps.

Now, five pins were set up, the three to the right being covered by the cloth. The horse tapped twice and Mr. von Osten said "two". Then the cloth was raised, Hans gave three further taps, and Mr. von Osten said "and three" with emphasis.

In this simple manner he tried to get the horse to understand that the three belongs to the two, and that both together make five. The image of the five pins as it was known from previous experience, was to be associated with the combined groups of two and three, and conversely, it was to be reproduced when these groups were presented. Later the cloth and pins were omitted and the question was asked: "How much is two and three?". The horse tapped five times. It had learned how to add. Still this could be regarded only as a mechanical process, if the horse were able to add only those numbers which had been presented together one or more times in the manner just described. And so long as we remained within the first decade, we could get twenty-five binary combinations whose sum does not exceed 10 (counting inverted orders we would have forty-five binary permutations),-all of which might have been practised separately. But as a matter of fact, Mr. von Osten did not take this course, for as he himself says, he allowed Hans to discover a great deal for himself. "Hans had to develop the multiplication table for himself."-With larger numbers and more addends, the number of combinations becomes so great that there can be no doubt they were not practised separately.

Since, after all this preliminary instruction, Hans really began to give solutions of new problems, the master believed that this was proof that he had succeeded in inculcating the inner meaning of the number concepts, and not merely an external association of memory images with certain movement responses. But he always remained within the sphere of the ideas thus developed, and adhered closely to the customary vocabulary and its usage. Every new concept, each additional word was explained anew.

It would not be legitimate to condemn the whole procedure from the very beginning on the ground of the horse's lack of knowledge of language or of its use. It was Mr. von Osten's aim to convey to the horse an understanding of the language, by means of sense-presentations, adequate to give rise to the proper sense-perceptions. Helen Keller and other blind deaf-mutes have been educated to an understanding of the language without the aid of vision and hearing. They have come to it through the sense of touch alone. Everything depends upon whether or not the predisposition for it is present. And it was quite rational that Mr. von Osten should have chosen counting and arithmetical calculation as the processes by which to make his attack upon the animal mind, for as a matter of fact, nowhere else is it so easy to bridge the gap between perception and conception and nowhere else can the sign of success or failure be perceived so readily as in the handling of numbers. It is unfortunate, however, that he did not utilize these same signs for purposes of counter-testing also, as, for instance, by inquiring for the cube root of 729. But he was prevented from doing this by his close adherence to his pedagogical principle and by his unquestioning faith in the soundness of the entire procedure.

In teaching multiplication the counting machine was used. Two of the ten balls on one of the rods were pushed far to the left, thus: 00. "How many are there?" Two taps. "Very well. That is once two." Another group of two was pushed to the left, at a short interval from the first group, thus: 00 00. "How many times two balls are there?" was asked, with a decided movement of the hand toward the two groups. Two taps. "How many, therefore, are two times two?" Four taps.

The horse was supposed to learn the meaning of the word "times" by means of the spatial separation of the groups; he was to be taught to notice and to count the groups, and also the number of units in a single group. Three times two then meant three groups with two units in each group. The horse was supposedly aided by the following factors: the relative nearness of the units belonging to one group, as over against the space interval between the groups themselves; also that the groups were pointed out as wholes in connection with the emphatic enunciation of the words 'once, twice,' etc.; and finally the touching and raising of the horse's foot by means of the hand until all the desired associations of the ideas with one another and with the corresponding tapping movements were quite perfect.

Subtraction was taught in the following manner. Five pins were set up; the horse tapped five times. Mr. von Osten then removed two of them and said emphatically: "I take away,-minus. How many are still standing?" The horse tapped three times. Here, too, there was at first some assistance by means of the hand to get the tapping.

In division four balls were first pushed to the left end of the rod, thus: 0000. "How many balls are there to the left?" Four taps. They were now divided into two pairs, thus: 00 00. Pointing to the units of one group, the teacher asks: "There are always how many in the group?" Two taps. Three groups were formed, thus: 00 00 00. "There are now how many balls to the left?" Six taps. "And there are always how many in each group?", (pointing at them). Two taps. "And how often is two contained in six?", (pointing to the groups consecutively). Three taps, etc.

The ideas of 'part', of 'whole', and of 'being contained' were illustrated by means of a chalk line which was interrupted in one or more places by erasure.

In all these operations Mr. von Osten adhered strictly to the rule, and required others to do so too, that the number upon which the operation was performed, must be mentioned first. Thus, one was not to say, "take 3 away from 7", but "from 7 take away 3." Otherwise, he believed, Hans would become easily confused. Also one was not allowed to say "to multiply", but to "take" a certain number so many "times". He, himself, never departed from this practice.

We will not go into the details of the method by which Hans was taught the meaning of the number signs, of the signs of operation, of the numbers above 10, or the significance of "digits", "tens", etc. Only this,-when in problems in addition the sum was greater than 10, the 10 was first tapped and then the remainder of the number added to the 10. Thus: "You are to add 9 and 5. How much must you add to the 9 to have 10?" One tap. "But now, you were to add not merely 1, but 5; how much have you still to add to the 10?"-Four taps. In like manner, whenever the addends were below 20 or 30 and the sum above 20 or 30, Mr. von Osten would ask for the 20 or 30 taps first. He thought that he was thus giving his pupil an ever firmer grasp upon the principle of the structure of our number system, in which all higher numbers are constituted of tens and digits. For the same reason he used at first, instead of the words 'eleven' and 'twelve' ('elf' and 'zw?lf' in the German), expressions which in English might be rendered as 'one-teen' and 'two-teen' ('einzehn' and 'zweizehn' in the German); and only later, after the animal had seemingly mastered the meaning in question, did Mr. von Osten replace them by the usual forms.

All this was beautifully conceived and might perhaps form the basis for the instruction of primitive races. But it is of immediate interest for us only because it enables us to better understand the origin of the conviction under which Mr. von Osten and his followers labored.

* * *

SUPPLEMENT II

THE REPORT OF SEPTEMBER 12, 1904

"The undersigned came together for the purpose of investigating the question whether or not there is involved in the feats of the horse of Mr. von Osten anything of the nature of tricks, that is, intentional influence or aid, on the part of the questioner. After a careful investigation they are unanimously agreed that such signs are out of the question under the conditions which were maintained during this investigation. This decision in no wise takes into account the character of the men exhibiting the horse, and who are known to most of the undersigned: In spite of the most attentive observation, nothing in the way of movements or other forms of expression which might have served as a sign, could be discovered. In order to obviate involuntary movements on the part of those present, one series of tests was made with only Mr. Busch present. Among these tests were some in which, according to his professional judgment, the possibility of tricks of the sort commonly used in training, was excluded. Another series of tests was made in such a way that the correct answers to the questions which Mr. von Osten put to the horse, were unknown to the questioner. From previous observation the greater number of the undersigned also know of a large number of cases in which, during the absence of Mr. von Osten and Mr. Schillings, other persons were likewise able to obtain correct responses from the horse. Among these were some cases in which the questioner did not know the correct solution of the problem or was mistaken about it. And lastly, several of the undersigned have become acquainted with the method which Mr. von Osten used, which has little in common with methods of training, and is patterned after the instruction given in the elementary schools. As a result of these observations the undersigned are of the opinion that unintentional signs of the kind which are at present familiar, are likewise excluded. They are unanimously agreed that this much is certain: This is a case which appears in principle to differ from any hitherto discovered, and has nothing in common with training, in the usual sense of that word, and therefore is worthy of a serious and incisive investigation.

Berlin, September 12, 1904.

Paul Busch, Circus-manager.

Otto, Count zu Castell-Rüdenhausen.

Dr. A. Grabow, member of the schoolboard, retired.

Robert Hahn, Teacher, Municipal schools.

Dr. Ludwig Heck, Director of the Zo?logical Garden.

Dr. Oscar Heinroth, Assistant in the Berlin Zo?logical Garden.

Dr. Richard Kandt.

Major F. W. von Keller, retired.

Major-General Th. K?ring, retired.

Dr. Miessner, Assistant in the Royal Veterinary College.

Prof. Nagel, Head of the department of sense-physiology in the Physiological Institute of the University of Berlin.

Prof. C. Stumpf, Director of the Psychological Institute, Member of the Academy of Sciences.

Henry Suermondt."

* * *

SUPPLEMENT III

AN ABSTRACT FROM THE RECORDS OF THE SEPTEMBER-COMMISSION[AQ]

The important meetings occurred on the 11th and 12th of September and both of them extended over four hours. The greatest difficulty was occasioned by the condition laid down by Mr. von Osten: that we were to work without him from the very beginning. In a certain sense this condition had been met once before when Mr. Schillings appeared upon the scene, a man whose fairness ought to be doubted by none. He came utterly skeptical, and yet in the course of a week he learned to handle the horse and received responses regularly. However, since the public had begun to doubt Mr. Schillings also, another person had to attempt the r?le of questioner. Count zu Castell tried to do this and practised for some days before the meetings, but his success-although of no small moment-was not great enough to be convincing.

In apprising Mr. von Osten of this fact we caused a veritable catastrophe. He declared in a most decisive manner that he would have to insist upon the condition he had imposed, since the public demanded it, and he could never assist in any tests, until he had been cleared of the suspicion of having descended to the use of tricks. If it should take weeks to accustom the horse to a new questioner, there would be no alternative but to wait that length of time.

A happy circumstance helped us out of our difficulty. We had chanced in our discussion to mention the experience of Dr. Miessner, a member of the commission, who on the day before had gone to witness an exhibition of the mare "Clever Rosa", and who believed that he had succeeded in discovering the tricks involved. There was a sudden change in Mr. von Osten's attitude. He expressed his willingness to undergo the most stringent examination and agreed to anything in the way of conditions of control, challenging even the proven ability of Dr. Miessner. "I have neither whip nor rod, as had the man in the exhibition, and agree to any precautionary measures you may care to take."

After he had gone, the commission decided to ask him to have the horse perform one of the more common, simple, feats. They were going to watch him very closely. Different members were assigned the task of attending to different parts of his body (head, eyes, right hand, left hand, etc.) while Mr. Busch, since he was the most proficient in the detection of tricks, was to regard the total behavior of the man.

The exhibitions included the indication of the day of the week by means of taps, the day just past, the day ahead, its date, arithmetical problems, and the counting of rings strung upon a rod. Messrs. Grabow and Hahn interpolated a few tests themselves, in which they did the questioning. All tests were successful.

Mr. von Osten withdrew, and in comparison of notes which followed, Mr. Busch, as well as all the others, declared that they had discovered nothing of the nature of a visible sign. Mr. Busch said that he had also kept an eye on the spectators and had noticed nothing there. Nevertheless, he desired to see Mr. von Osten go through one series with no one else but himself (Busch) present.

This was done, and on this occasion a number of tests were made in the recognition of colored cloths. The horse was required to indicate, by tapping, the place in the series which the cloth occupied and was then asked to bring the green or the red, as the case might be, in his mouth. Furthermore, he was asked to approach that one of the five gentlemen standing at a distance, whose photograph had been shown him. Then he was requested to spell the words "Rat" and "Busch" according to the method which he had been taught. Nearly all of these tests were likewise successful.

In the conference which followed, Mr. Busch again declared that he had noticed no trace of a sign; he maintained that, in the selecting of colored cloths (especially when they were placed so closely together) and in the approach toward a person, there was no possibility whatever that some trick was being used.

During the session of September 12th, Mr. von Osten agreed to two sets of experiments.

1. Another man was to put the question to the horse. Mr. von Osten himself was to stand, back to back to the questioner and to bend forward, so that he was effectually hidden from the horse's view, yet could, by means of occasional calls, make his presence known to the animal. The assumption was that it would be conducive to success if the horse knew that the master was present and was awaiting the answer, and yet at the same time the possibility of receiving a sign was obviated.

2. Another man in Mr. von Osten's absence was to ask the horse to tap a certain number. Then the questioner was to leave, and Mr. von Osten, returning, was to ask the horse to perform some arithmetical process with the number which was thus unknown to the master. Mr. von Osten said that he thought that this method was somewhat risky, since the horse would be aware that he, Mr. von Osten, did not know the number, and might therefore be in a humor to play some prank.

The questions of the first sort were answered with but very few errors. Mr. Hahn and Count zu Castell asked simple questions in arithmetic. When Mr. von Osten withdrew into the stable, the count put several other problems, among them the counting of persons and of windows, all of which were solved correctly.

Between the first and second series of tests the following experiments were interpolated. The names of six members of the commission were written upon six slates respectively, which were then suspended from a string. Mr. von Osten pointed to one of the men and asked: "On which of the slates is this gentleman's name to be found?" The correct number was tapped in every case. The command to approach the slate in question was also obeyed as a rule, although this was not as uniformly successful as tapping.

In the conference which followed, Mr. Busch declared that the feats appeared inconceivable to him; and again none of the men had noted anything in the way of signs.

Now followed the second series of tests mentioned above. In order to be sure to get the correct responses, Mr. Schillings, who up to this point had not been present at any of the experiments, was asked to put the questions to the horse. Mr. von Osten went into the house, accompanied by a member of the commission. And again, Mr. Schillings would go out before the second part of the test, without having met Mr. von Osten.

Five tests were made in this way. They were not attended by such amazing success as were the preceding ones, but nevertheless the results were surprising. The horse nearly always repeated the number itself, instead of performing the operation required. Since, however, Mr. Schillings, owing to a misunderstanding, had, in the first two cases, said to the horse: "You are to repeat this number for Mr. von Osten", the errors might appear to be a result of this request.

At the final discussion, the result of which was the unanimous declaration which was given for publication, not only the data obtained during these two sessions, but also the earlier experiences of some of the members of the commission were taken into consideration. None of the tests witnessed could be referred to chance or to the use of tricks. Count zu Castell pointed out that in the course of eight days he had elicited forty correct responses from the horse, among them some in regard to which he himself had been momentarily in error. Other members recalled the many instances in previous exhibitions, during which both Mr. Schillings and Mr. von Osten were absent, when questions were put to the horse by others. The commission also had access to a detailed account written by Professor Stumpf on Mr. von Osten's method of instruction, based on the explanations and demonstrations which Mr. von Osten had himself given. As a result of these considerations the commission felt under obligations to give public expression to its conviction. In the report it limited itself, however, to the purely negative side-principally in denying the use of tricks,-and expressed no opinion with regard to the actual genesis of the horse's accomplishments, since it believed that there was great possibility that other factors were involved which ought to be carefully investigated.

[AQ] A few days after the 12th of September I made the present abstract from the original records of the Commission, which I have here abbreviated somewhat. (See page 8). Referring once more to the misunderstanding mentioned on page 3, I would say that the closing sentence of the report is here re-given literally as it then appeared. C. St.

* * *

SUPPLEMENT IV

THE REPORT OF DECEMBER 9TH, 1904

Together with Dr. E. von Hornbostel and Mr. O. Pfungst, I have tried during the past few weeks to find an explanation of the accomplishments of the horse 'Hans' by the experimental method. We had access to the horse in the absence of the master and groom. The results are as follows:

The horse failed in his responses whenever the solution of the problem that was given him was unknown to any of those present. For instance, when a written number or the objects to be counted were placed before the horse, but were invisible to everyone else, and especially to the questioner, he failed to respond properly. Therefore he can neither count, nor read, nor solve problems in arithmetic.

The horse failed again whenever he was prevented by means of sufficiently large blinders from seeing the persons, and especially the questioner, to whom the solution was known. He therefore required some sort of visual aid.

These aids need not, however,-and this is the peculiarly interesting feature in the case,-be given intentionally. The proof for this is found in the fact that in the absence of Mr. von Osten the horse gave correct replies to a large number of persons; and to be more specific, Mr. Schillings and later Mr. Pfungst, after working with the horse for a short time, regularly received correct answers, without their being in any way conscious of having given any kind of signal.

So far as I can see, the following explanation is the only one that will comport with these facts. The horse must have learned, in the course of the long period of problem-solving, to attend ever more closely, while tapping, to the slight changes in bodily posture with which the master unconsciously accompanied the steps in his own thought-processes, and to use these as closing signals. The motive for this direction and straining of attention was the regular reward in the form of carrots and bread, which attended it. This unexpected kind of independent activity and the certainty and precision of the perception of minimal movements thus attained, are astounding in the highest degree.

The movements which call forth the horse's reaction, are so extremely slight in the case of Mr. von Osten, that it is easily comprehensible how it was possible that they should escape the notice even of practised observers. Mr. Pfungst, however, whose previous laboratory experience had made him keen in the perception of visual stimuli of slightest duration and extent, succeeded in recognizing in Mr. von Osten the different kinds of movements which were the basis of the various accomplishments of the horse. Furthermore, he succeeded in controlling his own movements, (of which he had hitherto been unconscious), in the presence of the horse, and finally became so proficient that he could replace these unintentional movements by intentional ones. He can now call forth at will all the various reactions of the horse by making the proper kind of voluntary movements, without asking the relevant question or giving any sort of command. But Mr. Pfungst meets with the same success when he does not attend to the movements to be made, but rather focuses, as intently as possible, upon the number desired, since in that case the necessary movement occurs whether he wills it or not. In the near future he will give a special detailed report of his observations, which gives promise of becoming a valuable contribution to the study of involuntary movements. Also he will give an account of our tests and of the mechanism of the various accomplishments of the horse. We must also defer, till then, the disproof of certain seemingly relevant arguments in favor of the horse's power of independent thought.

Some defenders of the view which maintains the horse's rationality may urge that it was only through our experiments that the animal became trained and spoiled in so far as the ability to think is concerned. They are refuted in this, however, by the fact that the horse still continues to solve problems involving decimal fractions and to determine calendar dates for Mr. von Osten, as brilliantly as ever, as is shown by his recent demonstration before a large group of spectators. That these results are now being achieved in a manner essentially different from formerly is nothing but a bare assertion.

On the other hand, now that the possibility has been established that these wonderful results may be obtained in all their complexity by means of intentional signs, many will question whether Mr. von Osten did not himself train the horse from the very beginning to respond to these signs. No one has the right, however, to charge an old man, who has never had a blemish on his reputation, with having invented a most refined network of lies, if the facts can be explained in a satisfactory manner in some other rational way. And this can be done in this case. For we have seen that there is another alternative, other than the theory that the horse can think or the assumption that tricks have been employed.

And now, aside from the specific results obtained, what is the scientific and philosophic import of the whole affair?-For one thing, the revolution in our conception of the animal mind, which had been hoped for by some, and feared by others, has not taken place. But a conclusion of an opposite character is justified. If such unexampled patience and high pedagogical excellence as was daily brought to bear by Mr. von Osten during the course of four long years, could not bring to light the slightest trace of conceptual thinking, then the old assertion of the philosophers that the lower forms are incapable of such thinking, finds corroboration in the results of these experiments so far as the animal scale up to and including the ungulates is concerned. For this reason the tremendous effort put forth by Mr. von Osten, is not, in spite of the self-deception under which he labors, lost to science. If anyone has the courage to try the experiment with the dog or the ape, the insight which we have now gained will enable him to beware of one source of error which hitherto has not been noticed.

In the face of much misapprehension which has arisen, I wish once more to say emphatically that the committee of September 12th in no wise declared itself to be convinced that the horse had the power of rational thinking. The committee restricted itself entirely to the question whether or not tricks were involved, and, intentionally and rightly referred the positive investigation to a purely scientific court. I would also report that for some time Mr. Schillings has been convinced, by his own observations, of the horse's lack of reason, and when he was apprised of our conclusion in the matter, he embraced it without wavering. I have no intention of taking part in any discussion which may arise in the press as a result of the present report. Unless they wish to confine themselves to mere guesswork, the defenders of other views will not shrink from the task of basing their criticism upon careful methodical experimentation, and they will keep a detailed record of their results day by day; for statements based solely upon memory, without specific report of experimental conditions, prove nothing.

Prof. Carl Stumpf.

December 9th, 1904.

* * *

TABLE OF REFERENCES

* * *

(The names of the authors of anonymous works are placed in parenthesis.)

1. Zell, Th. Das rechnende Pferd. Ein Gutachten über den "Klugen Hans" auf Grund eigener Beobachtungen. Berlin, R. Dietze, 1904.

2. Freund, F. Der "kluge" Hans? Ein Beitrag zur Aufkl?rung. Berlin, Boll and Pickardt, 1904.

3. Hansen, F. C. C. and A. Lehmann. über unwillkürliches Flüstern. Philosophische Studien, edited by W. Wundt, Leipsic, 1895, Vol. 11, pp. 471 ff.

4. Sanden, S. v. über Aktivit?t und Passivit?t des Reiters und seiner Hülfen. Deutsche hippologische Presse, Berlin, 1896, Jahrg. 12, No. 11, pp. 117 ff. and No. 12, pp. 128 ff.

5. Weyer, E. M. Some Experiments on the Reaction-Time of a Dog. Studies from the Yale Psychological Laboratory, New Haven, Conn., 1895, Vol. 3, pp. 96 f.

6. Dodge, R. Die motorischen Wortvorstellungen. Halle a. S., M. Niemeyer, 1896, pp. 40 and 77.

7. Darwin, Chas. The Expression of the Emotions in Man and Animals. New York, D. Appleton & Co., 1873, PP. 273 ff.

8. Wundt, W. V?lkerpsychologie. Leipsic, W. Engelmann, 1900, Vol. 1, Part I, pp. 175 f.

9. Lieber, F. On the Vocal Sounds of Laura Bridgeman. Smithsonian Contributions to Knowledge, Washington, 1851, Vol. 2, Art 2, pp. 11 f. (Laura wrote her name: Bridgman.)

10. Garner, R. L. The Speech of Monkeys. New York, Chas. Webster & Co., 1892, pp. 57 ff.

11. Féré, Chas. Sensation et mouvement. Paris, F. Alcan, 1887, pp. 102 f.

12. James, W. The Principles of Psychology. New York, Henry Holt & Co., 1890, Vol. 2, pp. 372 and 381.

13. Beard, G. M. The History of Muscle-Reading. Journal of Science, and Annals of Astronomy, Biology, Geology, etc., London, 1881, Series 3, Vol. 3, p. 558 f.

14. Laurent, L. Les procédés des liseurs de pensées. Journal de psychologie normale et pathologique, Paris, 1905, second year, No. 6, pp. 489 f.

15. Guicciardi, G. e G. C. Ferrari. Il lettore del pensiero "John Dalton." Rivista sperimentale di Freniatria ecc., Reggio nell' Emilia, 1898, Vol. 24, p. 209.

16. Tarchanoff, J. de. Hypnotisme, suggestion et lecture de pensées. Translated from the Russian by E. Jaubert, second edition. Paris, G. Masson, 1893, pp. 153 ff.

17. Preyer, W. Telepathie und Geisterseherei in England. Deutsche Rundschau, Berlin, 1886, Jahrg. 12, Heft 4, p. 40.

18. Sommer, R. Dreidimensionale Analyse von Ausdrucksbewegungen. Zeitschrift für Psychologie und Physiologie der Sinnesorgane, Leipsic, 1898, Vol. 16, pp. 280 ff.

19. Frenkel, H. Des secousses rhythmiques de la tête chez les aortiques et chez les personnes saines. Revue de Médecine, Paris, 1902, 22nd Year, No. 7, pp. 617 ff.

20. Zoneff, P. and E. Meumann. über Begleiterscheinungen psychischer Vorg?nge in Atem und Puls. Philosophische Studien, edited by W. Wundt, Leipsic, 1903, vol. 18, p. 3.

21. Müller, G. E. and A. Pilzecker. Experimentelle Beitr?ge zur Lehre vom Ged?chtniss. Zeitschrift fur Psychologie und Physiologie der Sinnesorgane, Leipsic, 1900, Erg?nzungsband 1, pp. 58 ff.

22. Kraepelin, E. Der psychologische Versuch in der Psychiatrie. Psychologische Arbeiten, edited by the same, Leipsic, 1895, Vol. 1, pp. 50 ff.

23. Amberg, E. über den Einfluss von Arbeitspausen auf die geistige Leistungsf?higkeit. Ditto, pp. 374 ff.

24. Shaler, N. S. Domesticated animals. London, Smith Elder & Co., 1896, pp. 143 ff.

25. Coupin, H. L'esprit des animaux domestiques. La Revue, Paris, 1903, first quarter, Vol. 44, p. 586.

26. (Lebrun, P.). Lettres qui découvrent l'illusion des philosophes sur la baguette, et qui détruisent leurs systèmes. Paris, J. Boudot, 1696, pp. 239 ff.

27. Notice sur un nouvel instrument, dont Mr. Ritter, membre de l'académie de Munich s'est servi dans les expériences qu'il a récemment faites avec Mr. Campetti etc. Bibliothèque Brittannique, Sciences et Arts, Geneva, 1807, Vol. 35, p. 91.

28. Zell, Th. Tierfabeln und andere Irrtümer in der Tierkunde. 2nd edition. Stuttgart, Kosmos (1905), p. 38.

29. Thorndike, E. L. Animal Intelligence. Psychological Review, Lancaster, Pa. and New York, 1898, Monograph Supplements, Vol. 2, No. 4, p. 95.

30. Vaschide, N. et P. Rousseau. études expérimentales sur la vie mentale des animaux. Revue scientifique, Paris, 1903, Series 4, Vol. 19, No. 25, p. 782.

31. Ettlinger, M. Sind die Tiere vernünftig? Hochland, Munich and Kempten, 1904, Jahrg, 2, Heft 2, p. 223.

32. Romanes, G. J. On the Mental Faculties of the Bald Chimpanzee (Anthropopithecus calvus). Proceedings of the Scientific Meetings of the Zoological Society of London, 1889, pp. 320 f.

33. Kinnaman, A. J. Mental Life of two Macacus rhesus Monkeys in Captivity. American Journal of Psychology, Worcester, Mass., 1902, Vol. 13, No. 1, pp. 139 ff.

34. Himstedt, Fr. and W. A. Nagel. Versuche über die Reizwirkung verschiedener Strahlenarten auf Menschen- und Tier-augen. Festschrift der Albrecht-Ludwigs-Universit?t in Freiburg zum 50 j?hrigen Regierungs-Jubil?um Sr. Konigl. Hoheit des Groszherzogs Friedrich. Freiburg i. Br., C. A. Wagner, 1902, pp. 272 ff.

35. Dahl, F. Naturwissenschaftliche Wochenschrift, Jena, 1905, New series, Vol. 4, No. 48, pp. 767 ff.

36. Corte, Claudio. Il cavallerizzo. Di nuove dall'auttore stesso corretto ed emendato. Venice, G. Ziletti, 1573, Book 1 Chap. 6, page 8. (I did not have access to the first edition of 1562, cf. Graesse, Trésor de livres rares, 1861, Vol. 2, p. 277.)

37. Riegel. Untersuchungen über die Ametropie der Pferde. Monatshefte für praktische Tierheilkunde, Stuttgart, 1904, Bd. 16, Heft 1, pp. 31 ff.

38. Berlin, R. über die Sch?tzung der Entfernungen bei Tieren. Zeitschrift für vergleichende Augenheilkunde, Wiesbaden, 1891, Bd. 7, Heft 1, pp. 5 f.

39. The same. über ablenkenden Linsen-Astigmatismus und seinen Einfluss auf das Empfinden von Bewegung. Ditto, 1887, Bd. 5, Heft 1, pp. 7 ff.

40. Schleich, G. Das Sehverm?gen der h?heren Tiere. Tübingen, F. Pietzcker, 1896, p. 24.

41. K?nigsh?fer. über das ?ugen des Wildes. Monatshefte des Allgemeinen Deutschen Jagdschutz-Vereins, Berlin, 1898, Jahrg. 3, No. 17, pp. 250 f.

42. Zürn, J. Vergleichend histologische Untersuchungen über die Retina und die Area centralis retin? der Hauss?ugetiere. Archiv fur Anatomie und Physiologie, Anatomische Abteilung, Leipsic, 1902, Supplementary volume, pp. 116 ff.

43. Hirschberg, J. Zur vergleichenden Ophthalmoskopie. Archiv fur Anatomie und Physiologie, Physiologische Abteilung, Leipsic, Jahrg. 1882, p. 96.

44. Berlin, R., see 39, p. 4.

45. The same. über den physikalisch-optischen Bau des Pferdeauges. Zeitschrift fur vergleichende Augenheilkunde, Leipsic, 1882, Jahrg. 1, Heft 1, p. 32.

46. Bayer, J. Tier?rztliche Augenheilkunde. Vol. 5 of the "Handbuch der Tier?rztlichen Chirurgie und Geburtshilfe" by J. Bayer und E. Fr?hner. Vienna und Leipsic, W. Braumüller, 1900, p. 459.

47. The same. Ditto, p. 475.

48. Riegel, see 37, p. 35.

48a. Schwendimann, F. Untersuchungen über den Zustand der Augen bei scheuen Pferden. Archiv für wissentschaftliche und praktische Tierheilkunde, Berlin, 1903, Bd. 29, Heft 6, p. 566.

48b. Berlin, R. Refraktion und Refraktionsanomalien von Tieraugen. Tageblatt der 52. Versammulung deutscher Naturforscher und ?rzte in Baden-Baden, 1879, p. 348. See also 45, pp. 28 f. and 39, p. 13.

49. The same, see 39, p. 9.

50. Bayer, J., see 46, pp. 460 f.

51. Zürn, J., see 42, p. 114.

52. Chievitz, J. H. über das Vorkommen der Area centralis retin? in den vier h?heren Wirbeltierklassen. Archiv für Anatomie und Physiologie, Anatomische Abteilung, Leipsic, 1891, Heft 4-6. p. 329.

53. Zürn, J., see 42, p. 140.

54. K?nigsh?fer, see 41, pp. 251 ff.

55. Tennecker, S. v. Bemerkungen und Erfahrungen über den Charakter und das Temperament, sowie über die geistigen Eigenschaften des Pferdes überhaupt. Beitr?ge zur Natur- und Heilkunde, von Friedreich und Hesselbach, Würzburg, 1825, Vol. 1, pp. 110 f.

56. Zborzill, E. Die mnemonische Dressur des Hundes. Berlin, S. Mode (1865), p. 21.

57. Müller, Ad. und K. Tiere der Heimat. 3rd Edition, Cassel, Th. Fischer, 1897, Book 1, p. 70.

58. Hutchinson, W. N. Dog Breaking. 6th Edition, London, J. Murray, 1876, pp. 105 f.

59. Huggins, Lady M. Kepler: a Biography. Cited by Sir J. Lubbock, On the Senses, Instincts, and Intelligence of Animals. London, Kegan Paul, Trench and Co., 1888, pp. 284 f. (The original was published privately and never put on the market. Hence it was not accessible for me.)

60. Lubbock, Sir J. Ditto, p. 285.

61. Rouhet, G. L'entra?nement complet et expérimental de l'homme avec étude sur la voix articulée, suivi de recherches physiologiques et pratiques sur le cheval. Paris, Libraires associés, and Bordeaux, Feret et fils, 1902, pp. 517 ff.

62. Lipps, Th. Zur Psychologie der Suggestion. Leipsic, J. A. Barth, 1897, pp. 5 f.

63. Zell, Th. See 1, pp. 40 f.

64. Zborzill, E. See 56, p. 23.

65. Beard, G. M. Physiology of Mind-Reading. Popular Science Monthly, New York, February 1877. Vol. 10, p. 472. Reprint in the Journal of Science, and Annals of Astronomy, Biology, Geology, etc., London, 1881, Series 3, Vol. 3, p. 418.

66. Babinet. Les tables tournantes au point de vue de la mécanique et de la physiologie. Revue des deux mondes, Paris, 1854, Twenty-fourth year, Vol. 5, pp. 409 f.

67. Tolstoi, L. N. Anna Karenina.

68. Goldbeck. Besitzen die Tiere, speziell Hunde, Verstand oder nicht? Deutsche tier?rztliche Wochenschrift, Hannover, 1902, Jahrg. 10, No. 20, p. 202.

69. Menault, E. L'intelligence des animaux. 4th Edition, Paris, Hachette et Cie., 1872, p. 233.

70. LeBon, G. L'equitation actuelle et ses principes. 3rd Edition, Paris, Firmin-Didot et Cie., 1895, pp. 120 and 288.

71. Loiset, B. Praktischer Unterricht in Kunstdarstellungen mit Pferden. New edition. Stuttgart, Schickhardt u. Ebner, 1884, pp. 69 f. and 98 ff.

72. Baucher, F. Dictionnaire raisonné d'équitation. 2nd Edition, Paris, chez l'auteur, 1851, pp. 291 ff.

73. Arnim, v. Praktische Anleitung zur Bearbeitung des Pferdes an der Longe. 2nd Edition, Leipsic, Zuckschwerdt und Co., 1896, pp. 18 f. and 39 f.

74. Meehan, J. The Berlin "Thinking" Horse. Nature, London. 1904, Vol. 70, No. 1825, p. 602.

75. Spohr. Die Logik in der Reitkunst. Part 2. Pamphlet No. 32 in the Series: "Unsere Pferde." Stuttgart, Schickhardt und Ebner, 1904, p. 29 f.

76. Redding, T. B. The Intelligence of a Horse. Science, New York, 1892, Vol. 20, No. 500, pp. 133 f.

77. Spohr. Die naturgem?sze Gesundheitspflege der Pferde. 4th Edition, Hannover, Schmorl u. v. Seefeld Nachf., 1904, p. 164.

78. Decroix, E. Projet de langage phonétique universel pour la conduite des animaux. Bulletin de la Société nationale d'Acclimatation de France, Paris, 1898, Forty-fourth Year, pp. 241 ff.

79. Noizet, Général. Etudes philosophiques. Paris, H. Plon, 1864, Vol. 1, pp. 471 ff.

80. Beard, G. M. See 65, Vol. 10, p. 471.

81. LeBon, G. See 70, p. 120.

82. Flügel, O. Das Seelenleben der Tiere. 3rd Edition, Langensalza, H. Beyer und S?hne, 1897, pp. 50 f.

83. Landois, H. über das musikalische Geh?r der Pferde. Zeitshrift für Veterin?rkunde, Berlin, 1889, Jahrg. 1, No. 6. pp. 237 ff.

84. Foveau de Courmelles. Les facultés mentales des animaux, Paris, J. B. Baillière et fils, 1890, p. 142.

85. Zürn, F. A. Die intellektuellen Eigenschaften (Geist und Seele) der Pferde. Pamphlet 8 of the Series: "Unsere Pferde." Stuttgart, Schickhardt und Ebner, 1899, p. 26.

86. Fillis, J. Tagebuch der Dressur. Translated from the French by J. Halperson and G. Goebel. Stuttgart, Schickhardt und Ebner, 1906, pp. 322 f.

87. Athenaeus. Dipnosophist?. Book 12, 520 c. Edited by G. Kaibel. Leipsic, B. G. Teubner, 1890, Vol. 3, pp. 148 f.

88. Aelianus, Cl. De natura animalium. Book 16, 23. Edited by R. Hercher. Leipsic, B. G. Teubner, 1864, Vol. 1, p. 401.

89. Julius Africanus, S. Κεστο?, chapter 14. In: Veterum Mathematicorum Opera. Paris, Typographia Regia, 1693, P. 293.

90. Guénon, A. Influence de la musique sur les animaux et en particulier sur le cheval. (Chalons-sur-Marne), 1898, pp. 83 ff.

91. Lépinay. L'hypnotisme chez le cheval. Revue de l'hypnotisme, Paris, 1903, Eighteenth Year, No. 5, pp. 152 f.

92. Fillis, J. Grunds?tze der Dressur und Reitkunst. Translated from the French by G. Goebel. 3rd Edition, Stuttgart, Schickhardt und Ebner, 1905, pp. 10 f.

93. Manouvrier, L. Mouvements divers et sueur palmaire consécutifs à des images mentales. Revue philosophique, Paris, 1886, Vol. 22, pp. 204 ff.

94. Gasparin, Cte A. de. Des tables tournantes, du surnaturel en général et des esprits. 2nd Edition, Paris, E. Dentu, 1855, Vol. 1, Part 1.

95. Rivers, W. H. R. and E. Kraepelin. über Ermüdung and Erholung. Psychologische Arbeiten, edited by E. Kraepelin, Leipsic, 1895, Vol. 1, pp. 636f.

96. (Carpenter, W. B.). Spiritualism and its Recent Converts. Quarterly Review, London, 1871, Vol. 131, No. 262, p. 312.

97. Darwin, Chas. See 7, p. 48.

98. Saint-Ange, de. Cours d'hippologie. 2nd Edition, Paris, chez Dumaine et chez Leneveu and Saumur, chez Mlle. Niverlet et chez Mlle. Dubosse, 1854, Vol. 1, p. 101.

99. Franzius, G. Die Wünschelrute. Zentralblatt der Bauverwaltung, Berlin, 1905, Jahrg. 25, No. 74, pp. 461 f.

100. Ménestrier, Cl. Fr. La philosophie des images énigmatiques. Lyon, J. Guerrier, 1694, pp. 483 f.

101. (Lebrun, P.). Histoire critique des pratiques superstitieuses, qui ont séduit les peuples et embarassé les s?avans. Paris (et Amsterdam), 1702, p. 42.

102. Agricola, G. De re metallica libri XII, eiusdem de animantibus subterraneis liber. Basel, Froben, 1556, Book 2, pp. 27 f.

103. Schott, C. Magia universalis natur? et artis. Würzburg, J. G. Sch?nwetters Erben, 1659, Part 4, Book 4, p. 430.

104. The same. Physica curiosa, sive mirabilia naturae et artis. Würzburg, 1662, Part 2, Book 12, p. 1532.

105. Zeidler, J. G. Pantomysterium, oder das Neue vom Jahre in der Wünschelruthe, etc. Hall in Magdeburg (Halle a. S.), Renger, 1700, Chap. 2. p. 47.

106. Barrett, W. F. On the so-called Divining Rod, or Virgula Divina. Proceedings of the Society for Psychical Research, London, 1897, Vol. 13, pp. 177 f.

107. Theophanes. Chronographia. Paris, Typographia Regia, 1655, pp. 189 f.

108. Youatt, W. The Dog. London, Ch. Knight and Co., 1845, pp. 108 ff.

109. Tarade, E. de. Traité de l'élevage et de l'éducation du chien. Paris, E. Lacroix (1866), pp. 113 ff.

110. Hachet-Souplet, P. Die Dressur der Tiere. Translated from the French by O. Marschall v. Bieberstein, Leipsic, O. Klemm, 1898, pp. 36 f.

111. Lubbock, Sir J. See 59, pp. 280 f.

112. Léonard, A. Essai sur l'éducation des animaux, le chien pris pour type. Lille, Leleux, 1842, pp. 81-185.

113. Meehan, J. See 74, p. 602.

114. Franconi (G?rtner). Die Dressur der Kunstpferde. Jahrbuch fur Pferdezucht, Pferdekenntnis, Pferdehandel usw. auf das Jahr 1835, Weimar und Ilmenau, 1835, Jahrg. 11, p. 329.

115. Loiset, B. See 71, p. 130.

116. Hachet-Souplet, P. See 110, p. 91.

117. Knickenberg, F. Der Hund und sein "Verstand." C?then (Anhalt), P. Schettlers Erben, 1905, pp. 129 f.

118. Lang, R. Geheimnisse zur künstlichen Abrichtung der Hunde, revised edition. Augsburg and Leipsic, A. B?umer, pp. 46 f.

119. Franconi (G?rtner). See 114, pp. 326 f.

120. Tennecker, S. v. Erinnerungen aus meinem Leben. Altona, I. F. Hammerich, 1838, Vol. 1, pp. 21 f. (The name of the author is erroneously given on the title page as F. v. Tennecker.)

121. Loiset, B. See 71, p. 132.

122. D--. über die Abrichtung der kleinen Kunstpferde zu dem Z?hlen mit dem Fusse, Kopfschütteln und dgl. Zeitung für die Pferdezucht, den Pferdehandel, die Pferdekenntnis usw., Tübingen, 1804, Vol. 4, p. 51.

123. Lang, R. See 118, pp. 52 f.

124. Buffon, Cte de, et L. Daubenton. Histoire naturelle, générale et particulière. Paris, Imprimerie royale, 1753, Vol. 4, p. 169.

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Angell's Text-book of General Psychology.

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The fourth edition contains a large amount of new material, chiefly empirical in character. To offset this addition, many of the more strictly theoretical discussions have been condensed. The old material has been rearranged and many new drawings have been supplied.

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The aim of this text-book is to present, in as concrete a form as is possible, the rudiments of Logic, considered as method.

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Transcriber's Notes

Illustrations have been moved near the relevant section of the text.

Inconsistent use of spacing has been retained for page numbers followed by "f" or "ff", and for "i.e." / "i. e.", "e.g." / "e. g.", and "c.f." / "c. f." Inconsistent use of commas following "i.e.", "e.g.", and "c.f." has also been retained. Inconsistent use of single and double quotes around words and the placing of punctuation either within or external to quotes has been left as-is. Capitalization inconsistencies and grammatical errors relating to subject/verb agreement were also retained.

Inconsistent hyphenation, accents, and use of separate words have been retained for "any one" / "anyone", "arm movement" / "arm-movement", "backstep" / "back-step", "blind spot" / "blind-spot", "by the way" / "by-the-way", "counting machine" / "counting-machine", "divining rod" / "divining-rod", "ear movements" / "ear-movements", "eye movement(s)" / "eye-movement(s)", "eyebrows" / "eye-brows", "first rank" / "first-rank", "four fifths" / "four-fifths", "Hans problem" / "Hans-problem", "head jerk" / "head-jerk", "head movement(s)" / "head-movement(s)", "hoped for" / "hoped-for", "memory images" / "memory-images", "movement impulse" / "movement-impulse", "movement responses" / "movement-responses", "number concepts" / "number-concepts", "number terms" / "number-terms", "psychophysical" / "psycho-physical", "some one" / "someone", "sound waves" / "sound-waves", "thought processes" / "thought-processes", "tieraugen" / "tier-augen", "time measurements" / "time-measurements", "training process" / "training-process", "vaudeville stage" / "vaudeville-stage", "well disposed" / "well-disposed", "well known" / "well-known", "well trained" / "well-trained" "zoologist" / "zo?logist" / "Zoological" / "Zo?logical".

There is no direct reference to Table of Reference item 105 or 112 within this book.

Here is a list of the minor typographical corrections made:

Bracket removed following "1904"

"VI" changed to "IV"

Hyphen added between "September" and "Commission"

"vice versa" italicized

Double quote added after "'Hans'?"

"elasping" changed to "elapsing"

Bracket removed following "utility."

"Futhermore" changed to "Furthermore"

"wtih" changed to "with"

Comma removed after "Problems"

Comma removed after "errors"

Comma removed after "errors"

"reponse" changed to "response"

Comma changed to period after "one"

Period added after "Mr"

Comma added after "continuously"

"preceive" changed to "perceive"

Double quote added before "Inhalt"

"concrn" changed to "concern"

"of" changed to "is"

"is" changed to "of"

Period removed after "I"

"to to" replaced by "to"

Period added after "50cm"

Double quote added after "you?"

Double quote removed after "Perseverationstendenz"

Comma removed from before "continued"

"proceesses" changed to "processes"

em-dash changed to hyphen between "soixante" and "six"

"asociate" changed to "associate"

Double quote added before "streifenf?rmige"

"explantion" changed to "explanation"

Comma added after "Another"

"Ostens'" changed to "Osten's"

"baguette")" changed to "baguette)""

"role" changed to "r?le"

"taks" changed to "takes"

em-dash changed to hyphen before "lens"

"satisfactury" changed to "satisfactory"

"thought" changed to "though"

"53" changed to "73"

Apostrophe changed to comma between "84" and "85"

"detail" changed to "details"

"expectpectantly" changed to "expectantly"

Comma changed to period after "stimuli"

"suppossed" changed to "supposed"

Double quote added after "himself"

"diminshingly" changed to "diminishingly"

"acounts" changed to "accounts"

Single quote moved from before "twice," to after it

Double quote removed from before "How"

Period removed after "found?"

"af" changed to "of"

"Von" changed to "von"

Period removed after "Stuttgart"

Comma changed to period after "Botany"