Finally we will indicate the one true inner cause of the difficulty in getting the number 1 as a response. It is not easy to relax attention immediately after having just begun to concentrate. Relaxation, therefore, often occurs with a certain retardation, and the result is a belated jerk of the head.
Briefly, I would also mention a few of the more interesting introspective observations which were made in situations in which the horse responded with movements of the head for answers such as "yes" and "no", "up" and "down", etc. From the very beginning I put questions to Hans which would have to be answered by a shake of the head. It often happened that instead of indicating "0", Hans would begin tapping some number. But the wonder of it was that, in many cases, he responded properly. I knew only that I inwardly pronounced the word "null" (zero), and that I looked expectantly at the horse's head. In the case of questions to which I expected the answer "yes" or "no", I imagined myself enunciating the answer, i. e., I used motor imagery. The tests failed, the moment I employed only visual or auditory imagery, whereas, motor imagery was always effective in calling forth correct reactions.[M] When the proper response was "up" and "down" I would think of those directions in space, and likewise with "left" and "right" in which case also I would put myself in the horse's place.
While I was still ignorant of the nature of the necessary movements, the tests were successful only when I had put the question aloud or in a whisper, but never when I failed to enunciate, i. e., when I merely had the question in mind ("in idea"). But this also became possible after a little practice, although I could not then give an explanation for my success. Except in one instance, we could discern no difference between problems spoken and those merely conceived by Mr. von Osten who had had the advantage of long practice. But the one exception deserves mention. The old gentleman commissioned Hans, presumably without uttering a word, to step backward to the left. Hans thereupon responded by giving his entire repertoire, as follows: He moved his head to the right, then to the left. Then he leaped forward and repeated the same movement of the head. Hereupon he stepped backward and signified a "yes" by a movement of the head. He then lowered his head and made two leaps forward. After this performance Mr. von Osten repeated the same command aloud, and in every case Hans responded properly. Again the silent command was given and again the horse responded with the series of reactions described above, lowering his head leaping forward, etc. In this experiment, without exception, the spoken command evoked adequate reactions,—the silent command, an incorrect response. Evidently the impulse to movement was not so great with the mere conceiving of "right", "left", etc., as when the words were enunciated. It, therefore, required some practice on my part before a sufficiently strong movement-impulse became associated with the idea. All this is in no wise at variance with the fact that tests involving counting and computation were as successful when the problem was given in silence, as when it was spoken. The signs for tapping, viz.: inclination and erection of the head and body, followed the question. The question therefore became superfluous. On the other hand the signs for head-movements on the part of the horse, were given while the question was being put. I ask, which way is "upward", and at the same time I look upward. In this case therefore the question itself is not entirely insignificant.—I experienced greater difficulty in getting Hans to respond with the head-movement to the left. After much practice I was able to evoke this movement by means of giving the command aloud, but never by means of the "silent" command. Accidentally I hit upon a device by means of which I attained this end also. I asked the horse aloud "Which direction is left?",—whereupon he reacted properly; then I immediately repeated the question silently, and was successful every time. My mental attitude here was still the same as when I put the question aloud. What sort of an attitude this was, I could not, of course, have stated explicitly at the time. I could not, therefore, awaken it at will,—and if I allowed but a minute to elapse between the spoken and the silent question, the vivid after-effect (the so-called "primary memory image") soon disappeared and the test was wholly unsuccessful. Practice, however, soon helped me to overcome this last difficulty also. I believe that my inability to evoke this specific reaction on the part of the horse, lay in the unfavorable position which I assumed, for it did not allow the horse to
perceive my movements easily. For the same reason, Hans would at first indicate "no" and "zero" by turning to the right, seldom to the left.
As in the case of counting, a high degree of concentration was also necessary here, but with this difference, that here attention was directed to ideas present to the mind, ("yes", "no", etc.), whereas in the counting process attention was directed toward expected sensory impressions (i. e., the taps of the horse).
All that has been said thus far is readily understood psychologically. The following curious fact, however, is noteworthy. Hans used the head-movement to indicate two such different concepts as "zero" and "no"; it appeared therefore that in both cases he was receiving the same kind of directive. Observation proved that such was the case and the directive in question was none other than an imitation in miniature, or rather a movement anticipatory of the expected head-movement of the horse. Now, whereas the signs for "up", "down", "right", and "left" were natural expressive movements which are normally associated with the corresponding concepts, this cannot be said to be true of "no" and "zero". My laboratory observations (see [page 107]) lead me to conclude that the movements, by means of which the concepts "no" and "zero" are naturally expressed, are quite different; and neither of these corresponds to the signs for "zero" and "no" which the questioner involuntarily gave to Hans. What was the genesis of these unnatural forms of expression? If we might assume that the questioner always had in mind the movement he awaited on the part of the horse, and never thought of "zero" or "no", then the contradiction would solve itself. But I must deny decidedly that I ever thought of the movements of the horse's head, and Mr. Schillings, whom I questioned on this point, agreed with me in this, in so far as his own mental processes were concerned. I can see nothing for it but that in this instance the expressive movements normally connected with the concepts "zero" and "no" have been replaced by other forms, without the questioner becoming aware of it. That such displacements may occur, has been shown by the tests described on pages [107] to [112]. That they did occur in this instance may be concluded from the following observation. In responding to me, as well as to Mr. Schillings, Hans always moved his head first to the left, then to the right, never in the opposite order. That this was not a peculiarity of the horse, but must be ascribed to the signs which were given him, is shown by the possibility of inverting the order under experimental control ([page 77]). Frequently Mr. Schillings and I had seen the horse respond to his master by means of such head-movements, and the order was always, without exception, the one mentioned. It must be assumed therefore that the horse's movement, which we so often noticed, made such an impression upon us, that afterwards it was regularly reproduced on our part quite unconsciously, so that Mr. Schillings never, and I only after a long time, became aware of the whole process.
In closing, just a word as to the discovery of our own movements. I soon noticed that every pronounced raising of the head or trunk brought about an interruption in the horse's response. But only by observing the final movement in the case of Mr. von Osten did I discover that I, too, performed a slight erection of the head. Observation of others was less difficult than the observation of one's own movements. As in the case of all other signs given to the horse, these movements were so slight that they were prone to escape notice even though one's whole attention were concentrated upon their detection. I also questioned whether in my attempts to disturb the horse by means of loud calls, it were really the call or some simultaneous involuntary movement which was the true cause of the interruption. The doubt was justified, for when I finally learned to cry out vehemently without making the slightest move, all my crying was in vain. Also it had seemed to me at first as if I were able to induce the horse to rear, not only by means of the proper sign or movement, but also by a mere command, but I found later that in every case there was always some movement, were it ever so slight. Finally I tried to simulate voluntarily the oft-mentioned involuntary jerks of the head. Although it is not very difficult to execute them at will with almost the same minuteness as when they were performed involuntarily, I still did not succeed in getting a series of such jerks of equal fineness throughout. In spite of (and partly on account of) the most concentrated attention, there would be from time to time a jerk of somewhat greater extent and energy. As soon as the movement had been executed, I was able to form a good judgment as to its relative extent, but I was unable to regulate the impulse beforehand.
With the following comment the chapter will be concluded. Introspections are necessarily subjective in character. If they are to possess general validity, they must be borne out by evidence furnished by others—and this to a greater extent than is necessary for other forms of observation. It was hardly possible to get corroboration from the other persons who had worked with Hans, for, although some of them were excellent observers of external natural phenomena, few of them had had the necessary amount of practice in introspection. The necessary confirmation, however, was had in laboratory tests, which we shall presently describe.
FOOTNOTES:
[M] Thus it is possible to think of the word "no" in three different ways. I may get a visual image of the written or printed word, or the auditory image of the word as spoken by another person, or finally I might think of it in terms of images of the sensations of movement which would arise if I myself were to enunciate or write the word. And so, in like manner, I could think of any other word in terms of either visual or auditory or motor imagery. In all probability the auditory and motor always occur together,[6] but still it is possible to make the one or the other predominate.