It appears that the imagery of most persons is a mixture of auditory-motor and visual elements, with a predominance of one or the other kind. Individuals who utilize almost exclusively the visual (as does the author, as a rule), are rare. But rarer still is the pronounced motor type.
CHAPTER IV
LABORATORY TESTS
The tests which are to be briefly reported here, were begun in November, 1904, and were carried out at the Psychological Institute of the University of Berlin. The purpose was twofold: first, to discover whether the expressive movements noted in Mr. von Osten, Mr. Schillings, and others, were to be regarded as typical and to be found in the majority of individuals,—and secondly, to ascertain in how far the psychical processes which I had noted in my own case and which I believed to lie at bottom of these movements, were paralleled in, and confirmed by, the introspections of others. The effort was made to make the experimental conditions as nearly as possible like those under which the horse had worked. The affective atmosphere which colored the situations in which the horse took part, could not, of course, be transferred, but this was in some respects an advantage. One person undertook the rôle of questioner, another—myself—that of the horse. The experiments fall into three groups, corresponding to the types of the horse's reactions: 1, tests in counting and computation; 2, tests in space reactions; 3, tests in fetching or designating objects.
In the experiments in counting and computation, the questioner, standing at my right, thought with a high degree of concentration of some number (usually between 1 and 10, but sometimes also as high as 100), or of some simple problem in addition. Then I would begin to tap,—but in human fashion with my right hand, rather than with my foot—and continued until I believed that I had perceived a final signal. I thus tested, all in all, twenty-five persons, of every age and sex (including children of five and six years), differing also in nationality and occupation. None of them was aware of the purpose of the experiments. It could not escape them, to be sure, that they were being watched. It was also evident to them that the things noted were certain tensions and movements; but none of my subjects discovered what the particular phenomena were that I was looking for. Only in a few isolated instances did they report that they were conscious of any movements on their part. With the exception of two persons, they all made the same involuntary movements which were described in [chapter II], the most important of which was the sudden slight upward jerk of the head when the final number was reached. It was at once evident that the direction of this jerk depended upon the position which one had asked the subject to assume at the beginning of the test, the direction changing whenever the position was changed. Thus, if the subject stood with head bowed—the body either being held erect or likewise bowed,—then release of tension would be expressed physically by an upward jerk. (Occasionally the entire trunk is slightly raised, so that it was possible to observe this physical reaction when standing behind the subject). If the subject had bent his head backward, the "psychological moment" was marked by a forward movement, (although under certain conditions the head was, in such a case, observed to bend still farther backward). If during the tests the head was bent slightly to the right, then the reaction was expressed in a movement toward the left, and vice versa, if it had been on the left, it was bent to the right. If the subject had been bending his head forward and to the right, he then raised it upward and to the left, etc. In all of these changes of position I noticed an intermediate posture which, to be sure, it was not always an easy matter to discover,—viz.: an upright position in which there was discernible no manner of head-movement or only a slight tremor. If the subject was lying on his back with his head supported, then there was noticeable a very slight movement to one side. In this same way a number of other positions were tested in order to discover for each the characteristic movement expressive of release of tension. It would therefore appear that the raising of the questioner's head, which served as the signal for stopping for Mr. von Osten's horse, was but one instance of a general law which may perhaps be stated thus: The release of muscular tension which occurs with the cessation of psychic tension, tends to bring about that position of the head (and body) which, at the time, represents the slightest amount of muscular strain.—These movements seldom were pronounced enough to be compared to motion through a distance of one millimeter, in a very few cases only did they attain to the magnitude of one or two millimeters: I failed to note them entirely, however, in only two individuals, two scientific men whose mode of thought was always the most abstract, and one of these was, in spite of repeated attempts, unable to elicit any response whatever on the part of the horse.
In the cases of the more suitable subjects I was able to indicate not only the number they had in mind, but also the divisions in which the number was thought, thus 12 as 5 and 5 and 2, or the same number as 2 and 5 and 5, and I was also able to determine the addends in the addition—i. e., whether the problem had been conceived as 3+2=5 or as 2+3=5. It frequently happened that in the beginning I would sometimes mistake these subdivisions, which were recognizable by the less pronounced jerks, for the final number. Thus I would often respond with 4 instead of 8, or 3 instead of 9, or with 3 when the problem was 3+2, just as Hans had so often done. In these tests, too, the difficulty of getting the number 1, as well as the larger numbers, came to light. Thus three times in succession 17 was indicated as 4, as 9, and as 17. But after some practice I was able to give numbers as high as 58 and 96. The frequency of the errors of one unit too many and of one unit too few is also noticeable in these tests.
We also found desirable corroboration, by trustworthy subjects, of the introspective observations of the author, which were reported in [Chapter III], with regard to the significance of concentration and the curve of attention. It is hardly necessary to mention that no attempts were made to influence the subjects in their accounts by asking suggestive questions. The most valuable feature about these tests was that the mute horse had now been replaced, as it were, by an animal capable of speech, and that it was now possible to follow the same process both from within and from without. Two illustrations may be welcome. The one who took the part of the horse gave three taps and made the following entry: "At 3 I saw a slight upward jerk of the head on the part of the questioner". The questioner however had thought of 4, and made the following note, without knowledge of the other's entry: "I was aware of extreme tension, so that it was impossible for me to get beyond 3". Or again, the 'horse', reacting to a movement on the part of the questioner, stopped at 3, but the latter, having intended to obtain 2, made the following entry: "I noted clearly that I ceased thinking of the number too late, and did not put on the brakes, as it were, until I had arrived at 3". We see that errors here were entirely the fault of the questioner, just as had been the case in the tests with Hans. (See [page 151f.]).
In a second group of experiments I asked a subject to fix his mind upon certain concepts, such as "up", or "down", "right" or "left", "yes" or "no", and others, in any order he pleased, but with the greatest possible degree of concentration. The subject each time had the choice of four or six concepts, and he was told to think of one of them at the signal "Now!". How he was to 'think' the concept was left entirely to him. He was also told to interpolate the series with a 'blank', that is, to think of nothing at all. Standing opposite the subject, I tried to guess at the mental content of the person's mind, on the basis of expressive movements. Sometimes I reacted by shaking or nodding the head, etc., just as Hans had done, but as a rule I was content to say the word which I thought the subject had in mind. With twelve subjects (a total of 350 tests) I made an average of 73% correct responses, and in the more favorable cases I attained even 90 to 100% correct responses. Very slight involuntary movements of the head and eyes, which showed but little individual variation, and always occurred when the subject began to fix upon the concept, were the signs which I used as cues. As in the case of the movements expressive of the release of tension, which I discussed above, these movements, too, occurred without the subject being aware of them, (except in those rare cases in which they had once or twice been especially pronounced). Indeed, it was very difficult and in some cases almost impossible for those persons whom I had initiated into the secret, to inhibit them voluntarily. "Up" and "down", "right" and "left", were expressed by movements of head or eye in those directions, "forward" by a forward movement of the head, "back" by a corresponding movement. "Yes" was accompanied by a slight nod of the head; "no" by two to four rapid turnings of the head to either side.[N] "Zero" was expressed by a movement of the head describing an oval in the air. Indeed, it was even possible to discover whether the subject had conceived of a printed or a written zero, for the characteristics of both were revealed in the head-movements. I was able later to verify this graphically. With Ch. as subject, I made 70% correct interpretations in a total of 20 tests; with von A. as subject, 72% in a total of 25 tests. And finally I was able to interpret the signs without any errors at all. It was not absolutely necessary to look directly at the subject's face. Even though I focussed a point quite to one side, so that the image of the subject's face would fall upon a peripheral portion of my retina, I still was able to make 89% correct interpretations in a total of 20 tests.—This is not astonishing after all, when we recall that the periphery of the retina possesses a relatively high sensitivity for movement impressions, although its chromatic sensitivity is very low.[O]