In all these cases psychic influences which have arisen without external stimulus have directly inoculated the mind, thereby evading the criticism of the "ego" or of personal consciousness.
"Suggesting" signifies, therefore, to inoculate the mind of a person more or less directly with ideas, feelings, emotions, and other psychical states, in order that no opportunity is left for criticism and consideration. Under "suggestion," on the other hand, is to be understood that sort of direct inoculation of the mind of an individual with ideas, feelings, emotions, and other psychophysical states which evade his "ego," his personal self-consciousness, and his critical attitude.
Now and then, especially in the French writers, one will find besides "suggestion" the term "psychic contagion," under which, however, nothing further than involuntary imitation is to be understood (compare A. Vigouroux and P. Juquelier, La contagion mentale, Paris, 1905). If one takes up the conception of suggestion in a wider sense, and considers by it the possibility of involuntary suggestion in the way of example and imitation, one will find that the conceptions of suggestion and of psychic contagion depend upon each other most intimately, and to a great extent are not definitely to be distinguished from each other. In any case, it is to be maintained that a strict boundary between psychic contagion and suggestion does not always exist, a fact which Vigouroux and Juquelier in their paper have rightly emphasized.
2. The Subtler Forms of Suggestion[152]
In one very particular respect hypnotism has given us a lesson of the greatest importance to psychology: it has proved that special precautionary measures must be taken in planning psychological experiments. The training of hypnotics has thrown light on this source of error. A hypnotizer may, often without knowing it, by the tone of his voice or by some slight movement cause the hypnotic to exhibit phenomena that at first could only be produced by explicit verbal suggestion, and that altogether the signs used by the hypnotizer to cause suggestions may go on increasing in delicacy. A dangerous source of error is provided by the hypnotic's endeavor to divine and obey the experimenter's intentions. This observation has also proved useful in non-hypnotic experiments. We certainly knew before the days of hypnotism that the signs by which A betrays his thoughts to B may gradually become more delicate. We see this, for example, in the case of the schoolboy, who gradually learns how to detect from the slightest movement made by his master whether the answer he gave was right or not. We find the same sort of thing in the training of animals—the horse, for instance, in which the rough methods at first employed are gradually toned down until in the end an extremely slight movement made by the trainer produces the same effect that the rougher movements did originally. But even if this lessening in the intensity of the signals exists independently of hypnosis, it is the latter that has shown us how easily neglect of this factor may lead to erroneous conclusions being drawn. The suggestibility of the hypnotic makes these infinitesimal signals specially dangerous in his case. But when once this danger was recognized, greater attention was paid to this source of error in non-hypnotic cases than before. It is certain that many psychological experiments are vitiated by the fact that the subject knows what the experimenter wishes. Results are thus brought about that can only be looked upon as the effects of suggestion; they do not depend on the external conditions of the experiment but on what is passing in the mind of the subject.
An event which at the time of its occurrence created a considerable commotion (I refer to the case of Clever Hans), will show how far we may be led by neglecting the above lesson taught us by hypnotism. If the Berlin psychologist Stumpf, the scientific director of the committee of investigation, had but taken into consideration the teachings of hypnotism, he would never have made the fiasco of admitting that the horse, Clever Hans, had been educated like a boy, not trained like an animal.
Clever Hans answered questions by tapping his hoof on the stage; and the observers, more particularly the committee presided over by Stumpf, believed that answers tapped out were the result of due deliberation on the part of the horse, exactly as spiritists believe that the spirits hold intelligent intercourse with them by means of "raps." One tap denoted a, two taps b, three taps c, etc.; or, where numbers were concerned, one tap signified 1, two taps 2, etc. In this way the animal answered the most complicated questions. For instance, it apparently not only solved such problems as 3 times 4 by tapping 12 times, and 6 times 3 by tapping 18 times, but even extracted square roots, distinguished between concords and discords, also between ten different colors, and was able to recognize the photographs of people; altogether, Clever Hans was supposed to be at that time about upon a level with fifth-form boys (the fifth form is the lowest form but one in a German gymnasium). After investigating the matter, Stumpf and the members of his committee drew up the following conjoint report, according to which only one of two things was possible—either the horse could think and calculate independently, or else he was under telepathic, perhaps occult, influence:
The undersigned met together to decide whether there was any trickery in the performance given by Herr v. Osten with his horse, i.e., whether the latter was helped or influenced intentionally. As the result of the exhaustive tests employed, they have come to the unanimous conclusion that, apart from the personal character of Herr v. Osten, with which most of them were well acquainted, the precautions taken during the investigation altogether precluded any such assumption. Notwithstanding the most careful observation, they were well unable to detect any gestures, movements, or other intimations that might serve as signs to the horse. To exclude the possible influence of involuntary movements on the part of spectators, a series of experiments was carried out solely in the presence of Herr Busch, councilor of commissions. In some of these experiments, tricks of the kind usually employed by trainers were, in his judgment as an expert, excluded. Another series of experiments was so arranged that Herr v. Osten himself could not know the answer to the question he was putting to the horse. From previous personal observations, moreover, the majority of the undersigned knew of numerous individual cases in which other persons had received correct answers in the momentary absence of Herr v. Osten and Herr Schillings. These cases also included some in which the questioner was either ignorant of the solution or only had an erroneous notion of what it should be. Finally, some of the undersigned have a personal knowledge of Herr v. Osten's method, which is essentially different from ordinary "training" and is copied from the system of instruction employed in primary schools. In the opinion of the undersigned, the collective results of these observations show that even unintentional signs of the kind at present known were excluded. It is their unanimous opinion that we have here to deal with a case that differs in principle from all former and apparently similar cases; that it has nothing to do with "training" in the accepted sense of the word, and that it is consequently deserving of earnest and searching scientific investigation. Berlin, September 12, 1904. [Here follow the signatures, among which is that of Privy Councilor Dr. C. Stumpf, university professor, director of the Psychological Institute, member of the Berlin Academy of Sciences.]
Anyone who has done critical work in the domain of hypnotism after the manner insisted on by the Nancy school cannot help considering Stumpf's method of investigation erroneous from the very outset. A first source of error that had to be considered was that someone present—it might have been Herr v. Osten or it might have been anyone else—unintentionally had given the horse a sign when to stop tapping. It cannot be considered sufficient, as stated in Stumpf's report, that Herr v. Osten did not know the answer; no one should be present who knows it. This is the first condition to be fulfilled when making such experiments. Anybody who has been engaged in training hypnotized subjects knows that these insignificant signs constitute one of the chief sources of error. Some of the leading modern investigators in the domain of hypnotism—Charcot and Heidenhain, for instance—were misled by them at the time they thought they had discovered new physical reflexes in hypnosis. But in 1904, by which time suggestion had been sufficiently investigated to prevent such an occurrence, a psychologist should not have fallen into an error that had been sufficiently made more than twenty years previously. But the main point is this: signs that are imperceptible to others are nevertheless perceived by a subject trained to do so, no matter whether that subject be a human being or an animal.