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Section 101. (4) Illusions of Touch.

The high standing of the sense of touch which make it in certain directions even the organ of control of the sense of sight, is well known, and Condillac's historic attempt to derive all the senses from this one is still plausible. If what is seen is to be seen accurately there is automatic resort to the confirmatory aid of the sense of touch, which apprehends what the eye has missed. Hence we find many people touching things, whose vision is not altogether reliable— i. e., people of considerable age, children unpracticed in seeing, an uneducated people who have never learned to see quickly and comprehensively. Moreover, certain things can be determined only by touching, i. e., the fineness of papers, cloth, etc., the sharpness or pointedness of instruments, or the rawness of objects. Even when we pat a dog kindly we do so partly because we want to see whether his skin is as smooth and fine as the eye sees it; moreover, we want to test the visual impression by that of touch.

But important and reliable as the sense of touch is, it is nevertheless not to be trusted when it is the sole instrument of perception. We must never depend on the testimony of a witness based entirely on perceptions by touch, and the statements of a wounded person concerning the time, manner, etc., of his wound are unreliable unless he has also seen what he has felt. We know that most knife and bullet wounds, i. e., the most dangerous ones, are felt, in the first instance, as not very powerful blows. Blows on the extremities are not felt as such, but rather as pain, and blows on the head are regularly estimated in terms of pain, and falsely with regard to their strength. If they were powerful enough to cause unconsciousness they are said to have been very massive, but if they have not had that effect, they will be described by the most honest of witnesses as much more powerful than they actually were. Concerning the location of a wound in the back, in the side, even in the upper arm, the wounded person can give only general indications, and if he correctly indicates the seat of the wound, he has learned it later but did not know it when it occurred. According to Helmholtz,

practically all abdominal sensations are attributed to the anterior abdominal wall. Now such matters become of importance when an individual has suffered several wounds in a brawl or an assault and wants to say certainly that he got wound A when X appeared, wound B when Y struck at him, etc. These assertions are almost all false because the victim is likely to identify the pain of the moment of receiving the wound with its later painfulness. If, for example, an individual has received a rather long but shallow knife wound and a deep stab in the back, the first will cause him very considerable burning sensation, the latter only the feeling of a heavy blow. Later on, at the examination, the cut has healed and is no longer painful; the dangerous stab which may have reached the lung, causes pain and great difficulty in breathing, so that the wounded man assigns the incidence of the stab to the painful sensation of the cut, and conversely.

Various perceptions of victims on receiving a wound are remarkable, and I have persuaded a police surgeon of considerable learning and originality to collect and interpret his great mass of material. It is best done by means of tabulation, accurate description of wounds according to their place, size, form, and significance, the statement of the victim concerning his feeling at the moment of receiving the wound, the consequences of healing, and at the end explanatory observations concerning the reasons for true or incorrect sensations of the victim. As this work is to have only psychological value it is indifferent whether the victim is veracious or not. What we want to know is what people say about their perception. The true and the false will distinguish themselves automatically, the material being so rich, and the object will be to compare true subjective feelings with true subjective deeds. Perhaps it may even be possible to draw generalizations and to abstract certain rules.

There are many examples of the fact that uncontrolled touch leads to false perceptions. Modern psychophysics has pointed to a large group of false perceptions due to illusions of pressure, stabs, or other contact with the skin. The best known, and criminalistically most important experiments, are those with open compasses. Pressed on the less sensitive parts of the body, the back, the thigh, etc., they are always felt as one, although they are quite far apart. The experiments of Flournoy, again, show how difficult it is to judge weights which are not helped by the eye's appreciation of their form and appearance. Ten objects of various forms were judged by fifty

people for their weight; only one discovered that they all had the same weight.

Similarly, mere touch can not give us proper control over the organs of the body. Sully says that in bed we may voluntarily imagine that a leg has a position quite different from that it really has. Let me cite some similar examples from my "Manual for Investigating Judges." If we take a pea between the thumb and the index finger, we feel the pea simply, although its tactile image comes to us through two fingers, i. e., double. If now we cross the third finger over the fourth and hold the pea between the ends of these two fingers, we feel it to be double because the fingers are not in their customary positions and hence give double results. From one point of view this double feeling is correct, but when we touch the pea naturally, experience helps us to feel only one pea. Another example consists in crossing the hands and turning them inward and upward, so that the left fingers turn to the left and the right fingers to the right. Here the localization of the fingers is totally lost, and if a second person points to one of the fingers without touching it, asking you to lift it, you regularly lift the analogous finger of the other hand. This shows that the tactile sense is not in a very high stage of development, since it needs, when unhelped by long experience, the assistance of the sense of sight. Perceptions through touch alone, therefore, are of small importance; inferences are made on the basis of few and more coarse characteristic impressions.

This is shown by a youthful game we used to play. It consisted of stretching certain harmless things under the table—a soft piece of dough, a peeled, damp potato stuck on a bit of wood, a wet glove filled with sand, the spirally cut rind of a beet, etc. Whoever got one of these objects without seeing it thought he was holding some disgusting thing and threw it away. His sense of touch could present only the dampness, the coldness, and the motion, i. e., the coarsest traits of reptilian life, and the imagination built these up into a reptile and caused the consequent action. Foolish as this game seems, it is criminalistically instructive. It indicates what unbelievable illusions the sense of touch is capable of causing. To this inadequacy of the tactile imagination may be added a sort of transferability of certain touch sensations. For example, if ants are busy near my seat I immediately feel that ants are running about under my clothes, and if I see a wound or hear it described, I often feel pain in the analogous place on my own body. That this may lead to considerable illusion in excitable witnesses is obvious.

Finally, this dependence of the sense of touch may be supplemented by the fact that it is counted only relatively, and its value varies with the individual. We find the cellar warm in winter and cold in summer, because we only feel the difference with the outer air, and when we put one hand in hot, and the other in cold water, and then put both in tepid water one finds the tepid water cold, the other warm. The record of tactile sensations is frequent in our protocols and requires constant consideration of the sense's unreliability.

Diseased conditions are of course to be referred to the physician. I need only mention that slight poisonings by means of chloroform, morphine, atropine, daturine, decrease, and that strychnine increases the sensitivity of the touch organ.