按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
ds； travellers； etc。； do not hear the pounding of their various habitual environmental noises； but they perceive the slightest call； and everybody observes the considerable murmur of the world； the sum of all distant noises； only in the silence of the night that misses it。
Illusions of direction of sound are very common。 It is said that even animals are subject to them； and everybody knows how few human beings can distinguish the source and direction of street music； a rolling wagon； or a ringing bell。 Even when long practice enables one to determine direction with correctness； an accidental event； perhaps the weather； especial sounds； a different grouping of individuals on the street； may result in serious mistakes。 I tried to learn to judge from my office…desk whether the ring of the horse… car came from above or below。 I succeeded so well that I could not understand how it was difficult not to learn the difference； and yet I failed many a time altogether in judgment。 The reason for it I do not know。
All these enumerated circumstances must show how very uncertain all acoustic perceptions are； and how little they may be trusted if they are not carefully tested under similar conditions； and ifwhat is most importantthey are not isolated。 We are here led back
＇1＇ Max Meyer： Zur Theorie der Geruschempfindungen。 Leipzig 1902。
to the old principle that every observation is not proof but means of proof； and that it may be trusted only when it is confirmed by many parallel actions which are really consistent。 That even after that mistakes are possible； is true； but ‘‘after that'' is when we have done all that lies within human power。
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 d