criminal psychology-第126节
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of vision is
＇2＇ ber die Quelle der Sinnestuschungen。 Magazin fr Seelenkunde VIII。
＇3＇ Erklrung der Sinnestuschungen。 Wurzburg 1888。
altered and changes in size； in form； or appearance occur。'' Naturally the criminalist can not perceive slight indigestion； weak hysteria； or an inflamed area in the retina when he is examining witnesses； yet false observations like those described may have a definite influence upon the decision in a case。
If such abnormal occasions are lacking the reasons for optical illusions are of another nature。 As a rule optical illusions occur when there is an interruption in the communication between the retina； the sense of movement； and the sense of touch； or when we are prevented from reducing the changes of the retinal image to the movement of our body or of our eyes。 This reduction goes on so unconsciously that we see the idea of the object and its condition as a unit。 Again； it is indubitable that the movement of the body seems quicker when we observe it with a fixed glance than when we follow it with our eyes。 The difference may be so significant that it is often worth while； when much depends on determining the speed of some act in a criminal case； to ask how the thing was looked at。
Fechner has made a far…reaching examination of the old familiar fact that things on the ground appear to run when we ride by them rapidly。＇1＇ This fact may be compared with the other； that when you look directly into swift…moving water from a low bridge； the latter seems all of a sudden to be swimming rapidly up stream； though the water does not appear to stand still。 Here some unknown factor is at work and may exercise considerable influence on many other phenomena without our being able to observe the results。 To this class may be added the extraordinary phenomenon that from the train objects easily seem too near and hence appear smaller than they are。 It may be； however； that the converse is true and objects appear smaller； or at least shorter； and that inasmuch as we are in the habit of attributing the diminution of size in objects to their distance； we tax the latter as false。 So much is certainthat whenever we ourselves move quickly we make false judgments of size； distance； and even color。 The last may be due to the fact that during a quick passage； colors may so compose themselves； that green and red become white； and blue and yellow； green； etc。 I believe that all these illusions are increasing in connection with the spread of bicycling； inasmuch as many observations are made from the fleeting wheel and its motion tends to increase the illusions considerably。 Concerning the differences in movement Stricker＇2＇
＇1＇ Elemente die Psychophysik。 Leipzig 1889。
＇2＇ Studien ber die Sprachvorstellung。 Vienna 1880。
says： ‘‘If I lie on my back and see a bird fly in the uniformly blue heaven； I recognize the movement although I have no object with which to compare it。 This can not be explained by the variety of points on the retina which are affected； for when the bird pauses and I turn my eye； I know that it is not moving。'' The last argument is not correct。 If the bird is sitting on a branch I know； in spite of all my occipital movement； that it is quiet； but only because I perceive and observe the bird's immobility。 If； however； I lie on my back like Stricker and see above me a bird of the class that； so to speak； swim motionless in the air for minutes at a time； and if then I turn my head； I can not tell when the bird begins to move。 Here then we have no exception to the general rule and can always say that we are speaking of movement optically perceived when the rays issuing from any body progressively touch various points on the retina。 And since this occurs when we are in motion as well as when the object is in motion it happens that we can not locate the movement； we cannot say whether it be in us or in the object。
Of course； the possibility that fanciful images may appear during movement is familiar。 If I sit quietly in the forest and at some distance see a stone or a piece of wood or a little heap of dried leaves； etc。； it may be that； because of some illusion； I take it to be a rolled up hedgehog； and it may happen that I am so convinced of the nature of the object while I am looking at it that I see how the hedgehog stretches itself； sticks out its paws and makes other movements。 I remember one winter when； because of some delay； a commission on which I was serving had failed to reach a village not far from the capital。 We had gone to investigate a murder case and had found the body frozen stiff。 The oven in the room was heated and the grave…digger placed the stiff body near the oven in order to thaw it out。 We at this time were examining the place。 After a while I was instructed by the examining justice to see about the condition of the corpse； and much to my disgust； I found it sitting near the oven； bent over。 It had thawed out and collapsed。 During the subsequent obduction I saw most clearly how the corpse made all kinds of movements； and even after the section； during the dictation of the protocol； my imagination still seemed to see the corpse moving a hand or a foot。
The imagination may also cause changes in color。 Once； I saw on my desk； which stood next to a window； a great round drop of water on the left side of which the panes of the window were reflected。 （Fig。 11）。 The whole business was about a meter from my eye。 I saw it repeatedly while working and it finally occurred to me to inquire how such a great drop of water could get there。 I had sat at my desk for hours without moving。 I must have observed it if it had dropped there。 Refraining intentionally from going closer； I started； without avail； to consider how it could have
｛illust。 caption = FIG。 11。｝
come。 Some time after I examined the drop of water FIG。 11。 and found it to be an ink…blot； long ago completely dried； and bearing on its left side a few grains of white cigar ash。 I had taken these to be the image of the window； and hence； had immediately attached to it the idea of the shining； raised drop of water。 I had altogether overlooked the deep black color of the drop。 On the witness stand I would have sworn that I had seen a drop of water； even if I had known the evidence on the matter to be important。
In many cases it is possible to control the imagination； but only when it is known that the images can not be as they are seen。 Everybody is aware how a half…covered object at a distance； or objects accidentally grouped in one way or another； are taken for God knows what。 Thus once； looking from my desk to my smoking table； I saw an enormous pair of tailor's scissors half…covered by a letter。 It remained identical under a number of repeated glances。 Only when I thought vigorously that such a thing could not possibly be in my room did it disappear。 A few scales of ashes； the lower round of the match safe； the metal trimmings of two cigar boxes half… covered by a letter and reflected by the uncertain light breaking through the branches of a tree； were all that the tailor's scissors was composed of。 If there had been such a thing in the house； or if I had believed something like it to exist in the house； I should have sought no further and should have taken my oath that I had seen the thing。 It is significant that from the moment I understood the phenomenon I could not restore the image of the scissors。 How often may similar things be of importance in criminal trials！
The so…called captivation of our visual capacity plays a not unimportant part in distinguishing correct from illusory seeing。 In order to see correctly we must look straight and fully at the object。 Looking askance gives only an approximate image； and permits the imagination free play。 Anybody lost in a brown study who pictures some point in the room across the way with his eyes can easily mistake a fly； which he sees confusedly askance； for a great big bird。 Again； the type of a book seems definitely smaller if the eyes are fixed on the point of a lead pencil with a certain distance before or above the book。 And yet again； if you stand so that at an angle of about 90 degrees from the fixation point； you look at a white door in a dark wall； observing its extent in indirect vision； you will find it much higher than in direct vision。
These examples indicate how indirect vision may be corrected by later correct vision； but such correction occurs rarely。 We see something indirectly； we find it uninteresting； and do not look at it directly。 When it becomes of importance later on； perhaps enters into a criminal case； we think that we have seen the thing as it is； and often swear that ‘‘a fly is a big bird。''
There are a number of accidents which tend to complete illusion。 Suppose that the vision of a fly； which has been seen indirectly and taken for a big bird happens to be synchronous with the shriek of some bird of prey。 I combine the two and am convinced that I have seen that bird of prey。 This may increase； so much so that we may have series of sense…illusions。 I cite the example of the decorative theatrical artist； who can make the most beautiful images with a few； but very character
