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Section 36. (a) General Considerations.

The criminalist studies the physiological psychology[1] of the senses and their functions, in order to ascertain their nature, their influence upon images and concepts, their trustworthiness, their reliability and its conditions, and the relation of perception to the object. The question applies equally to the judge, the jury, the witness, and the accused. Once the essence of the function and relation of sense-perception is understood, its application in individual cases becomes easy.

The importance of sense-perception need not be demonstrated. "If we ask," says Mittermaier, "for the reason of our conviction of the truth of facts even in very important matters, and the basis of every judgment concerning existence of facts, we find that the evidence of the senses is final and seems, therefore, the only true source of certainty."

There has always, of course, been a quarrel as to the objectivity and reliability of sense-perception. That the senses do not lie, "not because they are always correct, but because they do not judge," is a frequently quoted sentence of Kant's; the Cyrenaics have already suggested this in asserting that pleasure and pain alone are indubitable. Aristotle narrows the veracity of sensation to its essential content, as does Epicurus. Descartes, Locke and Leibnitz have suggested that no image may be called, as mere change of feeling, true or false. Sensationalism in the work of Gassendi, Condillac, and Helvetius undertook for this reason the defense of the senses against the reproach of deceit, and as a rule did it by invoking the infallibility of the sense of touch against the reproach of the contradictions in the other senses. Reid went back to Aristotle in distinguishing specific objects for each sense and in assuming the truth of each sense within its own field.

That these various theories can be adjusted is doubtful, even if, from a more conservative point of view, the subject may be treated quantitatively. The modern quantification of psychology was begun by Herbart, who developed a mathematical system of psychology by introducing certain completely unempirical postulates concerning the nature of representation and by applying certain simple premises in all deductions concerning numerical extent. Then came Fechner, who assumed the summation of stimuli. And finally these views were determined and fixed by the much-discussed Weber's Law, according to which the intensity of the stimulus must increase in the proportion that the intensity of the sensation is to increase; i. e., if a stimulus of 20 units requires the addition of 3 before it can be perceived, a stimulus of 60 units would require the addition of 9. This law, which is of immense importance to criminalists who are discussing the sense-perceptions of witnesses, has been thoroughly and conclusively dealt with by A. Meinong.[2]

"Modern psychology takes qualities perceived externally to be in themselves subjective but capable of receiving objectivity through

our relation to the outer world.... The qualitative character of our sensory content produced by external stimuli depends primarily on the organization of our senses. This is the fundamental law of perception, of modern psychology, variously expressed, but axiomatic in all physiological psychology."[3] In this direction Helmholtz[4] has done pioneer work. He treats particularly the problem of optics, and physiological optics is the study of perception by means of the sense of sight. We see things in the external world through the medium of light which they direct upon our eyes. The light strikes the retina, and causes a sensation. The sensation brought to the brain by means of the optic nerve becomes the condition of the representation in consciousness of certain objects distributed in space.... We make use of the sensation which the light stimulates in the mechanism of the optic nerve to construct representations concerning the existence, form, and condition of external objects. Hence we call images perceptions of sight. (Our sense-perception, according to this theory, consists, therefore, entirely of sensations; the latter constitute the stuff or the content from which the other is constructed). Our sensations are effects caused in our organs, externally, and the manifestation of such an effect depends essentially upon the nature of the apparatus which has been stimulated.

There are certain really known inferences, e. g., those made by the astronomer from the perspective pictures of the stars to their positions in space. These inferences are founded upon well-studied knowledge of the principles of optics. Such knowledge of optics is lacking in the ordinary function of seeing; nevertheless it is permissible to conceive the psychical function of ordinary perception as unconscious inferences, inasmuch as this name will completely distinguish them from the commonly so-called conscious inferences.

The last-named condition is of especial importance to us. We need investigation to determine the laws of the influence of optical and acoustical knowledge upon perception. That these laws are influential may be verified easily. Whoever is ignorant, e. g., that a noise is reflected back considerably, will say that a wagon is turning from the side from which the noise comes, though if he knows the law, if he knows that fact, his answer would be reversed. So, as every child knows that the reflection of sound is frequently deceptive, everybody who is asked in court will say that he believes the wagon

to be on the right side though it might as well have been on the left. Again, if we were unaware that light is otherwise refracted in water than in air we could say that a stick in the water has been bent obtusely, but inasmuch as everybody knows this fact of the relation of light to water, he will declare that the stick appears bent but really is straight.

From these simplest of sense-perceptions to the most complicated, known only to half a dozen foremost physicists, there is an infinite series of laws controlling each stage of perception, and for each stage there is a group of men who know just so much and no more. We have, therefore, to assume that their perceptions will vary with the number and manner of their accomplishments, and we may almost convince ourselves that each examinee who has to give evidence concerning his sense-perception should literally undergo examination to make clear his scholarly status and thereby the value of his testimony. Of course, in practice this is not required. First of all we judge approximately a man's nature and nurture and according to the impression he makes upon us, thence, his intellectual status. This causes great mistakes. But, on the other hand, the testimony is concerned almost always with one or several physical events, so that a simple relational interrogation will establish certainly whether the witness knows and attends to the physical law in question or not. But anyway, too little is done to determine the means a man uses to reach a certain perception. If instantaneous contradictions appear, there is little damage, for in the absence of anything certain, further inferences are fortunately made in rare cases only. But when the observation is that of one person alone, or even when more testify but have accidentally the same amount of knowledge and hence have made the same mistake, and no contradiction appears, we suppose ourselves to possess the precise truth, confirmed by several witnesses, and we argue merrily on the basis of it. In the meantime we quite forget that contradictions are our salvation from the trusting acceptance of untruth— and that the absence of contradiction means, as a rule, the absence of a starting point for further examination.

For this reason and others modern psychology requires us to be cautious. Among the others is the circumstance that perceptions are rarely pure. Their purity consists in containing nothing else than perception; they are mixed when they are connected with imaginations, judgments, efforts, and volitions. How rarely a perception is pure I have already tried to show; judgments almost

always accompany it. I repeat too, that owing to this circumstance and our ignorance of it, countless testimonies are interpreted altogether falsely. This is true in many other fields. When, for example, A. Fick says: "The condition we call sensation occurs in the consciousness of the subject when his sensory nerves are stimulated," he does not mean that the nervous stimulus in itself is capable of causing the condition in question. This one stimulus is only a single tone in the murmur of countless stimuli, which earlier and at the same time have influenced us and are different in their effect on each man. Therefore, that single additional tone will also be different in each man. Or, when Bernstein says that "Sensation, i. e., the stimulation of the sensorium and the passage of this stimulation to the brain, does not in itself imply the perception of an object or an event in the external world," we gather that the objectivity of the perception works correctively not more than one time out of many. So here again everything depends upon the nature and nurture of the subject.

Sensations are, according to Aubert, still more subjective. "They are the specific activity of the sense organs, (not, therefore, passive as according to Helmholtz, but active functions of the sense organs). Perception arises when we combine our particular sensations with the pure images of the spirit or the schemata of the understanding, especially with the pure image of space. The so-called ejection or externalization of sensations occurs only as their scheme and relation to the unity of their object."

So long as anything is conceived as passive it may always recur more identically than when it is conceived as active. In the latter case the individuality of the particular person makes the perception in a still greater degree individual, and makes it almost the creature of him who perceives. Whether Aubert is right or not is not our task to discover, but if he is right then sense-perception is as various as is humanity. The variety is still further increased by means of the comprehensive activity which Fischer[5] presupposes. "Visual perception has a comprehensive or compounding activity. We never see any absolute simple and hence do not perceive the elements of things. We see merely a spatial continuum, and that is possible only through comprehensive activity—especially in the case of movement in which the object of movement and the environment must both be perceived." But each individual method of "comprehension" is different. And it is uncertain whether this

is purely physical, whether only the memory assists (so that the attention in biased by what has been last perceived), whether imagination is at work or an especial psychical activity must be presupposed in compounding the larger elements. The fact is that men may perceived an enormous variety of things with a single glance. And generally the perceptive power will vary with the skill of the individual. The narrowest, smallest, most particularizing glance is that of the most foolish; and the broadest, most comprehensive, and comparing glance, that of the most wise. This is particularly noticeable when the time of observation is short. The one has perceived little and generally the least important; the other has in the same time seen everything from top to bottom and has distinguished between the important and the unimportant, has observed the former rather longer than the latter, and is able to give a better description of what he has seen. And then, when two so different descriptions come before us, we wonder at them and say that one of them is untrue.[6]

The speed of apperception has been subjected to measurement by Auerbach, Kries, Baxt, von Tigerstedt and Bergqvist, Stern, Vaschide, Vurpass, etc. The results show 0.015 to 0.035 seconds for compounded images. Unfortunately, most of these experiments have brought little unanimity in the results and have not compared, e. g., the apperception-times of very clever people with those of very slow and stupid ones. In the variety of perception lies the power of presentation (in our sense of the term). In the main other forces assist in this, but when we consider how the senses work in combination we must conclude that they determine their own forms. "If we are to say that sense experience instructs us concerning the manifoldness of objects we may do so correctly if we add the scholium that many things could not be mentioned without synthesis." So Dörner writes. But if we approach the matter from another side, we see how remarkable it is that human perceptions can be compared at all. Hermann Schwarz says "According to the opinion of the physicists we know external events directly by means of the organs, the nerves of which serve passively to support consciousness in the perception of such events. On the contrary, according to the opinion of most physiologists, the nerve fibers are active in the apprehension of external events, they modify it, alter it until it is well nigh unrecognizable, and turn it over to consciousness only after the original process has undergone still another transformation

into new forms of mechanical energy in the ganglion cells of the outer brain. This is the difference between the physical theory of perception and the physiological."

In this connection there are several more conditions pertaining to general sense-perception. First of all there is that so-called vicariousness of the senses which substitutes one sense for another, in representation. The actual substitution of one sense by another as that of touch and sight, does not belong to the present discussion. The substitution of sound and sight is only apparent. E. g., when I have several times heard the half-noticed voice of some person without seeing him, I will imagine a definite face and appearance which are pure imagination. So again, if I hear cries for help near some stream, I see more or less clearly the form of a drowning person, etc. It is quite different in touching and seeing; if I touch a ball, a die, a cat, a cloth, etc., with my eyes closed, then I may so clearly see the color of the object before me that I might be really seeing it. But in this case there is a real substitution of greater or lesser degree.

The same vicariousness occurs when perception is attributed to one sense while it properly belongs to another. This happens particularly at such times when one has not been present during the event or when the perception was made while only half awake, or a long time ago, and finally, when a group of other impressions have accompanied the event, so that there was not time enough, if I may say so, properly to register the sense impression. So, e. g., some person, especially a close friend, may have been merely heard and later quite convincingly supposed to have been seen. Sensitive people, who generally have an acuter olfactory sense than others, attach to any perceived odor all the other appropriate phenomena. The vicariousnesses of visual sensations are the most numerous and the most important. Anybody who has been pushed or beaten, and has felt the blows, will, if other circumstances permit and the impulse is strong enough, be convinced that he has seen his assaulter and the manner of the assault. Sometimes people who are shot at will claim to have seen the flight of the ball. And so again they will have seen in a dark night a comparatively distant wagon, although they have only heard the noise it made and felt the vibration. It is fortunate that, as a rule, such people try to be just in answering to questions which concern this substitution of one sense-perception for another. And such questions ought to be urgently put. That a false testimony can cause significant errors is as obvious as the fact

that such substitutions are most frequent with nervous and imaginative persons.

Still more significant is that characteristic phenomenon, to us of considerable importance, which might be called retrospective illumination of perception. It consists in the appearance of a sense-perception under conditions of some noticeable interruption, when the stimulus does not, as a rule, give rise to that perception. I cite a simple example in which I first observed this fact. Since I was a child there had been in my bed-room a clock, the loud ticking of which habit of many years prevented my hearing. Once, as I lay awake in bed, I heard it tick suddenly three times, then fall silent and stop. The occurrence interested me, I quickly got a light and examined the clock closely. The pendulum still swung, but without a sound; the time was right. I inferred that the clock must have stopped going just a few minutes before. And I soon found out why: the clock is not encased and the weight of the pendulum hangs free. Now under the clock there always stood a chair which this time had been so placed as to be inclined further backward. The weight followed that inclination and so the silence came about.

I immediately made an experiment. I set the clock going again, and again held the weight back. The last beats of the pendulum were neither quicker nor slower, nor louder or softer than any others, before the sudden stoppage of the clock. I believe the explanation to be as follows: As customary noises especially are unheard, I did not hear the pendulum of the clock. But its sudden stopping disturbed the balance of sound which had been dominating the room. This called attention to the cause of the disturbance, i. e., the ticking which had ceased, and hence perception was intensified backwards and I heard the last ticks, which I had not perceived before, one after another. The latent stimulus caused by the ticking worked backward. My attention was naturally awakened only after the last tick, but my perception was consecutive.

I soon heard of another case, this time, in court. There was a shooting in some house and an old peasant woman, who was busy sewing in the room, asserted that she had just before the shooting heard a few steps in the direction from which the shot must have come. Nobody would agree that there was any reason for supposing that the person in question should have made his final steps more noisily than his preceding ones. But I am convinced that the witness told the truth. The steps of the new arrival were perceived subconsciously; the further disturbance of the perception hindered

her occupation and finally, when she was frightened by the shot, the upper levels of consciousness were illuminated and the noises which had already reached the subconsciousness passed over the threshold and were consciously perceived.

I learned from an especially significant case, how the same thing could happen with regard to vision. A child was run over and killed by a careless coachman. A pensioned officer saw this through the window. His description was quite characteristic. It was the anniversary of a certain battle. The old gentleman, who stood by the window thinking about it and about his long dead comrades, was looking blankly out into the street. The horrible cry of the unhappy child woke him up and he really began to see. Then he observed that he had in truth seen everything that had happened before the child was knocked over—i. e., for some reason the coachman had turned around, turning the horses in such a way at the same time that the latter jumped sidewise upon the frightened child, and hence the accident. The general expressed himself correctly in this fashion: "I saw it all, but I did not perceive and know that I saw it until after the scream of the child." He offered also in proof of the correctness of his testimony, that he, an old cavalry officer, would have had to see the approaching misfortune if he had consciously seen the moving of the coachman, and then he would have had to be frightened. But he knew definitely that he was frightened only when the child cried out—he could not, therefore, have consciously perceived the preceding event. His story was confirmed by other witnesses.

This psychological process is of significance in criminal trials, inasmuch as many actionable cases depend upon sudden and unexpected events, where retrospective illumination may frequently come in. In such cases it is most important to determine what actually has been perceived, and it is never indifferent whether we take the testimony in question as true or not.

With regard to the senses of criminals, Lombroso and Ottolenghi have asserted that they are duller than those of ordinary people. The assertion is based on a collection made by Lombroso of instances of the great indifference of criminals to pain. But he has overlooked the fact that the reason is quite another thing. Barbarous living and barbarous morals are especially dulling, so that indifference to pain is a characteristic of all barbarous nations and characters. Inasmuch as there are many criminals among barbarous people, barbarity, criminality and indifference to pain come together in a

large number of cases. But there is nothing remarkable in this, and a direct relation between crime and dullness of the senses can not be demonstrated.