The criminalist studies the physiological psychology[172] 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.[173]
“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.”[174] In this direction Helmholtz[175] 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[176] 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 is 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
perceive 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.[177]
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.
(b) The Sense of Sight.