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.
[[ id="n36.1"]]
For a general consideration of perception see James, Principles of
Psychology.
Angell, Psychology.
[[ id="n36.2"]]
Meinong: Über die Bedeutung der Weberschen Gesetzes. Hamburg and
Leipzig, 1896.
[[ id="n36.3"]]
T. Pesch Das Weltphänomen
[[ id="n36.4"]]
H. Helmholtz: Die Tatsachen der Wahrnehmung. Braunschweig 1878.
[[ id="n36.5"]]
E. L. Fischer: Theorie der Gesichtswahrnehmung. Mainz 1891.
[[ id="n36.6"]]
Cf. Archiv, XVI, 371.