PERCEPTION.
=Perception and Sensation compared.=--A pure sensation we saw above, p.
12, to be an abstraction never realized in adult life. Anything which
affects our sense-organs does also more than that: it arouses processes
in the hemispheres which are partly due to the organization of that
organ by past experiences, and the results of which in consciousness are
described as ideas which the sensation suggests. The first of these
ideas is that of the _thing_ to which the sensible quality belongs. _The
consciousness of particular material things present to sense_ is
nowadays called _perception_. The consciousness of such things may be
more or less complete; it may be of the mere name of the thing and its
other essential attributes, or it may be of the thing's various remoter
relations. It is impossible to draw any sharp line of distinction
between the barer and the richer consciousness, because the moment we
get beyond the first crude sensation all our consciousness is of what is
_suggested_, and the various suggestions shade gradually into each
other, being one and all products of the same psychological machinery of
association. In the directer consciousness fewer, in the remoter more,
associative processes are brought into play.
_Sensational and reproductive brain-processes combined, then, are what
give us the content of our perceptions._ Every concrete particular
material thing is a conflux of sensible qualities, with which we have
become acquainted at various times. Some of these qualities, since they
are more constant, interesting, or practically important, we regard as
essential constituents of the thing. In a general way, such are the
tangible shape, size, mass, etc. Other properties, being more
fluctuating, we regard as more or less accidental or inessential. We
call the former qualities the reality, the latter its appearances. Thus,
I hear a sound, and say 'a horse-car'; but the sound is not the
horse-car, it is one of the horse-car's least important manifestations.
The real horse-car is a feelable, or at most a feelable and visible,
thing which in my imagination the sound calls up. So when I get, as now,
a brown eye-picture with lines not parallel, and with angles unlike, and
call it my big solid rectangular walnut library-table, that picture is
not the table. It is not even like the table as the table is for vision,
when rightly seen. It is a distorted perspective view of three of the
sides of what I mentally _perceive_ (more or less) in its totality and
undistorted shape. The back of the table, its square corners, its size,
its heaviness, are features of which I am conscious when I look, almost
as I am conscious of its name. The suggestion of the name is of course
due to mere custom. But no less is that of the back, the size, weight,
squareness, etc.
Nature, as Reid says, is frugal in her operations, and will not be at
the expense of a particular instinct to give us that knowledge which
experience and habit will soon produce. Reproduced attributes tied
together with presently felt attributes in the unity of a _thing_ with a
name, these are the materials out of which my actually perceived table
is made. Infants must go through a long education of the eye and ear
before they can perceive the realities which adults perceive. _Every
perception is an acquired perception._
=The Perceptive State of Mind is not a Compound.=--There is no reason,
however, for supposing that this involves a 'fusion' of separate
sensations and ideas. The thing perceived is the object of a unique
state of thought; due no doubt in part to sensational, and in part to
ideational currents, but in no wise 'containing' psychically the
identical 'sensations' and images which these currents would severally
have aroused if the others were not simultaneously there. We can often
directly notice a sensible difference in the consciousness, between the
latter case and the former. The sensible quality changes under our very
eye. Take the already-quoted catch, _Pas de lieu Rhône que nous_: one
may read this over and over again without recognizing the sounds to be
identical with those of the words _paddle your own canoe_. As the
English associations arise, the sound itself appears to change. Verbal
sounds are usually perceived with their meaning at the moment of being
heard. Sometimes, however, the associative irradiations are inhibited
for a few moments (the mind being preoccupied with other thoughts),
whilst the words linger on the ear as mere echoes of acoustic sensation.
Then, usually, their interpretation suddenly occurs. But at that moment
one may often surprise a change in the very _feel_ of the word. Our own
language would sound very different to us if we heard it without
understanding, as we hear a foreign tongue. Rises and falls of voice,
odd sibilants and other consonants, would fall on our ear in a way of
which we can now form no notion. Frenchmen say that English sounds to
them like the _gazouillement des oiseaux_--an impression which it
certainly makes on no native ear. Many of us English would describe the
sound of Russian in similar terms. All of us are conscious of the strong
inflections of voice and explosives and gutturals of German speech in a
way in which no German can be conscious of them.
This is probably the reason why, if we look at an isolated printed word
and repeat it long enough, it ends by assuming an entirely unnatural
aspect. Let the reader try this with any word on this page. He will soon
begin to wonder if it can possibly be the word he has been using all his
life with that meaning. It stares at him from the paper like a glass
eye, with no speculation in it. Its body is indeed there, but its soul
is fled. It is reduced, by this new way of attending to it, to its
sensational nudity. We never before attended to it in this way, but
habitually got it clad with its meaning the moment we caught sight of
it, and rapidly passed from it to the other words of the phrase. We
apprehended it, in short, with a cloud of associates, and thus
perceiving it, we felt it quite otherwise than as we feel it now
divested and alone.
Another well-known change is when we look at a landscape with our head
upside-down. Perception is to a certain extent baffled by this
manœuvre; gradations of distance and other space-determinations are
made uncertain; the reproductive or associative processes, in short,
decline; and, simultaneously with their diminution, the colors grow
richer and more varied, and the contrasts of light and shade more
marked. The same thing occurs when we turn a painting bottom-upward. We
lose much of its meaning, but, to compensate for the loss, we feel more
freshly the value of the mere tints and shadings, and become aware of
any lack of purely sensible harmony or balance which they may show. Just
so, if we lie on the floor and look up at the mouth of a person talking
behind us. His lower lip here takes the habitual place of the upper one
upon our retina, and seems animated by the most extraordinary and
unnatural mobility, a mobility which now strikes us because (the
associative processes being disturbed by the unaccustomed point of view)
we get it as a naked sensation and not as part of a familiar object
perceived.
Once more, then, we find ourselves driven to admit that when qualities
of an object impress our sense and we thereupon perceive the object, the
pure sensation as such of those qualities does not still exist inside of
the perception and form a constituent thereof. The pure sensation is one
thing and the perception another, and neither can take place at the same
time with the other, because their cerebral conditions are not the same.
They may _resemble_ each other, but in no respect are they identical
states of mind.
=Perception is of Definite and Probable Things.=--The chief cerebral
conditions of perception are old paths of association radiating from the
sense-impression. If a certain impression be strongly associated with
the attributes of a certain thing, that thing is almost sure to be
perceived when we get the impression. Examples of such things would be
familiar people, places, etc., which we recognize and name at a glance.
But _where the impression is associated with more than one reality_, so
that either of two discrepant sets of residual properties may arise, the
perception is doubtful and vacillating, and _the most that can then be
said of it is that it will be of a_ PROBABLE _thing_, of the thing which
would most usually have given us that sensation.
In these ambiguous cases it is interesting to note that perception is
rarely abortive; _some_ perception takes place. The two discrepant sets
of associates do not neutralize each other or mix and make a blur. What
we more commonly get is first one object in its completeness, and then
the other in its completeness. In other words, _all brain-processes are
such as give rise to what we may call_ FIGURED _consciousness_. If paths
are shot-through at all, they are shot-through in consistent systems,
and occasion thoughts of definite objects, not mere hodge-podges of
elements. Even where the brain's functions are half thrown out of gear,
as in aphasia or dropping asleep, this law of figured consciousness
holds good. A person who suddenly gets sleepy whilst reading aloud will
read wrong; but instead of emitting a mere broth of syllables, he will
make such mistakes as to read 'supper-time' instead of 'sovereign,'
'overthrow' instead of 'opposite,' or indeed utter entirely imaginary
phrases, composed of several definite words, instead of phrases of the
book. So in aphasia: where the disease is mild the patient's mistakes
consist in using entire wrong words instead of right ones. It is only in
grave lesions that he becomes quite inarticulate. These facts show how
subtle is the associative link; how delicate yet how strong that
connection among brain-paths which makes any number of them, once
excited together, thereafter tend to vibrate as a systematic whole. A
small group of elements, '_this_,' common to two systems, _A_ and _B_,
may touch off _A_ or _B_ according as accident decides the next step
(see Fig. 63). If it happen that a single point leading from '_this_' to
_B_ is momentarily a little more pervious than any leading from '_this_'
to _A_, then that little advantage will upset the equilibrium in favor
of the entire system _B_. The currents will sweep first through that
point and thence into all the paths of _B_, each increment of advance
making _A_ more and more impossible. The thoughts correlated with _A_
and _B_, in such a case, will have objects different, though similar.
The similarity will, however, consist in some very limited feature if
the 'this' be small. _Thus the faintest sensations will give rise to the
perception of definite things if only they resemble those which the
things are wont to arouse._
[Illustration: FIG. 63.]
=Illusions.=--Let us now, for brevity's sake, treat _A_ and _B_ in Fig. 63
as if they stood for objects instead of brain-processes. And let us
furthermore suppose that _A_ and _B_ are, both of them, objects which
might probably excite the sensation which I have called '_this_,' but
that on the present occasion _A_ and not _B_ is the one which actually
does so. If, then, on this occasion '_this_' suggests _A_ and not _B_,
the result is a _correct perception_. But if, on the contrary, 'this'
suggests _B_ and not _A_, the result is a _false perception_, or, as it
is technically called, an _illusion_. But the _process_ is the same,
whether the perception be true or false.
Note that in every illusion what is false is what is inferred, not what
is immediately given. The 'this,' if it were felt by itself alone, would
be all right; it only becomes misleading by what it suggests. If it is a
sensation of sight, it may suggest a tactile object, for example, which
later tactile experiences prove to be not there. _The so-called 'fallacy
of the senses,' of which the ancient sceptics made so much account, is
not fallacy of the senses proper, but rather of the intellect, which
interprets wrongly what the senses give._[39]
So much premised, let us look a little closer at these illusions. They
are due to two main causes. _The wrong object is perceived either
because_
1) _Although not on this occasion the real cause, it is yet the
habitual, inveterate, or most probable cause of 'this,'_; or because
2) _The mind is temporarily full of the thought of that object, and
therefore 'this' is peculiarly prone to suggest it at this moment._
I will give briefly a number of examples under each head. The first head
is the more important, because it includes a number of constant
illusions to which all men are subject, and which can only be dispelled
by much experience.
[Illustration: FIG. 64.]
=Illusions of the First Type.=--One of the oldest instances dates from
Aristotle. Cross two fingers and roll a pea, penholder, or other small
object between them. It will seem double. Professor Croom Robertson has
given the clearest analysis of this illusion. He observes that if the
object be brought into contact first with the forefinger and next with
the second finger, the two contacts seem to come in at different points
of space. The forefinger-touch seems higher, though the finger is really
lower; the second-finger-touch seems lower, though the finger is really
higher. "We perceive the contacts as double because we refer them to two
distinct parts of space." The touched sides of the two fingers are
normally not together in space, and customarily never do touch one
thing; the one thing which now touches them, therefore, seems in two
places, i.e. seems two things.
There is a whole batch of illusions which come from optical sensations
interpreted by us in accordance with our usual rule, although they are
now produced by an unusual object. The _stereoscope_ is an example. The
eyes see a picture apiece, and the two pictures are a little disparate,
the one seen by the right eye being a view of the object taken from a
point slightly to the right of that from which the left eye's picture is
taken. Pictures thrown on the two eyes by solid objects present this
sort of disparity, so that we react on the sensation in our usual way,
and perceive a solid. If the pictures be exchanged we perceive a hollow
mould of the object, for a hollow mould would cast just such disparate
pictures as these. Wheatstone's instrument, the _pseudoscope_, allows us
to look at solid objects and see with each eye the other eye's picture.
We then perceive the solid object hollow, _if it be an object which
might probably be hollow_, but not otherwise. Thus the perceptive
process is true to its law, which is _always to react on the sensation
in a determinate and figured fashion if possible, and in as probable a
fashion as the case admits_. A human face, e.g., never appears hollow to
the pseudoscope, for to couple faces and hollowness violates all our
habits. For the same reason it is very easy to make an intaglio cast of
a face, or the painted inside of a pasteboard mask, look convex, instead
of concave as they are.
=Curious illusions of movement= in objects occur whenever the eyeballs
move without our intending it. We have learned in an earlier chapter
(p. 72) that the original visual feeling of movement is produced by any
image passing over the retina. Originally, however, this sensation is
definitely referred neither to the object nor to the eyes. Such definite
reference grows up later, and obeys certain simple laws. For one thing,
we believe _objects_ to move whenever we get the retinal
movement-feeling, but think our _eyes_ are still. This gives rise to an
illusion when, after whirling on our heel, we stand still; for then
objects appear to continue whirling in the same direction in which, a
moment previous, our body actually whirled. The reason is that our
_eyes_ are animated, under these conditions, by an involuntary
_nystagmus_ or oscillation in their orbits, which may easily be observed
in anyone with vertigo after whirling. As these movements are
unconscious, the retinal movement-feelings which they occasion are
naturally referred to the objects seen. The whole phenomenon fades out
after a few seconds. And it ceases if we voluntarily fix our eyes upon a
given point.
There is an illusion of movement of the opposite sort, with which every
one is familiar at _railway stations_. Habitually, when we ourselves
move forward, our entire field of view glides backward over our retina.
When our movement is due to that of the windowed carriage, car, or boat
in which we sit, all stationary objects visible through the window give
us a sensation of gliding in the opposite direction. Hence, whenever we
get this sensation, of a window with _all_ objects visible through it
moving in one direction, we react upon it in our customary way, and
perceive a stationary field of view, over which the window, and we
ourselves inside of it, are passing by a motion of our own. Consequently
when another train comes alongside of ours in a station, and fills the
entire window, and, after standing still awhile, begins to glide away,
we judge that it is _our_ train which is moving, and that the other
train is still. If, however, we catch a glimpse of any part of the
station through the windows, or between the cars, of the other train,
the illusion of our own movement instantly disappears, and we perceive
the other train to be the one in motion. This, again, is but making the
usual and probable inference from our sensation.
_Another illusion due to movement_ is explained by Helmholtz. Most
wayside objects, houses, trees, etc., look small when seen from the
windows of a swift train. This is because we perceive them in the first
instance unduly near. And we perceive them unduly near because of their
extraordinarily rapid parallactic flight backwards. When we ourselves
move forward all objects glide backwards, as aforesaid; but the nearer
they are, the more rapid is this apparent translocation. Relative
rapidity of passage backwards is thus so familiarly associated with
nearness that when we feel it we perceive nearness. But with a given
size of retinal image the nearer an object is, the smaller do we judge
its actual size to be. Hence in the train, the faster we go, the nearer
do the trees and houses seem; and the nearer they seem, the smaller
(with that size of retinal image) must they look.
The feelings of our eyes' convergence, of their accommodation, the size
of the retinal image, etc., may give rise to illusions about the size
and distance of objects, which also belong to this first type.
=Illusions of the Second Type.=--In this type we perceive a wrong object
because our mind is full of the thought of it at the time, and any
sensation which is in the least degree connected with it touches off, as
it were, a train already laid, and gives us a sense that the object is
really before us. Here is a familiar example:
"If a sportsman, while shooting woodcock in cover, sees a bird about the
size and color of a woodcock get up and fly through the foliage, not
having time to see more than that it is a bird of such a size and color,
he immediately supplies by inference the other qualities of a woodcock,
and is afterwards disgusted to find that he has shot a thrush. I have
done so myself, and could hardly believe that the thrush was the bird I
fired at, so complete was my mental supplement to my visual
perception."[40]
As with game, so with enemies, ghosts, and the like. Anyone waiting in a
dark place and expecting or fearing strongly a certain object will
interpret any abrupt sensation to mean that object's presence. The boy
playing 'I spy,' the criminal skulking from his pursuers, the
superstitious person hurrying through the woods or past the churchyard
at midnight, the man lost in the woods, the girl who tremulously has
made an evening appointment with her swain, all are subject to illusions
of sight and sound which make their hearts beat till they are dispelled.
Twenty times a day the lover, perambulating the streets with his
preoccupied fancy, will think he perceives his idol's bonnet before him.
_The Proof-reader's Illusion._--I remember one night in Boston, whilst
waiting for a 'Mount Auburn' car to bring me to Cambridge, reading most
distinctly that name upon the signboard of a car on which (as I
afterwards learned) 'North Avenue' was painted. The illusion was so
vivid that I could hardly believe my eyes had deceived me. All reading
is more or less performed in this way.
"Practised novel-or newspaper-readers could not possibly get on so fast
if they had to see accurately every single letter of every word in order
to perceive the words. More than half of the words come out of their
mind, and hardly half from the printed page. Were this not so, did we
perceive each letter by itself, typographic errors in well-known words
would never be overlooked. Children, whose ideas are not yet ready
enough to perceive words at a glance, read them wrong if they are
printed wrong, that is, right according to the way of printing. In a
foreign language, although it may be printed with the same letters, we
read by so much the more slowly as we do not understand, or are unable
promptly to perceive, the words. But we notice misprints all the more
readily. For this reason Latin and Greek, and still better Hebrew, works
are more correctly printed, because the proofs are better corrected,
than in German works. Of two friends of mine, one knew much Hebrew, the
other little; the latter, however, gave instruction in Hebrew in a
gymnasium; and when he called the other to help correct his pupils'
exercises, it turned out that he could find out all sorts of little
errors better than his friend, because the latter's perception of the
words as totals was too swift."[41]
_Testimony to personal identity is proverbially fallacious_ for similar
reasons. A man has witnessed a rapid crime or accident, and carries away
his mental image. Later he is confronted by a prisoner whom he forthwith
perceives in the light of that image, and recognizes or 'identifies' as
the criminal, although he may never have been near the spot. Similarly
at the so-called 'materializing séances' which fraudulent mediums give:
in a dark room a man sees a gauze-robed figure who in a whisper tells
him she is the spirit of his sister, mother, wife, or child, and falls
upon his neck. The darkness, the previous forms, and the expectancy have
so filled his mind with premonitory images that it is no wonder he
perceives what is suggested. These fraudulent 'séances' would furnish
most precious documents to the psychology of perception, if they could
only be satisfactorily inquired into. In the hypnotic trance any
suggested object is sensibly perceived. In certain subjects this happens
more or less completely after waking from the trance. It would seem that
under favorable conditions a somewhat similar susceptibility to
suggestion may exist in certain persons who are not otherwise entranced
at all.
This suggestibility obtains in all the senses, although high authorities
have doubted this power of imagination to falsify present impressions of
sense. Everyone must be able to give instances from the smell-sense.
When we have paid the faithless plumber for pretending to mend our
drains, the intellect inhibits the nose from perceiving the same
unaltered odor, until perhaps several days go by. As regards the
ventilation or heating of rooms, we are apt to feel for some time as we
think we ought to feel. If we believe the ventilator is shut, we feel
the room close. On discovering it open, the oppression disappears.
It is the same with touch. Everyone must have felt the sensible quality
change under his hand, as sudden contact with something moist or hairy,
in the dark, awoke a shock of disgust or fear which faded into calm
recognition of some familiar object. Even so small a thing as a crumb of
potato on the table-cloth, which we pick up, thinking it a crumb of
bread, feels horrible for a few moments to our fancy, and different from
what it is.
In the sense of hearing, similar mistakes abound. Everyone must recall
some experience in which sounds have altered their character as soon as
the intellect referred them to a different source. The other day a
friend was sitting in my room, when the clock, which has a rich low
chime, began to strike. "Hollo!" said he, "hear that hand-organ in the
garden," and was surprised at finding the real source of the sound. I
have had myself a striking illusion of the sort. Sitting reading, late
one night, I suddenly heard a most formidable noise proceeding from the
upper part of the house, which it seemed to fill. It ceased, and in a
moment renewed itself. I went into the hall to listen, but it came no
more. Resuming my seat in the room, however, there it was again, low,
mighty, alarming, like a rising flood or the _avant-courier_ of an awful
gale. It came from all space. Quite startled, I again went into the
hall, but it had already ceased once more. On returning a second time to
the room, I discovered that it was nothing but the breathing of a little
Scotch terrier which lay asleep on the floor. The noteworthy thing is
that as soon as I recognized what it was, I was compelled to think it a
different sound, and could not then hear it as I had heard it a moment
before.
The sense of sight is pregnant with illusions of both the types
considered. No sense gives such fluctuating impressions of the same
object as sight does. With no sense are we so apt to treat the
sensations immediately given as mere signs; with none is the invocation
from memory of a _thing_, and the consequent perception of the latter,
so immediate. The 'thing' which we perceive always resembles, as we
shall hereafter see, the object of some absent sensation, usually
another optical figure which in our mind has come to be a standard bit
of reality; and it is this incessant reduction of our immediately given
optical objects to more standard and 'real' forms which has led some
authors into the mistake of thinking that our optical sensations are
originally and natively of no particular form at all.
Of accidental and occasional illusions of sight many amusing examples
might be given. Two will suffice. One is a reminiscence of my own. I was
lying in my berth in a steamer listening to the sailors 'at their
devotions with the holystones' outside; when, on turning my eyes to the
window, I perceived with perfect distinctness that the chief-engineer of
the vessel had entered my state-room, and was standing looking through
the window at the men at work upon the guards. Surprised at his
intrusion, and also at his intentness and immobility, I remained
watching him and wondering how long he would stand thus. At last I
spoke; but getting no reply, sat up in my berth, and then saw that what
I had taken for the engineer was my own cap and coat hanging on a peg
beside the window. The illusion was complete; the engineer was a
peculiar-looking man; and I saw him unmistakably; but after the
illusion had vanished I found it hard voluntarily to make the cap and
coat look like him at all.
'=Apperception.='--In Germany since Herbart's time psychology has always
had a great deal to say about a process called _Apperception_. The
incoming ideas or sensations are said to be 'apperceived' by 'masses' of
ideas already in the mind. It is plain that the process we have been
describing as perception is, at this rate, an apperceptive process. So
are all recognition, classing, and naming; and passing beyond these
simplest suggestions, all farther thoughts about our percepts are
apperceptive processes as well. I have myself not used the word
apperception, because it has carried very different meanings in the
history of philosophy, and 'psychic reaction,' 'interpretation,'
'conception,' 'assimilation,' 'elaboration,' or simply 'thought,' are
perfect synonyms for its Herbartian meaning, widely taken. It is,
moreover, hardly worth while to pretend to analyze the so-called
apperceptive performances beyond the first or perceptive stage, because
their variations and degrees are literally innumerable. 'Apperception'
is a name for the sum total of the effects of what we have studied as
association; and it is obvious that the things which a given experience
will suggest to a man depend on what Mr. Lewes calls his entire
psychostatical conditions, his nature and stock of ideas, or, in other
words, his character, habits, memory, education, previous experience,
and momentary mood. We gain no insight into what really occurs either in
the mind or in the brain by calling all these things the 'apperceiving
mass,' though of course this may upon occasion be convenient. On the
whole I am inclined to think Mr. Lewes's term of 'assimilation' the most
fruitful one yet used.
The 'apperceiving mass' is treated by the Germans as the active factor,
the apperceived sensation as the passive one; the sensation being
usually modified by the ideas in the mind. Out of the interaction of the
two, cognition is produced. But as Steinthal remarks, the apperceiving
mass is itself often modified by the sensation. To quote him: "Although
the _a priori_ moment commonly shows itself to be the more powerful,
apperception-processes can perfectly well occur in which the new
observation transforms or enriches the apperceiving group of ideas. A
child who hitherto has seen none but four-cornered tables apperceives a
round one as a table; but by this the apperceiving mass ('table') is
enriched. To his previous knowledge of tables comes this new feature
that they need not be four-cornered, but may be round. In the history of
science it has happened often enough that some discovery, at the same
time that it was apperceived, i.e. brought into connection with the
system of our knowledge, transformed the whole system. In principle,
however, we must maintain that, although either factor is both active
and passive, the _a priori_ factor is almost always the more active of
the two."[42]
=Genius and Old-fogyism.=--This account of Steinthal's brings out very
clearly the _difference between our psychological conceptions and what
are called concepts in logic_. In logic a concept is unalterable; but
what are popularly called our 'conceptions of things' alter by being
used. The aim of 'Science' is to attain conceptions so adequate and
exact that we shall never need to change them. There is an everlasting
struggle in every mind between the tendency to keep unchanged, and the
tendency to renovate, its ideas. Our education is a ceaseless compromise
between the conservative and the progressive factors. Every new
experience must be disposed of under _some_ old head. The great point is
to find the head which has to be least altered to take it in. Certain
Polynesian natives, seeing horses for the first time, called them pigs,
that being the nearest head. My child of two played for a week with the
first orange that was given him, calling it a 'ball.' He called the
first whole eggs he saw 'potatoes,' having been accustomed to see his
'eggs' broken into a glass, and his potatoes without the skin. A folding
pocket-corkscrew he unhesitatingly called 'bad-scissors.' Hardly any one
of us can make new heads easily when fresh experiences come. Most of us
grow more and more enslaved to the stock conceptions with which we have
once become familiar, and less and less capable of assimilating
impressions in any but the old ways. Old-fogyism, in short, is the
inevitable terminus to which life sweeps us on. Objects which violate
our established habits of 'apperception' are simply not taken account of
at all; or, if on some occasion we are forced by dint of argument to
admit their existence, twenty-four hours later the admission is as if it
were not, and every trace of the unassimilable truth has vanished from
our thought. Genius, in truth, means little more than the faculty of
perceiving in an unhabitual way.
On the other hand, nothing is more congenial, from babyhood to the end
of life, than to be able to assimilate the new to the old, to meet each
threatening violator or burster of our well-known series of concepts, as
it comes in, see through its unwontedness, and ticket it off as an old
friend in disguise. This victorious assimilation of the new is in fact
the type of all intellectual pleasure. The lust for it is scientific
curiosity. The relation of the new to the old, before the assimilation
is performed, is wonder. We feel neither curiosity nor wonder concerning
things so far beyond us that we have no concepts to refer them to or
standards by which to measure them.[43] The Fuegians, in Darwin's
voyage, wondered at the small boats, but took the big ship as a 'matter
of course.' Only what we partly know already inspires us with a desire
to know more. The more elaborate textile fabrics, the vaster works in
metal, to most of us are like the air, the water, and the ground,
absolute existences which awaken no ideas. It is a matter of course that
an engraving or a copper-plate inscription should possess that degree of
beauty. But if we are shown a _pen_-drawing of equal perfection, our
personal sympathy with the difficulty of the task makes us immediately
wonder at the skill. The old lady admiring the Academician's picture
says to him: "And is it really all done _by hand_?"
=The Physiological Process in Perception.=--Enough has now been said to
prove the general law of perception, which is this: that _whilst part of
what we perceive comes through our senses from the object before us,
another part_ (and it may be the larger part) _always comes out of our
own mind_.
At bottom this is but a case of the general fact that our nerve-centres
are organs for reacting on sense-impressions, and that our hemispheres,
in particular, are given us that records of our past private experience
may coöperate in the reaction. Of course such a general statement is
vague. If we try to put an exact meaning into it, what we find most
natural to believe is that the _brain reacts_ by paths which the
previous experiences have worn, _and which make us perceive the probable
thing_, i.e., the thing by which on the previous occasions the reaction
was most frequently aroused. The reaction of the hemispheres consists in
the lighting up of a certain system of paths by the current entering
from the outer world. What corresponds to this mentally is a certain
special pulse of thought, the thought, namely, of that most probable
object. Farther than this in the analysis we can hardly go.
=Hallucinations.=--Between normal perception and illusion we have seen
that there is no break, the _process_ being identically the same in
both. The last illusions we considered might fairly be called
hallucinations. We must now consider the false perceptions more commonly
called by that name. In ordinary parlance hallucination is held to
differ from illusion in that, whilst there is an object really there in
illusion, _in hallucination there is no objective stimulus at all_. We
shall presently see that this supposed absence of objective stimulus in
hallucination is a mistake, and that hallucinations are often only
_extremes_ of the perceptive process, in which the secondary cerebral
reaction is out of all normal proportion to the peripheral stimulus
which occasions the activity. Hallucinations usually appear abruptly and
have the character of being forced upon the subject. But they possess
various degrees of apparent _objectivity_. One mistake _in limine_ must
be guarded against. They are often talked of as _images_ projected
outwards by mistake. But where an hallucination is complete, it is much
more than a mental image. _An hallucination, subjectively considered, is
a sensation, as good and true a sensation as if there were a real object
there._ The object happens not to be there, that is all.
The milder degrees of hallucination have been designated as
_pseudo-hallucinations_. Pseudo-hallucinations and hallucinations have
been sharply distinguished from each other only within a few years. From
ordinary images of memory and fancy, pseudo-hallucinations differ in
being much more vivid, minute, detailed, steady, abrupt, and
spontaneous, in the sense that all feeling of our own activity in
producing them is lacking. Dr. Kandinsky had a patient who, after taking
opium or haschisch, had abundant pseudo-hallucinations and
hallucinations. As he also had strong visualizing power and was an
educated physician, the three sorts of phenomena could be easily
compared. Although projected outwards (usually not farther than the
limit of distinctest vision, a foot or so), the pseudo-hallucinations
_lacked the character of objective reality_ which the hallucinations
possessed, but, unlike the pictures of imagination, it was almost
impossible to produce them at will. Most of the 'voices' which
people hear (whether they give rise to delusions or not) are
pseudo-hallucinations. They are described as '_inner_' voices, although
their character is entirely unlike the inner speech of the subject with
himself. I know several persons who hear such inner voices making
unforeseen remarks whenever they grow quiet and listen for them. They
are a very common incident of delusional insanity, and may at last grow
into vivid or completely exteriorized hallucinations. The latter are
comparatively frequent occurrences in sporadic form; and certain
individuals are liable to have them often. From the results of the
'Census of Hallucinations,' which was begun by Edmund Gurney, it would
appear that, roughly speaking, one person at least in every ten is
likely to have had a vivid hallucination at some time in his life. The
following case from a healthy person will give an idea of what these
hallucinations are:
"When a girl of eighteen, I was one evening engaged in a very painful
discussion with an elderly person. My distress was so great that I took
up a thick ivory knitting-needle that was lying on the mantelpiece of
the parlor and broke it into small pieces as I talked. In the midst of
the discussion I was very wishful to know the opinion of a brother with
whom I had an unusually close relationship. I turned round and saw him
sitting at the farther side of a centre-table, with his arms folded (an
unusual position with him), but, to my dismay, I perceived from the
sarcastic expression of his mouth that he was not in sympathy with me,
was not 'taking my side,' as I should then have expressed it. The
surprise cooled me, and the discussion was dropped.
"Some minutes after, having occasion to speak to my brother, I turned
towards him, but he was gone. I inquired when he left the room, and was
told that he had not been in it, which I did not believe, thinking that
he had come in for a minute and had gone out without being noticed.
About an hour and a half afterwards he appeared, and convinced me, with
some trouble, that he had never been near the house that evening. He is
still alive and well."
The hallucinations of fever-delirium are a mixture of
pseudo-hallucination, true hallucination, and illusion. Those of opium,
haschish, and belladonna resemble them in this respect. The commonest
hallucination of all is that of hearing one's own name called aloud.
Nearly one half of the sporadic cases which I have collected are of this
sort.
=Hallucination and Illusion.=--Hallucinations are easily produced by
verbal suggestion in hypnotic subjects. Thus, point to a dot on a sheet
of paper, and call it 'General Grant's photograph,' and your subject
will see a photograph of the General there instead of the dot. The dot
gives objectivity to the appearance, and the suggested notion of the
General gives it form. Then magnify the dot by a lens; double it by a
prism or by nudging the eyeball; reflect it in a mirror; turn it
upside-down; or wipe it out; and the subject will tell you that the
'photograph' has been enlarged, doubled, reflected, turned about, or
made to disappear. In M. Binet's language, the dot is the outward _point
de repère_ which is needed to give objectivity to your suggestion, and
without which the latter will only produce an inner image in the
subject's mind. M. Binet has shown that such a peripheral _point de
repère_ is used in an enormous number, not only of hypnotic
hallucinations, but of hallucinations of the insane. These latter are
often _unilateral_; that is, the patient hears the voices always on one
side of him, or sees the figure only when a certain one of his eyes is
open. In many of these cases it has been distinctly proved that a morbid
irritation in the internal ear, or an opacity in the humors of the eye,
was the starting point of the current which the patient's diseased
acoustic or optical centres clothed with their peculiar products in the
way of ideas. _Hallucinations produced in this way are 'illusions'; and
M. Binet's theory, that all hallucinations must start in the periphery,
may be called an attempt to reduce hallucination and illusion to one
physiological type_, the type, namely, to which normal perception
belongs. In every case, according to M. Binet, whether of perception, of
hallucination, or of illusion, we get the sensational vividness by means
of a current from the peripheral nerves. It may be a mere trace of a
current. But that trace is enough to kindle the maximal process of
disintegration in the cells (cf. p. 310), and to give to the object
perceived the character of _externality_. What the _nature_ of the
object shall be will depend wholly on the particular system of paths in
which the process is kindled. Part of the thing in all cases comes from
the sense-organ, the rest is furnished by the mind. But we cannot by
introspection distinguish between these parts; and our only formula for
the result is that the brain has _reacted on_ the impression in the
resulting way.
M. Binet's theory accounts indeed for a multitude of cases, but
certainly not for all. The prism does not always double the false
appearance, nor does the latter always disappear when the eyes are
closed. For Binet, an abnormally or exclusively active part of the
cortex gives the _nature_ of what shall appear, whilst a peripheral
sense-organ alone can give the _intensity_ sufficient to make it appear
projected into real space. But since this intensity is after all but a
matter of degree, one does not see why, under rare conditions, the
degree in question _might_ not be attained by inner causes exclusively.
In that case we should have certain hallucinations centrally initiated,
as well as the peripherally initiated hallucinations which are the only
sort that M. Binet's theory allows. _It seems probable on the whole,
therefore, that centrally initiated hallucinations can exist._ How often
they do exist is another question. The existence of hallucinations which
affect more than one sense is an argument for central initiation. For,
grant that the thing seen may have its starting point in the outer
world, the voice which it is heard to utter must be due to an influence
from the visual region, i.e. must be of central origin.
Sporadic cases of hallucination, visiting people only once in a lifetime
(which seem to be a quite frequent type), are on any theory hard to
understand in detail. They are often extraordinarily complete; and the
fact that many of them are reported as _veridical_, that is, as
coinciding with real events, such as accidents, deaths, etc., of the
persons seen, is an additional complication of the phenomenon. The first
really scientific study of hallucination in all its possible bearings,
on the basis of a large mass of empirical material, was begun by Mr.
Edmund Gurney and is continued by other members of the Society for
Psychical Research; and the 'Census' is now being applied to several
countries under the auspices of the International Congress of
Experimental Psychology. It is to be hoped that out of these combined
labors something solid will eventually grow. The facts shade off into
the phenomena of motor automatism, trance, etc.; and nothing but a wide
comparative study can give really instructive results.[44]