ILLUSIONS OF PERCEPTION--_continued_.
B. _Active Illusions._
When giving an account of the mechanism of perception, I spoke of an
independent action of the imagination which tends to anticipate the
process of suggestion from without. Thus, when expecting a particular
friend, I recognize his form much more readily than when my mind has not
been preoccupied with his image.
A little consideration will show that this process must be highly
favourable to illusion. To begin with, even if the preperception be
correct, that is to say, if it answer to the perception, the mere fact
of vivid expectation will affect the exact moment of the completed act
of perception. And recent experiment shows that in certain cases such a
previous activity of expectant attention may even lead to the illusory
belief that the perception takes place before it actually does.[47]
A more palpable source of error resides in the risk of the formation of
an inappropriate preperception. If a wrong mental image happens to have
been formed and vividly entertained, and if the actual impression fits
in to a certain extent with this independently formed preperception, we
may have a fusion of the two which exactly simulates the form of a
complete percept. Thus, for example, in the case just supposed, if
another person, bearing some resemblance to our expected friend, chances
to come into view, we may probably stumble into the error of taking one
person for another.
On the physical side, we may, agreeably to the hypothesis mentioned
above, express this result by saying that, owing to a partial identity
in the nervous processes involved in the anticipatory image and the
impression, the two tend to run one into the other, constituting one
continuous process.
There are different ways in which this independent activity of the
imagination may falsify our perceptions. Thus, we may voluntarily choose
to entertain a certain image for the moment, and to look at the
impression in a particular way, and within certain limits such
capricious selection of an interpretation is effectual in giving a
special significance to an impression. Or the process of independent
preperception may go on apart from our volitions, and perhaps in spite
of these, in which case the illusion has something of the irresistible
necessity of a passive illusion. Let us consider separately each mode
of production.
_Voluntary Selection of Interpretation._
The action of a capricious exercise of the imagination in relation to an
impression is illustrated in those cases where experience and suggestion
offer to the interpreting mind an uncertain sound, that is to say, where
the present sense-signs are ambiguous. Here we obviously have a choice
of interpretation. And it is found that, in these cases, what we see
depends very much on what we wish to see. The interpretation adopted is
still, in a sense, the result of suggestion, but of one particular
suggestion which the fancy of the moment determines. Or, to put it
another way, the caprice of the moment causes the attention to focus
itself in a particular manner, to direct itself specially to certain
aspects and relations of objects.
The eye's interpretation of movement, already referred to, obviously
offers a wide field for this play of selective imagination. When looking
out of the window of a railway carriage, I can at will picture to my
mind the trees and telegraph posts as moving objects. Sometimes the true
interpretation is so uncertain that the least inclination to view the
phenomenon in one way determines the result. This is illustrated in a
curious observation of Sinsteden. One evening, on approaching a windmill
obliquely from one side, which under these circumstances he saw only as
a dark silhouette against a bright sky, he noticed that the sails
appeared to go, now in one direction, now in another, according as he
imagined himself looking at the front or at the back of the
windmill.[48]
In the interpretation of geometrical drawings, as those of crystals,
there is, as I have observed, a general tendency to view the flat
delineation as answering to a raised object, or a body in relief,
according to the common run of our experience. Yet there are cases where
experience is less decided, and where, consequently, we may regard any
particular line as advancing or receding. And it is found that when we
vividly imagine that the drawing is that of a convex or concave surface,
we see it to be so, with all the force of a complete perception. The
least disposition to see it in the other way will suffice to reverse the
interpretation. Thus, in the following drawing, the reader can easily
see at will something answering to a truncated pyramid, or to the
interior of a cooking vessel.
[Illustration: FIG. 5.]
Similarly, in the accompanying figure of a transparent solid, I can at
will select either of the two surfaces which approximately face the eye
and regard it as the nearer, the other appearing as the hinder surface
looked at through the body.
[Illustration: FIG. 6.]
Again, in the next drawing, taken from Schroeder, one may, by an effort
of will, see the diagonal step-like pattern, either as the view from
above of the edge of an advancing piece of wall at _a_, or as the view
from below of the edge of an advancing (overhanging) piece of wall at
_b_.
[Illustration: FIG. 7.]
These last drawings are not in true perspective on either of the
suppositions adopted, wherefore the choice is easier. But even when an
outline form is in perspective, a strenuous effort of imagination may
suffice to bring about a conversion of the appearance. Thus, if the
reader will look at the drawing of the box-like solid (Fig. 3, p. 79),
he will find that, after a trial or two, he succeeds in seeing it as a
_concave_ figure representing the coyer and two sides of a box as looked
at from within.[49]
Many of my readers, probably, share in my power of variously
interpreting the relative position of bands or stripes on fabrics such
as wall-papers, according to wish. I find that it is possible to view
now this stripe or set of stripes as standing out in relief upon the
others as a ground, now these others as advancing out of the first as a
background. The difficulty of selecting either interpretation at will
becomes greater, of course, in those cases where there is a powerful
suggestion of some particular local arrangement, as, for example, the
case of patterns much brighter than the ground, and especially of such
as represent known objects, as flowers. Yet even here a strong effort of
imagination will often suffice to bring about a conversion of the first
appearance.
A somewhat similar choice of interpretation offers itself in looking at
elaborate decorative patterns. When we strongly imagine any number of
details to be elements of one figure, they seem to become so; and a
given detail positively appears to alter in character according as it is
viewed as an element of a more or less complex figure.
These examples show what force belongs to a vivid preconception, if this
happens to fit only very roughly the impression of the moment, that is
to say, if the interpretative image is one of the possible suggestions
of the impression. The play of imagination takes a wider range in those
cases where the impression is very indefinite in character, easily
allowing of a considerable variety of imaginative interpretation.
I referred at the beginning of this account of sense-illusions to the
readiness with which the mind deceives itself with respect to the nature
and causes of the vague sensations which usually form the dim background
of our mental life. A person of lively imagination, by trying to view
these in a particular way, and by selectively attending to those aspects
of the sensation which answer to the caprice of the moment, may give a
variety of interpretations to one and the same set of sensations. For
example, it is very easy to get confused with respect to those tactual
and motor feelings which inform us of the position of our bodily
members. And so, when lying in bed, and attending to the sensations
connected with the legs, we may easily delude ourselves into supposing
that these members are arranged in a most eccentric fashion. Similarly,
by giving special heed to the sensations arising in connection with the
condition of the skin at any part, we may amuse ourselves with the
strangest fancies as to what is going on in these regions.
Again, when any object of visual perception is indistinct or indefinite
in form, there is plainly an opening for this capricious play of fancy
in transforming the actual. This is illustrated in the well-known
pastime of discovering familiar forms, such as those of the human head
and animals, in distant rocks and clouds, and of seeing pictures in the
fire, and so on. The indistinct and indefinite shapes of the masses of
rock, cloud, or glowing coal, offer an excellent field for creative
fancy, and a person of lively imagination will discover endless forms in
what, to an unimaginative eye, is a formless waste. Johannes Müller
relates that, when a child, he used to spend hours in discovering the
outlines of forms in the partly blackened and cracked stucco of the
house that stood opposite to his own.[50] Here it is plain that, while
experience and association are not wholly absent, but place certain wide
limits on this process of castle-building, the spontaneous activity of
the percipient mind is the great determining force.
So much as to the influence of a perfectly unfettered voluntary
attention on the determination of the stage of preperception, and,
through this, of the resulting interpretation. Let us now pass to cases
in which this direction of preperception follows not the caprice of the
moment, but the leading of some fixed predisposition in the
interpreter's mind. In these cases attention is no longer free, but
fettered, only it is now fettered rather from within than from without;
that is to say, the dominating preperception is much more the result of
an independent bent of the imagination than of some suggestion forced on
the mind by the actual impression of the moment.
_Involuntary Mental Preadjustment._
If we glance back at the examples of capricious selection just noticed,
we shall see that they are really limited not only by the character of
the impression of the time, but also by the mental habits of the
spectator. That is to say, we find that his fancy runs in certain
definite directions, and takes certain habitual forms. It has already
been observed that the percipient mind has very different attitudes with
respect to various kinds of impression. Towards some it holds itself at
a distance, while towards others it at once bears itself familiarly; the
former are such as answer to its previous habit and bent of imagination,
the latter such as do not so answer.
This bent of the interpretative imagination assumes, as we have already
seen, two forms, that of a comparatively permanent disposition, and that
of a temporary state of expectation or mental preparedness. Illusion may
arise in connection with either of these forms. Let us illustrate both
varieties, beginning with those which are due to a lasting mental
disposition.
It is impossible here to specify all the causes of illusion residing in
organized tendencies of the mind. The whole past mental life, with its
particular shade of experience, its ruling emotions, and its habitual
direction of fancy, serves to give a particular colour to new
impressions, and so to favour illusion. There is a "personal equation"
in perception as in belief--an amount of erroneous deviation from the
common average view of external things, which is the outcome of
individual temperament and habits of mind. Thus, a naturally timid man
will be in general disposed to see ugly and fearful objects where a
perfectly unbiased mind perceives nothing of the kind; and the forms
which these objects of dread will assume are determined by the character
of his past experience, and by the customary direction of his
imagination.
In perfectly healthy states of mind this influence of temperament and
mental habit on the perception of external objects is, of course, very
limited; it shows itself more distinctly, as we shall see, in modifying
the estimate of things in relation to the æsthetic and other feelings.
This applies to the mythical poetical way of looking at nature--a part
of our subject to which we shall have to return later on.
Passing now from the effect of such permanent dispositions, let us look
at the more striking results of temporary expectancy of mind.
When touching on the influence of such a temporary mental attitude in
the process of correct perception, I remarked that this readiness of
mind might assume an indefinite or a definite form. We will examine the
effect of each kind in the production of illusion.
_Action of Sub-Expectation._
First of all, then, our minds may at the particular moment be disposed
to entertain any one of a vaguely circumscribed group of images. Thus,
to return to the example already referred to, when in Italy, we are in a
state of readiness to frame any of the images that we have learnt to
associate with this country. We may not be distinctly anticipating any
one kind of object, but are nevertheless in a condition of
_sub-expectation_ with reference to a large number of objects.
Accordingly, when an impression occurs which answers only very roughly
to one of the associated images, there is a tendency to superimpose the
image on the impression. In this way illusion arises. Thus, a man, when
strolling in a cathedral, will be apt to take any kind of faint hollow
sound for the soft tones of an organ.
The disposition to anticipate fact and reality in this way will be all
the stronger if, as usually happens, the mental images thus lying ready
for use have an emotional colouring. Emotion is the great disturber of
all intellectual operations. It effects marvellous things, as we shall
presently see, in the region of illusory belief, and its influence is
very marked in the seemingly cooler region of external perception. The
effect of any emotional excitement appears to be to give a preternatural
vividness and persistence to the ideas answering to it, that is to say,
the ideas which are its excitants, or which are otherwise associated
with it. Owing to this circumstance, when the mind is under the
temporary sway of any feeling, as, for example, fear, there will be a
special readiness to interpret objects by help of images congruent with
the emotion. Thus, a man under the control of fear will be ready to see
any kind of fear-inspiring object whenever there is any resemblance to
such in the things actually present to his vision. The state of awe
which the surrounding circumstances of a spiritualist _séance_ inspires
produces a general readiness of mind to perceive what is strange,
mysterious, and apparently miraculous.
It is worth noting, perhaps, that those delightful half-illusions which
imitative art seeks to produce are greatly favoured by such a temporary
attitude of the interpreting imagination. In the theatre, for example,
we are prepared for realizing the semblance of life that is to be
unfolded before us. We come knowing that what is to be performed aims at
representing a real action or actual series of events. We not improbably
work ourselves into a slightly excited state in anticipation of such a
representation. More than this, as the play progresses, the realization
of what has gone before produces a strong disposition to believe in the
reality of what is to follow. And this effect is proportionate to the
degree of coherence and continuity in the action. In this way, there is
a cumulative effect on the mind. If the action is good, the illusion, as
every play-goer knows, is most complete towards the end.
Were it not for all this mental preparation, the illusory character of
the performance would be too patent to view, and our enjoyment would
suffer. A man is often aware of this when coming into a theatre during
the progress of a piece before his mind accommodates itself to the
meaning of the play. And the same thing is recognizable in the fact that
the frequenter of the theatre has his susceptibility to histrionic
delusion increased by acquiring a habit of looking out for the meaning
of the performance. Persons who first see a play, unless they be of
exceptional imagination and have thought much about the theatre--as
Charlotte Brontë, for instance--hardly feel the illusion at all. At
least, this is true of the opera, where the departure from reality is
so striking that the impression can hardly fail to be a ludicrous one,
till the habit of taking the performance for what it is intended to be
is fully formed.[51]
A similar effect of intellectual preadjustment is observable in the
fainter degrees of illusion produced by pictorial art. Here the
undeceiving circumstances, the flat surface, the surroundings, and so
on, would sometimes be quite sufficient to prevent the least degree of
illusion, were it not that the spectator comes prepared to see a
representation of some real object. This is our state of mind when we
enter a picture gallery or approach what we recognize as a picture on
the wall of a room. A savage would not "realize" a slight sketch as soon
as one accustomed to pictorial representation, and ready to perform the
required interpretative act.[52]
So much as to the effect of an indefinite state of sub-expectation in
misleading our perceptions. Let us now glance at the results of definite
preimagination, including what are generally known as expectations.
_Effects of Vivid Expectation._
Such expectations may grow out of some present objective facts, which
serve as signs of the expected event; or they may arise by way of verbal
suggestion; or, finally, they may be due to internal spontaneous
imagination.
In the first place, then, the expectations may grow out of previous
perceptions, while, nevertheless, the direction of the expectation may
be a wrong one. Here the interpreting imagination is, in a large sense,
under the control of external suggestion, though, with respect to the
particular impression that is misconstrued, it may be regarded as acting
independently and spontaneously.
Illustrations of this effect in producing illusion will easily occur to
the reader. If I happen to have heard that a particular person has been
a soldier or clergyman, I tend to see the marks of the class in this
person, and sometimes find that this process of recognition is
altogether illusory. Again, let us suppose that a person is expecting a
friend by a particular train. A passenger steps out of the train bearing
a superficial resemblance to his friend; in consequence of which he
falls into the error of false identification.
The delusions of the conjuror depend on a similar principle. The
performer tells his audience that he is about to do a certain thing, for
example, take a number of animals out of a small box which is incapable
of holding them. The hearers, intent on what has been said, vividly
represent to themselves the action described. And in this way their
attention becomes bribed, so to speak, beforehand, and fails to notice
the inconspicuous movements which would at once clear up the mystery.
Similarly with respect to the illusions which overtake people at
spiritualist _séances_. The intensity of the expectation of a particular
kind of object excludes calm attention to what really happens, and the
slightest impressions which answer to signs of the object anticipated
are instantly seized by the mind and worked up into illusory
perceptions.
It is to be noted that even when the impression cannot be made to tally
exactly with the expectation, the force of the latter often effects a
grotesque confusion of the perception. If, for example, a man goes into
a familiar room in the dark in order to fetch something, and for a
moment forgets the particular door by which he has entered, his definite
expectation of finding things in a certain order may blend with the
order of impressions experienced, producing for the moment a most
comical illusion as to the actual state of things.
When the degree of expectation is unusually great, it may suffice to
produce something like the counterfeit of a real sensation. This happens
when the present circumstances are powerfully suggestive of an immediate
event. The effect is all the more powerful, moreover, in those cases
where the object or event expected is interesting or exciting, since
here the mental image gains in vividness through the emotional
excitement attending it. Thus, if I am watching a train off and know
from all the signs that it is just about to start, I easily delude
myself into the conviction that it has begun to start, when it is
really still.[53] An intense degree of expectation may, in such cases,
produce something indistinguishable from an actual sensation. This
effect is seen in such common experiences as that the sight of food
makes the mouth of a hungry man water; that the appearance of a surgical
instrument produces a nascent sensation of pain; and that a threatening
movement, giving a vivid anticipation of tickling, begets a feeling
which closely approximates to the result of actual tickling.
One or two very striking instances of such imagined sensations are given
by Dr. Carpenter.[54] Here is one. An officer who superintended the
exhuming of a coffin rendered necessary through a suspicion of crime,
declared that he already experienced the odour of decomposition, though
it was afterwards found that the coffin was empty.[55]
It is, of course, often difficult to say, in such cases as these, how
far elements of actual sensation co-operate in the production of the
illusions. Thus, in the case just mentioned, the odour of the earth may
have been the starting-point in the illusion. In many cases, however, an
imaginative mind appears to be capable of transforming a vivid
expectation into a nascent stage of sensation. Thus, a mother thinking
of her sick child in an adjoining room, and keenly on the alert for its
voice, will now and again fancy she really hears it when others hear
nothing at all.
_Transition to Hallucination._
It is plain that in these cases illusion approaches to hallucination.
Imagination, instead of waiting on sensation, usurps its place and
imitates its appearance. Such a "subjective" sensation produced by a
powerful expectation might, perhaps, by a stretch of language, be
regarded as an illusion, in the narrow sense, in so far as it depends on
the suggestive force of a complete set of external circumstances; on the
other hand, it is clearly an hallucination in so far as it is the
production of the semblance of an external impression without any
external agency corresponding to this.
In the class of illusory expectations just considered the immediately
present environment still plays a part, though a much less direct part
than that observable in the first large group of illusions. We will now
pass to a second mode of illusory expectation, where imagination is
still more detached from the present surroundings.
A common instance of this kind of expectation is the so-called
"intuition," or presentiment; that something is going to happen, which
expectation has no basis in fact. It does not matter whether the
expectation has arisen by way of another's words or by way of personal
inclinations. A strong wish for a thing will, in an exalted state of
mind, beget a vivid anticipation of it. This subject will be touched on
again under the Illusions of Belief. Here I am concerned to point out
that such presentiments are fertile sources of sense-illusion. The
history of Church miracles, visions, and the like amply illustrates the
effect of a vivid anticipation in falsifying the perceptions of external
things.
In persons of a lively imagination any recent occupation of the mind
with a certain kind of mental image may suffice to beget something
equivalent to a powerful mode of expectation. For example, we are told
by Dr. Tuke that on one occasion a lady, whose imagination had been
dwelling on the subject of drinking fountains, "thought she saw in a
road a newly erected fountain, and even distinguished an inscription
upon it, namely, 'If any man thirst, let him come unto Me, and drink.'
She afterwards found that what she had actually seen was only a few
scattered stones."[56] In many cases there seems to be a temporary
preternatural activity of the imagination in certain directions, of
which no very obvious explanation is discoverable. Thus, we sometimes
find our minds dwelling on some absent friend, without being able to
give any reason for this mental preoccupation. And in this way arise
strong temporary leanings to illusory perception. It may be said,
indeed, that all unwonted activity of the imagination, however it
arises, has as its immediate result a temporary mode of expectation,
definite or indefinite, which easily confuses our perceptions of
external things.
In proportion as this pre-existing imaginative impulse becomes more
powerful, the amount of actual impression necessary to transform the
mental image into an illusory perception becomes less; and, what is more
important, this transformation of the internal image involves a larger
and larger displacement of the actual impression of the moment. A man
whose mind is at the time strongly possessed by one kind of image, will
tend to project this outwards with hardly any regard to the actual
external circumstances.
This state of things is most completely illustrated in many of the
grosser illusions of the insane. Thus, when a patient takes any small
objects, as pebbles, for gold and silver, under the influence of the
dominant idea of being a millionaire, it is obvious that external
suggestion has very little to do with the self-deception. The confusions
into which the patient often falls with respect to the persons before
him show the same state of mind; for in many cases there is no
discoverable individual resemblance between the person actually present
and the person for whom he is taken.
It is evident that when illusion reaches this stage, it is scarcely
distinguishable from what is specially known as hallucination. As I have
remarked in setting out, illusion and hallucination shade one into the
other much too gradually for us to draw any sharp line of demarcation
between them. And here we see that hallucination differs from illusion
only in the proportion in which the causes are present. When the
internal imaginative impulse reaches a certain strength, it becomes
self-sufficient, or independent of any external impression.
This intimate relation between the extreme form of active illusion and
hallucination may be seen, too, by examining the physical conditions of
each. As I have already remarked, active illusion has for its
physiological basis a state of sub-excitation, or an exceptional
condition of irritability in the structures engaged in the act of
interpretative imagination. The greater the degree of this irritability,
the less will be the force of external stimulation needed to produce the
effect of excitation, and the more energetic will be the degree of this
excitation. Moreover, it is plain that this increase in the strength of
the excitation will involve an extension of the area of excitation till,
by-and-by, the peripheral regions of the nervous system may be involved
just as in the case of external stimulation. This accounts for the
gradual displacement of the impression of the moment by the mental
image. It follows that when the irritability reaches a certain degree,
the amount of external stimulus needed may become a vanishing quantity,
or the state of sub-excitation may of itself develop into one of full
activity.
_Hallucinations._
I do not propose to go very fully into the description and explanation
of hallucinations here, since they fall to a large extent under the
category of distinctly pathological phenomena. Yet our study of
illusions would not be complete without a glance at this part of the
subject.
Hallucination, by which I mean the projection of a mental image outwards
when there is no external agency answering to it, assumes one of two
fairly distinct forms: it may present itself either as a semblance of an
external impression with the minimum amount of interpretation, or as a
counterfeit of a completely developed percept. Thus, a visual
hallucination may assume the aspect of a sensation of light or colour
which we vaguely refer to a certain region of the external world, or of
a vision of some recognizable object. All of us frequently have
incomplete visual and auditory hallucinations of the first order,
whereas the complete hallucinations of the second order are
comparatively rare. The first I shall call rudimentary, the second
developed, hallucinations.
Rudimentary hallucinations may have either a peripheral or a central
origin. They may first of all have their starting-point in those
subjective sensations which, as we have seen, are connected with certain
processes set up in the peripheral regions of the nervous system. Or,
secondly, they may originate in a certain preternatural activity of the
sensory centres, or "sensorium," in what has been called by German
physiologists an automatic excitation of the central structures, which
activity may probably diffuse itself downwards to the peripheral regions
of the nerves. Baillarger would call hallucinations of the former class
"psycho-sensorial," those of the latter class purely "psychical,"
hallucinations.[57]
It is often a matter of great difficulty to determine which part of the
nervous system is originally concerned in these rudimentary
hallucinations. It is probable that in normal life they are most
frequently due to peripheral disturbance. And it seems reasonable to
suppose that where the hallucination remains in this initial stage of a
very incompletely interpreted visual or auditory impression, whether in
normal or abnormal life, its real physiological source is the periphery.
For the automatic excitation of the centres would pretty certainly issue
in the semblance of some definite, familiar variety of sense-impression
which, moreover, as a part of a complex state known as a percept, would
instantly present itself as a completely formed quasi-percept. In truth,
we may pretty safely argue that if it is the centre which is directly
thrown into a state of activity, it will be thrown into the usual
complex, that is to say, _perceptional_, mode of activity.
Let us now turn to hallucinations properly so called, that is to say,
completely developed quasi-percepts. These commonly assume the form of
visual or auditory hallucinations. Like the incomplete hallucinations,
they may have their starting-point either in some disturbance in the
peripheral regions of the nervous system or in the automatic activity of
the central structures: or, to use the language of Baillarger, we may
say that they are either "psycho-sensorial" or purely "psychical." A
subjective visual sensation, arising from certain conditions in the
retina and connected portions of the optic nerve, may by chance resemble
a familiar impression, and so be at once interpreted as an effect of a
particular external object. More frequently, however, the automatic
activity of the centres must be regarded, either in part or altogether,
as the physiological cause of the phenomenon. This is clearly the case
when, on the subjective side, the hallucination answers to a preceding
energetic activity of the imagination, as in the case of the visionary
and the monomaniac. Sometimes, however, as we have seen, the
hallucinatory percept answers to previous prolonged acts of perception,
leaving a kind of reverberation in the structures concerned; and in this
case it is obviously impossible to say whether the peripheral or central
regions (if either) have most to do with the hallucination.[58]
The classifications of the causes of hallucination to be met with in the
works of pathologists, bear out the distinction just drawn. Griesinger
tells us (_op. cit._, pp. 94, 95) that the general causes of
hallucination are: (1) Local disease of the organ of sense; (2) a state
of deep exhaustion either of mind or of body; (3) morbid emotional
states, such as fear; (4) outward calm and stillness between sleeping
and waking; and (5) the action of certain poisons, as haschisch, opium,
belladonna. The first cause points pretty distinctly to a peripheral
origin, whereas the others appear to refer mainly, if not exclusively,
to central derangements. Excessive fatigue appears to predispose the
central structures to an abnormal kind of activity, and the same effect
may be brought about by emotional agitation and by the action of
poisons. The fourth case mentioned here, absence of external
stimulation, would naturally raise the nervous structures to an
exceptional pitch of excitability. Such a condition would, moreover,
prove favourable to hallucination by blurring the distinction between
mental image and actual impression.
_Hallucinations of Normal Life._
In normal life, perfect hallucinations, in the strict sense as distinct
from illusions, are comparatively rare. Fully developed persistent
hallucinations, as those of Nicolai, the Berlin bookseller, and of Mrs.
A----, the lady cited by Sir D. Brewster, in his _Letters on Natural
Magic_, point to the presence of incipient nervous disorder. In healthy
life, on the other hand, while everybody is familiar with subjective
sensations such as flying spots, phosphenes, ringing in the ears, few
fall into the error of seeing or hearing distinct recognizable objects
in the absence of all external impressions. In the lives of eminent men
we read of such phenomena as very occasional events. Malebranche, for
example, is said to have heard the voice of God calling him. Descartes
says that, after a long confinement, he was followed by an invisible
person, calling him to pursue his search for truth. Dr. Johnson narrates
that he once heard his absent mother calling him. Byron tells us that he
was sometimes visited by spectres. Goethe records that he once saw an
exact counterpart of himself coming towards him. Sir Walter Scott is
said to have seen a phantom of the dead Byron. It is possible that all
of us are liable to momentary hallucinations at times of exceptional
nervous exhaustion, though they are too fugitive to excite our
attention.
When not brought on by exhaustion or artificial means, the
hallucinations of the sane have their origin in a preternatural power of
imagination. It is well known that this power can be greatly improved by
attention and cultivation. Goethe used to exercise himself in watching
for ocular spectra, and could at will transform these subjective
sensations into definite forms, such as flowers; and Johannes Müller
found he had the same power.[59] Stories are told of portrait painters
who could summon visual images of their sitters with a vividness equal
to that of reality, and serving all the purposes of their art. Mr.
Galton's interesting inquiries into the power of "visualizing" would
appear to prove that many people can at will sport on the confines of
the phantom world of hallucination. There is good reason to think that
imaginative children tend to confuse mental images and percepts.[60]
_The Hallucinations of Insanity._
The hallucinations of the insane are but a fuller manifestation of
forces that we see at work in normal life. Their characteristic is that
they simulate the form of distinctly present objects, the existence of
which is not instantly contradicted by the actual surroundings of the
moment.[61] The hallucinations have their origin partly in subjective
sensations, which are probably connected with peripheral disturbances,
partly and principally in central derangements.[62] These include
profound emotional changes, which affect the ruling mental tone, and
exert a powerful influence on the course of the mental images. The
hallucinations of insanity are due to a projection of mental images
which have, owing to certain circumstances, gained a preternatural
persistence and vividness. Sometimes it is the images that have been
dwelt on with passionate longing before the disease, sometimes those
which have grown most habitual through the mode of daily
occupation,[63] and sometimes those connected with some incident at or
near the time of the commencement of the disease.
In mental disease, auditory hallucinations play a part no less
conspicuous than visual.[64] Patients frequently complain of having
their thoughts spoken to them, and it is not uncommon for them to
imagine that they are addressed by a number of voices at the same
time.[65]
These auditory hallucinations offer a good opportunity for studying the
gradual growth of centrally originating hallucinations. In the early
stages of the disease, the patient partly distinguishes his
representative from his preservative sounds. Thus, he talks of sermons
being composed to him _in his head_. He calls these "internal voices,"
or "voices of the soul." It is only when the disease gains ground and
the central irritability increases that these audible thoughts become
distinctly projected as external sounds into more or less definite
regions of the environment. And it is exceedingly curious to notice the
different directions which patients give to these sounds, referring them
now to a quarter above the head, now to a region below the floor, and so
on.[66]
_Range of Sense-Illusions._
And now let us glance back to see the path we have traversed. We set out
with an account of perfectly normal perception, and found, even here, in
the projection of our sensations of colour, sound, etc., into the
environment or to the extremities of the organism, something which, from
the point of view of physical science, easily wears the appearance of an
ingredient of illusion.
Waiving this, however, and taking the word illusion as commonly
understood, we find that it begins when the element of imagination no
longer answers to a present reality or external fact in any sense of
this expression. In its lowest stages illusion closely counterfeits
correct perception in the balance of the direct factor, sensation, and
the indirect factor, mental reproduction or imagination. The degree of
illusion increases in proportion as the imaginative element gains in
force relatively to the present impression; till, in the wild illusions
of the insane, the amount of actual impression becomes evanescent. When
this point is reached, the act of imagination shows itself as a purely
creative process, or an hallucination.
While we may thus trace the progress of illusion towards hallucination
by means of the gradual increase in force and extent of the imaginative,
or indirect, as opposed to the sensuous, or direct, element in
perception, we have found a second starting-point for this movement in
the mechanism of sensation, involving, as it does, the occasional
production of "subjective sensations." Such sensations constitute a
border-land between the regions of illusion in the narrow sense, and
hallucination. In their simplest and least developed form they may be
regarded, at least in the case of hearing and sight, as partly
hallucinatory; and they serve as a natural basis for the construction of
complete hallucinations, or hallucinatory percepts.
In these different ways, then, the slight, scarcely noticeable illusions
of normal life lead up to the most startling hallucinations of abnormal
life. From the two poles of the higher centres of attention and
imagination on the one side, and the lower regions of nervous action
involved in sensation on the other side, issue forces which may, under
certain circumstances, develop into full hallucinatory percepts. Thus
closely is healthy attached to morbid mental life. There seems to be no
sudden break between our most sober every-day recognitions of familiar
objects and the wildest hallucinations of the demented. As we pass from
the former to the latter, we find that there is never any abrupt
transition, never any addition of perfectly new elements, but only that
the old elements go on combining in ever new proportions.
The connection between the illusory side of our life and insanity may be
seen in another way. All illusion has as its negative condition an
interruption of the higher intellectual processes, the due control of
our mental representations by reflection and reason. In the case of
passive illusions, the error arises from our inability to subordinate
the suggestion made by some feature of the present impression to the
result of a fuller inspection of the object before us, or of a wider
reflection on the past. In other words, our minds are dominated by the
partial and the particular, to the exclusion of the total or the
general. In active illusions, again, the powers of judgment and
reflection, including those of calm perception itself, temporarily
vacate their throne in favour of imagination. And this same suspension
of the higher intellectual functions, the stupefaction of judgment and
reflection made more complete and permanent, is just what characterizes
insanity.
We may, perhaps, express this point of connection between the illusions
of normal life and insanity by help of a physiological hypothesis. If
the nervous system has been slowly built up, during the course of human
history, into its present complex form, it follows that those nervous
structures and connections which have to do with the higher intellectual
processes, or which represent the larger and more general relations of
our experience, have been most recently evolved. Consequently, they
would be the least deeply organized, and so the least stable; that is
to say, the most liable to be thrown _hors de combat_. This is what
happens temporarily in the case of the sane, when the mind is held fast
by an illusion. And, in states of insanity, we see the process of
nervous dissolution beginning with these same nervous structures, and so
taking the reverse order of the process of evolution.[67] And thus, we
may say that throughout the mental life of the most sane of us, these
higher and more delicately balanced structures are constantly in danger
of being reduced to that state of inefficiency, which in its full
manifestation is mental disease.
Does this way of putting the subject seem alarming? Is it an appalling
thought that our normal mental life is thus intimately related to
insanity, and graduates away into it by such fine transitions? A
moment's reflection will show that the case is not so bad as it seems.
It is well to remind ourselves that the brain is a delicately adjusted
organ, which very easily gets disturbed, and that the best of us are
liable to become the victims of absurd illusion if we habitually allow
our imaginations to be overheated, whether by furious passion or by
excessive indulgence in the pleasures of day-dreaming, or in the
intoxicating mysteries of spiritualist _séances_. But if we take care to
keep our heads cool and avoid unhealthy degrees of mental excitement, we
need not be very anxious on the ground of our liability to this kind of
error. As I have tried to show, our most frequent illusions are
necessarily connected with something exceptional, either in the
organism or in the environment. That is to say, it is of the nature of
illusion in healthy conditions of body and mind to be something very
occasional and relatively unimportant. Our perceptions may be regarded
as the reaction of the mind on the impressions borne in from the
external world, or as a process of adjustment of internal mental
relations to external physical relations. If this process is, in the
main, a right one, we need not greatly trouble, because it is not
invariably so. We should accept the occasional failure of the
intellectual mechanism as an inseparable accompaniment of its general
efficiency.
To this it must be added that many of the illusions described above can
hardly be called cases of non-adaptation at all, since they have no
relation to the practical needs of life, and consequently are, in a
general way, unattended to. In other cases, again, namely, where the
precise nature of a present sensation, being practically an unimportant
matter, is usually unattended to, as in the instantaneous recognition of
objects by the eye under changes of illumination, etc., the illusion is
rather a part of the process of adaptation, since it is much more
important to recognize the permanent object signified by the sensation
than the precise nature of the present sensational "sign" itself.
Finally, it should never be forgotten that in normal states of mind
there is always the possibility of rectifying an illusion. What
distinguishes abnormal from normal mental life is the persistent
occupation of the mind by certain ideas, so that there is no room for
the salutary corrective effect of reflection on the actual impression
of the moment, by which we are wont to "orientate," or take our bearings
as to the position of things about us. In sleep, and in certain
artificially produced states, much the same thing presents itself.
Images become realities just because they are not instantly recognized
as such by a reference to the actual surroundings of the moment. But in
normal waking life this power of correction remains with us. We may not
exercise it, it is true, and thus the illusion will tend to become more
or less persistent and recurring; for the same law applies to true and
to false perception: repetition makes the process easier. But if we only
choose to exert ourselves, we can always keep our illusions in a nascent
or imperfectly developed stage. This applies not only to those
half-illusions into which we voluntarily fall, but also to the more
irresistible passive illusions, and those arising from an over-excited
imagination. Even persons subject to hallucinations, like Nicolai of
Berlin, learn to recognize the unreal character of these phantasms. On
this point the following bit of autobiography from the pen of Coleridge
throws an interesting light. "A lady (he writes) once asked me if I
believed in ghosts and apparitions. I answered with truth and
simplicity, No, madam, I have seen far too many myself."[68] However
irresistible our sense-illusions may be, so long as we are under the
sway of particular impressions or mental images, we can, when resolved
to do so, undeceive ourselves by carefully attending to the actual
state of things about us. And in many cases, when once the correction is
made, the illusion seems an impossibility. By no effort of imagination
are we able to throw ourselves back into the illusory mental condition.
So long as this power of dispelling the illusion remains with us, we
need not be alarmed at the number and variety of the momentary
misapprehensions to which we are liable.