Illusions, James Sully [speld decodable readers .TXT] 📗

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