[APPENDIX]
Dreaming and Hypnosis
I am assured that a lady of a well-known court saw in a dream and described to her friends the person she afterwards married, and the hall in which the betrothal was celebrated; and she did this before she had seen or known either the man or the place. They attributed the circumstance to some indefinite secret presentiment; but chance may produce this effect, since it is quite rare that it happens; besides, dream-images being somewhat obscure, there is more liberty in connecting them afterwards with certain others.—Gottfried Wilhelm Leibniz
§ 79. Sleep and Dream.—The profound sleep that comes to us every night, and that we take entirely as a matter of course, rests without any doubt upon an instinctive tendency; but there can be little doubt, either, that the instinct has been modified in the course of human evolution. It seems probable, indeed, that profound sleep, the lapse of all but the vegetative organic functions, has been developed from the same fundamental tendency as hypnosis, so that natural sleep and artificial hypnosis represent two branches which spring from a single stem. This original and instinctive tendency is toward what we may call, in biological phrase, a partial or defensive sleep, a rest enjoyed while the animal is still partly on guard. It underlies the sleep of the mother, who is roused at once by the movement of her infant child; the sleep of the nurse, who is awaked by the restlessness of her patient; the sleep of the tired horseman or driver, who keeps the saddle or holds the reins, and remains alive to any sign of uneasiness on the part of his horse. It shows also in the ability of the wearied surgeon to rouse himself and perform an operation, though he falls asleep once more the moment it is over and has no remembrance of it at his normal waking. Such a partial rest, persisting only thus occasionally in the life of civilised man, is all that an animal surrounded by dangers can afford; if sight and smell and taste may be allowed to lapse, still touch and hearing must keep awake,—must keep awake, at any rate, to the kind of stimulus that spells danger. We are speaking now in figurative terms; the history and nervous mechanism of the sleep-tendency offer a problem to science, and must be scientifically worked out; but it is enough here if you get a general notion of the way in which sleep began.
In process of time, as dangers grow less or as the nightly care of the community is put into the hands of watchmen whose special duty it is to signal their approach, sleep becomes total and profound. Even our own protected sleep, however, is not always undisturbed. We resign ourselves to it with a full sense of security; and we go to sleep in a dark and quiet room, we rid ourselves of the friction of clothes, we keep a constant temperature in our bedroom, we lie down. Sleep, nevertheless, is interrupted, more or less often according to age and constitution, by a dream, by a series of experiences like those of the waking life; and sometimes the dream is accompanied by muscular activity; we talk or walk in our sleep.
The dream, then, is subject-matter for psychology; and the first question that we have to ask about it concerns its make-up; of what mental processes is the dream composed? The answer is twofold. So far as pattern goes, anything whatsoever may appear in the dream-state: perception, memory, emotion, imagination, thought, everything. But as regards the mental processes themselves, the dream is selective; certain processes are preferred for dreaming, so to say, as certain processes are preferred for the representation of self. The details of dreams are very quickly forgotten; and there is always danger lest recall and report, in the waking state, change the terms of a dream, translate them from their original mode into the customary terms of waking experience. We have, however, a large number of records, taken under favourable conditions, and we find substantial agreement among the various observers. Dreams are mainly visual, though lights are more and colours are less common, perhaps, than is ordinarily supposed. Next in order of frequency to vision stands audition; conversation, especially, is a common feature of dreams. Next follow sense-feelings and feeling-attitudes; unpleasant experiences seem, on the whole, to be more frequent than pleasant, though there are marked individual differences. Thereafter, at a wide remove, come touch and kinæsthesis and organic complexes; and last of all, taste and smell.
We know so little of the nervous correlates of the dream that a discussion of these facts must of necessity be speculative. It has been said that we dream largely in terms of sight for the same reason that we remember and imagine largely in those terms (‘dream’ is, for that matter, the older English word for ‘imagine’): the eye is the most important of all the sense-organs, the organ most continuously used, and the organ most relied upon for knowledge of the outside world; hence the visual centre of the brain has multitudinous connections with all the other brain-centres, and is readily excited when any one of them is excited. It has been pointed out, also, that the eye is extremely sensitive to slight changes of illumination, as well as to changes in the pressure of the eyelids, the state of circulation in the retina, and so forth; and that the sensations thus set up are reinforced by the persistent central grey. Observation has proved that the figures of a dream-scene may roughly correspond with the dots and splashes of light and colour that you see over the dark field of vision just before you fall asleep. So in regard to hearing: it may be said that verbal perceptions and ideas are, in the waking life, subordinate in number and importance only to those of vision; and it may be said, also, that the ear is the great defensive organ of the night-time, so that ear-sleep (if we may coin the word) is rarely profound, and the ear is liable to excitation by any chance crack or rustle in our surroundings, even by the pulsing of the blood through its own vessels. Here, indeed, we raise the whole difficult question of the origination of dreams. We cannot say that a dream may not arise ‘in the brain’ altogether apart from stimulation of a sense-organ; yet the sense-organs are always liable to stimulation, from without or from within; we know that stimuli, too weak to arouse a sleeper, will set up dreams; and it seems safe to conclude that most dreams are originated by sensory stimulation, while their subsequent course is due to associative and perhaps to determining tendencies active at the moment. Attempts have been made to refer certain familiar kinds of dream—dreams of flying, falling, appearing in public scantily clothed, preparing for a journey, etc.—to particular forms of stimulus: arrest of heart-beat, irregular breathing, cold from the slipping down of bed-clothes, etc.; but no positive correlation has been arrived at.
Dreams are ordinarily regarded as the type of fantastic and disordered experience, “the children of an idle brain, begot of nothing but vain fantasy”; and some dreams, it is true, are very fragmentary, and some dream-combinations seem ridiculous enough to the waking judgement, and some shifts of dream-scene are startlingly abrupt. It may be questioned, nevertheless, whether the changes are in fact more sudden or more radical than those of the waking life, and whether the grouping is more fantastic than in the day-dream. The great perceptive attitudes remain for the most part unchanged. We notice, on later reflection, that time may be curiously foreshortened, so that we have the events of a day crowded into a few seconds; but this is due partly to the occurrence of attitudes, of the nutshell-packing of experiences (p. 271), such as we find also in our waking memories, and partly to our own reflective reading of the dream; we, who are now awake, distribute the events over a day, much as the novelist may do in telling his story, or the playwright in developing his plot. The sense of personal identity is rarely lost; and the dream frequently reflects the personality of the dreamer; temperament, interests, principles, show themselves in it; no one of us could dream his neighbour’s dreams. In general, too, the dream plays about a topic or situation; and if the changes are both sudden and profound, we must remember that our waking trains are held in course, as dreams are not, by the continuity of the stimuli around us, and that even so we are often interrupted in a current train, and shift from topic to topic at a moment’s notice. The dream is under no external control by an environment, nor is it as a rule organised and regulated throughout by a dominant determining tendency, as is the case with thought and constructive imagination. It is subject, however, to the laws of associative tendency, and sometimes at any rate it seems to issue from a determination; a dream may, for example, be continued on successive nights. On the whole, then, dream-experience is less disorderly than is usually supposed. Our statements must be guarded: we cannot say that the perceptive attitudes are never disturbed; we know that personality may be greatly modified; we know that scene may follow scene in the most bizarre way. The whole trend of popular psychology, however, is to emphasize the differences between dreaming and waking, while the trend of accurate observation is to bring them together.