DREAM, the state of consciousness during sleep; it may also be defined as a hallucination or illusion peculiarly associated with the condition of sleep, but not necessarily confined to that state (from a root dreug, connected with Ger. triigen, to deceive). In sleep the withdrawal of the mind from the external world is more complete and the objectivity of the dream images is usually un questioned, whereas in the waking state the hallucination is usually recognized as such; we may, however, be conscious that we are dreaming, and thus in a measure be aware of the hallucinatory character of our percepts. The physiological nature of sleep (q.v.; see also MUSCLE and NERVE) and of dreaming is obscure. As a rule the control over the voluntary muscles in dreams is slight; the sleep-walker is the exception and not the rule, and the motor activity represented in the dream is seldom realized in practice, largely, no doubt, because we are ignorant, under these circum stances, of the spatial relations of our bodies. Among the psycho logical problems raised by dreams are the condition of attention, which is variously regarded as altogether absent or as fixed, the extent of mental control, and the relation of ideas and motor im pulses. There is present in all dreams a certain amount of dis sociation of consciousness, or of obstructed association, which may manifest itself in the preliminary stage of drowsiness by such phenomena as the apparent transformation or inversion of the words of a book. We may distinguish two types of dreams, (a) representative or centrally initiated, (b) presentative or due to the stimulation of the end organs of sense. In both cases, the dream having once been initiated, we are concerned with a combination of ideas suggested by resemblances or other associative elements. The false reasoning of dreams is due in the first place to the absence, to a large extent, of the memory elements on which our ordinary reasoning depends, and, secondly, to the absence of the normal supply of sensory elements.
(a) The state of the stomach, heart, etc., has long been rec ognized as important in the causation of dreams (see below, Classical Views). The common sensation of flying seems to be due in many cases to the disturbance of these organs setting up sensations resembling those felt in rapidly ascending or descending, as in a swing or a lift. Indigestion is a frequent cause of night mare—the name given to oppressive and horrible dreams—and bodily discomfort is sometimes translated into the moral region, giving rise to the dream that a murder has been committed. (b) Dreams of flying, etc., have also been attributed to the condition of the muscles during sleep; W. Wundt remarks that the move ments of the body, such as breathing, extensions of the limbs and so on, must give rise to dream fancies; the awkward position of the limbs may also excite images. (c) Especially important, prob ably, for the dreams of the early part of the night are the retinal conditions to which are due the illusions hypnagogiques of the preliminary drowsy stage; but probably Ladd goes too far in maintaining that entoptic stimuli, either intra- or extra-organic in origin, condition all dreams. Illusions hypnagogiques, termed popularly "faces in the dark," of which Maury has given a full account, are the not uncommon sensations experienced, usually visual and seen with both open and closed eyes, in the interval between retiring to rest and actually falling asleep; they are comparable to the crystal-gazing visions of waking moments; though mainly visual they may also affect other senses. Besides the eye the ear may supply material for dreams, when the circula tion of the blood suggests rushing waters or similar ideas. (d) It is a matter of common observation that the temperature of the surface of the body determines in many cases the character of the dreams, the real circumstances, as might be expected from the general character of the dream state, being exaggerated. In the same way the pressure of bed-clothes, obstruction of the supply of air, etc., may serve as the starting-point of dreams. The common dream of being unclothed may perhaps be due to this cause, the sensations associated with clothing being absent or so far modified as to be unrecognizable. In the same way the absence of foot-gear may account for some dreams of flying. It is possible to test the influence of external stimuli by direct experiment ; Maury made a number of trials with the aid of an assistant.
The relation between the memory in dreams and in the hypnotic trance is curious : suggestions given in the trance may be accepted and then forgotten or never remembered in ordinary life ; this does not prevent them from reappearing occasionally in dreams; conversely dreams forgotten in ordinary life may be remembered in the hypnotic trance. These dream memories of other states of consciousness suggest that dreams are sometimes the product of a deeper stratum of the personality than comes into play in ordi nary waking life. It must be remembered in this connection that we judge of our dream consciousness by our waking recollections, not directly, and our recollection of our dreams is extraordinarily fragmentary ; we do not know how far our dream memory really extends. Connected with memory of other states is the question of memory in dreams of previous dream states; occasionally a separate chain of memory, analogous to a secondary personality, seems to be formed. We may be also conscious that we have been dreaming, and subsequently, without intermediate waking, relate as a dream the dream previously experienced. In spite of the irrationality of dreams in general, it by no means follows that the earlier and later portions of a dream do not cohere; we may interpolate an episode and again take up the first motive, exactly as happens in real life. The strength of the dream memory is shown by the recurrence of images in dreams; a picture, the page of a book, or other image may be reproduced before our eyes several times in the course of a dream without the slightest alter ation, although the waking consciousness would be quite incapable of such a feat of visualizing. In this connection may be mentioned the phenomenon of redreaming; the same dream may recur either on the same or on different nights; this seems to be in many cases pathological or due to drugs, but may also occur under normal conditions.
Personality.—As a rule the personality of the dreamer is un changed; but it also happens that the confusion of identity ob served with regard to other objects embraces the dreamer him self ; he imagines himself to be some one else ; he is alternately actor and observer; he may see himself playing a part or may divest himself of his body and wander incorporeally. Ordinary dreams, however, do not go beyond a splitting of personality; we hold conversations, and are intensely surprised at the utter ances of a dream figure, which, however, is merely an alter ego. As in the case of Hilprecht (see above) the information given by another part of the personality may not only appear but actually be novel.
Voluntary Action in Dreams.—Connected with dreams volun tarily influenced is the question of how far dreams once initiated are modifiable at the will of the dreamer. Some few observers, like F. W. H. Myers and Dr. F. van Eeden, record that they can at longer or shorter intervals control their actions in their dreams, though usually to a less extent than their imagined actions in waking life. Dr. van Eeden, for example, tells us that he has what he calls a "clear dream" once a month and is able to pre determine what he will do when he becomes aware that he is dreaming.
Dreams of Children.—Opinions differ widely as to the age at which children begin to dream ; G. Compayre maintains that dreaming has been observed in the fourth month, but reflex action is always a possible explanation of the observed facts. S. de Sanctis found that in boys of eleven only one out of eight said that he dreamt seldom, as against four out of seven at the age of six ; but we cannot exclude the possibility that dreams were frequent but forgotten.
Dreams of the Old.—In normal individuals above the age of 65 de Sanctis found dreams were rare ; atmospheric influences seem to be important elements in causing them; memory of them is weak ; they are emotionally poor, and deal with long past scenes.
In the matter of complication of dream experiences the sexes are about equal; daily life supplies more material in the dreams of men ; nearly twice as many women as men remember their dreams clearly, a fact which hangs together to some extent with the vividness of the dreams, though it by no means follows that a vivid dream is well remembered. There are great variations in the emotional character of dreams; some observers report twice as many unpleasant dreams as the reverse ; in other cases the emotions seem to be absent ; others again have none but pleasing dreams. Individual experience also varies very largely as to the time when most dreams are experienced ; in some cases the great majority are subsequent to 6 :30 A.M. ; others find that quite half occur before 4 A.M.
Dreams of the Blind, Deaf, etc.—As regards visual dreams the blind fall into three classes—(1) those who are blind from birth or become blind before the age of five; (2) those who become blind at the "critical age" from five to seven; (3) those who be come blind after the age of seven. The dreams of the first class are non-visual; but in the dreams of Helen Keller there are traces of a visual content ; the second class sometimes has visual dreams ; the third class does not differ from normal persons, though visual dreams may fade away after many years of blindness. In the case of the partially blind the clearness of vision in a dream exceeds that of normal life when the partial loss of sight occurred in the sixth or later years. The education of Helen Keller is interesting from another point of view ; of ter losing the senses of sight and hearing in infancy she began her education at seven years and was able to articulate at eleven ; it is recorded that she "talked" in her dreams soon after. This accords with the experience of normal individuals who acquire a foreign language. Her extraordinary memory enables her to recall faintly some traces of the sunlit period of her life, but they hardly affect her dreams, so far as can be judged. The dreams of the blind, accord ing to the records of F. Hitschmann, present some peculiarities; animals as well as man speak; toothache and bodily pains are perceived as such ; impersonal dreaming, taking the form of a drama or reading aloud, is found; and he had a strong tendency to reproduce or create verse.
Dreams of Animals.—We are naturally reduced to inference in dealing with animals as with very young children; but various observations seem to show that dreams are common in older dogs, especially after hunting expeditions ; in young dogs sleep seems to be quieter; dogs accustomed to the chase seem to dream more than other kinds.
There are two classes of dreams which have a special impor tance in the lower cultures: (I) the dream or vision of the initia tion fast ; and (2) the dream caused by the process known as incubation, which is often analogous to the initiation fast. In many parts of North America the individual Indian acquires a tutelary spirit, known as manito or nagual, by his initiation dream or vision; the idea being, perhaps, that the spirit by the act of appearing shows its subjection to the will of the man. Simi larly, the magician acquires his familiar in North America, Aus tralia and elsewhere by dreaming of an animal. Incubation con sists in retiring to sleep in a temple, sometimes on the top of a mountain or other unusual spot, in order to obtain a revelation through a dream. Fasting, continence and other observances are frequently prescribed as preliminaries. Certain classes of dreams have, especially in the middle ages, been attributed to the influence of evil spirits (see DEMONOLOGY).
Classical and Mediaeval Views of Dreams.—Side by side with the prevalent animistic view of dreams we find in antiquity and among the semi-civilized attempts at philosophical or physio logical explanations of dreams. Democritus, from whom the Epicureans derived their theory, held the cause of them to be the simulacra or phantasms of corporeal objects which are con stantly floating about the atmosphere and attack the soul in sleep--a view hardly distinguishable from animism. Aristotle, however, refers them to the impressions left by objects seen with the eyes of the body ; he further remarks on the exaggera tion of slight stimuli when they are incorporated into a dream; a small sound becomes a noise like thunder. Plato, too, connects dreaming with the normal waking operations of the mind; Pliny, on the other hand, admits this only for dreams which take place after meals, the remainder being supernatural. Cicero, however, takes the view that they are simply natural occurrences no more and no less than the mental operations and sensations of the waking state. The pathological side of dreams attracted the notice of physicians. Hippocrates was disposed to admit that some dreams might be divine, but held that others were premonitory of diseased states of the body. Galen took the same view in some of his speculations.
Symbolical interpretations are combined with pathological no less than animistic interpretations of dreams; they are also ex tremely common among the lower classes in Europe at the present day, but in this case no consistent explanation of their importance for the divination of future events is usually discover able. Among the Greeks Plato in the Timaeus (ch. xlvi., xlvii.) explains dreams as prophetic visions received by the lower appe titive soul through the liver ; their interpretation requires intelli gence. The Stoics seem to have held that dreams may be a divine revelation and more than one volume on the interpretation of dreams has come down to us, the most important being perhaps the 'OvetpoKpLTLtca of Daldianus Artemidorus. We find parallels to this in a Muslim work by Gabdorrachaman, translated by Pierre Vattier under the name of Onirocrite mussulman, and in the numerous books on the interpretation of dreams which cir culate at the present day. In Siam dream books are found (Intern. Archiv fur Antler. viii. i so) ; one of the functions of the Australian medicine man is to decide how a dream is to be interpreted.
Modern Views.—The doctrine of Descartes that existence depended upon thought naturally led his followers to maintain that the mind is always thinking and consequently that dreaming is continuous. Locke replied to this that men are not always conscious of dreaming, and it is hard to be conceived that the soul of the sleeping man should this moment be thinking, while the soul of the waking man cannot recollect in the next moment a jot of all those thoughts. That we always dream was main tained by Leibniz, Kant, Sir. W. Hamilton and others; the latter refutes the argument of Locke by the just observation that the somnambulist has certainly been conscious, but fails to recall the fact when he returns to the normal state.
It has been commonly held by metaphysicians that the nature of dreams is explained by the suspension of volition during sleep; Dugald Stewart asserts that it is not wholly dormant but loses its hold on the faculties, and he thus accounts for the incoherence of dreams and the apparent reality of dream images.
Cudworth, from the orderly sequence of dream combinations and their novelty, argues that the state arises, not from any "fortuitous dancings of the spirits," but from the "phantastical power of the soul." According to K. A. Schemer, dreaming is a decentralization of the movement of life; the ego becomes purely receptive and is merely the point around which the peripheral life plays in perfect freedom. Hobbes held that dreams all proceed from the agitation of the inward parts of a man's body, which, owing to their connection with the brain, serve to keep the latter in motion. For Schopenhauer the cause of dreams is the stimulation of the brain by the internal regions of the organ ism through the sympathetic nervous system. These impressions the mind afterwards works up into quasi-realities by means of its forms of space, time, causality, etc.