“Nerve stimulus” and “bodily stimulus,” then, would be the somatic sources of the dream—that is, the only sources whatever of the dream, according to several authors.
But we have already found a number of doubts, which seem to attack not so much the correctness of the somatic theory of stimulation as its adequacy.
However certain all the representatives of this theory may have felt about the actual facts on which it is based—especially in case of the accidental and external nerve stimuli, which may be recognised in the content of the dream without any trouble—nevertheless none of them has been able to avoid the admission that the abundant ideal content of dreams does not admit of explanation by external nerve-stimuli alone. Miss Mary Whiton Calkins[[12]] has tested her own dreams and those of another person for a period of six weeks with this idea in mind, and has found only from 13·2 per cent. to 6·7 per cent. in which the element of external sensory perception was demonstrable; only two cases in the collection could be referred to organic sensations. Statistics here confirm what a hasty glance at our own experience might have led us to suspect.
The decision has been made repeatedly to distinguish the “dream of nerve stimulus” from the other forms of the dream as a well-established sub-species. Spitta[[64]] divided dreams into dreams of nerve stimulus and association dreams. But the solution clearly remained unsatisfactory as long as the link between the somatic sources of dreams and their ideal content could not be demonstrated.
Besides the first objection, of the inadequate frequency of external exciting sources, there arises as a second objection the inadequate explanation of dreams offered by the introduction of this sort of dream sources. The representatives of the theory accordingly must explain two things, in the first place, why the external stimulus in the dream is never recognised according to its real nature, but is regularly mistaken for something else (cf. the alarm-clock dreams, p. 22), and secondly, why the reaction of the receiving mind to this misrecognised stimulus should result so indeterminately and changefully. As an answer to these questions, we have heard from Strümpell[[66]] that the mind, as a result of its being turned away from the outer world during sleep, is not capable of giving correct interpretation to the objective sensory stimulus, but is forced to form illusions on the basis of the indefinite incitements from many directions. As expressed in his own words (p. 108):
“As soon as a sensation, a sensational complex, a feeling, or a psychic process in general, arises in the mind during sleep from an outer or inner nerve-stimulus, and is perceived by the mind, this process calls up sensory images, that is to say, earlier perceptions, either unembellished or with the psychic values belonging to them, from the range of waking experiences, of which the mind has remained in possession. It seems to collect about itself, as it were, a greater or less number of such images, from which the impression which originates from the nerve-stimulus receives its psychic value. It is usually said here, as the idiom does of waking thought, that the mind interprets impressions of nerve-stimuli in sleep. The result of this interpretation is the so-called nerve-stimulus dream—that is to say, a dream whose composition is conditioned by the fact that a nerve-stimulus brings about its effect in psychic life according to the laws of reproduction.”
The opinion of Wundt[[76]] agrees in all essentials with this theory. He says that the ideas in the dream are probably the result, for the most part, of sensory stimuli, especially of those of general sensation, and are therefore mostly phantastic illusions—probably memory presentations which are only partly pure, and which have been raised to hallucinations. Strümpell has found an excellent simile (p. 84). It is as “if the ten fingers of a person ignorant of music should stray over the keyboard of an instrument”—to illustrate the relation between dream content and dream stimuli, which follows from this theory. The implication is that the dream does not appear as a psychic phenomenon, originating from psychic motives, but as the result of a physiological stimulus, which is expressed in psychic symptomology, because the apparatus which is affected by the stimulus is not capable of any other expression. Upon a similar assumption is based, for example, the explanation of compulsive ideas which Meynert tried to give by means of the famous simile of the dial on which individual figures are prominent because they are in more marked relief.
However popular this theory of somatic dream stimuli may have become, and however seductive it may seem, it is nevertheless easy to show the weak point in it. Every somatic dream stimulus which provokes the psychic apparatus to interpretation through the formation of illusions, is capable of giving rise to an incalculable number of such attempts at interpretation; it can thus attain representation in the dream content by means of an extraordinary number of different ideas. But the theory of Strümpell and Wundt is incapable of instancing any motive which has control over the relation between the external stimulus and the dream idea which has been selected to interpret it, and therefore of explaining the “peculiar choice” which the stimuli “often enough make in the course of their reproductive activity” (Lipps, Grundtatsachen des Seelenlebens, p. 170). Other objections may be directed against the fundamental assumption of the whole theory of illusions—the assumption that during sleep the mind is not in a condition to recognise the real nature of the objective sensory stimuli. The old physiologist Burdach[[8]] proves to us that the mind is quite capable even during sleep of interpreting correctly the sensory impressions which reach it, and of reacting in accordance with the correct interpretation. He establishes this by showing that it is possible to exempt certain impressions which seem important to the individuals, from the neglect of sleeping (nurse and child), and that one is more surely awakened by one’s own name than by an indifferent auditory impression, all of which presupposes, of course, that the mind distinguishes among sensations, even in sleep (Chapter I., p. 41). Burdach infers from these observations that it is not an incapability of interpreting sensory stimuli in the sleeping state which must be assumed, but a lack of interest in them. The same arguments which Burdach used in 1830, later reappear unchanged in the works of Lipps in the year 1883, where they are employed for the purpose of attacking the theory of somatic stimuli. According to this the mind seems to be like the sleeper in the anecdote, who, upon being asked, “Are you asleep?” answers “No,” and upon being again addressed with the words, “Then lend me ten florins,” takes refuge in the excuse: “I am asleep.”
The inadequacy of the theory of somatic dream stimuli may also be demonstrated in another manner. Observations show that I am not urged to dream by external stimulations, even if these stimulations appear in the dream as soon as, and in case that, I dream. In response to the tactile or pressure stimulus which I get while sleeping, various reactions are at my disposal. I can overlook it and discover only upon awakening that my leg has been uncovered or my arm under pressure; pathology shows the most numerous examples where powerfully acting sensory and motor stimuli of different sorts remain without effect during sleep. I can perceive a sensation during sleep through and through sleep, as it were, which happens as a rule with painful stimuli, but without weaving the pain into the texture of the dream; thirdly, I can awaken on account of the stimulus in order to obviate it. Only as a fourth possible reaction, I may be impelled to dream by a nerve stimulus; but the other possibilities are realised at least as often as that of dream formation. This could not be the case if the motive for dreaming did not lie outside of the somatic sources of dreams.
Taking proper account of the defect in the explanation of dreams by somatic stimuli which has just been shown, other authors—Scherner,[[58]] who was joined by the philosopher Volkelt[[72]]—have tried to determine more exactly the psychic activities which cause the variegated dream images to arise from the somatic stimuli, and have thus transferred the essential nature of dreams back to the province of the mind, and to that of psychic activity. Scherner not only gave a poetically appreciative, glowing and vivid description of the psychic peculiarities which develop in the course of dream formation; he also thought he had guessed the principle according to which the mind proceeds with the stimuli that are at its disposal. The dream activity, according to Scherner—after phantasy has been freed from the shackles imposed upon it during the day, and has been given free rein—strives to represent symbolically the nature of the organ from which the stimulus proceeds. Thus we have a kind of dream-book as a guide for the interpretation of dreams, by means of which bodily sensations, the conditions of the organs and of the stimuli may be inferred from dream images. “Thus the image of a cat expresses an angry discontented mood, the image of a light-coloured bit of smooth pastry the nudity of the body. The human body as a whole is pictured as a house by the phantasy of the dream, and each individual organ of the body as a part of the house. In ‘toothache-dreams’ a high vaulted vestibule corresponds to the mouth and a stair to the descent of the gullet to the alimentary canal; in the ‘headache-dream’ the ceiling of a room which is covered with disgusting reptile-like spiders is chosen to denote the upper part of the head” (Volkelt, p. 39). “Several different symbols are used by the dream for the same organ, thus the breathing lungs find their symbol in an oven filled with flames and with a roaring draught, the heart in hollow chests and baskets, and the bladder in round, bag-shaped objects or anything else hollow. It is especially important that at the end of a dream the stimulating organ or its function be represented undisguised and usually on the dreamer’s own body. Thus the ‘toothache-dream’ usually ends by the dreamer drawing a tooth from his own mouth” (p. 35). It cannot be said that this theory has found much favour with the authors. Above all, it seems extravagant; there has been no inclination even to discover the small amount of justification to which it may, in my opinion, lay claim. As may be seen, it leads to a revival of the dream interpretation by means of symbolism, which the ancients used, except that the source from which the interpretation is to be taken is limited to the human body. The lack of a technique of interpretation which is scientifically comprehensible must seriously limit the applicability of Scherner’s theory. Arbitrariness in dream interpretation seems in no wise excluded, especially since a stimulus may be expressed by several representations in the content of the dream; thus Scherner’s associate, Volkelt, has already found it impossible to confirm the representation of the body as a house. Another objection is that here again dream activity is attributed to the mind as a useless and aimless activity, since according to the theory in question the mind is content with forming phantasies about the stimulus with which it is concerned, without even remotely contemplating anything like a discharge of the stimulus.