This is the ninth Chapter from the online book: Living Ethics: The Way of Wholeness. See: 1) How Should We Live? 2) Ethics and Civilization 3) Worldview and Ethics 4) Self View and Ethics 5) World as System 6) The Material Cosmos 7) Biological Systems 8) Human Systems
Donivan Bessinger, MD
We are such stuff as dreams are made on. —Shakespeare (1)
Who am I? In ordinary experience, I am known to others as a particular human body with its characteristic set of behaviors that identify me as an individual person, known by a certain name. In my ordinary experience of myself, I recognize those descriptive qualities too, but I am aware of a collection of memories, thoughts and motivations which are uniquely my own, and which give my view of myself a richness that can not fully be known to others. (Indeed, I protect that collection from full view, as though by a mask.) I can generally account for those contents on the basis of the history of my contacts with the outer world.
However, I am also aware of internal experiences that seem to have arisen without benefit of any external teaching or relationship to the experience of others in my conscious world. I cannot account for dreams, slips of the tongue or pen, active fantasies or impulsive thoughts or behaviors in which I seem to be “not myself.” These seem somehow to originate outside that conscious mental compartment, and to intrude into it. I may speculate that they originate from the outer world, by some magical or otherwise unknown means. Yet however I explain them, I must agree that there is some part of me that is not conscious.
Attempting to deal with these concepts and to express the entire functioning of the person has given rise to a variety of descriptive terms which often shift their meaning. The material structure (anatomy) with its various organic functions presents no particular semantic problem: We describe it as body (Greek soma). Yet psyche can mean the entire realm of human non-body function, in the sense of “total psyche.” (2) But psyche can also mean only the unconscious aspect, distinguished from the conscious thinking realm of mind. And sometimes “mind” means psyche. When “it’s all in the mind,” one can only guess where it is.
But if our worldview is to express a complete “cosmos in common” for understanding and discussing our world of experience, it must provide us with a workable concept of human nature. Yet at present, we are a long way from having a single standard model. The whole field of human psychology is very much in ferment and there are almost as many different theories of human psychological functioning as there are denominations of churches. A recent international conference on psychotherapy had well over a hundred different schools of thought represented, each with its own special descriptive language.
When there is that much confusion, how can we even talk about our inner “mechanisms”? Indeed, there’s a problem already—we are really not machines, after all. What kind of language then can we use?
First, we must come to terms with the fact that the mind and the body are not separate “beings.” For thousands of years, we humans (at least in the West) have been thinking of our Selves as different from our bodies, and perhaps from our souls as well. Yet the more we know about the mind and the body, the more it is apparent that we function as one unit. For example, it is not the case that only the body can have cancer. It is the whole being which has (and reacts to) cancer, or to any other condition of life.
It is also true that the whole body reacts to conditions in the mind-psyche. This is most strikingly seen in a recent report of mind-body interactions in patients with multiple personality. These patients act as if several different people lived in the same body, alternately changing places. One person seems to be in charge at one time, then another takes control.
One such adult patient was very allergic to orange juice, and broke out in hives any time he drank it. Yet, when his “little boy” personality was in charge, he enjoyed orange juice, and did not have any noticeable reaction to it. Another man had a muscle weakness disease that was medically well-documented; yet in another of his personalities, his muscle function immediately became normal.
It is an inescapable fact that mind and body interact. The ideas by which we live can affect both the structure and the function of our bodies. Medical scientists have often tended to be skeptical on that point, but now the scientific question is not ‘Is it true?’, but ‘How does it work?’
Secondly, if we are to have a language of psychological function, we must have a theory of the psyche, that is, a description of how we think the mind-psyche functions. One of the most interesting research frontiers is the study of psychoneurology. How are actions created or mediated in the mind? How does my idea (desire) to move get translated into many well-coordinated nerve impulses which move among many different centers in the brain and throughout the body? And how are ideas and memories stored, and how are they brought to consciousness? Indeed, what is consciousness?
Where do emotions come from? How do I account for my feelings? And where do dreams, fantasies, and slips of the tongue come from? We do not really have complete answers—anatomic or chemical—to such questions.
When we talk of the workings of the mind-psyche, we mostly have to talk in symbolic language. We must say, based on careful observations and careful introspection, that the mind-psyche works “as if” such and such relationships are true. Since we cannot say that such and such a feeling or idea exists in any particular place in the brain (or anywhere else within the body for that matter) or trace an exact series of chemical reactions, we must think in terms of an abstract model.
Various models of the total psyche have evolved, building on concepts developing over centuries. In a brief sketch of key ideas in the developing theory of the unconscious, Carl Jung cites a theory of primordial images traceable to Heraclitus.(3) He considers that Herbert Spencer and William James (4) are among the important contributors to theories of reflexes and instincts, which are of course, unconscious in their function.
Spencer used a concept of a functioning unconscious in developing “unconscious altruism” (5) as an aspect of natural ethics. Yet it was Sigmund Freud (6) who gave us the first scientific model of the psyche, with its concept of a functioning unconscious as the major determinant of behavior. Freud also described the operation of homeostatic mechanisms in the mental life of a person.
Freud’s model of the unconscious is derived from his work in “depth psychology,” using psychoanalysis (a term which he coined.) Freud considered mental life from three points of view: “the dynamic, the economic, and the topographical.” From the dynamic point of view:
… psychoanalysis derives all mental processes (apart from reception of external stimuli) from the interplay of forces, which assist or inhibit one another, combine with one another, enter into compromises with one another, etc. All of these forces are originally in the nature of instincts; that is to say, they have an organic origin. (7)
The economic aspect of psychic functioning:
… supposes that the mental representations of the instincts have a cathexis [an emotional charge] of definite quantities of energy, and that it is the general purpose of the mental apparatus to hinder any damming up of these energies and to keep as low as possible the total amount of the excitations to which it is subject. (8)
Thus the mental system is engaged in a dynamic processing of energies. Indeed, Freud’s description of “definite quantities of energy” seems to flirt (perhaps unconsciously!) with some sort of “quantum theory,” and his “economy” of the psyche gives us a special law of conservation of energy as well!
However, it is his mental topography, or model, of the psyche which has had wide influence on descriptions of mental processes. As Freud describes the model:
According to the most recent psychoanalytic views, the mental apparatus is composed of an id, which is the reservoir of the instinctive impulses; of an ego, which is the most superficial portion of the id and one which is modified by the influence of the external world; and of a superego, which develops out of the id, dominates the ego and represents the inhibitions of instinct characteristic of man. Further, the property of consciousness has a topographical reference; for processes in the id are entirely unconscious, while consciousness is the function of the ego’s outermost layer, which is concerned with the perception of the external world. (9)
Yet despite its utility in opening up the world of the unconscious to clinical access, the model has failed to take into account the full spectrum of normal human functioning. In the article just quoted, Freud acknowledges “hostility” to his work based primarily on “the general disinclination of mankind to concede to the factor of sexuality such importance as is assigned to it by psychoanalysis.”
Further, Freud’s model of the psyche can account for human religious experience only as a neurotic aberration and illusion, (10) which, like Karl Marx’s “religion as opiate,” either denies observed reality or radically redefines the concept of the normal. Both deny the normality of the functioning symbolism of religious experience that exists universally in human culture.
Any model of the psyche must deal with universal human experiences as normal. For example, after observing that noses are a universal human characteristic, it would be untenable to then describe all faces with noses as “deformed.”
Carl Jung broke his association with Freud because of (eventually bitter) disagreements about these issues of sexuality and religious experience. Freud had developed his model from self-analysis, (11) and Jung and Freud, in the trip to the United States in 1909, had participated in mutual analysis. (12) Each had access to the other’s psyche. Jung replied very directly to criticisms from Freud, and to the ideas of Adler, who had also left Freud to found another “school.”
What Freud has to say about sexuality, infantile pleasure, and their conflict with the “principle of reality,” as well as what he says about incest and the like, can be taken as the truest expression of his own psychic make-up. He has given adequate form to what he has noted in himself.
Both schools, to my way of thinking, deserve reproach for over-emphasizing the pathological aspect of life and for interpreting man too exclusively in the light of his defects. A convincing example of this in Freud’s case is his inability to understand religious experience, as is clearly shown in his book The Future of an Illusion. For my part, I prefer to look at man in the light of what in him is healthy and sound … (13)
Jung’s model (14) views the human personality as a systems wholeness, dynamically seeking integration, or individuation, into its undivided fullness. In Jung’s model, these descriptive words themselves renew their original meanings. Individual means undividable; integration means making whole. In Jung’s psychology, psychic energy (libido) is not just sexual in origin. Libido is all psychic energy, which like energy in the external world, occurs in many forms (electricity, heat, light, etc.) and is expressible in many ways.
There are four general aspects in the functioning of the psyche. These are: behavior (expressed in actions and reflexes), emotion (representing affect and feeling tone), cognition (ideas and mental operations), and imaging (dreams, fantasies, hallucinations). All theories must build with these blocks. Any model of the psyche must account for all four types of operations. (15) Because of its special utility in describing human psychology as a functional wholeness, we will present Jung’s model in some detail.
Jung’s model has been diagrammed as a sphere, (16) but a better metaphor would be the system of a living cell, perhaps a luminescent one-celled organism similar to the noctiluca species, whose Latin name means “It glows at night.”
A typical living cell consists of a globule (of various shapes) contained within a membrane. The membrane is a dynamic filter, using various active chemical processes to “pump” ions, glucose and other substances across it. At the cell’s center (approximately) is a nucleus containing its genetic information within a nuclear membrane. The genetic information is important in reproduction (cell division), but it also controls the formation of enzymes which activate the cell’s chemical functions. The cell is filled with cytoplasm which contains many organelles, such as mitochondria, lysosomes, Golgi apparatus, etc. These “little organs” are special structures around and within which are centered various types of reactions.
The metaphorical specimen that we are studying however, has a curious quality. When we first see it under the microscope, we notice that the whole cell has a faint background glow that shows it to be alive, but it is immobile, as if sleeping. Even while we look, and though we have not disturbed it, we see it move. At one end of the cell we see a brightly glowing cap, representing conscious activity. As we watch, the glow constantly changes. Sometimes the luminous zone is diffuse, as during ordinary awareness and nonspecific activities. Sometimes its light focuses at a very intense bright point, as during concentration on a specific task.
The glow of consciousness represents the ego. Ego is the only label that occurs in both Freudian and Jungian models. In general terms, Jung’s concept of ego is similar to Freud’s. The ego is that part which is most directly affected by the senses. It is the locus of rational mental process and the major focus of interest in the currently ascendent cognitive-behavioral psychology. The ego is “mind.”
Back to the specimen under our microscope. The interface between the glowing zone and the remainder is fuzzy and wavy, constantly changing as consciousness reaches into the near zones of the unconscious to retrieve memory. In the waking state, between the part that usually glows and the part that seems not to, there is a zone only occasionally partially involved in the glow of consciousness. This represents Jung’s idea of a personal unconscious, filled with old and recent memories of experience (learning) which have been acquired by the senses, and passed through consciousness, then forgotten or repressed, or passed subliminally, very close to consciousness. In some respects it corresponds to Freud’s idea of id. This zone is a personal and individual area, different in content for each person.
The remainder of the cell looks dim indeed, for its glow, like that of consciousness, is filtered by the cell membrane, which in our model represents Jung’s idea of the persona. The word represents the actor’s mask in ancient Greek theater. The personality that the world sees is an actively maintained mask. There is more to our person than can been seen through our persona, for we (with intention or not) change our mask according to immediate situation, cultural upbringing, professional training, etc..
The persona is commonly described as a complex that mediates between the external world and the ego. (17) That being the case, one would have to obtain a literary license to install it on our metaphorical cell membrane. However, Jung sees it as masking the whole psyche and giving a false appearance of individuality, when in fact, only a very small proportion of the human personality is purely personal.
When we analyze the persona we strip off the mask, and discover that what seemed to be individual is at bottom collective; in other words, that the persona was only a mask of the collective psyche. Fundamentally the persona is nothing real; it is a compromise between individual and society as to what a man should appear to be. (18)
If somehow, we manage to adjust the light to penetrate the membrane and observe the cell without destroying it, we see more features of the remaining unconscious. It is a dense region, but shows many structures and great activity. Most notable is the central nucleus. The central and key concept of Jung’s model of the psyche is the self.
Jung describes the self as being both the whole and the center of the psyche. It is like the force of gravity, in that it acts as if centered in the mass. Thus, in our cell metaphor, the cell is the whole self in both its conscious and unconscious aspects. However, the cell’s nucleus represents the integrative activity of the self. The nucleus has a magnetic quality, seemingly organizing multiple processes.
In our cell-model, there is a particularly strong flow of energy along a certain line, running between the self and the ego. This “ego-self axis”(19) is the line of a constant tug of war, so to speak, between the psyche’s inner-directed integrative forces represented by the self, and the externally-directed rational particularizing forces of the ego.
The “psychoplasm” (Is that carrying our metaphor too far?) also is filled with many organelles called complexes. In Human Systems, we defined the complex in its abnormal aspect, as an autonomous “cell” of energy, around which intense feelings and ideas cluster. There are also certain normal complexes which are the locus of specialized functions, present in all persons. The microanatomy of the complex deserves special consideration.
Inherited as a part of the psyche are certain primordial points around which images and feelings cluster, which Jung called archetypes. Jung indicates that they are not images or feelings themselves, but just as the joining of two molecules determines the way the crystal will develop, so does the archetype determine the way feelings and images cluster. The relationship to the gene has not been demonstrated (and indeed may never be), but perhaps it is appropriate to think of them by analogy as “psychic genes.”
In Jung’s model, the archetypes are the abstract functional units of human nature. We inherit not only our human anatomic characteristics, but our human nature as well. Though the conscious is at some point a “blank tablet” on which experience writes, the unconscious is not. As presented in Chapter Ten, Jung presented archetypes as a vast repository of psychic determinants forming the collective unconscious, which explain the high degree of correspondence in the way humans have reacted in all cultures and in all ages.
Like a mitochondrion (one of the organelles of a cell), the complex has its own micro-structure. The complex is formed when images cluster around a particular archetype. During personal experience, the complex takes on energy in varying degrees according to the associated feeling tone, and thus becomes a center of power that dynamically interacts with the nuclear self and with other complexes. It can emerge into the ego as a burst of energy stimulating mental activity (cognition) or leading to externally directed action (behavior). Thus the complex has a primordial center, and a personal shell. The complex can be positive or negative, creative or destructive, in its effects.
An important complex which is always present is the shadow. The shadow is usually a rather large zone itself, full of primitive emotion. The shadow is the ego’s waste bin, holding rejected images, thoughts, and feelings. Perhaps when we look at our specimen, the shadow appears as just that—a black hole which does not glow at all. It may draw considerable energy away from the ego-self axis, preventing personality integration. It may also project a burst of its energy back into the ego, causing destructive behavior.
The ego may deflect such already rejected energy into a projection, identifying the unacceptable energy as coming from other persons or situations. The classic shadow projection is racial or social bigotry. One betrays oneself when one admits what one hates.
The shadow is a moral problem that challenges the whole ego-personality, for no one can become conscious of the shadow without considerable moral effort. To become conscious of it involves recognizing the dark aspects of the personality as present and real. This act is the essential condition for any kind of self-knowledge, and it therefore, as a rule, meets with considerable resistance. (20)
Not all projections originate from the shadow, however. Many relate to male-female relationships. These emerge from the complicated and distinctive complex in each of us that harbors the ideas and feelings that would normally (consciously) belong to the opposite sex. This contra-sexual complex goes by the Latin names for “soul” and “spirit.” Jung named it the anima (female soul) in the man, and the animus (male spirit) in the woman. Jung writes:
It is easier to gain insight into the shadow than into the anima or animus. With the shadow, we have the advantage of being prepared in some sort by our education, which has always endeavoured to convince people that they are not one-hundred-per-cent pure gold. So everyone immediately understands what is meant by “shadow,” “inferior personality,” etc. And if he has forgotten, his memory can easily be refreshed by a Sunday sermon, his wife, or the tax collector. With the anima and animus, however, things are by no means so simple. (21)
All of us are familiar with traits which are typically labeled masculine or feminine, and generally we recognize that (at least in people we know quite well) we can find a mixture of traits. For example, a particular man who usually is typically aggressive may also show artistic sensitivity and creativeness or even an almost motherly tenderness in some situations. A woman known for her intuitive feminine creativity may also harbor great knowledge, be a keen thinker, and display an athletic or professional aggressiveness.
The Logos principle (see Human Systems) is the logical and reasoning paternal principle emphasizing cognition. The Eros principle is the intuitive nurturing maternal principle which emphasizes the connectiveness of relationships. Each person is endowed with archetypes of both in varying measure (see Self View and Ethics), but those that relate to functioning according to one’s own gender become incorporated into the conscious functioning of the Ego. The non-dominant, contra-sexual characteristics cluster around the unconscious complex (anima/animus).
I do not wish or intend to give these two intuitive concepts too specific a definition. I use Eros and Logos merely as conceptual aids to describe the fact that woman’s consciousness is characterized more by the connective quality of Eros than by the discrimination and cognition associated with Logos. In men, Eros, the function of relationship, is usually less developed than Logos. (22)
Marie-Louise von Franz has especially well interpreted these aspects of the archetypal psyche and their symbolic expression in art and literature. “The anima is a personification of all feminine psychological tendencies in a man’s psyche, such as vague feelings and moods, prophetic hunches, receptiveness to the irrational, capacity for personal love, feeling for nature, and—last but not least—his relation to the unconscious.” (23)
She writes that the woman’s animus is illustrated in the myths and fairy tales which tell of a prince who is redeemed by the love of a girl. “The animus in its most developed form sometimes connects the woman’s mind with the spiritual evolution of her age, and can hereby make her even more receptive than a man to new creative ideas.” (24)
Though in the balanced personality the anima and animus are positive forces, when unrecognized they may be destructive of personal creativity and of relationships with others, and be the source of projections as well.
Throughout history, these archetypes have been communicated in art and literature, and in raised voices in the external relationships of men and women. Collectively, they have been communicated by the armies and armaments of nations. In the normal homeostasis of the psyche, the complexes exchange energy in an effort to maintain a balance.
Their communication within the psyche, however, is exclusively in symbolic language and in feeling energy. In a person who “has it all together,” the ego finds appropriate means of expression in daily life of the energies of the various complexes. Only when consciousness dams up expression do complexes build destructive energy and perhaps become autonomous with neurotic, or worse, results.
Dreams and fantasies can bring these inner workings to the attention of consciousness, though of course their language of symbols tends to be quite obscure. For example, the Self and the Shadow will be represented as same-sex persons, while the anima or animus will be of the sex opposite that of the dreamer. These images provide a therapist with valuable guidance in dealing with personality problems. However, since our purpose is only to illustrate the homeostatic workings of the psyche, the complexities of analysis are quite beyond our scope here. Nevertheless, one can develop valuable insight into the “inner work” of one’s own psyche. One particularly practical guide is that of Jungian analyst Robert A. Johnson. (25) However since there are many books advocating unprofessional and unsound approaches, readers must exercise caution at the bookstore.
One must acknowledge that dream theory is especially very much in ferment. Some hold that dream symbols are merely random, or that they represent the rearrangement of memory from short-term to long-term storage bins (e.g. Winson), (26) or even that they are involved in an information-discarding process of “reverse learning” (e.g. Crick and Mitchison). (27)
Yet recurring dreams that resolve when a particular personal situation is resolved, and the consistency of dream symbols in recorded ancient dreams and that of modern patients, indicate that dreams are not random, and are related to unconscious personality functioning.
In any case, it is clear that the psyche is a complex homeostatic system. Jung’s model provides an integrative descriptive language which is very useful in discussing the wholeness of human personality, even though its mythological references often sound archaic. Jung’s description is nonetheless quite helpful in describing phenomena which cannot be described in the neuromolecular language available to psychoneurology. That there is a difference in the functional and physical levels of description does not invalidate the reality of the psyche, but instead affirms its enormous complexity.
Just as a cell obeys the genetic code of its nucleus, so (in functional terminology) does the psyche seek to obey its archetypes and draw the functioning of the person toward integration in the self. That process can start only when the ego allows the functioning of other psychic elements to be brought into some degree of conscious expression. The saving individuation process is a matter of the ego’s allowing the self to bring the person into the fullness of inborn potential and realization.
As individuation proceeds, the glow of the metaphorical noctiluca’s cap spreads throughout the cell, producing a glowing organism that in concert with others can literally light up a dark sea. That is the potential of humanity’s collective unconscious, which we next consider.
Copyright 2000 by Donivan Bessinger. All rights reserved.
Also see: [ Jung’s model of the psyche ]
Next Chapter: The Collective Unconscious
More by Donivan Bessinger, MD
References:
(1) “WE ARE SUCH STUFF”—William Shakespeare. The Tempest. Act IV. Scene 1.
(2) “TOTAL PSYCHE”—The word psyche is sometimes used to define that part of a human being which is not body. For that concept, I will generally use such terms as “total psyche” or “total self”. However, psyche is Greek for soul. Here I use “psyche” to refer to the unconscious, and “mind” (Greek nous) to refer to the realm of conscious mental activity.
(3) PRIMORDIAL IMAGES TRACEABLE TO HERACLITUS—C. G. Jung. “Structure and Dynamics of the Psyche” (1927). CW 8. PJ 57.
(4) HERBERT SPENCER AND WILLIAM JAMES—ibid. PJ 50.
(5) “UNCONSCIOUS ALTRUISM”—Herbert Spencer. The Data of Ethics (1879). Chap 12.
(6) SIGMUND FREUD WHO GAVE US—James Grier Miller. “Unconsciousness.” Encyclopedia Britannica, 1965, 22: 681.
(7) “PSYCHOANALYSIS DERIVES ALL”—Sigmund Freud. “Psychoanalysis” (1926). Encyclopedia Britannica, 1965, 18: 671.
(8) “SUPPOSES THAT THE MENTAL REPRESENTATIONS”—ibid.
(9) “ACCORDING TO THE MOST RECENT PSYCHOANALYTIC”—ibid.
(10) NEUROTIC ABERRATION AND ILLUSION—see Sigmund Freud: Future of an Illusion (1927, trans. 1961).
(11) FREUD … SELF-ANALYSIS—Heinz Hartmann. “Sigmund Freud.” Encyclopedia Britannica, 1965, 9: 928.
(12) PARTICIPATED IN MUTUAL ANALYSIS—C. G. Jung. MDR 158.
(13) “WHAT FREUD HAS TO SAY ABOUT SEXUALITY”—CGJ. “Freud and Jung: Contrasts” (1929). CW 4. MMSS 116-117.—For additional commentary, see Victor White. “Freud, Jung and God” in God and the Unconscious (1952). Dallas: Spring Publications, 1982.
(14) JUNG’S MODEL VIEWS THE HUMAN—The general description of Jung’s model is based on:
“The Structure and Dynamics of the Psyche” (1927). CW 8: 263 ff. PJ 47 ff.
“Two Essays on Analytical Psychology” (1928). CW 7: 202 ff. PJ 70 f.
“Aion: Researches into the Phenomenology of the Self” (1951). CW 9ii: 1-42. PJ 139 ff.
(15) ANY MODEL OF THE PSYCHE MUST ACCOUNT—C. J. Groesbeck. “Carl Jung” in Comprehensive Textbook of Psychiatry, Fourth Edition, H. I. Kaplan and B. J. Sadock, editors. Baltimore: Williams & Wilkins, page 433.
(16) MODEL DIAGRAMMED AS A SPHERE—Maria-Louise von Franz. “The process of individuation” in CGJ. MHS 161 (fig).
(17) PERSONA COMMONLY DESCRIBED AS A COMPLEX—Groesbeck. op. cit.
(18) “WHEN WE ANALYZE THE PERSONA”—CGJ. CW 7. PJ 105.
(19) EGO-SELF AXIS—For implications of the ego-self axis and correlations between theology and psychology, see Fritz Kunkel: Selected Writings. Edited, with commentary, by John Sanford. New York: Paulist Press, 1984.
(20) “THE SHADOW IS A MORAL PROBLEM”—CGJ. CW 9ii. PJ 145.
(21) “IT IS EASIER TO GAIN INSIGHT”—CGJ. CW 9ii. PJ 155.
(22) “I DO NOT WISH OR INTEND”—CGJ. CW 9ii. PJ 152.
(23) “THE ANIMA IS A PERSONIFICATION”—von Franz. op. cit. p 177.
(24) “THE ANIMUS IN ITS MOST”—ibid. p 193.
(25) ONE PARTICULARLY PRACTICAL GUIDE—Robert A. Johnson. Inner Work: Using Dreams and Active Imagination for Personal Growth. San Francisco: Harper & Row, 1986.
(26) REARRANGEMENT OF MEMORY—Jonathan Winson. Brain & Psyche: The Biology of the Unconscious. New York: Vintage/Random House, 1986.
(27) “REVERSE LEARNING”—F. H. C. Crick and Graeme Mitchison. “The function of dream sleep.” Nature 304, 5922 (1983): 111-114.