sleep experience

Dream, a hallucinatory experience that occurs during sleep.

Dreaming, a common and distinctive phenomenon of sleep, has throughout human history given rise to myriad beliefs, fears, and conjectures, both imaginative and experimental, regarding its mysterious nature. While any effort toward classification must be subject to inadequacies, beliefs about dreams nonetheless fall into various classifications depending upon whether dreams are held to be reflections of reality, sources of divination, curative experiences, or evidence of unconscious activity.

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Freud, Sigmund
Sigmund Freud: The interpretation of dreams

In what many commentators consider his master work, Die Traumdeutung (published in 1899, but given the date of the dawning century to emphasize its epochal character; The Interpretation of Dreams), he presented his findings. Interspersing evidence from his own dreams with evidence from those…

Efforts to study dreaming

Dream reports

The manner in which people dream obviously defies direct observation. It has been said that each dream “is a personal document, a letter to oneself” and must be inferred from the observable behaviour of people. Furthermore, observational methods and purposes clearly affect conclusions to be drawn about the inferred dreams. Reports of dreams collected from people after morning awakenings at home tend to exhibit more content of an overt sexual and emotional nature than do those from laboratory subjects. Such experiences as dreaming in colour seldom are spontaneously mentioned but often emerge under careful questioning. Reports of morning dreams are typically richer and more complex than those collected early at night. Immediate recall differs from what is reported after longer periods of wakefulness. In spite of the unique qualities of each person’s dreams, there have been substantial efforts to describe the general characteristics of what people say they have dreamed.

Estimates by individuals of the length of their dreams can vary widely (and by inference, the actual length of the dreams varies widely as well). Spontaneously described dreams among laboratory subjects typically result in short reports; although some may exceed 1,000 words in length, about 90 percent of these reports are fewer than 150 words long. With additional probing, about a third of such reports are longer than 300 words.

Some investigators have been surprised by repeated findings that suggest dreams may be less fantastic or bizarre than generally supposed. One investigator stated that visual dreams are typically faithful to reality—that is, they are representational. To borrow terms from modern art, dreams are rarely described as abstract or surrealist. Except for those that are very short, dreams are reported to take place in ordinary physical settings, with about half of them seeming quite familiar to the dreamer. Only rarely is the setting said to be exotic or peculiar.

Apparently dreams are quite egocentric, with the dreamer perceiving himself as a participant, though the presence of others is typically recalled. Seldom does the person remember an empty, unpopulated dreamworld, and individuals seem to dream roughly two-thirds of the time about people they know. Usually these people are close acquaintances, with family members mentioned in about 20 percent of dream reports. Recollections of notables or weird representations of people are generally rare.

In cases of so-called lucid dreaming, subjects report having been aware that they were dreaming as the dream was taking place. Most lucid dreamers also report having been able to direct or manipulate the dream’s content to some extent. The nature of lucid dreaming and even the coherence of the notion have been disputed, however. Some researchers have suggested that it is a unique state of consciousness that combines elements of wakefulness and ordinary (nonlucid) dreaming.

The typical dream report is of visual imagery; indeed, in the absence of such imagery, the person may describe the phenomenon as thinking rather than “dreaming” while asleep. Rare statements about dreams dominated by auditory experience tend to be made with claims of actually having been awake. It is unusual, however, to hear of dreams without some auditory characteristics. Emotionally bland dreams are common. When dreams do contain emotional overtones, fear and anxiety are most commonly mentioned, followed by anger; pleasant feelings are most often those of friendliness. Reports of overtly erotic dreams, particularly among subjects studied in laboratory settings, are infrequent.

Many individuals report having recurring dreams, or dreams that are repeated over a short or a long period with at most minor variations. Some recurring dreams display common themes, such as being able to fly, being chased, being naked in public, or being late for an exam. Although there is no consensus among experts regarding the causes or interpretation of recurring dreams, many researchers believe that negative recurring dreams may be indicative of the presence of an unresolved conflict in the individual.

Despite their generally representational nature, dreams seem somehow odd or strange. Perhaps this is related to discontinuities in time and purpose. One may suddenly find oneself in a familiar auditorium viewing a fencing match rather than hearing a lecture and abruptly in the “next scene” walking beside a swimming pool. These sudden transitions contribute a feeling of strangeness, which is enhanced by the dreamer’s inability to recall the bulk of his dreams clearly, giving them a dim, mysterious quality.

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Daumier, Honoré: caricature
hallucination: Dreams

The first stages of sleep appear to be dream-free. During this phase, measurements taken by an electroencephalograph (EEG) will record the sleeper producing large, slow brain waves. Sensory stimuli from without (such as noise or cold) or stimuli from within the body (such as…

Physiological dream research

A new era of dream research began in 1953 with the discovery that rapid eye movements during sleep seem often to signal that a person is dreaming. Researchers at the University of Chicago’s Sleep Research Laboratory observed that, about an hour after laboratory subjects fell asleep, they were apt to experience a burst of rapid eye movement (REM) under their closed lids, accompanied by a change in brain waves detected (by electroencephalography) as an electrical pattern resembling that of an alert waking person. When subjects were awakened during REM, they reported vivid dreams 20 out of 27 times; when roused during non-REM (NREM) sleep, they recalled dreams in only 4 of 23 instances. Subsequent systematic study confirmed this relationship between REM, activated brain waves (increased brain activity), and dream recall. Several thousand experimental studies utilizing these observable indexes of dreaming have since been conducted.

A major finding is that the usual report of a vivid, visual dream is primarily associated with REM and increased brain activity. On being aroused while exhibiting these signs, people recall dreams with visual imagery about 80 percent of the time. When awakened in the absence of them, however, people still report some kind of dream activity, though only about 30 to 50 percent of the time. In such cases they are apt to remember their sleep experiences as being relatively “thoughtlike” and realistic and as resembling the experiences of wakefulness.

D-state (desynchronized or dreaming) sleep has been reported for all mammals studied. It has been observed, for example, among monkeys, dogs, cats, rats, elephants, shrews, and opossums; these signs also have been reported in some birds and reptiles.

Surgical destruction of selected brain structures among laboratory animals has clearly demonstrated that the D-state depends on an area within the brain stem known as the pontine tegmentum (see pons). Evidence indicates that D-state sleep is associated with a mechanism involving a bodily chemical called norepinephrine; other stages of sleep seem to involve another chemical (serotonin) in the brain. Among other physiological changes found to be related to D-state sleep are increased variability in heart rate, increased activity in the respiratory system and sexual organs, and increases in blood pressure, accompanied by a near-complete relaxation of the skeletal muscles.

When people are chronically deprived of the opportunity to manifest D-state activity (by awakening them whenever there is EEG evidence of dreaming), it appears increasingly difficult to prevent them from dreaming. On recovery nights (after such deprivation), when the subject can sleep without interruption, there is a substantial increase in the number of reports of dreaming. This rebound effect continues in some degree on subsequent recovery nights, depending on how badly the person has been deprived.

During D-states in the last 6 1/2 to 7 1/2 hours of sleep, people are likely to wake by themselves about 40 percent of the time. This figure is about the same as that for dream recall, with subjects saying they had a dream the previous night about 35 percent of the time (roughly once every three or four nights). Evidence concerning the amount and kind of dreaming also depends on how rapidly one is roused and on the intensity of his effort to recall. Some people recall dreams more often than the average, while others rarely report them. These differences have nothing to do with the amount of D-state sleep. Evidence suggests instead that nonrecall reflects a tendency on the part of the individual to repress or to deny personal experiences.

The psychoanalytic literature is rich with reports indicating that what one dreams about reflects one’s needs as well as one’s immediate and remote past experience. Nevertheless, when someone in D-state sleep is stimulated (for example, by spoken words or by drops of water on the skin), the chances that the dreamer will report having dreamed about the stimulus (or anything like it) are quite low. Studies in which people have watched vivid movies before falling asleep indicate some possibility of influence on dreams, but such studies also emphasize the limitation of this influence. Highly suggestible people seem likely to dream as they are told to do while under hypnosis, but the influence of direct suggestion during ordinary wakefulness seems quite limited.

Variations within the usual quantity of D-state sleep (about 18 to 30 percent of D-state sleep in an average period of sleep) apparently are unrelated to differences in the amount or content of dreaming. The amount of D-state sleep seems independent of wide variations in the daily activities or personality characteristics of different people; groups of scientists, athletes, and artists, for example, cannot be distinguished from one another in terms of D-state activity. Such disorders as schizophrenia and intellectual disability appear to have no clearly discernible effect on the amount of time a person will spend in such REM-activated EEG sleep.

Dreamlike activities

Related states of awareness may be distinguished from the dream experiences typically reported; these include dreamlike states experienced as a person falls asleep and as he awakens, respectively called hypnagogic and hypnopompic reveries. During sleep itself there are nightmares, observable signs of sexual activity, and sleepwalking. Even people who ostensibly are awake may show evidence of such related phenomena as hallucinating, trance behaviour, and reactions to drugs.

Rapid eye movement is not characteristic of sleep onset; nevertheless, as people drift (as inferred from EEG activity) from wakefulness through drowsiness into sleep, they report dreamlike hypnagogic experiences about 90 percent of the time on being awakened. Most of these experiences (about 80 percent) are said to be visual. A person who awakens from drowsiness or at the onset of sleep will recall experiences that may be classified as dreams about 75 percent of the time. These “dreamlets” seem to differ from dream-associated REM sleep in being less emotional (neither pleasant nor unpleasant), more transient, and less elaborate. Such hypnagogic experiences seem to combine abstract thinking with recall of recent events (known in psychoanalytical terms as day residues). This is quite typical of falling asleep. Systematic studies remain to be made of the hypnopompic reveries commonly reported during mornings before full arousal, but it seems likely that they include recollections of the night’s dreams or represent one’s drifting back into transient REM sleep.

Extreme behavioral manifestations during sleep—night terrors, nightmares, sleepwalking, and enuresis (bedwetting)—have been found to be generally unrelated to ordinary dreaming. Night terrors are characterized by abrupt awakening, sometimes with a scream; a sleeping child may sit up in bed, apparently terror-stricken, with wide-open eyes and often with frozen posturing that may last several minutes. Afterward there typically is no recollection of dreamlike experience. Night terrors are observed in about 2 or 3 percent of children, and roughly half of the attacks occur between the ages of 4 and 7; about 10 percent of them are seen among youngsters as old as 12 to 14 years. Nightmares typically seem to be followed by awakening with feelings of suffocation and helplessness and expressions of fearful or threatening thoughts. Evidence of nightmares is observed for 5 to 10 percent of children, primarily about 8 to 10 years of age. Studies have suggested that signs of spontaneously generated night terrors and nightmares may be related to abrupt awakening from deep sleep that experimentally appears dreamless. This suggests that the vividly reported fears may well be produced by emotional disturbances that first occur on awakening.

Sleepwalking, observed in about 1 percent of children, predominantly appears between ages 11 and 14. Apparently sleeping individuals rise and walk from their beds, eyes open, usually avoiding obstacles, and later express no recollection of the episode. Studies of EEG data indicate that sleepwalking occurs only in deep sleep when dreams seem essentially absent; the behaviour remains to be reported for REM sleep. Enuresis occurs in about one-fourth of children over age four. These episodes seem not to be associated with REM as much as they do with deep sleep in the absence of D-state signs.

Nocturnal emission of sperm remains to be described in terms of any distinguishing EEG pattern; such events are extremely rare among sleeping laboratory subjects. Among a large sample of males who were interviewed about their sexual behaviour, about 85 percent reported having experienced emissions at some time in their lives, with typical frequency during the teens and 20s being about once a month. Of the females interviewed, 37 percent reported erotic dreams, sometimes with orgasm, averaging about three to four times a year. Most often, however, openly sexual dreams are said not to be accompanied by orgasm in either sex. Males usually could recall no dreams associated with emission, although most implicated erotic dreaming.

Dreamlike experiences induced by trances, delirium, or drug hallucination seem to stem from impairments to the central nervous system that lower the efficiency of processing sensory stimuli from the external environment. In such cases, apparently, one’s physiological activities begin to escape environmental constraint to the point that internalized, uncritical thinking and perceiving prevail.

Diverse views on the nature of dreams

Dreams as reflecting reality

Philosophers have long noted the similarities between reality and dreaming and the logical difficulties of distinguishing in principle between the two. The English philosopher Bertrand Russell wrote, “It is obviously possible that what we call waking life may be only an unusual and persistent nightmare,” and he further stated that “I do not believe that I am now dreaming but I cannot prove I am not.” Philosophers have generally tried to resolve such questions by saying that so-called waking experience, unlike dreaming, seems vivid and coherent. As the French philosopher René Descartes put it, “Memory can never connect our dreams one with the other or with the whole course of our lives as it unites events which happen to us while we are awake.” Similarly, Russell stated, “Certain uniformities are observed in waking life, while dreams seem quite erratic.”

Dreams as a source of divination

There is an ancient belief that dreams predict the future; the Chester Beatty Papyrus is a record of Egyptian dream interpretations dating from the 12th dynasty (1991–1786 bce). In Homer’s Iliad, Agamemnon is visited in a dream by a messenger of the god Zeus to prescribe his future actions. From India, a document called the Atharvaveda, dated to the 5th century bce, contains a chapter on dream omens. A Babylonian dream guide was discovered in the ruins of the city of Nineveh among tablets from the library of the emperor Ashurbanipal (668–627 bce). The Old Testament is rife with accounts of prophetic dreams, those of the pharaohs and of Joseph and Jacob being particularly striking. Among pre-Islamic peoples, dream divination so heavily influenced daily life that the practice was formally forbidden by Muhammad (570–632), the founder of Islam.

Ancient and religious literatures express the most confidence about so-called message dreams. Characteristically, a god or some other respected figure appears to the dreamer (typically a king, a hero, or a priest) in time of crisis and states a message. Such reports are found on ancient Sumerian and Egyptian monuments; frequent examples appear in the Bible. Joseph Smith (1805–44), the founder of Mormonism, said that an angel directed him to the location of buried golden tablets that described American Indians as descendants of the tribes of Israel.

Not all dream prophecies are so readily accepted. In Homer’s Odyssey, for example, dreams are classed as false (“passing through the Gate of Ivory”) and as true (“passing the Gate of Horn”). Furthermore, prophetic meaning may be attributed to dream symbolism. In the Bible, Joseph interpreted sheaves of grain and the Moon and stars as symbols of himself and his brethren. In general, the social status of dream interpreters varies; in cultures for which dreams loom important, their interpretation has often been an occupation of priests, elders, or medicine men.

An ancient book of dream interpretation was compiled by the 3rd-century soothsayer Artemidorus Daldianus in the Oneirocritica (from the Greek oneiros, “a dream”). Contemporary studies cover dreams and dreaming from a number of perspectives, such as physiology, neuroscience, psychology, and interpretation.

Dreams as curative

So-called prophetic dreams in the Middle Eastern cultures of antiquity often were combined with other means of prophecy (such as animal sacrifice) and with efforts to heal the sick. In classical Greece, dreams became directly associated with healing. In a practice known as temple sleep, ailing people came to dream in oracular temples such as those of the Greek god of medicine, Asclepius; there, they performed rites or sacrifices in efforts to dream appropriately, and they then slept in wait of the appearance of the god (or his emissary, such as a priest), who would deliver a cure. Many stone monuments placed at the entrances of the temples survive to record dream cures. A practice similar to temple dreaming, known as dream incubation, is recorded in Babylon and Egypt.

Dreams as extensions of the waking state

Even in early human history, dreams were interpreted as reflections of waking experiences and of emotional needs. In his work Parva naturalia (On the Senses and Their Objects), the Greek philosopher Aristotle (384–322 bce), despite the practice of divination and incubation among his contemporaries, attributed dreams to sensory impressions from “external objects…pauses within the body…eddies…of sensory movement often remaining like they were when they first started, but often too broken into other forms by collision with obstacles.” Anticipating work by the Austrian psychoanalyst Sigmund Freud (1856–1939), Aristotle wrote that sensory function is reduced in sleep, thereby favouring the susceptibility of dreams to emotional subjective distortions.

In spite of Aristotle’s unusually modern views and even after a devastating attack by the Roman statesman Marcus Tullius Cicero (106–43 bce) in (De divinatione; “On Divination”), the view that dreams have supernatural attributes was not again challenged on a serious level until the 1850s, with the classic work of the French scientist Alfred Maury, who studied thousands of reported recollections of dreams. Maury concluded that dreams arose from external stimuli, instantaneously accompanying such impressions as they acted upon the sleeping person. Citing a personal example, he wrote that part of his bed once fell on the back of his neck and woke him, leaving the memory of dreaming that he had been brought before a French revolutionary tribunal, questioned, condemned, led to the scaffold, and bound by the executioner, and that the guillotine blade had fallen.

The Scottish writer Robert Louis Stevenson said that much of his work was developed by “little people” in his dreams, and he specifically cited the Strange Case of Dr. Jekyll and Mr. Hyde (1886) in this context. The German chemist August Kekule von Stradonitz attributed his interpretation of the ring structure of the benzene molecule to his dream of a snake with its tail in its mouth. Otto Loewi, a German-born physician and pharmacologist, attributed to a dream his inspiration for an experiment with a frog’s nerve that helped him win the Nobel Prize for Physiology or Medicine in 1936. In all of these cases, the dreamers reported having thought about the same topics over considerable periods while they were awake.

Psychoanalytic interpretations

Among Freud’s earliest writings was The Interpretation of Dreams (1899), in which he insisted that dreams are “the royal road to knowledge of activities of the unconscious mind”—in other words, that dreams offer a means of understanding waking experience. He held this theory throughout his career, even mentioning it in his last published statement on dreams, printed about one year before his death. He also offered a theoretical explanation for the bizarre nature of dreams, invented a system for their interpretation, and elaborated on their curative potential.

Freud theorized that thinking during sleep tends to be primitive and regressive. Repressed wishes, particularly those associated with sex and hostility, were said to be released in dreams when the inhibitory demands of wakefulness diminished. The content of the dream was said to derive from such stimuli as urinary pressure in the bladder, traces of experiences from the previous day (day residues), and associated infantile memories. The specific dream details were called their manifest content; the presumably repressed wishes being expressed were called the latent content. Freud suggested that the dreamer kept himself from waking and avoided unpleasant awareness of repressed wishes by disguising them as bizarre manifest content in an effort called dreamwork. He held that impulses one fails to satisfy when awake are expressed in dreams as sensory images and scenes. In dreaming, Freud believed:

All of the linguistic instruments…of subtle thought are dropped…and abstract terms are taken back to the concrete.… The copious employment of symbols…for representing certain objects and processes is in harmony (with) the regression of the mental apparatus and the demands of censorship.

Freud submitted that one aspect of manifest content could come to represent a number of latent elements (and vice versa) through a process called condensation. Further displacement of emotional attitudes toward one object or person theoretically could be displaced in dreaming to another object or person or not appear in the dream at all. Freud further observed a process called secondary elaboration, which occurs when people wake and try to remember dreams. They may recall inaccurately in a process of elaboration and rationalization and provide “the dream, a smooth facade, (or by omission) display rents and cracks.” This waking activity he called “secondary revision.”

In seeking the latent meaning of a dream, Freud advised the individual to associate freely about it. Dreams thus represented another source of free association in psychoanalysis. From listening to the associations, the analyst was supposed to determine what the dream represented, in part through an understanding of the personal needs of the dreamer. Using this information, the analyst could help the patient overcome inhibitions that were identified through dreamwork. (See Sigmund Freud: The interpretation of dreams

Unlike Freud, Carl Jung (1875–1961) did not view dreams as complementary to waking mental life with respect to specific instinctual impulses. Jung believed that dreams were instead compensatory, that they balanced whatever elements of character were underrepresented in the way people live their lives. Dreaming, to Jung, represented a continuous 24-hour flow of mental activity that would surface in sleep under conducive conditions but could also affect waking life when one’s behaviour denied important elements of one’s true personality.

In Jung’s view, then, dreams are constructed not to conceal or disguise forbidden wishes but to bring the underattended areas to attention. This function is carried out unconsciously in sleep when people are living emotionally well-balanced lives. If this is not the case, there may be first bad moods and then symptoms in waking. Then and only then do dreams need to be interpreted. This is best done not with a single dream and multiple free associations but with a series of dreams so that the repetitive elements become apparent.


Since antiquity, dreams have been viewed as a source of divination, as a form of reality, as a curative force, and as an extension or adjunct of the waking state. Contemporary research focuses on efforts to discover and describe unique, complex biochemical and neurophysiological bases of dreaming. Psychoanalytic theorists emphasize the individual meaningfulness of dreams and their relation to personal hopes and fears. Other perspectives assert that dreams convey supernatural meaning, and some regard dreaming as nothing more than the normal activity of the nervous system. Such variety reflects the lack of any single, all-encompassing theory about the nature or purpose of dreams.

Wilse B. Webb Rosalind D. Cartwright The Editors of Encyclopaedia Britannica

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