Dream

For other uses, see Dream (disambiguation).

"The Knight's Dream", 1655, by Antonio de Pereda

Dreams are successions of images, ideas, emotions, and sensations that occur involuntarily in the mind during certain stages of sleep.^[1] The content and purpose of dreams are not definitively understood, though they have been a topic of scientific speculation, philosophical intrigue and religious interest throughout recorded history. The scientific study of dreams is called oneirology. Science has proven to an extent that all mammals dream. The scientific approach to dreams has been conducted through the discovery of REM sleep.

Dreams mainly occur in the rapid-eye movement (REM) stage of sleep—when brain activity is high and resembles that of being awake. REM sleep is revealed by continuous movements of the eyes during sleep. At times, dreams may occur during other stages of sleep. However, these dreams tend to be much less vivid or memorable. Dreams can last for a few seconds, or as long as twenty minutes. A person is more likely to remember the dream if he or she is awakened during the REM phase.

Dreams are a connection to the human subconscious. They can range from normal and ordinary to the overly surreal and bizarre. Dreams can at times make a creative thought occur to the person or give a sense of inspiration. Dream imagery is often absurd and unrealistic, and the events in dreams are generally outside the control of the dreamer, with the exception of lucid dreaming. Dreamers are usually not self-aware in their dreams; thus the dreams seem as reality. Dreams can have varying natures, such as frightening, exciting, magical, melancholic, adventurous, or sexual.^[2]

The opinions about the meaning of dreams has varied and shifted through time and culture. Dream interpretations date back to 5000-4000 BC, where they were documented on clay tablets. The earliest recorded dreams were acquired from materials dating back approximately 5000 years, in Mesopotamia.^[3] In some of the earliest societies, the dream world was regarded as an extension of reality. In the Greek and Roman periods, dreams were seen through a religious lens. The people believed that they were direct messages from the gods or from the dead. The people of that time relied on their dreams for solutions on what to do, or what course of action to take. They also believed dreams forewarned and predicted the future. Throughout history, people have sought meaning in dreams or divination through dreams.^[4] Dreams have also been described physiologically as a response to neural processes during sleep; psychologically as reflections of the subconscious; and spiritually as messages from the Soul, from a god or from the deceased, or as predictions of the future. Some cultures practice dream incubation with the intention of cultivating dreams that are prophetic or contain messages from the divine. Some of these interpretations remain today embedded in the minds of individuals. The randomness or hidden meaning of dreams remains disputable.

The most prolific dream theories and interpretations were developed by Sigmund Freud, the Austrian neurologist who developed the discipline of psychoanalysis. Freud explained dreams were manifestations of our deepest desires and anxieties. During sleep, dreams would manifest childhood repressed memories and obsessions. In The Interpretation of Dreams, Freud developed a psychological technique to interpret dreams and devised a series of guidelines to understand the symbols and motifs that appear in our dreams.

The cultural meaning of dreaming

Ancient history

The Sumerians in Mesopotamia left evidence of dreams dating back to 3100 BC. According to these early recorded stories, gods and kings, like the 7th century BC scholar-king Assurbanipal, paid close attention to dreams. In his archive of clay tablets, some amounts of the story of the legendary king Gilgamesh were found. In this epic poem—one of the earliest known stories—Gilgamesh reported his recurring dreams to his goddess-mother Ninsun, who made the first known recorded dream interpretation.^[5]

Gilgamesh's dreams were thought of as a prophecy, where he used to control the actions in the waking world. These philosophies recorded in the Gilgamesh epic gave a valuable source of information about ancient dream beliefs. The Mesopotamians believed that the soul, or some part of it, moves out from the body of the sleeping person and actually visits the places and persons the dreamer sees in his sleep. Sometimes the god of dreams is said to carry the dreamer.^[6]

Babylonians divided dreams into "good," which were sent by the gods, and "bad," sent by demons. In Assyria, people believed that their dreams were omens. One of the earliest recorded dreams was found written on a clay tablet in Nineveh. This dream dated back to the reign of King Ashurbanipal (669-626 BC). The tablet concluded that if a man flies repeatedly in his dreams, then all that he owns will be lost. Assyrians believed that dreams involving sexual content or adultery were thought of as diseases caused by evil demons rising from the under worlds to attack people.^[7]

In ancient Egypt, people believed gods showed themselves in dreams. They believed that dreams were caused by real things that were beyond interpretation or control by the conscious mind. As back as 2000 BC, the Egyptians wrote down their dreams on papyrus. People with vivid and significant dreams were thought blessed and were considered special. Ancient Egyptians distinguished three main types of dreams: those in which the gods demanded some devotional act, those that contained warnings or revelations, and those that came about through ritual.^[8]

Ancient Egyptians believed that dreams were like oracles, bringing messages from the gods. They thought that the best way to receive divine revelation was through dreaming and thus they would induce (or "incubate") dreams. Egyptians would travel to a sanctuary or shrine, such as the famous temple at Memphis, Egypt, to lie down on special "dream beds" in hope of receiving advice, comfort, or healing from the gods.^[9]

Religious history

Jacob's dream of a ladder of angels, c. 1690, by Michael Willmann

The ancient Hebrews connected their dreams heavily with their religion, though the Hebrews were monotheistic and believed that dreams were the voice of one god alone. Hebrews also differentiated between good dreams (from God) and bad dreams (from evil spirits). The Hebrews, like many other ancient cultures, incubated dreams in order to receive divine revelation. For example, the Hebrew prophet Samuel, would "lie down and sleep in the temple at Shiloh before the Ark and receive the word of the Lord."

Christians mostly shared their beliefs with the Hebrews and thought that dreams were of the supernatural element because the Old Testament had frequent stories of dreams with divine inspiration. The most famous of these dream stories was Jacob's dream that stretched from Earth to Heaven. Many Christian men preached that God talked to his people through their dreams.

Classical history

Dreaming of the Tiger Spring (虎跑夢泉)

In Chinese history, people wrote of two vital aspects of the soul of which one is freed from the body during slumber to journey a dream realm, while the other remained in the body. Although, this belief and dream interpretation was questioned since early time, such as by the philosopher Wang Chong (27-97).^[10] The Indian text Upanishads, written between 900 and 500 BC, emphasize two meanings on dreams. The first says that dreams are merely expressions of inner desires. The second is the belief of the soul leaving the body and being guided until awakened.

The Greeks shared their beliefs with the Egyptians on how to interpret good and bad dreams, and the idea of incubating dreams. Greek legend states that the god Hypnos made the people sleep by touching them with his magic wand or by fanning them with his wings. Morpheus also sent warnings and prophecies to those who slept at shrines and temples. The earliest Greek beliefs of dreams was that their gods physically visited the dreamers, where they entered through a keyhole, and exiting the same way after the divine message was given.

Dreams also helped their practice of medicine, sending sick people to particular temples. Sick Greeks visited these temples to perform various religious rites, sleep, and hope to have a dream that assured a return to good health. They slept for many days, sometimes trying for weeks or months until they had the "right" dream. Antiphon wrote the first known Greek book on dreams in the 5th century BC. In that century, other cultures influenced Greeks to developed the belief that souls left the sleeping body.^[11]

Hippocrates (469-399 BC) had a simple dream theory: during the day, the soul receives images; during the night, it produces images. Greek philosopher, Aristotle (384-322 BC) believed dreams caused physiological activity. He thought dreams could analyse illness and predict diseases. In the Hellenistic times, the main interest in dreams centred around their ability to heal. Greeks of that period believed that dreams offered vital clues that could help healers diagnose the dreamer. Galen, a Greek physician born in 129 AD, said that people should carefully observe dreams for clues to healing. He was so convinced of dream messages that he performed operations on the basis of dream interpretations.

Post-Classic/Medieval history

Some Indigenous American tribes and Mexican civilizations believe that dreams are a way of visiting and having contact with their ancestors.^[12]

The Middle Ages brought a harsh interpretation of dreams. They were seen as evil, and the images as temptations from the devil. Many believed that during sleep, the devil could fill the human mind with corrupting and harmful thoughts. Martin Luther, founder of Protestantism, believed dreams were the work of the Devil. However, Catholics such as St. Augustine and St. Jerome claimed that the direction of their life were heavily influenced by their dreams.

Freudian view of dreams

Nun's dream by Karl Briullov

In the early 19th century, many thought dreams had no meaning at all, that they were just caused by anxiety, family issues, or even by upset stomachs. Later in the 19th century, psychotherapist Sigmund Freud argued for the importance of dreams and their significance for psychology. He created a great vogue for the study of dreams.^[13] In 1899 he published Die Traumdeutung. In English it was called The Interpretation of Dreams.

Freud theorized that wish fulfillment was behind most dreams. His interpreted dreams as a reflection of the dreamer's deepest desires, going back to their childhood. To Freud, dreams were images that held important meanings. Freud's theory distinguishes two layers of dream content: manifest and latent. Manifest (superficial) content had no significant meaning but was a mask for underlying issues of the dream. Latent content was those underlying issues; it expressed unconscious wishes or fantasies. Freud believed most dreams were of a sexual nature. From Freud's time forward, many no longer considered dreams divine or demonic, but a valid mode for collecting information on an unconscious level. Freud called dreams the "royal road to the unconscious."^[14] In his earlier writings, Freud viewed the vast majority of dreams as sexual in nature, but he later shied away from this categorical position, and in Beyond the Pleasure Principle, considered trauma and aggression as other possible causes of dreams. He also considered supernatural origins in Dreams and Occultism, a lecture published in New Introductory Lectures on Psychoanalysis ^[15] Freud's, and by extension, other psychoanalytic views of dreams, have been attacked by, among others, Hans Eysenck, who wrote a book discrediting them called Decline and Fall of the Freudian Empire.

Jungian and other anti-Freudian dissident view of dreams

Carl Jung, a student of Freud who later turned against him, also believed that dreams related to the dreamer's wishes, which enables them to realize things they unconsciously desire, and that the dreams help them to fulfill their wishes. Jung believed dreams were messages to the dreamer and that dreamers should pay attention for their own good. Carl Jung came to believe that dream contents present the dreamer with revelations that uncover and help to resolve emotional issues, problems, religious issues and fears.^[16]

Jung believed that recurring dreams are a proof that the dreamer is neglecting an issue, thus it shows up repeatedly in dreams to demand attention. He believed that many of the symbols or images from these dreams return with each dream. Jung also said that dreams are not only important to the dreamer's life, but that they are all parts of "one great web of psychological factors." Such things as events, movies and people seen the previous day also play a role in dreaming. These memories leave impressions for the unconscious to deal with when the ego is at rest. The unconscious re-enacts these glimpses of the past, in the form of a dream. Jung called this a day residue.^[17]

Another student of Freud's who turned against him, Alfred Adler, believed dreams simply represented aggression. Freudian psychotherapy and psychoanalysis today have fallen out of fashion. Most modern psychologists regard Freud as being of primarily historical interest.

The Neurobiology of dreaming

Main article: REM sleep

EEG showing brainwaves during REM sleep

There is not a universally accepted biological definition of dreaming. In 1952, Eugene Aserinsky identified and defined rapid eye movement (REM) sleep while working in the surgery of his PhD adviser. He noticed that the sleepers' eyes fluttered beneath their closed eyelids. Later he used a polygraph machine to record the sleepers' brainwaves during the periods of this activity of their eyes. In one session, he awakened a subject who was wailing and crying out during REM and confirmed his suspicion that dreaming was occurring.^[18] In 1953, Aserinsky and his advisor published the ground-breaking study in Science.^[19]

Accumulated observation has shown that dreams are strongly associated with rapid eye movement sleep, during which an electroencephalogram (EEG) shows brain activity that, among sleep states, is most like wakefulness. Participant-remembered dreams during NREM sleep are normally more mundane in comparison.^[20] During a typical lifespan, a person spends a total of about six years dreaming^[21] (which is about two hours each night).^[22] Most dreams only last 5 to 20 minutes.^[21] It is unknown where in the brain dreams originate, if there is a single origin for dreams or if multiple portions of the brain are involved, or what the purpose of dreaming is for the body or mind.

During REM sleep, the release of the neurotransmitters norepinephrine, serotonin and histamine is completely suppressed.^[23][24][25] As a result, motor neurons are not stimulated, a condition known as REM atonia. This prevents dreams from resulting in dangerous movements of the body.

According to a report in the journal Neuron, rat brains show evidence of complex activity during sleep, including the activation in memory of long sequences of activity.^[26][27] Studies show that various species of mammals and birds experience REM during sleep,^[28] and follow the same series of sleeping states as humans.^[26]

Despite their power to bewilder, arouse, frighten or amuse, dreams can often be ignored in mainstream models of cognitive psychology.^[29] As methods of introspection were replaced with more self-consciously objective methods in the social sciences in 1930s and 1940s, dream studies dropped out of the scientific literature. Dreams were neither directly observable by an experimenter nor were subjects' dream reports reliable, being prey to the familiar problems of distortion due to delayed recall, if they were recalled at all. According to Sigmund Freud, dreams are more often forgotten entirely, perhaps due to their prohibited character. Altogether, these problems seemed to put them beyond the realm of science.

The discovery that dreams take place primarily during a distinctive electrophysiological state of sleep, rapid eye movement (REM) sleep, which can be identified by objective criteria, led to the rebirth of interest in this phenomenon. When REM sleep episodes were timed for their duration and subjects woken to make reports before major editing or forgetting could take place, it was determined that subjects accurately matched the length of time they judged the dream narrative to be ongoing to the length of REM sleep that preceded the awakening. There is no "time dilation" effect; a five-minute dream takes roughly five minutes of real time to play out.^[30] This close correlation of REM sleep and dream experience was the basis of the first series of reports describing the nature of dreaming: that it is a regular nightly, rather than occasional, phenomenon, and a high-frequency activity within each sleep period occurring at predictable intervals of approximately every 60–90 minutes in all humans throughout the life span.

REM sleep episodes and the dreams that accompany them lengthen progressively across the night, with the first episode being shortest, of approximately 10–12 minutes duration, and the second and third episodes increasing to 15–20 minutes. Dreams at the end of the night may last as long as 15 minutes, although these may be experienced as several distinct stories due to momentary arousals interrupting sleep as the night ends. Dream reports can be reported from normal subjects on 50% of the occasion when an awakening is made prior to the end of the first REM period. This rate of retrieval is increased to about 99% when awakenings are made from the last REM period of the night. This increase in the ability to recall appears related to intensification across the night in the vividness of dream imagery, colors, and emotions.^{[citation needed]}

Dreams in animals

REM sleep and the ability to dream seem to be embedded in the biology of many organisms that live on Earth. All mammals experience REM. The range of REM can be seen across species: dolphins experience minimum REM, while humans remain in the middle and the opossum and the armadillo are among the most prolific dreamers.^[31]

Studies have observed dreaming in monkeys, dogs, cats, rats, elephants and shrews. There have also been signs of dreaming in certain birds and reptiles.^[32]Sleeping and dreaming are intertwined. Scientific research results regarding the function of dreaming in animals remain disputable, however, the function of sleeping in living organisms is increasingly clear. For example, recent sleep deprivation experiments conducted on rats and other animals have resulted in the deterioration of physiological functioning and actual tissue damage of the animals.^[33]

In 1954 the Theta rhythm was discovered by two scientists at the University of California at Los Angeles when experimenting with rabbits, shrews, moles and rats. The Theta Rhythm is the oscillatory pattern of electric activity in the brain. This discovery lead to a commentary published in 1972 that explained differences in Theta Rhythm where defined by respective animal behaviors. Awake animals showed high Theta Rhythm when behaving in ways that where crucial to their survival, for example: eating and reproducing. This apparently was a response to a changing environment. The Theta Rhythm occurs during REM and studies suggest it "reflected a neural process whereby information that is essential to the survival of the species" is gathered throughout the day and is "reprocessed into memory during REM sleep". In conclusion: "dreams may reflect a memory-processing mechanism inherited from lower species".^[34]

Some scientists argue that humans dream for the same reason other mammals do. From a Darwinian perspective dreams would have to fulfill some kind of biological requirement or provide some benefit for natural selection to take place. Antti Revonsuo, a professor at the University of Turku in Finland, claims that centuries ago dreams would prepare humans for recognizing and avoiding danger by presenting a simulation of threatening events. This threat-simulation theory was presented in 2000.^[35]

Neurological theories of dreams

Activation synthesis theory

Main article: Activation-synthesis hypothesis

In 1976 J. Allan Hobson and Robert McCarley proposed a new theory that changed dream research, challenging the previously held Freudian view of dreams as subconscious wishes to be interpreted. Activation synthesis theory asserts that the sensory experiences are fabricated by the cortex as a means of interpreting chaotic signals from the pons. They propose that during REM sleep, the ascending cholinergic PGO (ponto-geniculo-occipital) waves stimulate higher midbrain and forebrain cortical structures, producing rapid eye movements. The activated forebrain then synthesizes the dream out of this internally generated information. They assume that the same structures that induce REM sleep also generate sensory information.

Hobson's 1976 research suggested that the signals interpreted as dreams originated in the brain stem during REM sleep. However, research by Mark Solms suggests that dreams are generated in the forebrain, and that REM sleep and dreaming are not directly related.^[36] While working in the neurosurgery department at hospitals in Johannesburg and London, Solms had access to patients with various brain injuries. He began to question patients about their dreams and confirmed that patients with damage to the parietal lobe stopped dreaming; this finding was in line with Hobson's 1977 theory. However, Solms did not encounter cases of loss of dreaming with patients having brain stem damage. This observation forced him to question Hobson's prevailing theory, which marked the brain stem as the source of the signals interpreted as dreams.

Solms viewed the idea of dreaming as a function of many complex brain structures as validating Freudian dream theory, an idea that drew criticism from Hobson. In 1978, Solms, along with partners William Kauffman and Edward Nadar, undertook a series of traumatic-injury impact studies using several different species of primates, particularly howler monkeys, in order to disprove Hobson's postulation that the brain stem played a significant role in dream pathology. Unfortunately, Solms' experiments proved inconclusive, as the high mortality rate associated with using a hydraulic impact pin to artificially induce brain damage in test subjects meant that his final candidate pool was too small to satisfy the requirements of the scientific method.^[37]

Continual-activation theory

Combining Hobson's activation synthesis hypothesis with Solms' findings, the continual-activation theory of dreaming presented by Jie Zhang proposes that dreaming is a result of brain activation and synthesis; at the same time, dreaming and REM sleep are controlled by different brain mechanisms. Zhang hypothesizes that the function of sleep is to process, encode and transfer the data from the short-term memory to the long-term memory, though there is not much evidence backing up this so-called "consolidation." NREM sleep processes the conscious-related memory (declarative memory), and REM sleep processes the unconscious related memory (procedural memory).

Zhang assumes that during REM sleep the unconscious part of a brain is busy processing the procedural memory; meanwhile, the level of activation in the conscious part of the brain descends to a very low level as the inputs from the sensory are basically disconnected. This triggers the "continual-activation" mechanism to generate a data stream from the memory stores to flow through the conscious part of the brain. Zhang suggests that this pulse-like brain activation is the inducer of each dream. He proposes that, with the involvement of the brain associative thinking system, dreaming is, thereafter, self-maintained with the dreamer's own thinking until the next pulse of memory insertion. This explains why dreams have both characteristics of continuity (within a dream) and sudden changes (between two dreams).^[38][39]

Dreams as excitations of long-term memory

Eugen Tarnow suggests that dreams are ever-present excitations of long-term memory, even during waking life. The strangeness of dreams is due to the format of long-term memory, reminiscent of Penfield & Rasmussen's findings that electrical excitations of the cortex give rise to experiences similar to dreams. During waking life an executive function interprets long-term memory consistent with reality checking. Tarnow's theory is a reworking of Freud's theory of dreams in which Freud's unconscious is replaced with the long-term memory system and Freud's "Dream Work" describes the structure of long-term memory.^[40]

Dreams for strengthening of semantic memories

Location of hippocampus

A 2001 study showed evidence that illogical locations, characters, and dream flow may help the brain strengthen the linking and consolidation of semantic memories.^[41] These conditions may occur because, during REM sleep, the flow of information between the hippocampus and neocortex is reduced.^[42] Increasing levels of the stress hormone cortisol late in sleep (often during REM sleep) cause this decreased communication. One stage of memory consolidation is the linking of distant but related memories. Payne and Nadal hypothesize these memories are then consolidated into a smooth narrative, similar to a process that happens when memories are created under stress.^[43]

Dreams for removing junk

Robert (1886),^[44] a physician from Hamburg, was the first who suggested that dreams are a need and that they have the function to erase (a) sensory impressions that were not fully worked up, and (b) ideas that were not fully developed during the day. By the dream work, incomplete material is either removed (suppressed) or deepened and included into memory. Robert's ideas were cited repeatedly by Freud in his Die Traumdeutung. Hughlings Jackson (1911) viewed that sleep serves to sweep away unnecessary memories and connections from the day. This was revised in 1983 by Crick and Mitchison's "reverse learning" theory, which states that dreams are like the cleaning-up operations of computers when they are off-line, removing (suppressing) parasitic nodes and other "junk" from the mind during sleep.^[45][46] However, the opposite view that dreaming has an information handling, memory-consolidating function (Hennevin and Leconte, 1971) is also common. Dreams are a result of the spontaneous firings of neural patterns while the brain is undergoing memory consolidation while sleeping.

Dreams as resonance in neural circuits

During sleep the eyes are closed, so that the brain to some degree becomes isolated from the outside world. Moreover all signals from the senses (except olfaction) must pass through the thalamus before they reach the brain cortex, and during sleep thalamic activity is suppressed.^[47] This means that the brain mainly works with signals from itself. A well-known phenomenon in dynamical physical systems where the level of input and output from the system is low is that oscillation makes spontaneous resonance patterns to occur. Hence, dreams may be the simple consequence of neural oscillation.

Psychological theories of dreams

Dreams for testing and selecting mental schemas

Coutts^[48] describes dreams as playing a central role in a two-phase sleep process that improves the mind's ability to meet human needs during wakefulness. During the accommodation phase, mental schemas self-modify by incorporating dream themes. During the emotional selection phase, dreams test prior schema accommodations. Those that appear adaptive are retained, while those that appear maladaptive are culled. The cycle maps to the sleep cycle, repeating several times during a typical nights sleep. Alfred Adler suggested that dreams are often emotional preparations for solving problems, intoxicating an individual away from common sense toward private logic. The residual dream feelings may either reinforce or inhibit contemplated action.

Evolutionary psychology theories of dreams

Numerous theories state that dreaming is a random by-product of REM sleep physiology and that it does not serve any natural purpose.^[49] Flanagan claims that "dreams are evolutionary epiphenomena" and they have no adaptive function in the least. "Dreaming came along as a free ride on a system designed to think and to sleep.^[50]" Hobson, for different reasons, also considers dreams epiphenomena. He believes that the substance of dreams have no significant influence on waking actions, and most people go about their daily lives perfectly well without remembering their dreams.^[51]

Hobson proposed the activation-synthesis theory, which states that "there is a randomness of dream imagery and the randomness synthesizes dream-generated images to fit the patterns of internally generated stimulations".^[52] This theory is based on the physiology of REM sleep, and Hobson believes dreams are the outcome of the forebrain reacting to random activity beginning at the brainstem. Overall, this theory has obtained broad support for a while because it corresponds to physiological data and its explanation of dreaming applies to a majority of peoples’ random dream experiences.^[53] The activation-synthesis theory hypothesizes that the peculiar nature of dreams is attributed to certain parts of the brain trying to piece together a story out of what is essentially bizarre information.^[54]

However, evolutionary psychologists believe dreams serve some adaptive function for survival. Deirdre Barrett describes dreaming as simply "thinking in different biochemical state" and believes people continue to work on all the same problems—personal and objective—in that state.^[55] Her research finds that anything—math, musical composition, business dilemmas—may get solved during dreaming, but the two areas especially likely to help are 1) anything where vivid visualization contributes to the solution, whether in artistic design or invention of 3-D technological devices and 2) problem where the solution lies in "thinking outside the box"—i.e. the person is stuck because conventional wisdom on how to approach the problem is wrong.^[56][57] In a related theory, which Mark Blechner terms "Oneiric Darwinism," dreams are seen as creating new ideas through the generation of random thought mutations. Some of these may be rejected by the mind as useless, while others may be seen as valuable and retained.^[58]

Finnish psychologist Antti Revonsuo posits that dreams have evolved for "threat simulation" exclusively. According to the Threat Simulation Theory he proposes, during much of human evolution physical and interpersonal threats were serious, giving reproductive advantage to those who survived them. Therefore dreaming evolved to replicate these threats and continually practice dealing with them. In support of this theory, Revonsuo shows that contemporary dreams comprise much more threatening events than people meet in daily non-dream life, and the dreamer usually engages appropriately with them.^[59] It is suggested by this theory that dreams serve the purpose of allowing for the rehearsal of threatening scenarios in order to better prepare an individual for real-life threats.

A more extensive view of ‘dreaming as play’ is proposed by Humphrey who proposes we dream to practice many different physical, intellectual and social skills, not just to evolve past threats.^[59]

The main competitors against this kind of theory regard dreaming as a necessary by-product of random cortical activation, which occurs for other reasons.^[59] Crick and Mitchison believe that "cortical neural networks become overloaded during learning and that the function of REM sleep is to remove superfluous connections by randomly flooding them".^[59] In other words this theory believes we dream so that we can forget^{[citation needed]}.

Psychosomatic theory of dreams

Y.D. Tsai developed in 1995 a 3-hypothesis theory^[60] that is claimed to provide a mechanism for mind-body interaction and explain many dream-related phenomena, including hypnosis, meridians in Chinese medicine, the increase in heart rate and breathing rate during REM sleep, that babies have longer REM sleep, lucid dreams, etc.

Dreams are a product of "dissociated imagination," which is dissociated from the conscious self and draws material from sensory memory for simulation, with feedback resulting in hallucination. By simulating the sensory signals to drive the autonomous nerves, dreams can affect mind-body interaction. In the brain and spine, the autonomous "repair nerves," which can expand the blood vessels, connect with compression and pain nerves. Repair nerves are grouped into many chains called meridians in Chinese medicine. When some repair nerves are prodded by compression or pain to send out their repair signals, a chain reaction spreads out to set other repair nerves in the same meridian into action. While dreaming, the body also employs the meridians to repair the body and help it grow and develop by simulating very intensive movement-compression signals to expand the blood vessels when the level of growth enzymes increase.

Other hypotheses on dreaming

There are many other hypotheses about the function of dreams, including:^[61]

• Dreams allow the repressed parts of the mind to be satisfied through fantasy while keeping the conscious mind from thoughts that would suddenly cause one to awaken from shock.^[62]
• Freud suggested that bad dreams let the brain learn to gain control over emotions resulting from distressing experiences.^[61]
• Jung suggested that dreams may compensate for one-sided attitudes held in waking consciousness.^[63]
• Ferenczi^[64] proposed that the dream, when told, may communicate something that is not being said outright.
• Dreams regulate mood.^[65]
• Hartmann^[66] says dreams may function like psychotherapy, by "making connections in a safe place" and allowing the dreamer to integrate thoughts that may be dissociated during waking life.
• More recent research by psychologist Joe Griffin, following a twelve-year review of data from all major sleep laboratories, led to the formulation of the expectation fulfilment theory of dreaming, which suggests that dreaming metaphorically completes patterns of emotional expectation in the autonomic nervous system and lowers stress levels in mammals.^[67][68]

Dream content

From the 1940s to 1985, Calvin S. Hall collected more than 50,000 dream reports at Western Reserve University. In 1966 Hall and Van De Castle published The Content Analysis of Dreams in which they outlined a coding system to study 1,000 dream reports from college students.^[69] It was found that people all over the world dream of mostly the same things. Hall's complete dream reports became publicly available in the mid-1990s by Hall's protégé William Domhoff, allowing further different analysis. Personal experiences from the last day or week are frequently incorporated into dreams.^[70]

Visuals

The visual nature of dreams is generally highly phantasmagoric; that is, different locations and objects continuously blend into each other. The visuals (including locations, characters/people, objects/artifacts) are generally reflective of a person's memories and experiences, but often take on highly exaggerated and bizarre forms.

Emotions

The most common emotion experienced in dreams is anxiety. Other emotions include abandonment, anger, fear, joy, happiness, etc. Negative emotions are much more common than positive ones.^[69]

Sexual themes

The Hall data analysis shows that sexual dreams occur no more than 10% of the time and are more prevalent in young to mid-teens.^[69] Another study showed that 8% of men's and women's dreams have sexual content.^[71] In some cases, sexual dreams may result in orgasms or nocturnal emissions. These are colloquially known as wet dreams.^[72]

Recurring dreams

While the content of most dreams is dreamt only once, many people experience recurring dreams—that is, the same dream narrative or dreamscape is experienced over different occasions of sleep.

Color vs. black and white

A small minority of people say that they dream only in black and white.^[73][74]

Dream interpretations

Main article: Dream interpretation

Dreams were historically used for healing (as in the asclepieions found in the ancient Greek temples of Asclepius) as well as for guidance or divine inspiration. Some Native American tribes used vision quests as a rite of passage, fasting and praying until an anticipated guiding dream was received, to be shared with the rest of the tribe upon their return.^[75]

During the late 19th and early 20th centuries, both Sigmund Freud and Carl Jung thought of dreams as an interaction between the unconscious and the conscious. They also assert together that the unconscious is the dominant force of the dream, and in dreams it conveys its own mental activity to the perceptive faculty. While Freud felt that there was an active censorship against the unconscious even during sleep, Jung argued that the dream's bizarre quality is an efficient language, comparable to poetry and uniquely capable of revealing the underlying meaning.

Fritz Perls presented his theory of dreams as part of the holistic nature of Gestalt therapy. Dreams are seen as projections of parts of the self that have been ignored, rejected, or suppressed.^[76] Jung argued that one could consider every person in the dream to represent an aspect of the dreamer, which he called the subjective approach to dreams. Perls expanded this point of view to say that even inanimate objects in the dream may represent aspects of the dreamer. The dreamer may, therefore, be asked to imagine being an object in the dream and to describe it, in order to bring into awareness the characteristics of the object that correspond with the dreamer's personality.

Dream interpretation can be a result of subjective ideas and experiences. A recent study conducted by the Journal of Personality and Social Psychology concluded that most people believe that "their dreams reveal meaningful hidden truths". The study was conducted in the United States, South Korea and India. 74% Indians, 65% South Koreans and 56% Americans believe in Freud’s dream theories. ^[77] Furthermore, the studies of Phycologists Michael Norton of Harvard University and Carey Morewedge of Carnegie Mellon University reflect that humans are irrational about dreams because they try to put together unrelated information to convey a meaning. According to these series of studies, we are irrational about dreams they same way we are irrational in our every day decisions. In their search for meaning, humans can turn to dreams in order to find answers and explanations. The studies find that dreams reflect the human trait of optimistic thinking since the results depict that humans tend to focus more on dreams where good things take place.^[77]

Relationship with medical conditions

There is evidence that certain medical conditions (normally only neurological conditions) can impact dreams. For instance, some people with synesthesia have never reported entirely black-and-white dreaming, and often have a difficult time imagining the idea of dreaming in only black and white.^[78]

Therapy for recurring nightmares (often associated with posttraumatic stress disorder) can include imagining alternative scenarios that could begin at each step of the dream.^[79]

Dreams and psychosis

A number of thinkers have commented on the similarities between the phenomenology of dreams and that of psychosis. Features common to the two states include thought disorder, flattened (i.e. diminished) or inappropriate affect (emotion), and hallucinations. Among philosophers, Immanuel Kant, for example, wrote that "the lunatic is a wakeful dreamer."^[80] Arthur Schopenhauer said: "A dream is a short-lasting psychosis, and a psychosis is a long-lasting dream."^[81] In the field of psychoanalysis, Sigmund Freud wrote: "A dream then, is a psychosis,"^[82] and Carl Jung: "Let the dreamer walk about and act like one that is awake and we have the clinical picture of dementia praecox."^[83]

McCreery^[84][85] has sought to explain these similarities by reference to the fact, documented by Oswald,^[86] that sleep can supervene as a reaction to extreme stress and hyper-arousal. McCreery adduces evidence that psychotics are people with a tendency to hyper-arousal, and suggests that this renders them prone to what Oswald calls "microsleeps" during waking life. He points in particular to the paradoxical finding of Stevens and Darbyshire^[87] that patients suffering from catatonia can be roused from their seeming stupor by the administration of sedatives rather than stimulants.

Griffin and Tyrrell^[88] go so far as to say that "schizophrenia is waking reality processed through the dreaming brain."^[89]

Other associated phenomena

Incorporation of reality

During the night, many external stimuli may bombard the senses, but the brain often interprets the stimulus and makes it a part of a dream to ensure continued sleep.^[90] Dream incorporation is a phenomenon whereby an actual sensation, such as environmental sounds, are incorporated into dreams, such as hearing a phone ringing in a dream while it is ringing in reality or dreaming of urination while wetting the bed. The mind can, however, awaken an individual if they are in danger or if trained to respond to certain sounds, such as a baby crying. Except in the case of lucid dreaming, people dream without being aware that they are doing so.

The term "dream incorporation" is also used in research examining the degree to which preceding daytime events become elements of dreams. Recent studies suggest that events in the day immediately preceding, and those about a week before, have the most influence.^[70]

Apparent precognition of real events

Main article: Precognition

According to surveys, it is common for people to feel their dreams are predicting subsequent life events.^[91] Psychologists have explained these experiences in terms of memory biases, namely a selective memory for accurate predictions and distorted memory so that dreams are retrospectively fitted onto life experiences.^[91] The multi-faceted nature of dreams makes it easy to find connections between dream content and real events.^[92]

In one experiment, subjects were asked to write down their dreams in a diary. This prevented the selective memory effect, and the dreams no longer seemed accurate about the future.^[93] Another experiment gave subjects a fake diary of a student with apparently precognitive dreams. This diary described events from the person's life, as well as some predictive dreams and some non-predictive dreams. When subjects were asked to recall the dreams they had read, they remembered more of the successful predictions than unsuccessful ones.^[94]

Lucid dreaming

Main article: Lucid dreaming

Lucid dreaming is the conscious perception of one's state while dreaming. In this state a person usually has control over characters and the environment of the dream as well as the dreamer's own actions within the dream.^[95] The occurrence of lucid dreaming has been scientifically verified.^[96]

Oneironaut is a term sometimes used for those who lucidly dream.

Dreams of absent-minded transgression

Dreams of absent-minded transgression (DAMT) are dreams wherein the dreamer absentmindedly performs an action that he or she has been trying to stop (one classic example is of a quitting smoker having dreams of lighting a cigarette). Subjects who have had DAMT have reported waking with intense feelings of guilt. One study found a positive association between having these dreams and successfully stopping the behavior.^[97]

Recalling dreams

The recall of dreams is extremely unreliable, though it is a skill that can be trained. Dreams can usually be recalled if a person is awakened while dreaming.^[79] Women tend to have more frequent dream recall than men.^[79] Dreams that are difficult to recall may be characterized by relatively little affect, and factors such as salience, arousal, and interference play a role in dream recall. Often, a dream may be recalled upon viewing or hearing a random trigger or stimulus. A dream journal can be used to assist dream recall, for psychotherapy or entertainment purposes.

For some people, vague images or sensations from the previous night's dreams are sometimes spontaneously experienced in falling asleep. However they are usually too slight and fleeting to allow dream recall. At least 95% of all dreams are not remembered. Certain brain chemicals necessary for converting short-term memories into long-term ones are suppressed during REM sleep. Unless a dream is particularly vivid and if one wakes during or immediately after it, the content of the dream is not remembered.^[98]

Déjà vu

Main article: Déjà vu

One theory of déjà vu attributes the feeling of having previously seen or experienced something to having dreamt about a similar situation or place, and forgetting about it until one seems to be mysteriously reminded of the situation or the place while awake.^[99]

Sleepwalking

Sleepwalking was once thought of as "acting out a dream", but that theory has fallen out of favour.

Daydreaming

A daydream is a visionary fantasy, especially one of happy, pleasant thoughts, hopes or ambitions, imagined as coming to pass, and experienced while awake.^[100] There are many different types of daydreams, and there is no consistent definition amongst psychologists.^[100] The general public also uses the term for a broad variety of experiences. Research by Harvard psychologist Deirdre Barrett has found that people who experience vivid dream-like mental images reserve the word for these, whereas many other people refer to milder imagery, realistic future planning, review of past memories or just "spacing out"--i.e. one's mind going relatively blank—when they talk about "daydreaming."^[101]

While daydreaming has long been derided as a lazy, non-productive pastime, it is now commonly acknowledged that daydreaming can be constructive in some contexts.^[102] There are numerous examples of people in creative or artistic careers, such as composers, novelists and filmmakers, developing new ideas through daydreaming. Similarly, research scientists, mathematicians and physicists have developed new ideas by daydreaming about their subject areas.

Hallucination

A hallucination, in the broadest sense of the word, is a perception in the absence of a stimulus. In a stricter sense, hallucinations are perceptions in a conscious and awake state, in the absence of external stimuli, and have qualities of real perception, in that they are vivid, substantial, and located in external objective space. The latter definition distinguishes hallucinations from the related phenomena of dreaming, which does not involve wakefulness.

Nightmares

"Nachtmahr" ("Night-mare"), Johann Heinrich Füssli (1802)

A nightmare is an unpleasant dream that can cause a strong negative emotional response from the mind, typically fear and/or horror, but also despair, anxiety and great sadness. The dream may contain situations of danger, discomfort, psychological or physical terror. Sufferers usually awaken in a state of distress and may be unable to return to sleep for a prolonged period of time.^[103]

Night terrors

A night terror, also known as a sleep terror or pavor nocturnus, is a parasomnia disorder that predominantly affects children, causing feelings of terror or dread. Night terrors should not be confused with nightmares, which are bad dreams that cause the feeling of horror or fear.

Fugue states

A fugue state, formally "dissociative fugue" or "psychogenic fugue" (DSM-IV Dissociative Disorders 300.13^[104]), is a rare psychiatric disorder characterized by reversible amnesia for personal identity, including the memories, personality and other identifying characteristics of individuality. The state is usually short-lived (hours to days), but can last months or longer. Dissociative fugue usually involves unplanned travel or wandering, and is sometimes accompanied by the establishment of a new identity. After recovery from fugue, previous memories usually return intact, but there is complete amnesia for the fugue episode. Additionally, an episode is characterized as a fugue if it can be related to the ingestion of psychotropic substances, to physical trauma, to a general medical condition, or to psychiatric conditions such as delirium, dementia, bipolar disorder or depression. Fugues are usually precipitated by a stressful episode, and upon recovery there may be amnesia for the original stressor ("Dissociative Amnesia").

In culture

"The Dream" by Edouard Detaille. Soldiers dreaming about glory.

In art

Dreams and dark imaginings are the theme of Goya's etching The Sleep of Reason Produces Monsters. There is a painting by Salvador Dalí that depicts this concept, titled Dream Caused by the Flight of a Bee around a Pomegranate a Second Before Awakening (1944). Rousseau's last painting was The Dream. Le Rêve ("The Dream") is a 1932 painting by Pablo Picasso.

In literature

Dream frames were frequently used in medieval allegory to justify the narrative; The Book of the Duchess and Piers Plowman are two such dream visions.

The Cheshire Cat vanishes in Wonderland.

They have also featured in fantasy and speculative fiction since the 19th century. One of the best-known dream worlds is Wonderland from Lewis Carroll's Alice's Adventures in Wonderland, as well as Looking-Glass Land from its sequel, Through the Looking-Glass. Unlike many dream worlds, Carroll's logic is like that of actual dreams, with transitions and flexible causality.

Other fictional dream worlds include the Dreamlands of H. P. Lovecraft's Dream Cycle and The Neverending Story's world of Fantasia, which includes places like the Desert of Lost Dreams, the Sea of Possibilities and the Swamps of Sadness. Dreamworlds, shared hallucinations and other alternate realities feature in a number of works by Phillip K. Dick, such as The Three Stigmata of Palmer Eldritch and Ubik. Similar themes were explored by Jorge Luis Borges, for instance in The Circular Ruins.

In popular culture

Modern popular culture often conceives of dreams, like Freud, as expressions of the dreamer's deepest fears and desires.^[105] In films such as Spellbound (1945), The Manchurian Candidate (1962) and Inception (2010), the protagonists must extract vital clues from surreal dreams.^[106]

Most dreams in popular culture are, however, not symbolic, but straightforward and realistic depictions of their dreamer's fears and desires.^[106] Dream scenes may be indistinguishable from those set in the dreamer's real world, a narrative device that undermines the dreamer's and the audience's sense of security^[106] and allows horror movie protagonists, such as those of Carrie (1976), Friday the 13th (1980) or An American Werewolf in London (1981) to be suddenly attacked by dark forces while resting in seemingly safe places.^[106]

In speculative fiction, the line between dreams and reality may be blurred even more in the service of the story.^[106] Dreams may be psychically invaded or manipulated (Dreamscape, 1984; the Nightmare on Elm Street films, 1984–1991; Inception, 2010) or even come literally true (as in The Lathe of Heaven, 1971). Peter Weir's 1977 Australian movie "The Last Wave" makes a simple and straightforward postulate about the premonitory nature of dreams (from one of his Aboriginal characters) that "...dreams are the shadow of something real". Such stories play to audiences' experiences with their own dreams, which feel as real to them.^[106]

One of the earliest newspaper comic strips, recounting Little Nemo's adventures in Slumberland, had a dream world theme.

Graphic novelist Neil Gaiman was tasked with re-imagining a Golden Age character, "The Sandman". In his version, the Sandman becomes Dream, the Lord of Dreams (also known, to various characters throughout the series, as Morpheus, Oneiros, the Shaper, the Shaper of Form, Lord of the Dreaming, the Dream King, Dream-Sneak, Dream Cat, Murphy, Kai'ckul, and Lord L'Zoril), who is essentially the anthropomorphic personification of dreams. At the start of the series, Morpheus is captured by an occult ritual and held prisoner for 70 years. Morpheus escapes in the modern day and, after avenging himself upon his captors, sets about rebuilding his kingdom, which has fallen into disrepair in his absence.

In philosophy and religion

Aboriginal beliefs

The Dreaming is a common term within the animist creation narrative of indigenous Australians for a personal, or group, creation and for what may be understood as the "timeless time" of formative creation and perpetual creating.

In addition, the term applies to places and localities on indigenous Australian traditional land (and throughout non-traditional Australia) where the uncreated creation spirits and totemic ancestors, or genius loci, reside.^[107] No one English word covers the concept; for example, Anangu who speak Pitjantjatjara use the word Tjukurpa and those who speak Yankunytjatjara use Wapar, but neither means dreaming in the English sense.^[108]

Dreams and philosophical realism

Main article: Dream argument

Some philosophers have concluded that what we think of as the "real world" could be or is an illusion (an idea known as the skeptical hypothesis about ontology).

The first recorded mention of the idea was by Zhuangzi, and it is also discussed in Hinduism, which makes extensive use of the argument in its writings.^[109] It was formally introduced to Western philosophy by Descartes in the 17th century in his Meditations on First Philosophy. Stimulus, usually an auditory one, becomes a part of a dream, eventually then awakening the dreamer.

See also

• Cognitive neuroscience of dreams           
• Dimethyltryptamine
• Dream art
• Dream dictionary
• Dream pop
• Dream sequence
• Dream speech
• Dream world (plot device)
• Dream Yoga
• Dreamcatcher
• Dreamwork
• Ethereal being
• Incubus
• Lilith, a Sumerian dream demon           
• List of dream diaries
• List of dreams
• Lucid Dream
• Mara (folklore)
• Morpheus (mythology)
• Oneiromancy
• Spirit spouse (in dreams)
• Succubus
• Veridical dream

References

Notes

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Further reading

• Freud, Sigmund (1994). The interpretation of dreams. New York: Modern Library. ISBN 067960121X. 
• Jung, Carl (1934). The Practice of Psychotherapy. "The Practical Use of Dream-analysis". New York: Routledge & Kegan Paul. pp. 139-. ISBN 071001645X. 
• Jung, Carl (2002). Dreams (Routledge Classics). New York: Routledge. ISBN 0415267404. 
• Harris, William V., Dreams and Еxperience in Classical Antiquity (Cambridge, Mass.; London: Harvard University Press, 2009).

External links

• Dreams on In Our Time at the BBC. (listen now)
• Dream Psychology by Sigmund Freud
• The Dream & Nightmare Laboratory in Montreal
• Archive for Research in Archetypal Symbolism website
• The International Association for the Study of Dreams
• More information on the expectation fulfilment theory of dreaming
• Dreams at the Open Directory Project
• Dixit, Jay (2007). "Dreams: Night School". Psychology Today. http://www.psychologytoday.com/articles/index.php?term=20071029-000003.