forgotten

In 1997,[70] Joe Griffin published a new theory to explain dreams, which later became known as the
 expectation fulfilment theory of dreams. After years of research on his own dreams and those of others, he found that
 dreaming serves to discharge the emotional arousals (however minor) that haven't been expressed during the day, thus
 freeing up space in the brain to deal with the emotional arousals of the next day and allowing instinctive urges
 to stay intact. In effect, the expectation is fulfilled, i.e. the action is 'completed', in the dream but in a
metaphorical form, so that a false memory is not created. The theory satisfactorily explains why dreams are usually
forgotten immediately afterwards: as Griffin suggests, far from being "the cesspit of the unconscious", as Freud
proclaimed, dreaming is the equivalent of the flushed toilet.
The most common type of home run involves hitting the ball over the outfield fence, or above a line on the outfield fence specifically designed to indicate a home run, in flight, in fair territory, without it being caught or deflected back by an outfielder into the playing field. This is sometimes called a home run "out of the ballpark", although that term is frequently used to indicate a blow that completely clears any outfield seating, as a home run is usually automatically assumed to have left the field of play unless otherwise indicated. A batted ball that hits the ground (in fair territory) and bounces out of play is not a home run, but an "automatic double" in most stadiums (colloquially called a ground rule double).

A batted ball is also considered a home run if the ball touches any of the following while in flight, even if the ball subsequently rebounds back onto the playing field:

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imagination

Coutts[58] 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 night's 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.[59] Flanagan claims that "dreams are evolutionary epiphenomena" and they have no adaptive function. "Dreaming came along as a free ride on a system designed to think and to sleep.[60] " 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.[61]

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".[62] 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. 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.[63]

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.[64] Her research finds that anything—math, musical composition, business dilemmas—may get solved during dreaming.[65][66] 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.[67]

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.[68] 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.

According to Tsoukalas (2012) the biology of dreaming is related to the reactive patterns elicited by predatorial encounters (especially the tonic immobility reflex), a fact that lends support to evolutionary theories claiming that dreams specialize in threat avoidance and/or emotional processing.[47]
Psychosomatic theory of dreams

Y.D. Tsai developed in 1995 a 3-hypothesis theory[69] 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.
Expectation fulfilment theory of dreams

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memories

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.[51]
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.[52] These conditions may occur because, during REM sleep, the flow of information between the hippocampus and neocortex is reduced.[53]

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.[54]
Dreams for removing excess sensory information

Robert (1886),[55] 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.[56][57] 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.
Psychological theories of dreams
Dreams for testing and selecting mental schemas

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