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.^[55] 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.^[56]" 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.^[57]

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".^[58] 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.^[59]

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.^[60] Her research finds that anything—math, musical composition, business dilemmas—may get solved during dreaming.^[61][62] 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.^[63]

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.^[64] 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.

Psychosomatic theory of dreams

Y.D. Tsai developed in 1995 a 3-hypothesis theory^[65] 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.