Theories of dream function since the identification of REM sleep include:
Hobsons and McCarleys 1977 activation-synthesis hypothesis, which proposed "a functional role for dreaming sleep in promoting some aspect of the learning process...." In 2010 a Harvard study was published showing experimental evidence that dreams were correlated with improved learning.Cricks and Mitchisons 1983 "reverse learning" theory, which states that dreams are like the cleaning-up operations of computers when they are offline, removing (suppressing) parasitic nodes and other "junk" from the mind during sleep.Hartmanns 1995 proposal that dreams serve a "quasi-therapeutic" function, enabling the dreamer to process trauma in a safe place.Revonsuos 2000 threat simulation hypothesis, whose premise is that during much of human evolution, physical and interpersonal threats were serious, giving reproductive advantage to those who survived them. Dreaming aided survival by replicating these threats and providing the dreamer with practice in dealing with them.Eaglemans and Vaughns 2021 defensive activation theory, which says that, given the brains neuroplasticity, dreams evolved as a visual hallucinatory activity during sleeps extended periods of darkness, busying the occipital lobe and thereby protecting it from possible appropriation by other, non-vision, sense operations. Religious and other cultural contexts
Dreams figure prominently in major world religions. The dream experience for early humans, according to one interpretation, gave rise to the notion of a human "soul," a central element in much religious thought.
In one narration by Aisha, the wife of the Prophet, it is said that the Prophets dreams would come true like the oceans waves. Just as in its predecessors, the Quran also recounts the story of Joseph and his unique ability to interpret dreams. Buddhist
In Buddhism, ideas about dreams are similar to the classical and folk traditions in South Asia. The same dream is sometimes experienced by multiple people, as in the case of the Buddha-to-be, before he is leaving his home. It is described in the Mahāvastu that several of the Buddhas relatives had premonitory dreams preceding this. Some dreams are also seen to transcend time: the Buddha-to-be has certain dreams that are the same as those of previous Buddhas, the Lalitavistara states. In Buddhist literature, dreams often function as a "signpost" motif to mark certain stages in the life of the main character.Buddhist views about dreams are expressed in the Pāli Commentaries and the Milinda Pañhā. Other
In Chinese history, people wrote of two vital aspects of the soul of which one is freed from the body during slumber to journey in a dream realm, while the other remained in the body. This belief and dream interpretation had been questioned since early times, such as by the philosopher Wang Chong (27–97 CE).The Babylonians and Assyrians divided dreams into "good," which were sent by the gods, and "bad," sent by demons.