Why do we dream? What science has found so far

Everyone dreams

Even people who say they never dream usually dream several times a night. The difference is in remembering. For a long time dreaming was thought to happen only in REM sleep, the stage when the eyes move quickly under the lids. We now know dreams also occur in other stages, although REM dreams tend to be longer and more vivid.

Where the brain dreams

Researchers in Switzerland and the United States woke volunteers many times during the night and asked whether they had been dreaming, while recording brain activity with high-density EEG. They identified an area at the back of the brain, which they called the posterior hot zone, whose activity indicated whether the person was dreaming, in REM sleep and outside it. The pattern was clear enough to predict, from the signal alone, whether the volunteer would report a dream.

Source: Siclari et al., The neural correlates of dreaming, Nature Neuroscience, 2017.

Freud, Jung and faith on this dream

In Freud's psychoanalysis. We dream, Freud said, to fulfill wishes: a dream would be the disguised fulfillment of a suppressed or repressed wish. Everyday language, he noted, already treats dreams this way: faced with an unexpected joy, we say we never would have imagined it, not even in our wildest dreams. To him, the dream was also the guardian of sleep.

In Jung's psychology. Jung disagreed. The idea of dreams as guardians of sleep left him skeptical, because, as he wrote, dreams are always disturbing sleep. Nor did he see the images as a disguise: just as a plant produces flowers, he wrote, the psyche creates its symbols. In his view, the general function of dreams is to try to restore our psychological balance, compensating for what waking life exaggerates or ignores.

In symbols and faith. In ancient Egypt, Chevalier and Gheerbrant note in A Dictionary of Symbols, a wisdom book said the god created dreams to show people the way when they cannot see the future. In the Bible, Job 33:14-16 says God speaks "in a dream, in a vision of the night, when deep sleep falleth upon men." And the Brazilian dream book O Livro dos Sonhos, by L. P. Baçan, gives the entry for the dream itself an upbeat reading: in life, success in your activities; in love, happiness.

Bringing both views together. Among a people in West Africa, Jung was told that ordinary people's dreams mean nothing; only the dreams of chiefs and medicine men counted. To him, that was the attitude of modern people who think their dreams are meaningless just because they don't understand them. Science explains how the brain builds a dream from memories and emotions; theory and faith ask what it means. One answer doesn't cancel the other, as the guide to what dreams mean shows.

Sources: Freud, Die Traumdeutung, 1900; Jung (ed.), Man and His Symbols; Chevalier and Gheerbrant, A Dictionary of Symbols; L. P. Baçan, O Livro dos Sonhos, 2014.

Does dreaming help learning?

In an experiment published in Current Biology, volunteers trained on a virtual maze task and then took a nap. Those who reported dreaming about the task performed much better on the second attempt than those who did not. For the authors, the dream may be a sign that the brain is reprocessing and strengthening what was just learned.

Source: Wamsley et al., Dreaming of a Learning Task Is Associated with Enhanced Sleep-Dependent Memory Consolidation, Current Biology, 2010.

Why we forget dreams

On waking, a dream fades fast unless it is recorded. If you want to remember more, keep paper by the bed and write everything down in the first minutes, before touching your phone. Waking suddenly in the middle of a dream also raises the chance of recall.

Do dreams have meaning?

There is no scientific basis for dream dictionaries that promise to predict the future. What studies show is that dreams mix recent memories, emotions and worries. Frequent nightmares that disrupt sleep are worth discussing with a health professional.

See also dream meanings and sleep paralysis.

Read also: lucid dreaming, according to science; What is déjà vu? The science behind it, no mystery.