Why do we dream? What science and psychoanalysis tell us

What exactly is a dream?

A dream is a perceptual, emotional and narrative experience that occurs during sleep — mainly during so-called REM sleep (Rapid Eye Movement), when brain activity resembles wakefulness. During these phases our eyes move rapidly beneath closed lids, the brain is highly active, but the body is temporarily paralysed — an evolutionary safeguard that stops us from physically acting out our dreams.

The work of Nathaniel Kleitman and Eugene Aserinsky at the University of Chicago (1953) was the first to identify REM sleep and its link to vivid dreaming. Sleep neuroscience has advanced considerably since — without, however, fully resolving the question of why.

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The major theories of dream function

1. The psychoanalytic theory: Freud and wish-fulfilment

For Sigmund Freud (The Interpretation of Dreams, 1900), dreams are “the royal road to the unconscious”. They are the disguised fulfilment of a repressed wish — most often a sexual or aggressive desire that the waking conscious mind cannot accept.

According to Freud, the dream is the product of “dream-work” that transforms the latent content (the real, hidden wish) into manifest content (what we remember on waking), through mechanisms such as condensation, displacement and symbolisation.

This theory had a considerable cultural impact, but it is contested scientifically today: neuroscience does not confirm that REM sleep is specifically dedicated to processing repressed wishes. It nonetheless remains a powerful hermeneutic framework for exploring the personal meaning of dreams.

2. Analytical psychology: Jung and the message of the collective unconscious

Carl Gustav Jung proposed a radically different view. For him, dreams do not disguise — they communicate directly, but in the symbolic language of the unconscious. This language is made of archetypes: universal figures and motifs shared by all of humanity (the Mother, the Hero, the Shadow, the Self).

Unlike Freud, Jung saw the dream not as a disguised wish but as a compensation: the unconscious sends messages to rebalance consciousness when it has become too one-sided. Dreaming of a snake may thus signal that one is neglecting one’s instinctual dimension; dreaming of a journey may point to a need for transformation.

3. Neuroscientific theories: activate, consolidate, simulate

Twentieth- and twenty-first-century neuroscience has put forward several functional theories:

The activation-synthesis theory (Hobson & McCarley, 1977) suggests that dreams result from the brain’s attempt to “make sense” of random neural signals sent during REM sleep from the brainstem. Dreams would carry no symbolic message but rather an attempt at narrative from chaotic neural data.

The memory-consolidation theory: research such as that of Matthew Walker (Why We Sleep, 2017) shows that REM sleep plays a crucial role in consolidating emotional memories and learning. Dreams would be a “staging” of this memory processing, allowing the brain to integrate new experiences into existing networks.

The threat-simulation theory of Antti Revonsuo (2000) proposes that dreams have an evolutionary function: they would simulate threatening situations to prepare the psyche to face them. This would explain the frequency of nightmares and anxiety dreams during stressful periods.

4. The neuropsychoanalytic theory: Solms and the synthesis

The neuropsychologist Mark Solms attempted a synthesis between psychoanalytic and neuroscientific approaches. His research (2000) shows that dreams are not exclusively tied to REM sleep — they can occur in other sleep stages — and that it is mainly the dopaminergic reward system (the motivational “seeking system”) that is involved, rather than the brainstem alone. This is compatible with the Freudian idea of wish-fulfilment, but within a neurobiological frame.

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What all these theories have in common

Despite their differences, all these theories agree on a few points:

• Dreams are linked to real brain processes during sleep, not to mere neural “noise”.
• They intensely engage emotional regions of the brain (amygdala, hippocampus).
• They process the dreamer’s current experiences, emotions and concerns.
• Their content is never entirely random: it is shaped by what you live, feel and fear.

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How long do we dream each night?

Adult sleep is organised in cycles of about 90 minutes, alternating light sleep, deep sleep and REM sleep. We dream mainly during REM, which makes up about 20–25% of total sleep time. For 8 hours of sleep, that amounts to roughly 1.5 to 2 hours of dreaming per night — of which we usually remember only a few fragments.

Dream recall is helped by waking during or immediately after a REM phase: noting your dreams on waking in a journal (an ancient practice — the Greeks kept “dream diaries”) markedly improves the ability to retain them.

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Should we interpret every dream?

No. Some dreams are clearly tied to external stimuli (a noise, a temperature, a physiological need) or to ordinary memory consolidation of the day. Symbolic interpretation is relevant above all for recurring dreams, emotionally intense dreams, and dreams that keep “resonating” after waking — those deserve attention.

A reasonable approach: treat the dream as a metaphor for your inner state at the moment it occurs, without seeking literal predictions or supernatural revelations. Its value is introspective, not prophetic.