Dreams reflect nocturnal cognitive processes: Early-night dreams are more continuous with waking life, and late-night dreams are more emotional and hyperassociative.

Dreams from the early night are more clearly connected to waking-life activities, while late-night dreams are more emotional, important, varied in time orientation, and hyperassociative. These differences align with known sleep-stage functions: non-REM sleep supports episodic memory consolidation and REM sleep supports emotional regulation and creativity. The findings suggest that dream content reflects underlying sleep processes such as memory consolidation, emotion-processing, and creativity across the night.

Study at a glance

Abstract

Contributions of specific sleep stages to cognitive processes are increasingly understood. Non-REM sleep is particularly implicated in episodic memory consolidation, whilst REM sleep preferentially consolidates and regulates emotional information, and gives rise to creativity and insight. Dream content reflects these processes: non-REM dreams are more likely to picture episodic memories, whereas REM dreams are more emotional and bizarre. However, across-the-night differences in the memory sources of dream content, as opposed to sleep stage differences, are less well understood. In the present study, 68 participants were awoken from sleep in the early and late night and recorded their dreams and waking-life activities. Early-night dreams were more clearly relatable to (or continuous with) waking life than late-night dreams. Late-night dreams were more emotional-important, more time orientation varied, and more hyperassociative, than early-night dreams. These dream content differences may underlie the mental content that accompanies sleep processes like memory consolidation, emotion-processing, and creativity.