Key Points: The content of your dreams varies throughout the night. What you dream in the first half of nightly sleep corresponds with what happens in your life, in general—past, present, and future. The second half of the night contains dream content that is more personal, more emotional, more past-oriented.
Many researchers think that dreams offer a window into the functions of sleep, possibly revealing the types of information that is processed during sleep, including memories undergoing consolidation, emotional experiences being regulated, or rehearsing and responding to stressful life situations.
In support of this idea, the dreams reported from different stages of sleep seem to reflect the known functions of these sleep stages. For instance, Non-REM sleep has been shown to be important for certain types of learning, specifically strengthening memory for episodic events. Non-REM dreams likewise incorporate recent waking-life experiences more obviously or directly than REM dreams. REM sleep, on the other hand, seems more important for processes of emotion regulation, and broadening associative connections between memories. And REM dreams are more emotional and bizarre than non-REM dreams.
In a recent study, researchers wanted to look at whether dream content also changes depending on the time of night, possibly reflecting a time-course of sleep function that occurs over a night of sleep. Specifically, the researchers were interested in whether and when dreams are more directly related to waking life experiences, compared to when they are more remotely or metaphorically related to waking life emotions or personal concerns.
The home sleep study had 68 participants.
On two separate nights, participants completed four awakenings (waking up every two hours during the night) to report their dream content. These reports were recorded, and in the morning the participants listened to their dream reports and completed a questionnaire in response to each dream.
The questions assessed whether the dream content was related to waking life experiences.
It first asked if the dream is related to waking life in the present (in the past month), the recent past (1 month to 1 year ago), the distant past (over a year ago), or the future.
It then asked if the dream was related to waking life in general, literally, or metaphorically.
Lastly, participants were asked whether the dream was emotionally related to current waking life, whether the dream was bizarre, emotionally intense, negative or positive, stressful, and finally, important.
The primary analysis looked at whether dreams from early night differed from late-night dreams.
In fact, early-night dreams were more related to waking life (from the present, recent past, future, or literally similar) than late-night dreams, whereas late-night dreams were more emotional, important, bizarre, metaphorical, and related to the distant past.
Here's one example of an early-night dream:
“I was at work. We had orders coming in. I was cataloguing…I was replacing lots of cutters. There wasn’t very much time, and there was some pressure to get the cutters replaced.”
And an example of a late-night dream:
“It’s a big party with exams, the exams were actually happening at the party, people were getting called into a room one by one on their own. My partner turned up with his stupid car. Everyone was in sort of modern Victorian dress. Time was dancing, yeah time was actually dancing, not time spent dancing. The teapot from Beauty and the Beast was there. [Person] was there was well. I was happy. We were all in modern Victorian dress. Fireworks.”
Overall, the authors conclude that dream content varies through a night of sleep. Dreams from the first four hours of sleep were more related to waking life, from the recent past to the present to the anticipated future. Dreams from the second four hours of sleep were more emotionally intense, personally important, and more bizarre, metaphorical, and related to the distant past.
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Malinowski, J. E., & Horton, C. L. (2021). Dreams reflect nocturnal cognitive processes: Early-night dreams are more continuous with waking life, and late-night dreams are more emotional and hyperassociative. Consciousness and Cognition, 88, 103071.