Why do we dream?
General information only. This article explains the basics and is not medical advice. For anything about your own health, talk to a doctor or other qualified professional.
Quick answer
Scientists don’t know for sure why we dream. Leading theories say dreams help us process emotions, sort and store memories, and rehearse responses to threats. Most vivid dreams happen during REM (rapid eye movement) sleep, when the brain is nearly as active as when we’re awake.
Everyone dreams, even people who say they don’t. Most adults have four to six dream periods a night, adding up to around two hours, but we forget almost all of them within minutes of waking.
The main theories
| Theory | What it says |
|---|---|
| Emotional processing | Dreams replay emotional experiences in a safer setting, which may soften painful memories |
| Memory consolidation | The sleeping brain sorts the day’s information, keeping what matters and linking it to older memories |
| Threat simulation | Dreams let us practice escaping danger, which may explain why chases and falls are so common |
| Activation-synthesis | Dreams are the brain’s attempt to make a story out of random signals during sleep |
These ideas don’t rule each other out. Dreams may do several jobs at once.
What happens in REM sleep
Sleep runs in cycles of about 90 minutes. In REM sleep, the eyes dart around, breathing becomes irregular and brain activity rises. At the same time, most muscles are temporarily paralyzed, which stops us from acting out our dreams. REM periods get longer toward morning, which is why the dreams you remember usually happen just before waking.
Why do we forget dreams?
During sleep, the brain releases less of the chemicals involved in forming new memories. Unless you wake up during or right after a dream, it usually fades. Keeping a dream journal by your bed and writing straight after waking helps you remember more.
Lucid dreams and nightmares
In a lucid dream, you realize you’re dreaming and can sometimes control what happens. Nightmares are common, especially in children, and are often linked to stress. Frequent, distressing nightmares are worth discussing with a doctor.
Dreams depend on good sleep. See why sleep is important and how to sleep better.
Still curious?
Jump to a random question from the archive.