Adults dream for about two hours a night, on average-that’s one twelfth of their lives, adding up to more than six years of dreaming during an 80-year life. Humans have long wondered why we dream and whether it serves a purpose-perhaps as a way for us to communicate with the gods, predict the future, or represent our repressed feelings. There are scores of theories.
The truth is that nobody knows for sure why we dream or whether dreams are of any use, but many functions have been proposed. For instance, studies have found that rapid eye movement (REM) sleep (the dreaming stage), in particular, may help people consolidate and reorganize memories so that they can perform cognitive activities better.
Except for people with certain brain abnormalities, everyone has REM sleep, during which dreams occur. Some people remember their dreams regularly, without effort, but most of us forget them quickly-or seldom remember them at all unless we are awakened in the middle of one. The brain processes that store memories are largely suppressed during sleep. You’re more likely to recall dreams that are more coherent as well as those that are vivid and cause greater arousal.
People who don’t remember their dreams may think they don’t dream, but they almost certainly do. That was the conclusion of a French study in the Journal of Sleep Research in 2015, which found that when people who claimed they never dreamed were monitored during sleep, their movements and other behavior strongly indicated they were dreaming during REM sleep.