"We found that -- for creative problems that you've already been working on -- the passage of time is enough to find solutions," first author Sara Mednick of the University of California, San Diego, and the VA San Diego Healthcare System said in a statement. "However, for new problems, only REM sleep enhances creativity."
It appears REM sleep helps achieve such solutions by stimulating associative networks, allowing the brain to make new and useful associations between unrelated ideas, Mednick said.
Using a creativity task called a Remote Associates Test, study participants were shown multiple groups of three words such as cookie, heart, sixteen, and asked to find a fourth word that can be associated to all three words -- sweet, in this instance. Participants were tested in the morning, and again in the afternoon, after either a nap with REM sleep, one without REM or a quiet rest period.
"Participants grouped by REM sleep, non-REM sleep and quiet rest were indistinguishable on measures of memory," first author Denise Cai, a California-San Diego graduate student, said in a statement.
"Although the quiet rest and non-REM sleep groups received the same prior exposure to the task, they displayed no improvement on the Remote Associates Test. Strikingly, however, the REM sleep group improved by almost 40 percent over their morning performances."
The findings were published in the Proceedings of the National Academy of Sciences.
