Got a Problem? Sleep on It

Remember the last time you noodled over a problem but didn't arrive at a suitable solution? Chances are, you put it out of your mind and told yourself you'd sleep on it, only to wake the next day with the answer.

You may not have realized you were employing a scientifically studied problem solving technique. Sleep researchers and other scientists have studied how sleep-or the lack of it-affects cognitive functioning and other measures of health and quality of life. Although they suspected that sleep improved problem solving, they were not clear on the specific mechanism.

The results of a recent study shed new light on the subject. The researchers found that REM (Rapid Eye Movement) sleep enhances integration of unassociated information used for problem solving. They compared REM sleep, non-REM (NREM) sleep, and wakefulness on memory and associative processing in creative problem solving.

The quantity of sleep was not the critical factor; the quality of sleep was. When subjects were exposed (primed) with new information prior to taking a nap, they were better able to solve the problem after waking.

We cycle between REM and NREM sleep every 90 minutes. Both are critical, although we only spend about one quarter of our sleep time in REM sleep. This is when we dream. REM sleep also provides energy for our brain and our body.

REM sleep is an opportunity for our brain to store new information into long-term memory through the process of sleep spindles: one to two second burst of brain waves that rapidly wax and wane at a strong frequency. During sleep spindles, our brain replenishes neurotransmitters that organize neural networks we need for learning, performance, and problem solving.

People who sleep less than six hours may block sleep spindles. Lack of sufficient sleep dramatically impairs memory and concentration and increases stress hormones that disrupt metabolism, leaving us unable to make decisions.

Effective problem solving requires, in part, taking information we already have and putting it together in new ways. The theory of incubation states that the solution to a problem will emerge spontaneously after we take a break from working on it. The researchers in this current study found, however, that taking a break by sleeping isn't enough on its own to enhance problem solving. We need REM sleep to reorganize or rearrange information into new patterns that provide solutions.

So, the next time you are struggling with a problem or making a decision, sleep on it!


Cai, Denise J., Mednick, Sarnoff A., Harrison, Elizabeth M., Kanady, Jennifer C., and Mednick, Sara C. "EM, not incubation, improves creativity by priming associative networks." PNAS. Web.

American Psychological Association. "More sleep would make most Americans happier, healthier and safer." Web. 2 May 2004.

National Sleep Foundation. "Let sleep work for you." Web.

Greer, Mark. "Strengthen your brain by resting it." Monitor 35(7) (2004). Web.