The Science of “Sleeping on It”

Experts say if you want to harness sleep’s problem-solving powers to the fullest, think about your dilemma just before bed

Thomas Edison appreciated a good midday snooze, and the great inventor’s quirky napping routine has become legend. By most accounts, Edison liked to settle into a comfortable chair with a ball bearing in each hand, and metal pie pans at his feet. After dozing for a while, Edison’s hands would relax and the ball bearings would clatter into the pans, waking him up.

All this was not without purpose. Upon waking, Edison would immediately write down whatever thoughts came to him. His belief was that many of his most inspired ideas came to him in the dozy, dreamy moments that precede deep sleep, and his napping program was designed to harness more of this creative energy. A new study in the journal Psychological Science suggests Edison was onto something.

For the study, researchers at Northwestern University presented people with a series of carefully designed, sneakily tricky puzzles. The participants had two minutes to try to solve each puzzle. During those two minutes, a unique sound clip would play on a loop in the background. (New puzzle, new sound clip.)

After this first stage of the experiment, which always took place in the early evening, the people went home with some specialized equipment. The equipment monitored their sleep and, as they slept, played back some of the same sound clips they’d heard while attempting to complete the puzzles in the lab. The next morning, the people returned to the lab and got another crack at the puzzles they’d been unable to solve the night before. Their solve-rate improved across the board, but they were especially adept at solving the puzzles that corresponded with sound clips they’d heard while sleeping. They figured out the answers to 32% of the sleep-cued puzzles, compared to 21% of the un-cued puzzles.

“There was this idea that during sleep the brain is resting, but now we know there’s a lot of important work being done,” says Mark Beeman, a professor of psychology at Northwestern. During sleep, the brain sorts, consolidates, and stores new information. It also “rehearses” recent memories, he says. This rehearsal seems to help the brain identify meaningful patterns while discarding unhelpful “background noise” — all of which could aid in problem-solving, he explains. Playing sound clips cued to certain puzzles appeared to facilitate this form of helpful rehearsal.

“This research adds to a growing literature suggesting that sleep can reorganize information to facilitate problem-solving,” says Kristin Sanders, first author of the study and a doctoral student at Northwestern. “It also suggests that replay of the problem memory during sleep is critical for this reorganization.”


reat minds have long recognized the strange, elucidating power of “sleeping on it.” The writer John Steinbeck once mused that “a problem difficult at night is resolved in the morning after the committee of sleep has worked on it.” And there are countless anecdotes about artists, scientists, and philosophers who experienced bursts of inspiration after sleeping.

Research supports a lot of this anecdotal evidence. A 1992 study in the journal Psychological Research found that depriving people of sleep for one night reduced their problem-solving ability much more significantly than it impaired other high-level cognitive processes. And some researchers have speculated that dreaming may have evolved, in part, to facilitate problem-solving. “Dreams are thinking or problem-solving in a different biochemical state of that of waking,” writes the Harvard psychologist Deirdre Barrett in The New Science of Dreaming. Barrett makes the case that, from the perspective of evolution and natural selection, any function of the brain must have some utility. And the utility of dreams may be to help the brain dissect a problem in different and helpful ways.

“Sleep may help your brain come up with new solutions because that’s a time when it’s not bogged down with 20 other tasks.”

Meanwhile, more research bears out the idea that, during sleep, the brain replays ideas or problems it had grappled with during the day. While people tend to recall those dreams that disturb or dazzle them, studies that utilize dream journals have revealed that, for the most part, people dream about the kinds of activities or interactions they have during their waking hours. And a 2010 study in the journal Sleep found that during those dozy periods when a person is just drifting off to sleep or about to wake up, the brain often replays imagery related to new experiences. When a person’s conscious mind punches out during periods of sleep, some other “unconscious” work seems to take place, Beeman says.


order to harness sleep’s problem-solving powers to the fullest, he says it may help to think about your dilemma just before bed. This may encourage your sleeping brain to go to work on it. If you’re really up against a wall and desperate for new ideas or insights, his research indicates that playing some type of sound clip — crashing waves, say, or the sound of rain — both while you think about your problem and while you sleep may further incite your brain to tackle the problem.

It may also be important to devote time to thinking about your challenge during the morning hours. Edison was in a hurry to write down his post-nap thoughts because he realized they might fade away as other preoccupations snared his attention. Allowing your brain a little time each morning to revisit and review what bedeviled you the night before may yield helpful insights.

“Sleep may help your brain come up with new solutions because that’s a time when it’s not bogged down with 20 other tasks,” Beeman says. Subjecting your brain to a little less bogging during your waking hours may likewise yield some unexpected benefits.

All Rights Reserved for Markham Heid

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