A new study shows that a nap can help you memorize images and solve problems, but only if you dream about them. Participants attempted to navigate through a virtual, 3-D maze. Half of them then took a 90-minute nap. Those who dreamed about the maze were 10 times better at negotiating the task than other nappers or subjects who didn't sleep at all. Let's say you really wanted to beat that maze—could you force yourself to dream about it?
Possibly. People are more likely to dream about the things they worry about the most during their waking hours, so the best way to induce a targeted dream is to truly believe that it's important. That's no help to sleep researchers, who often need their subjects to dream about trifles like a maze or brain teaser. They can try to force the issue by having people write notes about the desired dream subject right before going to sleep. They might also encourage the use of visualization or chanting exercises. (Early studies established that repeating a phrase to yourself works better than having someone whispering in your ear.)
No one knows whether these dream incubation techniques really work, though. In 1974, William Dement of Stanford tested 500 students to see if they could dream up a solution to a word problem. To facilitate the experiment, the test subjects were told to write down the problem and visualize the letters on the page as they went to bed. About 20 percent managed to dream about the problem, with seven actually solving it. A more recent study by Deirdre Barrett at Harvard asked student-subjects to solve a problem with more personal relevance—most of them chose a homework assignment or a relationship issue. Half of the students were able to have and remember a dream related to their problem.
The study released this week showed that some students began dreaming about the maze within a minute of falling asleep. The transition between wakefulness and sleep—it's called a hypnogogic state when you're falling asleep and a hypnopompic state while waking up—is poorly understood. Recent research suggests that drifting off is not a linear process in the brain (PDF) and that you alternate several times between wakefulness and sleep before finally succumbing. Researchers are forced to draw a somewhat arbitrary line between the two, usually requiring that certain brain waves disappear on an electroencephalogram for 30 seconds. Many researchers think you have the most control over your dreams—if that is the proper term for the disjointed hypnagogic images and sequences that flash through your mind—in the first minutes of sleep.
These images can be every bit as compelling as the REM- phase dreams that so interested Freud and Jung. August Kekule had one such vision of a snake biting its tail just before realizing that the structure of benzene was a ring rather than a straight chain. Mendeleev reportedly dreamt an image of the periodic table. (Some historians have questioned both Kekule's and Mendeleev's stories.) Many artists, like Samuel Taylor Coleridge, relied on the hypnogogic state for inspiration.
Got a question about today's news? Ask the Explainer.
Explainer thanks Deirdre Barrett, author of The Committee of Sleep: How Artists, Scientists, and Athletes Use Dreams for Creative Problem-Solving—and How You Can Too, Ernest Hartmann of Tufts University, Roger Knudson of Miami University, and Robert Stickgold of Beth Israel Deaconess Medical Center and Harvard Medical School.