Here's more evidence that sleep, including napping, can make you smarter.

Dreaming may improve memory, boost creativity, and help you better plan for the future, new research suggests.

In a recent study, people who took naps featuring REM sleep—in which dreams are most vivid—performed better on creativity-oriented word problems. That is, the REM, or rapid eye movement, sleep helped people combine ideas in new ways, according to psychiatrist Sara Mednick, who led the study.

Part of the experiment's morning round involved a word-analogy test, similar to some SAT problems. For example, given "chips: salty::candy:_____" the answer would have been "sweet."

At midday, after the first round, the subjects were given a 90-minute rest period, during which they were monitored.

Some participants took naps with REM sleep, which typically begins more than an hour after a person falls asleep. Others took an REM-less nap. A third group rested quietly but didn't sleep.

There was a second round of tests in the afternoon. In a typical second-round test, participants were asked to guess what single word is associated with three seemingly unrelated words. For example, given "cookie," "heart," and "sixteen," the answer would have been "sweet." The correct answers to many of the second-round questions were the same as the solutions to analogy questions from round one.

On the second-round questions whose answers matched first-round answers—for example, "sweet" and "sweet"—the REM nappers improved their performances by 40 percent. Non-REM nappers and the non-nappers showed no improvement on these problems, said Mednick, of the University of California, San Diego, who presented her findings Friday in San Diego at the American Psychological Association's annual convention.

That means that REM sleep improved participants' ability to see connections among seemingly unrelated things: the answers from the first-round analogy problems and the three words in each round-two association test, she said.

Mednick noted that all groups remembered the morning's answers equally well—proving that the second round wasn't just testing nappers' memorization abilities. Instead, REM "plays a role in helping people detach their memory of that word from being able to use that word in other contexts," she said.

Sleep Helps Turn Memories Into Predictions?

Boosted by deep sleep, an improved memory may have yet one more benefit: helping you imagine—and better plan for—the future.

"When you imagine future events, you're recombining aspects of experiences that have actually occurred," Harvard psychiatrist Daniel Schacter, whose research was separate from Mednick's, told National Geographic News.

Schacter, who also presented Friday at the psychology convention, has found that the same areas in the brain that handle memory, such as the hippocampus, show increased activity when subjects are asked to imagine future events (interactive brain map).

Could REM sleep turn you into a crystal ball?