JOIN USResearchers led by Sara C Mednick, an assistant professor of psychiatry at the University of California, San Diego, gave 77 volunteers word-association tests under three before-and-after conditions: spending a day without a nap, napping without REM sleep and napping with REM sleep. Just spending the day away from the problem improved performance; people who stayed awake did a little better on the 5 pm session than they had done on the 9 am test. Taking a nap without REM sleep also led to slightly better results. But a nap that included REM sleep resulted in nearly a 40 percent improvement over the pre-nap performance.
The study, published in The Proceedings of the National Academy of Sciences, found that those who had REM sleep took longer naps than those who napped without REM, but there was no correlation between total sleep time and improved performance. Only REM sleep helped.
"Dreams are fanciful," Dr Mednick said. "They incorporate strange ideas that you would never have put together in waking life. In REM sleep, it becomes more likely that ideas might come together in a solution."
Kids and self-control
A simple five-minute behavioural test for children entering kindergarten can predict significant gains in mathematics skills over the course of the year, researchers have found. Claire Cameron Ponitz, a research associate at the University of Virginia, led a group that tested 343 children with the Head-Toes-Knees-Shoulders task, in which children perform the opposite of an oral command (for example, the correct response for "touch your toes" would be to touch your head). Higher scores, the researchers write in the May issue of Developmental Psychology, indicate a greater ability to control and direct one's own behaviour, an ability essential for success in the structured environment of a kindergarten class.