In a study of 40 preschoolers, napping aided children's ability to recall information they had been taught earlier that day. Children recalled 75 percent of the matches accurately after a nap, versus 65 percent when they skipped a nap.
"There was very little telling us about naps, the physiology of them— nothing to say they really had a function," said Rebecca Spencer, an associate professor of psychology and neuroscience at UMass Amherst. "I think policy-wise, teachers, in order to make the most of the research, need to know more about how to promote napping in the classroom."
In the study, published in the Proceedings of the National Academy of Sciences on Monday, researchers taught children a game that resembled the popular game Memory, in which children have to match images with cards laid out in a grid pattern. They chose the memory task because it requires many of the basic skills preschoolers utilize when attempting other types of learning, such as learning the alphabet.
After playing the game, the children either napped or stayed awake. Later that afternoon, they were tested again, to see how much they remembered from the morning session.
A week later, the experiment was flipped. The children who had napped in the first experiment were kept awake, and those who had not slept.
The difference was clear, Spencer said, with those who napped recalling 10 percent more of the locations of the cards than when they did not nap. The researchers even checked the children the next day to see if overnight sleep had an effect, and found no difference in performance.
Spencer then brought some of the children into the laboratory and measured their brain activity while they slept. To her surprise, she found that the kids were not experiencing REM sleep associated with dreaming. She did, however, detect bursts of brain activity called sleep spindles that were associated with the most productive naps—the ones that helped children retain memory. In other studies, that type of brain activity had been associated with moments when the brain was most plastic and adaptable.
The study clearly suggests that napping may be a potent part of the learning process, but there was an interesting anomaly. Among children who were not habitual nappers, sleeping did not have an effect. That suggests to Spencer that as the children's brains mature, perhaps they do not depend on the nap to consolidate their memories.
Image: Napping preschooler, via Shutterstock