The latest study done by University of California at Berkeley suggests that the brain may need sleep to process short-term memories, creating "space" for new facts to be learned. In their experiment, 39 healthy adults were given a hard learning task in the morning - with broadly similar results, before half of them were sent for their siesta. When the tests were repeated, the nappers outperformed those who had carried on without sleep.
Dr Matthew Walker, who led the study, reported at the AAAS conference in San Diego, said, "Sleep not only rights the wrong of prolonged wakefulness, but, at a neurocognitive level, it moves you beyond where you were before you took a nap. It's as though the e-mail inbox in your hippocampus is full, and, until you sleep and clear out all those fact e-mails, you're not going to receive any more mail. It's just going to bounce until you sleep and move it into another folder."
However, Professor Derk-Jan Dijk, Director of the Surrey Sleep Research Centre said that there was no clear evidence that daytime napping offered a distinct advantage over sleeping just once over 24 hours. "The sleep-wake cycle is not as rigid as we might think - we have the capability to sleep in different ways, said Dijk to BBC.