A nap during the day improves the brain's ability to absorb new facts, US scientists have claimed.
Volunteers who slept for 90 minutes during the day did better at cognitive tests than those who were kept awake.
The latest study, from the University of California at Berkeley, suggests that the brain may need sleep to process short-term memories, creating space for learning new facts.
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, BBC reported, adding that the results were presented at a conference in California.
Checks on brain electrical activity suggested that this process might be happening in a sleep phase between deep sleep, and dreaming sleep, called stage 2 non-rapid eye movement sleep, when fact-based memories are moved from temporary storage in the brain's hippocampus to another area called the pre-frontal cortex.
Dr Matthew Walker, who led the study, 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."
However, Professor Derk-Jan Dijk, the 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.