AAAS: A nap after lunch boosts the brain's learning capacity - Telegraph

Researchers have found that sleeping for an hour in the afternoon boosts brain power and dramatically increases its ability to learn new facts and tasks

On the other hand, the more hours we spend awake, the more sluggish our minds become and the less able to absorb new information.

"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," said Professor Matthew Walker, who led the study at the University of California. - AAAS: A nap after lunch boosts the brain's learning capacity
Nap 'boosts' brain learning power - BBC News
Afternoon Nap Might Make You Smarter - BusinessWeek
New Zealand Herald - The Press Association - Health.com