“We’re familiar with the benefits of sleep,” said Amelia Goodfellow, a student assistant in sleep and stress at the UC Davis health center. “We’re not as familiar with the impacts or positive effects of napping, which are very similar.” For students, the benefits of increased productivity and concentration will translate to better academic performance, the presenters argued — even though they acknowledge having no data to back that up.
However, research has repeatedly shown that when supplementing 7-9 hours of sleep, 20-30 minute naps do offer these benefits, particularly when taken between the hours of 10 to 11 a.m. or 2 to 4 p.m., when human sleep rhythms trigger a natural slump with grogginess and lack of focus.
http://www.insidehighered.com/news/2011/06/03/california_davis_health_educators_urge_students_to_nap