Abstract: Napping not only can be a countermeasure to the afternoon circadian nadir, but has the potential to improve mood, alertness, and performance in the afternoon. However, habitual napping behavior in young adults is not to compensate for poor sleep on the preceding night. More specially, a short-term nap was long enough to lead to benefits, but short enough to avoid post-nap grogginess. Moreover, research has consistently shown that nap can also benefit to memory consolidation. Declarative memory was consolidated in slow wave sleep (SWS) during daytime naps, and the consolidation was associated with stage 2 sleep and spindles. Furthermore, stage 2 sleep and spindles may be particularly important for the efficient consolidation of motor skill memory. The mechanism of memory consolidation during naps might be the direction of further studies

Key words: nap, habitual nap, short-term nap, memory consolidation