Statement of Significance
sleepiness
We evaluated the cognitive benefits of PSG (Polysomnography)-verified, nap durations of 10 min, 30 min, and 60 min for 5 to 240 min after awakening. Naps of any of these durations boosted positive mood and reduced self-reported sleepiness. Compared to wake, only naps of 30 min significantly benefitted recognition at 210 min post encoding. Improvements in speed of processing and vigilance showed less consistent patterns. Sleep macrostructure and memory benefits were not significantly associated. 30 min appears to be the duration to recommend for a mid-afternoon nap while provisioning ~10 min to fall asleep.