Researchers agree that optimum napping time is between fifteen minutes and two hours. During a nap that’s shorter than fifteen minutes, you never enter the most restful phase of sleep. But if you sleep for over two hours, you might not be able to fall asleep when you turn in for the night.
Cognitive neuroscientists at Washington University in St. Louis have investigated the relationship between mood and cognitive performance by showing subjects ten-minute clips from both classic horror films and prime-time television comedies.