Researchers have seen evidence that a daytime nap can help preschoolers learn.
The research involved 40 children ages 3 to 5, who were shown a grid with pictures of items like a cat or an umbrella.
They were tested later on how well they remembered the location of the items. And after a nap, their accuracy improved.
Researchers from the University of Massachusetts say grown-ups shouldn't cut out the naps when they try to cram more learning activities into a preschooler's day.
The research is in the Proceedings of the National Academy of Sciences.