Mid-day naps may help preschool children improve their learning efficiency, U.S. researchers said Monday.

Researchers from the University of Massachusetts Amherst said little is known about the value of naps in young children and some U.S. preschool programs have begun to eliminate naps to increase teaching time.

Against this backdrop, the researchers recruited 40 preschool children and taught them a visual-spatial task, in which children see a grid of pictures and have to remember where different pictures are located on the grid.

Children learned the task in the morning, and performed a memory test immediately afterward and then again in the afternoon, with or without a mid-day nap.

While the children performed at similar levels immediately after learning, those who napped performed significantly better both in the afternoon and the next day than those who did not nap, the researchers reported in the journal Proceedings of the National Academy of Sciences.

"That means that when they miss a nap, the child cannot recover this benefit of sleep with their overnight sleep," they wrote in their paper.

To explore the effect of sleep stages and whether memories were actively processed during the nap, the researchers recruited an additional 14 preschoolers who came to a sleep lab and had polysomnography, a record of biophysiological changes, during their average 73-minute naps.

The researchers noted a correlation between sleep spindle density which is activity associated with integrating new information, and the memory benefit of sleep during the nap.

"Essentially we are the first to report evidence that naps are important for preschool children," lead author Rebecca Spencer, research psychologist of the university, said in a statement. "Our study shows that naps help the kids better remember what they are learning in preschool."

The researchers urged preschools to develop napping guidelines and further research on how to protect and promote naptime for young children to enhance their learning.

Source: Xinhuanet