Most parents know it's going to be a rough evening if their preschooler skipped their regular nap. But those naps may help their children in other ways besides behavior.
A recent study found that preschoolers' naps may help improve their learning skills.
The researchers found that naps improved young children's ability to process memory, at least if the children regularly got naps.
This benefit of processing memory could not be made up during night sleep if a regular nap was missed, the researchers found.
Preschoolers performed better on a memory test after their nap than if they had been deprived of their nap.
This study, led by Laura Kurdziel, a doctoral student in the Neuroscience and Behavior Program at the University of Massachusetts in Amherst, looked for links between preschoolers' regular naps and learning.
The researchers studied 40 preschool children, including 31 girls, who ranged from 3 to 5 years old.
The researchers collected information from the parents in questionnaires about the children's nighttime sleep habits, and the 17 children who regularly napped (at least five days a week) were noted.
The 10 children who were determined not to be regular nappers were those who napped less than two days a week.
One morning at preschool, the children participated in a memory task similar to a memory card game.
The children repeated the task until they got either 7 out of 9 correct items or 9 out of 12 correct items (matching a photo to where the card showing that photo was).
On average, it took the children two to three attempts to reach the minimum correct matches.
A few hours later, the children laid down for their nap from 1 to 3 pm.
This exercise was conducted twice with the second time occurring about one to three weeks later.
During one of the experiments, some children were kept awake with quiet activities during nap time while the others were encouraged to sleep.
Then, during the second experiment, the conditions were flipped: the children who had slept before were kept awake and the others were encouraged to sleep. The naps lasted an average of 77 minutes.
After the naps, the children completed the memory tests again. Many of the children (those who were not absent) completed the memory tests the following morning as well.
The children had all performed with similar overall results during the first memory test (before the nap).
After naptime, however, the children who had napped had significantly better scores on one of the memory tasks than those who were kept awake.
The nappers got 75 percent of the tasks correct while those kept awake got 65 percent correct.
However, the bigger benefit in learning and memory among the children who took naps was for those who regularly napped at least five days a week.
The children who did not regularly take naps did not appear to benefit from the nap in terms of learning and memory skills.
"The present results illustrate a benefit of mid-day naps on learning in the preschool classroom," the researchers wrote. "Following a nap, children recalled 10 percent more of the spatial locations than when they had been kept awake during the nap opportunity."
The researchers said the differences in performance when the kids did not nap did not appear related to poor attention or alertness because the learning benefit remained the next day for children who had napped.
"Thus, the negative effects of nap-deprivation on memory consolidation cannot be reversed with overnight sleep," the researchers wrote.
William Kohler, MD, the medical director of the Florida Sleep Institute in Spring Hill, Florida, said that children's brains mature at different rates.
"There are some children who will significantly benefit from a nap," he said. "Sleep improves cognition and is important for memory development."
He said that there are certain children who will have greater difficulties with cognitive activities if they are denied a nap, so it is important that those children have the opportunity to nap even if others their age do not require it.
"Most children by age 5 don't need to nap and that's one reason in kindergarten, naps are going out of favor because studies have shown that the children don't need the nap or don't take the nap if given the opportunity to do so," Dr. Kohler said.
"But there are children who will benefit from it, and it's important to recognize that to maximize cognitive development, these children need to be given the opportunity to have that nap available," he said.
This study was published September 23 in the Proceedings of the National Academy of Sciences. The research was funded by the National Institutes of Health and a Commonwealth College Honors Research Grant. No disclosures were reported.