Napping helps preschoolers learn

A great deal of research supports the claim that sleep benefits cognitive function in adults. However, evidence-based research on how much sleep children need for healthy cognitive development is scarce. Despite this lack of clarity, certain facts appear consistent across studies. First, recommendations for sleep need have fluctuated throughout history, with children always sleeping less than the experts recommend. Second, children are sleeping less now than ever before (1). Without targeted research on the impact of sleep on cognitive development, experts are unable to make informed recommendations for school start times, bedtimes, and nap times. Napping is the core of infant sleep and remains an essential part of many children’s sleep diet until they begin kindergarten. PNAS now presents a unique study by Kurdziel et al. to illuminate what may be one of the primary functions of daytime napping in preschool-aged children: memory consolidation (2). Preschoolers were trained in the morning on a visuospatial memory task similar to the game “Memory,” and then either napped or played quietly without napping. Recall was tested 30 min after the nap and the following morning, 24 h posttraining. The authors found that when children napped they showed greater conservation of knowledge both in the postnap and 24-h recall conditions, whereas there was significant long-term forgetting when they did not nap. These data are unique in clearly indicating napping as a valuable resource for memory consolidation in preschool-aged children. Numerous studies demonstrate positive effects of sleep on memory consolidation in adults (3). Although seldom researched, similar results have been shown across younger age groups. Infants who nap within 4 h of training on an artificial language show generalization of language rules compared with infants who stayed awake (4). On a visuospatial task similar to the one used by Kurdziel et al. (2), performance improvement …