Toddlers nap a lot — and then they don’t. It’s a matter of brain science.
Why do some preschoolers refuse naps while others have a meltdown without an afternoon snooze? Researchers suspect it may have to do with a memory-related part of the brain.
While young children all need a lot of sleep, they vary widely in when they stop napping during the day: Some leave naps behind by the time they are 3, while many others happily take an afternoon nap through age 5 or even longer.
In a special sleep issue of Proceedings of the National Academy of Sciences, Rebecca Spencer, a professor of psychological and brain sciences at the University of Massachusetts Amherst, and colleague Tracy Riggins propose a theory on why and when youngsters stop napping: It may be dependent on a brain structure called the hippocampus.
The hippocampus plays a major role in memory processing and learning. Spencer and Riggins hypothesize that the maturity of the hippocampus, rather than age, may be a key driver of transitioning out of napping.
The hippocampus is important in forming and stabilizing memories of new information, before they are passed along to the brain’s long-term storage. Sleep, in adults and children alike, helps the hippocampus do its job.
But during early childhood, the hippocampus is rapidly developing. The immature hippocampus is analogous to a small bucket that can only hold so much before it overflows, Spencer said. So young children need that afternoon nap to help the hippocampus process memories — essentially emptying the bucket.
Studies support the value of allowing preschoolers to nap after learning new information. In a
2020 study, Spencer and her colleagues found that youngsters who napped after story time were better able to recall the story’s sequence of events than peers who stayed awake.
As the hippocampus matures, so does its capacity, and the drive to nap abates, Spencer and Riggins say. So children may transition out of napping based on hippocampus development. But that does not mean something is wrong with the hippocampus of a child who still naps at age 5.