At some point the time has come: small children no longer sleep during the day – often to the chagrin of their parents.
However, the point at which they break this habit varies greatly.
Some children are still sleeping regularly during the day as young as four or five, while others are no longer taking a daily nap by the age of three.
What is the reason for this non-simultaneity?
Why do some children take naps longer than other children of the same age?
The lack of simultaneity obviously has to do with the development of the brain and its storage abilities, not with age itself.
Rebecca Spencer from the University of Massachusetts in Amherst and Tracy Riggins from the University of Maryland in College Park assume that children's need for a nap during the day is linked to the individual developmental level of the hippocampus, a special brain region.
Young children give up their naps when their hippocampus is ready.
The hippocampus is the short-term storage facility for memories.
From there, the memory content is passed on to the cerebral cortex, where large amounts of this initially sketchy information are stored over the long term, categorized and converted into knowledge.
The shift from the hippocampus to the cerebral cortex occurs primarily during sleep.
Spencer and Riggins were able to show some time ago that small children build up sleep pressure in the form of special brain waves before they take a nap.
Daytime sleep promotes learning
The two scientists assume that this sleep pressure is caused by an overload of the immature hippocampus.
The more impressions small children absorb, the faster the storage capacity of their hippocampus, which is not yet fully developed, is exhausted.
Without an emptying in the direction of the cerebral cortex, many other impressions and thus also much learning content would be lost.
Napping helps children free up their hippocampus for new memories.
Basically, it's the same as with small and large buckets, the scientists write in a statement.
A small bucket overflows faster than a large bucket and therefore has to be emptied more quickly.
If daytime napping helps toddlers protect their immature hippocampus from overload and promotes learning, why don't they stick with the habit much longer?
At no time in their lives do people have to take in so many impressions and master so many new tasks as in early childhood - and with a brain that still has to learn to learn.
Nevertheless, getting out of the daily nap is part of the normal development of a child.
By the time they are five years old, most of them are gone.
With a mature hippocampus, children no longer need a nap because they can store their impressions until they go to sleep.
You keep everything until the evening.
This means that daytime sleep is no longer so important for learning.
The researchers had shown a while ago that the hippocampus is immature in children who still need a nap than in children who have already given up this habit.
However, in their publication in the "Proceedings" of the American National Academy of Sciences, both women also make it clear that their data are of a correlative nature.
They cannot support their thesis that the degree of maturation of the hippocampus is the cause for the end of the afternoon nap with hard causal data.
They have no clear evidence for this and therefore also plead for further investigations.
Should we now offer small children a nap, even if they make no attempt to sleep?
The scientists have a clear opinion on this.
"Some still need the nap, some may not need it anymore, but if they still sleep, their learning will benefit," says Rebecca Spencer.
She advocates protecting the nap for those who still need it, and thinks little of the fact that many kindergartens and pre-school institutions only focus on learning and no longer offer naps.
Because one doesn't work without the other.