Under construction.
Under construction. Nevit Dilmen/CC-BY-SA-3.0

New parents, amazed and overwhelmed, doddering and bleary-eyed, live for the solid nap, when that six-month-old, milk drunk and cried-out, finally nods off. It’s a chance to take a shower, fold the laundry, or quietly stare straight ahead. In those moments, something much more remarkable is taking place in the crib, where the baby’s sleeping brain is baking the day’s lessons into knowledge. According to a new study from the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, that process begins earlier than once thought, and depends (like a new parent’s peace of mind) on how long the nap lasts.

The researchers were examining how babies between six and eight months old learn to realize that words are not just noise, but actually refer to objects and ideas. In order to keep the babies’ existing knowledge from tainting the experiment, they used imaginary toy-like objects—which they called “Zusers” and “Bofels”—to assess the value of a midday nap. They found that non-nappers couldn’t tell if a newly introduced object should be called a Zuser or a Bofel. After a 30-minute nap, however, the adorable test subjects could distinguish between the right and wrong terms. And after 50 minutes, the researchers saw a brain pattern that until now has only been seen in older children and adults. Called the N400 component, it is a sign that the babies had formed a solid mental bond between word and object.

How to tell a Zuser from a Bofel.
How to tell a Zuser from a Bofel. MPI CBS

Babies process a lot and, as any parent who has heard a curse word unexpectedly repeated back to them can attest, they’re sponges. “But only during sleep, when the child’s brain is disconnected from the outer world, can it filter and save essential relations,” said study author Manuela Friedrich in a release. “Only during the interaction between awake exploration and ordering processes while sleeping can early cognitive and linguistic capabilities develop properly.”

All hail the power of the nap.