Babies Use Sleep to Make Sense of Words
Teens aren’t the only ones who sleep in order to learn. A new study by scientists at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS), has found that sleep accelerates a baby’s language development, allowing children as young as six months to successfully associate meanings with words.
The scientists studied this relationship by introducing 6- to 8-month-old babies to objects given fictitious names like “Bofel” or “Zuser.” (Researchers called object by fantasy names so the children wouldn’t be influenced by any pre-existing vocabulary for objects.) Objects that were different only in form or colour were still called “Bofel” or “Zuser,” just as different species of cats are still called cats.
Initially, the babies failed to associate a Bofel with the word “Bofel,” even if it was quite similar to a Bofel they had seen before. However, the results changed once the babies were allowed to take a midday nap. The children who had slept could correctly identify an object by its correct, invented name; children who had not slept still could not.
Furthermore, the amount of time a baby had slept made a difference to their learning. MRI scans showed babies who had slept for 30 minutes formed an association between a visual stimulus and a sound, a connection babies are typically able to make by three months. These babies perceived the word as a random sound with no meaning.
However, babies who had slept for 50 minutes showed on MRI a brain reaction indicative of processing unintelligible words, sentences and images into meaning — previously believed to occur only in older children and adults. These children had learned the meanings of the words they were shown in the experiment.
“Our results demonstrate that children hold real word meanings in their long-term memory much earlier than assumed,” said Angela D. Friederici, director at MPI CBS and senior author of the underlying study. “Although the brain structures relevant for this type of memory are not fully matured, they can already be used to a distinguishable extent.”
This study adds to the growing body of evidence that sleep is integral to the learning process. The second stage of sleep, in particular, seems to play a key role in developing a baby’s vocabulary.
Typically, development of this type of memory takes months, but during sleep the process accelerates to mere minutes.
“Only during the interaction between awake exploration and ordering processes while sleeping can early cognitive and linguistic capabilities develop properly,” said study leader Manuela Friedrich said.