New borns learn vowels while sleeping
Brain scans reveal that learning lasts.
"Newborns spend most of their day asleep, but their minds are still active, says
a new study that shows they can learn to tell the difference between various spoken
sounds while they snooze.
Researchers suggest they're able to do this because of a pattern of sleep unique
to infants.
"It's been suspected that infants could learn in their sleep, but it's nice to have
a very clear demonstration," says Janet F. Werker, an expert on childhood language
acquisition at the University of British Columbia in Vancouver. The study appears
in tomorrow's issue of the journal Nature.
Lead investigator Marie Cheour is the head of the Laboratory of Language and the
Developing Brain Laboratory at the University of Turku in Finland. She and her colleagues
enlisted the help of 15 healthy, full-term newborns still in the hospital following
their birth.
Cheour's team brought the babies to their laboratory during the evening, where they
hooked up each infant to an electroencephalograph (EEG), a noninvasive device used
to measure brain waves.
Over the course of the evening, while the babies were asleep, the researchers played
standard and slightly deviated vowel sounds while the EEG recorded their brain waves.
When the babies woke up, they received formula and whatever attention they needed,
and the sounds began again once they went back to sleep.
That night, half of the infants were returned to their mothers, while the remaining
children stayed for the entire evening.
The next morning, all of the babies again were part of the same EEG experiment.
From the EEG readings, Cheour's team could determine whether the babies' brains
were discriminating between different speech sounds.
"We learned that all the children whom we trained to discriminate between those
speech sounds really did learn it," says Cheour. "Those who spent the night with
their mothers didn't."
To find out if the effects lasted, the babies returned to the laboratory one day
later and repeated the test.
"Even the next evening, the children continued to be able to discriminate those
speech sounds," says Cheour. "I was surprised that it happened so quickly."
Although it's not clear when children stop learning while sleeping, Cheour says
it's likely they lose the ability very quickly.
"Infant sleep is very different from ours," says Cheour, explaining that they spend
much more time in the active, dream-stage sleep that has been linked to brain maturation
and development.
It's not yet clear whether infants can learn to distinguish between other speech
sounds, such as consonants or even musical notes, says Cheour.
Werker says states of consciousness differ between infants and older children or
adults.
"We know that learning is state-dependent, and that infants are less able to take
in information when they're fussy and crying," she says. "Very young infants are
not in a quiet, alert state very much of the time. If that were the only time that
they could learn, they wouldn't have much opportunity to be learning about the world
around them."
Werker adds this ability lasts only for the first few weeks of life: "This demonstration
of learning during sleeping is probably restricted to very young infants."