Babies’ brains practice words long before they can speak

A one-year-old sits in a brain scanner while researchers record her brain responses to spoken syllables.   

Institute for Learning & Brain Sciences/UW

Newborn babies arrive as strangers in a strange land. They know nothing of the customs or language of their new mysterious world. Yet astonishingly, with almost no obvious effort, babies learn an entirely new language. Some babies even learn several.

They manage this feat, in part, by tons of behind-the-scenes practice, a new study finds. Babies mentally rehearse the movements required for speech long before they utter a word, scientists reported July 14 in the Proceedings of the National Academy of Sciences.

This result might explain why babies sometimes get those super intense, slightly confused looks when you’re talking to them, kind of like Zoolander’s Blue Steel. Maybe babies are concentrating really hard, trying to figure out exactly how your mouth is able to produce those funny noises.

Scientists led by Patricia Kuhl of the Institute for Learning and Brain Sciences at the University of Washington, Seattle tested the responses of babies’ brains as they listened to spoken syllables. The team used a technique called magnetoencephalography, which measures subtle magnetic differences caused by differences in brain activity, to figure out which brain areas are active when babies hear syllables.

Unlike other brain scanning methods, a little bit of motion is OK with MEG, making the technique great for little kids. (University of Washington lab member Sarah Roseberry Lytle says that the lab keeps a professional toy-shaker around for the sole purpose of taming wiggly babies during their scans.)

Syllables of speech mesmerize this baby while scientists figure out which parts of the brain are active.Institute for Learning & Brain Sciences/UW

In 7-month-old babies, brain areas important for movement and hearing were active as the babies heard a familiar syllable. “It’s almost as if their brain is rehearsing,” says Lytle, who directs the outreach division of the Institute for Learning and Brain Sciences and wasn’t involved in the study.

p>In slightly older babies, the brain behaved differently: Auditory areas were very involved, while motor areas seemed to play less of a role. This weakened motor area response in 11-month-old babies, and also in adult listeners, might indicate a baby’s familiarity with the sound.

By 11 months, the syllable has become a familiar one, and the motor areas of the brain might not need to work as hard mimicking the movement. This idea fits with what happened when the older babies heard a syllable that doesn’t exist in their native language. All of a sudden, those motor areas once again jumped to attention.

This result makes sense, given what scientists know about how babies learn language over time. Babies start off as generalists. These little citizens of the world pick up any and all sounds and languages that happen to float by. But during the second half of their first year, babies get choosier and focus more brainpower on the language spoken most frequently around them. So a new sound might prompt babies to start back at square one and try to figure out how the speaker makes that noise.

Studies like these are starting to reveal some of the mysterious ways in which infant brains soak up language so easily. One day, we might actually know how these precocious little learners pull off their linguistic feats. But just because we understand it a little better won’t make it any less amazing.

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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