Hearing Bilingual: How Babies Sort Out Language
By PERRI KLASS, M. D.
Once, experts feared that young children exposed to more than one language would suffer “language confusion,” which might delay their speech development. Today, parents often are urged to capitalize on that early knack for acquiring language. Upscale schools market themselves with promises of deep immersion in Spanish – or Mandarin – for everyone, starting in kindergarten or even before.
Yet while many parents recognize the utility of a second language, families bringing up children in non-English-speaking households, or trying to juggle two languages at home, are often desperate for information. And while the study of bilingual development has refuted those early fears about confusion and delay, there aren’t many research-based guidelines about the very early years and the best strategies for producing a happily bilingual child.
But there is more and more research to draw on, reaching back to infancy and even to the womb. As the relatively new science of bilingualism pushes back to the origins of speech and language, scientists are teasing out the earliest differences between brains exposed to one language and brains exposed to two.
Researchers have found ways to analyze infant behavior – where babies turn their gazes, how long they pay attention – to help figure out infant perceptions of sounds and words and languages, of what is familiar and what is unfamiliar to them. Now, analyzing the neurologic activity of babies’ brains as they hear language, and then comparing those early responses with the words that those children learn as they get older, is helping explain not just how the early brain listens to language, but how listening shapes the early brain.
Recently, researchers at the University of Washington used measures of electrical brain responses to compare so-called monolingual infants, from homes in
which one language was spoken, to bilingual infants exposed to two languages. Of course, since the subjects of the study, adorable in their infant-size EEG caps, ranged from 6 months to 12 months of age, they weren’t producing many words in any language.
Still, the researchers found that at 6 months, the monolingual infants could discriminate between phonetic sounds, whether they were uttered in the language they were used to hearing or in another language not spoken in their homes. By 10 to 12 months, however, monolingual babies were no longer detecting sounds in the second language, only in the language they usually heard.
The researchers suggested that this represents a process of “neural commitment,” in which the infant brain wires itself to understand one language and its sounds.
In contrast, the bilingual infants followed a different developmental trajectory. At 6 to 9 months, they did not detect differences in phonetic sounds in either language, but when they were older – 10 to 12 months – they were able to discriminate sounds in both.
“What the study demonstrates is that the variability in bilingual babies’ experience keeps them open,” said Dr. Patricia Kuhl, co-director of the Institute for Learning and Brain Sciences at the University of Washington and one of the authors of the study. “They do not show the perceptual narrowing as soon as monolingual babies do. It’s another piece of evidence that what you experience shapes the brain.”
The learning of language – and the effects on the brain of the language we hear – may begin even earlier than 6 months of age.