Photo: Kate Samp for Strategies for Children

Although experts no longer fear that young children growing up in a bilingual household will experience language confusion, relatively little has been known about how the brain acquires two languages. Now, in “Hearing Bilingual,” The New York Times reports that scientists are getting a clearer picture of the differences in the brain development of babies in monolingual and bilingual homes.

“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,” writes Dr. Perri Klass, national medical director of Reach Out and Read and professor of pediatrics and journalism at New York University. “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.”

In one study at the University of Washington, researchers measured the electrical responses of babies’ brains and found that at 6 months, infants in monolingual homes could discriminate between phonetic sounds whether or not they were in a familiar language. By 10 to 12 months, they could no longer discern sounds in the unfamiliar language. Infants in bilingual homes, on the other hand, could detect sounds in both languages at 10-12 months of age.

“What the study demonstrates is that the variability in bilingual babies’ experience keeps them open,” Dr. Patricia Kuhl, co-author of the study and co-director of the Institute for Learning and Brain Sciences at the University of Washington, tells Dr. Klass. “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.”

In another study, researchers at the University of British Columbia found that infants born to bilingual mothers are able to distinguish between the two languages. Research from York University in Toronto finds that “bilingual children develop crucial skills in addition to their double vocabularies, learning different ways to solve logic problems or to handle multitasking, skills that are often considered part of the brain’s so-called executive function,” Klass writes. “These higher-level cognitive abilities are localized to the frontal and prefrontal cortex in the brain. ‘Overwhelmingly, children who are bilingual from early on have precocious development of executive function,’ Dr. Bialystok said.”

The research into bilingualism also confirms what other research on language development has shown. Young children learn language in the context of social interaction, not merely from hearing words. University of Washington researchers have shown that babies in English-speaking homes maintain an ability to distinguish sounds in Mandarin if they have been exposed to the language by having someone speak to them in Mandarin. This is not true if they heard Mandarin only on television or an audio tape.

“This special mapping that babies seem to do with language happens in a social setting,” Dr. Kuhl tells Dr. Klass.  “They need to be face to face, interacting with other people. The brain is turned on in a unique way.”