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.”
In one recent study, Dr. Werker and her collaborators showed that babies born to bilingual mothers not only prefer both of those languages over others — but are also able to register that the two languages are different.
In a study of older infants shown silent videotapes of adults speaking, 4-month-olds could distinguish different languages visually by watching mouth and facial motions and responded with interest when the language changed. By 8 months, though, the monolingual infants were no longer responding to the difference in languages in these silent movies, while the bilingual infants continued to be engaged.
Over the past decade, Ellen Bialystok, a distinguished research professor of psychology at York University in Toronto, has shown 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.
Dr. Kuhl calls bilingual babies “more cognitively flexible” than monolingual infants. Her research group is examining infant brains with an even newer imaging device, magnetoencephalography, or MEG, which combines an M.R.I. scan with a recording of magnetic field changes as the brain transmits information.
Previous research by her group showed that exposing English-language infants in Seattle to someone speaking to them in Mandarin helped those babies preserve the ability to discriminate Chinese language sounds, but when the same “dose” of Mandarin was delivered by a television program or an audiotape, the babies learned nothing.
“This special mapping that babies seem to do with language happens in a social setting,” Dr. Kuhl said. “They need to be face to face, interacting with other people. The brain is turned on in a unique way.”
Scaring to see how early the language discrimination starts and how quick we lose our natural inborn ability of multi-lingual