In an essay in the Science Section of the Oct 10, 2011 New York Times, Perri Klass reports on new research about bilingual learning in infants that contains some findings that are not good news for adult language students.

The research shows that infants in monolingual homes can distinguish between sounds in different languages at 6 months but are no longer able to hear distinct sounds in languages other than their own by 10 to 12 months.  By that point, the infants’ brains have become wired to focus only on their native languages, while the sounds of any other language have become mere noise. Babies growing up in bilingual homes do not narrow down in the same way and are able to discriminate sounds in both languages at the same point in their development. Lucky babies! If the capacity for new language acquisition begins to decline by the end of the first year of life, the hurdles adult language learners face seem all the more insurmountable.

Equally fascinating—and discouraging—was some earlier research described by Klass that demonstrated that English-language babies exposed to Mandarin-speakers were able to discriminate Chinese sounds but only in a social setting. If the language was delivered via a TV or audio-tape, “the babies learned nothing.”  Apparently the human brain is receptive to language only when it is delivered face-to-face by another human being. What does this say for the self-taught, DVD foreign language programs currently available?

For an excellent talk by Patricia Kuhl, the principal researcher for the work on which Klass is reporting see: http://bit.ly/xNKGpZ. She describes as babies before 8 months as “citizens of the world,” able to distinguish between all language sounds. By ten months, however, they concentrate on the native language spoken to them and build  up a neural network that creates interference for other languages, which now sound like noise. The better they map their brains for one language, the more they lose the ability to hear other languages.