Babies, Brains, and Bilingualism

If you’d like to learn a new language, pay attention to the background noise, a new study suggests.

"Yo sé más idiomas que tú!"

See, each person’s brain responds a little differently to different types of sounds. Yours is most sensitive to slight variations in your native tongue (which you think of as accents), and less sensitive to variations in other languages. If you’re musically inclined, your brain is highly responsive to slight changes in rhythm and pitch. But when it comes to say, ceiling fans, it’s unlikely that you could tell them apart by sound alone.

None of this is hard-wired, though – when we’re born, we’re extraordinarily sensitive to just about every sound we hear; as we grow, our brains become “tuned in” to some types of sounds more than others.

Late in their first year of life, babies in monolingual environments become more sensitive to sound differences within their own language, while the brains of babies raised bilingually continue to respond to speech in both languages:

For instance, between 8 and 10 months of age babies exposed to English become better at detecting the difference between “r” and “l” sounds, which are prevalent in the English language. This is the same age when Japanese babies, who are not exposed to as many “r” and “l” sounds, decline in their ability to detect them.

In other words, when a non-native speaker has persistent trouble pronouncing certain words, it may be because his or her brain actually can’t process the difference between, say, the “r” and “l” sounds. To them, it may sound like English speakers are emphasizing an imaginary difference.

As the Journal of Phonetics reports, a team led by UW’s Patricia Kuhl fitted babies with special caps that could measure electrical activity across their scalps (i.e., EEG devices). Then they played random English and Spanish syllables to babies of various ages:

For example, a sound that is used in both Spanish and English served as the background sound and then a Spanish “da” and an English “ta” each randomly occurred 10 percent of the time as contrasting sounds. If the brain can detect the contrasting sound, there is a signature pattern called the mismatch response that can be detected with the EEG.

The researchers found that babies less than eight months old showed equal brain activity for either language – but by ten months of age, the brains of bilingual babies responded to both syllables, while those of monolingual babies only responded to English sounds. So it’s pretty clear that those few months are a critical time in the brain’s language development.

This discovery has a wide range of exciting implications. For one thing, it explains why immersion is such a powerful tool for learning a new language – if your brain is bathed in a constant stream of foreign pronunciation, it’s hard not to become at least a little more sensitive to its sounds. Even if you don’t pick up a lot of new vocabulary, your pronunciation and comprehension are bound to improve.

At least, that’s what happened for the babies in the study:

The researchers followed up with the parents when the babies were about 15 months old to see how many Spanish and English words the children knew. They found that … the size of the bilingual children’s vocabulary was associated with the strength of their brain responses in discriminating languages at 10-12 months of age.

Another intriguing implication involved treatment of autism. Some research suggests that autism-related language problems may be linked to early-life exposure to excessive background noise, which causes the brain to treat, say, ceiling fan noise as if it’s just as relevant as speech.

Even for non-autistic children, though, this research suggests there’s hope for those who have trouble learning even their native language, or for kids who’d like to become bilingual. By combining the latest neurological data with training and exposure exercises, it may be possible to reopen the mind’s sensitivity to a wider range of sounds.

As for me, I’m planning to start my advanced Rosetta Stone Ceiling Fan course as soon as it arrives.

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