53-56為題組

      Joy Hirsch, a neuroscientist in New York, has recently found evidence that children and adults don’t use the same parts of the brain when learning a second language. He used an instrument called an MRI (magnetic resonance imaging) to study the brains of two groups of bilingual people. One group consisted of those who had learned a second language as children. The other consisted of people who learned their second language later in life. People from both groups were placed inside the MRI scanner. This allowed Hirsch to see which parts of the brain were getting more blood and were more active. He asked people from both groups to think about what they had done the day before, first in one language and then the other. They couldn’t speak out loud, because any movement would disrupt the scanning.

      Hirsch looked specifically at two language centers in the brain—Broca’s area, believed to control speech production, and Wernicke’s area, thought to process meaning. He found that both groups of people used the same part of Wernicke’s area no matter what language they were speaking. But how they used Broca’s area was different. 

      People who learned a second language as children used the same region in Broca’s area for both languages. People who learned a second language later in life used a special part of Broca’s area for their second language—near the one activated for their native tongue. 

      How does Hirsch explain this difference? He believes that, when language is first being programmed in young children, their brains may mix all languages into the same area. But once that programming is complete, a different part of the brain must take over a new language. Another possibility is simply that we may acquire languages differently as children than we do as adults. Hirsch thinks that mothers teach a baby to speak by using different methods such as touch, sound, and sight. And that’s very different from sitting in a high school class.