会双语让人更聪明

RENEE MONTAGNE, host: This is MORNING EDITION from NPR News. I'm Renee Montagne.

In today's health segment, people with rare diseases help each other using the Internet. But first, in an increasingly interconnected world, speaking more than one language is becoming common. Approximately one out of five Americans speak a language other than English at home. Around the world, as many as two-thirds of children are brought up bilingual. And it turns out that being bilingual is also good for the brain. Reporter Gretchen Cuda-Kroen has the story.

Ms. JUDY SZENTKIRALYI: (Foreign language spoken)

Mr. PAUL SZENTKIRALYI: (Foreign language spoken)

GRETCHEN CUDA-KROEN: Judy and Paul Szentkiralyi both grew up in the U.S. bilingual - speaking Hungarian with their families and English with their peers. And when they married they knew they wanted to raise their children speaking both languages. So their two daughters, Hannah and Julia, heard only Hungarian from mom and dad at home.

Ms. HANNAH SZENTKIRALYI: (Foreign language spoken)

CUDA-KROEN: Then came school and learning English. Judy recalls Hannah's first few months with the new language.

Ms. SZENTKIRALYI: When she did go to preschool that accent was very thick. She's counting like vun(ph), two, tree. And by the time maybe four or five months went by it was totally gone.

CUDA-KROEN: Most people were supportive, but not everyone. Judy's husband Paul recalls an uncomfortable confrontation Judy once had in a local grocery store.

Mr. SZENTKIRALYI: I remember one time you came home, you said this one lady was, well, when's she going to learn English. It's like, well, when she goes to school she'll learn English.

CUDA-KROEN: The Szentkiralyi's says that people often asked them if their kids got confused or if they fell behind in school. Janet Werker has an answer for them. She's a psychologist at the University of British Columbia who studies language acquisition in bilingual babies. Werker says the idea that children exposed to two languages from birth become confused or that they fall behind is a common misconception.

Ms. JANET WERKER (University of British Columbia): Growing up bilingual is just as natural as growing up monolingual. There is absolutely no evidence that bilingual acquisition leads to confusion and there is no evidence that bilingual acquisition leads to delay.

CUDA-KROEN: Werker and other researchers say the evidence to the contrary is actually quite strong. Being bilingual, they say, may actually be good for you.

Ellen Bialystok, a psychologist from York University in Toronto, says the reason lies in the way the bilingual mind uses language. No matter what language a person is speaking at the moment, Bialystok says both languages are active in the brain.

Ms. ELLEN BIALYSTOK (York University, Toronto): The evidence is very dramatic. Even if you're in a context that's utterly monolingual where you think there's absolutely no reason to think about Chinese or Spanish or French, it is part of the activated network that's going on in your brain.

CUDA-KROEN: This means bilinguals have to do something that's monolinguals don't do. They have to keep the two languages separate. Bialystok likens it to tuning into the right signal on the radio or television the brain has to keep the two channels separate and pay attention to only one.

Ms. BIALYSTOK: The brain has a perfectly good system whose job it is to do just that - it's the executive control system. That's what it does. It focuses attention on what's important, and ignores misleading distraction. Therefore, for a bilingual, every time you open your mouth to speak, you recruit this executive control system. It's always used in every sentence you utter. That's what makes it strong.

CUDA-KROEN: Bialystok says that constantly engaging this executive control function is a form of mental exercise, and some researchers, including herself, believe that this can be beneficial for the brain. Bilingual speakers have been shown to perform better on a variety of cognitive tasks, and one study Bialystok did found that dementia(痴呆) set in 4-5 years later in people who spent their lives speaking two languages instead of one.

Ms. BIALYSTOK: They can get a little extra mileage(好处，益处) out of these cognitive networks because they have been enhanced throughout life.

CUDA-KROEN: And the advantages of bilingualism may be due to more than just mental fitness. Bialystok says there's some preliminary evidence that being bilingual may physically remodel parts of the brain.

For NPR News, I'm Gretchen Cuda-Kroen in Cleveland.