- Speaking two or more languages appears to enhance executive function -- the ability to focus on the information needed to complete a task.
- Bilinguals with Alzheimer's disease retained brain function longer than those who spoke only one language.
- The "cost" of bilingualism is that bilinguals may have smaller vocabularies in each language.
Bilingual education is controversial in the United States, but a growing body of research shows that regularly speaking two languages comes with certain types of improved mental performance.
In a Perspective article appearing today in the journal Science, Jared Diamond of the University of California, Los Angeles, and author of "Guns, Germs and Steel" highlights studies of bilingualism that show this effect.
Diamond began wondering about the effects on the brain of multilingualism while camping with New Guinea Highlanders, all of whom could speak between five and 15 languages.
"What are the cognitive effects of such multilingualism?" Diamond asked in the new article.
"Being able to use two languages and never knowing which one you're going to use right now rewires your brain," said Ellen Bialystok of York University in Toronto, Canada, whose work Diamond cited repeatedly in the article.
"The attentional executive system which is crucial for all higher thought -- it's the most important cognitive piece in how we think -- that system seems to be enhanced," she noted.
Executive functioning allows us to keep a goal in mind, take actions to achieve that goal, and to ignore other information that might distract us from that goal, said Albert Costa, who studies bilingualism at the Universitat Pompeu Fabra in Barcelona, Spain.
"The question is: Would it be the case that bilinguals, by the constant need for controlling the two languages, develop a more efficient executive functioning system?" he said. "The results suggest that bilinguals may have this positive collateral effect."
"The effects are much stronger when you go to kids and older people," he added. These are ages where executive functioning is worse.
Bialystock has shown that bilinguals do better at tests that require multitasking, including ones that simulated driving and talking on a phone.
"Make no mistake: Everybody is worse," Bialystock said, "but the bilinguals were less worse."
Bialystock's studies focused on people who were truly bilingual. The longer people have spoken multiple languages, the greater the cognitive effects. There are even benefits when languages were taken up at later ages. "We have not seen a cutoff," she said.