A cognitive neuroscientist, Ellen Bialystok has spent almost 40 years learning about how bilingualism sharpens the mind. Her good news: Among other benefits, the regular use of two languages appears to delay the onset of Alzheimer’s disease symptoms. Dr. Bialystok, 62, a distinguished research professor of psychology at York University in Toronto, was awarded a $100,000 Killam Prize last year for her contributions to social science. We spoke for two hours in a Washington hotel room in February and again, more recently, by telephone. An edited version of the two conversations follows.
Chris Young for The New York Times
Q. How did you begin studying bilingualism?
A. You know, I didn’t start trying to find out whether bilingualism was bad or good. I did my doctorate in psychology: on how children acquire language. When I finished graduate school, in 1976, there was a job shortage in Canada for Ph.D.’s. The only position I found was with a research project studying second language acquisition in school children. It wasn’t my area. But it was close enough.
As a psychologist, I brought neuroscience questions to the study, like “How does the acquisition of a second language change thought?” It was these types of questions that naturally led to the bilingualism research. The way research works is, it takes you down a road. You then follow that road.
Q. So what exactly did you find on this unexpected road?
A. As we did our research, you could see there was a big difference in the way monolingual and bilingual children processed language. We found that if you gave 5- and 6-year-olds language problems to solve, monolingual and bilingual children knew, pretty much, the same amount of language.
But on one question, there was a difference. We asked all the children if a certain illogical sentence was grammatically correct: “Apples grow on noses.” The monolingual children couldn’t answer. They’d say, “That’s silly” and they’d stall. But the bilingual children would say, in their own words, “It’s silly, but it’s grammatically correct.” The bilinguals, we found, manifested a cognitive system with the ability to attend to important information and ignore the less important.
Q. How does this work — do you understand it?
A. Yes. There’s a system in your brain, the executive control system. It’s a general manager. Its job is to keep you focused on what is relevant, while ignoring distractions. It’s what makes it possible for you to hold two different things in your mind at one time and switch between them.
If you have two languages and you use them regularly, the way the brain’s networks work is that every time you speak, both languages pop up and the executive control system has to sort through everything and attend to what’s relevant in the moment. Therefore the bilinguals use that system more, and it’s that regular use that makes that system more efficient.
Q. One of your most startling recent findings is that bilingualism helps forestall the symptoms of Alzheimer’s disease. How did you come to learn this?
A. We did two kinds of studies. In the first, published in 2004, we found that normally aging bilinguals had better cognitive functioning than normally aging monolinguals. Bilingual older adults performed better than monolingual older adults on executive control tasks. That was very impressive because it didn’t have to be that way. It could have turned out that everybody just lost function equally as they got older.
That evidence made us look at people who didn’t have normal cognitive function. In our next studies , we looked at the medical records of 400 Alzheimer’s patients. On average, the bilinguals showed Alzheimer’s symptoms five or six years later than those who spoke only one language. This didn’t mean that the bilinguals didn’t have Alzheimer’s. It meant that as the disease took root in their brains, they were able to continue functioning at a higher level. They could cope with the disease for longer.
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