Speaking more than one language may have a cognitive trade-off

Travelers, patrons of exotic restaurants and others who like to connect with the world’s different cultures benefit from speaking in more than one tongue, but new research also suggests that the skill comes with a cognitive price tag. Language efficiency in children and adults tends to suffer slightly, with children learning vocabulary more slowly and adults exhibiting slower linguistic response times, says Ellen Bialystok, PhD, a cognitive psychologist at York University in Toronto.

At a Jan. 14 lecture in Rockville, Md., put on by the National Institutes of Health’s Office of Behavioral and Social Sciences Research, Bialystok described a study in which she and colleagues measured the vocabularies of 1,738 monolingual and bilingual children ages 3 to 10. At every age, monolinguals slightly outperformed bilinguals on the Peabody Picture Vocabulary Test, in which the test administrator announces the name of an object on a page with multiple images while the participant points to it as quickly as possible.

While the vocabulary of both bilingual and monolingual people eventually evens out, other small differences persist into adulthood, said Bialystok. For example, adult bilinguals are slower to name pictures and have more “tip-of-the-tongue” moments in which they know a word in question, but can’t recall it. In addition, monolingual adults who were asked to name as many objects that belong to a particular category within a short time frame performed better than bilinguals who took the same test.

What’s behind the cognitive slowdown in bilinguals? One possibility is that the bilingual brain has to take an extra step to decide which language to respond in. “If you are an active, sustained bilingual, both languages are always active,” Bialystok explained, “even in a monolingual context.”

Of course, there are also clear cognitive benefits of speaking more than one tongue, Bialystok said. Brain-imaging research has shown that when people switch to another language, their brains make constant use of their executive control network, which involves the dorsolateral prefrontal cortex, anterior cingulate cortex, Broca’s area and the basal ganglia. Working out those brain areas may make these people better able to perform other activities that require switching, such as visual searches where people are asked to find the incongruent image or pattern. In fact, some studies suggest that strengthening the connections in these brain regions may protect against cognitive decline in aging adults and might even delay the onset of Alzheimer’s disease, Bialystok said.

—M. Price