Being bilingual is great. But it may not boost some brain functions

Advantages of speaking a second language are obvious: easier logistics when traveling, wider access to great literature and, of course, more people to talk with. Some studies have also pointed to the idea that polyglots have stronger executive functioning skills, brain abilities such as switching between tasks and ignoring distractions.

But a large study of bilingual children in the U.S. finds scant evidence of those extra bilingual brain benefits. Bilingual children performed no better in tests measuring such thinking skills than children who knew just one language, researchers report May 20 in Nature Human Behaviour.

To look for a relationship between bilingualism and executive function, researchers relied on a survey of U.S. adolescents called the ABCD study. From data collected at 21 research sites across the country, researchers identified 4,524 kids ages 9 and 10. Of these children, 1,740 spoke English and a second language (mostly Spanish, though 40 second languages were represented).

On three tests that measured executive function, such as the ability to ignore distractions or quickly switch between tasks with different rules, the bilingual children performed similarly to children who spoke only English, the researchers found. “We really looked,” says study coauthor Anthony Dick, a developmental cognitive neuroscientist at Florida International University in Miami, says. “We didn’t find anything.”

That result runs counter to earlier studies — small and large — that turned up advantages in similar tests of executive function for bilingual children, although those results have been contested by other research. Because of its size and the fact that it represented lots of communities across the United States, the ABCD dataset presented “an excellent opportunity to look at this question,” Dick says.

Compared with children who spoke only English, bilingual kids scored slightly lower on a measure of English vocabulary. But the dip was small — “a drop in the bucket,” says Dick, whose son has attended a bilingual Spanish-English school for years.

Still, the complexity of bilingualism makes it hard to draw conclusions from the new results, says social scientist Gigi Luk of McGill University in Montreal. Nuances about whether a child speaks another language at home, when and how the second language was picked up and even whether one language is more respected than another can get lost in these sorts of large studies, she says. “We just don’t have enough information about the bilingual experience that these children have every day.”

The study was aimed at the narrow question of whether bilingualism improves the brain’s executive functioning — not the other advantages that come from knowing a second language. “I don’t want this to be a paper about how parents should not have their children learn a second language,” Dick says. To the contrary, “there are inherent benefits outside of executive function to learning a second language — huge benefits.”