Being bilingual improves the executive functioning processes that manage things such as attention, working memory, planning, and problem-solving. The bilingual mind experiences a workout from constantly suppressing one language while activating another, which builds up the brain's cognitive processes.
"This is the most important cognitive system we have," Bialystok says. "There are studies showing that executive function in childhood predicts academic outcomes in a narrow sense, and broader success outcomes in life."
But when Bialystok started doing research on the bilingual effect, there was a concern that socioeconomic factors were interfering with the results. Now there are a number of studies that, when taken together, she says "rule out that our effects are limited to a certain socioeconomic status, or even worse, confounded by socioeconomic status and not reflecting the effects of bilingualism."
One study Bialystok was involved with looked at a group of low-income children from a specific region of Portugal. On a litany of tests, measuring things like intelligence and visual memory, the kids who stayed in Portugal and those who had immigrated to Luxembourg and learned to speak Luxembourgish performed the same. But on the measures that test the brain's control function, researchers found that the kids in Luxembourg "significantly outperformed those who stayed behind," Bialystok says.
Overall, kids from poorer socioeconomic backgrounds tend to perform worse than wealthier kids on executive functioning measures. Bilingualism, it appears, can help compensate for that gap.
A separate 2008 study from University of Washington researchers compared Spanish-English native bilingual kindergarteners (who tended to come from more disadvantaged backgrounds) to English speakers enrolled in second-language immersion and English-only speakers. The native bilinguals outperformed the other groups on executive function tests. But that was only after controlling for factors like socioeconomic status; before doing that, their scores were the same. Given the impact of socioeconomic and other factors on cognitive development, those kids should have done worse than their more-advantaged peers. Essentially, disadvantaged bilinguals may be "doing more with less," the researchers noted.
That study was particularly notable because after English, Spanish is by far the most common spoken language in the U.S. About 60 million people, or one in five, speak a language other than English at home, according to 2011 Census data. And 21 percent of them live below the poverty line, compared to just 14 percent of the general population.
Myths still persist around bilingualism. For a long time, educational experts concluded that it took bilingual kids much longer to develop language skills, says Sarah Roseberry Lytle, the director of translation at the University of Washington's Institute for Learning and Brain Sciences. It turns out that's not the case; it just looked that way when those kids were assessed in only one language.