A new paper by a York University professor finds speaking more than one language has wide-ranging cognitive health benefits for children, adults and seniors.
Professor Ellen Bialystok and co-authors reviewed recent studies using behavioural and neuroimaging methods to examine the effects of bilingualism on cognition across the lifespan. Their review builds on earlier evidence of its benefits for children’s cognitive development. The study, published March 29 in the journal Trends in Cognitive 
Sciences, revealed some surprising results. The researchers found that bilingualism protects against cognitive decline by boosting cognitive reserve and delaying the onset of dementia symptoms. The review also suggests that the increasing diversity in world populations may have an unexpected positive impact on the resiliency of the adult brain.
Ellen Bialystok
“Our conclusion is that lifelong experience in managing attention to two languages reorganizes specific brain networks, creating a more effective basis for executive control and sustaining better cognitive performance throughout the lifespan,” said Bialystok, a Distinguished Research Professor in the Department of Psychology in York’s Faculty of Health.
The study points out that understanding how bilingualism impacts cognitive reserve is crucial in the context of an aging population.
“The possibility that bilingualism contributes to cognitive reserve is certainly of growing importance,” said Bialystok. “Overall we’ve found that bilingualism has benefits in every stage of life. It should not be surprising that intense and sustained experience leaves its mark on our minds, and it is now clear that the bilingual brain has been uniquely shaped by experience.”
This was not always the case: researchers once assumed the effects of speaking more than one language would be negative. In the 1920s, bilingualism was even thought to contribute to lower scores on intelligence tests.
“Nearly a century later, and in the face of substantial evidence that contradicts this assumption, there is still a push by educators and clinicians to ‘simplify’ their children’s linguistic environment whenever there are signs of academic difficulties,” Bialystok said. “Their well-intentioned goal is to minimize confusion, but those strategies are based on fear and anecdote, rather than science.”
The study is co-authored by Fergus Craik, Rotman Research Institute, Baycrest; and Gigi Luk, Harvard Graduate School of Education.