Bilingual Brain: Here's What Happens When You Flip Between Languages

A study has shed light on the brain mechanisms which allow bilingual people to switch effortlessly from one language to another.

Neurolinguistics researchers already believe parts of the brain in charge of decision-making, the prefrontal and anterior cingulate cortices, light up when we toggle between languages. Now, a study published in the Proceedings of the National Academy of Sciences presents a potential new piece to the puzzle.

Esti Blanco-Elorrieta, graduate student at the NYU neurolinguistics lab, told Newsweek, "The process of switching languages entails [minimally] disengaging from the language that was being used until that point, and engaging in a new language. This study showed that it is turning off the previous language, and not 'turning on' a new language, that is effortful."

And while those who swap between languages may make it seem easy, it is in fact "a remarkably complicated process that involves the successful coordination of two independent language systems," he explained.

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"In fact, previous research has suggested that there is in fact a cognitive cost associated with this process; however, up until now we didn't know exactly where this cost lied."

To investigate how the brain turns off one language and turns on another, researchers enlisted the help of 21 volunteers who were fluent in American Sign Language (ASL). The researchers filmed the participants looking at an image and naming it both in English and sign language simultaneously, as special equipment measured their brain activity.

Turning off one language required activity in the cognitive control areas, but turning on the second language required little to no effort, the team found.

The researchers were surprised to discover that adding on the dominant language didn't require more exertion, even when participants had to use two languages at the same time, said Blanco-Elorrieta.

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"Turning off a language, particularly if that is our dominant language, seems to be effortful for us, so the cognitive cost of switching languages following external demands seems to arise from disengaging from a language that was being used until that point.

"Second, that when we are speaking in our weaker language, adding our dominant language on top is not costly, i.e., we can produce two languages for the price of one in that case."

Understanding how different languages coexist and interact in the human brain is important because it lays the groundwork for investigating the social benefits of being bilingual, Blanco-Elorrieta explained.

San Diego State University's Karen Emmorey, who studied bilingual individuals fluent in English and ASL, collaborated on the research.

Dr. Christos Pliatsikas, of the school of Psychology and Clinical Language Sciences at the University of Reading, U.K., and who was not involved in the study, told Newsweek, "This study fills an important gap in our knowledge of the neurological correlates of bilingualism, and specific bimodal bilingualism, i.e. the ability to use a spoken and a sign language."

The research, as well as previous evidence, indicates that the cognitive control that's needed to speak more than one language could train our brains to become more efficient.

However, Pliatsikas pointed out, "Since this study looks at production at the single word/sign level, it cannot comment on what happens at the sentence or conversational level. But it is a step in the right direction."

This article has been updated with background information.