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How Brains Seamlessly Switch Between Languages

Bilingual people engage the same brain region that monolingual individuals use to put together words—even when combining different languages.

Scientific American

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Billions of people worldwide speak two or more languages. (Though the estimates vary, many sources assert that more than half of the planet is bilingual or multilingual.) One of the most common experiences for these individuals is a phenomenon that experts call “code switching,” or shifting from one language to another within a single conversation or even a sentence.

In 2021 Sarah Frances Phillips, a linguist and graduate student at New York University, and her adviser Liina Pylkkänen published findings from brain imaging that underscore the ease with which these switches happen and reveal how the neurological patterns that support this behavior are very similar in monolingual people. The new study reveals how code switching—which some multilingual speakers worry is “cheating,” in contrast to sticking to just one language—is normal and natural. Phillips spoke with Mind Matters editor Daisy Yuhas about these findings and why some scientists believe bilingual speakers may have certain cognitive advantages.

[An edited transcript of the interview follows.]

Can you tell me a little bit about what drew you to this topic?

I grew up in a bilingual household. My mother is from South Korea; my dad is African-American. So I grew up code switching a lot between Korean and English, as well as different varieties of English, such as African-American English and the more mainstream, standardized version.

When you spend a lot of time code switching, and then you realize that this is something that is not well understood from a linguistic perspective, nor from a neurobiological perspective, you realize, “Oh, this is open territory.”

Most of the world operates with two or more languages. We should have models that tell us how brains operate not only within a single language but also across languages. We need to have a better understanding of what typical bilingual behavior and brain processes look like rather than relying on monolingual models of how languages are processed in the brain. Those single-language models, potentially, could cause people who are bilingual to be misdiagnosed with processing deficits just because they’re doing something that doesn’t fit what monolingual people typically do.

Rather than deficits, some researchers have argued that there is a “bilingual advantage.” Can you explain that idea?

The claim—and there’s debate around it that makes it kind of a hot topic—is that bilingual people exhibit some kind of cognitive advantage, compared with their monolingual peers. This comes out of work done by Ellen Bialystok at York University [in Toronto], who saw that bilingual speakers were faster at doing cognitively demanding tasks, such as a psychological test where you have to inhibit some information to be able to successfully complete an assignment. These kinds of tasks are not necessarily linguistic in function; they tap into other things that we typically use on a day-to-day basis, such as attention and working memory.

Could code switching relate to possible memory and attention benefits?

One recent idea about improved cognitive functioning, which comes from work by researchers such as Judith Kroll at the University of California, Irvine, is that social aspects of language switching—such as deciding when and how you switch—could help explain potential benefits. Let’s say you have a Spanish-English bilingual person talking to another Spanish-English bilingual person. Well, that is actually the easiest mode of conversation for them both because they can use whatever words work in whatever ways they want to put those words together to convey thoughts and ideas that they have, right?

What’s actually hard is when you’re in a situation where you have to stick with just one language. Let’s say, as a Spanish-English bilingual person, you’re in conversation with someone who only speaks English or Spanish. In one hypothesis, the adaptive control hypothesis, the bilingual individual has to work really, really hard to make this conscious effort to suppress a language to communicate effectively with one monolingual person versus another fellow bilingual person.

Current ideas about the bilingual brain suggest that both languages are always accessible, even when the bilingual person is speaking with a monolingual person. So in specific social contexts, bilingual people have to further develop their working memory and attention skills to prevent switching to the language that the monolingual speaker would not understand.

What did you do in your new study?

I was really interested in looking at what happens in the brain when bilingual people switch languages as they compose words together. We gathered data from 20 English-Korean bilingual and biliterate participants, meaning they’re able to read, write, speak and listen in both Korean and English. They each did more than 700 trials. And we used a technique called magnetoencephalography, or MEG, to track brain activity.

We presented participants a subject and intransitive verb [forms of speech that combine in the same way in both languages] to observe brain activity when these words combine. So in monolingual speakers, when we get something like “icicles” and “melt,” it creates a greater peak of activity in a part of the brain called the left anterior temporal lobe because these words combine. But if we use “melt” and “jump,” or other verbs, we don’t see this effect because those words don’t combine into something meaningful.

What did you find when you did this test on bilingual people?

We replicated what’s found in monolingual people: So when “melt” is in the context of “icicles,” we see increased activity when compared with “jump”—and we see recruitment of the left anterior temporal lobe. We found this both in language switching [between English and Korean] and orthography [with Roman and Korean characters]. We’re manipulating the language, as well as the representation of these words.

In other words, the brain activity looks a lot like what occurs in people who speak just one language. What does that tell us about code switching?

The fact that the left anterior temporal lobe is able to combine these concepts in meaningful ways without slowing down, without being affected by where these concepts are coming from or how they’re being presented to us, tells us that our brains are able to do this kind of process naturally, and so we shouldn’t shy away from it.

One of the things that I want people to know and understand is that code switching is very natural for bilingual people. Asking us to maintain a single language is harder. I think that while most bilingual individuals have a negative attitude toward code switching—they think it’s bad or that we should stick to one language—it’s not actually bad for our brain. I think that it’s important to recognize that just because something doesn’t look like monolingual behavior doesn’t mean it’s deviant.

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This post originally appeared on Scientific American and was published November 30, 2021. This article is republished here with permission.

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