A new study of people who speak many languages has found that there is something special about how the brain processes your native language.
In the brains of these polyglots (people who speak five or more languages) the same linguistic regions light up when they hear any of the languages they speak. In general, this network responds more strongly to languages in which the speaker is more proficient, with one notable exception: the speaker’s native language. When listening to the native language, the activity of the linguistic network decreases significantly.
The findings suggest that there is something unique about the first language one acquires, allowing the brain to process it with minimal effort, the researchers say.
“Something makes it a little easier to process (maybe it’s that you’ve spent more time using that language) and you get a drop in activity in the native language compared to other languages you speak fluently,” says Evelina Fedorenko. , associate professor of neuroscience at MIT, member of MIT’s McGovern Institute for Brain Research, and senior author of the study.
Saima Malik-Moraleda, a graduate student in the Speech and Hearing Bioscience and Technology Program at Harvard University, and Olessia Jouravlev, a former MIT postdoc and now an associate professor at Carleton University, are lead authors of the paper , which appears today. In the diary Cerebral cortex.
Many languages, one network
The brain’s language processing network, located primarily in the left hemisphere, includes regions in the frontal and temporal lobes. In a 2021 study, Fedorenko’s lab found that in the brains of polyglots, the linguistic network was less active when they listened to their native language than the linguistic networks of people who speak a single language.
In the new study, the researchers wanted to expand on that finding and explore what happens in the brains of polyglots when they listen to languages in which they have different levels of proficiency. Studying polyglots can help researchers learn more about the functions of the language network and how languages learned later in life may be represented differently than a native language or languages.
“With polyglots, you can make all the comparisons within a single person. You have languages that vary along a continuum, and you can try to see how the brain modulates responses based on proficiency,” Fedorenko says.
For the study, the researchers recruited 34 polyglots, each of whom had at least some degree of proficiency in five or more languages but were neither bilingual nor multilingual since childhood. Sixteen of the participants spoke 10 or more languages, including one who spoke 54 languages with at least some proficiency.
Each participant was scanned with functional magnetic resonance imaging (fMRI) while they listened to passages read in eight different languages. These included their native language, a language in which they were highly proficient, a language in which they were moderately proficient, and a language in which they described themselves as low proficient.
They were also scanned while listening to four languages they did not speak at all. Two of them were languages from the same family (such as the Romance languages) as languages they could speak, and two were languages that had no relation to any of the languages they spoke.
The passages used for the study came from two different sources, which the researchers had previously developed for other language studies. One was a set of Bible stories recorded in many different languages and the other consisted of passages from “Alice in Wonderland” translated into many languages.
Brain scans revealed that the linguistic network lit up more when participants listened to the languages in which they were best fluent. However, this was not the case for the participants’ native languages, which activated the linguistic network much less than the non-native languages in which they were similarly proficient. This suggests that people are so proficient in their native language that the language network doesn’t need to work hard to interpret it.
“As you increase proficiency, you can perform linguistic calculations to a greater extent, so you get progressively stronger responses. But then if you compare a language with really high proficiency and a native language, it may be that the native language is just a little bit easier, possibly because you have more experience with it,” says Fedorenko.
Brain engagement
The researchers observed a similar phenomenon when polyglots listened to languages they did not speak: their linguistic network was more engaged when they heard languages related to a language they could understand, than when they heard completely unfamiliar languages.
“Here we are getting a clue that the response in the linguistic network increases with how much is understood from the information,” says Malik-Moraleda. “We didn’t quantify the level of understanding here, but in the future we plan to evaluate how much people actually understand the passages they are hearing, and then see how that relates to activation.”
The researchers also found that a brain network known as the multiple demand network, which activates whenever the brain performs a cognitively demanding task, also activates when listening to non-native languages.
“What we’re seeing here is that linguistic regions are involved when we process all these languages, and then there’s this other network that looks for non-native languages to help you because it’s a more difficult task,” Malik-Moraleda says. .
In this study, most polyglots began studying their non-native languages as teenagers or adults, but in future work, the researchers hope to study people who learned multiple languages from a very young age. They also plan to study people who learned a language from childhood but moved to the United States at a very young age and began speaking English as their dominant language, while becoming less proficient in their native language, to help unravel the effects of mastery versus age. of acquisition on brain responses.
The research was funded by the McGovern Institute for Brain Research, the MIT Department of Brain and Cognitive Sciences, and the Simons Center for the Social Brain.