Study: Multilinguals' brains work differently when it comes to their mother tongue

Researchers from the Massachusetts Institute of Technology (MIT) say that multilinguals' brains work differently when it comes to their native language.

The new study found that in the brains of multilinguals, who speak five or more languages, the language processing network responds similarly when they listen to 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 in the speaker's native language.

When listening to the mother tongue, the activity of the language network decreases significantly, as the results show the presence of a unique quality in the first language that a person acquires, which allows the brain to process it with minimal effort.

In other words, the brains of multilingual people require “relatively little effort when processing their native language.”

“There's something that makes processing a little easier,” says Evelina Fedorenko, an English language expert, associate professor of neuroscience at MIT, member of MIT's McGovern Institute for Brain Research, and lead author of the study. Longer use of that language.

The brain's language processing network, located primarily in the left hemisphere, includes areas in the frontal and temporal lobes.

In a 2021 study, Fedorenko's lab found that in the brains of multilinguals, the language network was less active when listening to their native language than the language networks of people who spoke only one language.

In the new study, the researchers wanted to expand on this finding and explore what happens in the brains of multilinguals as they listen to languages ​​that they have different levels of proficiency in.

Studying multiple languages ​​can help researchers learn more about the functions of the language network, and how languages ​​learned later in life may be represented differently from the mother tongue.

The researchers recruited 34 multilingual people, each of whom had at least some degree of proficiency in five or more languages ​​but who had not been bilingual or multilingual since childhood. 16 of the participants spoke 10 or more languages, including one who spoke 54 languages ​​with at least some proficiency.

Each participant was scanned using functional magnetic resonance imaging (fMRI) while they listened to passages read in eight different languages, including their native language, the language in which they were highly proficient, the language in which they were somewhat proficient, and the language in which they described themselves as having low proficiency.

They were also examined while listening to four languages ​​they had never spoken.

Brain scans revealed that the language network was more active when participants listened to the languages ​​in which they were more proficient. However, this did not apply to the participants' native languages, resulting in the language network being activated significantly less than in non-native languages ​​in which they had similar proficiency. This indicates that mastering the mother tongue does not require great effort to interpret it.

The researchers saw a similar phenomenon when multilinguals listened to languages ​​they did not speak: their language networks were more engaged when listening to languages ​​related to a language they could understand, compared to listening to completely unfamiliar languages.