It's not uncommon for bilingual speakers to mistakenly apply the grammatical rules of one language while speaking the other—for example, saying "I have 20 years" instead of "I am 20" when asked about their age.
Some may wonder if these language mashups are evidence of deeper neurological distinctions among languages: If you speak English and Spanish, for instance, do you have an English "grammatical engine" that learns and applies English rules and a Spanish one that learns and applies Spanish rules?
A new study by a team of New York University scientists finds that, in fact, bilingualism is not powered by separate grammar engines in the brain, but, rather, by a common neural system that works across languages.
"Our research suggests that brains have a single grammatical engine that fuels all of the languages we speak—rather than separate engines for each one," explains Esti Blanco-Elorrieta , an assistant professor of psychology and neural science at NYU and the senior author of the study, which appears in JNeurosci. "We show that the same brain patterns support grammar in English and Spanish, indicating that human language may be built from neural computations that transcend any one language."
While previous research has found neurological commonality across speakers of different languages and other NYU research has explored "bilingual brains," less clear is how the brain builds grammar across languages in bilingual speakers.
To address this, Blanco-Elorrieta and Xuanyi Jessica Chen, an NYU doctoral student and the paper's first author, used magnetoencephalography (MEG) to track brain activity millisecond-by-millisecond while Spanish-English bilingual speakers transformed both English and Spanish words into grammatically correct forms. For instance, participants would hear a singular form of a word ("boat" [English] or "barco" [Spanish]) and were asked to say the plural version of the term (e.g., "boats" or "barcos").
The researchers also tested how participants responded to both cognates—words in different languages that share a similar meaning, spelling, and pronunciation because of their common linguistic roots—and "pseudowords" (made-up words such as "paple").
This method, which reached beyond existing words in English and Spanish, was aimed at determining if the same neural mechanisms apply when novel words enter our vocabulary.
The findings showed that the brain relies on a shared neural mechanism for grammar across languages, even when words differ in sound or structure. Moreover, the same neural system also applied to completely novel words (i.e., pseudowords), further suggesting that the brain implements grammar as a reusable computation—or universal language template—rather than deploying multiple language-specific rulebooks.
"The results provide some of the clearest neural evidence to date that grammatical computations are shared across languages in bilingual speakers," says Blanco-Elorrieta, who previously teamed up with Chen to create a calculator to measure multilingualism. "More broadly, because the brain appears to use a common neural system across languages, our findings offer new insight into how we communicate and learn new languages."
This research was supported by grants from the National Science Foundation (BCS-Grant 2446452) and the National Institutes of Health (R00 DC019973-01).
