Study finds bilingual brains use one shared grammar engine

Bilingual brains do not appear to carry two separate grammar rulebooks. In a study of Spanish-English speakers, New York University researchers used millisecond-by-millisecond brain imaging to show that the same neural pattern helped turn singular words into plurals in both languages, even when the words were novel.

Using magnetoencephalography, or MEG, the team tracked activity as participants shifted singular forms into plurals in English and Spanish. The study also tested cognates, words that sound similar across languages, and pseudowords, made-up forms designed to see whether the brain would still recruit the same machinery when the language input was unfamiliar. The answer, the authors said, was yes: grammar appeared to rely on a shared neural mechanism across languages, not on separate language-specific systems.

Senior author Esti Blanco-Elorrieta, an assistant professor of psychology and neural science at NYU, said the results suggest the brain has a single grammatical engine that fuels the languages a person speaks. First author Xuanyi Jessica Chen helped lead the work, which was published in JNeurosci. The finding matters because it shifts the bilingual debate away from the old image of two parallel language programs and toward a model in which grammar is a reusable computation, something the brain can apply across languages even when sounds and structures differ.

That does not mean every part of bilingual language use is shared, or that the study settled every question about how people switch, mix, or learn languages. It does add to a broader body of evidence that language networks are often overlapping rather than fully compartmentalized. In 2024, researchers at MIT’s McGovern Institute for Brain Research reported that polyglots who speak five or more languages show activation in the same language regions when they listen to any language they know, although the native language can be processed with unusual efficiency. Reviews in Nature Reviews Neuroscience have likewise described bilingual language use as dynamic, with continual interaction rather than hard separation.

The public-health stakes reach beyond the lab. In Spanish-English bilingual communities and other multilingual settings, a better account of how grammar is shared could eventually shape language learning, speech therapy, and rehabilitation after stroke, where clinicians are often trying to help patients rebuild damaged language abilities. The larger equity issue is just as clear: with about 7,000 spoken and signed languages around the world, neuroscience has long leaned too heavily on monolingual subjects. Work like this begins to correct that imbalance by treating bilingualism not as a curiosity, but as a central model for how the human brain organizes language.