New research is reshaping how scientists think about bilingual language processing. Instead of switching between two separate grammar systems, the brain may rely on a shared grammatical network that supports more than one language at once.
In the study, Spanish-English bilingual participants completed a task that required them to change nouns to match number, such as turning "boat" into "boats" or the Spanish equivalent into its plural form. Researchers also included simple repeat trials to compare ordinary word repetition with true grammatical processing.
Using magnetoencephalography, or MEG, the team tracked brain activity with millisecond precision. The results showed that grammatical changes activated a left frontal-temporal language network in both English and Spanish. Even more notably, computer models trained on one language could identify the same grammatical pattern in the other, suggesting the brain was using a common operation rather than two separate ones.
The study also found that Spanish responses appeared slightly earlier than English ones, likely reflecting differences in processing efficiency rather than a different grammar engine. The same neural pattern was observed even when participants worked with invented words, reinforcing the idea that the brain was applying a flexible rule-based system instead of simply recalling memorized forms.
According to the researchers at New York University, the findings offer some of the clearest evidence yet that bilingual grammar may be built on one reusable neural framework. The authors note, however, that more research is needed across languages with very different structures and across speakers with different levels of fluency.
As language science advances, studies like this may help explain how the brain learns, organizes, and adapts communication across cultures in the years ahead.