Bilingualism
How bilingual life shapes brain structure over time
Open access · cc by · source: Europe PMC
Being highly bilingual is linked to steady growth in brain regions that control movement and learning, but causes wave-like volume changes in language-control areas.
Key findings
The researchers found that higher bilingualism scores were tied to linear volume increases in the putamen and the cerebellum. In contrast, the left and right inferior frontal gyrus showed a complex, wave-like relationship, where volume first decreased, then increased, and finally decreased again at the highest levels of bilingualism. No significant changes were observed in other key regions like the caudate nucleus or thalamus.
Methodology
Researchers scanned the brains of 274 bilingual adults in Spain who grew up using Spanish and Catalan to varying degrees. They calculated a custom bilingualism score for each participant using a language background questionnaire. Using advanced statistical models, they looked for non-linear patterns of change in brain regions responsible for speech and cognitive control.
Limitations
This cross-sectional study cannot prove that bilingualism directly causes brain structures to grow or shrink over time, as participants were only scanned at a single point in time. Furthermore, because the researchers did not measure the specific conversational context—such as how often participants naturally switch languages versus being forced to switch—they could only speculate on the reasons behind the wave-like changes in the frontal cortex. Finally, the findings are specific to a bilingual region with co-official languages, meaning they might not apply to bilinguals living in societies where one language is heavily marginalized.
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