A Linguist Explains What Happens in Your Brain When You Switch Languages

Research on bilingual processing shows that the language not currently being spoken is not simply dormant. Words, sounds, and meanings from both languages can become active, especially when they resemble one another. This co-activation is usually helpful. Shared words and concepts can accelerate recognition. It can also create competition. The speaker must select the word and grammatical form that fit the intended language, audience, and situation.

There is no single bilingual switch in the brain. Language control recruits a network that overlaps with systems used for attention, action selection, monitoring, and speech production. In laboratory tasks, bilinguals often name a picture more slowly immediately after a cue tells them to change languages. This difference is called a bilingual switch cost. One explanation is that the brain must disengage from one language goal, increase activation of another, and resolve competition among possible words. Switch costs are not always equal in both directions. When one language is more dominant, switching back to it can sometimes be unexpectedly costly. If the dominant language had to be strongly suppressed so the less dominant language could be used, the system may need extra time to reactivate it. This counterintuitive result helped motivate inhibitory accounts of bilingual language control.

Imagine three settings. At work, a bilingual uses English and avoids another language. At home, the speaker uses Spanish with one person and English with another. With bilingual friends, everyone fluidly draws on both languages. Each environment makes different demands. The adaptive control hypothesis proposes that language-control processes adjust to recurring interactional contexts. A single-language setting emphasizes maintaining one language and limiting intrusions. A dual-language setting demands monitoring speakers and switching appropriately. Dense code-switching can rely more on cooperative language use because mixing is expected rather than treated as an error Green & Abutalebi (2013)↗.

Early and highly proficient bilinguals often recruit largely overlapping language networks for both languages. A less practiced language may require greater activity in control-related regions because word retrieval is slower and competition is harder to resolve. With experience, processing can become more efficient, and switching can feel more automatic. The brain is plastic: repeated multilingual use can lead to functional and structural adaptation. However, it is too simple to claim that bilingualism gives every person a general cognitive advantage. Findings outside language tasks are mixed, and outcomes depend on the population, measures, and bilingual experience being studied. The clearest conclusion is narrower: managing multiple languages trains a flexible language-control system Lehtonen et al. (2018)↗.

People sometimes interpret a mixed-language sentence as evidence that the speaker lacks a word or cannot keep languages separate, but switching languages is not a failure of control. It is one possible outcome of controlling it. In some contexts, separation is the goal. In others, flexible combination communicates more effectively. Language switching gives linguists and neuroscientists a window into how the brain selects among competing possibilities. It shows that languages are neither sealed in separate boxes nor blended into one undifferentiated whole. They remain distinguishable while interacting through shared concepts, sounds, words, and control processes.

The next time a bilingual speaker changes languages mid-sentence, the remarkable fact is not that one language interrupted another. Instead, the brain coordinated two linguistic systems, a social situation, and a communicative goal quickly enough for the conversation to continue.

References and additional readings:

• Abutalebi, J., & Green, D. (2007). Bilingual language production: The neurocognition of language representation and control. Journal of Neurolinguistics, 20(3), 242–275. ↗
• Green, D. W., & Abutalebi, J. (2013). Language control in bilinguals: The adaptive control hypothesis. Journal of Cognitive Psychology, 25(5), 515–530. ↗
• Lehtonen, M., Soveri, A., Laine, A., Järvenpää, J., de Bruin, A., & Antfolk, J. (2018). Is bilingualism associated with enhanced executive functioning in adults? A meta-analytic review. Psychological Bulletin, 144(4), 394–425. ↗
• Luk, G., Green, D. W., Abutalebi, J., & Grady, C. (2012). Cognitive control for language switching in bilinguals: A quantitative meta-analysis of functional neuroimaging studies. Language and Cognitive Processes, 27(10), 1479–1488. ↗
• Sulpizio, S., Del Maschio, N., Del Mauro, G., Fedeli, D., & Abutalebi, J. (2020). Bilingual language processing: A meta-analysis of functional neuroimaging studies. Neuroscience & Biobehavioral Reviews, 108, 834–853. ↗