Being bilingual can affect how your brain works. But it all depends on how you use the language and whether you acquired the language from birth or much later. Research suggests that as you learn or regularly use a second language it becomes constantly active alongside your native language in your brain. To enable communication, your brain has to select one language and inhibit the other. This process takes effort and the brain adapts to do this more effectively.
It is altered both structurally, through changes in the size or shape of specific regions and functionally, through changes in how much specific regions are used. These adaptations usually occur in brain regions and pathways that are also used for other cognitive processes. In one experiment, researchers measured these cognitive processes. They found that being bilingual can potentially improve performance typically in either faster reaction times or higher accuracy.
But other studies have shown equal performance among the bilinguals and monolinguals. Multiple studies have shown that different factors influence how the brain adapts to language skills. These include how long someone has been using more than one language. In addition, the regularity or diversity of use can also affect brain adaptation.
The amount of switching between languages also plays a role. These studies find that different language experiences have distinct effects on brain adaptation and performance on tasks. These adaptions are also dynamic which means that the brain seems to keep adapting with continued and changing experience.
For example, the brains adapts regions in frontal areas of the cortex when a person is in the process of learning the new language. This would ensure that the learner can more effectively handle the increased effort required to select and control the languages.