The brains of people who can speak two languages actually work differently than their one-language counterparts, according to a recent study.
According to a study published in Psychological Science, children who know two languages can more easily solve problems that involve misleading cues, and knowledge of a second language -- even one learned as an adolescent -- affects how people read their native language.
A team led by Eva Van Assche, a bilingual psychologist at the University of Ghent in Belgium, recruited 45 native Dutch-speaking students who had learned English as a teenager.
The researchers then asked the students to read a selection of Dutch sentences, some of which included cognates -- words that look similar and have equivalent meanings in both languages (such as "seven" and "zeven," or "better" and "beter," or "heart" and "hart").
Recording students' eye movements, the researchers found that the participants spent, on average, eight fewer milliseconds gazing at cognate words than control words. That suggests that their brains processed the dual-language words more quickly than words found only in their native language.
“The most important implication of the study is that even when a person is reading in his or her native language, there is an influence of knowledge of the nondominant second language,” Van Assche said to the British Psychological Society research digest blog in August, adding that auditory stimuli were next for investigation. “Becoming a bilingual changes one of people's most automatic skills.”
See Van Assche's report from 2007 (.pdf) on the subject.