It is not possible for bilingual people to completely shut off a language,a new study has shown.
Ghent University psychologists Eva Van Assche, Wouter Duyck, Robert Hartsuiker and Kevin Diependaele have found that knowledge of a second language actually has a continuous impact on native-language reading.
For their study, the research team asked 45 Ghent University students, whose native-language was Dutch and secondary language was English, to read several sentences containing control words - plain words in their native-language - and cognates.
Cognates are words that have a similar meaning and form across languages, often descending from the same ancient language; for example, "cold" is a cognate of the German word "kalt" since they both descended from Middle English.
The researchers recorded the students' eye movements, and observed where their eyes paused (fixation locations), as they read the sentences.
The researchers found that the students looked a shorter period of time at the cognates than at the controls.
According to the psychologists, it is the overlap of the two languages that speeds up the brain's activation of cognates, which is why despite not needing to use their second language to read in their native-language, the participants still were unable to simply "turn it off."
Based on their observations, the researchers came to the conclusion that not only is a second language always active, it has a direct impact on reading another language-even when the reader is more proficient in one language than another.
The study has been published in the journal Psychological Science.