How we process a second language
We know more about the surface of Pluto, a former planet nearly 8 billion km away, than we do about how our brains process a second language. Although we know how to use effective techniques to teach someone to acquire a second language, how our brains actually do this is still far from clear.
What happens here? Surface of Pluto
We used to think that a second language was stored in a different area of the brain to where we store our first language because people who suffered a brain injury sometimes had selectively impaired language functions. There have been stroke ( a brain injury caused by a lack of blood flow to the brain) patients who have lost their first language and have been left only able to understand and speak in their second language.
However, brain imaging has now changed this understanding of how our brains process a second language. It has been known for some time that two separate areas of the cerebral cortex, the thin outer layer folded and dimpled around the solid grey matter inside, are involved in processing language, one for understanding and the other for production
The Wernicke area deals with the reception of language and the formation of meaning, while the Broca area controls the production of speech. Both of these areas are active whether we are using our first or second language. Studies of patients recovering from brain injury with selective aphasia (different language problems) have shown that two other key areas are involved in switching between languages. One area suppresses the selection of words in the first language, while the other directs the selection of words to the lexical store in the second.
“In speech production, there is plentiful evidence that languages are simultaneously activated and the inappropriate one suppressed, as a function of task.” 1
So when we use our second language we operate both languages simultaneously from the same areas of our brain and simply suppress the one we are not using and switch to the one we are using. It is this combined capacity of the executive function of the brain, also called cognitive control and supervisory attentional system that we train and make fitter when we learn a second language.
There is no separate second language area of the brain. Both languages are stored together, fluency is achieved not only by expanding vocabulary, but by exercising the selecting and switching capacities. Interacting with a skilled first language teacher steadily pushing at your intelligible limits is by far the quickest way to make progress in your fluency, and even just to maintain the fluency you’ve already achieved.