Have you ever wondered how does your brain process your language abilities when you speak in one language and not the other? Did you know that both languages are constantly active (readily available) when a bilingual person reads, hears, or speaks in one language?
Learning a second language reorganizes the entire language system in our brains! It is pretty amazing when you think about it.
It used to be believed that the activity of a person’s native language was present at the early stages of the acquisition of a second language. But now there is evidence that suggests activity of both languages when only one of them is in use, even when the person is very fluent in both languages.
This activity shows that a bilingual person acquires new cognitive skills (that engages also different parts of the brain that are not related to language) to use both languages, in addition to the skills related to the vocabulary, grammar, and the phonology of the new language.
Long term application of this knowledge seems to lead to excellent cognitive conflict resolution skills. Which is why it is not a surprise that the elderly bilinguals who have used both of their languages for many years are significantly more resistant to age related decline of mental skills.