I’ve noted previously how child bilingualism improves the “executive functions” and a recent study has corroborated these findings while also discovering how bilingualism can stave off dementia in old age:
[Psychologist Ellen Bailystok] wanted to explore whether enhanced executive control actually has a protective effect in mental aging—specifically, whether bilingualism contributes to the “cognitive reserve” that comes from stimulating social, mental and physical activity. She studied a large group of men and women with dementia, and compared the onset of their first symptoms. The age of onset for dementia was a full four years later in bilinguals than in patients who had lived their lives speaking just one language. That’s a whopping difference. Delaying dementia four years is more than any known drug can do, and could represent a huge savings in health care costs.
Is there any downside to bilingualism? Yes. […] Bialystok’s studies also found that bilinguals have less linguistic proficiency in either of their two languages than do those who only speak that language. They have somewhat smaller vocabularies, for example, and aren’t as rapid at retrieving word meanings. But compared to the dramatic cognitive advantages of learning a second language, that seems a small price to pay.
via @siibo