"Over time, regularly speaking more than one language appears to strengthen skills that boost the brain's so-called cognitive reserve, a capacity to work even when stressed or damaged. This build-up of cognitive reserve appears to help bilingual people as they age. 'Speaking two languages isn't going to do anything to dodge the bullet' of getting Alzheimer's disease or dementia, says Ellen Bialystok, a bilingualism researcher at York University in Toronto. But greater cognitive reserve means the 'same as the reserve tank in a car: Once the brain runs out of fuel, it can go a little farther,' she says."