Neuroscientists think that having more reserve brain power helps compensate for age-related declines in thinking and memory, and may help protect against the losses caused by Alzheimer's and other forms of dementia.
It reviews the state of research on bilingual adults, and finds they maintain better executive functioning later in life than monolingual people. That extra "cognitive reserve" may allow the brain to better cope with the damage caused by dementia, thereby delaying symptoms. (Being physically and mentally active has also been shown to have cognitive benefits.) The article, also co-authored by Bialystock, is in the current issue of Trends in Cognitive Sciences.