People who speak more than one language do not exhibit symptoms of Alzheimer’s disease until they have twice as much brain damage as unilingual people, a new study shows. It’s the first physical evidence that bilingualism delays the onset of the disease. “This is unheard of—no medicine comes close to delaying the onset of symptoms and now we have the evidence to prove this at the neuroanatomical level,” says Tom Schweizer, a neuroscientist and professor of surgery at the University of Toronto who headed the research.