Instead research highlights the very differences I noticed. In our 40s, most people are cognitively similar. Divergences in cognition appear around age 60. By 80 “it’s quite dramatically splayed out,” says physician John Rowe, a professor of health policy and aging at Columbia University’s Mailman School of Public Health. Yes, there will be a group diminished by dementia and cognitive decline, but in general the 80-somethings “include the wisest people on the planet,” Carstensen says.