what are the determinants in how we age? The different systems in our brains age at different rates. Some systems decline as others actually increase in efficiency and effectiveness. The basic message we hear in popular culture, that aging is a time of unmitigated decline, is not accurate. Yes, some things do slow down, but our health, happiness, and mental sparkle need not. The latest neuroscientific research suggests an entirely new way of thinking about aging—about memory, our perceptual systems, intelligence, even about motivation, pain, and our social lives. You might think, as...