Researchers are exploring some age-old questions about human intelligence. You know it: You are smarter than some people and not as smart as others. So what in that heart of smarts—the brain—creates this difference? Is it our brain’s relative size? (Was Einstein big-brained?) Our amounts of certain brain tissue? Our brain networks’ speed? These are among the possibilities that researchers have identified.

Here we will focus on two other questions: How stable is intelligence over the life span? (Will the precocious 5-year-old likely mature into a talented collegian and a brilliant senior citizen?) And what are the traits and talents of those at the low and high extremes of intelligence?