Use it and keep it Older adults who have careers or interests that keep them intellectually active retain their full intelligence longer than those who retire to a nonintellectual life. Shown here is Phil Aune, nicknamed “Pa-Pa Alpha,” who retired at age 70 as the world’s oldest air-traffic controller. Mr. Aune worked for 47 years at California’s Van Nuys Airport, the world’s busiest general-aviation airport.