Biologically, we all age. Joints get stiffer, arteries get thinner and eyes and ears just don’t gather information they way they used to. Based on their unparalleled collection of five decades of health data following residents in Dunedin, New Zealand, Duke psychologists Terrie Moffitt and Avshalom Caspi have devised a way to measure whether a person is biologically aging one year for every calendar year or at a faster — or slower — pace. Listen here.