Harvard University has been running the world's longest study into happiness. The Harvard Study of Adult Development has been running since 1938, and in that time of researchers have observed how Americans experience and understand happiness, and how that's changed over time. In an address for the UNSW Centre for Ideas, the study's fourth director, Robert Waldinger, reveals the study's largest findings, and how technology — and changes in society — have inflected the interpretation of the study's data.