The Happiness Hypothesis: Putting Ancient Wisdom to the Test of Modern Science

by Jonathan Haidt

When it comes to explaining personality, it’s always true that nature and nurture work together. But it’s also true that nature plays a bigger role than most people realize. Consider the identical twin sisters Daphne and Barbara. Raised outside London, they both left school at the age of fourteen, went to work in local government, met their future husbands at the age of sixteen at local town hall dances, suffered miscarriages at the same time, and then each gave birth to two boys and a girl. They feared many of the same things (blood and heights) and exhibited unusual habits (each drank her coffee cold; each developed the habit of pushing up her nose with the palm of the hand, a gesture they both called “squidging”). None of this may surprise you until you learn that separate families had adopted Daphne and Barbara as infants; neither even knew of the other’s existence until they were reunited at the age of forty. When they finally did meet, they were wearing almost identical clothing.23 Such strings of coincidences are common among identical twins who were separated at birth, but they do not happen among fraternal twins who were similarly separated.