The Giggle Twins: A Selection from Jonathan Haidt’s The Happiness Hypothesis (2006)
“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 . . . .
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. . . . Daphne and Barbara came to be known as the ‘giggle twins.’ Both have sunny personalities and a habit of bursting into laughter in mid-sentence. They won the cortical lottery—their brains were preconfigured to see good in the world. . . . Twin studies generally show that from 50 percent to 80 percent of all the variance among people in their average levels of happiness can be explained by differences in their genes rather than in their life experiences.”—Jonathan Haidt, The Happiness Hypothesis: Finding Modern Truth in Ancient Wisdom (2006)