Happy Sad Shy Glad: Is Personality Pre-Programmed?

Every year, thousands of twins (and other multiples) flock to Twinsburg, Ohio for the Twins Days Festival, a long weekend of wild, rollicking twin-related festivities (a Double-Take Parade, talent shows, a wiener roast, and something called, rather unsettlingly, the ‘Corn Hole Tournament’). An almost equal horde of researchers across a wide range of disciplines –…