In announcing that the nature-nurture debate is over, the psychologist Eric Turkheimer was not just using the traditional mule-trainer’s technique of getting his subjects’ attention, namely whacking them over the head with a two-by-four. He was summarizing a body of empirical results that are unusually robust by the standards of psychology. They have been replicated in many studies, several countries, and over four decades. As the samples grew (often to many thousands), the tools were improved, and the objections were addressed, the results, like the Star-Spangled Banner, were still there.
