Twenty-eight years ago James R. Flynn, a researcher at the University of Otago in New Zealand, discovered a phenomenon that social scientists still struggle to explain: IQ scores have been increasing steadily since the beginning of the 20th century. Flynn went on to examine intelligence-test data from more than two dozen countries and found that scores were rising by 0.3 point a year—three full points per decade. Nearly 30 years of follow-up studies have confirmed the statistical reality of the global uptick, now known as the Flynn effect. And scores are still climbing.