Intelligence makes for better leaders—from undergraduates to executives to presidents—according to multiple studies. It certainly makes sense that handling a market shift or legislative logjam requires cognitive oomph. But new research on leadership suggests that, at a certain point, having a higher IQ stops helping and starts hurting. The researchers looked at 379 male and female business leaders in 30 countries, across fields that included banking, retail and technology. The managers took IQ tests (an imperfect but robust predictor of performance in many areas), and each was rated on leadership style and effectiveness by an average of eight co-workers. IQ positively correlated with ratings of leader effectiveness, strategy formation, vision and several other characteristics—up to a point. The ratings peaked at an IQ of around 120, which is higher than roughly 80 percent of office workers. Beyond that, the ratings declined. The researchers suggest the “ideal” IQ could be higher or lower in various fields, depending on whether technical versus social skills are more valued in a given work culture. “It’s an interesting and thoughtful paper,” says Paul Sackett, a management professor at University of Minnesota, who was not involved in the research. “To me, the right interpretation of the work would be that it highlights a need to understand what high-IQ leaders do that leads to lower perceptions by followers,” he says. “The wrong interpretation would be, ‘Don’t hire high-IQ leaders.’ ”