When Leslie John, an associate professor at Harvard Business School, arrived at work on the morning of the U.S. presidential election between Donald Trump and Hillary Clinton, she was worried. John is an expert in behavioral decision research and studies the various innate flaws and biases that impede human reasoning. As a supporter of Clinton, she wondered whether the same cognitive traps that she studies in a laboratory could be leading to overconfidence about the likelihood of a Clinton victory. “Everyone I spoke with pointed me to Democratic and Republican pollsters, financial and prediction markets, essentially every forecaster in the public record was predicting a Clinton win,” John says. “Yet here we are.”