Although Dan Ariely is an academic by trade, he is a pragmatist at heart. The Duke professor and best-selling author brings his theories to light through practical applications and behavioral experiments, where irrationality is almost always certain. Ariely has written two books on the subject—The Upside of Irrationality and Predictably Irrational —and recently sat down with Olivier Sibony, a director in McKinsey’s Paris office, to share his insights into human behavior that can help companies make better decisions.