Economics has paid little attention to the psychology of economic behaviour, leading to somewhat simplistic assumptions about human nature. The psychological aspects have typically been reduced to standard utility theory, based on a narrow conception of rationality and self-interest maximization. The contributions in this volume, some focused on analytical models and methodology, others on laboratory and field experiments, challenge these assumptions, and provide novel and complex understandings of human motivation and economic decision-making. With a pioneering introduction by the book's two editors, this volume brings together exciting contributions to a field that is rapidly growing in influence and reach.