The Heuristics and Biases approach to judgment under uncertainty began 40 years ago with the publication of a study of the statistical foibles on the part of research psychologists and statisticians (Tversky & Kahneman, 1971). Since then, this research program has substantially influenced the working assumptions of psychologists and economists about the role of normative models of probability judgment and decision making, while providing a new language of judgmental heuristics. We provide a historical overview of the Heuristics and Biases research program that describes its intellectual antecedents and the special role of the rational actor model in shaping its methods, and we review the program's evolution over the course of three waves of research and theory development.