This groundbreaking book gives a fascinating account of how people really make decisions under real-world conditions. It provides a new, more psychologically plausible notion of rationality that is based on heuristics--simple rules for making decisions using realistic mental resources. It looks at when and how such simple heuristics work, compares decisions based on single and multiple reasons, and describes the benefits in some situations of having only limited knowledge. Simple Heuristics shows how heuristics can yield adaptive decisions in situations as varied as choosing a mate, dividing resources among offspring, predicting high school drop-out rates, and playing the stock market. Researchers in cognitive psychology, evolutionary psychology, and cognitive science, as well as economics and artificial intelligence, will find this book both useful and thought provoking.