New, 21st anniversary edition, with a new foreword by Ben Goldacre, author of Bad Science and Bad Pharma, and an afterword by James Ball, covering developments in our understanding of irrationality over the last two decades. Why do doctors, army generals, high-ranking government officials and other people in positions of power make bad decisions that cause harm to others? Why do prizes serve no useful function? Why are punishments so ineffective? Why is interviewing such an unsatisfactory method of selection? Irrationality is a challenging and thought-provoking book that draws on statistical concepts, probability theory and a mass of intriguing research to expose the failings of human reasoning, judgement and intuition. The author explores the inconsistencies of human behaviour, and discovers why even the experts find it so hard to make rational and unbiased decisions. Written with clarity and occasional flashes of wry humour, this classic volume is just as relevant today as when it was first written twenty-one years ago.