A Study of Thinking is a pioneering account of how human beings achieve a measure of rationality in spite of the constraints imposed by bias, limited attention and memory, and the risks of error imposed by pressures of time and ignorance. First published in 1956 and hailed at its appearance as a groundbreaking study, it is still read three decades later as a major contribution to our understanding of the mind. In their insightful new introduction, the authors relate the book to the cognitive revolution and its handmaiden, artificial intelligence.