The conventional theories in economics and politics contend that people act rationally. Elizabeth Kolbert reviews a pair of books that suggest that's not really the case.
Some of these heuristics were pretty obvious -- people tend to make inferences from their own experiences, so if they've recently seen a traffic accident they will overestimate the danger of dying in a car crash -- but others were more surprising, even downright wacky. For instance, Tversky and Kahneman asked subjects to estimate what proportion of African nations were members of the United Nations. They discovered that they could influence the subjects' responses by spinning a wheel of fortune in front of them to generate a random number: when a big number turned up, the estimates suddenly swelled.