Many birds provide parental care by following this rule: "Feed any small bird sitting in the nest in which you have laid your eggs." These birds do not need to recognize their own eggs and chicks in order to provide efficient care for their offspring. In an environment where the content of one's nest is almost bound to be one's own eggs and chicks, simple cognitive machinery that is less demanding than individual recognition can do the job. This is why the simplest decision-making mechanism has been selected in the course of evolution. In Gut Feelings, Gerd Gigerenzer (director of the Center for Adaptive Behavior and Cognition at the Max Plank Institute for Human Development in Berlin) sets himself the task of showing that the human mind is constructed in a similar way: it contains a collection of domain-specific cognitive mechanisms. Psychologists term these mechanisms ‘simple heuristics'. They consist in intuitive rules, such as, “Always do x when you find yourself in a situation of type y”, which have evolved because they happened to help humans cope successfully with particular aspects of their environment.