Economics is built on one simple assumption—that individual behavior can best be predicted by assuming that each individual will take the actions that best achieve his objectives. The reason for that assumption, usually and somewhat misleading labelled “rationality,” is that although individuals are in part irrational we have no good theory of mistakes, no way of predicting what particular irrational action they will take, hence it is the rational element in behavior that can be used to predict it.
Evolutionary psychology offers a challenge to the rationality assumption, since it provides us with a theory of mistakes. In this essay I sketch out the nature of that theory, describe some puzzles that economics has a difficult time explaining, and try to show how modifying economics with the aid of evolutionary psychology might help explain them.
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