Evolutionary Versus Instrumental Goals: How Evolutionary Psychology Misconceives Human Rationality

An important research tradition in the cognitive psychology of reasoning-called the heuristics and biases approach-has firmly established that people's responses often deviate from the performance considered normative on many reasoning tasks. For example, people assess probabilities incorrectly, they display confirmation bias, they test hypotheses inefficiently, they violate the axioms of utility theory, they do not properly calibrate degrees of belief, they overproject their own opinions onto others, they display illogical framing effects, they uneconomically honor sunk costs, they allow prior knowledge to become implicated in deductive reasoning, and they display numerous other information processing biases (for summaries of the large literature, see It has been common for these empirical demonstrations of a gap between descriptive and normative models of reasoning and decision making to be taken as indications that systematic irrationalities characterize human cognition. However, over the last decade, an alternative interpretation of these findings has been championed by various evolutionary psychologists, They have reinterpreted the modal response in most of the classic heuristics and biases experiments as indicating an optimal information processing adaptation on the part of the subjects. It is argued by these investigators that the research in the heuristics and biases tradition has not demonstrated human irrationality at all and that a Panglossian position (see Stanovich & West, 2000) which assumes perfect human rationality is the proper default position to take. It will be argued in this chapter that although the work of the evolutionary psychologists has uncovered some fundamentally important things about human cognition, these theorists have misconstrued the nature of human rationality and have conflated important distinctions in this domain. What these theorists have missed (or failed to sufficiently emphasize) is that definitions of rationality must coincide with the level of the entity whose optimization is at issue. This admonition plays out most directly in the distinction between evolutionary rationality and instrumental