Bounded Rationality : The Adaptive Toolbox edited

It is a curious feature of 20-century academia that the branch of mathematics known as rational choice theory led two of the most influential approaches to human behaviour to make completely different assumptions about the workings of the human mind. Biologists use rational choice theory to model the effects of natural selection on populations of genes. For a given range of alleles and their phenotypes, natural selection will 'choose' the ones that replicate best. Equipped with this benchmark, biologists can proceed to the field to test whether the design of organisms comes anywhere close. Under this view, organisms are seen as collections of phenotypic effects -effects that can be described in terms of strategies or decision-rules: Do X; If A, then do B; If C is greater than D, then do E... and so on. Individual behaviour consists of the execution of these decision rules. In other words, natural selection attempts to optimise the design of organisms; the organisms themselves don't try to optimise anything, they merely execute the decision rules of which they are composed. Given the problem of choosing where to forage or with whom to mate -problems that have a very large number of possible solutions -the biologist expects natural selection to have fashioned an efficient 'research strategy' that asks the most revealing questions of the world in order to arrive at an acceptable solution in the shortest possible time. Like a game of twenty questions, the winner is the one that arrives at the 'right' answer with the fewest yes-no questions. Economists, meanwhile, use rational choice theory to model what goes on in an individual's head. For a given range of behavioural options, individuals choose the one that they calculate will maximise their utility. Choosing habitats or mates involves, or should involve, compiling as much information about as many available options as possible, performing some sophisticated number-crunching, and plumping for the utility-maximising outcome. (Most economists would admit that this 'rational actor' model is only convenient shorthand and was never intended as a realistic theory of human psychology. Nevertheless, the model is taken seriously enough for altruism and irrationality to constitute anomalies or problems for the model.) Enter Gerd Gigerenzer who, for the past decade, has been developing the biological model of 'reasoning' in the hope of weaning