Patricia Rich

Information cascades are troubling and well studied because apparently individually rational responses to evidence can lead entire communities to conform (participate in cascades), and hence to converge on the wrong answer. Yet existing theory cannot explain why a robust, substantial minority of people in experimental studies do not conform. Groups achieve improved reliability thanks to these non-conformists. I use simulations to study cascade problems in an evolutionary setting. The results show that although conforming maximizes expected fitness, non-conformists can persist and often flourish in the population. The reason is that by its nature, conformity carries an evolutionary cost.

There are two prominent viewpoints regarding the nature of rationality and how it should be evaluated in situations of interest: the traditional axiomatic approach and the newer ecological rationality. An obstacle to comparing and evaluating these seemingly opposite approaches is that they employ different language and formalisms, ask different questions, and are at different stages of development. I adapt a formal framework known as SCOP to address this problem by providing a comprehensive common framework in which both approaches may be defined and compared. The main result is that the axiomatic and ecological approaches are in far greater agreement on fundamental issues than has been appreciated; this is supported by a pair of theorems to the effect that they will make accordant rationality judgements when forced to evaluate the same situation. I conclude that ecological rationality has some subtle advantages, but that we should move past the issues currently dominating the discussion of rationality.