  In response to this worry, theorists try to derive replicator dynamics from models of individual adaptive behavior. Some models posit that people tend to imitate the behavior of others, based either on how popular or how successful that behavior seems. Other models posit some kind of reinforcement mechanism. Neither approach accords very well with the traditional preference among both philosophers and economists for rational explanations. Samuelson (1997, p. 23) responds that such approaches may nevertheless be appropriate “if we are interested in people, rather than ideally rational agents.” But it is hardly obvious that our best cognitive science of actual human psychology will eschew rational explanation in favor of the psychological mechanisms currently being invoked to underwrite replicator dynamics.