Rational Learning and Partisan Attitudes

Theory: Characterizing voters as rational actors who update their party affiliations based on a Bayesian assimilation of new information, Achen (1992) showed that a revisionist model of party identification generates, among its empirical implications, stable partisanship among adults. The model further implies that susceptibility to partisan change declines with age. The significance of Achen's model for the study of party identification leads us to examine more closely its underlying assumptions and the empirical ramifications of this and other learning models. Method: This essay develops a more general learning model, based upon the Kalman filter, that encompasses the Achen model as a special case. Results: We show that the Achen assumption of a fixed party benefit level leads to implausible implications about how voters learn from the history of party performance. When party benefit levels are allowed to vary over time, models of voter learning no longer imply that partisan attitudes, even among the older segments of the population, remain stable in the wake of new information about the parties. We conclude by discussing the empirical viability of our revised learning model and its implications for the study of partisan attitudes.