Conservatism in Belief Revision and Participant Skepticism

Comparing the responses of participants in reasoning experiments to the normative standard of Bayes’ Theorem has been a popular empirical approach for almost half a century. One longstanding finding is that people’s belief revision is conservative with respect to the normative prescriptions of Bayes’ Theorem, that is, beliefs are revised less than they should be. In this paper, we consider a novel explanation of conservatism, namely that participants do not perceive information provided to them in experiments as coming from a fully reliable source. From the Bayesian perspective, less reliable evidence should lead to more conservative belief revision. Thus, there may be less of discrepancy between normative predictions and behavioural data than previously assumed.