Proceedings of the Annual Meeting of the Cognitive Science Society

Belief bias in syllogistic reasoning refers to the finding thatindividuals are more likely to accept believable than unbeliev-able conclusions independent of their logical validity. Mosttheories argue that belief bias is driven by differences in rea-soning processes between believable and unbelievable syllo-gisms. In contrast, Dube, Rotello, and Heit (2010) proposedthat belief bias is solely an effect of response processes. Weinvestigated belief bias without having to rely on response biasmanipulations (Klauer, Musch, and Naumer, 2000) or confi-dence ratings (Dube et al., 2010). Instead, we added a thirdresponse (“I don’t know”) to the usual binary response set(“Yes”/“No”). This allowed us to test belief bias with a fullyidentified multinomial processing tree model, in a hierarchicalBayesian framework. We found evidence that the belief biasis driven by differences in response processes. Evidence for adifference in reasoning processes was inconclusive.