Proceedings of the Annual Meeting of the Cognitive Science Society

Studies of how evidence affects beliefs sometimes show be-lief polarization in response to mixed evidence. However, thenature of the mental processes leading to change in opinion isup for debate. Different accounts of how people process evi-dence and then update their beliefs make different predictions,especially about one-sided evidence, which is rarely examined.We presented subjects with multiple text arguments regardingsocio-political topics as one-sided or mixed evidence. Partici-pants rated arguments differently according to their extant be-liefs, which is consistent with accounts of motivated reason-ing. They did not polarize afterward, instead showing evi-dence of belief updating according to Bayesian principles: be-lief change is sensitive to prior opinions and to the directionand quality of the evidence presented. These data support re-thinking some of the mental processes underlying incorpora-tion of evidence into a personal belief structure.