Belief bias is the tendency for prior beliefs to influence people's deductive reasoning in two ways: through the application of a simple belief-heuristic and through the application of more effortful reasoning for unbelievable conclusions. Previous research indicates that cognitive ability is the primary determinant of the effect of beliefs on accuracy. In the current study, we show that the mere tendency to engage analytic reasoning is responsible for the effect of cognitive ability on motivated reasoning. The implications of this finding (...) for our understanding of the impact of individual differences on belief bias are discussed. (shrink)