In choices under incomplete information on incumbents, consumers with stronger preferences are more likely to reinforce their prior choices with motivated reasoning. However, in situations where incomplete information is restricted only to the prior choice, consumers with stronger preferences are more likely to abandon, not reinforce, their prior choices due to cognitive dissonance. Here, we consider how cognitive ability and personality traits mediate such interplay between motivated reasoning and cognitive dissonance. We set an experiment to show that consumers with a stronger System 2 are more likely to engage in motivated reasoning to reinforce the prior choice and thus suffer less cognitive dissonance. Cognitive dissonance can, however, overcome motivated reasoning for those cognitively poor consumers who are more emotional, less humble, less extraverted and less conscientious.