Illusions in modal reasoning

According to the mental model theory, models represent what is true, but no t what is false. One unexpected consequence is that certain inferences shou ld have compelling, but invalid, conclusions. Three experiments corroborate d the occurrence of such illusions in reasoning about possibilities. When p roblems had the heading "Only one of the premises is true," the participant s considered the truth of each premise in turn, but neglected the fact that when one premise is true, the others are false. When two-premise problems had the heading "One of the premises is true and one is false," the partici pants still neglected the falsity of one of the premises. As predicted, how ever, the illusions were reduced when reasoners were told to check their co nclusions against the constraint that only one of the premises was true. We discuss alternative explanations for illusory inferences and their implica tions for current theories of reasoning.