Illusions in quantified reasoning: How to make the impossible seem possible, and vice versa

The mental model theory postulates that reasoners build models of the situa tions described in premises, and that these models normally represent only what is true. The theory has an unexpected consequence. It predicts the exi stence of illusions in inferences. Certain inferences should have compellin g but erroneous conclusions. Two experiments corroborated the occurrence of such illusions in inferences about what is possible from disjunctions of q uantified assertions, such as, "at least some of the plastic beads are not red." Experiment I showed that participants erroneously inferred that impos sible situations were possible, and that possible situations were impossibl e, but that they performed well with control problems based on the same pre mises. Experiment 2 corroborated these findings in inferences from assertio ns based on dyadic relations, such as, "all the boys played with the girls. ".