Illusory Inferences about Embedded Disjunctions

The mental model theory of reasoning postulates that individuals construct mental models of the possibilities consistent with premises, and that these models represent what is true but not what is false. An unexpected consequence of this assumption is that certain premises should yield systematically invalid inferences. This prediction is unique amongst current theories of reasoning, because no alternative theory, whether based on formal rules of inference or on probabilistic considerations, can explain these illusory inferences. We report two studies of novel illusory inferences that depend on embedded disjunctions, e.g., premises of the form A or else (B or else C). The theory distinguishes between those embedded disjunctions that should yield illusions and those that should not. Experiment 1 corroborated this distinction. Experiment 2 extended the phenomena to a more controlled set of problems.