Mental models and deduction

According to the mental-model theory of deductive reasoning, reasoners use the meanings of assertions together with general knowledge to construct men tal models of the possibilities compatible with the premises. Each model re presents what is true in a possibility. A conclusion is held to be valid if it holds in all the models of the premises. Recent evidence described here shows that the fewer models an inference calls for, the easier the inferen ce is. Errors arise because reasoners fail to consider all possible models, and because models do not normally represent what is false, even though re asoners can construct counterexamples to refute invalid conclusions.