ABSTRACT
A major point of contention about human reasoning is whether or not individuals search for counterexamples to conclusions. This theoretical account rests on the semantic principle of validity: a conclusion is valid if and only if it allows for no counterexamples, i.e., possibilities in which the premises are true but the conclusion is false. Hence, by constructing a counterexample, reasoners are able to know that an inference is invalid. In the case of syllogisms, Polk and Newell have defended an account in terms of models, but argued that their explanation of individual differences gains little, if anything, by postulating a search for counterexamples. Bucciarelli and Johnson-Laird have shown that people are able to search for counterexamples if prompted to do so. To search for a search for counterexamples, authors carried out an experiment in which the participants had to evaluate eight inferences based on non-standard quantifiers.
