Proceedings of the Annual Meeting of the Cognitive Science Society

Theories of syllogistic reasoning based on Euler Circles have foundered on a combinatorial explosion caused by an inappropriate interpretation of the diagrams. A new interpretation is proposed, allowing single diagrams to abstract over multiple logical models of premises, permitting solution by a simple rule, which involves the identification of individuals whose existence is entailed by the premises. This solution method suggests a performance model. which predicts some of the phenomena of the Figural Effect, a tendency for subjects to prefer conclusions in which the terms preserve their grammatical status from the premises (Johnson-Laird k Steedman 1978). 21 students were asked to identify the necessary individuals for each of the 64 pairs of premis.'5e>. The order in which the three terms specifying the individuals were produced was shown to be as predicted by the performance model. but contrary to the presumed predictions of Mentad Models theory.