Proceedings of the Annual Meeting of the Cognitive Science Society

“No Valid Conclusion” (NVC) is one of the most frequently se-lected responses in syllogistic reasoning experiments and cor-responds to the logically correct conclusion for 58% of thesyllogistic problem domain. Still, NVC is often neglected incomputational models or just treated as a byproduct of theunderlying inferential mechanisms such as a last resort whenthe search for alternatives is exhausted. We illustrate thatNVC represents a major shortcoming of current models for hu-man syllogistic reasoning. By introducing heuristic rules, wedemonstrate that slight extensions of the existing models resultin substantial improvements of their predictive performances.Our results illustrate the need for better NVC handling in cog-nitive modeling and provide directions for modelers on how tointegrate it into their approaches.