Proceedings of the Annual Meeting of the Cognitive Science Society

When does a reasoner respond that ”no valid conclusion” (NVC)follows in a syllogistic reasoning task? Cognitive theories aim totrace it back to theory specific inference processes. In contrast,systemic theories explain it by depleted cognitive resources amongothers. This paper investigates possible theories to explain NVCresponses in an experiment with 139 participants. Using mixedmodels we analyze the association of NVC responses with reactiontimes, the validity as well as the entropy of a syllogism, and howNVC responses change over time. As expected, the number ofNVC responses is lower than logically expected, participantsrespond NVC more often for invalid syllogisms, and the likelihoodto respond NVC increases over the time-course of the experiment.Surprisingly, however, only for valid syllogisms, are the entropyand the RTs associated with NVC responses. Consequently,for invalid syllogisms, NVC responses seem to be generateddifferently as compared to valid ones.