The Suppression Task Revisited Vidhi Trehan, Aude Laloi, Richard van Hoolwerff, Gideon Borensztajn, Gal Moas Abstract: The apparent inconsistency of subjects’ answers in logical reasoning tasks, along with the fact that these answers do not comply with those predicted by classical logic, has been used to argue that human reasoning can not be described adequately by any logical formalism. In particular, Byrne devised a logical experiment, the suppression task, in which subjects seem to suppress valid logic inferences when additional premisses are added. She concludes that human reasoning is governed by the mental models theory of Johnson-Laird. However, closer analysis of the suppression task reveals subtle differences between the logical forms of the subtasks, which were presumed to be equivalent. A Closed World Reasoning (CWR) interpretation may account for the perceived suppression patterns. Byrne’s experimental design restricted the permitted answers to a fixed set. This set excluded a possible interpretation of the premise which we call “strengthening”, and thus may have distorted her results on suppression. The current research replicated Byrne’s experiment, but allowed for open answers. Most of the subjects’ answering patterns were found to match those predicted by CWR with strengthening.