Semantics as a foundation for psychology: a case study of Wason's selection task Keith Stenning, Michiel van Lambalgen Abstract: We review the various explanations that have been offered to account for subjects' behaviour in Wason's famous selection task. We argue that one element that is lacking is a good understanding of subjects' semantics for the key expressions involved, and an understanding of how this semantics is affected by the demands the task puts upon the subject's cognitive system. We make novel proposals in these terms for explaining the major content effects of deontic materials. Throughout we illustrate with excerpts from tutorial dialogues which motivate the kinds of analysis proposed. Our long term goal is an integration of the various insights about conditional reasoning on offer from different cognitive science methodologies. The purpose of this paper is to try to draw the attention of logicians and semanticists to this area, since we believe that empirical investigation of the cognitive processes involved could benefit from semantic analyses. Keyword(s): Conditionals, anaphora, psychology of reasoning, semantics