Wason´s selection task: Content effect, instruction effect or both?

This paper was presented at the THIRD INTERNATIONAL CONFERENCE ON THINKING. British Psychological Society. Cognitive Psychology Section. University College London. August, 1996"This experiment explores the effect of the scenario’s availability, instruction (true/false vs. violation) and presentation order on performance in different versions of Wason’s selection task. Each subject was given three problems corresponding to the content of the three different rules (abstract content, thematic-permission and thematic-norm). The main analyses are presented in terms of matching and logical index (Pollard and Evans, 1987). The matching and logical index were influenced by the contents of the rules. Also there exist an interaction between instructions and content in the logical index. In the abstract version, as in the thematic-obligation, the logical indices are superior on the individuals that receive violation instructions, whilst that in the thematic-permission the best performance was registered with true/false instructions. The results are not consistent with syntactic theories of human reasoning, and are discussed in terms of pragmatic and semantic theories of human reasoning