The four-card problem and the generality of formal reasoning

Three experiments were designed to investigate the failure of intelligent adults to solve an apparently simple problem of formal reasoning devised by Wason. Both the mode of presentation and the type of material reduced the difficulty of the problem, while retaining its essential form. However, success on the original problem remained at a low level, even when subjects had attempted an easier version and had been given an explanation. These results enable one to reject a “strong” formulation of Piaget's theory of formal reasoning. A “weaker” formulation is suggested as a basis for further research.