During the eighties and nineties, researchers in cognitive, developmental and social psychology became increasingly interested in the ecological approach to visual perception proposed by James J. Gibson (1950, 1966, 1979). This approach is founded on the concepts of direct perception and affordances. The goal of this paper is to justify, from a theoretical point of view, the extension of the affordance concept to the field of cognition, especially social cognition. In the first part, we set out the broad outlines of the ecological approach to perception, its origins and basic concepts, as well as some theoretical and empirical studies based upon this approach in developmental psychology. The second part deals with the extension of the ecological approach to social cognition. First, we state four principles of the ecological approach to social perception as formulated by Me Arthur and Baron (1983), and then review the empirical research conducted by defenders of the ecological position. Finally, we present arguments in favour of the extension of the affordance concept to the field of cognition. The concluding sections are devoted to the conception of personality traits as affordances and the summary of empirical evidence supporting this view. The implications of an ecological conception of personality traits are discussed.