Children's explanations of their performances are characterized by an increase of internal explanations over external ones. Originally considered a manifestation of cognitive development, this change has more recently been considered as an appropriation of a social norm. Two investigations are presented analyzing development of causal explanations ofsuccess and failure in mathematics and drawing. In the first study, two measures ofcausal attribution are compared in order to show that the use ofunipolar scales is more suitable for illustrating differences in causal factors progressively operated by children. The hypothesis ofthe appropriation ofa norm of internality is investigated in the second study. Results do not confirm this hypothesis and further, they cannot be interpreted solely in terms of cognitive development. They are discussed in the frame ofa theory ofsocio-cognitive development.In this research the development of children's explanations of their own achievements is investigated in order to analyze the combinations of normative and cognitive factors in the development of causal analysis. In this area, Weiner's model Weiner & Kukla, 1970;Weiner, Russell, & Lerman, 1978) has often been used as it permits researchers to test specific hypotheses derived from Kelley's theory (1972). This familiar model is based on the distinction between four causal factors organized along two dimensions: internal (effort, ability) versus external (task difficulty, luck) and stable (ability, task difficulty) versus unstable (effort, luck).We thank Nicole Dubois and two anonymous reviewers for their helpful comments on an earlier draft of this paper.