The goal of the present research was to clarify conceptual issues in the assessment of effortful control in children and to examine the role of effortful control in the development of internalizing behaviors. Effortful control was assessed through both inhibition and activation components. Differential patterns of these abilities were examined in relation to subsequent internalizing problems. Furthermore, social competence was examined as a possible mechanism through which effortful control may influence internalizing behaviors. Children were assessed at 4-, 5.5- and 7.5-years on measures of inhibition/activation, social competence and internalizing behaviors. Results showed main effects for inhibition and activation on internalizing behaviors and supported a main effect for activation ability on kindergarten social competence ratings. Implications for future research examining effortful control and social and emotional outcomes were discussed
