At every point in the lifespan, individual difference and a sense of control are strong predictors of motivation, coping, and success and failure in a wide range of life domains. What are the origins of these individual differences, how do they develop, and what are the mechanisms by which they exert such influence on psychological functioning? This book draws on theories and research covering key control constructs, including self-efficacy, learned helplessness, locus of control, and attribution theory. It also discusses such issues as the origins of control in social interactions, environmental features that promote or undermine control, developmental change in the mechanisms by which experiences of control have their effects on action, and the implications for intervening into the competence system, including interventions for people in uncontrollable circumstances.