Limbic-based ?bottom-up? systems characterized by heightened reactivity to motivational stimuli and rewards mature rapidly from early adolescence, while prefrontally-organized ?top-down? systems that enable more effective cognitive control and judgment mature more slowly (Casey & Jones, 2010). This mismatch has been proposed as a key contributor to health risk behavior among adolescents, which is of critical importance because: (1) risk behaviors are the leading cause of morbidity and mortality in this age group, including diseases arising from unprotected sexual activity and casualties arising from reckless behavior (including driving fatalities and serious injuries); (2) it is the peak age for the onset of a wide range of risk behavior patterns with potential long-term consequences, including substance use and abuse, and delinquency. The developmental maturity mismatch hypothesis, however, has not been directly tested in relation to risk behavior at a level sufficient to inform this critical health area (Pfeifer & Allen, 2012). The primary aim of the proposed research is to understand the behavioral, cognitive, and neural bases of risk taking, through integrated analyses of age differences, developmental trajectories, and individual differences in psychosocial, neurocognitive and neural imaging assessments.