choice (Kuhnen and Knutson, 2005). More generally, previous studies have documented striking individual differences in the efficiency of cognitive control (Fan et al., 2002), which is necessary for self-regulation in rewarding situations. In fact, the ability to direct attention away from rewarding stimuli during a delay of gratification task in toddlers predicts cognitive control later in life (Eigsti et al., 2006). Together, these studies underscore the importance of taking into consideration individual differences in experience, behavior and neural activation when examining complex brain-behavior operations such as reward processing in developmental populations. In a recent study (Galván et al., 2007), we examined individual differences to help disentangle the complexities that underlie increased vulnerability in some individuals to reward-driven behaviors and negative outcomes, such as addiction. Our approach was to examine the association between activity in reward-related neural circuitry in anticipation of a large monetary reward with personality trait measures of risk-taking and impulsivity in adolescence. fMRI scans and anonymous self-report rating scales of risky behavior, risk perception and impulsivity were acquired in individuals between the ages of 7 and 29 years. The main finding was that there was a positive association between NAcc activity and the likelihood of engaging in risky
