The presence of peers increases risk taking among adolescents but not adults. We posited that the presence of peers may promote adolescent risk taking by sensitizing brain regions associated with the anticipation of potential rewards. Using fMRI, we measured brain activity in adolescents, young adults, and adults as they made decisions in a simulated driving task. Participants completed one task block while alone, and one block while their performance was observed by peers in an adjacent room. During peer observation blocks, adolescents selectively demonstrated greater activation in reward-related brain regions, including the ventral striatum and orbitofrontal cortex, and activity in these regions predicted subsequent risk taking. Brain areas associated with cognitive control were less strongly recruited by adolescents than adults, but activity in the cognitive control system did not vary with social context. Results suggest that the presence of peers increases adolescent risk taking by heightening sensitivity to the potential reward value of risky decisions.

Age differences in future orientation are examined in a sample of 935 individuals between 10 and 30 years using a delay discounting task as well as a new self-report measure. Younger adolescents consistently demonstrate a weaker orientation to the future than do individuals aged 16 and older, as reflected in their greater willingness to accept a smaller reward delivered sooner than a larger one that is delayed, and in their characterizations of themselves as less concerned about the future and less likely to anticipate the consequences of their decisions. Planning ahead, in contrast, continues to develop into young adulthood. Future studies should distinguish between future orientation and impulse control, which may have different neural underpinnings and follow different developmental timetables.

Adolescents take more risks in the presence of their peers, but the mechanism through which peer presence affects risky decision‐making is unknown. We propose that the presence of peers increases the salience of the immediate rewards of a risky choice. The current study examined the effect of peer presence on reward sensitivity in a sample of 100 late adolescents ages 18 through 20 (M=18.5) using a delay discounting task, which assesses an individual's preference for immediate versus delayed rewards. Participants were randomly assigned to complete the task alone or with 2 same‐age, same‐sex peers observing. Consistent with our prediction, adolescents demonstrated a greater preference for immediate rewards when with their peers than when alone. Heightened risk taking by adolescents in the company of their friends may be due in part to the effect that being with one's peers has on reward sensitivity.