Adolescents' perceptions of parent and peer norms about externalizing behaviors influence the extent to which they adopt similar attitudes, yet little is known about how the trajectories of perceived parent and peer norms are related to trajectories of personal attitudes across adolescence. Neural development of midline regions implicated in self–other processing may underlie developmental changes in parent and peer influence. Here, we examined whether neural processing of perceived parent and peer norms in midline regions during self-evaluations would be associated with trajectories of personal attitudes about externalizing behaviors. Trajectories of adolescents' perceived parent and peer norms were examined longitudinally with functional neuroimaging ( n = 165; ages 11–16 years across three waves; 86 girls, 79 boys; 29.7% White, 21.8% Black, 35.8% Latinx, 12.7% other/multiracial). Behavioral results showed perceived parent norms were less permissive than adolescents' own attitudes about externalizing behaviors, whereas perceived peer norms were more permissive than adolescents' own attitudes, effects that increased from early to middle adolescence. Although younger adolescents reported less permissive attitudes when they spontaneously tracked perceived parent norms in the ventromedial and medial pFCs during self-evaluations, this effect weakened as they aged. No brain–behavior effects were found when tracking perceived peer norms. These findings elucidate how perceived parent and peer norms change in parallel with personal attitudes about externalizing behaviors from early to middle adolescence and underscore the importance of spontaneous neural tracking of perceived parent norms during self-evaluations for buffering permissive personal attitudes, particularly in early adolescence.

One feature of adolescence is a rise in risk-taking behaviors, whereby the consequences of adolescents' risky action often impact their immediate surrounding such as their peers and parents (vicarious risk taking). Yet, little is known about how vicarious risk taking develops, particularly depending on who the risk affects and the type of risky behavior. In a 3-wave longitudinal fMRI study, 173 adolescents completed 1–3 years of a risky decision-making task where they took risks to win money for their best friend and parent ( n with behavioral and fMRI data ranges from 139–144 and 100–116 participants, respectively, per wave). Results of this preregistered study suggest that adolescents did not differentially take adaptive (sensitivity to the expected value of reward during risk taking) and general (decision-making when the expected values of risk taking and staying safe are equivalent) risks for their best friend and parent from sixth to ninth grade. At the neural level, preregistered ROI analyses revealed no differences in the ventral striatum and ventromedial pFC during general nor adaptive risk taking for best friend versus parent over time. Furthermore, exploratory longitudinal whole-brain analyses revealed subthreshold differences between best friend and parent trajectories within regulatory regions during general vicarious risk taking and social-cognitive regions during adaptive vicarious risk taking. Our findings demonstrate that brain regions implicated in cognitive control and social-cognitive processes may distinguish behaviors involving peers and parents over time.