Consequences for peers differentially bias computations about risk across development

Adolescents routinely take risks that impact the well-being of the friends they are with. However, it remains unclear when and how consequences for friends factor into decisions to take risks. Here we used an economic decision-making task to test whether risky choices are guided by the positive and negative consequences they promise for peers. Across a large developmental sample of participants ages 12-25, we show that risky decision computations increasingly assimilate friends' outcomes throughout adolescence into early adulthood in an asymmetric manner that overemphasizes protecting friends from incurring loss. Whereas adults accommodated friend outcomes to a greater degree when the friend was present and witnessing these choices, adolescents did so regardless of whether a friend could witness their decisions, highlighting the fundamentality of adolescent social motivations. By demonstrating that outcomes for another individual can powerfully tune an actor's risk tolerance, these results identify a key factor underlying peer-related motivations for risky behavior, with implications for the law and risk-prevention.