Internal uncertainty impacts social information use in risky choice across adolescence.

Adolescents are often thought to be more susceptible to social influence than people in other age groups. This is often explained by altered reward processing or heightened social motivations, such as a need to belong to a group during adolescence. However, uncertainty also makes people more susceptible to social information. While researchers agree that adolescence is a time of great uncertainty, the role of uncertainty in explaining susceptibility to social influence across development remains unclear. Here, we asked 166 participants aged 10-26 to make 144 risky decisions in a lottery experiment, either with or without observing social information and nested within conditions of low and high uncertainty. Modelling susceptibility to social influence as Bayesian updating suggests that despite the same levels of uncertainty between participants, their own internal uncertainty about the utility of choices underwent a negative linear age trend, contributing to age-related differences in susceptibility to social influence across adolescence. Our results suggest that the adolescent development of peer influence is at least in part driven by age differences in the internal uncertainty about how to decide.