The social world of young children primarily revolves around parents and caregivers, who play a key role in guiding children’s social and cognitive development. However, a hallmark of adolescence is a shift in orientation towards nonfamilial social targets, an adaptive process that prepares adolescents for their independence. Little is known regarding neurobiological signatures underlying changes in adolescents’ social orientation. Using functional brain imaging of human voice processing in children and adolescents (ages 7-16), we demonstrate distinct neural signatures for mother’s voice and nonfamilial voices across child and adolescent development in reward and social valuation systems, instantiated in nucleus accumbens and ventromedial prefrontal cortex. While younger children showed increased activity in these brain systems for mother’s voice compared to nonfamilial voices, older adolescents showed the opposite effect with increased activity for nonfamilial compared to mother’s voice. Findings uncover ...