During adolescence social-interactions with other people become more relevant. One key aspect of these interactions is cooperative behavior. Cooperation relies on a set of cognitive and affective mechanisms. In this study, we focused on the mental ability to feel happy for another person’s positive experience, called vicarious joy. We investigated the neural mechanisms of this ability using a false-choice vicarious reward fMRI task. Participants played a game where they could win monetary rewards for themselves, their mother, their father, and a stranger. A region-of-interest (ROI) analysis of the Nucleus Accumbens revealed robust activation in this region for personal reward as well as vicarious rewards for both parents. Vicarious reward for a stranger was not associated with activation within the Nucleus Accumbens. ROI activation was associated with self-reported vicarious joy for mother and father. A Prisoner’s Dilemma game outside the scanner showed an increase in cooperative behavior until age 14 for parents and strangers, followed by a decline for the stranger but not for the parents. Together, these findings demonstrate that adolescence is an important time for developing ingroup-outgroup relations.

在青春期，与他人的社交互动变得更加重要。这些互动的一个关键方面是合作行为。合作依赖于一套认知和情感机制。在这项研究中，我们专注于为他人的积极体验感到快乐的心理能力，称为替代快乐。我们使用错误选择替代奖励 fMRI 任务研究了这种能力的神经机制。参与者玩了一个游戏，他们可以为自己、他们的母亲、他们的父亲和一个陌生人赢得金钱奖励。伏隔核的感兴趣区域 (ROI) 分析揭示了该区域对个人奖励以及对父母双方的替代奖励的强烈激活。对陌生人的替代奖励与伏隔核内的激活无关。ROI 激活与父母自我报告的替代快乐有关。扫描仪外的囚徒困境游戏显示，父母和陌生人的合作行为在 14 岁之前有所增加，随后陌生人的合作行为有所下降，但父母没有。总之，这些发现表明，青春期是发展内群体-外群体关系的重要时期。