Why are trait extraversion and extraverted behaviors both associated with greater positive affect? Across 3 studies, we examined whether 2 aspects of social experience-perceived social contribution and social power-mediate the relation between extraversion and positive affect. Study 1 (N = 205) showed that trait measures of social contribution and power mediated the relation between trait extraversion and trait positive affect. Study 2 (N = 78) showed that state social contribution and power helped to explain the greater levels of state positive affect reported by participants who were instructed to enact extraverted behaviors. Finally, Study 3 (N = 62) showed that social contribution and power mediated the relation between natural fluctuations in extraverted behavior and positive affect states in daily life. In all 3 studies, multiple-mediator models showed that social contribution, but not power, independently mediated the relations that trait and state extraversion had with positive affect. This suggests that perceptions of positive influence-more so than a general sense of power-help to explain why extraverts and extraverted moments are happier. We link these findings to emerging trends in the study of personality dynamics and the potential benefits of acting "out of character."