In all three 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". Extraversion is one of five basic trait domains that describe the structure of personality (John, Naumann, & Soto, 2008), and can be defined as the tendency to be talkative, assertive, and sociable at the high end of the continuum, and quiet, passive, and reserved at the opposite ("introverted") end. The tendency for extraverts to experience higher levels of positive affect (PA) is often described as one of the most robust findings in personality psychology (Lucas & Fujita, 2000;Smillie, DeYoung, & Hall, 2015;Steel, Schmidt, & Shultz, 2008), and holds across several cultures (Lucas, Diener, Grob, Suh, & Shao, 2000). This relation is strongest when PA is defined, in line with Watson and Tellegen's (1985) factor model of affect, as the combination of pleasant valence and high activation (e.g., lively, excited; see Smillie, DeYoung, & Hall, 2015). Therefore, extraverts tend to be "happier"-a term we use as short-hand-in the sense that they experience higher levels of PA.The extraversion-PA relation also holds at the state level: individuals feel happier in the moments in which they behave in a more talkative and sociable way. Several experimental studies have provided causal evidence that participants who are instructed to act extraverted (e.g., talkative, bold, assertive) report higher levels of PA than those instructed to act introverted (e.g., quiet, passive, reserved) during interactive activities in the lab (Gallagher, Fleeson, & Hoyle, 2011;McNiel & Fleeson, 2006;McNiel, Lowman, & Fleeson, 2010;Smillie, Wilt, Kabbani, Garratt, & Revelle, 2015;Zelenski et al., 2013;Zelenski, Santoro, & Whelan, 2012) (Keyes, 1998) explained 32% of the relation between trait extraversion and PA. Of the five subscales, social contribution (believing that one has something valuable to give, and does give, to society) was the strongest mediator, independently explaining 29% of the trait extraversion-PA relation. To bolster this correlational study with experimental evidence, Smillie, Wilt, and colleagues (Study 2) then investigated whether state measures of social well-being and social contribution mediated the relation between enacted extraversion and increased PA. As a state measure of social contribution, participants reported the percentage to which they "contributed to the discussion tasks", relative to the other two participants. Mirroring the trait-level findings, single-mediator models showed that social well-being and social contribution both helped to explain the effect of acting extraverted on PA. However, social contribution again emerged as ...