Ventral striatal activity mediates cultural differences 4 in affiliative judgments of smiles 5

9 Abstract Previous research demonstrates that European Americans judge excited 10 (vs. calm) smiles as more affiliative (warm, friendly, extraverted) than do Chinese, 11 and that these differences are in part due to European Americans valuing excite12 ment, enthusiasm, and other high arousal positive states (HAP) more than Chinese. 13 But what mechanisms underlie these differences? To answer this question, Euro14 pean Americans (n = 19) and Chinese (n = 19) viewed excited (vs. calm) targets 15 and then rated targets’ leadership potential (or familiarity, as a control) while 16 undergoing functional magnetic resonance imaging. After scanning, participants 17 then rated the same targets in terms of basic social traits such as affiliation, dom18 inance, and competence. Consistent with previous findings, European Americans 19 rated excited (vs. calm) targets as more affiliative than did Chinese. As predicted, 20 European Americans showed greater ventral striatal activity (VS; associated with 21 anticipation of reward) as they began to rate the excited (vs. calm) targets than did 22 Chinese, and cultural differences in affiliation judgments were mediated by these 23 cultural differences in VS activity (but not by activity in the medial prefrontal 24 cortex, insula, or amygdala). However, while the cultural difference in affiliation 25 judgments was driven by European Americans rating the excited (vs. calm) targets 26 as more affiliative; the cultural difference in VS activity was driven by the calm (vs.