Ventral striatal activity mediates cultural differences in affiliative judgments of smiles

Abstract

Previous research demonstrates that European Americans judge excited (vs. calm) smiles as more affiliative (warm, friendly, extraverted) than do Chinese, and that these differences are in part due to European Americans valuing excitement, enthusiasm, and other high arousal positive states (HAP) more than Chinese. But what mechanisms underlie these differences? To answer this question, European Americans (n = 19) and Chinese (n = 19) viewed excited (vs. calm) targets and then rated targets’ leadership potential (or familiarity, as a control) while undergoing functional magnetic resonance imaging. After scanning, participants then rated the same targets in terms of basic social traits such as affiliation, dominance, and competence. Consistent with previous findings, European Americans rated excited (vs. calm) targets as more affiliative than did Chinese. As predicted, European Americans showed greater ventral striatal activity (VS; associated with anticipation of reward) as they began to rate the excited (vs. calm) targets than did Chinese, and cultural differences in affiliation judgments were mediated by these cultural differences in VS activity (but not by activity in the medial prefrontal cortex, insula, or amygdala). However, while the cultural difference in affiliation judgments was driven by European Americans rating the excited (vs. calm) targets as more affiliative; the cultural difference in VS activity was driven by the calm (vs. excited) targets eliciting greater VS activity among Chinese, which more closely matched the cultural differences in ideal affect observed in this sample. Consistent with Affect Valuation Theory, these findings suggest that affective responses mediate cultural differences in affiliative judgments.