Smile and the world smiles (and trusts) with you: Happiness mimicry shapes first impressions.

Numerous studies have shown that the processes underlying trait judgments can be influenced by concurrent affect processing. The present project explores the role of emotional mimicry in trait attribution. Across three experiments, we asked participants to assess social characteristics of faces expressing happiness, sadness, and anger. In Experiments 1 and 3, we used facial electromyography to predict participants' inferences about trustworthiness, confidence, and attractiveness (Experiment 1) or their behaviorally assessed trust by asking participants to share virtual points in a "trust/investment game" (Experiment 3). In Experiment 2, we tested the causal relationship between facial activity and trait judgments. Participants were asked to assess trustworthiness while performing facial movements that either enhanced or inhibited muscle activity during mimicry of given emotional expressions. The results indicate that mimicry of happiness not only predicts but is causally linked to perceptions of trustworthiness-the stronger the imitation, the more positive the assessments. The results of Experiments 1 and 3 show that increased sadness mimicry is associated with lower trust ratings, although the results of Experiment 2 do not support a causal relationship. Additionally, we confirmed previous observations that people are more likely to mimic affiliative displays (i.e., happiness and sadness) than antagonistic ones (i.e., anger), with happiness being the most likely to be mimicked. In summary, these studies provide evidence that facial mimicry modulates social trait inferences and underscores the functional role of mimicry in social interactions. (PsycInfo Database Record (c) 2025 APA, all rights reserved).