Facial expressions of authenticity: Emotion variability increases judgments of trustworthiness and leadership.

People automatically generate first impressions from others' faces, even with limited time and information. Most research on social face evaluation focuses on static morphological features that are embedded "in the face" (e.g., overall average of facial features, masculinity/femininity, cues related to positivity/negativity, etc.). Here, we offer the first investigation of how variability in facial emotion affects social evaluations. Participants evaluated targets that, over time, displayed either high-variability or low-variability distributions of positive (happy) and/or negative (angry/fearful/sad) facial expressions, despite the overall averages of those facial features always being the same across conditions. We found that high-variability led to consistently positive perceptions of authenticity, and thereby, judgments of perceived happiness, trustworthiness, leadership, and team-member desirability. We found these effects were based specifically in variability in emotional displays (not intensity of emotion), and specifically increased the positivity of social judgments (not their extremity). Overall, people do not merely average or summarize over facial expressions to arrive at a judgment, but instead also draw inferences from the variability of those expressions.