Woojeong Lee¹, Hyeri Yoh¹, Sang Chul Chong¹; ¹Yonsei University

Judging the overall emotion of a crowd is essential for effective social interaction. While previous studies showed that people rapidly judge ensemble emotion based on facial expressions, real-world contexts such as background information and the observer's own emotional state have not been explored. To understand how each observer integrates these sources of information, this study investigated how facial expressions, background emotion, and observer mood influence ensemble emotion perception using naturalistic photographs. In Experiment 1, 10 participants judged the overall emotion of scenes containing crowd figures superimposed on positive, negative, or neutral backgrounds. Facial emotions were evaluated using DeepFace, and background emotions were rated in a pilot survey. Bayesian generalized linear mixed-effects models revealed robust main effects of both facial emotion and background emotion on ensemble judgments. Positive and negative backgrounds shifted ratings in their respective directions relative to neutral backgrounds. Model comparisons strongly favored the full model including interactions. However, interaction terms showed little evidence, suggesting that background emotion primarily influences the overall bias in ensemble judgments. Experiment 2 (N = 43) examined whether the observer's own emotional state further influences these judgments. Participants completed an autobiographical recall task to induce either a positive or a negative mood before judging scenes with positive or negative backgrounds. Results replicated the strong main effects of facial and background emotion from Experiment 1. While the observer's mood showed no main effect, model comparisons revealed a notable interaction with background emotion, suggesting internal emotional states may modulate ensemble perception. Together, these findings demonstrate that emotion ensemble perception integrates multiple sources of information beyond facial expressions. Specifically, contexts substantially influence how we perceive the collective mood in social scenes, underscoring the importance of studying ensemble perception in naturalistic settings that reflect the complexity of our environments.

Acknowledgements: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT)(RS-2022-NR070542).