The Ensemble Perception of Crowd Facial Expressions: Emotional Valence Effect and Temporal Dynamics-An ERP Study.

Ensemble perception enables observers to rapidly extract the mean emotion from a crowd of faces, yet its neural mechanisms remain unclear. Combining behavioral measures, event-related potentials (ERPs), and multivariate pattern analysis (MVPA), we investigated the temporal dynamics of crowd emotion perception and the moderating role of emotional valence. At the behavioral level, we observed a happiness superiority effect in recognition accuracy and speed. At the neural level, MVPA revealed respective neural representations for crowd versus individual face processing. ERP results further delineated three potential stages: initial feature encoding and integration, followed by configural processing and valence differentiation, and finally mean emotion extraction and decision formation. These findings provide a neurochronometric framework for ensemble perception of crowd emotions, advancing understanding of how the brain efficiently summarizes collective affective signals.