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Rapid and persistent neural representations differentiate crowd vs. individual faces: an magnetoencephalography (MEG) study

Poster Session F - Tuesday, March 10, 2026, 8:00 – 10:00 am PDT, Fairview/Kitsilano Ballroom

Enda Tan¹ (), Kestutis Kveraga^2,3, Hee Yeon Im¹; ¹University of British Columbia, ²Massachusetts General Hospital, ³Harvard Medical School

Reading the “mood of a crowd” is essential for adaptive social behavior, from avoiding threats to navigating everyday interactions. Prior work suggests that processing emotional information in crowds versus individual faces engages distinct neural pathways, with earlier dorsal-stream activation for crowds and later ventral-stream activation for single faces. However, it remains unclear how representations of crowds versus individuals unfold relative to other facial dimensions (e.g., sex) and whether these neural representations predict behavior. Using time-resolved representational similarity analysis (RSA) of MEG data, we examined how the brain encodes different types of social information from facial crowds and individual faces. Adult participants (N = 44) viewed either two crowds (four faces each) or two individual faces presented bilaterally, with one side displaying angrier or happier expressions and the other neutral. Participants indicated which crowd or person they would avoid. Whole-brain RSA revealed that the brain discriminated crowds from individual faces as early as 110 ms post-stimulus, comparable to the latency for recognizing facial sex, indicating that distinguishing crowds from individuals is an early and fundamental perceptual process. This distinction continued to explain the largest variance in neural time courses, whereas sex-related effects plateaued rapidly, suggesting sustained engagement of crowd-versus-individual representations during the task. The strength of this distinction correlated with behavioral accuracy in avoiding the angrier side (r=.40, p <.05), underscoring its functional relevance for adaptive social-emotional decisions. These findings demonstrate that neural encoding of facial crowds emerges rapidly, persists throughout processing, and predicts behavioral performance in social-emotional decision-making.

Topic Area: EMOTION & SOCIAL: Person perception