Physiological Encoding of Social Evaluation: Modeling Eye Movements, Pupillary, and Neuronal Responses to Faces

Face-based social evaluations are ubiquitous and consequential. These evaluations are organized along two fundamental dimensions: valence (positive versus negative intentions) and power (high versus low social influence). However, how these dimensions manifest in spontaneous physiological responses remains unclear. Across three studies (96 participants and 506 single neurons), we used data-driven modeling to identify dimension-specific physiological signatures. Positive evaluations along the valence dimension were encoded by pupillary constriction and decreased neural activity in both amygdala and hippocampus. Amygdalar suppression was feature-specific, emerging only during mouth fixations, whereas the hippocampus exhibited feature-invariant suppression across all fixations. Power evaluations were encoded by pupil dilation, prolonged eye-region fixations, and increased hippocampal activity. Furthermore, social anxiety selectively heightened the sensitivity of pupillary responses to valence but did not affect power encoding. This selective modulation confirms that these responses are driven by high-level social computations rather than reflexive reactions to low-level visual features. Our findings demonstrate how the fundamental dimensions of social evaluation are embodied across multiple physiological systems within moments of viewing a face.