Shared and individual tuning curves for social vision.

A stimulus with light is clearly visual; a stimulus with sound is clearly auditory. But what makes a stimulus "social", and how do judgments of socialness differ across people? Here, we characterize both group-level and individual thresholds for perceiving the presence and nature of a social interaction. We take advantage of the fact that humans are primed to see social interactions-e.g., chasing, playing, fighting-even in very un-lifelike stimuli such as animations of geometric shapes. Unlike prior work using these stimuli, we exploit their most advantageous property, which is that their visual features are fully parameterizable. We use this property to construct psychophysics-inspired "social tuning curves" for individual subjects. Social tuning curves are stable within individuals, unique across individuals, and show some relationship to socio-affective traits. Results support the view that social information processing begins early in the perceptual hierarchy. Further, our approach lays the foundation for a generative account of social perception in single subjects.