Shared and individual tuning curves for social perception

Stimuli with light are clearly visual; stimuli with sound are clearly auditory. But what makes a stimulus "social", and how do socialness judgments differ across people? Here, we characterize group-level and individual thresholds for perceiving the presence and nature of a social interaction. We leverage the fact that humans see social interactions—e.g., chasing, playing, fighting—even in very un-lifelike stimuli like animations of geometric shapes. Unlike most prior work that used hand-crafted stimuli, we exploit these animations’ most advantageous property: their visual features are fully parameterizable. Using this property, we construct psychophysics-inspired "social tuning curves" for individuals. We find not only that simple visual features influence social perception, but also that the exact shape of the tuning curve is unique to and stable within each person. Further, individual differences in tuning curves are related to socio-affective traits. Our approach lays the foundation to study how social percepts emerge from interactions between features of a stimulus and features of an individual observer.