The Representation of Two-Body Shapes in the Human Visual Cortex

Human social nature has shaped visual perception. A signature of the relationship between vision and sociality is a particular visual sensitivity to social entities such as faces and bodies. We asked whether human vision also exhibits a special sensitivity to spatial relations that reliably correlate with social relations. In general, interacting people are more often situated face-to-face than back-to-back. Using functional MRI and behavioral measures in female and male human participants, we show that visual sensitivity to social stimuli extends to images including two bodies facing toward (vs away from) each other. In particular, the inferior lateral occipital cortex, which is involved in visual-object perception, is organized such that the inferior portion encodes the number of bodies (one vs two) and the superior portion is selectively sensitive to the spatial relation between bodies (facing vs nonfacing). Moreover, functionally localized, body-selective visual cortex responded to facing bodies more strongly than identical, but nonfacing, bodies. In this area, multivariate pattern analysis revealed an accurate representation of body dyads with sharpening of the representation of single-body postures in facing dyads, which demonstrates an effect of visual context on the perceptual analysis of a body. Finally, the cost of body inversion (upside-down rotation) on body recognition, a behavioral signature of a specialized mechanism for body perception, was larger for facing versus nonfacing dyads. Thus, spatial relations between multiple bodies are encoded in regions for body perception and affect the way in which bodies are processed.