Social brain responses to natural scene images of social interactions

Recent research reveals that human occipitotemporal 'social brain' regions that are selective for images of individual faces and bodies are also sensitive to visual cues of social interaction. Earlier studies mainly contrasted observing dyadic interactions with non-interactive controls, emphasizing the interacting/non-interacting distinction to observers, and lacking the variety seen in natural settings. To address these limitations, we analysed a 7 T fMRI data set in which participants viewed many naturalistic images while performing a memory task. We focused on 182 scenes containing at least two individuals, and used localizers to identify face- and body-selective regions of interest (ROIs). Brain responses to each image were measured, and the depiction of social interaction was rated by independent observers. Control measures were gathered, per image, for the number of people, their surface area and distribution, and their implied animatedness. Linear and generalized additive modelling revealed that social interaction predicted a greater BOLD response in all ROIs, beyond the effects of the control variables. Face- and body-selective regions in both hemispheres showed heightened sensitivity to social interaction in natural scenes, even during an orthogonal task. These findings expand our understanding of 'social vision' areas beyond individual person perception to include multi-person social interactions.