EXPRESS: The joint attention grouping effect: Perceptual binding of observed social interactions

The visual system may perceptually process conspecifics more efficiently when they are interacting, versus not, to support social cognitive functions such as group detection. In three experiments, young adult university students were briefly shown dyads (upright or inverted) and made speeded judgments of whether they attended the same location (joint attention) or different locations (non-joint attention). Participants performed worse with inverted stimuli, but this inversion effect was smaller in joint attention conditions. These findings indicate perceptual grouping of joint attention dyads into a single perceptual unit. This joint attention grouping effect was evident when dyads looked towards spatial locations (Experiment 1), towards objects (Experiment 2), and for asymmetrically composed stimuli (Experiment 3). The effect was weaker for non-social directional stimuli (Experiment 1). These data support the idea that two interacting individuals are coded as one socially bound perceptual unit, supporting efficient and rapid social cognitive computations.