Abstract

This study investigated whether viewpoint-dependent processing shown in a single face is also observed in a pair of faces. We measured an amount of the shape aftereffect using an adaptation paradigm. In Experiment 1, a pair of faces was used not only as an adaptation stimulus but also as a testing stimulus to find out whether the shape aftereffect was observed according to the relative direction of the pair of faces. As a result, when adapted with a stimulus that converges by 30°, the shape aftereffect was observed only in the direction of convergence, and when adapted with the stimulus diverged by 30°, the shape aftereffect was observed only in the direction of divergence. Experiment 2 was to find out what aftereffect patterns were observed when applying a pair of faces as adaptation stimulus and a single face as testing stimulus. As a result, there was no significant aftereffect. The results of Experiment 1 and 2 propose that the observer processes a pair of faces as a single unit, not as individual left-facing and right-facing faces, implying the existence of neurological pathways for directional processing of social dyad stimuli, where the human visual system consists of three separate dimensions; convergence and divergence.