Biases in perceiving gaze vergence.

The focus of another person's gaze is an important cue in social interactions, helping us to understand others' intentions, predict their behavior, and allocate our own attention appropriately. The perception of gaze vergence provides information about the distance at which another person is fixating, but has yet to receive much empirical attention. Here, we report that observers display systematic biases when perceiving others' gaze vergence and depth of fixation. Specifically, they perceive others as having convergent gaze and fixating at closer distances, especially when gaze is directed downward or observed under conditions of sensory uncertainty. These biases may reflect the predominance of convergent over divergent gaze in everyday social interactions and implicit knowledge of the physical structure of the environment, in which objects below our line of sight are typically closer. These findings demonstrate the sophistication of social vision, in which our visual perception of others is shaped by statistical regularities, and help to establish the perception of others' gaze vergence and fixation distance as a subject of psychological investigation.