Psychophysics of perceiving eye-gaze and head direction with peripheral vision: implications for the dynamics of eye-gaze behavior.

Two psychophysical experiments are reported, one dealing with the visual perception of the head orientation of another person (the 'looker') and the other dealing with the perception of the looker's direction of eye gaze. The participant viewed the looker with different retinal eccentricities, ranging from foveal to far-peripheral viewing. On average, judgments of head orientation were reliable even out to the extremes of peripheral vision (90 degrees eccentricity), with better performance at the extremes when the participant was able to view the looker changing head orientation from one trial to the next. In sharp contrast, judgments of eye-gaze direction were reliable only out to 4 degrees eccentricity, signifying that the eye-gaze social signal is available to people only when they fixate near the looker's eyes. While not unexpected, this vast difference in availability of information about head direction and eye direction, both of which can serve as indicators of the looker's focus of attention, is important for understanding the dynamics of eye-gaze behavior.