Gale, C., and Monk, A. F. Where am I looking? The accuracy of video-mediated gaze awareness. Perception and Psychophysics 3, 62 (2000), 586–595. [pdf]
The experiments reported in this paper demonstrate that full gaze awareness is possible with sufficient accuracy to be used as a resource in face-to-face and video-mediated communication. Knowledge of what someone is looking at is used habitually in everyday life. The estimators were still very accurate when they could not see the hand-and-eye movement to the gazed-at object.
The next step in this research would be to demonstrate that a video configuration that include a single view of the face and the objects being gazed rather than these things on their own.
Participants worked in pairs, with one person gazing at a flat horizontal stimulus between them. The other participant estimated where the gazer was looking. Experiment 1 used linear scales as gaze targets. The mean root mean square error of estimation equates to 3.8 degrees of head-and-eye pan and 2.6 degrees of tilt. This small error of estimation was essentially the same in a video-mediated condition and in one in which a procedure that did not allow the estimator to see the head-and-eye movement to the target position was used. Experiment 2 obtained comparable gaze estimation performance in face-to-face and video-mediated conditions, using a combined pan-and-tilt grid. It is concluded that people are very good at estimating what someone else is looking at and that such estimations should be practical during video-mediated conversation.