Differences in the perception of monocular and binocular gaze.

Purpose: The judged direction of side gaze from a straight head is known to be biased from its true direction. This study reports the specific biases in the perceived direction of gaze from right, left, or both eyes when targets are in the plane of the observer or in a plane in front of the observer. Theories are discussed about the ocular cues that are used to determine the perceived direction of gaze.

Methods: Two sets of 16 observers judged the direction of gaze from each of two models whose LCD-imaged heads gazed toward points that were either on the plane of the observers' faces or on a plane that was midway between the models and observers.

Results: For both distant and near targets, straight monocular gaze from the right and left eyes appeared to be mildly exotropic, as expected from the positive angle kappa of the models, but straight binocular gaze appeared orthotropic. However, when binocular gaze was toward the side, the perceived direction of gaze differed significantly between the two eyes, and for this condition, the perception of binocular gaze followed that of the abducting eye.

Conclusion: When the perceived directions of monocular gaze from the two eyes do not agree, the perceived direction of binocular gaze resolves this conflict by matching that of the abducting eye.