Shifts in the retinal image of a visual scene during saccades contribute to the perception of reached gaze direction in humans.

We tested whether the perception of gaze direction is affected by the shifts in the retinal image of the visual scene during eye movements. To do so, we displaced the visual scene during saccadic eye movements and measured whether these unconsciously-detected shifts altered subjects' perception of the reached gaze direction. While facing a visual environment composed of light-emitting diodes, subjects first performed a rightward saccade of a great amplitude before producing a leftward saccade towards a target that appeared in the environment. During the primary saccade, the visual environment could be shifted by 4.5 degrees on either side. Subjects overestimated the target by 3.69 degrees and underestimated it by 2.45 degrees when the shift of the retinal image of the environment was greater and smaller than the extent of eye deviation, respectively. This suggests that the perception of gaze direction is largely based on the processing of retinal excitation both before and after the eye movements.