Distribution of the Binocular Fixation Positions while Gazing at the Rim of a Cylinder

Effect of the Upper-Surface Visibility

Abstract

To find out how fixation points change when one gazes at the rim of a cylinder and the visibility of its upper surface changes, we measured binocular eye movements. When the upper surface is invisible, the fixation position is distributed within a bounded region. When the upper surface is visible, either (1) the fixation position is distributed on the inferred surface of an curved object or (2) the fixation position shifts to a background. From these results we conjecture that when the upper surface of a cylinder is visible, the fixation position is not located at the corresponding rim for each eye but (1) is located on the inferred surface's depth or (2) shifts to the background. This implies that a clue to a shape's contour is important in estimating the depth and inferred shapes of objects and that depth perception is reflected by eye movements.