Percieved Depth of Half-Occlusions

The purpose of this experiment was to assess the perceived depth of half-occlusions. Half-occlusions are the monocular fragments of an occluded figure that appear visually adjacent to the occluding figure. Observers were presented both ecologically valid and ecologically invalid half-occlusions. The contribution of three additional variables on the perceived depth of half-occlusions was also examined: 1.) the width of the half-occlusion, 2.) the luminance relationship between the half-occlusion and the occluder, and 3.) whether there were one or two half-occlusions adjacent to an occluder. Twenty-one undergraduate students were presented computer-generated stereograms in a 2 (ecologically valid or invalid half-occlusions) X 2 (wide or narrow half-occlusions) X 2 (luminance relationship between the half-occlusion and occluder) within-subjects factorial experimental design. Each of the resulting 16 stereograms was presented 5 times in a random order for depth judgments of the half-occlusions and of the area beyond the half-occlusion. Results showed that each factor as a main effect or as an interaction affected perceived depth. The results were discussed in terms of published theories