Figure 2.

A schematic of the motion displays used in experiment 1. (a) Three frames of the motion sequence used in the experiment. As the lines and dots translated to the right, the length of the lines increased, and the small dots on the lines translated to the right in phase with the lines. This display appeared as two lines that grew in length while they translated (depicted schematically in d). (b) Same as a, except that small squares were placed in the surround and translated in the opposite direction of the lines. This display generated vivid illusory contours, and the lines appeared to be progressively uncovered behind an occluding surface (depicted schematically in e). (c) If the lines did not change in length during their translation, no illusory contours were observed. (f) Mean ratings of 10 observers of the strength of apparent occlusion generated by the displays depicted in a–c (where more vivid occlusion is represented as larger ratings).