Abstract
An afterimage's shape changes systematically depending on the adapted shape. Adapting to circles produces polygonal afterimages, whereas adapting to hexagons sometimes produce circular afterimages. In this study, a right-eye afterimage produced by adapting to circles was tested while the left eye adapted to a plain background, static circles, rotating circles, rotating stars, or rotating hexagons. Subjects rated the subjective roundness of the right-eye afterimage. Although the right eye adapted to circles, the ratings varied with the left-eye adaptation. After the left eye adapted to rotating hexagons, the right-eye afterimages were rated highest (most circular). In contrast, after the left eye adapted to rotating circles, the right-eye afterimages were rated lowest (most angular). This interocular transfer of shape adaptation demonstrates that afterimage shape is determined in a cortical area that collects information from both eyes.