Abstract

In both the Hermann and Speillman illusions, small gray spots are seen at the intersections of the white grid on the surrounding black grid field. The existing explanations of the illusions are of two types. The first explanation states that the gray depressed spots are caused by the excitatory regions of the human receptive fields having concentric on-center and off-center areas. Other investigators attribute this phenomenon to Ratliff’s theory on the effect of the secondary bipolar cell innovations. Although the process is not the same as the illusion described above, the present research systematically investigates the perception of the geometric figures consisting of black grids surrounded by high-frequency colored grids. Six different surrounding colored grid figures with five different densities of grid were tested. The subjects perceived a black grid figure as various reflecting colors complementary to the surrounding grid colors. The optimal visual angle for the illusion was 6–18 min of arc. The results were analyzed by the analysis of variance, and a few theoretical implications were discussed by comparing the theories described above.

© 1988 Optical Society of America