Lateral Inhibition Explanation of Geometrical Illusions

Abstract

Ganz¹ has suggested that figural distortions found with geometrical illusions are produced by lateral inhibition which results whenever the visual system signals information about spatially adjacent contours². In explaining why two lines appear out of alignment when a further figure is next to one of the lines (Fig. 1) Ganz has assumed that apparent location is determined by the mean of the spatially distributed ridge of excitation which is the neural correlate of a contour. When one figure is near another the distribution of excitation from each figure is modified through lateral inhibition. Excitation is not, however, uniformly reduced ; the sections of a distribution which are closer to the peak of the excitatory ridge of the other figure are inhibited more than sections farther away. The mean of each distribution will thus be shifted, and the figures will appear displaced from each other.