Asymmetric lightness cancellation in Craik-O'Brien patterns of negative and positive contrast.

The Craik-O'Brien illusion was measured for patterns of negative and positive contrast by a compensation method. The illusion of negative contrast (black teeth on uniform field) was stronger than that of positive one (white teeth). The amount of compensation increased linearly with increasing tooth width, but was nonlinear, showing two phases with increasing tooth height. The results might be explained by the concept of the antagonistic and nonantagonistic mechanisms in the lower stage of the visual system, and the reconstructive process of the barrier activity against the lateral spread in the higher stage.