Abstract

The role of edges in the production and regulation of brightness phenomena is problematical. Whereas edges are crucially involved in the generation of the Craik-Cornsweet-O'Brien and missing-fundamental squarewave illusions, the necessity or degree of their involvement in classical brightness contrast, in the brightness effect of White, or in grating induction is unclear. To assess the influence of edge sharpness in the expression of the grating induction effect, induction magnitude was measured, by using both cancelling and contrast matching techniques, for two subjects as a function of systematic Gaussian blurring of the inducing/test field boundary. Four test field heights were examined, ranging from 0.25° to 2.0°, in octave intervals. Confirming previous results, grating induction magnitude decreased monotonically with increasing test field height, as measured by both procedures. Increasing levels of blur resulted in modest (eta² = 2%) but significant (p < 0.001) increases in grating induction magnitude. That grating induction magnitude does not decrease with edge blur is consistent with simulations of the effect based on a linear combination of the responses of isotropic filters across multiple spatial scales.

© 1992 Optical Society of America