Comparing the spatial-frequency response of first-order and second-order lateral visual interactions: Grating induction and contrast-contrast

The magnitudes of two suprathreshold lateral spatial-interaction effects - grating induction and contrast-contrast-were compared with regard to their dependence upon inducing-grating spatial frequency. Both effects cause the contrast of target stimuli embedded in surrounding patterns to be matched nonveridically. The magnitudes of each effect were measured in a common unit that indexed the degree of nonveridical contrast matching across a large range of target-grating contrasts (±0.80). Grating induction was a low-pass effect with respect to spatial frequency, whereas contrast-contrast was bandpass, peaking at approximately 4.0 cycles deg^-1. The magnitude of grating induction exceeded that of contrast-contrast, both overall and at their optimal frequencies (0.03125 and 4.0 cycles deg^-1, respectively); the two effects are equipotent at an inducing-grating spatial frequency of 1.0 cycle deg^-1. A significant negative correlation between the magnitudes of the two effects suggests a link whereby activation of second-order normalization mechanisms may inhibit first-order mechanisms.