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.