Abstract
The brightness induction produced by a surround annulus on a target disk can be measured by adjusting the luminance of a second disk to match the target in brightness. This produces parabolic brightness matching functions (BMFs) when average perceptual matches are plotted against annulus luminance on a log-log scale. A model developed by Rudd et al. (JOSA A, 2023), in which a contrast gain control operates between the outer and inner edges of the annulus, predicts that a linear relationship should hold between the first-order (k1) and second-order coefficients (k2) of the parabolic BMFs. We previously verified this prediction and discovered that the slope of this linear relationship depends on the contrast polarity of the target with respect to its annulus, but is unaffected by the annulus size or the background luminance. Here, we further tested the model by varying the target disk luminance in two conditions where the target disk was either a decrement or an increment with respect to its annulus and the background was white (highest display luminance). The model predicts that the slope of the k1 vs k2 plots will itself decrease as a linear function of the log luminance of the target disk, and the rate of decrease will equal -1. Our results confirmed the first prediction, but the slope was -2 instead of -1. This pattern held both in the decremental and incremental target conditions.