Osman Kavcar¹, Michael E. Rudd^1,2, Christabel Arthur¹, Michael A. Crognale^1.2; ¹University of Nevada, Reno, ²Center for Integrative Neuroscience

We investigated brightness induction using disk/annulus stimuli. Observers adjusted the brightness of a match disk to match the brightness of a fixed-luminance target disk surrounded by an annulus whose luminance was varied to induce brightness changes in the target. Unlike the classical paradigm (Wallach, 1948), the match disk was not surrounded by an annulus. When the resulting brightness matches are plotted against annulus luminance on a log-log scale, the relationship is well described by 2nd-order polynomial functions, which we refer to as achromatic color appearance matching functions (ACAMFs; Kavcar, Rudd, & Crognale, 2025). Rudd, Kavcar, and Crognale (2023) proposed a brightness induction model for our stimuli based on edge integration combined with contrast gain control, and the auxiliary assumption that observers discount the outer annulus edge on the target side with this display. The model predicts that the 2nd-order coefficients (k2) of the polynomial ACAMFs should be proportional to the 1st-order coefficients (k1) with a proportionality constant that depends on the contrast polarity of the target disk to its annulus, the target disk luminance, and the strength of the contrast gain control. Our previous work established experimentally that this relationship does not depend on the annulus size but does depend on the target disk luminance and contrast polarity. Here, we further tested the model by varying the background luminance. Our results support an additional model prediction that the relationship between 1st- and 2nd-order coefficients should not depend on the background. The slope of a linear regression line fitted to the k1 vs k2 plots remained virtually unchanged as the background luminance was varied; and was ~-3.30 for conditions in which the target was a luminance decrement, and -~1.74 for conditions in which the target was a luminance increment. These values replicate the values obtained in our earlier work.

Acknowledgements: Research reported in this paper was supported by National Institute of General Medical Sciences of the National Institutes of Health under grant number P30 GM145646. The content is solely the responsibility of the authors.