Asymmetries in the strength of chromatic induction along an L-M axis of color space

Poster Presentation: Tuesday, May 20, 2025, 8:30 am – 12:30 pm, Pavilion
Session: Color, light and materials: Neural mechanisms, clinical

Michael Rudd1 (), Sean O'Neil1, Natasha Staneva1, Idris Shareef1, Michael Crognale1; 1University of Nevada, Reno

We adapted a psychophysical technique previously used to measure asymmetries in light/dark induction strength (Rudd, 2013) to here measure the relative strengths of chromatic induction along an L-M opponent axis in color space. Two achromatic disks (1.16 deg diam, 40 cd/m2) were presented on opposite sides of a Display++ monitor (Cambridge Research Systems, Kent, UK), each surrounded by an achromatic annulus (80 cd/m2). The annuli had widths 0.19 and 1.78 deg, with the display side containing the thinner annulus randomized across trials. The chromatic background was 60 cd/m2. Across trials, the L/M contrast of the background was randomly varied. Four participants adjusted the L/M content of the disk surrounded by the thinner annulus to match the two disks in hue. The background induced a contrasting hue in both disks and annuli. These hue changes were stronger on the side with the thinner annulus. We wondered if, when changing saturation of the background, the rate of change in the match settings would differ across the ranges of background saturations for which L was either < M or > M. If so, this might imply the existence of separate underlying halfwave-rectified L-M and M-L mechanisms (corresponding to separate half axes of the L-M color dimension) characterized by different gains and producing different chromatic induction strengths. In fact, we did find differences across the two background ranges. The induction strength, as measured by the rate of change in the settings as the background varied, was highly reliable across observers when the disks appeared reddish (more L), but differed markedly across observers when the disks appeared greenish (more M). The implications of our results for an edge integration theory of color (Rudd, 2010) will be discussed.

Acknowledgements: NIGMS NIH P30 GM145646