Fatemeh Charkhtab Basim¹, Erin Goddard², Kenneth Knoblauch³, Kimberly Jameson⁴, Michael Webster¹; ¹Department of Psychology, University of Nevada, Reno, NV, US, ²School of Psychology, University of New South Wales, Sydney, Australia, ³Univ Lyon, Université Claude Bernard Lyon 1, Inserm U1208, Stem Cell and Brain Research Institute, Bron, France, ⁴Institute for Mathematical Behavioral Sciences, University of California, Irvine, CA, USA

A number of studies have shown that anomalous trichromats may have stronger color percepts than predicted by their threshold sensitivity losses. However, the form and nature of this compensation remains poorly understood. Prior work has typically examined isolated tasks, leaving open how compensation varies across different levels of perceptual and cognitive processing. In the present study, we used common stimuli and compensation metrics to quantify anomalous observers’ performance across a range of different tasks. 17 anomalous trichromats (11 deuteranomalous, 6 protanomalous) and 15 normal trichromats completed a battery assessment for stimuli that varied in nominal LvsM chromatic contrast. These included color classification (achromatic boundary placement), focal-hue selection, reaction-times, contrast adaptation, and magnitude estimation (MLDS). For each, we computed the contrast-scaling factor required to align an observer’s responses with the average values for the color normal observers, normalized by scaling relative to the threshold elevation (resulting in a compensation index ranging from 0=no compensation to 1=full compensation). The average index varied strongly with task, Appearance-based measures (e.g. focal hues) showed the strongest effects, along with contrast scaling (MLDS). Alternatively, contrast adaptation exhibited significant but smaller improvements, with weakest compensation found for reaction times. The degree of compensation also showed large observer variability, which was unrelated to the magnitude of the individual’s threshold loss. Across tasks, deuteranomalous observers generally showed stronger compensation than protanomalous observers, particularly for naming and reaction times, whereas group differences were weaker for adaptation, hue selection, and MLDS. Overall, the results show that compensation in anomalous trichromacy may involve multiple distinct processes that are differentially engaged by perceptual tasks.

Acknowledgements: Supported by EY-010834