Attention plays a greater role in judging large color differences than small ones.

Sensitivity to the magnitude of suprathreshold color differences increases at color category boundaries (the category effects), with this influence becoming more pronounced as the magnitude of the target color differences increases [Sci. Rep.14, 13665 (2024)SRCEC32045-232210.1038/s41598-024-64215-0]. According to the categorical facilitation hypothesis [J. Vis.15(8):22 (2015)1534-736210.1167/15.8.22], observers are presumed to spontaneously attend to linguistic categories when judging color differences. In this study, we aimed to examine how attention influences the magnitude judgments of large color differences. We psychophysically investigated whether the Stroop task involving colored words at the center of the display-thereby drawing attentional resources toward color words-interferes with a color difference judgment task involving peripheral color patches. Observers performed the color difference magnitude judgment tasks, based on maximum likelihood difference scaling (MLDS), for three square stimuli with smaller or larger color differences, under conditions with or without the Stroop task. The results showed that the sensitivity to the magnitude of color differences decreased under the Stroop task condition, and this effect was much more pronounced for larger color differences than for smaller ones. These findings suggest that attention plays a critical role in the magnitude judgments of large color differences, partially supporting the categorical facilitation hypothesis.