Visual search for warm and cool colors

Warm versus cool colors are considered a fundamental aspect of color experience, yet the basis for this distinction remains poorly understood. Recently, we found that the warm-cool dimension closely aligns with sensitivity biases implicit in uniform color spaces [J. Vis.23, 5572 (2023)1534-736210.1167/jov.23.9.5572], which predicts that color vision is less sensitive to the warm-cool axis than other chromatic axes. Here, we tested this prediction by measuring visual search for color targets on backgrounds defined by different axes in color space. The search task involved locating a circular chromatic target sampled from a range of chromaticities that was presented on a background of ellipses that randomly varied in color along the warm-cool (roughly orange-cyan) axis, a blue-yellow axis, or along magenta-greenish axes perpendicular to the warm-cool or blue-yellow axis. Search times were faster on both warm-cool and blue-yellow backgrounds than the orthogonal backgrounds. However, there was no difference between these two axes, or for warm versus cool hues or blue versus yellow hues. These results are consistent with weaker sensitivity for the warm-cool and blue-yellow axes of the color space, but do not reveal a salience difference between colors more strongly associated with objects and surfaces (warm and yellow) versus backgrounds and illumination (cool and blue).