The linear separability effect in color visual search: Ruling out the additive color hypothesis

Bauer, Jolicoeur, and Cowan (1996b, 1996c) demonstrated difficult visual search for color targets that were not linearly separable tin color space) from two distracter colors and easier search for Linearly separable targets. This suggested that search is mediated by a chromatically linear discrimination mechanism (see D'Zmura, 1991). However, in those experiments, the targets that were not linearly separable fell midway between the distracter colors and thus corresponded to the admix of the distracter colors. An alternate interpretation of the results of Bauer et al. is that search was more difficult when the target corresponded to the distracter admix than when it did not. We tested this hypothesis in three experiments by contrasting conditions in which a target that was not linearly separable did or did not correspond to the admix of the distracter colors. In all cases, a target that was not Linearly separable produced difficult search, demonstrating that linear separability determines search performance.