title: Convex hull test of the linear separability hypothesis in visual search.
abstract: Visual search for a colour target in distractors of two other colours is dramatically affected by the configuration of the colours in CIE (x, y) space. To a first approximation, search is difficult when a target's chromaticity falls directly between (i.e. is not linearly separable from) two distractor chromaticities, otherwise search is easy (D'Zmura [1991, Vision Research, 31, 951-966]; Bauer, Jolicoeur, & Cowan [1996a, Vision Research, 36, 1439-1466]; Bauer, Jolicoeur, & Cowan [1996b, Perception, 25, 1282-1294]). In this paper, we demonstrate that the linear separability effect transcends the two distractor case. Placing a target colour inside the convex hull defined by a set of distractors hindered search performance compared with a target placed outside the convex hull. This is true whether the target was linearly separable in chromaticity only (Experiments 1 and 2), or in a combination of luminance and chromaticity (Experiments 3 and 4).
authors.affiliation: Department of Psychology, University of Waterloo, Ontario, Canada.
authors.forename: B
authors.initials: B
authors.lastname: Bauer
authors.forename: P
authors.initials: P
authors.lastname: Jolicoeur
authors.forename: W B
authors.initials: WB
authors.lastname: Cowan
mesh_terms: D000328:Adult; D003118:Color Perception / Q000502:physiology*; D003623:Dark Adaptation; D005260:Female; D006801:Humans; D008297:Male; D011930:Reaction Time; D013053:Spectrophotometry