title: Evidence for the existence of colour mechanisms producing unique hues as derived from a colour illusion based on spatio-chromatic interactions.
abstract: When its spatial frequency is high enough, a grid of grey horizontal strips presented on a coloured background may change its neutral colour. It was found that some background colours induce a strong illusion and some no illusion at all. The effect of the background colour on the illusion was studied for the spatial frequencies of 0.5, 2.5, 4, and 8 c/deg. Thirty chromaticities (evenly distributed across the colour gamut triangle) of the backgrounds in the equiluminant plane, and 24 in the ML plane (where S-contrast was zero), were tested. Five matches were made for each frequency and each background chromaticity. Viewing was binocular. For the low (0.5 c/deg) frequency strips, the backgrounds were found to induce the colour, if any, approximately complimentary to that of the background (i.e., chromatic simultaneous contrast). For the high (8 c/deg) frequency, most backgrounds induced only illusory colours close to unique hues (yellow, blue, and green), with a few backgrounds inducing a mixture of green with blue. Then, the method of adjustment was used to determine the unique hues for the same three observers. A remarkable similarity was found between unique hues and illusory loci, suggesting that the illusion is due to a difference in the spatial resolution of the post-receptor channels producing the unique hues.
authors.affiliation: Department of Vision Sciences, Glasgow Caledonian University, Glasgow G4 0BA, UK. a.logvinenko@gcal.ac.uk
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Logvinenko
authors.forename: Sara J
authors.initials: SJ
authors.lastname: Hutchinson
mesh_terms: D003118:Color Perception / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D006801:Humans; D007088:Illusions / Q000502:physiology / Q000523:psychology; D010775:Photic Stimulation / Q000379:methods; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D011601:Psychophysics; D015348:Vision, Binocular / Q000502:physiology