title: Superior discrimination for hue than for saturation and an explanation in terms of correlated neural noise.
abstract: The precision of human colour discrimination depends on the region of colour space in which measurements are made and on the direction in which the compared colours-the discriminanda-differ. Working in a MacLeod-Boynton chromaticity diagram scaled so that thresholds at the white point were equal for the two axes, we made measurements at reference points lying on lines that passed at 45° or -45° through the white point. At a given reference chromaticity, we measured thresholds either for saturation (i.e. for discriminanda lying radially along the line passing through the white point) or for hue (i.e. for discriminanda lying on a tangent of a circle passing through the reference point and centred on the white point). The discriminanda always straddled the reference point in chromaticity. The attraction of this arrangement is that the two thresholds can be expressed in common units. All that differs between saturation and hue measurements is the phase with which the short-wave signal is combined with the long-/middle-wave signal. Except for chromaticities very close to the white point, saturation thresholds were systematically higher than hue thresholds. We offer a possible explanation in terms of correlated neural noise.
authors.affiliation: Laboratory of Visual Physiology, I. P. Pavlov Institute of Physiology, Nab. Makarova 6, St Petersburg 199034, Russia Department of Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK mvd1000@cam.ac.uk.
authors.forename: M V
authors.initials: MV
authors.lastname: Danilova
authors.affiliation: Department of Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK.
authors.forename: J D
authors.initials: JD
authors.lastname: Mollon
mesh_terms: D003118:Color Perception; D055253:Color Vision; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D012684:Sensory Thresholds
keywords: colour discrimination; colour vision; correlated neural noise; hue; saturation