Durham E-Theses The time-course of colour vision LEE, ROBERT,JAMES How to cite: LEE, ROBERT,JAMES (2010) The time-course of colour vision, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/199/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk 1 R. J. Lee The time-course of colour vision Four experiments are presented, each investigating temporal properties of colour vision processing in human observers. The first experiment replicates and extends an experiment by Stromeyer et al. (1991). We look for a phase difference between combined temporal modulations in orthogonal directions in colour space, which might null the often-claimed latency of signals originating from the short-wavelength sensitive cones (S-cones). We provide another estimate of the magnitude of this latency, and give evidence to suggest that it originates early in the chromatic pathway, before signals from S-cones are combined with those that receive opposed L- and M-cone input. In the second experiment we adapt observers to two stimuli that are matched in the mean and amplitude of modulation they offer to the cone classes and to the cardinal opponent mechanisms, but that differ in chromatic appearance, and hence their modulation of later colour mechanisms. Chromatic discrimination thresholds after adaptation to these two stimuli differ along intermediate directions in colour space, and we argue that these differences reveal the adaptation response of central colour mechanisms. In the third experiment we demonstrate similar adaptation using the same stimuli, measured with reaction times rather than thresholds. In the final experiment, we measure the degree to which colour constancy is achieved as a function of time in a simulated stimulus environment in which the illuminant changes periodically. We find that perfect constancy is not achieved instantaneously after an illuminant chromaticity shift and that constancy of colour appearance judgements increases over several seconds. 2 The time-course of colour vision Robert James Lee Ph.D. Department of Psychology Durham University 2010 3 Contents Acknowledgements ................................................................................................................................... 8 Outline ...................................................................................................................................................... 9 1 Introduction .................................................................................................................................... 10 1.1 Colour vision ........................................................................................................................... 10 1.1.1 Mechanisms of colour vision .......................................................................................... 10 1.2 Specification of colour ............................................................................................................ 22 1.2.1 Cone-excitation space ..................................................................................................... 23 1.2.2 The Macleod-Boynton (1979) Chromaticity Diagram ..................................................... 24 1.2.3 Derrington, Krauksopf & Lennie (1984) colour space (DKL) ........................................... 25 1.3 Adaptation .............................................................................................................................. 26 1.4 Temporal issues ...................................................................................................................... 28 1.4.1 Classical S cone signal delay ............................................................................................ 28 1.4.2 Justification and Aims ..................................................................................................... 32 1.5 Colour constancy ..................................................................................................................... 32 1.5.1 Measuring constancy ...................................................................................................... 33 1.5.2 Constancy models ........................................................................................................... 33 1.5.3 Estimating the illuminant ................................................................................................ 35 1.5.4 Model implementation ................................................................................................... 36 1.5.5 The time-course of colour constancy .............................................................................. 37 1.5.6 Justification and Aims ..................................................................................................... 39 2 Hue circle stimuli ............................................................................................................................. 40 2.1 Mathematical construction ..................................................................................................... 40 2.1.1 Generating circular loci ................................................................................................... 40 2.1.2 Cardinal axes ................................................................................................................... 42 2.1.3 Intermediate axes ........................................................................................................... 44 2.2 Discrimination model .............................................................................................................. 46 4 2.3 More complex models ............................................................................................................ 52 2.4 Alternative models .................................................................................................................. 57 2.5 Relationship to measured data ............................................................................................... 58 3 Common methods .......................................................................................................................... 60 3.1.1 Calibration ....................................................................................................................... 60 3.1.2 Individual observer calibration – 8-channel.................................................................... 65 3.1.3 Individual observer calibration – CRT ............................................................................. 67 4 Experiment 1: intermediate axes experiment ................................................................................ 71 4.1 Abstract ................................................................................................................................... 71 4.2 Introduction ............................................................................................................................ 71 4.2.1 Early chromatic pathways ............................................................................................... 72 4.2.2 Delay of the S-cone signal ............................................................................................... 73 4.2.3 The Peake Effect .............................................................................................................. 74 4.2.4 Predictions ...................................................................................................................... 75 4.3 Methods .................................................................................................................................. 79 4.3.1 Apparatus ........................................................................................................................ 80 4.3.2 Calibration for individual observers ................................................................................ 81 4.3.3 Stimulus characteristics .................................................................................................. 81 4.3.4 Experimental procedure ................................................................................................. 82 4.3.5 Experimental conditions ................................................................................................. 83 4.4 Results ..................................................................................................................................... 83 4.4.1 ‘Cardinal’ axes ................................................................................................................. 85 4.4.2 ‘Intermediate’ axes ......................................................................................................... 86 4.5 Models ...................................................................................................................................