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E. Martinez, K.A. Jameson; Evaluating Salient Cognitive Loci in Perceptual Color Space . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1911.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: What are the properties and form of psychological color space when assessed using color symmetry judgments? The present research investigates cognitive color appearance space using a psychophysics paradigm to (i) evaluate the robustness of the color space constructs hue, saturation, and brightness using cognitive midpoint judgments, and (ii) isolate and characterize deviations occuring between the midpoint data and those dimensional constructs. Methods: The cognitive task is a psychologically simple (Stevens, 1951) and meaningful (Weiss, 1975) operation known as bisection. Three large fields (>10°), consisting of two referents and an adjusted test field, are presented on a CRT display. Referent pairs are color appearances differing along only one dimension (e.g., saturation only). Observers adjust the test field (via trackball) to represent the subjective midpoint between two referent stimuli presented. Adjusted midpoints, or 'bisection points,' can vary freely along the standard three dimensions since the adjustment method allows unconstrained movement through color space without dimensions specified. Color space for large (suprathrehold) color appearance differences (based on Munsell Renotation system) were investigated to model constant loci for achromatic (1), saturation (6), and hue (5) directions, for medium and large color-difference conditions. Results: Analyses of midpoint judgment data generally validate the cognitive salience of achromatic, saturation, and hue constructs and confirm the shape of psychologically constant contours originally presented for the Munsell Renotation system by D. Nickerson in 1964. Observer's repeated-trials for a condition are used to produce 95% confidence interval ellipses. Each ellipse is characterized by its size, shape (ratio of the major and minor semi-axes), and orientation to the x-coordinate. Various observers produce similar size, shape, and orientation for a single condition. Medium color-difference ellipses do not correlate well with large color-difference ellipses for an individual observer indicating that different dimensions are influencing bisection judgments in the two conditions. Analyses of Bisymmetry Condition Axioms reveal properties of these dimensional interactions. Conclusions: Although bisection is well established as a psychophysical task, this is the first systematic application to evaluate interactions between the multidimensional constructs typically assumed to underlie psychological color space. Dimensional interactions are revealed for these cognitive judgments, and those interactions differ across color lines and medium/large color-difference judgments.
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