5 research outputs found
The subjective metric of remembered colors: A Fisher-information analysis of the geometry of human chromatic memory.
In order to explore the metric structure of the space of remembered colors, a computer game was designed, where players with normal color vision had to store a color in memory, and later retrieve it by selecting the best match out of a continuum of alternatives. All tested subjects exhibited evidence of focal colors in their mnemonic strategy. We found no concluding evidence that the focal colors of different players tended to cluster around universal prototypes. Based on the Fisher metric, for each subject we defined a notion of distance in color space that captured the accuracy with which similar colors where discriminated or confounded when stored and retrieved from memory. The notions of distance obtained for different players were remarkably similar. Finally, for each player, we constructed a new color scale, in which colors are memorized and retrieved with uniform accuracy
Perceptual spaces and their symmetries: The geometry of color space
Our sensory systems transform external signals into neural activity, thereby
producing percepts. We are endowed with an intuitive notion of similarity
between percepts, that need not reflect the proximity of the physical
properties of the corresponding external stimuli. The quantitative
characterization of the geometry of percepts is therefore an endeavour that
must be accomplished behaviorally. Here we characterized the geometry of color
space using discrimination and matching experiments. We proposed an
individually tailored metric defined in terms of the minimal chromatic
difference required for each observer to differentiate a stimulus from its
surround. Next, we showed that this perceptual metric was particularly adequate
to describe two additional experiments, since it revealed the natural symmetry
of perceptual computations. In one of the experiments, observers were required
to discriminate two stimuli surrounded by a chromaticity that differed from
that of the tested stimuli. In the perceptual coordinates, the change in
discrimination thresholds induced by the surround followed a simple law that
only depended on the perceptual distance between the surround and each of the
two compared stimuli. In the other experiment, subjects were asked to match the
color of two stimuli surrounded by two different chromaticities. Again, in the
perceptual coordinates the induction effect produced by surrounds followed a
simple, symmetric law. We conclude that the individually-tailored notion of
perceptual distance reveals the symmetry of the laws governing perceptual
computations.Comment: 42 pages, 9 figures, 1 appendix. (v2) 47 pages, 10 figures, 1
appendix. (v3) Text modified after peer-review process. (v4) 34 pages, 1
appendix, 10 figures. Article accepted to be published at Mathematical
Neuroscience and Application
Novel perceptually uniform chromatic space
Chromatically perceptive observers are endowed with a sense of similarity between colors. For example, two shades of green that are only slightly discriminable are perceived as similar, whereas other pairs of colors, for example, blue and yellow, typically elicit markedly different sensations. The notion of similarity need not be shared by different observers. Dichromat and trichromat subjects perceive colors differently, and two dichromats (or two trichromats, for that matter) may judge chromatic differences inconsistently. Moreover, there is ample evidence that different animal species sense colors diversely. To capture the subjective metric of color perception, here we construct a notion of distance in color space based on the physiology of the retina, and is thereby individually tailored for different observers. By applying the Fisher metric to an analytical model of color representation, we construct a notion of distance that reproduces behavioral experiments of classical discrimination tasks.We then derive a coordinate transformation that defines a new chromatic space in which the Euclidean distance between any two colors is equal to the perceptual distance, as seen by one individual subject, endowed with an arbitrary number of color-sensitive photoreceptors, each with arbitrary absorption probability curves and appearing in arbitrary proportions.Fil: Da Fonseca, María de Los Angeles. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Samengo, Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentin