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Results for “Color Perception”

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PubMedDate not supplied

[A model of constant color perception for continuous spectral functions].

A trichromatic model is proposed of constant pattern of colour perception (MCCP) for scenes with a single illumination source. In MCCP functions of the source emission, surface reflection, photoacceptor sensitivity are approximated by the normal distribution curves. MCCP characteristics "colour tone", "cleanness", and "lightness" organize its output colour metric by the human's pattern, and in a wide range of spectral composition of illumination they are invariant under these changes. Special colorimetric regime of MCCP work which estimates the colour of visual stimulus permits a comparison between the efficiencies of two proposed algorithms of visual information processing for MCCP.

Color Perception↗
PubMed1977

[Importance, especially in aeronautics, of color perception tests under dynamic conditions. Study of a suitable experimental apparatus].

Following a review of the most recent opinion on the physiology of colour vision, a device for examining it in dynamic, i.e. real-life conditions is described. The apparatus consist of two projectors which flash two absolutely identical pictures on to the screen, one of them is upside down. It appears at fixed but adjustable intervals so that the exposure time of the intelligible image can be varied. Subjects were also controlled with Ishihara charts and Nägel anomaloscope. The results are compared and point to the higher sensitivity of the dynamic test to even slight degrees of dyschromatopsia.

Color Perception Tests↗
PubMedDate not supplied

[The spherical theory of color perception: its verification by the methods of psychophysics and neurophysiology].

In the paper data of experimental verification of "spherical theory of perception" (E. N. Sokolov) are summed on the material of colour perception study. The results of psychophysical experiments with subjects having different forms of colour perception (normal trichromats, colour anomalies) and neurophysiological experiments on animals (carp) are considered within single psychophysiological system--spherical model of colour discrimination. Neuron-like elements of the model reflect the activity of light-sensitive cells of the visual system and at the same time reproduce some rules of subjective colours discrimination at the psychophysical level. Advantages of spherical model are considered allowing to analyze human individual colour functions in norm and pathology and giving the opportunity of strictly quantitative approach to description of neuronal mechanisms of colour vision. From the position of spherical model of colour discrimination neuronal structure of colour analyzer is discussed, which includes layers of photoreceptors, ++predetectors (colour-opponent and achromatic cells) and colour-selective detectors.

Animals↗
PubMed1992

The dermo-optical perception of color as an information source for blind travelers.

Dermo-optical color perception refers to a person's ability to distinguish color surfaces through "skin perception" without the use of sight. The aims of this study were (1) to assess prior research findings which apparently demonstrated the existence of dermo-optical color perception and (2) to explore the possibilities of using color to indicate reference points for blind travellers. Three experiments were conducted with 20 congenitally blind subjects and a sighted blindfolded control group matched on age, sex, and education. In Exp. 1 on a discrimination task subjects were asked if two boards were of the same color and on a pairing task were asked to match a colored board with one among a set of three boards having the same color. In Exp. 2 the discrimination task was identical to that in Exp. 1, but instead of using boards perceived through haptic exploration, we used colored cubicles in which the whole body would be exposed to the color. In Exp. 3 subjects were asked to walk along the corridor of a labyrinthine set-up and to identify any changes of color they could perceive. The experiments were designed to provide measures of reliability of subjects' responses. Analysis showed little or no support for the ability to perceive color by dermo-optical means. The comparisons of the blind and the sighted control groups were nonsignificant. On the basis of our findings, the use of color to help blind travellers has to be rejected. The paper concludes with a discussion suggesting reasons for the contradictory results emerging from studies on dermo-optical color perception.

Adolescent↗
PubMed1989

Influence of achromatic surrounds on categorical perception of surface colors.

Color samples selected from the OSA Uniform Color Scales set were seen isolated in a dark field, illuminated by hidden projectors. These appeared as self-luminous aperture colors when thus isolated. We employed a categorical color-naming procedure to assess color appearance. Achromatic surrounds of 33 min width, if adjacent to samples subtending about 2.2 deg, were sufficient to render normal categorical surface-color perception. As the size of surrounds decreased, color naming shifted from that normally observed in the surface-color mode to that appropriate to the aperture-color mode. For isolated samples, brown was almost never seen, being most often replaced by orange; a white border less than one-sixtieth the width of the color samples was sufficient to restore its perception in an otherwise dark field. The reflectance of the surround and the gap between test and surround stimuli were also examined and found to be important factors in surface color perception, whereas the overall luminance level was not.

Adult↗
PubMedDate not supplied

[Perception of color and volumetric shape of objects].

The problem of recognition of coloration of volume objects, illuminated simultaneously with bright point ans weak diffuse sources (having arbirary and previously unknown spectra) is considered. A mathematical model, in which a process of recognition of coloration is accompanied by determining orientations of surface elements relatively the point source is described. The information on orientation allows in many cases to calculate the volume shape of objects of the external world form their monocular ""retinal"" image.

Color Perception↗
PubMed1992

Cortical area V4 and its role in the perception of color.

The color and lightness vision of three monkeys with bilateral removal of cortical area V4 and three unoperated controls were tested by measuring their ability to discriminate between two rows of colored or gray stimuli. In one row, the stimuli were ordered in terms of either chromaticity or luminance, whereas in the other row they were disordered. Their ability to select the odd-one-out in an array of colors or grays and to select the colored patch from an array of achromatic grays was also assessed. Unlike an achromatopsic patient tested previously in an identical fashion, monkeys with V4 lesions performed indistinguishably from controls in the oddity test. The animals lacking V4 were slightly impaired at discriminating between ordered and disordered arrays of colors or grays, but the color impairment was no more severe than the impairment with grays. These deficits were readily accounted for in terms of the conspicuous deficits in pattern discrimination apparent in a nine-choice pattern oddity task. The results do not support the view that cortical area V4 in the monkey is the homolog of the cortical "color center" in humans, located in the lingual and fusiform gyri and damage to which leads to the clinical syndrome of cerebral achromatopsia, unless it is the additional damage to underlying white matter that leads to the severe color disorder in patients.

Animals↗
PubMed1990

Role of color in perception of attractiveness.

In this color study females reported a favorite color significantly more often than males. Males preferred bright colors significantly more than females, with a converse finding for preference for soft colors. The 276 subjects, when asked to evaluate the attractiveness of stimulus models in photographs, gave as the reason color significantly more often than style of clothing or facial expressions. Subjects significantly concurred with expert choices of recommended and nonrecommended colors in five of the six sets of photographs. This study lends credence that wearing recommended colors makes a difference in judgments of what looks best by subjects over the age of 12.

Adolescent↗
PubMed1985

A central spectrum model for the perception of coloration in filtered Gaussian noise.

In this paper we describe a monaural auditory signal-processing model for the perception of coloration. The model gives a central spectrum display of a stationary input signal. The central spectrum level for a nerve fiber tuned to a given frequency is computed as a combination of the average firing rate and the firing synchronized to the center frequency of the nerve. The model incorporates a critical-band filter bank, steady-state representations of the average and synchronized firing rates, and temporal integration. The central spectrum model, when used to process simulated data, accurately predicts the perception of coloration in filtered Gaussian noise.

Auditory Perception↗
PubMed1990

[The study of color vision in children].

The paper analyses results after investigation of color perception in 520 children (264 boys and 256 girls), aged 3-5 years, by means of two simple tests: a "Pflüger-Trident Test" (Velhagen) and a "Simplified Test of Color Vision" (Fletcher). It is proved that in children of under school age color perception is already developed enough and can be investigated for detecting disturbances in color vision.

Child, Preschool↗
PubMed1978

Dichromatic color language: "reds" and "greens" don't look alike but their colors do.

When protanopes or deuteranopes arrange the Farnsworth Dichotomous Test colors in order of similarity, they reveal their lack of red/green hue discriminations by alternating chips that the normal trichromat sees as reddish and greenish test colors. The dichromatic orderings follow a systematic variation in saturation of blue hues through neutral and into yellow hues as described by theory for each of the two types. Some dichromats who show the typical test behavior nevertheless use reddish and greenish hue terms appropriately when instructed to name the same test colors. Lightness cues are probably used by these dichromats in the naming task but ignored in the perceptual similarity task. Thus, unlike normal trichromats, who use similar names for perceptually similar colors, dichromats may use dissimilar names for perceptually similar colors. In this way they can achieve concordance with the normative language system despite its discordance with their impoverished color perceptions.

Color Perception↗
PubMed1992

Absence of smooth motion perception in color vision.

We have tested the behavioral evidence for a separation of the processing of color contrast from motion in the human visual system. Two different aspects of motion perception are examined; the identification of the direction of movement of a chromatic grating and the perception of smooth motion. The results show that color vision is at no great disadvantage in the identification of direction of movement, since this can be done at color contrasts quite close to detection threshold over a wide range of spatial and temporal frequencies. However, we find that subjects can identify direction without having the genuine perception of smooth motion. Smooth motion perception is revealed to be highly impaired since it is detected only at very high color contrasts and over a narrow range of spatial temporal conditions.

Color Perception↗
PubMed1989

Molecular patterns of X chromosome-linked color vision genes among 134 men of European ancestry.

We used Southern blot hybridization to study X chromosome-linked color vision genes encoding the apoproteins of red and green visual pigments in 134 unselected Caucasian men. One hundred and thirteen individuals (84.3%) had a normal arrangement of their color vision pigment genes. All had one red pigment gene; the number of green pigment genes ranged from one to five with a mode of two. The frequency of molecular genotypes indicative of normal color vision (84.3%) was significantly lower than had been observed in previous studies of color vision phenotypes. Color vision defects can be due to deletions of red or green pigment genes or due to formation of hybrid genes comprising portions of both red and green pigment genes [Nathans, J., Piantanida, T.P., Eddy, R.L., Shows, T.B., Jr., & Hogness, D.S. (1986) Science 232, 203-210]. Characteristic anomalous patterns were seen in 15 (11.2%) individuals: 7 (5.2%) had patterns characteristic of deuteranomaly (mild defect in green color perception), 2 (1.5%) had patterns characteristic of deuteranopia (severe defect in green color perception), and 6 (4.5%) had protan patterns (the red perception defects protanomaly and protanopia cannot be differentiated by current molecular methods). Previously undescribed hybrid gene patterns consisting of both green and red pigment gene fragments in addition to normal red and green genes were observed in another 6 individuals (4.5%). Only 2 of these patterns were considered as deuteranomalous. Thus, DNA testing detected anomalous color vision pigment genes at a higher frequency than expected from phenotypic color vision tests. Some color vision gene arrays associated with hybrid genes are likely to mediate normal color vision.

Color Perception↗
PubMedDate not supplied

[Trichromatic model of the constant perception of the color of objects].

A description is presented of a trichromatic model of colour constancy (MCC) of objects with concavities: folds, holes and so on. MCC involves the system of algorithmically independent processing blocks of the image heterarchically interacting and creating at its outlet a triparametric estimation of surface reflectance of each object of the picture. This estimation little depends on changes in the illumination colour. Results are presented and discussed of a computer experiment with MCC simulating the scene in which a plane with differently coloured regions and a conic hole in each are illuminated with a single chromatic light source.

Algorithms↗