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At least 37 records · Page 2Linked to original sources
PubMed1976

[Constancy of color perception in the gray toad (Bufo bufo L.): role of the surrounding background in recognition of stimulus color].

The paper continues the previous study (1) on some aspects of toad colour vision. It deals with signs which allow the visual system of toad to recognize blue stimuli. The behavioural experiments were performed during the breeding season when males exhibited the clasping of stationary blue stimuli. It is shown that in spite of some variety of spectral compositions of light sources males clasp only blue stimuli on white surrounding background. Under fixed illumination on white background males clasp blue stimuli, while on red and/or yellow background they clasp grey stimuli as well. These responses appear explicable if it is assumed that the surrounding background is the main sign of a spectral composition of illumination with "the simultaneous colour contrast" being a part of the constant colour perception mechanism (2).

Animals↗
PubMed1992

Color perception within a chromatic context: changes in red/green equilibria caused by noncontiguous light.

We measured changes in the color appearance of one light caused by another light presented in a well-separated region. Observers viewed a 1 degrees test field superimposed on a 3 degrees, 540 or 660 nm adapting field (32 or 320 td). The change in appearance due to noncontiguous light was determined by surrounding the 3 degrees adapting field with a continguous 3 degrees i.d., 5 degrees o.d. ring of either 32 or 320 td. The ring was 540, 660 nm or achromatic (tungsten-halogen "white"). The test was an admixture of 549 and 660 nm light, and varied from 6 to 1000 td. The observer adjusted the ratio of 549 to 660 nm test light so the test appeared neither reddish nor greenish. A 540 or 660 nm ring had a chromatic inducing effect on the small test that mimicked a simple surround contiguous with the test. Results with an achromatic ring were more complex: an isolated achromatic ring (no adapting field present) had virtually no effect on the color appearance of the test, but the same achromatic ring surrounding a chromatic adapting field shifted the test toward the color appearance of the adapting light (e.g. introducing a "white" ring surrounding a "green" adapting field shifted the test toward greenness). A thin pencil-width band of "white" light superimposed on a larger 5 degrees adapting field had an effect similar to a "white" 3-5 degrees ring. These results demonstrate (1) strong effects of the remote noncontiguous lights and (2) that the change in color appearance they cause is not a simple function of only the light in the noncontinguous region. The change depends on other lights in view. The visual processes revealed in these experiments are considered in terms of inferred illumination and surface reflectances of objects in natural scenes.

Adaptation, Ocular↗
PubMed1990

[Early diagnosis of congenital disorders of color vision with the Velhagen "Pflügerhaken Color Charts for evaluating color perception" in 3,375 preschool children].

In three series of examinations, 3375 male preschool-age children and 93 adult normal trichromates were tested using the Velhagen Pflügerhaken charts. The authors recommend modifying the evaluation of the results slightly by introducing a "doubteful" category for children who make one mistake or who show hesitation and lack of assurance in interpreting the charts. Using this modified form of assessment, diagnoses of "probably achromatopic" and "doubtful" were made in 7.16% and 2.13% respectively of 1689 preschool-age boys. The failure rate during the test and the duration of the examination were age-dependent, and declined with increasing age from 4.15% to 0.45% and from 1.18 min to 0.59 min, respectively. Most mistakes were made with charts nos. 9, 3, and 5. The results of tests with Pflügerhaken charts are fully comparable with those of other internationally used tests for adults. They can be recommended for screening preschool-age children.

Adult↗
PubMedDate not supplied

[Contancy of color perception in the grey toad].

Under the conditions of behavioural experiment capacity of grey toads for constant perception of an object colour was studied. It is shown that irrespective of the spectral composition of light source toad males are able to recomgnize blue colorations among the other ones (green and grey of various gradations).

Animals↗
PubMed1991

Two carriers for motion perception: color and luminance.

Starting with the experiments of Ramachandran and Gregory (Nature, 275, 55-56, 1978), several psychophysical studies in apparent motion (AM) have established that the perception of motion is significantly impaired at equiluminance. Still debated, however, is whether color alone can resolve ambiguities in AM. We report here on several psychophysical experiments, the quantitative results of which indicate that color does play a substantial role in AM. These findings seem to support recently proposed neurophysiological frameworks according to which there exist significant interactions among the neuronal pathways mediating the perception of basic visual attributes such as color, motion, form and depth.

Color Perception↗