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Biomedical subjects

R M Boynton

Publications and source records attributed to R M Boynton.

At least 19 recordsLinked to original sources
PubMed1996

Frederic Ives Medal paper. History and current status of a physiologically based system of photometry and colorimetry.

The CIE chromaticity diagram, which has been in common use for more than 60 years, disguises essential relations among cone excitations that become transparent in a system developed with D. I. A. MacLeod and initially proposed by the author to the CIE in 1979. This proposal led to the formation of a CIE committee to consider an ideal version of the system, to be employed either as a supplement to, or an alternative for, the 1931 "standard observer". After 15 years, the task remains unfinished. The history of debate within the original committee and that of its successor (which is still active today) is briefly reviewed. Among cone fundamentals that might be chosen, a set derived and published by Stockman, MacLeod, and Johnson [J. Opt. Soc. Am. A 10, 2491 (1993)] is favored here, and some of the advantages for displaying visual data in a system based on these fundamentals are illustrated.

Color Perception↗
PubMed1990

Salience of chromatic basic color terms confirmed by three measures.

Using single color terms of their choice, nine subjects named each of 424 colors twice under carefully-controlled conditions. Compared to any other color names, the chromatic basic color terms (red, green, yellow, blue, orange, purple, brown and pink) are all used more consistently within subjects, with greater consensus between subjects, and with shorter mean response times; there is no overlap between the two categories of color names by any of these criteria. The results are interpreted as supporting the conception that basic color terms refer to fundamental sensations for which there is a specific physiological basis.

Adult↗
PubMed1990

Segregation of basic colors in an information display.

Previous studies of the role of color in visual search have shown efficient coding for as many as six colors in a high-density display. In an effort to increase this limit, we established an optimal basic color code from extensive surface-color-naming data. This code yielded excellent segregation in a visual search task: The time required to find a critical target of a cued color increased only marginally as up to nine groups of different colors were added to the display. It made no difference whether the cue was provided by name or by example. Significant color differences in this task triggered a second experiment, which examined the detectability of the critical target feature in the periphery. A close correlation was found to exist in the order of color performance between the two experiments. Color segregation was tested again in a third experiment, in which subjects were required to count the number of targets of the cued color. The colors again segregated well. A final experiment tested the proposition that it was the basic nature of the colors that was responsible for the good segregation. When seven basic colors were pitted against seven equally discriminable nonbasic ones in a modified version of the visual search task, no significant difference was found between the two groups. It is concluded that basic colors segregate well not because they are universally named but because they are well separated in color space.

Adult↗
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↗
PubMed1989

Partial color constancy of isolated surface colors examined by a color-naming method.

Color samples selected from the OSA Uniform Color Scales set were viewed without any surround. Separate light sources were used to illuminate the samples and to control the state of adaptation of the subject, thereby separating two factors that are normally confounded. A color-naming procedure was used to assess shifts in color appearance produced by altering the spectral distributions of one or both light sources. The results confirm that chromatic adaptation, when it is the only factor operating, can mediate partial color constancy.

Color Perception↗
PubMed1988

Isolating the color vision loss in primary open-angle glaucoma.

We evaluated the results of Farnsworth-Munsell 100-Hue tests in age- and lens density-matched eyes of normal subjects, glaucoma suspects, and patients with primary open-angle glaucoma. With these controls in place, no significant correlation between the test results and age or between the test results and lens density was found. However, a significant difference in the total error scores on the 100-Hue test remained. This difference could not be explained by pupil size or medications taken. We concluded that color vision loss in glaucoma is in part attributable to the disease process and cannot be explained solely on the basis of changes in age and lens density.

Aged↗
PubMed1988

Color vision.

Explore the source record for details and available documents.

Animals↗
PubMed1988

The aging lens: in vivo assessment of light absorption in 84 human eyes.

We have developed an apparatus and psychophysical paradigm for the reliable and practical measurement of light absorption by the human crystalline lens. Using this procedure we can partition a loss of sensitivity with aging into that attributable to changes in the lens and that due to other factors. The procedure eliminates effects of inaccurate refractive correction and misalignment, and reduces the effects of pupil size. Results on 84 eyes showed a gradual decrease in sensitivity with age, especially for short wavelengths. We noted considerable individual variability, which points up the value of using a procedure that assesses sensitivity loss due to lens absorption for each tested individual.

Absorption↗
PubMed1987

Categorical color perception of Japanese observers: comparison with that of Americans.

Ten native Japanese observers named 424 colors of the OSA Uniform Color Scales set using monolexemic color terms of their choice. The results are compared with those from seven American subjects previously studied by Boynton and Olson. It is concluded, in full agreement with the original thesis of Berlin and Kay, that there are eleven basic color terms in each language, each of which describes a fundamental color sensation dependent upon an underlying physiology that does not differ between the two groups.

Adult↗
PubMed1987

Effects of field area and configuration on chromatic and border discriminations.

Visual discrimination was tested with juxtaposed fields that differed only in luminance, S cone excitation, or the ratio of L to M cone excitation. Observers were asked to make discriminations based upon a criterion of color difference or of the perception of a border between fields. The area of the fields was varied either by increasing the length of their common junction or by increasing their widths at constant junction length. For fields larger than 0.2-0.4 deg2, area controls sensitivity. For smaller fields, discrimination may be worse for narrow fields with long common junctions than for wide ones with small common junctions, especially for discriminations that depend upon S cones, in which the field components tend to become spatially integrated. Decreasing viewing time reduces the magnitude of this effect. S cone and L-M channel acuities were estimated at about 7 and 32 c/deg, respectively.

Adult↗
PubMed1987

Rod influence in dichromatic surface color perception.

Two protanopes, two deuteranopes, and two normal subjects named 424 OSA Uniform Color Scales samples using single-word color terms of their choice under three different experimental conditions. When viewing a stimulus field subtending about 4 deg, the performance of the dichromats revealed a substantial ability to discriminate colors along the red-green axis. When the stimuli were limited to the central fovea, or when rods were excluded with a bleach, dichromats could no longer categorize colors in the red-green dimension. The different conditions did not affect the performance of the normals. The results suggest that rods contribute signals used by dichromats, along with lightness cues, to help discriminate and categorize surface colors.

Adolescent↗
PubMed1987

Analysis of color-matching ellipses in a cone-excitation space.

Color-discrimination ellipses derived from the variability of color-matching data of six observers are analyzed in a normalized constant-luminance cone-excitation space. The analysis shows that the ellipses do not vary significantly in shape with chromaticity, observer, or experimental conditions. The discrimination contours are predictable from the thresholds on the two cardinal axes of this space; these are used to normalize the data at each chromaticity for each observer. Thresholds on these two axes vary with chromaticities, individuals, and experimental conditions in accordance with simple and familiar laws.

Adult↗
PubMed1986

Similarity of normalized discrimination ellipses in the constant-luminance chromaticity plane.

Discrimination steps were measured for three subjects, along oblique axes passing through nine points in a 25 td constant-luminance chromaticity plane. When plotted in a normalized cone-excitation chromaticity diagram, the best-fitting discrimination ellipses for a given subject have approximately the same shape and orientation regardless of the reference chromaticity. Their orientation is consistent with the hypothesis that excitation of B-cones affects the red-green opponent balance, otherwise determined by R- and G-cone excitations, in a manner independent of initial cone-excitation levels. The CIELAB formula predicts an orientation for normalized ellipses in agreement with the data, but it also predicts systematic changes in the ratio of minor to major axes which are not observed experimentally.

Color Perception↗
PubMed1985

Blue cones contribute to border distinctness.

A conclusion reached by Kaiser and Boynton in wavelength discrimination experiments, that differential blue-cone excitation makes a small contribution to the distinctness of borders in small fields, was verified using a rating procedure for borders produced in the La Jolla Analytic Colorimeter.

Color Perception↗
PubMed1985

Role of the blue mechanism in wavelength discrimination.

The role of blue cones as well as the pathways they supply (collectively called the "blue mechanism") is evaluated by comparing ordinary wavelength discrimination functions with those obtained using two methods designed to inhibit the blue mechanism selectively. These methods use a just-noticeable-border criterion (JNB), instead of the usual one of just-noticeable-difference, and a yellow preadapting field to induce transient tritanopia. Without transient tritanopia, the data obtained using the just-noticeable-border criterion reveal a small contribution of the blue mechanism to wavelength discrimination. Transient tritanopia, with JNB, produces an additional selective loss of wavelength discrimination in a spectral region flanking 460 nm, which yields a function resembling those for tritanopes previously examined.

Color Perception↗
PubMed1984

Selective color effects in dichoptic masking.

Dichoptic masking was investigated under conditions designed to isolate, in turn, achromatic and chromatic pathways in the visual system. Red, green, and blue tests and masks were used in various combinations. For the achromatic condition, achieved with a 3 min, 10 msec test flash and a 3 deg masking flash and with both eyes light adapted, there is essentially no dichoptic masking. With a 50 min test flash and conditions otherwise the same, a small amount of chromatically nonselective dichoptic masking occurs which is attributed to interaction between fairly remote contours, a form of weak pattern masking. For the chromatic condition, achieved with a 1 deg test flash delivered for 200 msec with both eyes light adapted, a small, nonselective masking effect, also attributed to weak pattern masking, occurs for most color combinations. The only chromatically-selective effect observed occurs for blue tests seen with blue masks. For this condition, dichoptic thresholds reach a maximum at modest photopic luminances of the mask and then decline.

Adaptation, Ocular↗