B. R. Wooten

Opponent chromatic mechanisms: Relation to photopigments and hue naming

Opponent chromatic response functions were determined from monochromatic, equal-luminance stimuli from 400 to 700 nm for three observers using a hue cancellation procedure. The same observers scaled the hue of the stimuli using the terms red, green, yellow, and blue. The results showed that the hue scaling was accurately predicted from the cancellation functions using the model of Hurvich and Jameson. Theoretical curves were generated to fit the chromatic response functions with a linear combination of three cone photopigments. The theoretical photopigments were based on an idopsin nomogram with lambdamax at a = 435, beta = 530, and lambda = 562 nm. An estimate of the density of each observers preretinal optic media was obtained in order to relate the photopigment absorption spectra to the psychophysical data. Good linear fits were obtained for each observers red-green curve, but not for the yellow-blue curves. A nonlinear model with an expansive exponent was used to fit the yellow-blue response functions with the three theoretical photopigments.

Photopic spectral sensitivity of the peripheral retina

Photopic spectral sensitivity was determined in the mid- and far-peripheral retina by two methods. The first consisted of measuring increment thresholds on a background similar in spectral composition to CIE Source A. The resulting spectral-sensitivity functions displayed maxima at about 440 nm, in agreement with previous work. The second method consisted of measuring dark-adaptation curves following termination of the background. From these curves, spectral-sensitivity functions were derived for various times in the dark. The results showed that the 440 nm maximum quickly diminished. When photopic thresholds were estimated from the cone plateau of the dark-adaptation curves, the spectral-sensitivity functions peaked at about 550 nm and had much the same shape from the parafovea to the far periphery. We suggest that previous findings of maximum photopic sensitivity in the short-wave region of the spectrum resulted from chromatic adaptation induced by backgrounds (such as Source A) that were weighted towards middle and long waves.

Psychophysical determination of intraocular light scatter as a function of wavelength

Intraocular scatter of monochromatic light was assessed in three subjects (ages 21, 38, and 43) using the equivalent veil technique. For an annular stimulus of 3 deg inner and 8 deg outer diameter, the scattered illuminance at the center averaged 1.2% of the surround and was independent of wavelength from 420 to 650 nm. These results are inconsistent with predictions of wavelength dependence inherent in recent theories of ocular scatter. We conclude that intraocular scatter is produced by particles or cellular structures substantially larger than the wavelength of light.

Short-wave cone input to the red-green opponent channel

Abstract de Monasterio and Gouras (1977) have shown that the short-wave lobe of tri-phasic, red-green opponent ganglion cells in rhesus and cynomologus monkeys results from interaction between middle- and long-wave sensitive cones. They have argued that the same is true for the human red-green system. We show that the short-wave red lobe of the human red-green system as determined by hue cancellation must result from the interaction of all three cone types with the short-wave receptor predominating.

Human infant color vision and color perception

Major issues in research on the human infants sensory and perceptual coding of wavelength information are discussed. It is firmly established that two-month-old infants are at least dichromatic, but there are no clear data on whether they are trichromatic. There is some evidence to suggest that the basic sensory capacities required for color processing are different for infants than for adults, but specifics on the ontogenetic course are as yet unknown. Despite the recent increase in publications in this area, a critical review of the experimental literature yields few firm conclusions. Methodological considerations barring conclusions from the older literature persist to the present. In terms of perceptual processing, doubt is cast on recently advanced ideas that infants and adults perceive hue categorically.

Evidence that brown is not an elemental color

Two experiments using the continuous judgmental color-naming technique (Sternheim & Boynton, 1966) were performed to investigate possible response biases in an earlier investigation of the possible elemental nature of brown (Fuld, Werner, & Wooten, 1983). We manipulated theorder in which the response categories were presented by attempting to build in a maroon category dependence (Experiment 1) and by avoiding a brown category dependence (Experiment 2). The results indicate that the order in which the response categories become available can influence color-naming results; they also indicate that brown is not an elemental color. Yellow and black were reconfirmed as elemental colors, thus upholding the assumption of Hering opponent process models that there are six elemental colors.

Achromatic color categories

Sternheim and Boynton’s (1966) continuous judgmental color-naming technique was used to assess the elemental nature of achromatic colors. Results from three subjects indicate that the names “black” and “white” are necessary and sufficient to describe achromatic test lights associated with the name “gray.” On the basis of the criteria that establishes a color as elemental, black and white were confirmed as elemental, whereas gray was not. These findings support the assumption of various opponent processing models that there are only two elemental achromatic sensations. In addition, the results support Hering’s (1920) view that black and white differ from the paired-chromatic opponent colors in that they are not mutually exclusive.

Opponent chromatic response functions for an average observer

Average opponent chromatic response functions are presented for use in quantitative models of color perception. Theoretical transformations of photopigment input are related to opponent channel activity. Opponent chromatic activity is, in turn, used to describe a theoretical huenaming curve for an average observer.

Unsettled issues in infant color vision

The purpose of this paper is to clarify several issues in infant color vision that, despite previous reviews in this journal, remain in dispute. We argue that the data are still insufficient to conclude that 2-3-month-old infants are adult-like trichromats, but they are at least dichromats. How closely infant hue perception parallels adult hue perception cannot be discerned from existing data.

The elemental hues of short-wave and extraspectral lights

The continuous judgmental color-naming technique was used to assess the elemental nature of hue names descriptive of short-wave and extraspectral lights. Subjects were instructed to describe the hue of a 3-deg, 1-sec, 1,000-Td light by assigning percentages to each of three or four response categories available for use in a particular session. Response categories were chosen from the following group: red, green, blue, yellow, violet, and purple. Test stimuli consisted of monochromatic lights ranging from 510 to 420 nm and various proportions of 400-and 700-nm light. Results from eight subjects showed the color names blue, red, and green to be necessary and sufficient in describing these lights. On the basis of criteria established for the elementalness of hues, blue, red, and green were determined to be elemental, whereas purple and violet were found not to be elemental.