CHROMATIC ROD VISION

S tabell B. & S tabell U. Chromatic rod vision. IV. Time between pre-and test-stimulation varied. Scand. J. Psychol ., 1972, 13 , 141–144.—The scotopic contrast hue was determined as a function of time between pre-and test-stimulation. As the interval increased, the scotopic hue was found to change from orange toward yellow in the 440–475 nm region of pre-stimulation and from violet-blue toward violet in the 550–595 nm region. It is concluded that (1) depending on wavelength of pre-stimulation, the processes in the red-green substance may revert to the mid-valued state faster or slower than the processes in the yellow-blue substance, and (2) the red/blue ratio of the violet hue which has to be added to the additive opponent hue to produce the scotopic contrast hue, may change as a function of time between pre- and test-stimulation.     

TRANSITION FROM ROD TO CONE VISION:III. Successive contrast anew

S tabell , U. & S tabell , B. Transition from rod to cone vision. III. Successive contrast anew. Scand. J. Psychol ., 1969, 10 , 140–144—The relation between the specific threshold level and the upper limit of the scotopic contrast color was investigated. The achromatic interval between the scotopic and the photopic component increased when time in darkness increased, and when pre-stimulation was reduced as regards intensity, duration, or cone/rod ratio. The results are interpreted on the basis of the opponent theory of color vision.     

Chromatic rod vision VIII. Simultaneous contrast

Stabell, U. & Stabell, B. Chromatic rod vision. VIII. Simultaneous contrast. Scand. J. Psychol., 1973, 14, 1619.-Compared with the curve of additive opponent hue, the curve of scotopic hue of simultaneous contrast was found to be displaced toward blue in the orange and green-yellow regions of inducing field. The results are explained on the assumptions that (a) change of disposition for scotopic hue reflects variation in ratio of primary hue-related processes of inducing field, and (b) the chromatic-related opponent processes, in a dark-adapted and chromatically neutral eye, are of equal magnitude within the photochromatic interval.     

Chromatic rod vision VII. Intensity of pre-stimulation varied

Stabell, B. & Stabell, U. Chromatic rod vision. VII. Intensity of pre-stimulation varied. Scand. J. Psychol., 1973, 14, 12–15.-Change in scotopic hue with variation of intensity of pre-stimulation was predicted on the basis of Hering's opponent theory of color, but the experimental results could not be adequately explained within the framework of the theory.     

COLOR THRESHOLD MEASUREMENTS IN SCOTOPIC VISION: Simultaneous color contrast

S tabell , U. & S tabell , B. Color threshold measurements in scotopic vision. III. Simultaneous color contrast. Scand J. Psychol ., 1968, 9, 133–137.—Color may be observed well below the break-point level of the dark adaptation curve, suggesting that the impulse pattern initiated in the rods may trigger a color-related response. Color is induced when the intensity of the inducing field reaches a certain level above the specific threshold, provided the stimulation of the test field is observable.     

COLOR THRESHOLD MEASUREMENTS IN SCOTOPIC VISION: Test-stimulation varied

S tabell , U. & S tabell , B. Color threshold measurements in scotopic vision. II. Test-stimulation varied. Scand. J. Psychol ., 1968, 9, 129–132.—The color threshold curve generally coincides with the dark adaptation curve of the rods, irrespectively of test-stimulation variation, confirming the assumption that a threshold response of rods may initiate a color-related process. Variation of color threshold intensity is thus assumed to reflect variation of rod threshold intensity.     

ROD VISION AS CHROMATIC VISION

S tabell , B. Rod vision as chromatic vision. Scand. J. Psychol ., 1968, 9, 282–288.—It was found (I) that the smallest quantity of light of pre-stimula-tion which produces color upon test-stimulation, stands in unique relation to the intensity of the specific threshold, and (2) that the size of the pre-and test-stimulation fields may affect the duration of the after-image. The results are judged to indicate that pre-stimulation of cones creates the disposition for the color-related response, and that the color-related response is generated centrally to the photochemical systems of the receptors.     

TRANSITION FROM ROD TO CONE VISION: II. Successive contrast

S tabell , B. & S tabell , U. Transition from rod to cone vision. II. Successive contrast. Scad J. Psychol., 1969, 10 137–139—Transition from chromatic rod to chromatic cone activity during dark adaptation is interpreted as a kind of color mixing.     

CHROMATIC ROD AND CONE ACTIVITIES AS A FUNCTION OF THE PHOTOCHROMATIC INTERVAL

S tabbll , B. & S tabell , U. Chromatic rod and cone activities as a function of the photochromatic interval. Scand. J. Psychol ., 1969, 10,215– 219.—The Sco topic contrast color dominated for longer periods and at higher intensities the larger the magnitude of the photochromatic interval, indicating that the relative responsiveness of the chromatic rod to the chromatic cone activity increases as a function of the photochromatic interval.     

DURATION OF SCOTOPIC CONTRAST HUES

STABELL, U. & STABELL, B. Duration of scotopic contrast hues. Scand. J. Psychol. , 1971, 12, 106–112.–It is generally accepted that following intense and prolonged bleaching, regeneration of cone pigments in man takes a few minutes to reach completion. The results show that the scotopic hue may remain visible for more than one hour. Hence, it is suggested that light signals and not bleaching signals produce the scotopic contrast hues.     

Biological components of colour preference in infancy

Adult colour preference has been summarized quantitatively in terms of weights on the two fundamental neural processes that underlie early colour encoding: the S−(L+M) (‘blue–yellow’) and L−M (‘red–green’) cone‐opponent contrast channels ( Ling, Hurlbert & Robinson, 2006 ; Hurlbert & Ling, 2007 ). Here, we investigate whether colour preference in 4–5‐month‐olds may be analysed in the same way. We recorded infants’ eye‐movements in response to pairwise presentations of eight colour stimuli varying only in hue. Infants looked longest at reddish and shortest at greenish hues. Analyses revealed that the L−M and S−(L+M) contrast between stimulus colour and background explained around half of the variation in infant preference across the hue spectrum. Unlike adult colour preference patterns, there was no evidence for sex differences in the weights on either of the cone‐opponent contrast components. The findings provide a quantitative model of infant colour preference that summarizes variation in infant preference across hues.     

Scotopic and photopic afterimages

Stabell, U. & Stabell, B. Scotopic and photopic afterimages. Scand. J. Psychol., 1973, 14, 210–212.MdashThe curves of photopic and scotopic afterimages were found to coincide, confirming the suggestion that disposition for scotopic contrast hue is controlled basically by the ratio of hue-related processes initiated upon chromatic prestimulation of cones, while the achromatic test-stimulation is a constant stimulus, regardless of test variables.     

Scotopic contrast hues displaced toward blue

Abstract.— Pre-stimulation with a neutral white light, in a dark-adapted state, produced a disposition for a scotopic hue of violet of about 463 nm. The observation may be explained on the basis of Helmholtz's theory of complementary negative afterimages, provided that (1) the assumption that neutral white is observed when the three types of cone receptors are activated to about the same degree, is rejected, and (2) the origin of the scotopic contrast hues is assumed to be located centrally to the photochemical systems of the receptors.     

Scotopic contrast hues displaced toward red

Stabell, B. & Stabell, U. Scotopic contrast hues displaced toward red. Scand. J. Psychol., 1973, 14, 316–319.-The displacement of scotopic contrast hues toward red, contrary to predictions based on the opponent color theory of Hering, is explained on the assumption that the violet receptor system has a negligible sensitivity at the yellow cardinal point, while all the receptor systems are activated at the blue cardinal point.     

Color measurement and color theory: II. Opponent-colors theory

Quantitative opponent-colors theory is based on cancellation of redness by admixture of a standard green, of greenness by admixture of a standard red, of yellowness by blue, and of blueness by yellow. The fundamental data are therefore the equilibrium colors: the set A₁ of lights that are in red/green equilibrium and the set A₂ of lights that are in yellow/blue equilibrium. The result that a cancellation function is linearly related to the color-matching functions can be proved from more basic axioms, particularly, the closure of the set of equilibrium colors under linear operations. Measurement analysis treats this as a representation theorem, in which the closure properties are axioms and in which the colorimetric homomorphism has the cancellation functions as two of its coordinates.Consideration of equivalence relations based on opponent cancellation leads to a further step: analysis of equivalence relations based on direct matching of hue attributes. For additive whiteness matching, this yields a simple extension of the representation theorem, in which the third coordinate is luminance. For other attributes, precise representation theorems must await a better qualitative characterization of various nonlinear phenomena, especially the veiling of one hue attribute by another and the various hue shifts.     

TRANSITION FROM ROD TO CONE VISION I. Simultaneous contrast

S tabell , B. Transition from rod to cone vision. I. Simultaneous contrast. Scand. J. Psychol ., 1969, 10 , 61–64.—Above the specific threshold, color quality depended on the test filter, while at lower intensities the same color was observed irrespectively of the test filter used, confirming the assumption that colors within the photochromatic interval are triggered by rod activity. The lawful relation between rise of specific threshold and increase of rod sensitivity was not found under the condition of simultaneous contrast.     

CHROMATIC ROD VISION

STABELL, B. & STABELL, U. Chromatic rod vision. I. Wavelength of test-stimulation varied. Scand. J. Psychol. , 1971, 12, 175–178.–The ability to distinguish one type of radiation from another by its hue disappears in scotopic vision. Accordingly, scotopic hues are found to be invariant of variation of wavelength. It is concluded, on the basis of the Principle of Univariance, that hues may be triggered by light signals initiated in one type of receptor.     

Are there nontrivial constraints on colour categorization?

In this target article the following hypotheses are discussed: (1) Colour is autonomous: a perceptuolinguistic and behavioural universal. (2) It is completely described by three independent attributes: hue, brightness, and saturation: (3) Phenomenologically and psychophysically there are four unique hues: red, green, blue, and yellow; (4) The unique hues are underpinned by two opponent psychophysical and/or neuronal channels: red/green, blue/yellow. The relevant literature is reviewed. We conclude: (i) Psychophysics and neurophysiology fail to set nontrivial constraints on colour categorization. (ii) Linguistic evidence provides no grounds for the universality of basic colour categories. (iii) Neither the opponent hues red/green, blue/yellow nor hue, brightness, and saturation are intrinsic to a universal concept of colour. (iv) Colour is not autonomous.     

Foveal spatial summation in human cone mechanism

We measured at the fovea the chromatic contrast threshold for stimuli modulated along different chromatic directions in the isoluminant plane of MBDKL colour space, considering the two cardinal axes (L/M) and S/(L + M) and other intermediate non-cardinal directions. This psychophysical determination was conducted as a function of stimulus size. The test stimulus was a foveal isoluminant Gaussian patch with a raised cosinusoidal temporal profile superimposed on a neutral background. The task was performed binocularly. The increment threshold was measured for three observers by a Bayesian adaptive psychometric method (QUEST). The Ricco area of complete spatial summation was estimated from the threshold-versus-area curves. The perceptive fields are smaller for the L/M-cone opponent direction than the S/(L + M)-cone opponent. The perceptive field sizes for the stimuli in non-cardinal chromatic directions and stimuli modulated at the (L/M)-cone opponent direction present similar values. Measurements were made at two luminance levels, 5 and 40 cd m(-2), but the differences found were small. The perceptive field sizes found could be associated with LGN area.     

Linear and nonlinear opponent color coding

The linearity axiom as proposed by Krantz (1975) is confirmed for red/green equilibria, i.e., lights which appear neither reddish nor greenish (unique yellows, unique blues, and achromatic colors). This experiment also gave some evidence of “veiling,” i.e., the masking of a weak hue component by a strong one. In a second experiment, hue magnitude estimates (HME) for the green component were obtained in variable mixtures of unique green and unique yellow stimuli. Contrary to the suggestion raised by the work of Yager and Taylor (1970), we did not find the relation between the HME and the luminance of the green stimulus to be independent of the amount of added yellow. A relation proposed by Indow and Stevens (1966), in which the proportion of the green luminance is taken as the relevant psychophysical unit, gives a better fit to our data. It is shown, however, that alternative interpretations of such data are possible and that this type of experiment cannot be conclusive regarding the issue of the possibility of absolute judgment of opponent hue attributes.