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.     

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 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.     

CHROMATIC ROD VISION III. Duration of pre-stimulation varied

S tabell B. & S tabell U. Chromatic rod vision. III. Duration of pre-stimulation varied. Scand. J. Psychol ., 1972, 13 , 136–140.—The scotopic contrast hue was determined as a function of duration of pre-stimulation, together with the additive opponent hue. It is concluded that the red/blue ratio which has to be added to the additive opponent hue to produce the scotopic contrast hue, may change as a function of both wavelength and duration of pre-stimulation.     

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.     

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.     

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.     

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.     

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.     

Hue shift of induced colour as a function of luminance relations

The hue of induced colour was studied as a function of surround/test field luminance ratio using a chromatic surround and an achromatic central test field. The hue of the test field was determined by means of colour naming methods. Three inducing colours were used: blue (Wr No. 47), green (Wr No. 58), and red (Wr No. 25). The number of subjects was 9–11 in the two experiments. The luminance ratio (ranging from 0.07 to 17.1) was varied by varying the luminance of the test field (Experiment 1) or of the surround (Experiment 2). For the blue surround the results show a hue shift in accordance with the Bezold-Brücke phenomenon. For the inducing colours green and red the induced colours are weak, and the hue shifts are more or less unsystematic though there are individual subjects showing a trend in the Bezold-Brücke direction. It is concluded that the hue shifts depend on the luminance relations rather than on the test field luminance.     

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.     

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.     

Rod suppression of cone-mediated information about colour and form during dark adaptation

Following substantial bleaches, the specific form and hue thresholds were measured during dark adaptation with a test stimulus of 1 x 2 degrees at 40 degrees extrafoveally. The wavelength of the test field was varied between runs. The results show that both thresholds started to rise at about the cone-rod break of the dark-adaptation curve, irrespective of wavelength used in the test. Furthermore, the specific threshold for form was found to rise when a scotopic stimulus was superimposed on a photopic test flash. On the other hand, both thresholds remained at the cone-plateau level when the test flash was confined within the rod-free fovea. In order to explain the rise in the specific thresholds, it is suggested that signals from rods generated directly in response to the test stimulus may suppress both cone-mediated form and colour. It is also suggested that this type of rod-cone interaction represents a general characteristic involved in several kinds of visual information processing.     

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.     

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.

     

Chromatic induction effects in the Hermann grid illusion.

The chromatic Hermann grid illusion was investigated in sixteen subjects, with variation of the lightness contrast between the chromatic inducing squares and the background, and the saturation and hue of the inducing squares. Subjects made magnitude estimates of the sharpness and clarity of perceived dots at the intersections of the grid, and matched the appearances of the dots with Munsell chips. A chromatic induction effect was found to occur in the absence of lightness contrast, but the sharpness of the illusory dots increased with increasing lightness contrast (p less than 0.001). The saturation of the perceived dots increased with increases in the saturation of the inducing squares (p less than 0.05), and was higher for the longer wavelengths than for the shorter wavelengths (p less than 0.005). Neural units with center-surround arrangements responding differentially to light of the same color in the center and the surround, e.g. red off-centers and red on-surrounds, could account for the chromatic induction effect.     

Dark-adaptation mechanisms of the long-wave foveal cones

The ordinary long-term rod and cone dark-adaptation curves have generally been assumed to follow a single exponential rate of recovery. However, in two previous papers on rod dark-adaptation (Stabell et al., 1986a, b), the recovery curve was found to consist of three different sections. The results of the present paper show the same type of recovery function with three different sections for the long-term dark-adaptation curve of the long-wave cone system. During the major, middle section log cone threshold, like log rod threshold, is linearly related to the logarithm of the concentration of bleached photopigment. Presupposing that the bleached cone photopigment acts as a ligand, the change in threshold level obtained during the middle section of the dark-adaptation curve is well described by the change in activity rate of an allosteric, postively cooperative enzyme built as a dimer.     

Comparison of scotopic sensitivity in diurnal (Anas platyrhynchos) and crepuscular (Dendrocygna autumnalis) ducks.

Scotopic visual adaptation curves were obtained from 4 mallard ducks. A curve of best fit was used to compare the mallards' mean adaptation curve to the curve previously reported for the black-bellied tree duck, a crepuscular species. The curves did not differ significantly in either their slopes or base levels (thresholds). The mallards curve had a rod-cone "break" at approximately 25 min. This break is evident in the scotopic curve for pigeons, but is absent from the black-bellied tree ducks' curve. Examination of retinal tissues indicated that the black-bellied tree ducks had significantly more rods and cones, and a larger rod:cone ratio than the mallards. The mallards' scotopic visual threshold is exceeded by the natural illumination present under several nocturnal conditions.     

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.