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.     

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.     

Effects of hue,brightness, contrast with background,and observation time on figural dominance in ambiguous patterns

Ambiguous patterns composed of two alternate crosses of different hues and brightness on two different brightness backgrounds were viewed for 120 sec by 10 female college students. Each subject observed 92 pattern presentations (23 patterns, each pattern presented in 2 orientations and on each of 2 backgrounds). Effects of hue and brightness contrast with background were clearly demonstrated: blue was the most dominant, red the least, and green and yellow located in between. Brightness contrast of patterns with background accentuated figural dominance of the darker figures. The number of alternations increased over the observation time for hues of equal brightness; however, the relation of this measure to total duration of seeing a figure in studies of figural dominance is unclear. Theories of neural satiation, fatigue, and interaction were used in interpreting the results.     

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.     

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.     

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.     

Dark adaptation of foveal cones during the cone-plateau period

Following substantial bleaching by "white" light, absolute threshold, relative spectral sensitivity and sensation of hue of monochromatic lights were measured at the central fovea during the cone-plateau period. The absolute-threshold level was found to increase and then decrease markedly, the relative spectral sensitivity remained invariant, while the sensation of hues of monochromatic lights from the long- and middle-wave regions of the spectrum changed toward hues of shorter wavelengths.     

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.     

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.     

Scaling of saturation and hue in the nonspectral region

The saturation of two nonspectral hues, magenta and violet, and the hue shift between red and blue through the nonspectral region were both scaled by two methods, equisection to produce a difference scale, ψ_D, and ratio judgments to produce a magnitude scale, ψ_M. The colored stimuli were viewed through apertures in a dark surround, with the luminance kept constant at one of three levels, 0.5, 2.5, and 12.6 cd/m². As previously found with saturation and hue shift between two adjacent primary hues in the spectral region, WD was linear with colorimetric purity for the saturation of magenta or violet and with the mixture ratio of red or blue for the hue shift, whereas ψ_M was a power function of colorimetric purity for the saturations and of the mixture ratio for the hue shift with exponents larger than unity in both cases. The present results were combined with previous results to give the change of parameters for saturation functions over the entire hue circle.     

Assimilative hue shifts in color depend on bar width

Hue shifts were measured in isoluminant color gratings whose bar width was varied from 2′ to 20′ of visual angle. Subjects matched the hues in each grating with individual Munsell swatches. Hue shifts were largest for bar widths of 2′; however, they depended on the color combination used. Green and red shifted toward (i.e., assimilated with) whatever second grating color they were paired with. Blue, on the other hand, assimilated with red and with yellow, but remained relatively unchanged when combined with green. Yellow shifted only minimally, regardless of the second grating color. Hue shifts decreased with increasing stripe width and disappeared between 4.5′ and 7.5′. Compared with the assimilative hue shifts, color contrast effects were slight or absent. These results cannot be attributed merely to chromatic aberration, macular pigment, eye movements, or field size.     

Transfer of hue matching in pigeons.

Pigeons were trained on a modified three-key matching-to-sample procedure, in which only one comparison key (rather than two) was lighted after an observing response to the center-key standard. Pecks on keys of matching comparison hues were reinforced. When non-matching hues appeared as the initially lighted comparisons, the nonmatching hue terminated and the matching hue appeared on the other side key only if the pigeon did not peck the nonmatching comparison for 4.8 sec. Pecks to the nonmatching hue reset the 4.8-sec delay interval. Three hues were used during acquisition. During transfer tests, two novel hues were substituted individually or together for one or two of the training hues. Latencies to the novel side-key hue were shortest when a novel matching hue appeared as the standard on the center key, and were essentially identical to baseline matching latencies. In contrast, when a novel hue appeared as either a standard or comparison in a nonmatching combination, latencies increased with increasing separation between the noevel hue and the nonmatching hue. These transfer data demonstrate the concept of hue matching.     

Scaling of saturation and hue

The study concerns the relation of saturation to the purity and luminance of aperture colors viewed in a dark surround. For the primary hues, red, yellow, green, and blue, and the intermediate hues, orange and yellowish green, the saturations increased as power functions of colorimetric purity. An IS-dB increase in luminance caused a threefold increase in the exponent for yellow, but luminance had little effect on the exponents of the other colors. The direct heterochromatic matching of saturation to saturation confirmed the validity of the scales determined by magnitude estimation and led to the construction of families of saturation scales based on a common unit called a crome. Equisection and jnd scales were also determined. Their nonlinearity suggests that saturation is a prothetic continuum. It was found that mixing red or green with yellow behaves much the same as mixing red or green with achromatic light. The changes in hue behave as prothetic continua, for the equisection and jnd scales are nonlinearly related to the power-function scales obtained by magnitude estimation and matching.     

Influence of Value on Spatial Balance of Color Pairs

The spatial balance of the component colors is an important element of color harmony in a design. Munsell (1905) suggested that the area of each color in a composition be inversely proportional to the product of the color's chroma and value. Moon and Spencer (1944) proposed that both chroma and value contribute to spatial balance, but the dominant factor is the contrast of a color with the background or with the adaptation point of the eye. The purpose of the present study was to investigate the predictive power of these two rules for hues of equal chroma, varying in value. The stimuli were presented on three different achromatic backgrounds, and both complementary and adjacent pairs of hues were used. When two colors differed in value, subjects tended to avoid equal areas. With black or white backgrounds subjects seemed to prefer larger areas of the color whose value was nearer that of the background, but with a gray background, their choice was either a narrow band of light or of dark color. These findings fail to support either the Munsell or the Moon and Spencer models.     

Color-naming functions for the pigeon

Six pigeons were trained to match wavelengths in a three-key matching-to-sample paradigm. Test trials were occasionally presented, where probe wavelengths appeared on the center key and choices were made to the training stimuli presented on the side keys. Color naming functions were obtained by plotting the percentage of test trials that each training stimulus wavelength was chosen for each center key probe wavelength. The wavelength where the functions intersected was interpreted as a transition point between pigeon hues. Three experiments employed different wavelengths as training stimuli. The first two experiments demonstrated that the intersection of the color-naming functions occurred in all cases at 540 nm and 595 nm. The third experiment employed 540 nm and 595 nm as two of the three training stimuli, and the relatively slow acquisition, together with the resulting color-naming functions, supported the proposition that 540 nm and 595 nm may be transition point wavelengths between pigeon hues.     

Control of pigeons' matching-to-sample performance by differential sample response requirements

Pigeons were trained on a matching-to-sample task in which sample hue and required sample-specific observing behavior provided redundant, relevant cues for correct choices. On trials that involved red and yellow hues as comparison stimuli, a fixed-ratio 16 schedule (FR 16) was required to illuminate the comparisons when the sample was red, and a differential-reinforcement-of-low-rates 3-sec schedule (DRL 3-sec) was required when the sample was yellow. On trials involving blue and green hues as comparison stimuli, an FR 16 schedule was required when the sample was blue and a DRL 3-sec schedule was required when the sample was green. For some pigeons, a 0-sec delay intervened between sample offset and comparison onset, whereas other pigeons experienced a random mixture of 0-sec and 2-sec delay trials. Test trial performance at 0-sec delay indicated that sample-specific behavior controlled choice performance considerably more than sample hue did. Test performance was independent of whether original training involved all 0-sec delay trials or a mixture of 0-sec and 2-sec delays. Sample-specific observing response requirements appear to facilitate pigeons' matching-to-sample performance by strengthening associations between the observing response and correct choice.     

Stimulus display geometry and colour discrimination learning by pigeons

Pigeons learned a successive conditional visual discrimination on vertically and horizontally arranged pairs of stimulus-response keys. When the discriminanda were two similar hues the pigeons' performance was significantly better on the vertical than on the horizontal task. This was also found in an experiment in which the subjects could see only monocularly. When, however, the discriminative stimuli were patterns of different orientation or markedly dissimilar hues then the performance on the horizontal task had an advantage over that on the vertical one. A horizontal advantage also obtained when similar hues were discriminated on keys clustered closely together. Pigeons thus seem more adept at solving successive conditional discriminations on horizontal than on vertical pairs of keys except when similar hues are displayed on widely separated keys where the reverse is true. It is hypothesized that colour vision inequalities due to regional retinal differentiations are responsible for this latter effect.     

A random-walk model of accuracy and reaction time applied to three experiments on pigeon visual discrimination

A random-walk model of visual discrimination is described and applied to reaction time (RT) distributions from three discrete-trial experiments with pigeons. Experiment 1 was a two-choice hue discrimination task with multiple hues. Choice percentages changed with hue discriminability; RTs were shortest for the least and most discriminable stimuli. Experiments 2 and 3 used go/no-go hue discriminations. Blocks of sessions differed in reward probability associated with a variable red stimulus in Experiment 2 and with a constant green stimulus in Experiment 3. Changes in hue had a large effect on response percentage and a small effect on RT; changes in reward shifted RT distributions on the time axis. The "random-walk, pigeon" model applied to these data is closely related to Ratcliff's diffusion model (Ratcliff, 1978; Ratcliff & Rouder, 1998). Simulations showed that stimulus discriminability affected the speed with which evidence accumulated toward a response threshold, in line with comparable effects in human subjects. Reward probability affected bias, modeled as the amount of evidence needed to reach one threshold rather than the other. The effects of reward probability are novel, and their isolation from stimulus effects within the decision process can guide development of a broader model of discrimination.     

Delayed monochromatic hue matches indicate characteristics of visual memory

Short-term memory for 16 monochromatic hues from 425 to 640 nm was measured after six delays from .1 to 24.3 sec by means of an iterative, momentary stimulus-matching technique. Small shifts were revealed in the remembered hue produced by certain wavelengths at some delays. These shifts did not follow trends consistent with a storage dependent on sensory pathway characteristics, perceptually unique hues, or semantic encoding but may reflect entropic effects in a storage that is remarkably unbiased. By indicating the discriminability of hues in memory, standard deviations of the delayed matches reveal other characteristics of what is stored: Their smooth, exponential growth questions the existence of "levels" and permits estimating the half-life of hue memory; their continued resemblance to the discrimination function for simultaneously perceived hues suggests that the stored activity; closely resembled the sensory response of color. The results also indicate how successive comparisons may be corrected in applied color work.     

Newborns' discrimination of chromatic from achromatic stimuli

Two experiments assessed newborns' ability to discriminate chromatic from achromatic stimuli. In Experiment 1, newborns differentiated gray from green, from yellow, and from red: For each of these hues they preferred chromatic-and-gray checkerboards over gray squares matched in mean luminance, even though the luminance of the gray checks was varied systematically over a wide range so as to minimize nonchromatic cues. However, newborns showed no evidence of differentiating gray from blue: At some luminances they showed no preference for a blue-and-gray checkerboard over a gray square. In Experiment 2, newborns differentiated red from gray but appeared not to differentiate blue from gray: Following habituation to a series of gray squares of varying luminance, they looked longer at a red square than at a gray square of novel luminance but showed no such pattern of recovery to a blue square. The results imply that newborns have some, albeit limited, ability to discriminate chromatic from achromatic stimuli and hence, that they are at least dichromats.