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.     

FACILITATION OF CHROMATIC CONE ACTIVITY BY ROD ACTIVITY

STABELL, U. & STABELL, B. Facilitation of chromatic cone activity by rod activity. II. Variation of chromatic-related cone activity. Scand. J. Psychol. , 1971, 12, 168–174.–At the cone-rod break of the dark adaptation curve, the specific threshold was found to drop to lower intensity levels, while the threshold curves of fovea proceeded in one step only, confirming the suggestion that rods may facilitate chromatic-related cone activity.     

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

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 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.     

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.     

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.     

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.     

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.     

Verbal reaction times to hues vs hue names and forms vs form names

Iwo choice reaction time (RI) studies were carried out in which different classes of stimuli—hues vs hue names in one study and forms vs form names in the other—occurred in independent lists of2, 4, and6 equally probable alternatives. Mean choice RIs were faster for hue names and form names than for hues and forms with4 and6 alternatives, but no significant differences were found in the2-stimulus lists. In both studies, significant list length by stimulus type (e.g., hues vs hue names) interactions indicated greater increase in mean RI with increases in list length for forms and hues than for form names and hue names. It was concluded that differential amounts of generalization of interference aceounted for the interactions. Effects of experimental variables on inferred components of RI were also examined.     

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.     

PROJECTED AFTERIMAGES AND COGNITIVE MATURITY

R uuth , E. & S mith , G. J. W. Projected afterimages and cognitive maturity. Scand. J. Psychol ., 1969, 10, 20 9–214—The hypothesis that projected afterimages will remain size-constant if they are not isolated by the observer as subjective phenomena is tested in a group of 20 children classified with respect to cognitive maturity. The less mature children, still mainly in the preoperational stage, are more resistant to size-increase with increasing projection distance and also report more positive hues. Tney apparently confuse their afterimages with real objects and thus fail to objectivize.     

COLOR THRESHOLD MEASUREMENTS IN SCOTOPIC VISION

The absolute and the color threshold in scotopic vision generally coincide during dark adaptation, indicating that color-threshold intensity is a measure of the concentration of rhodopsin, and that different modes of rhodopsin regeneration are reflected in the measurements of the color threshold.     

The diagnosticity of color for emotional objects

Object classification can be facilitated if simple diagnostic features can be used to determine class membership. Previous studies have found that simple shapes may be diagnostic for emotional content and automatically alter the allocation of visual attention. In the present study, we analyzed whether color is diagnostic of emotional content and tested whether emotionally diagnostic hues alter the allocation of visual attention. Reddish-yellow hues are more common in (i.e., diagnostic of) emotional images, particularly images with positive emotional content. An exogenous cueing paradigm was employed to test whether these diagnostic hues orient attention differently from other hues due to the emotional diagnosticity. In two experiments, we found that participants allocated attention differently to diagnostic hues than to non-diagnostic hues, in a pattern indicating a broadening of spatial attention when cued with diagnostic hues. Moreover, the attentional broadening effect was predicted by self-reported measures of affective style, linking the behavioral effect to emotional processes. These results confirm the existence and use of diagnostic features for the rapid detection of emotional content.     

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.     

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.