Cone Photoreceptor Sensitivities and Unique Hue Chromatic Responses: Correlation and Causation Imply the Physiological Basis of Unique Hues

This paper relates major functions at the start and end of the color vision process. The process starts with three cone photoreceptors transducing light into electrical responses. Cone sensitivities were once expected to be Red Green Blue color matching functions (to mix colors) but microspectrometry proved otherwise: they instead peak in yellowish, greenish, and blueish hues. These physiological functions are an enigma, unmatched with any set of psychophysical (behavioral) functions. The end-result of the visual process is color sensation, whose essential percepts are unique (or pure) hues red, yellow, green, blue. Unique hues cannot be described by other hues, but can describe all other hues, e.g., that hue is reddish-blue. They are carried by four opponent chromatic response curves but the literature does not specify whether each curve represents a range of hues or only one hue (a unique) over its wavelength range. Here the latter is demonstrated, confirming that opponent chromatic responses define, and may be termed, unique hue chromatic responses. These psychophysical functions also are an enigma, unmatched with any physiological functions or basis. Here both enigmas are solved by demonstrating the three cone sensitivity curves and the three spectral chromatic response curves are almost identical sets (Pearson correlation coefficients r from 0.95–1.0) in peak wavelengths, curve shapes, math functions, and curve crossover wavelengths, though previously unrecognized due to presentation of curves in different formats, e.g., log, linear. (Red chromatic response curve is largely nonspectral and thus derives from two cones.) Close correlation combined with deterministic causation implies cones are the physiological basis of unique hues. This match of three physiological and three psychophysical functions is unique in color vision.     

Orthogonal Relations and Color Constancy in Dichromatic Colorblindness

This paper employs uniform color space to analyze relations in dichromacy (protanopia, deuteranopia, tritanopia). Fifty percent or less of dichromats represent the classical reduction form of trichromacy, where one of three cones is inoperative but normal trichromatic color mixture such as complementary colors (pairs that mix white) are accepted by the dichromat, whose data can thus be plotted to CIE chromaticity spaces. The remaining dichromats comprise many and varied more-complex gene arrays from mutations, recombinations, etc. Though perhaps a minority, the three reductionist types provide a simple standard, in genotype and phenotype, to which the more complex remainder may be compared. Here, previously published data on dichromacy are plotted and analyzed in CIELUV uniform color space to find spatial relations in terms of color appearance space (e.g., hue angle). Traditional residual (seen) hues for protanopia and deuteranopia (both red–green colorblindness) are yellow and blue, but analysis indicates the protanopic residual hues are more greenish yellow and reddish blue than in tradition. Results for three illuminants (D65, D50, B) imply four principles in the spatial structure of dichromacy: (1) complementarity of confusion hue pairs and of residual hue pairs; (2) orthogonality of confusion locus and residual hues locus at their intersection with the white point, in each dichromatic type; (3) orthogonality of protanopic and tritanopic confusion loci; and (4) inverse relations between protanopic and tritanopic systems generally, such that one''s confusion hues are the other''s residual hues. Two of the three dichromatic systems do not represent components of normal trichromatic vision as sometimes thought but are quite different. Wavelength shifts between illuminants demonstrate chromatic adaptation correlates exactly with that in trichromatic vision. In theory these results clarify relations in and between types of dichromacy. They also apply in Munsell and CIELAB color spaces but inexactly to the degree they employ inexact complementarity.     

Dichromatic color language: "reds" and "greens" don't look alike but their colors do.

When protanopes or deuteranopes arrange the Farnsworth Dichotomous Test colors in order of similarity, they reveal their lack of red/green hue discriminations by alternating chips that the normal trichromat sees as reddish and greenish test colors. The dichromatic orderings follow a systematic variation in saturation of blue hues through neutral and into yellow hues as described by theory for each of the two types. Some dichromats who show the typical test behavior nevertheless use reddish and greenish hue terms appropriately when instructed to name the same test colors. Lightness cues are probably used by these dichromats in the naming task but ignored in the perceptual similarity task. Thus, unlike normal trichromats, who use similar names for perceptually similar colors, dichromats may use dissimilar names for perceptually similar colors. In this way they can achieve concordance with the normative language system despite its discordance with their impoverished color perceptions.     

Effect of shape, size and color on selection of oviposition sites by Chaetorellia australis

The effect of shape, size and color on the selection of oviposition sites by females of Chaetorellia australis Hering (Diptera, Tephritidae) originating from infested yellow starthistle (YST) Centaurea solstitialis L. (Asteraceae, Cardueae) heads, was studied in the laboratory by direct observation of females sitting on or attempting to oviposit into different objects. Artificial substrates made of yellow-colored parafin was mimicking the natural oviposition sites (floral buds of YST), were used to study the effect of shape and size. The results revealed that spherical and conical objects of a total surface area of 310 mm², were visited more frequently than cylindrical and cubical ones of the same surface area. Also more females were observed and more oviposition attempts were recorded on spheres of 5 and 10 mm diameter than of 15 and 20 mm diameter. Yellow and orange dry YST heads, colored by dipping in molten colored ceresin wax, were preferred for oviposition to black, green, blue, red and white ones. The observed preference for certain colors depended primarily on the color hue and not on the intensity of the total reflected light. The females responded positively to hues reflecting maximally between 560 and 610 nm, optimum at 590 nm, while hues reflecting below 540 nm and especially between 400 and 500 nm appeared to have no positive effect.     

Male receiver bias for red agonistic signalling in a yellow-signalling widowbird: a field experiment

Receiver bias models of signal evolution are typically regarded as alternatives or complements to ornament evolution due to coevolving mate choice, whereas sexually or socially selected agonistic signals are rarely studied with respect to receiver psychology. Against the background of convergent evolution of red agonistic signals from yellow ancestors in the genus Euplectes (widowbirds and bishops), we experimentally test the function of a yellow signal in the montane marsh widowbird (E. psammocromius), as well as a hypothesized receiver bias for redder (longer wavelength) hues. In a field experiment in southern Tanzania, males that had their yellow wing patches blackened lost their territories or lost territorial contests more often than controls or reddened males, which together with a longer wavelength hue in territory holders, indicates an agonistic signal function. Males painted a novel red hue, matching that of red-signalling congeners, retained their territories and won contests more often than controls. To our knowledge, this is the first demonstration of a receiver bias driving agonistic signal evolution. Although the sensory or cognitive origin of this bias is yet unknown, it strengthens our view that genetically constrained signal production (i.e. carotenoid metabolism), rather than differential selection, explains the carotenoid colour diversification in Euplectes.     

Observations on the colours of lumpsuckers, Cyclopterus lumpus L.

Ripe unfertilized eggs derived from fish landed at two Icelandic ports were predominantly red and yellow-red, but a small proportion were red-purple. There was a significant difference between the frequencies of hues of eggs from the two landing places. During the phase of blastula formation, fertilized red-purple eggs showed no discernible change in either hue or chroma. However, as the gastrula formed and covered the yolk, the chroma declined dramatically, although the hue remained unaltered. When the embryo formed, the chroma continued to decrease and the hue also began to change as the red-purple pigment disappeared from the yolk and the orange-yellow oil of the yolk became more visible.
The most common plasma colouration in male fish collected at Hafnarfjordur and Husavik was red, but the observed hues covered 60% of the visible spectrum, ranging from green to purple. No significant differences between Hafnarfjordur and Husavik males in terms of hue or value were discerned, but there was a significant difference in chroma score. Female plasma hues were almost as variable as the males (spanning 45% of the visible spectrum) but centred in the green-yellow zone. Plasma, subcutaneous jelly and skin colours were closely linked.
Fish from the oceanic feeding grounds were all green in skin colour, whatever their age or sex; it is suggested that this colouration has a cryptic function in the near surface waters inhabited by lumpsuckers.     

Fixed green and brown color morphs and a novel color-changing morph of the Pacific tree frog Hyla regilla

Pacific tree frogs Hyla regilla are typically either green or brown in dorsal coloration. The frequency of green and brown individuals is known to fluctuate seasonally. Previous investigators have generally assumed that the green and brown body colors represent a "fixed" polymorphism and that seasonal changes in the proportion of the two body colors are a consequence of differential survival of the two color morphs. Here we report that, in addition to the "fixed" (i.e., non-color-changing) green and brown morphs of H. regilla, there are some individuals that can change hue between green and brown. The distribution of color-change ability in our study population is bimodal, suggesting that "color changers" are a distinct morph rather than one extreme of a continuous distribution of color-change ability. Our findings suggest that background brightness, not hue, triggers color change in the newly discovered morph and that this change requires days to weeks to occur. Such slow color change is not well suited for making short-term changes in color as a frog moves between differently colored substrates. Rather, seasonal changes in habitat characteristics and/or microhabitat use are likely to maintain color-change ability. Color polymorphism and color-change ability appear to represent alternative responses to divergent selection for crypsis in a heterogeneous, seasonally variable environment.     

Simulation of water colors in a shallow acidified lake, Lake Onneto, Japan, using colorimetric analysis and bio-optical modeling

Lake Onneto has unusually brilliant water colors, such as blue-green, green, and greenish yellow. We investigated the coloration mechanism in this lake by measuring the radiometric water color and inherent optical properties (IOPs), such as attenuation, absorption, and scattering coefficients of color-producing agents (CPAs) in the lake. The hue of the water body was determined using colorimetric analysis. In addition, the radiometric water color of the lake was simulated using bio-optical modeling. Results showed that the hues of the water body were different between two sampling stations (blue-green and green at 3.1 and 5.5 m of bottom depth, respectively). However, the total suspended solids (TSS) concentrations were almost identical between the two stations (0.47 and 0.42 mg l⁻¹, respectively). In addition, the attenuation and absorption coefficients showed that the CPAs in the water body were only inorganic suspended solids (ISS) more than 0.7 μm in diameter, and specific CPAs, such as dissolved mineral ions and aqueous colloids, were not observed in the lake. Simulation of the radiometric water color showed that the radiation around 600 nm of wavelength (yellow region) steeply increased with decreasing bottom depth, indicating that the water colors of Lake Onneto are strongly governed by the light reflection from yellowish bottom sediments.     

Neural basis for unique hues

All colors can be described in terms of four non-reducible ‘unique’ hues: red, green, yellow, and blue [1]. These four hues are also the most common ‘focal’ colors — the best examples of color terms in language [2]. The significance of the unique hues has been recognized since at least the 14^th century [3] and is universal [4] and [5], although there is some individual variation [6] and [7]. Psychophysical linking hypotheses predict an explicit neural representation of unique hues at some stage of the visual system, but no such representation has been described [8]. The special status of the unique hues “remains one of the central mysteries of color science” [9]. Here we report that a population of recently identified cells in posterior inferior temporal cortex of macaque monkey contains an explicit representation of unique hues.     

Reaction times identify a Pavlovian component in a two-choice discrimination

Six pigeons discriminated on discrete trials between two colors. In Experiment 1, two luminous spots were both either blue or green and the reinforced responses were “peck left” for blue and “peck right” for green. In Experiment 2, the hue of a center spot controlled subsequent choice pecks to left or right. In both experiments response bias was manipulated in two ways. During stimulus frequency (“SF”) sessions correct responses brought food on 40% of trials; in “imbalanced” blocks of sessions one hue appeared on 80% of trials and the other on 20%. During reinforcement probability (“RNF”) sessions the hues appeared equally often, but in imbalanced blocks the hues signaled different reinforcement probabilities, either 64% or 16%. In “balanced” control blocks the hues appeared equally often and were both reinforced at 40%. The experiments gave similar results. When bias was computed from choice percentages the imbalanced conditions yielded substantial response bias, and the amount of bias was about the same under RNF and SF treatments. However, reaction times (RTs) gave a different outcome. RNF imbalance slowed responses directed at the less reinforced stimulus, but SF imbalance had little RT effect (Experiment 1) or no effect (Experiment 2). These results suggest that choice was controlled by an instrumental stimulus-response-reinforcement association, whereas RTs were controlled by a Pavlovian stimulus-reinforcement association.     

紫茉莉开花过程中花色和花色素的变化规律

紫茉莉是我国广泛分布的庭院花卉之一,具有丰富的花色。但不同花色紫茉莉在开花过程中的花色变化规律及其呈色机制还不清楚。以紫红色、黄色和白色紫茉莉为研究对象,分别通过色差仪测定法和紫外-可见分光光度法测定了不同开花时期不同花色紫茉莉花色表型及各类色素含量,探讨了其花色和色素变化规律,揭示其呈色机制。结果表明,从花蕾期到盛开期,紫红色紫茉莉花冠由淡绿色转变为紫红色,明度L^*值和色相b^*值减小,而色相a^*值、色度C^*值和色度角h值增大,叶绿素含量逐渐下降,类胡萝卜素、花色素苷和总黄酮含量逐渐升高;黄色紫茉莉花冠由淡绿色转变为黄色,盛开期具有最高的色度C^*值、色相a^*值和b^*值,整个开花过程具有较稳定的叶绿素和总黄酮含量,同时具有较高的类胡萝卜素含量;白色紫茉莉花冠由淡绿色转变为白色,过渡期具有最高的明度L^*值、色度C^*值、色相a^*值和b^*值,整个开花过程花色素苷和总黄酮含量较低,但随着开花进程逐渐升高,而类胡萝卜素含量稳定,过渡期总叶绿素含量显著低于其他2个时期。可见,不同花色紫茉莉开花过程中花色变化规律存在差异,而其差异性与其相应的色素成分变化密切相关。     

SENSORY EVALUATION OF INDIAN-STYLE MARINATED CHICKEN BY MALAYSIAN AND EUROPEAN NAÏVE ASSESSORS

This study was carried out to determine the sensory acceptability of chicken breast fillets marinated with 13 different commercially available Indian-style marinades. Thirty-four naïve assessors (untrained panelists), 20 Malaysian and 14 European, were selected to assess the following sensory attributes: color, color uniformity, Tikka-Masala aroma, Tikka-Masala flavor, herblike flavor, hotness, authenticity, juiciness and overall acceptability. The color of the cooked samples and the pH, moisture and fat content of the marinades were analyzed instrumentally. Marinades were applied to the chicken fillets, which were then dry cooked at 170C for 15 min to an internal temperature of 73C. Sensory evaluation showed significant differences ( P <  0.05) in color uniformity, hotness and juiciness of the cooked marinated chicken perceived between groups. Samples marinated with marinades L and I received the highest score from the Malaysian panelists in terms of overall acceptability, whereas marinades A and F were chosen by the European group.

PRACTICAL APPLICATIONS

The findings from this research will benefit manufacturers of marinade and marinated chicken products in developing or optimizing their products for the local and international markets. The optimal characteristics of an ideal marinade were identified for each assessor group. These results are also of interest to individuals undertaking cross-cultural consumer studies, even though the results presented here used naïve assessors.     

CONVERGENT EVOLUTION OF RED CAROTENOID COLORATION IN WIDOWBIRDS AND BISHOPS (EUPLECTES SPP.)

Avian carotenoid‐based signals are classic examples of sexually selected, condition‐dependent threat displays or mate choice cues. In many species, male dominance or mating success is associated with redder (i.e., longer wavelength) color hues, suggesting that red colors are either more efficient or more reliable signals than yellow colors. Few studies, however, have investigated selection for redness in a macroevolutionary context. Here, we phylogenetically reconstruct the evolution of carotenoid coloration in the African widowbirds and bishops (Euplectes spp.), for which agonistic selection for redder hues, as well as pigmentary mechanisms, is well documented. Using reflectance spectrometry for objective color quantification, and accounting for phylogenetic uncertainty, we find that yellow plumage color is a retained ancestral state in Euplectes, and that red color hues have convergently evolved two or three times. Results are discussed in relation to a known diversity in pigment mechanisms, supporting independent origins of red color, and suggesting that agonistic selection and physiological constraints have interacted to generate color diversity in Euplectes.     

Can Infants Tell the Difference between Gold and Yellow?

There is a large literature focused on the color perception of matte surface. However, recent research showed that the component of surface specular reflection, such as glossiness, also affects categorical color perception. For instance, the color term “gold” was used to name high specular stimuli within a specific range of chromaticity, which overlaps with those of yellow and orange for low specular stimuli. In the present study, we investigated whether the component of surface specular reflectance affects the color perception of 5- to 8-month-old infants by using the preferential looking technique. In the first experiment, we conducted a simple test to determine whether infants perceive yellow and gold as the same color by comparing their preference for these colors over green. If the infants perceive yellow and gold as the same color, they would show similar preference scores over green. On the other hand, if infants show different preference scores over green, it indicates that infants do not perceive yellow and gold as the same color. Only the 7–8 month-old infants showed different preference scores for gold and yellow over green. This result indicates that the 7–8 month-old infants perceive gold and yellow as different colors. In Experiment 2, we eliminated the component of specular reflectance on the gold surface and presented it against green to infants. A similar preference score of yellow over green was obtained. This result suggests that the difference between the preference scores for gold and yellow over green in Experiment 1 was based on representations of glossiness.     

用于柑桔成熟度无损检测的色度频度序列法研究

农产品内部品质无损检测技术是确定水果最合适的采收期和对成熟度不一致的农产品进行准确分级的关键．为了建立利用计算机视觉技术进行柑桔成熟度的无损检测的方法,本研究建立了用于柑桔成熟度检测的计算机视觉系统,研究了柑桔图像颜色的描述方法,通过分析比较,认为在利用水果可见光彩色图像检测水果成熟度时,宜采用HSI颜色模型空间;提出了用与各个色度对应的像素在图像中出现的频度构成的频度序列描述图像的颜色信息的新方法,并利用人工神经网络方法建立了根据柑桔图像的色度频度序列判断柑桔成熟度的映射器,这一映射器检验252只成熟度不同的尾张系柑桔的结果为,对成熟果实和未熟果实的判断正确率分别为 79 1％和63．6％,总的判断正确率为77．8％,这表明尾张系柑桔果实的表皮颜色与成熟度之间具有相关性,可以通过利用计算机视觉技术测定柑桔的表皮颜色信息来判断柑桔的成熟度．     

Visual wavelength discrimination by the loggerhead turtle, Caretta caretta

Marine turtles are visual animals, yet we know remarkably little about how they use this sensory capacity. In this study, our purpose was to determine whether loggerhead turtles could discriminate between objects on the basis of color. We used light-adapted hatchlings to determine the minimum intensity of blue (450 nm), green (500 nm), and yellow (580 nm) visual stimuli that evoked a positive phototaxis (the phototaxis "threshold" [pt]). Juvenile turtles were later trained to associate each color (presented at 1 log unit above that color's pt) with food, then to discriminate between two colors (the original rewarded stimulus plus one of the other colors, not rewarded) when both were presented at 1 log unit above their pt. In the crucial test, turtles were trained to choose between the rewarded and unrewarded color when the colors varied in intensity. All turtles learned that task, demonstrating color discrimination. An association between blue and food was acquired in fewer trials than between yellow and food, perhaps because some prey of juvenile loggerheads in oceanic surface waters (jellyfishes, polyps, and pelagic gastropods) are blue or violet in color.     

Divisionistic generation of skin hue and the change of shade in the scalycheek damselfish, Pomacentrus lepidogenys

In addition to melanophores and xanthophores, there existed two types of iridophore in the dermis of the scalycheek damselfish, Pomacentrus lepidogenys. There are dendritic iridophores which reflect white light-rays by Tyndall scattering, and the round or somewhat ellipsoidal iridophores which reflect rays with a relatively narrow spectral peak from blue to green through the non-ideal thin-film interference. Most of the dendritic iridophores were covered with xanthophores and were situated over melanophores, thus constituting a kind of chromatophore unit which produces a yellow or yellowish-green color. The characteristic yellowish-green hue of the integument results from a compound effect of small contributions by more elementary colors. During color changes of the skin, the position of the spectral peak does not shift. Unlike the iridophores of the blue damselfish, both types of iridophore of the scalycheek damselfish were found to be inactive. It appears, therefore, that the aggregation and dispersion of pigment within the melanophores is the primary mechanism responsible for the changes in color of this species.     

Effect of color hue and brightness of artificial oviposition substrates on the selection of oviposition site by Dacus oleae

In laboratory experiments of the choice type, olive fruit flies, Dacus oleae (Gmelin), wild and/or olivereared for a few generations, showed strong preference for oviposition in yellow and orange colored ceresin wax domes 18 mm in diameter. Green colored domes of two different hues were less preferred, while red, blue, black and white domes received a limited number of eggs when a preferred color was present. The females more frequently visited the domes of the preferred colors, which indicates that they selected them before arrival. The observed preference for certain colors like yellow and orange depended primarily on the color hue and not on the intensity of the total reflected light or on the degree to which the colored domes contrasted with the background. The females responded positively to hues reflecting maximally between 560 and 610 nm, optinum at ca. 580 nm. Hues reflecting maximally between 520 and 550 nm or above 610 nm were not very attractive while hues reflecting below 520 nm and especially between 400 and 480 nm appeared to be rather unattractive. There were indications that not only the spectral purity of a hue but also the quantity of the energy reflected within the narrow spectral region which corresponds to that hue are important for the selection of the oviposition site by this fly.

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Der einfluss von farbtönen und farbintensität künstlicher eiablagesubstrate auf ihre auswahl für die eiablage bei Dacus oleae

Zusammenfassung In Auswahlversuchen im Labor bevorzugten wilde und für einige Generationen im Labor auf Oliven gezüchtete Olivenfliegenweibchen zur Eiablage gelb und orange gefärbte Ceresinwachsdome von 18 mm Durchmesser. Grüngefärbte Dome von zwei verschiedenen Farbtönen waren weniger bevorzugt. Rote, blaue, schwarze und weisse Dome wurden mit einer begrenzten Anzahl Eiern belegt, wenn eine der bevorzugten Farben dabei war. Die Weibchen besuchten öfter die Dome mit den bevorzugten Farben, was darauf hindeutet, dass sie diese vor der Ankunft auswählten.Die beobachtete Bevorzugung für gewisse Farben wie gelb und orange hing hauptsächlich von den Farbtönen ab und nicht von der Intensität des total reflektierten Lichtes oder der Stärke des Kontrastes der farbigen Dome vom Hintergrund. Die Weibchen reagierten positiv auf Farbtöne mit einer maximalen Reflektion zwischen 560 und 610 nm mit einem Optimum bei ca. 580 nm. Farbtöne, die maximal zwischen 520 und 550 nm oder bei mehr als 610 nm reflektierten, waren nicht sehr attraktiv und Farbtöne mit einer Reflektion bei weniger als 520 nm, speziell zwischen 400 und 480 nm, scheinen nicht attraktiv zu sein. Es bestehen Hinweise dafür, dass nicht nur die Farbreinheit sondern auch die Menge der reflektierten Energie des entsprechenden Spektralabschnittes wichtig für die Auswahl der Eiablagesubstrate ist.

     

Pollen competition between morphs in a pollen‐color dimorphic herb and the loss of phenotypic polymorphism within populations

Flower color polymorphism is relatively uncommon in natural flowering plants, suggesting that maintenance of different color morphs within populations is difficult. To address the selective mechanisms shaping pollen‐color dimorphism, pollinator preferences and reproductive performance were studied over three years in Epimedium pubescens in which some populations had plants with either green or yellow pollen (and anthers). Visitation rate and pollen removal and receipt by the bee pollinator (Andrena emeishanica) did not differ between the two color morphs. Compared to the green morph, siring success of the yellow morph's pollen was lower, but that of mixtures of pollen from green and yellow morphs was lowest. This difference, corresponding to in vivo and ex vivo experiments on pollen performance, indicated that pollen germination, rather than tube growth, of the green morph was higher than that of the yellow morph and was seriously constrained in both morphs if a pollen competitor was present. A rare green morph may invade a yellow‐morph population, but the coexistence of pollen color variants is complicated by the reduced siring success of mixed pollinations. Potential pollen competition between morphs may have discouraged the maintenance of multiple phenotypes within populations, a cryptic mechanism of competitive exclusion.