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Concept: Color


Is there a link between the color of a taxi and how many accidents it has? An analysis of 36 mo of detailed taxi, driver, and accident data (comprising millions of data points) from the largest taxi company in Singapore suggests that there is an explicit link. Yellow taxis had 6.1 fewer accidents per 1,000 taxis per month than blue taxis, a 9% reduction in accident probability. We rule out driver difference as an explanatory variable and empirically show that because yellow taxis are more noticeable than blue taxis-especially when in front of another vehicle, and in street lighting-other drivers can better avoid hitting them, directly reducing the accident rate. This finding can play a significant role when choosing colors for public transportation and may save lives as well as millions of dollars.

Concepts: Color, Green, Yellow, Primary color, Complementary color, Color wheel, Taxicab, Indigo


We tested whether eye color influences perception of trustworthiness. Facial photographs of 40 female and 40 male students were rated for perceived trustworthiness. Eye color had a significant effect, the brown-eyed faces being perceived as more trustworthy than the blue-eyed ones. Geometric morphometrics, however, revealed significant correlations between eye color and face shape. Thus, face shape likewise had a significant effect on perceived trustworthiness but only for male faces, the effect for female faces not being significant. To determine whether perception of trustworthiness was being influenced primarily by eye color or by face shape, we recolored the eyes on the same male facial photos and repeated the test procedure. Eye color now had no effect on perceived trustworthiness. We concluded that although the brown-eyed faces were perceived as more trustworthy than the blue-eyed ones, it was not brown eye color per se that caused the stronger perception of trustworthiness but rather the facial features associated with brown eyes.

Concepts: Eye, Photoreceptor cell, Color, Qualia, Rod cell, Cone cell, Human eye, Eye color


Countershading was one of the first proposed mechanisms of camouflage [1, 2]. A dark dorsum and light ventrum counteract the gradient created by illumination from above, obliterating cues to 3D shape [3-6]. Because the optimal countershading varies strongly with light environment [7-9], pigmentation patterns give clues to an animal’s habitat. Indeed, comparative evidence from ungulates [9] shows that interspecific variation in countershading matches predictions: inĀ open habitats, where direct overhead sunshine dominates, a sharp dark-light color transition high up the body is evident; in closed habitats (e.g., under forest canopy), diffuse illumination dominates and a smoother dorsoventral gradation is found. We can apply this approach to extinct animals in which the preservation of fossil melanin allows reconstruction of coloration [10-15]. Here we present a study of an exceptionally well-preserved specimen of Psittacosaurus sp. from the Chinese Jehol biota [16, 17]. This Psittacosaurus was countershaded [16] with a light underbelly and tail, whereas the chest was more pigmented. Other patterns resemble disruptive camouflage, whereas the chin and jugal bosses on the face appear dark. We projected the color patterns onto an anatomically accurate life-size model in order to assess their function experimentally. The patterns are compared to the predicted optimal countershading from the measured radiance patterns generated on an identical uniform gray model in direct versus diffuse illumination. These studies suggest that Psittacosaurus sp. inhabited a closed habitat such as a forest with a relatively dense canopy. VIDEO ABSTRACT.

Concepts: Habitat, Light, Sunlight, Color, Lighting, Pigment, Paleontology, Dinosaur


Non-human primates evaluate food quality based on brightness of red and green shades of color, with red signaling higher energy or greater protein content in fruits and leafs. Despite the strong association between food and other sensory modalities, humans, too, estimate critical food features, such as calorie content, from vision. Previous research primarily focused on the effects of color on taste/flavor identification and intensity judgments. However, whether evaluation of perceived calorie content and arousal in humans are biased by color has received comparatively less attention. In this study we showed that color content of food images predicts arousal and perceived calorie content reported when viewing food even when confounding variables were controlled for. Specifically, arousal positively co-varied with red-brightness, while green-brightness was negatively associated with arousal and perceived calorie content. This result holds for a large array of food comprising of natural food - where color likely predicts calorie content - and of transformed food where, instead, color is poorly diagnostic of energy content. Importantly, this pattern does not emerged with nonfood items. We conclude that in humans visual inspection of food is central to its evaluation and seems to partially engage the same basic system as non-human primates.

Concepts: Human, Eye, Vision, Visual system, Color, Primate, Hominidae, New World monkey


Synesthesia is a phenomenon where a stimulus produces consistent extraordinary subjective experiences. A relatively common type of synesthesia involves perception of color when viewing letters (e.g. the letter ‘a’ always appears as light blue). In this study, we examine whether traits typically regarded as markers of synesthesia can be acquired by simply reading in color.

Concepts: Light, Color, Green, Blue, Purple, Qualia, Synesthesia, Azure


Structural colors are generated by scattering of light by variations in tissue nanostructure. They are widespread among animals and have been studied most extensively in butterflies and moths (Lepidoptera), which exhibit the widest diversity of photonic nanostructures, resultant colors, and visual effects of any extant organism. The evolution of structural coloration in lepidopterans, however, is poorly understood. Existing hypotheses based on phylogenetic and/or structural data are controversial and do not incorporate data from fossils. Here we report the first example of structurally colored scales in fossil lepidopterans; specimens are from the 47-million-year-old Messel oil shale (Germany). The preserved colors are generated by a multilayer reflector comprised of a stack of perforated laminae in the scale lumen; differently colored scales differ in their ultrastructure. The original colors were altered during fossilization but are reconstructed based upon preserved ultrastructural detail. The dorsal surface of the forewings was a yellow-green color that probably served as a dual-purpose defensive signal, i.e. aposematic during feeding and cryptic at rest. This visual signal was enhanced by suppression of iridescence (change in hue with viewing angle) achieved via two separate optical mechanisms: extensive perforation, and concave distortion, of the multilayer reflector. The fossils provide the first evidence, to our knowledge, for the function of structural color in fossils and demonstrate the feasibility of reconstructing color in non-metallic lepidopteran fossils. Plastic scale developmental processes and complex optical mechanisms for interspecific signaling had clearly evolved in lepidopterans by the mid-Eocene.

Concepts: Evolution, Insect, Color, Lepidoptera, Fossil, Paleontology, Butterfly


In human vision, acuity and color sensitivity are greatest at the center of fixation and fall off rapidly as visual eccentricity increases. Humans exploit the high resolution of central vision by actively moving their eyes three to four times each second. Here we demonstrate that it is possible to classify the task that a person is engaged in from their eye movements using multivariate pattern classification. The results have important theoretical implications for computational and neural models of eye movement control. They also have important practical implications for using passively recorded eye movements to infer the cognitive state of a viewer, information that can be used as input for intelligent human-computer interfaces and related applications.

Concepts: Brain, Human, Retina, Eye, Visual perception, Visual system, Saccade, Color


Billions of birds are estimated to be killed in window collisions every year, worldwide. A popular solution to this problem may lie in marking the glass with ultraviolet reflective or absorbing patterns, which the birds, but not humans, would see. Elegant as this remedy may seem at first glance, few of its proponents have taken into consideration how stark the contrasts between ultraviolet and human visible light reflections or transmissions must be to be visible to a bird under natural conditions. Complicating matters is that diurnal birds differ strongly in how their photoreceptors absorb ultraviolet and to a lesser degree blue light. We have used a physiological model of avian colour vision to estimate the chromatic contrasts of ultraviolet markings against a natural scene reflected and transmitted by ordinary window glass. Ultraviolets markings may be clearly visible under a range of lighting conditions, but only to birds with a UVS type of ultraviolet vision, such as many passerines. To bird species with the common VS type of vision, ultraviolet markings should only be visible if they produce almost perfect ultraviolet contrasts and are viewed against a scene with low chromatic variation but high ultraviolet content.

Concepts: Human, Mathematics, Light, Bird, Color, Estimation, Visible spectrum, Color vision


A basic premise of the recently proffered color-in-context model is that the influence of color on psychological functioning varies as a function of the psychological context in which color is perceived. Some research has examined the appetitive and aversive implications of viewing the color red in romance- and achievement-relevant contexts, respectively, but in all existing empirical work approach and avoidance behavior has been studied in separate tasks and separate experiments. Research is needed to directly test whether red influences the same behavior differently depending entirely on psychological context.

Concepts: Psychology, Science, Color, Green, Red, Primary color, RGB color model, Visible spectrum


BACKGROUND: Coloured-hearing (CH) synesthesia is a perceptual phenomenon in which an acoustic stimulus (the inducer) initiates a concurrent colour perception (the concurrent). Individuals with CH synesthesia “see” colours when hearing tones, words, or music; this specific phenomenon suggesting a close relationship between auditory and visual representations. To date, it is still unknown whether the perception of colours is associated with a modulation of brain functions in the inducing brain area, namely in the auditory-related cortex and associated brain areas. In addition, there is an on-going debate as to whether attention to the inducer is necessarily required for eliciting a visual concurrent, or whether the latter can emerge in a pre-attentive fashion. RESULTS: By using the EEG technique in the context of a pre-attentive mismatch negativity (MMN) paradigm, we show that the binding of tones and colours in CH synesthetes is associated with increased MMN amplitudes in response to deviant tones supposed to induce novel concurrent colour perceptions. Most notably, the increased MMN amplitudes we revealed in the CH synesthetes were associated with stronger intracerebral current densities originating from the auditory cortex, parietal cortex, and ventral visual areas. CONCLUSIONS: The automatic binding of tones and colours in CH synesthetes is accompanied by an early pre-attentive process recruiting the auditory cortex, inferior and superior parietal lobules, as well as ventral occipital areas.

Concepts: Brain, Cerebrum, Perception, Color, Sense, Thalamus, Qualia, Philosophy of perception