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Bare skin, blood and the evolution of primate colour vision. Biology Letters, 2, 217-221

California Institute of Biology, Sloan-Swartz Center for Theoretical Neurobiology, MC 139-74, Caltech, Pasadena, CA 91125, USA.
Biology letters (Impact Factor: 3.25). 07/2006; 2(2):217-21. DOI: 10.1098/rsbl.2006.0440
Source: PubMed

ABSTRACT

We investigate the hypothesis that colour vision in primates was selected for discriminating the spectral modulations on the skin of conspecifics, presumably for the purpose of discriminating emotional states, socio-sexual signals and threat displays. Here we show that, consistent with this hypothesis, there are two dimensions of skin spectral modulations, and trichromats but not dichromats are sensitive to each. Furthermore, the M and L cone maximum sensitivities for routine trichromats are optimized for discriminating variations in blood oxygen saturation, one of the two blood-related dimensions determining skin reflectance. We also show that, consistent with the hypothesis, trichromat primates tend to be bare faced.

    • "While a number of aspects of our response to colour appear to be hard-wired through evolution (e.g. Changizi et al., 2006; Khan et al., 2011; Lehrl et al., 2007), many other aspects of our response to colour in food are learned (Maga, 1974; Garber et al., 2008; Shankar et al., 2010a). There is an interesting story to tell about the association between redness and sweetness in fruits (e.g. "
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    ABSTRACT: Although not mentioned as a constitutive element of flavour, at least according to the International Standards Organization definition, there can be little doubt that what we see exerts a profound effect on our perception of and behavioural responses toward food and drink. While there are many attributes of the consumer's visual experience that may be relevant here, the majority of the research published to date has involved varying the hue and intensity of the colouration in beverages. Here, evidence is reviewed demonstrating how not only the colour of the food or drink, but also the colour of the glassware, the packaging, the plateware, the cutlery, and even the colour of the environment in which we eat and drink, can all exert a (sometimes dramatic) effect on our perception of, and response to, a variety of food and beverage products. Several potential explanations for these results are outlined, including in terms of expectancy effects, generalized priming, and the indirect impact of colour on mood, and thereafter of mood on food. Given the variety of ways in which what we see can affect our responses to food and drink (note that more than 200 studies have been published on this topic), it seems likely that some combination of these various explanations may well be needed in order to fully explain the range of effects that have been documented to date when changing the colour has been shown to influence the taste and/or flavour of food and drink.
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    • "The face often flushes during anger (Darwin, 1965, Drummond and Quah, 2001, Montoya et al., 2005) or pleasure (Drummond, 1994), and becomes pale when experiencing fear (Drummond, 1997, Montoya et al., 2005). Changizi et al. (2006) claim that the primate color-vision system has evolved for the purpose of discriminating skin color to estimate the emotional states of others. Drummond (1997) found that respondents associated flushing with anger and pallor with fear, suggesting that we associate facial color with emotion and vice versa. "
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    ABSTRACT: Recent studies have suggested that both configural information, such as face shape, and surface information is important for face perception. In particular, facial color is sufficiently suggestive of emotional states, as in the phrases: "flushed with anger" and "pale with fear." However, few studies have examined the relationship between facial color and emotional expression. On the other hand, event-related potential (ERP) studies have shown that emotional expressions, such as fear, are processed unconsciously. In this study, we examined how facial color modulated the supraliminal and subliminal processing of fearful faces. We recorded electroencephalograms while participants performed a facial emotion identification task involving masked target faces exhibiting facial expressions (fearful or neutral) and colors (natural or bluish). The results indicated that there was a significant interaction between facial expression and color for the latency of the N170 component. Subsequent analyses revealed that the bluish-colored faces increased the latency effect of facial expressions compared to the natural-colored faces, indicating that the bluish color modulated the processing of fearful expressions. We conclude that the unconscious processing of fearful faces is affected by facial color.
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    • "This trait may be potentially informative to conspecifics of both sexes in a sexual context, providing information about both the condition and the competitive ability of the signaler. Indeed, skin color is influenced by blood oxygenation and flow and is thus closely linked to underlying physiology and condition (Changizi et al. 2006; Bradley and Mundy 2008). Furthermore, according to the immunohandicap hypothesis (Folstad and Karter 1992), because the hormone testosterone is an immunosuppressant, only individuals in good condition may be able to exhibit the most intense coloration. "
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    ABSTRACT: The effects of intrasexual and intersexual selection on male trait evolution can be difficult to disentangle, especially based on observational data. Male–male competition can limit an observer's ability to identify the effect of female mate choice independently from sexual coercion. Here, we use an experimental approach to explore whether an ornament, the red facial skin exhibited by male rhe-sus macaques (Macaca mulatta), might be involved in both female mate choice and male–male competition. We used a noninvasive experimental approach based on the looking time paradigm in a free-ranging setting, showing images of differently colored male faces to both adult females (N = 91) and males (N = 77), as well as to juveniles (N = 94) as a control. Results show that both adult females and males looked longer at dark red faces compared with pale pink ones. However, when considering the proportion of subjects that looked longer at dark red faces regardless of preference strength, only females showed a significant dark red bias. In contrast, juveniles did not show any preferences between stimuli, suggesting that the adult bias is not a consequence of the experimental design or related to a general sensory bias for red coloration among all age–sex classes. Collectively, these results support the role the ornament plays in female mate choice in this species and provide the first evidence that this ornament may play a role in male–male competition as well, despite a general lack of observational evidence for the latter effect to date.
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