Introduction
Few abstract categories, if any, are marked unambiguously, both objectively and subjectively. Sex and gender, however, aside from their polymorphous cultural and political semantics, constitute precisely such categories. On the one hand, sex is marked, unambiguously and universally, by the
sexual dimorphism of skin color—an objective, evolved physical reality. Universally, females carry a lighter skin than males (Frost,
1988; Jablonski & Chaplin,
2000). On the other hand, this objective dimorphism is anchored culturally on a brightness dimension in the case of gender, a socially constituted abstract category (e.g., Semin & Palma,
2014; Semin, Palma, Acartürk, & Dziuba,
2018). It is a representation that escapes conscious access (e.g., Carrito & Semin,
2019). Indeed, the anchoring of gender on the brightness dimension appears to be consistent across different cultures such as the Portuguese, Dutch, and Turkish cultures (i.e., Semin & Palma,
2014; Semin et al.,
2018).
In short, objectively females have a lighter skin color than males irrespective of geographical location (e.g., Jablonski & Chaplin,
2018) and this difference is a distinctive and universal adaptive pattern (Jablonski,
2004; Jablonski & Chaplin,
2000,
2002). To complement this objective phenomenon, culturally the alignment of female–male with the bipolar dimension of light–dark has been demonstrated across a sample of European cultures. There are two questions that are addressed in the research reported here. The first is: can the grounding of gender on the brightness dimension be generalized to a non-Western, non-industrialized population, namely the Wichí (Salta, Argentina)? The second question we addressed was whether a sample of prepubescent children aged 6 to 9 years has the same grounding of gender on a brightness dimension? This age range is significant because it is well known that the sexual dimorphism of skin color emerges only after puberty and is not a feature prominent in the younger age groups that we targeted (see Robins,
1991). To address these questions, we conducted two studies with children and adults, namely one with a Wichí sample and one with a Spanish sample.
In the following, we start with a brief overview of the literature on the sexual dimorphism of skin color. We then turn to the research on the association between gender and brightness and then present an overview of the current research.
Sexual dimorphism in skin color as a result of natural selection
It is only recent that the difference in skin coloration between males and females has been objectively established and that the evolutionary bases as well as the adaptive function of this dimorphism have been systematically examined. The data based on analyses of unexposed skin areas collected in all the populations that have been studied indicate that women have a lighter skin than men (Jablonski,
2013; Jablonski & Chaplin,
2010), ruling out the possible argument that outdoor time budget can account for the differences between males and females. Moreover, this difference holds across latitudes, namely it is orthogonal to geographical variations in skin pigmentation.
A variety of arguments have been advanced to account for this phenomenon. It has been argued that the sexual dimorphism in skin color is the result of
sexual selection, either because men preferentially select lighter female skin, or as a product of sexual competition between females, or even to reduce male aggressiveness. It is, however, the hypothesis advanced by Jablonski and Chaplin (e.g.,
2000) that has garnered considerable empirical support. According to these authors, sexual dimorphism is primarily driven by
natural selection (see also Madrigal & Kelly,
2007). Thus, skin pigmentation is an adaptive trait resulting from the tradeoff between protection against ultraviolet radiation (UVR) (provided by darker skin tones) and production of vitamin D (enhanced by lighter skin tones). Females need to maximize the synthesis of vitamin D during pregnancy and lactation to increase their infant’s and their own biological fitness. Therefore, they benefit from having a lighter skin. In contrast, darker skin pigmentation may have been the result of natural selection in males as it optimizes the folate levels in body, which in turn safeguard sperm production. “Because folate is essential for the synthesis of DNA in dividing cells, anything that involves rapid cell proliferation, such as spermatogenesis (the production of sperm cells), requires folate” (Jablonski & Chaplin,
2002, p. 170). Thus, sexual dimorphism in skin color is adaptive for both females and males.
Interestingly, sex differences in skin color emerge late in development (Jablonski,
2012; Paik et al.,
2012; Robins,
1991). Girls and boys are born with similar skin pigmentation. Through puberty, the skin of children progressively darkens with no differences between sexes prior to adolescence. Around the ages of 14–16, the skin lightens for both sexes, but the lightening process is more accentuated in females, producing the sex difference in skin color by the end of adolescence (e.g., Kalla & Tiwari,
1970; Mesa,
1983). These developmental trends in skin pigmentation are driven by sex hormones (Jablonski,
2013; Robins,
1991).
Conceptions of male and female skin color
Inspired by Jablonski’s work (e.g.,
2012), Semin and his colleagues have investigated the cognitive representation of the sexual dimorphism in skin color. Do people have an explicitly accessed representation of the difference in skin color between males and females? When participants are asked about the nature of the male–female skin color, then the majority claim that there is no difference in skin color between males and females (Carrito & Semin,
2019). Nevertheless, their performance on a variety of tasks demonstrates that differences between the genders in skin color implicitly drive their performances on a variety of implicit cognitive tasks.
For instance, in a set of speeded classification tasks, Portuguese and Dutch adults were shown to process masculine names faster when they were presented in dark colors as compared to light colors, and the reverse was true for feminine names (e.g., Semin & Palma,
2014). Moreover, when presented with unreadable names in the form of black and white blobs, a sample of Portuguese participants was significantly more likely to classify them as males when they came in black and as females when they came in white, even if they were not able to identify a name at all (Semin et al.,
2018). The dimension of brightness not only drives the categorization of females and males, but also the attribution of gender-based preferences. In a choice study presenting a series of commercial objects, Dutch participants inferred females’ and males’ commercial preferences on the basis of the objects’ brightness, namely they preferentially matched the dark object with the male character and the light object with the female character (Semin & Palma,
2014). In a similar experiment with Turkish adults using visual inspection as the dependent measure, they found that participants looked longer and made more eye fixations on dark objects when choosing for a male and vice versa for a female (Semin et al.,
2018). Finally, it was found that individuals not only expected female faces to be lighter than male faces but also were more likely to recall female faces as lighter and male faces as darker than originally presented, evincing the impact of the brightness–gender categorization on recognition memory (Carrito & Semin,
2019).
The research reported so far has been conducted with Western Industrial population samples and with adults. We know, however, that sex differences in skin color emerge late in development. It is only during puberty that the sexual dimorphism of skin color emerges raising the question if prepubescent children have the same implicit representation as adults. A second and equally important question is whether the same gender marking of skin color can be found in a non-industrialized culture. It is to these questions that we turned in the research we report below.
General discussion
Previous research established a consistent interface between the gender category and the brightness dimension in adults from three different industrialized populations and across a number of different experimental paradigms. Individuals not only classified feminine and masculine items according to their brightness, but also expected females to have lighter skin than males, suggesting that the gender categorization patterns are related to the perception of the sexual dimorphism in skin color. However, to provide stronger evidence for the association between skin color and gender marking, three further perspectives on this association are required: Does the demonstrated gender marking hold across populations with distinctly different (a) skin tones; (b) cultural contexts; and (c) age groups? The current research addresses these questions by relying on a new Western population (Spanish) and non-industrialized population with a darker skin (Wichí) (Robins,
1991), and by exploring the developmental differences of this association between children aged 6 to 9 and adults from the two cultural communities. Crucially, according to the anthropological findings (e.g., Jablonski,
2013), children of these ages are still sexually undifferentiated with respect to their skin color.
In both Spanish and Wichí populations, we found a significant effect of the gender of the target for whom a choice was made, and the type of object chosen. Participants preferentially chose the light object for female characters and the dark object for male characters. This was true for children and adults, but the sexual classification pattern was different in the Wichí and Spanish samples. In the case of Spanish adults, none of the other predictor variables explored were significant, indicating that the interface between brightness and gender emerges regardless of the gender of participants, and the color and position of the objects. This finding extends previous results on other industrialized populations, namely Dutch, Portuguese and Turkish adults. Spanish children showed the same trend with no differences across ages, suggesting that the gender–brightness association is already well established by the age of 6, and remained unchanged, at least, until the beginning of puberty.
In the case of the Wichí participants, an unexpected effect of participant gender was observed. Female participants were more likely to assign light-female and dark-male than were male participants. As a matter of fact, these gender differences were more pronounced with age. In the case of the Wichí sample of children, the interface between gender and brightness was found both in boys and girls but the latter displayed a more consistent pattern than the former. However, in adults, the gender marking seemed to be exclusively driven by the female participants’ choices, with males choosing the light and dark objects at chance level. An account for this pattern of results has to be speculative given that we have no data to drive out potential accounts. One possible reason may be of a methodological nature. The person in charge of testing was a female researcher and could have produced a distorting effect in male participants, such as low levels of engagement with the task triggered by a more suspicious attitude toward a (foreign) female in an authority position. This kind of effect of female researchers in cross-cultural fieldwork has been widely explored some decades ago (e.g., Arendell,
1997; Turnbull,
1986; Easterday, Papademas, Schorr, & Valentine,
1977; Warren,
1988). Although none of these studies was conducted in Wichí populations, it is possible that similar problems had arisen in the current research. Moreover, the males of our study started to display a less defined pattern of choices for the objects by the age when the children in the Wichí communities begin to participate in gender-differentiated activities and spend considerable time with same-sex adults (Arenas,
2003; Montani,
2008,
2012). This may mean an asymmetrical exposure to adult males and females for boys, who step away from the domestic space occupied by females and elders of both sexes, and before puberty, start to be part of the male tasks such as field trips (Montani,
2008,
2012). This could explain why Wichí boys were less likely to align gender with the brightness dimension when presented with female characters as compared to male characters.
Contrary to our predictions, the children from both cultures already displayed a consistent gender–brightness association. One possible account for this finding is that the acquisition of the gender–brightness interface goes back to the earliest formation of gender representations. All known cultural communities have some division of roles and duties based on a person’s gender, and this is reflected in their gender representations (Maccoby,
1988). A large body of research indicates that around the age of 3–4 years, children already show a basic understanding of the sex differences associated with possessions, physical appearance, roles, toys, and activities (for a recent review see Martin & Ruble,
2010). Not only children possess conventional knowledge related to gender by these ages, but they also start to recognize some rudimentary metaphorical associations with the gender category, and attribute abstract features to females (e.g., softness) and males (e.g., hardness) (Leinbach, Hort, & Fagot,
1997; Weinraub et al.,
1984). Whether or not these early gender representations are already grounded with brightness is a subject that requires research.
Another implication for the early emergence of the gender–brightness link is related to the sources from which individuals could implicitly exploit regularities regarding the sexual difference in skin color. We have considered two main sources that provide observational material: their surrounding males and females, and the media. Yet, apart from visual observation, individuals can also extract information about their environment from the use of their language, namely their linguistic ecology. Indeed, the linguistic context in which a particular word occurs is a key part of its representation (Casasanto & Lupyan,
2015). As such, the co-occurrence of words related to male-dark and female-light, respectively, could lead to the acquisition of “implicit” knowledge about the gender–brightness relation. The works on artificial grammar learning demonstrated that even infants as young as 10 months old are able to learn the predictive relations between linguistic items with only a brief and passive exposure to the conditional probabilities of occurrence (e.g., Gómez & Gerken,
2000; Reber,
1967; Saffran,
2003). Therefore, it is possible that as soon as children are exposed to linguistic stimuli that encompass the probabilistic association between gender and brightness, they implicitly start to generate differential representations of males and females based on brightness.
Another interesting finding, consistent across cultures, is that children presented a more distinct gender–brightness pattern than did adults. We expected to find the reverse pattern based on the fact that prepubescent girls and boys have still similar skin tone and, therefore, are less likely to extract the sexual discrepancy regularities from their own peers.
While we claim the gender grounding with brightness is universal as it is derived from a universal sexual dimorphism in skin color, culture adds layers of interpretation on the interface between gender and brightness. In many, but not all cultures, white is also associated with purity, chastity, innocence, and black is associated with authority, knowledge, war, and this further contributes to the implicit representations of males and females. It is possible that as individuals progressively enrich their implicit representations of gender throughout development, the interface with brightness becomes less accentuated.
Taken together these findings give partial support to the relation between the sex dimorphism in skin color and the gender grounding with brightness. The interface between gender and brightness was not only found in a previously not studied industrialized population (i.e., Spanish), but also in adults from a non-industrialized population with darker skin (i.e., Wichí), although the latter effect was confined to female adults. Therefore, future research should explore other populations to examine the universality of the gender–brightness link.
One of the central contributions of this research is to the developmental roots of the gender–brightness association. We find that already by the age of 6, children from the two different cultures associate the bipolar light–dark dimension with the female–male category, and they did so in a more consistent way than adults. This suggests that the physical evidence (i.e., sex discrepancy in skin color) obtained via “online” observation or through media exposure is not the only force driving the gender marking acquisition. Conversely, it is likely that the skin color regularities are transduced into linguistic patterns (such as the co-occurrence of words related to female-light and male-dark, respectively) within a particular linguistic community and this could contribute to the acquisition of the gender grounding.
Humans often rely on sensorimotor experiences to ground abstract concepts. For instance, the concept of time as movement is grounded by space but with no invariant reference. Therefore, the spatial representations of time are variable around the world. Thus, the way people structure time in space is affected by cultural artifacts that serve as reference points for movement as, for example, writing direction (e.g., Fuhrman & Boroditsky,
2010). This results in cultural differences in the time–space association and how time is grounded. Likewise, gender is also anchored on a sensory dimension, namely the brightness–darkness. However, the marking of gender presents a special case. In contrast to the space–time association, the marking of gender is probably a universal as males and females as grounding referents (i.e., their skin color) are universally dark and light.
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