Female ornaments: is red skin color attractive to males and related to condition in rhesus macaques?

Sexual selection produces extravagant male traits, such as colorful ornaments, via female mate choice. More rarely, in mating systems in which males allocate mating effort between multiple females, female ornaments may evolve via male mate choice. Females of many anthropoid primates exhibit ornaments that indicate intraindividual cyclical fertility, but which have also been proposed to function as interindividual quality signals. Rhesus macaque females are one such species, exhibiting cyclical facial color variation that indicates ovulatory status, but in which the function of interindividual variation is unknown. We collected digital images of the faces of 32 rhesus macaque adult females. We assessed mating rates, and consortship by males, according to female face coloration. We also assessed whether female coloration was linked to physical (skinfold fat, body mass index) or physiological (fecal glucocorticoid metabolite [fGCM], urinary C-peptide concentrations) condition. We found that redder-faced females were mated more frequently, and consorted for longer periods by top-ranked males. Redder females had higher fGCM concentrations, perhaps related to their increased mating activity and consequent energy mobilization, and blood flow. Prior analyses have shown that female facial redness is a heritable trait, and that redderfaced females have higher annual fecundity, while other evidence suggests that color expression is likely to be a signal rather than a cue. Collectively, the available evidence suggests that female coloration has evolved at least in part via male mate choice. Its evolution as a sexually selected ornament attractive to males is probably attributable to the high female reproductive synchrony found in this species

Do nonhuman animals reason about prestige-based status?

Status is a complex, but crucially important, aspect of life across species. In recent decades, researchers have made significant contributions to our understanding of both the pathways by which status can be attained, as well as our underlying capacities for reasoning about these pathways. In 2001, Henrich & Gil-White proposed a prestige-based pathway to status where low status actors willingly defer to competent or knowledgeable high status actors, as a means of facilitating social learning and cultural transmission. Although this type of status hierarchy, and the capacity to reason about it, was hypothesized to be unique to humans, here I argue that there are several reasons why we might observe prestige-based status, and the capacity for reasoning about this pathway to status, in some nonhuman species as well. These reasons focus on the prevalence, importance, and sophistication of social learning in certain taxa, as well as the marked variation in hierarchy characteristics and structure across species. I point out places where our current methodologies encounter difficulties distinguishing whether a hierarchy in the wild is based on dominance or prestige, where our experimental methods leave us unable to assess whether an individual is reasoning about a high status actor as being prestigious or formidable, and provide suggestions for addressing these limitations. Adopting a comparative approach will clarify whether prestige-based status truly is unique to humans, and—if not—precisely what selective pressures facilitate the emergence of prestige-based status and the capacity for reasoning about it

The nature and consequences of essentialist beliefs about race in early childhood

It is widely believed that race divides the world into biologically distinct kinds of people – an essentialist belief inconsistent with reality. Essentialist views of race have been described as early emerging, but the present study found that young children (n = 203, Mage = 5.45) hold only the more limited belief that the physical feature of skin color is inherited and stable. Overall, children rejected the causal essentialist view that behavioral and psychological characteristics are constrained by an inherited racial essence. Although average levels of children’s causal essentialist beliefs about race were low, variation in these beliefs was related to children's own group membership, exposure to diversity, as well as children’s own social attitudes

Boys and girls, men and women: Do children take stimulus age into account when expressing gender stereotypes?

Gender and age are salient social categories from early in development. However, whether children’s beliefs about gender and age intersect, such that gender stereotypes might be expressed differently when asked about children (as compared to adults) has not been investigated. Here, in a pre-registered study (N = 297), we examined if young children (3.0 – 6.9-year-olds, Mage = 5.03 years, n = 145) and adults (n = 152) across Massachusetts were more likely to express gender stereotypes when presented with child or adult stimuli. Participants were presented with 20 questions about gender stereotyped behavioral and psychological properties and selected their response (male or female) for each question by selecting between four child faces (2 White boys, 2 White girls) or four adult faces (2 White men, 2 White women) across two separate blocks. Overall, both children and adults expressed gender stereotypes above chance, and, in children, expression of stereotypes increased across the age range. Although neither children nor adults applied gender stereotypes differently to child vs. adult visual stimuli, all participants were more likely to apply gender stereotypes when that stereotype was child-centric (e.g., about doing childish activities). Our results suggest that children could be vulnerable to stereotype content from an early age; however, future research should explore whether children show this same age-invariant pattern when both gender and age are made salient and directly contrasted (e.g., by presenting men, women, boys, and girls simultaneously)