A critique of life history approaches to human trait covariation

Covariation of life history traits across species may be organised on a ‘fast-slow’ continuum. A burgeoning literature in psychology and social science argues that trait covariation should be similarly organised across individuals within human populations. Here we describe why extrapolating from inter-species to inter-individual trait covariation is not generally appropriate. The process that genetically tailors species to their environments (i.e. Darwinian evolution) is fundamentally different from processes that tailor individuals to their environments (e.g. developmental plasticity), so their outcomes in terms of trait covariation need not be parallel or even related. We discuss why correlational selection, physical linkage, pleiotropy, and non-random mating do not substantively affect this claim in the context of complex human traits. We also discuss life history trade-offs and their relation to inter-individual trait covariation. We conclude that researchers should avoid hypotheses and explanations that assume trait covariation will correspond across and within species, unless they can mount a theoretically coherent argument to support this claim in the context of their research question

Sex differences in misperceptions of sexual interest can be explained by sociosexual orientation and men projecting their own interest onto women

Sex differences in misperceptions of sexual interest have been well documented; however, it is unclear whether this cognitive bias could be explained by other factors. In the current study, 1226 participants (578 men, 630 women) participated in a speed-dating study, where participants rated their sexual interest in each other as well as the sexual interest they perceived from their partners. Consistent with previous findings, we found that men tended to overperceive sexual interest from their partners, while women tended to underperceive sexual interest. However, this sex difference becomes negligible when considering potential mediators, such as the raters’ sociosexual orientation, and raters projecting their own levels of sexual interest onto their partners. These findings challenge the popular notion that sex differences in misperceptions in sexual interest have evolved as a specialised adaptation due to different selection pressures in men and women

Microbes and masculinity: Does exposure to pathogenic cues alter women's preferences for male facial masculinity and beardedness?

Women’s preferences for men’s androgen dependent secondary sexual traits are proposed to be phenotypically plastic in response to exposure to pathogens and pathogen disgust. While previous studies report that masculinity in facial shape is more attractive to women who have recently been exposed to pathogenic cues and who are high in self-reported pathogen disgust, facial hair may reduce male attractiveness under conditions of high pathogens as beards are a possible breeding ground for disease carrying ectoparasites. In the present study, we test whether women’s preferences for beardedness and facial masculinity vary due to exposure to different pathogenic cues. Participants (N = 688, mean age + 1SD = 31.94 years, SD = 6.69, range = 18–67) rated the attractiveness of facial composite stimuli of men when they were clean-shaven or fully bearded. These stimuli were also manipulated in order to vary sexual dimorphism by ±50%. Ratings were conducted before and after exposure to one of four experimental treatments in which participants were primed to either high pathogens (e.g. infected cuts), ectoparasites (e.g. body lice), a mixture of pathogens and ectoparasites, or a control condition (e.g. innocuous liquids). Participants then completed the three-domain disgust scale measuring attitudes to moral, sexual and pathogen disgust. We predicted that women would prefer facial masculinity following exposure to pathogenic cues, but would show reduced preferences for facial hair following exposure to ectoparasites. Women preferred full beards over clean-shaven faces and masculinised over feminised faces. However, none of the experimental treatments influenced the direction of preferences for facial masculinity or beardedness. We also found no association between women’s self-reported pathogen disgust and their preferences for facial masculinity. However, there was a weak positive association between moral disgust scores and preferences for facial masculinity, which might reflect conservatism and preferences for gender typicality in faces. Women’s preferences for beards were positively associated with their pathogen disgust, which runs contrary to our predictions and may reflect preferences for high quality individuals who can withstand any costs of beardedness, although further replications are necessary before firm conclusions can be made. We conclude that there is little support for pathogenic exposure being a mechanism that underpins women’s directional preferences for masculine traits

A multivariate analysis of women's mating strategies and sexual selection on men's facial morphology

The strength and direction of sexual selection via female choice on masculine facial traits in men is a paradox in human mate choice research. While masculinity may communicate benefits to women and offspring directly (i.e. resources) or indirectly (i.e. health), masculine men may be costly as long-term partners owing to lower paternal investment. Mating strategy theory suggests women's preferences for masculine traits are strongest when the costs associated with masculinity are reduced. This study takes a multivariate approach to testing whether women's mate preferences are context-dependent. Women (n = 919) rated attractiveness when considering long-term and short-term relationships for male faces varying in beardedness (clean-shaven and full beards) and facial masculinity (30% and 60% feminized, unmanipulated, 30% and 60% masculinized). Participants then completed scales measuring pathogen, sexual and moral disgust, disgust towards ectoparasites, reproductive ambition, self-perceived mate value and the facial hair in partners and fathers. In contrast to past research, we found no associations between pathogen disgust, self-perceived mate value or reproductive ambition and facial masculinity preferences. However, we found a significant positive association between moral disgust and preferences for masculine faces and bearded faces. Preferences for beards were lower among women with higher ectoparasite disgust, providing evidence for ectoparasite avoidance hypothesis. However, women reporting higher pathogen disgust gave higher attractiveness ratings for bearded faces than women reporting lower pathogen disgust, providing support for parasite-stress theories of sexual selection and mate choice. Preferences for beards were also highest among single and married women with the strongest reproductive ambition. Overall, our results reflect mixed associations between individual differences in mating strategies and women's mate preferences for masculine facial traits

The role of accurate self-assessment in optimising mate choice.

Individuals are thought to seek the best possible romantic partner in exchange for their own desirability. We investigated whether individuals’ self-evaluations were related to their partner choices and whether the accuracy of these self-evaluations was associated with mating outcomes. Participants (N=1354) took part in a speed-dating study where they rated themselves and others on mate value and indicated their willingness to date each potential partner. Individuals were somewhat accurate in their self-evaluations, and these self-evaluations were associated with individuals’ revealed minimum and maximum standards for a potential partner, but not the number of partners they were interested in. Participants who overestimated their mate value were accepted by an equivalent number of partners compared to under-estimators, but the over-estimators were choosier and thus ended up with fewer (but similarly attractive) reciprocal matches. Results support social exchange theory and the matching hypothesis, and contrast findings that self-enhancement facilitates positive social outcomes.Output Status: Forthcomin

For the good of evolutionary psychology, let's reunite proximate and ultimate explanations

First paragraph: In Lee, Sidari, Murphy, Sherlock, and Zietsch (2020), we showed using a large speed dating study that sex differences in misperceptions of sexual interest can be explained by sociosexual orientation and, primarily, the tendency to project one's own interest onto others. We suggested that our results called into question the influential theory that the sex difference in misperception of sexual interest evolved via sex-specific specialized adaptations because it is advantageous for men, relative to women, to overperceive sexual interest (error management theory; EMT). Roth, Samara, and Kret (2020) criticise our interpretation, claiming that 1) our analyses are confounded and 2) we have confused proximate and ultimate levels of explanation. We reject both claims, but the second is an interesting and important issue that has arisen repeatedly in discussions of our paper, as well as in other contexts in the broader literature on evolution and human behavior. We spend some time discussing why proximate explanations are crucial to a healthy evolutionary psychology, and why we believe evolutionary psychologists should pay more attention to them

The role of accurate self-assessment in optimising mate choice.

Individuals are thought to seek the best possible romantic partner in exchange for their own desirability. We investigated whether individuals’ self-evaluations were related to their partner choices and whether the accuracy of these self-evaluations was associated with mating outcomes. Participants (N=1354) took part in a speed-dating study where they rated themselves and others on mate value and indicated their willingness to date each potential partner. Individuals were somewhat accurate in their self-evaluations, and these self-evaluations were associated with individuals’ revealed minimum and maximum standards for a potential partner, but not the number of partners they were interested in. Participants who overestimated their mate value were accepted by an equivalent number of partners compared to under-estimators, but the over-estimators were choosier and thus ended up with fewer (but similarly attractive) reciprocal matches. Results support social exchange theory and the matching hypothesis, and contrast findings that self-enhancement facilitates positive social outcomes

Mating strategies and the masculinity paradox: How relationship context, relationship status, and sociosexuality shape women's preferences for facial masculinity and beardedness

According to the dual mating strategy model, in short-term mating contexts women should forego paternal investment qualities in favor of mates with well-developed secondary sexual characteristics and dominant behavioral displays. We tested whether this model explains variation in women’s preferences for facial masculinity and beardedness in male faces. Computer-generated composites that had been morphed to appear +/-50% masculine were rated by 671 heterosexual women (M age = 31.72 years, SD = 6.43) for attractiveness when considering them as a short-term partner, long-term partner, a co-parent or a friend. They then completed the Revised Sociosexual Inventory (SOI-R) to determine their sexual openness on dimensions of desire, behavior, and attitudes. Results showed that women’s preferences were strongest for average facial masculinity, followed by masculinized faces, with feminized faces being least attractive. In contrast to past research, facial masculinity preferences were stronger when judging for co-parenting partners than for short-term mates. Facial masculinity preferences were also positively associated with behavioral SOI, negatively with desire, and were unrelated to global or attitudinal SOI. Women gave higher ratings for full beards than clean-shaven faces. Preferences for beards were higher for co-parenting and long-term relationships than short-term relationships, although these differences were not statistically significant. Preferences for facial hair were positively associated with global and attitudinal SOI, but were unrelated to behavioral SOI and desire. Although further replication is necessary, our findings indicate that sexual openness is associated with women’s preferences for men’s facial hair and suggest variation in the association between sociosexuality and women’s facial masculinity preferences

Multivariate Intra-Sexual Selection on Men’s Perceptions of Male Facial Morphology

Objectives Intra-sexual selection has shaped the evolution of sexually dimorphic traits in males of many primates, including humans. In men, sexual dimorphism in craniofacial shape (i.e. facial masculinity) and facial hair have both been shown to communicate aspects of social and physical dominance intra-sexually. However, less attention has been given to how variation in physical and social dominance among receivers impacts on perceptions of facial masculinity and beards as intra-sexual signals of formidability. Methods In the current study, male participants (N = 951) rated male faces varying in masculinity and beardedness when judging masculinity, dominance and aggressiveness. These participants also responded to scales measuring their psychological dominance, sexual jealousy, status seeking, and masculine morphology (facial masculinity, facial hair, and height). Results Beardedness exerted strong effects over clean-shaven faces on ratings of masculinity, dominance, and aggressiveness. Trait ratings of masculinity, dominance, and aggressiveness rose linearly with increasing craniofacial masculinity. The significant facial masculinity × facial hair interaction suggests that beardedness caused strong effects on all trait ratings over clean-shaven faces at every level of facial masculinity. Participants with full beards also reported higher scores on dominance and assertiveness scales. Participants high in dominance and assertiveness also gave higher ratings for dominance, but not masculinity or aggressiveness, to bearded over clean-shaven faces. Participants low in intra-sexual jealousy rated clean-shaven and/or feminised faces as less dominant, less masculine, and less aggressive. Conclusions These findings demonstrate that facial hair enhances perceptions of masculinity, dominance, and aggressiveness above ratings of facial masculinity, potentially by augmenting masculine craniofacial features. Individual differences in intra-sexual dominance showed associations with judgments of facial hair but not facial masculinity. Our study demonstrates that when two sexually dimorphic androgen dependent facial traits are judged in concert, ornamental rather than structural masculine facial features underpin men’s intra-sexual judgments of formidability

Testing the mate-choice hypothesis of the female orgasm: disentangling traits and behaviours

The evolution of the female orgasm in humans and its role in romantic relationships is poorly understood. Whereas the male orgasm is inherently linked to reproduction, the female orgasm is not linked to obvious reproductive or survival benefits. It also occurs less consistently during penetrative sex than does the male orgasm. Mate-choice hypotheses posit that the wide variation in female orgasm frequency reflects a discriminatory mechanism designed to select high-quality mates.We aimed to determine (1) whether women report that their orgasm frequency varies between partners, (2) whether this variation reflects mates' personal characteristics, and (3) whether this variation reflects own and partner sexual behaviour during intercourse.We collected survey data from 103 women who rated (1) the extent to which their orgasm frequency varied between partners, (2) the characteristics of previous sexual partners who induced high-orgasm frequency and those who induced low-orgasm frequency, and (3) the specific behaviours during sex with those partners. This is the first study to test within-woman variation in orgasm and partner traits.Overall, women reported variation in their orgasm rates with different partners. Partners who induced high-orgasm rates were rated as more humorous, creative, warm, faithful, and better smelling than partners who induced low-orgasm rates, and also engaged in greater efforts to induce partner orgasm.Some assumptions and predictions of mate-choice hypotheses of female orgasm were supported, while other aspects of our findings provide reasons to remain sceptical