An agent-based model of the female rivalry hypothesis for concealed ovulation in humans

Agent-based models of the cultural evolution of occupational gender roles

The causes of sex differences in human behaviour are contested, with 'evolutionary' and 'social' explanations often being pitted against each other in the literature. Recent work showing positive correlations between indices of gender equality and the size of sex differences in behaviour has been argued to show support for 'evolutionary' over 'social' approaches. This argument, however, neglects the potential for social learning to generate arbitrary gender segregation. In the current paper we simulate, using agent-based models, a population where agents exist as one of two 'types' and can use social information about which types of agents are performing which 'roles' within their environment. We find that agents self-segregate into different roles even where real differences in performance do not exist, if there is a common belief (modelled as priors) that group differences may exist in 'innate' competence. Facilitating role changes such that agents should move without cost to the predicted highest-rewards for their skills (i.e. fluidity of the labour market) reduced segregation, while forcing extended exploration of different roles eradicated gender segregation. These models are interpreted in terms of bio-cultural evolution, and the impact of social learning on the expression of gender roles.

Women’s Intrasexual Competitiveness and Jealousy Across the Ovulatory Cycle: A Hormone-Based Study

Research on social status competition among women suggests that underlying hormonal shifts associated with the ovulatory cycle systematically drive alterations in preferences and behavior. Specifically, it is proposed that the fertile window, marked by heightened estradiol and lower progesterone levels, is related to increased psychological motivation for intrasexual social comparison, leading to increasing competitiveness and jealousy. In this pre-registered, longitudinal study, 257 women provided saliva samples for hormone assays, rated the attractiveness of other women, and self-reported intrasexual competitiveness and jealousy across four testing sessions. Multilevel analyses revealed no compelling evidence for (hormone-related) cycle shifts in intrasexual competitiveness, attractiveness ratings, or jealousy. Rather, women higher in intrasexual competitiveness seem to rate other women as more attractive in general. We discuss how our results contribute to a growing body of literature suggesting that women’s social attitudes and preferences are more stable and less hormonally influenced than previously assumed.

Men are not aware of and do not respond to their female partner's fertility status: Evidence from a dyadic diary study of 384 couples

Understanding how human mating psychology is affected by changes in female cyclic fertility is informative for comprehending the evolution of human reproductive behavior. Based on differential selection pressures between the sexes, men are assumed to have evolved adaptations to notice women's within-cycle cues to fertility and show corresponding mate retention tactics to secure access to their female partners when fertile. However, previous studies suffered from methodological shortcomings and yielded inconsistent results. In a large, preregistered online dyadic diary study (384 heterosexual couples), we found no compelling evidence that men notice women's fertility status (as potentially reflected in women's attractiveness, sexual desire, or wish for contact with others) or display mid-cycle increases in mate retention tactics (jealousy, attention, wish for contact or sexual desire towards female partners). These results extend our current understanding of the evolution of women's concealed ovulation and oestrus, and suggest that both might have evolved independently.

Hormonal contraceptives as disruptors of competitive behavior: Theoretical framing and review

Emerging evidence suggests that hormonal contraceptives (HCs) impact psychological outcomes through alterations in neurophysiology. In this review, we first introduce a theoretical framework for HCs as disruptors of steroid hormone modulation of socially competitive attitudes and behaviors. Then, we comprehensively examine prior research comparing HC users and non-users in outcomes related to competition for reproductive, social, and financial resources. Synthesis of 46 studies (n = 16,290) led to several key conclusions: HC users do not show the same menstrual cycle-related fluctuations in self-perceived attractiveness and some intrasexual competition seen in naturally-cycling women and, further, may show relatively reduced status- or achievement-oriented competitive motivation. However, there a lack of consistent or compelling evidence that HC users and non-users differ in competitive behavior or attitudes for mates or financial resources. These conclusions are tentative given the notable methodological limitations of the studies reviewed. Implications and recommendations for future research are discussed.

Women's Estrus and Extended Sexuality: Reflections on Empirical Patterns and Fundamental Theoretical Issues

How do women's sexual interests change across their ovulatory cycles? This question is one of the most enduring within the human evolutionary behavioral sciences. Yet definitive, agreed-upon answers remain elusive. One empirical pattern appears to be robust: Women experience greater levels of sexual desire and interest when conceptive during their cycles. But this pattern is not straightforward or self-explanatory. We lay out multiple possible, broad explanations for it. Based on selectionist reasoning, we argue that the conditions that give rise to sexual interests during conceptive and non-conceptive phases are likely to differ. Because conceptive and non-conceptive sex have distinct functions, the sexual interests during conceptive and non-conceptive phases are likely to have different strategic ends. We discuss provisional evidence consistent with this perspective. But the exact nature of women's dual sexuality, if it exists, remains unclear. Additional empirical research is needed. But perhaps more crucially, this topic demands additional theory that fruitfully guides and interprets future empirical research.