Testosterone and Fathers’ Parenting Unraveled: Links with the Quantity and Quality of Father-Child Interactions Abstract Objective Individual differences in quality of father involvement in caregiving might in part be explained by fathers’ testosterone (T) levels. We examined the links between fathers’ (n = 32) salivary T levels, amount of time spent with their child (12–30 months of age), type of father-child interaction, and fathers’ sensitivity. Methods During two home visits, video observations of father-child interactions were conducted to measure fathers’ sensitivity during a challenging and harmonious interaction. Fathers’ saliva was collected several times throughout the day on a working day and on the home visit days, including right before and after each father-child interaction. Results Fathers’ T secretion throughout the day was lower on home visit days (i.e., days with a higher amount of time spent with their child) than on a working day. For both challenging and harmonious father-child interactions, mean T levels did not differ before and after father-child interactions. However, individual changes in fathers’ T levels during the father-child interactions did predict fathers’ sensitivity. Specifically, the more T increased during the challenging interaction, or decreased during the harmonious interaction, the more sensitive the father was during that interaction as well as during a subsequent interaction. Conclusions Parenting quality is most optimal when fathers’ T system reacts in the expected direction given the context of the father-child interaction, i.e., a T decrease during a harmonious interaction and a T increase during a challenging interaction. Our study underscores the importance of examining the interplay between biology, behavior, and caregiving context in fathers’ parenting.

A Comparison of men’s Life History, Aging, and Testosterone Levels among Datoga Pastoralists, Hadza Foragers, and Qom Transitional Foragers Abstract Objectives Relative to industrialized populations, men from subsistence groups exhibit lower testosterone values and more modest declines with age. Limited energy availability has been hypothesized to suppress testosterone production, particularly during young adulthood when testosterone levels are highest, resulting in a flatter trajectory of age-decline. Energetic constraint, however, is not unique to the evolutionary ecology of humans, and yet significant age-related testosterone decline is observed in numerous species of wild primates. Conversely, human life history is distinguished by extensive bi-parental care and male provisioning. Because fathers show decreased testosterone with parenting effort, we argue that within more naturalistic and evolutionarily relevant ecologies, natural fertility and earlier reproduction suppresses testosterone in emerging adulthood such that a lower relative baseline dictates less age-decline across the remaining lifespan. Methods We examine men’s testosterone levels as contrasting functions of energetic status and paternal involvement across three traditional populations with substantial variability in men’s nutritional condition and parental investment. Anthropometric and demographic data along with saliva samples were collected from 70 Datoga, 29 Hadza, and 43 Qom men, ages 20–72 years. Results Population variation in salivary testosterone was greatest at younger ages and patterned so paternal involvement associated with lower morning and evening testosterone, along with diminished age-decline in both measures. Men’s energetic status as indicated by body mass index was not associated with testosterone values or age-related decline. Conclusions Within socioecological contexts of smaller scale society, these data suggest that blunted age-decline in men’s testosterone levels is primarily due to population variation in parental investment rather than energetic constraint.

I Don’t Sweat my Future: Future-Selves, Personality, and Skin Conductance Abstract Objective Future-selves (both positive and negative) have been shown to be related to self-esteem, efficacy, meaning, continuity, and social acceptance. Control beliefs (beliefs about whether actions can bring about desired outcomes) as well as locus of control (internal or external) may impact how individuals see their future and their perception of what can be done to create or change the future. Machiavellian personality traits are associated with external locus of control, while conscientiousness is associated with internal locus of control. Methods We measured galvanic skin response (GSR), a widely used measure of physiological arousal, in 84 study participants while they described possible future selves, one positive and one negative, and completed questionnaires about personality traits. Results Higher conscientiousness was associated with lower skin conductance when describing positive future selves, whereas higher scores on the Machiavellian Personality Assessment questionnaire were correlated with lower skin conductance when describing negative future selves. Conclusion Conscientious individuals are confident in their ability to control their future, thus explaining their lower arousal when describing positive future selves. Machiavellian individuals view the world more negatively but believe they can handle negative situations, thus explaining their lower arousal when describing negative future selves.

Why Be Generous? Tests of the Partner Choice and Threat Premium Models of Resource Division Abstract Objective The ability to divide resources is crucial for a social and cooperative species like humans, but how humans divide resources remains unclear. Recent results using economic games have suggested conflicting models: The ‘partner choice’ perspective argues that generosity is (in part) a bid for an ongoing cooperative relationship, so generosity is expected to be elicited by cues of cooperative partner value. The ‘threat premium’ perspective argues that generosity is (in part) an attempt to avoid violent retaliation, so generosity is expected to be elicited by cues of threat potential. Methods We tested these competing hypotheses using a dyad study in which pairs of undergraduate participants (N = 312) had a half-hour face-to-face conversation, evaluated each other on components of cooperative partner value and physical dominance, and completed 4 economic tasks comprising 7 resource division decisions. Results Generosity was uniquely predicted by cues of the ability to produce material benefits in an ancestral environment, this effect was stronger for men, and generosity tracked other measures of social attraction. In contrast, the partner’s physical dominance did not predict generosity. Conclusions We observed support for the partner choice approach to resource divisions. Implications for the study of social preferences and resource divisions are discussed.

Testosterone and Cortisol Interact to Predict Within-Team Social Status Hierarchy among Olympic-Level Women Athletes Abstract Objectives The dual-hormone hypothesis posits that social status is positively related to testosterone levels when cortisol levels are relatively low and negatively related to testosterone levels when cortisol is high. In the present study, we test this hypothesis with Olympic-level women athletes using a novel status-hierarchy generation task that establishes rank-order among teammates along three dimensions: leadership ability, popularity, and skill. Methods Participants completed the hierarchy generation task and then, testosterone and cortisol levels were obtained from samples provided on a neutral-day baseline and immediately prior to competing in an international match. Results The interaction between cortisol and testosterone predicted social status among teammates for both baseline and pre-match samples. Specifically, there was a negative association between testosterone and status for those who were relatively high in cortisol. Conclusions These results provide support for the dual-hormone hypothesis using a new, ecologically valid method for determining rank-order among members of a social group, in a special population of women athletes competing at the highest level of their sport.

Quantity-Quality Trade-Offs May Partially Explain Inter-Individual Variation in Psychopathy Abstract Objective The examination of ultimate factors that maintain genetic (and consequently phenotypic) variance in a behavioral trait represents one of the key goals of evolutionary ecology of personality. One of these factors are adaptive trade-offs: if a trait is involved in a trade-off, than natural selection cannot deplete its genetic variance. We used this theoretical framework to examine psychopathy, a behavioral syndrome consisting of deceitful behavior, emotional coldness and recklessness. Relying on previous research, we assumed that psychopathy elevates fertility but diminishes offspring quality, thus contributing to quantity-quality trade-off. Method The research sample was consisted of 635 individuals with at least one child, who were at the end of their reproductive phase. We examined psychopathy traits of these individuals, together with parental investment via their offspring ratings. Furthermore, we collected the measures of offspring Covitality (combined physical and mental health) and Residual reproductive value (expected future fitness in offspring) as the measures of offspring quality. We used parental reproductive success as an indicator of offspring quantity. Results Research results confirmed the hypotheses. Psychopathic traits had small positive relations with the number of children and negative associations with parental investment, Covitality and residual reproductive value in offspring. Mediation model that depicted parental investment as the mediator of the psychopathy-offspring quality link had a good fit to the data. Conclusions Research findings have high heuristic potential because they provide an insight in how natural selection can preserve variation in psychopathy.

Further Evidence that Facial Width-to-Height Ratio and Global Facial Masculinity Are Not Positively Associated with Testosterone Levels Abstract Objectives Facial masculinity, as for example measured by the facial width-to-height ratio (fWHR) or the global facial masculinity index, has been associated with a vast range of behavioural traits, including dominance and aggression. Further, facial masculinity is thought to be influenced by testosterone (T) levels as an underlying mechanism. However, a recent meta-analysis on fWHR and T levels provided non-significant associations in men, which we wanted to examine further in men and additionally in women. Methods We examined whether fWHR and global facial masculinity are positively associated with salivary baseline T and T reactivity in 140 men (age 18–34 years), as well as with salivary baseline T and hair T concentrations in 151 women (age 18–35 years). Results No associations of salivary baseline T, T reactivity or hair T levels with fWHR or global facial masculinity were observed. Additional analyses revealed sex differences in sexual dimorphism in fWHR and global facial masculinity: men had generally higher global facial masculinity compared to women, but unexpectedly a lower fWHR. Conclusions Overall, our results provide further evidence that neither fWHR nor global facial masculinity are related to T levels and question earlier findings on male-biased sexual dimorphism in fWHR.

Sexual Attractiveness: a Comparative Approach to Morphological, Behavioral and Neurophysiological Aspects of Sexual Signaling in Women and Nonhuman Primate Females Abstract Objective and Methods This review focuses on comparative data in nonhuman primates and humans in relation to signaling secondary sex characteristics (SSC), sexual behavior, and neurophysiology of sexuality during the female cycle. Results In monkeys and apes no clear distinction can be drawn between sex as a reproductive, social, or a pleasurable activity. Although female sexual behavior is not limited to a specific phase of the menstrual cycle, changes in body morphology and in behavior and psychology (for example, in feeding, risk taking, and mood) can occur across the cycle. In human and nonhuman primates, homologous biological mechanisms including specific areas of the brain, sex steroids, and receptors are involved in regulating female sexuality. Important aspects of this regulation include the interaction between the subcortical reward system and the social brain network and its projection to the prefrontal cortex. In humans, females advertise SSC permanently after the onset of puberty, but without significant changes across the cycle, whereas in other primate species, female sexual signaling can vary significantly across cycle stages and in fertile and non-fertile phases of the life cycle. Conclusion A great deal is now known about the regulation of female sexuality in primates and the use of sexual signals in terms of their variable expression and their information content for males. Human research has also elucidated the cultural mechanisms through which women communicate about their sexuality, including clothes and make-up. A full understanding of female sexuality in humans, therefore, requires knowledge of culture-biology interactions.

Endocrine Correlates of Social Comparison in Couple Relationships Abstract Objectives This study employed an experimental design that induced social comparison in couples by systematically varying performance feedback in a manipulated pretend IQ test. Methods Sixty-two heterosexual couples were randomly assigned to four experimental groups, in which either the man (1) or the woman (2) was provided with superior feedback and compared to couples which received equal feedback (3) or no feedback (4). The biopsychological responses were assessed using repeated measures of mood, levels of the gonadal hormones testosterone (T) and estradiol (E2), and the stress hormone cortisol (C) in both partners. Results Compared to the men, the entire female sample responded to the test with a decrease in T. Women who received superior feedback showed a unique endocrine profile, characterized by an immediate increase in E2 and a delayed decrease in T. In contrast to men, women’s mood decreased in all conditions except for the superior feedback. Conclusions Our results indicate that women may be physiologically and subjectively more strongly affected by comparison processes with their partners in the dimension of skills and achievement. Moreover, our findings are the first to show that in romantic relationships, the endocrine correlates of social comparison may include an intriguing interplay between the steroid hormones T and E2, but not C.

Cross-Cultural Variation in women’s Preferences for men’s Body Hair Abstract Objectives According to the ectoparasite avoidance hypothesis, natural selection has shaped human hairlessness to reduce the potential for the body to host disease carrying ectoparasites. However, men retain sexually dimorphic and conspicuous patches of facial and body hair. The ectoparasite avoidance hypothesis also proposes that sexual selection via women’s mate preferences for reduced hirsutism has further elaborated upon the reduction in body hair and could explain variation in women’s preferences for body hair in men. The current study tests this hypothesis using cross-cultural data from 30 countries on women’s preferences for chest hair. Methods We test whether heterosexual women’s (N = 3436) preferences for reduced hirsutism are most pronounced in countries with higher disease and parasite levels or whether other social and economic factors previously shown to influence preferences for facial masculinity and beardedness predict women’s preferences for chest hair. Results We found that preferences were unrelated to past or current disease rates. Instead, preferences for body hair were stronger among women who were older, had strong preferences for facial hair, and were from countries that had male-biased sex ratios, higher human development indices, and lower education indices. Women’s body hair preferences were also associated with facial masculinity preferences and gender empowerment. However, neither these terms, nor human development indices or education indices were individually significant in their contributions to the family of best-fit models and we suggest caution when interpreting their significance. Conclusions Women’s preferences for body hair may be strongest among women from countries where male-male competition is higher and preferences for beardedness are stronger rather than where prevailing ecological conditions my impact on maternal and offspring survival.