Hormonal contraceptive use lowers female intrasexual competition in pair-bonded women

Women in their mid-follicular phase outcompete hormonal contraceptive users, an effect partially explained by relatively greater progesterone and cortisol reactivity to competition

Early evidence suggests that hormonal contraceptive (HC) use alters psychological functioning and competitive behavior. Yet, there is limited data on endocrine models for explaining how HC use affects these outcomes. In this pre-registered and open-data study, we test if HC users and naturally cycling (NC) females in their low (mid-follicular) and high (mid-luteal) progesterone phase differ in competitive persistence and whether progesterone and cortisol reactivity mediate of this effect. HC users (N = 73) in the active hormone-exposure phase and NC participants in the mid-follicular (N = 69) or mid-luteal (N = 72) phase completed two behavioral measures of competitive persistence, holding up a weight for time followed by attempting to solve an unsolvable anagram. Participants also completed measures of handgrip strength and self-reported competitiveness as well as gave saliva samples before and after the tasks for hormone assay. Results showed that NC-follicular group had greater competitive persistence in the weight-holding task compared to both NC-luteal (d = 0.38) and HC use (d = 0.43) groups independent of physical strength and self-reported competitiveness covariates. Although anagram task performance showed similar trends for group differences, analyses for this task were inconclusive. Baseline progesterone did not mediate the effect of cycle phase group on competitive persistence. HC users showed relatively blunted cortisol and progesterone reactivity, and this effect partially mediated the difference in competitive persistence between HC users and the NC-follicular group. In sum, results suggest that HC use could downregulate competitive behavior at least partly by dampening cortisol-progesterone reactivity. These findings offer a new endocrine model for understanding HC use and cycle phase effects on motivational and energetic outcomes required for optimal performance in competitive contexts.

Female intrasexual competitiveness interacts with body mass index to predict willingness to use a risky diet pill

Introduction

Previous research has highlighted the putative role of intrasexual competition (IC) in predicting women's body dissatisfaction, weight loss effort, and, at its extreme, eating disorders. However, extant research reporting on these links is limited by its exclusion of potential confounds, including psychopathologies such as depression. Moreover, it is presently unclear whether women higher in body mass index (BMI) may be more prone to the influence of IC in taking dieting risks.

Methods

To address these gaps in the literature, 189 young adult women completed measures of IC, depressive symptoms, willingness to use a risky diet pill, and had their height and weight measured.

Results

Results showed that IC interacted with BMI to predict willingness to use a risky diet pill, such that women high in both IC and BMI were most likely to take the risky diet pill. Further exploratory analyses considering potential directional links between BMI and depression supported mediating roles of depression (from BMI) and BMI (from depression) in predicting willingness to use a risky diet pill.

Discussion

Results suggest that links between IC and dieting risks may be moderated by women's BMI, and that these links hold when considering depressive symptoms. Future longitudinal research would benefit from a better understanding of the potential directional links between BMI, depression, and diet pill use.

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.

Fertility predicts self-development-oriented competitiveness in naturally cycling women but not hormonal contraceptive users

Objective

A growing body of research has begun investigating the relationship between hormones and female competitiveness. Many researchers have focused on the effect of the menstrual cycle and hormonal contraceptives. Despite many attempts at understanding hormone-behavior associations, contradictory findings have made it difficult to determine the existence of true effects. The aim of the current research was to use a robust methodological design to investigate the effect of fertility probability on four competitive orientations in naturally cycling women and hormonal contraceptive users.

Methods

Using a longitudinal diary study with over 3,900 observations from 21 countries, we explore the effect of fertility probability on four self-report competitive orientations after controlling for menstruation: self-developmental competition, hyper competitiveness, competition avoidance, and lack of interest toward competition.

Results

Using Bayesian estimation for ordinal mixed models, we found that fertility probability was associated with an increase in self-development competitiveness amongst naturally cycling women but not hormonal contraceptive users. We also found weak evidence that hormonal contraceptive users show reduced interest in competing compared to naturally cycling women. There were no other robust effects of fertility or hormonal contraceptive use.

Conclusions

These results suggest that fertility probability is associated with increased fluctuations in self-development competitive motivation and that hormonal contraceptives interfere with this effect. This research contributes to the growing body of literature suggesting that hormonal contraceptives may influence psychology and behavior by disrupting evolved hormonal mechanisms.

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.

Testosterone reactivity to competition and competitive endurance in men and women

Transient shifts in testosterone occur during competition and are thought to positively influence dominance behavior aimed at enhancing social status. However, individual differences in testosterone reactivity to status contests have not been well-studied in relation to real-time expressions of competitive behavior among men and women. This research tests the association between changes in endogenous testosterone levels during competition and performance in terms of competitive endurance. Participant sex, social presence, and relative status outcomes (e.g., winning vs. losing) are tested as moderators of this relationship. In two studies, men and women (total N = 398) competed in the competitive will task (timed weight-holding) either individually or in the presence of an opponent (Study 1) or as a team with and without the presence of a competitor team (Study 2). Results showed a positive relationship between testosterone reactivity and performance for men, particularly those who won or ranked highest among their group - with increasing testosterone predicting better performance and decreasing testosterone predicting worse performance. For women, the effect only emerged among individuals who competed in dyads and lost. In Study 2, an exploratory mediation analysis revealed that individual differences in trait dominance predicted both testosterone reactivity to competition and task performance, with testosterone reactivity (moderated by sex and status outcome) partially explaining the direct relationship between dominance-related traits and behavior. Our goal was to examine testosterone reactivity in relation to real-time competitive effort and highlight the potential role of this relationship in explaining how individual differences in trait dominance produce competitive behavior.

Aggression Toward Sexualized Women Is Mediated by Decreased Perceptions of Humanness

Researchers have argued that the regulation of female sexuality is a major catalyst for women's intrasexual aggression. The present research examined whether women behave more aggressively toward a sexualized woman and whether this is explained by lower ratings of the target's humanness. Results showed that women rated another woman lower on uniquely human personality traits when she was dressed in a sexualized (vs. conventional) manner. Lower humanness ratings subsequently predicted increased aggression toward her in a behavioral measure of aggression. This effect was moderated by trait intrasexual competitiveness; lower humanness ratings translated into more aggression, but only for women scoring relatively high on intrasexual competition. Follow-up studies revealed that the effect of sexualized appearance on perceived humanness was not due to the atypicality of the clothing in a university setting. The current project reveals a novel psychological mechanism through which interacting with a sexualized woman promotes aggressive behavior toward her.

Measuring female intrasexual competition by the scale for intrasexual competition: a validation of the German version

Competitive behaviour amongst members of the same sex is termed intrasexual competition. The tendency to engage in such competition appears to be strongly related to stable individual characteristics such as personality traits. Additionally, recent studies have revealed transient fluctuations in competitiveness according to the female menstrual cycle. To date, no German questionnaire exists to measure intrasexual competition. Our first study aimed to translate and validate the Intrasexual Competition Scale (ICS) by Buunk and Fisher (J Evol Psychol 7:37-48, 2009) in a population of healthy Swiss females (n = 241). Our second study applied the validated German ICS in a group of healthy, regularly cycling females (n = 49) in order to examine possible associations between the menstrual cycle phase and ICS scores. The psychometric properties suggest that the German ICS is a reliable and valid tool to assess individual differences in female intrasexual competition. Furthermore, our second study demonstrated that on average, women showed higher intrasexual competition scores when tested in the late follicular phase (M = 35.77 ± SD = 12.03) compared to the mid-luteal phase (M = 30.93 ± SD = 10.20). Our studies support previous findings of an association between ICS scores and relatively stable individual characteristics such as personality traits. Furthermore, our research endorses the assumption of cycle-dependent fluctuations in intrasexual competition. Future research should clarify the precise mechanisms underlying these findings and include biomarkers such as oestrogen and testosterone.

The salivary testosterone response to a chance-determined contest is associated with face-gazing behaviours in athletic women

Human gaze is an important indicator of dominant and submissive behaviours related to positioning in a social hierarchy. This study investigated face gazing after a chance-determined contest and its linkage to salivary testosterone (sal-T) reactivity in athletic women. Twenty-six women athletes completed a coin-toss game on days 7 (D7), 14 (D14) and 21 (D21) of a single menstrual cycle. The game was played against an unknown opponent of similar age with the winner congratulated and rewarded with all coins. Gazing towards an opponent's head or face was timed after each contest (over 2 min) from video footage. Salivary T (sal-T) was assessed before and 15 min after these contests. The sal-T residuals increased after winning and decreased after losing on D7, D14 and D21 (p < 0.05). Gaze times were longer after a loss (M = 7.8 s) than a win (M = 3.1 s) across all days. Regression analyses revealed that the sal-T residuals and contest outcome interacted to predict gaze time. Upon deconstruction we found that, when losing a contest, a larger sal-T response (i.e., smaller decline) predicted a longer gaze (β = 1.71, p = 0.004), but no association was evident when winning (β = -0.06, p = 0.821), and these slope patterns differed (p = 0.011). In conclusion, winning a contest by chance increased sal-T responsivity and decreased opponent gaze across the menstrual cycle. A positive relationship between individual sal-T reactivity and gaze duration was observed, but only when losing. These preliminary results support suggestions that women's T may help modulate post-competition behaviours (e.g., face gazing) possibly to achieve social cohesion and cooperation.

No Evidence for Associations between men's Salivary Testosterone and Responses on the Intrasexual Competitiveness Scale

Objectives

Many previous studies have investigated relationships between men’s competitiveness and testosterone. For example, the extent of changes in men’s testosterone levels following a competitive task predicts the likelihood of them choosing to compete again. Recent work investigating whether individual differences in men’s testosterone levels predict individual differences in their competitiveness have produced mixed results.

Methods

In light of the above, we investigated whether men’s (N = 59) scores on the Intrasexual Competitiveness Scale were related to either within-subject changes or between-subject differences in men’s salivary testosterone levels.

Results

Men’s responses on the Intrasexual Competitiveness Scale did not appear to track within-subject changes in testosterone. By contrast with one recent study, men’s Intrasexual Competitiveness Scale also did not appear to be related to individual differences in testosterone.

Conclusions

Our results present no evidence for associations between men’s testosterone and their responses on the Intrasexual Competitiveness Scale.

Electronic supplementary material

The online version of this article (10.1007/s40750-018-0095-2) contains supplementary material, which is available to authorized users.

A longitudinal analysis of salivary testosterone concentrations and competitiveness in elite and non-elite women athletes

BACKGROUND

There is evidence linking women's testosterone (T) to competitive behaviours in sport and exercise. To advance this work, we examined the longitudinal relationships between salivary T (sal-T) and competitiveness in athletic women who differ in training status.

METHODS

Elite (n = 9) and non-elite (n = 21) women athletes were monitored on days 6-8 (follicular phase), 13-15 (ovulatory phase) and 20-22 (Luteal phase) of a menstrual cycle with two repeats. Salivary T levels were assessed before breakfast, followed by two questions (each rated on a 1-7 scale) on competitive desire and training motivation. Using a linear mixed model, we evaluated the menstrual phase and training status effects on each variable, before assessing the within-subject effects of sal-T on competitiveness.

RESULTS

Salivary T concentrations were higher at ovulation (effect size [ES] difference = 0.2-1.4), relative to the follicular and luteal phases, with a more marked response among elite women (p < .01). The competitiveness ratings showed similar menstrual-phase variation (ES difference = 0.6-1.0 at ovulation). A positive effect of sal-T on competitiveness emerged in both groups (p < .001), but with different slope patterns (p < .015). Specifically, the elite sal-T relationships with desire to compete (standardized β = 1.147, SE = 0.132) and training motivation (β = 1.195, SE = 0.124) were stronger compared with non-elite women (β = 0.631, SE = 0.114; β = 0.778, SE = 0.114), respectively.

CONCLUSIONS

Morning sal-T concentrations, competitive desire and training motivation all peaked around ovulation in women athletes. Notably, sal-T availability and its relationship with competitiveness was stronger among high-performing athletes. Our findings confirm menstrual fluctuations in T and competitiveness among naturally-cycling women, with population context as a moderating factor.

Interactions between observer and stimuli fertility status: Endocrine and perceptual responses to intrasexual vocal fertility cues

Both men and women find female voices more attractive at higher fertility times in the menstrual cycle, suggesting the voice is a cue to fertility and/or hormonal status. Preference for fertile females' voices provides males with an obvious reproduction advantage, however the advantage for female listeners is less clear. One possibility is that attention to the fertility status of potential rivals may enable women to enhance their own reproductive strategies through intrasexual competition. If so, the response to having high fertility voices should include hormonal changes that promote competitive behavior. Furthermore, attention and response to such cues should vary as a function of the observer's own fertility, which influences her ability to compete for mates. The current study monitored variation in cortisol and testosterone levels in response to evaluating the attractiveness of voices of other women. All 33 participants completed this task once during ovulation then again during the luteal phase. The voice stimuli were recorded from naturally cycling women at both high and low fertility, and from women using hormonal birth control. We found that listeners rated high fertility voices as more attractive compared to low fertility, with the effect being stronger when listeners were ovulating. Testosterone was elevated following voice ratings suggesting threat detection or the anticipation of competition, but no stress response was found.

A longitudinal analysis of women's salivary testosterone and intrasexual competitiveness

Research on within-subject changes in women's intrasexual competitiveness has generally focused on possible relationships between women's intrasexual competitiveness and estimates of their fertility. While this approach is useful for testing hypotheses about the adaptive function of changes in women's intrasexual competitiveness, it offers little insight into the proximate mechanisms through which such changes might occur. To investigate this issue, we carried out a longitudinal study of the hormonal correlates of changes in intrasexual competitiveness in a large sample of heterosexual women (N=136). Each woman provided saliva samples and completed an intrasexual competitiveness questionnaire in five weekly test sessions. Multilevel modeling of these data revealed a significant, positive within-subject effect of testosterone on intrasexual competitiveness, indicating that women reported greater intrasexual competitiveness when testosterone was high. By contrast, there were no significant effects of estradiol, progesterone, estradiol-to-progesterone ratio, or cortisol and no significant effects of any hormones on reported relationship jealousy. This is the first study to demonstrate correlated changes in measured testosterone levels and women's reported intrasexual competitiveness, implicating testosterone in the regulation of women's intrasexual competitiveness.

Hormonal contraceptives suppress oxytocin-induced brain reward responses to the partner's face

The hypothalamic peptide oxytocin (OXT) has been identified as a key modulator of pair-bonding in men, but its effects in women are still elusive. Moreover, there is substantial evidence that hormonal contraception (HC) influences partner preferences and sexual satisfaction, which constitute core domains of OXT function. We thus hypothesized that OXT effects on partner-related behavioral and neural responses could be significantly altered in women using HC. In this functional magnetic resonance imaging study involving 40 pair-bonded women, 21 of whom were using HC, we investigated whether a 24-IU nasal dose of OXT would modulate brain reward responses evoked by the romantic partner's face relative to the faces of familiar and unfamiliar people. Treatment with OXT increased the perceived attractiveness of the partner relative to other men, which was paralleled by elevated responses in reward-associated regions, including the nucleus accumbens. These effects of OXT were absent in women using HC. Our results confirm and extend previous findings in men that OXT interacts with the brain reward system to reinforce partner value representations, indicating a common OXT-dependent mechanism underlying partner attraction in both sexes. This mechanism may be disturbed in women using HC, suggesting that gonadal steroids could alter partner-specific OXT effects.

Parental Social Status and Intrasexual Competitiveness among Adolescents

A study among 1,881 adolescents (52.3% girls) with a mean age of 19.1 years examined the effects of parental social status upon intrasexual competitiveness. Whereas females were consistently more intrasexually competitive the higher the socio-economic status of their parents, males with parents of the lowest socio-economic status tended to be more intrasexually competitive than those with parents of medium socio-economic status, and nearly as intrasexually competitive as those with parents of high socio-economic status. Only among adolescents with parents of low socio-economic status were males more intrasexually competitive than females. Among males and females, higher levels of intrasexual competitiveness were related to a higher family income, to a higher occupational status of the father as well as of the mother, and to a higher educational level of the mother. Only among females were higher levels of intrasexual competitiveness associated with a higher educational level of the father. Males whose fathers had only elementary education had a relatively high level of intrasexual competitiveness. The results are discussed in the context of the multifaceted nature of human status, and the potential relevance of intrasexual competitiveness for individuals of high versus low social status.

Psychobehavioral Effects of Hormonal Contraceptive Use

Although female use of hormonal contraceptives (HCs) has been associated with a variety of physical side effects, the psychological and behavioral side effects have received comparatively little attention until recently. Indeed, the long-term impact of HC use on human psychology has been vastly under-researched and has only recently become a focus for mainstream scholars. Women who use HCs report higher rates of depression, reduced sexual functioning, and higher interest in short-term sexual relationships compared to their naturally-cycling counterparts. Also, HC use may alter women's ability to attract a mate, as well as the mate retention behaviors in both users and their romantic partners. Some evidence even suggests that HC use alters mate choice and may negatively affect sexual satisfaction in parous women, with potential effects on future offspring. Interestingly, HCs have become a standard method of population control for captive nonhuman primates, opening up exciting avenues for potential comparative research. Here, the existing literature on the psychobehavioral effects of HCs in humans and nonhuman primates is reviewed and discussed. The potential resulting downstream consequences for the path of human evolution and recommendations for how future research could tease apart the underlying causes of these psychobehavioral effects of HC use are discussed, including suggestions for research involving nonhuman primates.