Day-to-day coordination of the stress and reproductive axes: A continuous-time analysis of within-person testosterone and cortisol relationships in athletic and healthy men.

Day-to-day coordination of the stress (i.e., hypothalamic-pituitary-adrenal [HPA]) and reproductive (i.e., hypothalamic-pituitary-gonadal [HPG]) axes is central to allostatic regulation, reproductive success, and survival. Reports of positive, within-person testosterone and cortisol relationships (or coupling) suggest cross-talk of a facilitative nature, but longitudinal evidence is scarce and has methodological and analytical limitations. To address this, we used a continuous-time (CT) model to investigate day-to-day, within-person coupling of testosterone and cortisol in two male cohorts. Salivary testosterone and cortisol fluctuations were monitored in 35 athletic men across two international tournaments (M = 19.3 tests) and in 41 healthy men during normal daily living (M = 27.9 tests). Bayesian CT analysis revealed a diminishing effect of each hormone on itself as time-interval length or lag increased. In both groups, cortisol had a negative lagged effect on testosterone that persisted for around three days. The cortisol effect on testosterone peaked after 0.71 and 0.51 days in athletic (standardized estimate = -0.13) and healthy men (standardized estimate = -0.11), respectively. Further estimates of non-lagged, contemporaneous correlations revealed positive testosterone and cortisol relationships (athlete r = 0.04, healthy r = 0.46). In summary, complex within-person HPA and HPG interplay emerged in two independent male cohorts. Specifically, a rising cortisol concentration was linked to a fall in testosterone concentration at later time points, but concurrently these hormones tended to rise and fall together. Our results suggest that inhibitory and facilitatory hormonal actions coexist on varying timescales, thereby expanding knowledge of HPG and HPA cross-talk in everyday life.

Not within spitting distance: Salivary immunoassays of estradiol have subpar validity for predicting cycle phase.

Salivary steroid immunoassays are widely used in psychoneuroendocrinological studies of menstrual cycle phase, puberty, and menopause. Though manufacturers advertise their assays as suitable, they have not been rigorously validated for these purposes. We collated data from eight menstrual cycle studies across > 1200 female participants and > 9500 time points. Seven studies collected saliva and one collected serum. All assayed estradiol and progesterone and had an independent measure of cycle phase (LH-surge, menstrual onset). In serum, cycle phase measures strongly predicted steroid concentrations. In saliva, cycle phase poorly predicted estradiol values, which showed an upward bias compared to expectations from serum. For salivary progesterone, predictability from cycle phase was mixed, low for enzyme-linked assays and moderate for tandem mass spectrometry. Imputing the population-average serum steroid changes from cycle phase may yield more valid values of hormonal changes for an independent person than directly assessing their hormone levels using salivary immunoassays.

Hormonal Underpinnings of the Variation in Sexual Desire, Arousal and Activity Throughout the Menstrual Cycle - A Multifaceted Approach.

Although prior evidence supports women's mating behaviors and preferences being related to ovarian hormonal levels, there is conflicting evidence about exactly which hormones predict sexual function best, which specific psychosexual facets are affected and how between-individual and within-individual differences relate to this question. In this study levels of estradiol and progesterone were measured (once daily for 15 days for each participant) for 97 women, who attended two testing sessions, in times of the cycle varying in conception probability (based on the luteinizing hormone (LH) test result). Women completed surveys on their sexual desire, arousal, sexual activity frequency and initiation. There was a significant difference between peri-ovulatory and luteal values for all sexual function variables. Between-subject progesterone negatively predicted sexual activity frequency only. Within-subject estradiol positively and progesterone negatively predicted sexual desire. The findings provide support for hormonal underpinnings of sexual desire and sexual activity frequency fluctuations during the menstrual cycle. The findings did not yield support for hormonal influences on sexual arousal and initiation of sexual encounters. The main findings are consistent with the excitatory and inhibitory effects of estradiol and progesterone, respectively, on measures of women's sexual motivation.

Does scent attractiveness reveal women's ovulatory timing? Evidence from signal detection analyses and endocrine predictors of odour attractiveness.

Odour cues associated with shifts in ovarian hormones indicate ovulatory timing in females of many nonhuman species. Although prior evidence supports women's body odours smelling more attractive on days when conception is possible, that research has left ambiguous how diagnostic of ovulatory timing odour cues are, as well as whether shifts in odour attractiveness are correlated with shifts in ovarian hormones. Here, 46 women each provided six overnight scent and corresponding day saliva samples spaced five days apart, and completed luteinizing hormone tests to determine ovulatory timing. Scent samples collected near ovulation were rated more attractive, on average, relative to samples from the same women collected on other days. Importantly, however, signal detection analyses showed that rater discrimination of fertile window timing from odour attractiveness ratings was very poor. Within-women shifts in salivary oestradiol and progesterone were not significantly associated with within-women shifts in odour attractiveness. Between-women, mean oestradiol was positively associated with mean odour attractiveness. Our findings suggest that raters cannot reliably detect women's ovulatory timing from their scent attractiveness. The between-women effect of oestradiol raises the possibility that women's scents provide information about overall cycle fecundity, though further research is necessary to rigorously investigate this possibility.

Hormonal changes of intimate partner violence perpetrators in response to brief social contact with women.

This study investigated whether men with a history of real-life aggressive, dominant behavior show increases in testosterone and cortisol levels after brief social contact with women. Furthermore, we tested the prediction that such changes in hormones would be larger than those observed previously in young male students. Sixty-seven male participants convicted of intimate partner violence (IPV) either had brief social contact with a female confederate (experimental condition) or a male confederate (control condition). We also performed meta-analyses to investigate whether IPV perpetrators' hormonal responses were larger than the typical responses of young male students in prior studies. All statistical analyses were preregistered. Change in testosterone did not differ across experimental conditions, and testosterone in the IPV perpetrators actually declined from baseline in the female confederate condition. Our meta-analysis showed that this testosterone decrease was different from the testosterone increase typically observed in young male students. The cortisol levels of IPV perpetrators did not change in response to contact with women. This result was consistent with our meta-analysis since young male students also did not experience a cortisol change in response to interactions with women. In sum, our findings provide no evidence that male IPV perpetrators exhibit larger hormone increases to brief interactions with women, although it is possible that the men in this sample did not perceive the social contact period as a courtship opportunity. These results suggest that hormone reactivity to social encounters may differ across subject populations and depend on how subjects perceive social situations within laboratory settings.

Do women's faces become more attractive near ovulation?

There have been mixed findings regarding whether raters judge women's natural faces more attractive when the women were photographed near ovulation relative to when photographed in other cycle regions. Bobst and Lobmaier (2012) isolated shape cues associated with ovulatory timing via computer morphing techniques and found that men judged face shapes characteristic of the fertile window as more attractive than those characteristic of the luteal phase. Here, we tested replication of their findings but also added stimuli from the early follicular phase. We constructed three composite faces constructed from photos of the same 23 women who had each been photographed in the early follicular phase, during the fertile window, and during the luteal phase. We next warped 20 other identity faces to the shapes of the composite faces representing each cycle phase, and asked male participants to rank order the resulting face triplets for attractiveness. Men ranked fertile window and luteal phase stimuli as more attractive than early follicular stimuli, but ranked fertile window and luteal phase faces as equally attractive. This result failed to replicate preferences for fertile window over luteal phase stimuli, and thereby argues against perceivers' ability to detect face shape cues of immediate fecundity. Because estradiol was lower in the early follicular phase relative to the other two cycle phases, our findings are consistent with the possibility that within-women increases in estradiol produce subtle increases in face shape attractiveness. Discussion addresses the overall evidence for facial cues of women's ovulatory timing.

Hormonal mechanisms and the optimal use of luteinizing hormone tests in human menstrual cycle research.

Tests of whether women's psychology or behavior shifts during the fertile window vs. other cycle phase regions often employ a design in which fertile window test sessions are scheduled after a positive urinary luteinizing hormone (LH) test result. Lobmaier and Bachofner (2018) point out that this design will schedule high fecundity test sessions at the very end of the fertile window, if not later, when fecundity is not at its highest. I agree with their arguments, and here argue that the problems with this scheduling technique appear even more severe if one considers the hormonal mechanisms that are the likely regulators of cycle phase shifts. Test sessions scheduled after positive LH tests will occur at a time of rapid transitions in hormone production and will often systematically exclude periovulatory days with the highest concentrations of important hormones, such as estradiol. In doing so, this method may often fail to detect cycle phase shifts that are regulated by changes in these hormones. Hypothesis testing in cycle phase research can be improved via a transition from thinking of "fertility" as a discrete and monolithic variable, to instead thinking about the predicted effects of more continuous hormonal signals. I conclude with some general thoughts about how LH tests may be used more productively in studies of cycle phase shifts in psychology and behavior.

It is not all about mating: Attractiveness predicts partner value across multiple relationship domains.

An account of the "beauty premium" based only on mating motivations overlooks adaptationist models of social valuation that have broader explanatory power. We suggest a broader approach based on evolved preferences for attractive partners in multiple cooperative domains (not just mating), which accounts for many observations of attractiveness-based preferential treatment more comfortably than does the target article's mating-specific account.

Ovarian hormone fluctuations predict within-cycle shifts in women's food intake.

What role do ovarian hormones play in modulating day-to-day shifts in women's motivational priorities? In many nonhuman mammals, estradiol causes drops in feeding and foraging, progesterone reverses this effect, and the two hormones in combination produce cycle phase shifts characterized by lower food intake near ovulation when sexual receptivity is at its peak. Hormonal predictors of within-cycle shifts in women's total food intake have not been previously tested. Here, in a study with both daily hormone measures and self-reported food intake, we found that within-cycle fluctuations in estradiol negatively predicted shifts in food intake, progesterone fluctuations positively predicted them, and the two hormones together statistically mediated a significant peri-ovulatory drop in eating. These patterns are precisely opposite to those previously reported for sexual desire from this same sample (i.e. positive and negative effects of estradiol and progesterone, respectively, on desire). To more precisely test endocrine regulation of tradeoffs between sexual and eating motivation, a difference score for the daily standardized values of the sexual desire and food intake variables was created. Fluctuations in estradiol and progesterone were oppositely associated with shifts in this difference score, supporting hormone modulation of tradeoffs between alternative motivational priorities. These tradeoffs were especially pronounced during the fertile window of the menstrual cycle on days when conception was possible, consistent with the hormone effects functioning to shift motivational salience between feeding and mating depending on within-cycle changes in fecundity. The findings provide direct evidence that phylogenetically conserved endocrine signals regulate daily shifts in human motivational priorities.

Theoretical frameworks for human behavioral endocrinology.

How can we best discover the ultimate, evolved functions of endocrine signals within the field of human behavioral endocrinology? Two related premises will guide my proposed answer. First, hormones typically have multiple, simultaneous effects distributed throughout the brain and body, such that in an abstract sense their prototypical function is the coordination of diverse outcomes. Second, coordinated output effects are often evolved, functional responses to specific eliciting conditions that cause increases or decreases in the relevant hormones. If we accept these premises, then a natural way to study hormones is to hypothesize and test how multiple eliciting conditions are mapped into coordinated output effects via hormonal signals. I will call these input-output mappings "theoretical frameworks." As examples, partial theoretical frameworks for gonadal hormones will be proposed, focusing on the signaling roles of testosterone in men and on estradiol and progesterone in women. Recent research on oxytocin in humans will also be considered as an example in which application of the theoretical framework approach could be especially helpful in making functional sense of the diverse array of findings associated with this hormone. The theoretical framework approach is not especially common in the current literature, with many theories having eschewed explicit consideration of input-output mappings in favor of parsimony-based arguments that attempt to find the one main thing that a hormone does with respect to psychology or behavior. I will argue that these parsimony-based models have many shortcomings, and conclude that the construction and testing of theoretical frameworks provides a better means of discovering the evolved functions of human endocrine signals.

Within-cycle fluctuations in progesterone negatively predict changes in both in-pair and extra-pair desire among partnered women.

Grebe et al. (2016) argued that women's sexual interest in their own partners may be under different hormonal regulation than their sexual desire for other men. They measured partnered women's salivary hormones and reports of attraction to different categories of men at two time points separated by one week. Change in progesterone positively predicted change in women's desire for their own partners, whereas change in estradiol was a negative predictor. These results are opposite to those we previously reported for the hormonal prediction of general sexual desire in a study that employed frequent hormone sampling across multiple menstrual cycles (Roney and Simmons, 2013). Here, to test replication of the Grebe et al. findings, we assessed hormonal predictors of targeted in-pair and extra-pair desire among the subset of the sample from our 2013 paper who reported being in romantic relationships. Contrary to Grebe et al. (2016), we found that within-cycle fluctuations in progesterone were negatively correlated with changes in women's desire for both their own partners and other men. In addition, both in-pair and extra-pair desire were elevated within the fertile window and lowest during the luteal phase. Our findings contradict the idea that partner-specific desire has a unique form of hormonal regulation, and instead support a general elevation of sexual motivation associated with hormonal indices of fecundity. Discussion focuses on possible reasons for the discrepancies in findings between our study and that of Grebe et al. (2016), and on the evolved functions of women's sexual motivation.

The role of physical formidability in human social status allocation.

Why are physically formidable men willingly allocated higher social status by others in cooperative groups? Ancestrally, physically formidable males would have been differentially equipped to generate benefits for groups by providing leadership services of within-group enforcement (e.g., implementing punishment of free riders) and between-group representation (e.g., negotiating with other coalitions). Therefore, we hypothesize that adaptations for social status allocation are designed to interpret men's physical formidability as a cue to these leadership abilities, and to allocate greater status to formidable men on this basis. These hypotheses were supported in 4 empirical studies wherein young adults rated standardized photos of subjects (targets) who were described as being part of a white-collar business consultancy. In Studies 1 and 2, male targets' physical strength positively predicted ratings of their projected status within the organization, and this effect was mediated by perceptions that stronger men possessed greater leadership abilities of within-group enforcement and between-group representation. Moreover, (a) these same patterns held whether status was conceptualized as overall ascendancy, prestige-based status, or dominance-based status, and (b) strong men who were perceived as aggressively self-interested were not allocated greater status. Finally, 2 experiments established the causality of physical formidability's effects on status-related perceptions by manipulating targets' relative strength (Study 3) and height (Study 4). In interpreting our findings, we argue that adaptations for formidability-based status allocation may have facilitated the evolution of group cooperation in humans and other primates. (PsycINFO Database Record

Lady in Red: Hormonal Predictors of Women's Clothing Choices.

Recent evidence supports the idea that women use red clothing as a courtship tactic, and results from one study further suggested that women were more likely to wear red on days of high fertility in their menstrual cycles. Subsequent studies provided mixed support for the cycle-phase effect, although all such studies relied on counting methods of cycle-phase estimation and used between-subjects designs. By comparison, in the study reported here, we employed frequent hormone sampling to more accurately assess ovulatory timing and used a within-subjects design. We found that women were more likely to wear red during the fertile window than on other cycle days. Furthermore, within-subjects fluctuations in the ratio of estradiol to progesterone statistically mediated the within-subjects shifts in red-clothing choices. Our results appear to represent the first direct demonstration of specific hormone measurements predicting observable changes in women's courtship-related behaviors. We also demonstrate the advantages of hormonal determination of ovulatory timing for tests of cycle-phase shifts in psychology or behavior.

Hormonal predictors of sexual motivation in natural menstrual cycles.

Little is known regarding which hormonal signals may best predict within- and between-women variance in sexual motivation among naturally cycling women. To address this, we collected daily saliva samples across 1-2 menstrual cycles from a sample of young women; assayed samples for estradiol, progesterone, and testosterone; and also collected daily diary reports of women's sexual behavior and subjective sexual desire. With respect to within-cycle, day-to-day fluctuations in subjective desire, we found evidence for positive effects of estradiol and negative effects of progesterone. Desire exhibited a mid-cycle peak, similar to previous findings; measured progesterone concentrations statistically mediated the fall in desire from mid-cycle to the luteal phase, but no combination of hormone measures substantially mediated the follicular phase rise in desire, which suggests that other signals may be implicated in this effect. Hormonal predictors of within-cycle fluctuations in sexual behavior generally reached only trend levels of statistical significance, though the patterns again suggested positive effects of estradiol and negative effects of progesterone. Between-women and within-women, between-cycle effects of hormone concentrations were generally absent, although statistical power was more limited at these higher levels of analysis. There were no significant effects of testosterone concentrations when controlling for the effects of estradiol and progesterone, which raises questions regarding the importance of this hormone for the regulation of sexual motivation in natural cycles. Our study is among the first to identify hormonal predictors of within-cycle fluctuations in sexual motivation, and thus adds novel evidence regarding the endocrine correlates of human sexuality.

Men smelling women: null effects of exposure to ovulatory sweat on men's testosterone.

Males of many species, humans included, exhibit rapid testosterone increases after exposure to conspecific females. Female chemical stimuli are sufficient to trigger these responses in many nonhuman species, which raises the possibility of similar effects in humans. Recently, Miller and Maner (2010) reported that smelling T-shirts worn by women near ovulation can trigger testosterone responses in men; however, men were aware that they were smelling women's scents, and thus mental imagery associated with that knowledge may have contributed to the hormone responses. Here, we collected axillary sweat samples from women on days near ovulation. In a crossover design, men who were not explicitly aware of the specific stimuli smelled the sweat samples in one session and water samples in a second session. There were no differences in testosterone responses across the experimental conditions. Our null findings suggest that the relevant chemical signal is not found in axillary sweat, and/or that knowledge of the stimulus source is necessary for hormone responses. These results thus suggest boundary conditions for the effects reported in Miller and Maner (2010), and recommend further research to define the precise circumstances under which men's testosterone may respond to chemosensory cues from women.

Variation in CAG repeat length of the androgen receptor gene predicts variables associated with intrasexual competitiveness in human males.

An expanding body of research suggests that circulating androgens regulate the allocation of energy between mating and survival effort in human males, with higher androgen levels promoting greater investment in mating effort. Because variations in the number of CAG codon repeats in the human androgen receptor (AR) gene appear to modulate the phenotypic effects of androgens - with shorter repeat lengths associated with greater androgenic effects per unit androgen - polymorphisms in this gene may predict trait-like individual differences in the degree to which men are calibrated toward greater mating effort. Consistent with this, men in the present study with shorter CAG repeat lengths exhibited greater upper body strength and scored higher on self-report measures of dominance and prestige, all of which are argued to be indices of mating effort. Repeat length failed to predict sociosexual orientation (i.e. pursuit of short-term mating relationships), however, suggesting that the traits correlated with this polymorphism may be primarily associated with intrasexual competitiveness in the service of long-term mating effort. None of these measures of mating effort was related to baseline testosterone concentrations (either as main effects or as interactions with CAG repeat length), implying that long-term androgen exposure associated with AR gene polymorphisms may account for more variance in some androgen-dependent traits than does current testosterone concentration. These findings provide further evidence for the importance of the CAG repeat polymorphism in the AR gene in explaining a broad range of individual differences in human males.

The origins of extraversion: joint effects of facultative calibration and genetic polymorphism.

The origins of variation in extraversion are largely mysterious. Recent theories and some findings suggest that personality variation can be orchestrated by specific genetic polymorphisms. Few studies, however, have examined an alternative hypothesis that personality traits are facultatively calibrated to variations in other phenotypic features, and none have considered how these distinct processes may interact in personality determination. Since physical strength and physical attractiveness likely predicted the reproductive payoffs of extraverted behavioral strategies over most of human history, it was theorized that extraversion is calibrated to variation in these characteristics. Confirming these predicted patterns, strength and attractiveness together explained a surprisingly large fraction of variance in extraversion across two studies--effects that were independent of variance explained by an androgen receptor gene polymorphism. These novel findings initially support an integrative model wherein facultative calibration and specific genetic polymorphisms operate in concert to determine personality variation.

Changes in estradiol predict within-women shifts in attraction to facial cues of men's testosterone.

Many studies have demonstrated that women express stronger attraction to androgen-related traits when tested near ovulation than when tested at other times in the cycle. Much less research, however, has directly addressed which hormonal or other physiological signals may regulate these temporal shifts in women's attractiveness judgments. In the present study, we measured women's preferences for facial cues of men's testosterone concentrations on two occasions spaced two weeks apart, while also measuring women's salivary estradiol and testosterone concentrations at each testing session. Changes in women's estradiol concentrations across sessions positively predicted changes in their preferences for facial cues of high testosterone; there was no such effect for changes in women's testosterone concentrations. For the subset of women who had a testing session fall within the estimated fertile window, preferences for high testosterone faces were stronger in the fertile window session, and change in estradiol from outside to inside the fertile window positively predicted the magnitude of the ovulatory preference shift. These patterns were not replicated when testing preferences for faces that were rated as high in masculinity, suggesting that facial cues of high testosterone can be distinguished from the cues used to subjectively judge facial masculinity. Our findings suggest that women's estradiol promotes attraction to androgen-dependent cues in men (similar to its effects in females of various nonhuman species), and support a role for this hormone as a physiological regulator of cycle phase shifts in mating psychology.

Androgen receptor gene sequence and basal cortisol concentrations predict men's hormonal responses to potential mates.

Exposure to potential mates triggers rapid elevations of testosterone and glucocorticoid concentrations in males of many non-human species, and preliminary studies support similar effects in human males. The human studies have all reported large individual differences in these responses, however, and the present study tested whether specific biological variables may help explain these differences. Replicating past research, the present study found that men's salivary testosterone and cortisol concentrations increased after a brief conversation with a young woman, but did not change (or slightly decreased) after a conversation with a young man. In addition, smaller numbers of CAG repeats in men's androgen receptor gene, and lower baseline cortisol concentrations, each predicted larger testosterone responses to the interactions with women. The CAG repeat finding demonstrates that a specific genetic polymorphism predicts physiological responses to social interactions that may in turn have important downstream consequences on men's mating behaviour. The effects of cortisol are consistent with past demonstrations of glucocorticoid inhibition of testosterone production and show that such inhibition also affects testosterone responses to social stimuli. In sum, the present study both confirms men's hormonal reactions to potential mates and identifies novel biological variables that predict individual differences in these responses.