Can listeners assess men's self-reported health from their voice?

Men's voices may provide cues to overall condition; however, little research has assessed whether health status is reliably associated with perceivable voice parameters. In Study 1, we investigated whether listeners could classify voices belonging to men with either relatively lower or higher self-reported health. Participants rated voices for speaker health, disease likelihood, illness frequency, and symptom severity, as well as attractiveness (women only) and dominance (men only). Listeners' were mostly unable to judge the health of male speakers from their voices; however, men rated the voices of men with better self-reported health as sounding more dominant. In Study 2, we tested whether men's vocal parameters (fundamental frequency mean and variation, apparent vocal tract length, and harmonics-to-noise ratio) and aspects of their self-reported health predicted listeners' health and disease resistance ratings of those voices. Speakers' fundamental frequency (f_o) negatively predicted ratings of health. However, speakers' self-reported health did not predict ratings of health made by listeners. In Study 3, we investigated whether separately manipulating two sexually dimorphic vocal parameters—f_o and apparent vocal tract length (VTL)—affected listeners' health ratings. Listeners rated men's voices with lower f_o (but not VTL) as healthier, supporting findings from Study 2. Women rated voices with lower f_o and VTL as more attractive, and men rated them as more dominant. Thus, while both VTL and f_o affect dominance and attractiveness judgments, only f_o appears to affect health judgments. Results of the above studies suggest that, although listeners assign higher health ratings to speakers with more masculine f_o, these ratings may not be accurate at tracking speakers' self-rated health.     

Quantifying the strength and form of sexual selection on men's traits

Although recent research has increasingly focused on human sexual selection, fundamental questions remain concerning the relative influence of individual traits on success in competition for mates and the mechanisms, form, and direction of these sexual selective pressures. Here, we explore sexual selection on men's traits by ascertaining men's dominance and attractiveness from male and female acquaintances. On a large American university campus, 63 men from two social fraternities provided anthropometric measurements, facial photographs, voice recordings, and reported mating success (number of sexual partners). These men also assessed each other's dominance, and 72 women from two socially affiliated sororities assessed the men's attractiveness. We measured facial masculinity from inter-landmark distances and vocal masculinity from acoustic parameters. We additionally obtained facial and vocal attractiveness and dominance ratings from unfamiliar observers. Results indicate that dominance and the traits associated with it predict men's mating success, but attractiveness and the traits associated with it do not. These findings point to the salience of contest competition on men's mating success in this population.     

A sex difference in the context-sensitivity of dominance perceptions

Although dominance perceptions are thought to be important for effective social interaction, their primary function is unclear. One possibility is that they simply function to identify individuals who are capable of inflicting substantial physical harm, so that the perceiver can respond to them in ways that maximize their own physical safety. Another possibility is that they are more specialized, functioning primarily to facilitate effective direct (i.e., violent) intrasexual competition for mates, particularly among men. Here we used a priming paradigm to investigate these two possibilities. Facial cues of dominance were more salient to women after they had been primed with images of angry men, a manipulation known to activate particularly strong self-protection motivations, than after they had been primed with images of angry women or smiling individuals of either sex. By contrast, dominance cues were more salient to men after they had been primed with images of women than when they had been primed with images of men (regardless of the emotional expressions displayed), a manipulation previously shown to alter men's impressions of the sex ratio of the local population. Thus, men's dominance perceptions appear to be specialized for effective direct competition for mates, while women's dominance perceptions may function to maximize their physical safety more generally. Together, our results suggest that men's and women's dominance perceptions show different patterns of context-sensitivity and, potentially, shed new light on the routes through which violence and intrasexual competition have shaped dominance perceptions.     

Mating context and menstrual phase affect women's preferences for male voice pitch

Fundamental frequency (F₀) is the vocal acoustic parameter closest to what we perceive as pitch. Men speak at a lower F₀ than do women, even controlling for body size. Although the developmental and anatomical reasons for this sex difference are known, the evolutionary reasons are not. By examining fertility-related variation in women's preferences for men's voices, the present study tests the hypothesis that female choice for good genes influenced the evolution of male voice pitch (VP). Unlike previous correlational studies that did not consider the effects of menstrual phase and mating context on women's preferences for male VP, the present study includes these variables and utilizes experimental pitch (P) manipulations. Results indicate that low VP is preferred mainly in short-term mating contexts rather than in long-term, committed ones, and this mating context effect is greatest when women are in the fertile phase of their ovulatory cycles. Moreover, lower male F₀ correlated with higher self-reported mating success. These findings are consistent with the hypothesis that an association between low male VP and heritable fitness led to the evolution of the observed patterns in women's P preferences and men's mating success and that these patterns influenced the evolution of low VP in men. However, alternative explanations are considered.     

How multiple mating by females affects sexual selection

Multiple mating by females is widely thought to encourage post-mating sexual selection and enhance female fitness. We show that whether polyandrous mating has these effects depends on two conditions. Condition 1 is the pattern of sperm utilization by females; specifically, whether, among females, male mating number, m (i.e. the number of times a male mates with one or more females) covaries with male offspring number, o. Polyandrous mating enhances sexual selection only when males who are successful at multiple mating also sire most or all of each of their mates'' offspring, i.e. only when Cov_♂(m,o), is positive. Condition 2 is the pattern of female reproductive life-history; specifically, whether female mating number, m, covaries with female offspring number, o. Only semelparity does not erode sexual selection, whereas iteroparity (i.e. when Cov_♀(m,o), is positive) always increases the variance in offspring numbers among females, which always decreases the intensity of sexual selection on males. To document the covariance between mating number and offspring number for each sex, it is necessary to assign progeny to all parents, as well as identify mating and non-mating individuals. To document significant fitness gains by females through iteroparity, it is necessary to determine the relative magnitudes of male as well as female contributions to the total variance in relative fitness. We show how such data can be collected, how often they are collected, and we explain the circumstances in which selection favouring multiple mating by females can be strong or weak.     

Evidence of adaptation for mate choice within women's memory

Sexually dimorphic characteristics in men may act as cues, advertising long-term health, dominance, and reproductive potential to prospective mates. Evolution has accordingly adapted human cognition so that women perceive sexually dimorphic facial features as important when judging the attractiveness and suitability of potential mates. Here we provide evidence showing, for the first time, that women's memory for details encountered in recently experienced episodes is also systematically biased by the presence of men's facial cues signaling enhanced or reduced sexual dimorphism. Importantly, the direction and strength of this bias are predicted by individual differences in women's preferences for masculine versus feminine facial features in men and are triggered specifically while viewing images of male but not female faces. No analogous effects were observed in male participants viewing images of feminized and masculinized women's faces despite the fact that male participants showed strong preferences for feminized facial features. These findings reveal a preference-dependent memory enhancement in women that would promote retention of information from encounters with preferred potential mates. We propose that women's memory for recently experienced episodes may therefore be functionally specialized for mate choice and in particular for the comparative evaluation of alternative potential mates. This also raises the possibility that similar specialization may be present in other species where it has been established that precursor, ‘episodic-like’ forms of memory exist.     

The evolved psychology of voice: evaluating interrelationships in listeners' assessments of the size,masculinity, and attractiveness of unseen speakers

A growing body of research has examined how voice characteristics advertise personal dimensions relevant in mate competition and mate choice. This work has centered on two key voice features, namely, fundamental frequency (F₀) and formants (Fn), and has consistently found that speakers with low F₀, low Fn, or both are rated as being larger, more masculine, and more attractive if men but less attractive if women. However, this consistency in listeners' perceptions is not matched by an equivalent consensus in how these mate-relevant dimensions are causally related or signaled by voice characteristics. Consequently, it is critical to test whether the strong correlations in listeners' perceptions reflect reliable causal relationships between these dimensions or, alternatively, whether they reflect some perceptual or cognitive nonindependence, for example, “what is large is masculine” and “what is small is feminine.” To test this latter possibility, we report detailed analyses of interdependence in listeners' ratings of perceived size, masculinity or femininity, and attractiveness of natural and manipulated voices of the opposite sex. We found strong correlations in listeners' ratings of all three dimensions, confirming past research. Principal component analysis corroborated these interrelationships but also revealed some independence in women's ratings of men's attractiveness and additional (but weaker) independence in men's ratings of women's size. We discuss possible implications for future research on the evolved psychology of voice and whether and how it reflects adaptive functional heuristics for discriminating mates.     

Sex difference in travel is concentrated in adolescence and tracks reproductive interests

Sexual selection theory suggests that the sex with a higher potential reproductive rate will compete more strongly for access to mates. Stronger intra-sexual competition for mates may explain why males travel more extensively than females in many terrestrial vertebrates. A male-bias in lifetime distance travelled is a purported human universal, although this claim is based primarily on anecdotes. Following sexual maturity, motivation to travel outside the natal territory may vary over the life course for both sexes. Here, we test whether travel behaviour among Tsimane forager–horticulturalists is associated with shifting reproductive priorities across the lifespan. Using structured interviews, we find that sex differences in travel peak during adolescence when men and women are most intensively searching for mates. Among married adults, we find that greater offspring dependency load is associated with reduced travel among women, but not men. Married men are more likely to travel alone than women, but only to the nearest market town and not to other Tsimane villages. We conclude that men''s and women''s travel behaviour reflects differential gains from mate search and parenting across the life course.     

Women’s sexual strategies in pregnancy

Humans exhibit an unusual pattern of sexual behavior compared to other mammalian females. Women's extended sexuality has been hypothesized to be related to a variety of possible benefits, especially non-genetic reproductive benefits, such as securing male investment via reinforced pairbonds or paternity confusion. But sexual behavior also comes at a cost, particularly for pregnant women, in terms of energetic costs, potential disease, and possible harm to the fetus. We hypothesize, therefore, that sexual behavior in pregnant women should reflect adaptive strategies and that pregnant women will be particularly strategic about their sexual behavior in order to maximize potential benefits while minimizing potential costs. One hundred twelve pregnant women completed a survey of their partners' qualities and their sexual desires toward their primary partners and men other than their primary partners. Results showed that women's perceptions of relationship threat positively predicted sexual desire for primary partners, while their perceptions of their partner's investing qualities negatively predicted sexual desire for extra-pair mates. These qualities, as well as cues to partner's genetic quality and gestation age, also interacted in ways that suggest that pregnant women's sexual desires are sensitive to cues of future investment and relationship stability.     

Fitness consequences of divorce in the azure-winged magpie depends on the breeding experience of a new mate

Sexual conflict in producing and raising offspring is a critical issue in evolutionary ecology research.Individual experience affects their breeding performance,as measured by such traits of provisioning of offspring and engagement in extra-pair copulations,and may cause an imbalance in sexual conflict.Thus,divorce is hypothesized to occur within aged social pairs,irrespective of current reproductive success.This concept was explored in the azure-winged magpie Cyanopica cyanus by investigating the divorce of a social pair and its relationship to their changes in breeding performance with prior experience.Females engaging in extra-pair copulation may intensify sexual conflicts and may be the main reason for divorce.Once divorced,females repairing with an inexperienced male realized higher reproductive success than that repairing with an experienced male;males repairing with an experienced female realized higher reproductive success than that repairing with an inexperienced female.This finding indicates that the fitness consequence of divorce depends on the breeding experience of new mates.Divorced females can obtain more extra-pair copulations,whereas divorced males cannot,when they repair with inexperienced breeders.Divorced females provisioned a brood at lower rates than inexperienced females whereas divorced males had no such difference.It appears that divorced females can obtain an advantage in sexual conflicts with inexperienced mates in future reproduction.Consequently,females are probably more active than males in divorcing their aged mates so as to select an inexperienced male as a new mate.Azure-winged magpies thus provide novel insights into the implicaticns of sexual conflict in birds.     

Infidelity,jealousy, and wife abuse among Tsimane forager–farmers: testing evolutionary hypotheses of marital conflict

The role of men's jealousy over a wife's infidelity in precipitating marital conflict and wife abuse is well documented. The role of women's jealousy over a husband's infidelity has received little attention, which is puzzling given high potential costs to women of withdrawal of paternal investment. We address this gap by investigating marital conflict and wife abuse among Tsimane forager–farmers of Bolivia. We test predictions derived from male jealousy and paternal disinvestment hypotheses, which consider threats and consequences of infidelity by women (male jealousy hypothesis) and men (paternal disinvestment hypothesis). The paternal disinvestment hypothesis proposes that wife abuse is employed by husbands to limit wives' mate retention effort and maintain men's opportunities to pursue extrapair sexual relationships. Interviews were conducted among husbands and wives in the same marriages using a combination of open-ended and structured items. Spouses agree that the most frequently reported type of marital argument is women's jealousy over a husband's infidelity (N=266 arguments). Roughly 60% of abusive events occurred during arguments over men's diversion of household resources (N=124 abusive events). In multivariate analyses, likelihood of wife abuse is greater in marriages where husbands have affairs, where wives are younger, and where spouses spend more time apart (N=60 husbands, 71 wives). While we find strong support for both male jealousy and paternal disinvestment hypotheses, it is men's infidelity, not women's, that precipitates most instances of marital conflict and wife abuse. We conclude that men's aggression towards their wives facilitates men's diversion of family resources for their selfish interests.     

Pitch lowering enhances men's perceived aggressive intent,not fighting ability

Voice pitch is the primary perceptual correlate of fundamental frequency (f_o) and describes how low or high a voice is perceived by listeners. Prior research showed that men whose habitual voice pitch is lower are perceived to have stronger fighting ability. However, voice pitch is also flexible and can thus be used facultatively to signal states that change situationally, such as current aggressive intent (i.e., readiness to use aggression). Drawing on motivation-structural-rules theory, this research tests the hypothesis that male speakers will be perceived as more likely to attack when they lower (compared to raise) their pitch to address an adversary in a conflict situation. Three experiments using male speakers and listeners supported this hypothesis, both with and without controlling for the perception of the speakers' fighting ability. In contrast, the same experiments found no evidence that pitch lowering enhanced the speakers' perceived fighting ability after controlling for their perceived aggressive intent. Moreover, we found mixed evidence that the speakers' perceived physical strength interacted with pitch modulation to influence their perceived aggressive intent. On balance, these findings show that, at least for men, pitch modulation is primarily an aggressive-intent signal assessed independently of signalers' fighting ability. Future research should distinguish between perceptions of aggressive-intent and fighting-ability when examining the perceptual effects of male voice-pitch modulation in intrasexual competition.     

Effects of extra-pair and within-pair reproductive success on the opportunity for selection in birds

The number of mates, their fecundity, and the number of extra-pairfertilizations can all affect male reproductive success in biparentalspecies. Extra-pair mating in birds has been of particular interest,because it could generate strong levels of sexual selectioneven when a species is socially monogamous. We examined howextra-pair fertilizations affect the opportunity for selectionin the sexually dimorphic common yellowthroat (Geothlypis trichas)and the sexually monomorphic house wren (Troglodytes aedon).We were able to identify sires for at least 95% of all nestlings,and, thus, we were able to make a nearly complete accountingof male reproductive success. Although extra-pair fertilizationswere common in yellowthroats (26% of young) it contributed little(21%) to the total variance in male reproductive success. Mostof the variance in reproductive success (58%) was attributableto the male's within-pair success, which was influenced primarilyby the number of young produced by each mate and the proportionof within-pair young sired. Despite a moderate level of extra-pairfertilizations (10% of young) in house wrens, almost all ofthe variance in male reproductive success (97%) was attributableto within-pair success, particularly the number of social mates.Although extra-pair fertilizations generally increase the variancein male reproductive success, within-pair reproductive successmay be the major source of variation in male reproductive success.Thus, sexual dimorphism in monogamous birds may be influencedmore by the number of mates and their fecundity than by extra-pairmatings.     

On hits and being hit on: error management theory,signal detection theory,and the male sexual overperception bias

Although Error Management Theory (EMT) can explain male sexual overperception, more advanced Signal Detection Theory (SDT) analyses can identify sensitivity and bias separately. An SDT analysis of perceptions of relatively clear interest/disinterest signals (Study 1) found that sensitivity to sexual interest/disinterest signals drove participants' perceptions, rather than an overall bias to perceive sexual interest. Cues of interest were generally underperceived, while sensitivity and accuracy were uniformly high. EMT analysis also found overall sexual interest underperception, but with men slightly overperceiving interest relative to women. These discrepant results were due to EMT using difference scores, which obscure baseline perceptions for men and women. Individual differences in life history strategy, mating strategy, and mate value did not affect sensitivity or bias. Study 2 largely replicated these results using more ambivalent scenarios, except EMT analyses found men's misperception to be significantly larger than women's, despite being closer to pre-rated communication levels. These results show that sexual communication may be more nuanced than previously thought, and that an SDT analysis is more appropriate for such data.     

Physical attractiveness of face and body as indicators of physical fitness in men

Human physical attractiveness appears to be an important signal of mate value that is utilized in mate choice We argue that performance-related physical fitness (PF) was an important facet of ancestral male mate value and, therefore, that a positive relationship exists between PF and physical attractiveness as well as mating success. We investigated these relationships in a sample of 80 young men. In line with our predictions, we found that (i) a composite measure of PF correlated substantially with body attractiveness (r=.43, after controlling for confounds) but not with facial attractiveness; (ii) PF was positively related to various measures of self-reported mating success (r_S ≈ .22); (iii) the relationship between PF and self-reported mating success was partly mediated by body attractiveness. We conclude it is a key function of men's body attractiveness to signal their PF and that men's faces and bodies signal different facets of mate value.     

Sex differences in friendship preferences

Friendships can help us solve a number of challenges, increasing our welfare and fitness. Across evolutionary time, some of the many challenges that friendships helped to solve may have differed between men and women. By considering the specific and potentially distinct recurrent problems men's and women's friendships helped them solve, we can derive predictions about the qualities that would have made men's and women's same-sex friends ideal partners. This logic leads to several predictions about the specific friend preferences that may be differentially prized by men and women. Across three studies (N = 745) with U.S. participants—assessing ideal hypothetical friends, actual friends, and using a paradigm adapted from behavioral economics—we find that men, compared to women, more highly value same-sex friends who are physically formidable, possess high status, possess wealth, and afford access to potential mates. In contrast, women, compared to men, more highly value friends who provide emotional support, intimacy, and useful social information. Findings suggest that the specific friendship qualities men and women preferred differed by sex in ways consistent with a functional account of friendship.     

What do men want? Re-examining whether men benefit from higher fertility than is optimal for women

Several empirical observations suggest that when women have more autonomy over their reproductive decisions, fertility is lower. Some evolutionary theorists have interpreted this as evidence for sexual conflicts of interest, arguing that higher fertility is more adaptive for men than women. We suggest the assumptions underlying these arguments are problematic: assuming that women suffer higher costs of reproduction than men neglects the (different) costs of reproduction for men; the assumption that men can repartner is often false. We use simple models to illustrate that (i) men or women can prefer longer interbirth intervals (IBIs), (ii) if men can only partner with wives sequentially they may favour shorter IBIs than women, but such a strategy would only be optimal for a few men who can repartner. This suggests that an evolved universal male preference for higher fertility than women prefer is implausible and is unlikely to fully account for the empirical data. This further implies that if women have more reproductive autonomy, populations should grow, not decline. More precise theoretical explanations with clearly stated assumptions, and data that better address both ultimate fitness consequences and proximate psychological motivations, are needed to understand under which conditions sexual conflict over reproductive timing should arise.     

Sexual selection and reproductive success in males of the bicolor damselfish, Eupomacentrus partitus (Pisces: Pomacentridae)

Relative reproductive success of male bicolor damselfish, Eupomacentrus partitus, was measured as the number of egg batches obtained per week per male during a 14-month field study. Large and consistent differences in spawning success, observed in seven colonies containing 23 males, demonstrated that mating was non-random. Various physical and behavioural characteristics of males were also monitored. Significant correlations (P<0.05) were found between reproductive success and four variables: frequency of courtship, inter- and intraspecific aggression, and total length. The importance of other factors such as size and location of male territories and time allotment to various activities was also considered. The interactions between these variables, as well as preliminary observations of spawning, suggest that intersexual selection, that is female choice of mates, is the dominant process in sexual selection in this species.     

Sexual Experience Enhances Drosophila melanogaster Male Mating Behavior and Success

Competition for mates is a wide-spread phenomenon affecting individual reproductive success. The ability of animals to adjust their behaviors in response to changing social environment is important and well documented. Drosophila melanogaster males compete with one another for matings with females and modify their reproductive behaviors based on prior social interactions. However, it remains to be determined how male social experience that culminates in mating with a female impacts subsequent male reproductive behaviors and mating success. Here we show that sexual experience enhances future mating success. Previously mated D. melanogaster males adjust their courtship behaviors and out-compete sexually inexperienced males for copulations. Interestingly, courtship experience alone is not sufficient in providing this competitive advantage, indicating that copulation plays a role in reinforcing this social learning. We also show that females use their sense of hearing to preferentially mate with experienced males when given a choice. Our results demonstrate the ability of previously mated males to learn from their positive sexual experiences and adjust their behaviors to gain a mating advantage. These experienced-based changes in behavior reveal strategies that animals likely use to increase their fecundity in natural competitive environments.