Gender differences in sexual jealousy: Adaptionist or social learning explanation?

It has often been speculated, and some evidence suggests, that men and women differ in the elicitation of jealousy: Men appear to be more likely than women to become upset over threats to sexual exclusivity; whereas women are more likely than men to react negatively to potential loss of partner time and attention. Both adaptionist and traditional social learning theories have been used to explain these apparent gender differences. In the present article we outline both explanations and review the relevant psychological literature on gender differences in the elicitation of jealousy. We propose that the difference in men's and women's psychological mechanisms for elicitation of jealousy is best characterized (at least in this culture) as a greater sensitivity among men to cues indicative of possible sexual infidelity rather than greater emotional upset in response to the occurence of extradyadic sex on the part of one's mate. We also provide data testing a traditional social learning explanation for the elicitation of jealousy. Results of a survey administered to college students (N = 223) demonstrate the subtle nature of gender differences in the elicitation of jealousy within this culture. Men and women were most likely to differ (in the hypothesized directions) when items pertained to concern over a partner's potential extradyadic sex rather than to reactions to sexual infidelity that is suspected to have already occurred. Although men reported placing more value on sexual activity within dating relationships and women reported placing more value on emotional intimacy, these ratings of relationship rewards did not explain the gender differences in reported jealousy. Results failed to support a traditional social learning explanation of jealousy and are discussed with regard to evolutionary theory and directions for future research.     

Evolution,Sex, and Jealousy: Investigation With a Sample From Sweden

When asked to choose which would be most upsetting, a mate’s sexual or emotional infidelity, past research has demonstrated that men are more likely than women to choose sexual infidelity, whereas women are more likely than men to choose emotional infidelity. Explanation of this sex difference has been controversial. In the current study we attempted to replicate previous research by examining a sample of college students in Sweden. In doing so, we also investigated the “double-shot” explanation. In the current study, the majority of men chose the sexual infidelity scenario as most upsetting, whereas the majority of women chose the emotional infidelity scenario as most upsetting. Contrary to the double-shot explanation, choice of scenario was unrelated to attitudes regarding whether the other sex was capable of satisfying sexual relations outside of a love relationship.     

Morbid jealousy from an evolutionary psychological perspective

Individuals diagnosed with morbid jealousy have hypersensitive jealousy mechanisms that cause them to have irrational thoughts about their partner's fidelity and to exhibit extreme behaviors. Using a newly constructed database of 398 cases of morbid jealousy reported in the literature from 1940 to 2002, we tested four evolutionarily informed hypotheses about normally functioning jealousy mechanisms and applied them to this novel population of individuals diagnosed with morbid jealousy. We hypothesized that a greater percentage of men than women diagnosed with morbid jealousy would be focused on a partner's sexual infidelity and on indicators of a rival's status and resources and that a greater percentage of women than men diagnosed with morbid jealousy would be focused on a partner's emotional infidelity and on indicators of a rival's youth and physical attractiveness. All four hypotheses were supported. The results suggest continuity between normal jealousy and morbid jealousy and highlight the heuristic value of using archival databases to test evolutionarily informed hypotheses.     

Upset in response to a Sibling’s partner’s infidelities

Using data collected from people with at least one brother and one sister, and consistent with an evolutionary perspective, we find that older men and women (a) are more upset by a brother’s partner’s sexual infidelity than by her emotional infidelity and (b) are more upset by a sister’s partner’s emotional infidelity than by his sexual infidelity. There were no effects of participant sex or sex of in-law on upset over a sibling’s partner’s infidelities, but there was an effect of participant sex on reports of upset over one’s own partner’s infidelities. The results suggest that the key variable among older participants is the sex of the sibling or, correspondingly, the sex of the sibling’s partner, as predicted from an evolutionary analysis of reproductive costs, and not the sex of the participant, as predicted from a socialization perspective. Discussion offers directions for future work on jealousy.     

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.     

Sex differences (and similarities) in jealousy: The moderating influence of infidelity experience and sexual orientation of the infidelity

Past demonstrations of sex differences in jealousy have generally employed Buss et al.'s [Psychol. Sci. 3 (1992) 251] forced-choice methodology, a limitation criticized by DeSteno and Salovey [Psychol. Sci. 7 (1996) 367]. The present studies address this criticism by demonstrating the sex difference using both forced-choice and continuous measures of jealousy. In addition, the results distinguish two important moderators of the sex difference: infidelity experience, in which male victims and female perpetrators of infidelity reported greater distress in response to a sexual infidelity, and sexual orientation of the infidelity, in which the sex difference disappears completely when an infidelity carries no risk of conception because an opposite-sex partner has become involved with a same-sex lover.     

Sex (similarities and) differences in friendship jealousy

Friendships provide material benefits, bolster health, and may help solve adaptive challenges. However, a recurrent obstacle to sustaining those friendships—and thus enjoying many friendship-mediated fitness benefits—is interference from other people. Friendship jealousy may be well-designed for helping both men and women meet the recurrent, adaptive challenge of retaining friends in the face of such third-party interference. Although we thus expect several sex similarities in the general cognitive architecture of friendship jealousy (e.g., it is attuned to friend value), there are also sex differences in friendship structures and historical functions, which might influence the inputs of friendship jealousy (e.g., the value of any one friendship). If so, we should also expect some sex differences in friendship jealousy. Findings from a reanalysis of previously-published data and a new experiment, including both U.S. student and adult community participants (N = 993), provide initial support for three predicted sex differences: women (versus men) report greater friendship jealousy at the prospective loss of best friends to others, men (versus women) report greater friendship jealousy at the prospective loss of acquaintances to others, and men's (but not women's) friendship jealousy is enhanced in the context of intergroup contests.     

Sexual jealousy as a facultative trait: Evidence from the pattern of sex differences in adults from China and the United States

Across two studies, 716 and 308 undergraduate students from the United States and mainland China, respectively, were administered a series of measures on jealousy, emotional responses to partner infidelity, family background, and personality. Across both studies for the U.S. and Chinese samples, a higher proportion of males than females reported more distress to a partner's imagined sexual infidelity than to emotional infidelity, whereas a higher proportion of females than males reported more distress to a partner's emotional infidelity than to sexual infidelity, consistent with theoretical expectations and previous empirical research. However, a much higher proportion of U.S. males and females reported more distress to sexual infidelity than their same-sex Chinese peers, suggesting that the tendency toward sexual jealousy might be facultatively influenced by sexual permissiveness in the general culture. The overall pattern of results is considered in terms of individual and contextual differences in the expression of jealousy, as well as in terms of the emotional and behavioral responses associated with jealousy reactions.     

Modernization,Sexual Risk-Taking,and Gynecological Morbidity among Bolivian Forager-Horticulturalists

Sexual risk-taking and reproductive morbidity are common among rapidly modernizing populations with little material wealth, limited schooling, minimal access to modern contraception and healthcare, and gendered inequalities in resource access that limit female autonomy in cohabiting relationships. Few studies have examined how modernization influences sexual risk-taking and reproductive health early in demographic transition. Tsimane are a natural fertility population of Bolivian forager-farmers; they are not urbanized, reside in small-scale villages, and lack public health infrastructure. We test whether modernization is associated with greater sexual risk-taking, report prevalence of gynecological morbidity (GM), and test whether modernization, sexual risk-taking and parity are associated with greater risk of GM. Data were collected from 2002–2010 using interviews, clinical exams, and laboratory analysis of cervical cells. We find opposing effects of modernization on both sexual risk-taking and risk of GM. Residential proximity to town and Spanish fluency are associated with greater likelihood of men’s infidelity, and with number of lifetime sexual partners for men and women. However, for women, literacy is associated with delayed sexual debut after controlling for town proximity. Fifty-five percent of women present at least one clinical indicator of GM (n = 377); 48% present inflammation of cervical cells, and in 11% the inflammation results from sexually transmitted infection (trichomoniasis). Despite having easier access to modern healthcare, women residing near town experience greater likelihood of cervical inflammation and trichomoniasis relative to women in remote villages; women who are fluent in Spanish are also more likely to present trichomoniasis relative to women with moderate or no fluency. However, literate women experience lower likelihood of trichomoniasis. Parity has no effect on risk of GM. Our results suggest a net increase in risk of reproductive morbidity among rapidly modernizing, resource-stressed populations.     

Estrogens and relationship jealousy

The relation between sex hormones and responses to partner infidelity was explored in two studies reported here. The first confirmed the standard sex difference in relationship jealousy, that males (n=133) are relatively more distressed by a partner’s sexual infidelity and females (n=159) by a partner’s emotional infidelity. The study also revealed that females using hormone-based birth control (n=61) tended more toward sexual jealousy than did other females, and reported more intense affective responses to partner infidelity (n=77). In study two, 47 females were assessed four times across one month. Patterns of response to partner infidelity did not vary by week of menstrual cycle, but significant relations between salivary estradiol level and jealousy responses were obtained during the time of rising and high fertility risk. The implications, at least for females, are that any evolved psychological, affective, or behavioral dispositions regarding reproduction-related relationships are potentially moderated by estradiol, and that the use of synthetic hormones may disrupt this relation. David C. Geary is the Frederick A. Middlebush Professor of Psychological Sciences at the University of Missouri at Columbia. He has published nearly 100 articles and chapters across a wide range of topics, including cognitive and developmental psychology, education, evolutionary biology, and medicine. His two books, Children’s Mathematical Development (1984) and Male, Female: The Evolution of Human Sex Differences (1988), have been published by the American Psychological Association. M. Catherine DeSoto recently completed her Ph.D. in psychological sciences at the University of Missouri at Columbia and is currently assistant professor of psychobiology at the University of Northern Iowa. Her research primarily focuses on the interface between biology and behavior, including the relation between sex hormones and personality disorders. Mary K. Hoard is completing her Ph.D. studies in psychological sciences at the University of Missouri at Columbia and is currently a research specialist in the Department of Psychological Sciences. Her research interests focus on children’s cognitive development, as well as the relation between sleep and cognitive and psychological functioning. Melanie Skaggs Sheldon is a graduate student in the Department of Psychological Sciences at the University of Missouri at Columbia. Her research interests include social cooperation, sexual behavior, and personality, as understood from an evolutionary perspective. M. Lynne Cooper is a professor of psychological sciences and director of the training program in social psychology at the University of Missouri at Columbia. She is an associate editor of the Journal of Personality and the author of more than 60 articles and chapters in the areas of personality and social psychology. Her primary research efforts involve directing a longitudinal study of risky sexual behavior of adolescents and young adults.     

Male facial attractiveness and masculinity may provide sex‐ and culture‐independent cues to semen quality

Phenotype‐linked fertility hypothesis (PLFH) predicts that male secondary sexual traits reveal honest information about male fertilization ability. However, PLFH has rarely been studied in humans. The aim of the present study was to test PLFH in humans and to investigate whether potential ability to select fertile partners is independent of sex or cultural background. We found that on the contrary to the hypothesis, facial masculinity was negatively associated with semen quality. As increased levels of testosterone have been demonstrated to impair sperm production, this finding may indicate a trade‐off between investments in secondary sexual signalling (i.e. facial masculinity) and fertility or status‐dependent differences in investments in semen quality. In both sexes and nationalities (Spanish and Colombian), ranked male facial attractiveness predicted male semen quality. However, Spanish males and females estimated facial images generally more attractive (gave higher ranks) than Colombian raters, and in both nationalities, males gave higher ranks than females. This suggests that male facial cues may provide culture‐ and sex‐independent information about male fertility. However, our results also indicate that humans may be more sensitive to facial attractiveness cues within their own populations and also that males may generally overestimate the attractiveness of other men to females.     

Why do men marry and why do they stray?

Humans are quite unusual compared to other great apes in that reproduction typically takes place within long-term, iteroparous pairings--social arrangements that have been culturally reified as the institution of marriage. With respect to male behaviour, explanations of marriage fall into two major schools of thought. One holds that marriage facilitates a sexual division of labour and paternal investment, both important to the rearing of offspring that are born helpless and remain dependent for remarkably long periods (provisioning model). And the other suggests that the main benefits which men receive from entering into marriage derive from monopolizing access to women's fertility (mating effort model). In this paper, we explore extramarital sexual relationships and the conditions under which they occur as a means of testing predictions derived from these two models. Using data on men's extramarital sexual relationships among Tsimane forager-horticulturists in lowland Bolivia, we tested whether infidelity was more common when men had less of an opportunity to invest in their children or when they risked losing less fertility. We found that Tsimane men appear to be biasing the timing of their affairs to when they are younger and have fewer children, supporting the provisioning model.     

Women's height,reproductive success and the evolution of sexual dimorphism in modern humans

Recent studies have shown that, in contemporary populations, tall men have greater reproductive success than shorter men. This appears to be due to their greater ability to attract mates. To our knowledge, no comparable results have yet been reported for women. This study used data from Britain's National Child Development Study to examine the life histories of a nationally representative group of women. Height was weakly but significantly related to reproductive success. The relationship was U-shaped, with deficits at the extremes of height. This pattern was largely due to poor health among extremely tall and extremely short women. However, the maximum reproductive success was found below the mean height for women. Thus, selection appears to be sexually disruptive in this population, favouring tall men and short women. Over evolutionary time, such a situation tends to maintain sexual dimorphism. Men do not use stature as a positive mate-choice criterion as women do. It is argued that there is good evolutionary reason for this, because men are orientated towards cues of fertility, and female height, being positively related to age of sexual maturity, is not such a cue.     

LOSS OF SEX IN CLONAL POPULATIONS OF A FLOWERING PLANT,DECODON VERTICILLATUS (LYTHRACEAE)

The loss of traits that no longer increase fitness is a pervasive feature of evolution, although detailed studies of the genetic, developmental, and evolutionary factors involved are few. Most perennial plants practice both sexual and clonal reproduction, and it has been hypothesized that populations with little sexual recruitment may lose the capacity for sexual reproduction by fixing mutations that disable one or more of the many processes involved in sex. The clonal, tristylous aquatic plant, Decodon verticillatus, exhibits marked geographical variation in sexual recruitment. Populations at the northern limit of the range are usually monomorphic for style length consist of single genotypes, and produce almost no seed, due, in part, to environmental conditions that inhibit pollination, fertilization, and seed maturation. Controlled crosses in a greenhouse provided evidence for greatly reduced sexual capacity in an exclusively clonal, monomorphic population. Plants from this infertile population produced only 3–18% as many seeds per pollination as fertile populations. Observations of pollen tube growth indicated that infertility is due to severe reductions in pollen tube numbers both early after pollination and later when pollen tubes were traversing the ovary, due primarily to the inability of pistils to support normal tube growth. A three-year greenhouse experiment comparing fertility, survival, and growth of F1 progenies produced from reciprocal crosses between plants from the infertile population and those from nearby fertile populations suggested that the genetic basis for infertility is simple and may involve a single recessive mutation. In addition, the results did not reveal any association between infertility and other aspects of survival and vegetative vigor. The infertile genotype was likely fixed in the population through founder effect rather than indirect selection resulting from antagonistic pleiotropy or direct selection of advantages associated with reduced investment in sexual reproduction. A broader comparison of sexual fertility in 15 clonal, monomorphic populations and five genotypically diverse, trimorphic populations under greenhouse conditions revealed substantial infertility in all but one monomorphic population. Populations varied somewhat in the stage at which infertility was expressed, however, pollen tube growth was impaired in all populations. These results provide strong support for the hypothesis that complex traits like sex are degraded by mutation when they no longer increase fitness.     

Hormonal contraceptive use and mate retention behavior in women and their male partners

Female hormonal contraceptive use has been associated with a variety of physical and psychological side effects. Women who use hormonal contraceptives report more intense affective responses to partner infidelity and greater overall sexual jealousy than women not using hormonal contraceptives. Recently, researchers have found that using hormonal contraceptives with higher levels of synthetic estradiol, but not progestin, is associated with significantly higher levels of self-reported jealousy in women. Here, we extend these findings by examining the relationship between mate retention behavior in heterosexual women and their male partners and women's use of hormonal contraceptives. We find that women using hormonal contraceptives report more frequent use of mate retention tactics, specifically behaviors directed toward their partners (i.e., intersexual manipulations). Men partnered with women using hormonal contraceptives also report more frequent mate retention behavior, although this relationship may be confounded by relationship satisfaction. Additionally, among women using hormonal contraceptives, the dose of synthetic estradiol, but not of synthetic progesterone, positively predicts mate retention behavior frequency. These findings demonstrate how hormonal contraceptive use may influence behavior that directly affects the quality of romantic relationships as perceived by both female and male partners.     

Spousal age-gaps,partner preferences,and consequences for well-being in four Colombian communities

Across cultures, women tend to marry older men. This phenomenon is commonly described as the result of evolved mate choice preferences, which cause men to base reproductive decisions on cues of youth and fertility in women, and women to base such decisions on cues of wealth and status in men. Other researchers have challenged this idea, arguing that husband-older spousal age-gaps might not be consistent with the joint preferences of men and women; age-gaps might instead arise as the result of sexual conflict. In such cases, the realized age-gap could benefit one party at a cost to the other. In practice, large age-gaps may result in negative outcomes for younger women married to older men—e.g., because of power differences in these relationships. Testing for the existence of sexual conflict over the size of the spousal age-gap in Tanzania, researchers found no evidence that large age-gaps are harmful to women. Here, we conceptually replicate this previous work, and assess the relationship between spousal age-gaps, partner preferences, and individual well-being in four communities in Colombia. We extend prior methods by inferring the size of idealized age-gaps using network structured mate-choice games, and measuring the realized age-gap directly among ever-married partners. Our analyses suggest that there is limited evidence of sexual conflict over the size of the spousal age-gap in these communities. First, realized age-gaps are not large on average—around 1–7 years across communities. Second, the age-gaps that do exist are consistent with the preferences of both men and women—at least during their early to middle reproductive periods. And, lastly, large age-gaps are not negatively associated with measures of fertility or well-being for either sex. Our results underscore the importance of appreciating the cultural context within which behavioral practices with potentially negative consequences are situated.     

Sexual coercion and forced in-pair copulation as sperm competition tactics in humans

Rape of women by men might be generated either by a specialized rape adaptation or as a by-product of other psychological adaptations. Although increasing number of sexual partners is a proposed benefit of rape according to the “rape as an adaptation” and the “rape as a by-product” hypotheses, neither hypothesis addresses directly why some men rape their long-term partners, to whom they already have sexual access. In two studies we tested specific hypotheses derived from the general hypothesis that sexual coercion in the context of an intimate relationship may function as a sperm competition tactic. We hypothesized that men’s sexual coercion in the context of an intimate relationship is related positively to his partner’s perceived infidelities and that men’s sexual coercion is related positively to their mate retention behaviors (behaviors designed to prevent a partner’s infidelity). The results from Study 1 (self-reports from 246 men) and Study 2 (partner-reports from 276 women) supported the hypotheses. The Discussion section addresses limitations of this research and highlights future directions for research on sexual coercion in intimate relationships.     

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.