Aaron T. Goetz

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.

Sexual Coercion in Intimate Relationships: A Comparative Analysis of the Effects of Women's Infidelity and Men's Dominance and Control

Researchers studying the proximate (or immediate) causes of sexual coercion have proposed that partner rape is motivated by a man’s attempt to dominate and control his partner and that this expression of power is the product of men’s social roles. Researchers studying the ultimate (or evolutionary) causes, in contrast, have proposed that partner rape may function as an anti-cuckoldry tactic, with its occurrence related to a man’s suspicions of his partner’s sexual infidelity. In two studies, we collected data relevant to both perspectives to explore how these variables interact with men’s sexual coercion in an intimate relationship. Regression analyses from Study 1 (self-reports from 256 men) and Study 2 (partner-reports from 290 women) indicated that men’s sexual coercion of their partners was consistently predicted by female infidelity and men’s controlling behavior, suggesting that both variables are necessary to explain men’s sexual coercion. Discussion addressed limitations of the current research and highlighted the importance of integrating multiple levels of analysis when studying men’s sexual coercion of their intimate partners.

Men's sexual coercion in intimate relationships: development and initial validation of the Sexual Coercion in Intimate Relationships scale

We report the development and initial validation of the Sexual Coercion in Intimate Relationships Scale (SCIRS), a measure designed to assess the prevalence and severity of sexual coercion in committed intimate relationships. We review existing measures of sexual coercion and discuss their limitations, describe the identification of the SCIRS items, perform a principal components analysis and describe the resulting three components, and present evidence for the convergent and discriminative validity of the SCIRS. Because sexual coercion in intimate relationships often takes the form of subtle tactics, the SCIRS items assess communicative tactics such as hinting and subtle manipulations in addition to tactics such as the use of physical force. The SCIRS provides researchers and clinicians with a valid, reliable, and comprehensive measure with which to study the dynamics of sexual coercion in intimate relationships.

Why do men rape? An evolutionary psychological perspective.

Rape of women by men has occurred throughout recorded history and across cultures. In this article, we discuss rape from an evolutionary psychological perspective. Evolutionary psychology is a powerful heuristic tool that allows researchers to develop and test novel hypotheses about complex behaviors such as rape. Some researchers have argued that men have evolved psychological mechanisms that motivate them to rape in specific contexts. We discuss evidence consistent with this claim, and argue that a more nuanced view of mens rape behavior is necessary. We propose that it may be useful to characterize rapists as belonging to one of several types, distinguished by individual differences as well as by the circumstances in which they are predicted to commit rape. We discuss research evidence in support of each rapist type, as well as the need for future research. Finally, we discuss research concerning womens rape-avoidance psychology and behavior.

Absence Makes the Adaptations Grow Fonder: Proportion of Time Apart From Partner, Male Sexual Psychology, and Sperm Competition in Humans (Homo sapiens)

Sperm competition occurs when the sperm of multiple males concurrently occupy the reproductive tract of a female and compete to fertilize an egg. We used a questionnaire to investigate psychological responses to the risk of sperm competition for 237 men in committed, sexual relationships. As predicted, a man who spends a greater (relative to a man who spends a lesser) proportion of time apart from his partner since the couples last copulation reported (a) greater sexual interest in his partner, (b) greater distress in response to his partners sexual rejection, and (c) greater sexual persistence in response to his partners sexual rejection. All effects were independent of total time since the couples last copulation and the mans relationship satisfaction. Discussion addresses limitations of the current research and situates the current results within the broader comparative literature on adaptation to sperm competition.

Psychological and physiological adaptations to sperm competition in humans

Postcopulatory competition between males, in the form of sperm competition, is a widespread phenomenon in many animal species. The extent to which sperm competition has been an important selective pressure during human evolution remains controversial, however. The authors review critically the evidence that human males and females have psychological, behavioral, and physiological adaptations that evolved in response to selection pressures associated with sperm competition. The authors consider, using evidence from contemporary societies, whether sperm competition is likely to have been a significant adaptive problem for ancestral humans and examine the evidence suggesting that human males have physiological and psychological mechanisms that allow for “prudent” sperm allocation in response to variations in the risk of sperm competition.

Men’s Partner-Directed Insults and Sexual Coercion in Intimate Relationships

Women who have been sexually coerced by an intimate partner experience many negative health consequences. Recent research has focused on predicting this sexual coercion. In two studies, we investigated the relationship between men’s use of partner-directed insults and sexually coercive behaviors in the context of intimate relationships. Study 1 secured self-reports from 247 men on the Partner-Directed Insults Scale and the Sexual Coercion in Intimate Relationships Scale. Study 2 obtained partner-reports from 378 women on the same measures. Across both studies, results indicate that men’s use of sexually coercive behaviors can be statistically predicted by the frequency and content of the insults that men direct at their intimate partner. Insults derogating a partner’s value as a person and accusing a partner of sexual infidelity were most useful in predicting sexual coercion. The discussion notes limitations of the current research and highlights directions for future research.

From Mate Retention to Murder: Evolutionary Psychological Perspectives on Men's Partner-Directed Violence

In response to the tragically high incidence and negative consequences of female-directed violence in intimate relationships, a large literature has been dedicated to the investigation of the proximate and the ultimate or evolutionary predictors of mens partner-directed violence. Evolutionary psychology offers a framework for investigating the design of evolved information-processing mechanisms that motivate costly behaviors such as mens partner-directed violence. We review several forms of mens partner-directed violence, including insults, sexual coercion, physical violence, and homicide, from an evolutionary psychological perspective and with a particular focus on the adaptive problem of paternity uncertainty. The problem of paternity uncertainty is hypothesized to have selected for the emotion of male sexual jealousy, which in turn motivates mens nonviolent and violent mate retention behaviors. We review empirical evidence for the relationships among paternity uncertainty, male sexual jealousy, and mens partner-directed violence. We propose that a comprehensive understanding of mens partner-directed violence will be achieved only by careful consideration of both proximate and ultimate causes.

Mate guarding and frequent in-pair copulation in humans

Cuckoldry is an adaptive problem faced by parentally investing males of socially monogamous species (e.g., humans and many avian species). Mate guarding and frequent in-pair copulation (IPC) may have evolved as anti-cuckoldry tactics in avian species and in humans. In some avian species, the tactics are used concurrently, with the result that mate guarding behaviors and IPC frequency are correlated positively. In other avian species, the tactics are compensatory, with the result that mate guarding behaviors and IPC frequency are correlated negatively. The relationship between mate guarding and IPC frequency in humans is unknown. Avian males that use these tactics concurrently share with human males an inability to guard a female partner continuously during her peak fertile period. We hypothesized, therefore, that men’s mate guarding and IPC frequency function as concurrent anti-cuckoldry tactics, resulting in a positive correlation between them. Study 1 (n=305) secured men’s self-reports of mate guarding and IPC frequency. Study 2 (n+367) secured women’s reports of their partners’ mate guarding and IPC frequency. The concurrent tactics hypothesis was supported in both studies: Men’s mate guarding and IPC frequency are correlated positively, and this association is not attributable to male age, female age, relationship satisfaction, relationship length, or time that the couple spends together. The Discussion section addresses potential limitations of this research and future research directions.

Perceived risk of female infidelity moderates the relationship between objective risk of female infidelity and sexual coercion in humans (Homo sapiens).

Female extrapair copulation (EPC) can be costly to a womans long-term romantic partner. If a woman has copulated recently with a man other than her long-term partner, her reproductive tract may contain the sperm of both men, initiating sperm competition (whereby sperm from multiple males compete to fertilize an egg). Should the woman become pregnant, her long-term partner is at risk of cuckoldry-investing unwittingly in offspring to whom he is not genetically related. Previous research in humans (Homo sapiens) and in nonhuman animals suggests that males have evolved tactics such as partner-directed sexual coercion that reduce the risk of cuckoldry. The current research provides preliminary evidence that mated men (n = 223) at greater risk of partner EPC, measured as having spent a greater proportion of time apart from their partner since the couples last in-pair copulation, more frequently perform partner-directed sexually coercive behaviors. This relationship is moderated, however, by mens perceived risk of partner EPC, such that the correlation between the proportion of time spent apart since last in-pair copulation and sexually coercive behaviors remains significant only for those men who perceive themselves to be at some risk of partner EPC. Discussion addresses limitations of this research and highlights directions for future research investigating the relationship between female EPC and mens partner-directed sexual coercion.