McKibbin, W. F., Starratt, V. G., Shackelford, T. K., & Goetz, A. T. (2011). Perceived risk of female infidelity moderates the relationship between objective risk of female infidelity and sexual coercion in Humans (Homo sapiens). Journal of Comparative Psychology, 125, 370-373.

Perceived Risk of Female Infidelity Moderates the Relationship Between Objective Risk of Female Infidelity and Sexual Coercion in Humans (Homo sapiens)

William F. McKibbin, Valerie G. Starratt, Todd K. Shackelford, and Aaron T. Goetz


Female extrapair copulation (EPC) can be costly to a woman’s 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 couple’s last in-pair copulation, more frequently perform partner-directed sexually coercive behaviors. This relationship is moderated, however, by men’s 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 men’s partner-directed sexual coercion.

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Shackelford, T. K., Goetz, A. T., McKibbin, W. F., & Starratt, V. G. (2007). Absence makes the adaptations grow fonder: Proportion of time apart from partner, male sexual psychology, and sperm competition in humans. Journal of Comparative Psychology, 121, 214-220.

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

Todd K. Shackelford, Aaron T. Goetz, William F. McKibbin, and Valerie G. Starratt

Florida Atlantic University


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 couple’s last copulation reported (a) greater sexual interest in his partner, (b) greater
distress in response to his partner’s sexual rejection, and (c) greater sexual persistence in response to his
partner’s sexual rejection. All effects were independent of total time since the couple’s last copulation
and the man’s relationship satisfaction. Discussion addresses limitations of the current research and
situates the current results within the broader comparative literature on adaptation to sperm competition.

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