McKibbin, W.F., Bates, V.M., Shackelford, T.K., Hafen, C.A., & LaMunyon, C.W. (2010). Risk of sperm competition moderates the relationship between men’s satisfaction with their partner and men’s interest in their partner’s copulatory orgasm. Personality and Individual Differences, 49, 961-966

Risk of sperm competition moderates the relationship between men’s satisfaction with their partner and men’s interest in their partner’s copulatory orgasm

William F. McKibbin, Vincent M. Bates, Todd K. Shackelford,
Christopher A. Hafen, and Craig W. LaMunyon


Sperm competition occurs when the sperm of multiple males concurrently occupy a female’s reproductive
tract and compete for fertilization. Sperm competition may have been a recurrent adaptive problem over human evolutionary history (Shackelford & Pound, 2006). Women’s orgasm may facilitate selective uptake and retention of a particular man’s sperm (Thornhill & Gangestad, 2008). Men who are more satisfied with and invested in their relationship may experience greater costs in the event of sperm competition and potential cuckoldry. Therefore, these men may be especially interested in ensuring their partner’s copulatory orgasm. We hypothesized that men’s relationship satisfaction and investment would predict interest in their partner’s copulatory orgasm, and that sperm competition risk would moderate the association between relationship satisfaction and interest in partner’s copulatory orgasm. Using structural equation modeling on self-report data secured from 229 men in a committed heterosexual relationship, we tested and found support for these hypotheses.

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Schützwohl, A., Fuchs, A., McKibbin W.F., & Shackelford, T.K. (2009). How willing are you to accept sexual requests from slightly unattractive to exceptionally attractive imagined requestors? Human Nature, 20, 282-293.

How Willing Are You to Accept Sexual Requests from Slightly Unattractive to Exceptionally Attractive Imagined Requestors?

Achim Schützwohl, Amrei Fuchs,
William F. McKibbin and Todd K. Shackelford


 In their classic study of differences in mating strategies, Clark and Hatfield (1989, Journal of Psychology and Human Sexuality, 2, 39–54) found that men and women demonstrated a striking difference in interest in casual sex. The current study examined the role of an imagined requestor’s physical attractiveness (slightly unattractive, moderately attractive, and exceptionally attractive) on men’s and women’s willingness to accept three different requests (go out, come to apartment, go to bed) as reflected in answers to a questionnaire. We tested two hypotheses with a sample of 427 men and 443 women from three countries. Hypothesis 1 states that men, relative to women, will demonstrate a greater willingness to accept the “come to apartment” and “go to bed” requests but not the “go out” request for all three levels of requestor attractiveness. This  hypothesis reflects Clark and Hatfield’s main findings. Hypothesis 2 states that the physical attractiveness of a potential partner will have a greater effect on women’s than on men’s willingness to accept all three requests, and particularly for the explicit request for casual sex. The results partially supported Hypothesis 1 and fully supported Hypothesis 2. The discussion highlights limitations of the current research and presents directions for future research.

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