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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