Original article:

Oral sex, semen displacement, and sexual arousal: Testing the ejaculate adjustment hypothesis

Evolutionary Psychology 11(5): 1130-1139 Michael N. Pham, Department of Psychology, Oakland University, Rochester, Michigan, USA, mnpham@oakland.eduTodd K. Shackelford, Department of Psychology, Oakland University, Rochester, Michigan, USALisa L. M. Welling, Department of Psychology, Oakland University, Rochester, Michigan, USAAlyse D. Ehrke, Department of Psychology, Oakland University, Rochester, Michigan, USAYael Sela, Department of Psychology, Oakland University, Rochester, Michigan, USAAaron T. Goetz, Department of Psychology, California State University Fullerton, Fullerton, California, USA

Abstract

Male Indian Flying Foxes (Pteropus giganteus) that spend more time performing oral sex on a female also spend more time copulating with her. In humans, men who spend more time copulating with their regular partner also perform more “semen-displacing” copulatory behaviors (e.g., deeper, more vigorous penile thrusting). We investigated whether men who spend more time performing oral sex on their regular partner also spend more time copulating with her and perform more semen-displacing copulatory behaviors. We proposed and tested the ejaculate adjustment hypothesis for men’s copulatory behaviors: Men adjust their copulatory behaviors to increase their sexual arousal and consequent ejaculate quality, thereby increasing their chances of success in sperm competition. Two hundred and thirty-three men in a committed, heterosexual relationship responded to questions about their copulatory behavior and sexual arousal during their most recent sexual encounter with their long-term partner. The results indicated that men who spend more time performing oral sex on their partner also spend more time copulating with her, perform more semen-displacing copulatory behaviors, and report greater sexual arousal. We discuss limitations to the current research and highlight the heuristic value of sperm competition theory for understanding human sexual behaviors.

Keywords

sperm competition, oral sex, semen displacement, sexual arousal, semen quality

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Evolutionary Psychology - An open access peer-reviewed journal - ISSN 1474-7049 © Ian Pitchford and Robert M. Young; individual articles © the author(s)
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