Previous research suggests that human males, like males of many mammalian and avian species, adjust their ejaculate quality in accordance with sperm competition risk. Men who spend less time with their regular female partner since the couple’s last copulation produce ejaculates with more sperm at the couple’s next copulation (Baker & Bellis, 1993). We conducted a conceptual replication of this research to investigate whether sperm competition risk predicts ejaculate adjustment in human males using additional measures of sperm competition risk (e.g., perceptions of partner infidelity, presence of potential sexual rivals) and updated laser-optic semen analysis technology. We collected data from 34 heterosexual couples (age range 18–32 years) from a university population who completed self-report surveys on their relationship dynamics and provided six ejaculate samples (three copulatory and three masturbatory) across a 45-day period. Time spent together since the couple’s last copulation was not significantly associated with ejaculate quality. However, sperm concentration for copulatory ejaculates was higher for men who perceived more potential sexual rivals. Discussion situates the current results within the literature on human sperm competition and suggests several directions for future research.

先前的研究表明，人类男性与许多哺乳动物和鸟类物种的雄性一样，会根据精子竞争风险调整其射精质量。自从这对夫妇最后一次交配以来，与他们的固定女性伴侣相处时间较少的男性在这对夫妇的下一次交配时会产生更多的精子（Baker & Bellis，1993）。我们对这项研究进行了概念复制，以调查精子竞争风险是否使用额外的精子竞争风险测量（例如，对伴侣不忠的看法、潜在性竞争对手的存在）和更新的激光光学精液分析技术来预测人类男性的射精调整。我们从大学人群中收集了 34 对异性恋夫妇 （年龄范围为 18-32 岁） 的数据，他们完成了关于他们关系动态的自我报告调查，并在 45 天内提供了 6 个射精样本 （3 个交配样本和 3 个手本）。自这对夫妇最后一次交配以来一起度过的时间与射精质量没有显着相关性。然而，对于认为更多潜在性竞争对手的男配射精的精子浓度更高。讨论将当前结果置于人类精子竞争的文献中，并提出了未来研究的几个方向。