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The amazing way new sexual partners affect male sperm

Scientists are studying the ways in which novelty affects our sexual selves. Here's what they've found


Carrie Weisman
August 14, 2015 2:57AM (UTC)
This article originally appeared on AlterNet.

AlterNetWhen it comes to relationships, mainstream society tends to favor the “till death do us part” approach. But new research conducted by the College of Wooster suggests one particular part of the male body may not be wired for the long monogamous haul.

Paul Joseph, a 2014 Wooster graduate, and Laura Sirot, an assistant professor of biology at Wooster, teamed up with researchers at the Cleveland Clinic’s Center for Reproductive Medicine to investigate some of the mysteries surrounding male infertility. They rounded up 21 heterosexual men and asked them to masturbate to seven porn flicks over a 15-day period. The first six films featured the same actress and actor. The seventh featured the same actor with a different actress.

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What the team found holds some pretty big implications for reproductive science. When exposed to images of a novel woman, participants ejaculated at a faster rate with higher volumes of semen containing higher numbers of motile sperm. That is to say, when watching the film featuring a new actress, participants came faster, and produced more quality sperm.

The men were also asked to refrain from drinking and sex in the 48 hours leading up to each of the sessions.

The results of the study, published in the June issue of Evolutionary Psychological Science, suggest, “Human males ejaculate more quickly and invest more in ejaculates with novel females.”

The idea of novelty surrounding sexual selection isn’t new. In fact, it’s one of the main arguments put forward by anti-porn activist Gary Wilson, who argues that “Constant novelty at a click can cause addiction.”

But those who conducted the experiment are walking away with other ideas about ways in which novelty affects our sexual selves. Sirot, co-author of the study, told the Huffington Post via email, “Our study does not suggest anything about whether monogamy was favored or disfavored by natural selection. However, the result of this study and other studies of human differential ejaculation behavior suggest that extra-pair (or extramarital) copulations may have occurred in our evolutionary past.”

The findings are in keeping with what’s known as the  Coolidge Effect, which Wikipedia describes as a “phenomenon seen in the mammalian species whereby the quality and quantity of a male’s sperm would decrease with repeated exposure to images of the same woman but subsequently increase upon exposure to images of a new woman.”

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The study may provide an additional service to couples trying to conceive, particularly the women.

When looking for answers about their reproductive health, most men will take a trip to the doctor’s office. There, they’ll be asked to provide a semen sample, likely produced while masturbating to porn. Porn featuring images of “novel" women, i.e., women who don’t look like their wives or girlfriends. And that could yield some misleading results.

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Paul Joseph told the Huffington Post in a written statement, “The ejaculates produced in fertility clinics may be of higher quality than usual, which may conceal any potential fertility problems experienced in the bedroom." So the focus will shift to the female party. She may be asked to go through a series of invasive procedures to identify any potential fertility problems, that, as David Freeman of the Huffington Post notes, may “really lie with their partners.”

The study's findings may, in the future, help spare some women such experiences.

Of course, no study is foolproof. Sirot noted, “It is possible that, by chance, the actresses or scenes randomly chosen for the novel trial for each participant tended to be ones that the men found more arousing."

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She added, "We did not ask the men for a subjective rating of their level of arousal. However, our experiment was deliberately designed to try to eliminate any consistent differences between the video clips other than the novelty itself."

Carrie Weisman is an AlterNet staff writer who focuses on sex, relationships and culture. Got tips, ideas or a first-person story? Email her


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