Men - Here's How A New Woman Alters Your Ejaculations

Young man is sitting in bed and watching pornography on laptop. LoloStock/Shutterstock

Sperm competition has been observed extensively in the animal world and it can get pretty weird. Some male spiders voluntarily cut off their own penis and leave it in females as a “plug” after copulation, and nematode worms increase the amount of sperm they ejaculate when in the presence of competing males. So, what about humans? A new study suggests that when men were exposed to a different actress while watching porn, they ejaculated quicker and produced more semen. Yes, these men were asked to watch porn and ejaculate for science.

There has been very little research on how semen ejaculation is allocated in different situations in humans. For the most part, humans seem to lack many of these adaptations we see in other animals, which makes sense because humans are predominantly monogamous. But, researchers suggest sperm competition could exist in humans. 

For the latest study, researchers set out to investigate whether a “novel” stimulus, which was a porn film with a new actress, would have an effect on male ejaculation. Researchers analyzed the time of ejaculation, the volume and number of motile sperm produced by 21 self-identified heterosexual men between the ages of 18 and 23 years old.

Why porn? Samantha Leivers, an expert in male sexual behavior from The University of Western Australia, who was not involved in the study, tells IFLScience that men produce better quality ejaculates when using pornographic material compared to producing a semen sample with no stimuli whatsoever. The best quality ejaculates tend to be produced through sex than masturbation, but that's hardly clinically feasible. Can you imagine a researcher running in after sex to collect semen samples? Talk about a buzzkill. 

Throughout the study, which was published in Evolutionary Psychological Science, each participant provided seven samples of ejaculate over the course of 15 days. Participants were asked to refrain from drinking alcohol and having sex 48 hours before each collection. Each man was left alone in a private room to watch the provided film and masturbate into a collection pot. 

Researchers found that men didn’t habituate – a decrease in response to a repeated stimulus – when watching six pornographic films with the same actress. Time taken to ejaculate ranged between four and 21 minutes overall. When the participants watched the seventh film with the new actress, the total number of motile sperm, the speed and amount of ejaculation increased.  

“Men produced higher quality ejaculates when exposed to novel, rather than familiar, women,” the researchers wrote in the study.

"This research adds to a rapidly growing body of work indicating that human sexual psychology and physiology includes adaptation to prevent or to more effectively participate in sperm competition," Professor Todd Shackelford, from the department of psychology at Oakland University, who was not involved in the study, tells IFLScience. 

And while we are yet to gain a complete understanding of how sperm competition evolved in humans, researchers suggest that male sexual behavior responds in a way consistent “with a history of sperm competition and extra-pair mating opportunities.” 
 
The sample size was quite small, but Leivers says this is often the case with intimate studies of human sexual behavior and biology are difficult to carry out and this kind of research is certainly not for everyone. 

"I think it would be interesting in the future to continue the research so that the novel woman used in this study then became the familiar woman," says Leivers. She wonders whether researchers would see a drop or plateau in sperm motility and ejaculate size until another novel woman was the introduced.

"This approach could rule out the possibility that the changes in the ejaculate that we see are indeed because the novel woman was in fact novel, and not because she was, for instance, more attractive than the familiar woman," Leivers explains. 

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