London - Men who have sex with new partners are more likely to reach orgasm faster and will produce better quality sperm, scientists believe.
The study by US researchers found that when men have encounters with unfamiliar women, their sperm shows improved quantity, movement and structure.
In the study, 21 heterosexual men aged between 18 and 23 were shown seven sexually explicit film clips involving a man and a woman.
The first six clips featured the same couple, but in the seventh, the woman differed distinctly. The men each provided seven samples over the course of 15 days.
After analysis, the results showed that the men produced higher quality sperm when the new woman was introduced, as well as ejaculating more quickly.
Experts hope that the findings will pave the way for better treatments for male infertility.
Writing in the journal Evolutionary Psychological Science, the authors said: “In our study, men produced higher quality ejaculates when exposed to novel, rather than familiar women. Additionally, men ejaculated more quickly when viewing a new woman after being exposed to the same woman repeatedly.
“Our findings are the first to demonstrate that men’s ejaculate behaviour and composition change in response to novel female stimulus.”
The research team, from the College of Wooster in Ohio, said that the sperm change may show that men “preferentially invest more” into new sexual situations with unfamiliar partners – so it is more likely that they conceive through the encounter. The experts also suggested that men orgasm more quickly with a new woman in order to avoid being detected with a partner that is not their own.
This is because of male competition, as well as the evolutionary desire to secure an heir.
They wrote: “A decrease in the time to ejaculation may decrease the likelihood of an extra-pair copulation being detected.”
The results could have an impact on fertility treatments, as male infertility could be being under-diagnosed, they warned.
This is because sperm samples are often collected using images depicting women other than the man’s partner.
Daily Mail