According to a new study, men who have sex with new partners will produce better quality sperm.
During encounters with unfamiliar women, guys are also more likely to reach orgasm faster, say scientists, surprising no-one.
Researchers at The College of Wooster in Ohio hope their findings will help to improve treatments for fertility.
According to scientists, quantity, movement and structure all aid sperm health. And, writing in the journal ‘Evolutionary Psychological Science’, researchers said they believe these traits may change for the better with new sexual partners.
The team said:
Our findings are the first to demonstrate that men’s ejaculate behaviour and composition change in response to novel female stimulus.
In simple terms, that means lads get more excited when they see a new woman, basically.
The study involved 21 participants, all heterosexual men aged between 18 and 23 years old, who each provided seven samples of you-know-what over the course of 15 days while watching clips from porn movies.
Six film clips featured the same man and woman but differed in the sexual acts performed, while a seventh clip had the same man but a new female with very different features to the other woman, which resulted in some incredible sperm, apparently.
The authors added:
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 study’s authors said one reason for producing “better” sperm with a new partner is down to sperm competition and an evolutionary desire to secure an heir.
The findings could have a significant impact on fertility treatments, as researchers suggest that male infertility could be being under-diagnosed because “ejaculate samples used to test for infertility are often collected with the use of images depicting women other than the man’s partner”.