Well ladies, it turns out having a lot of guy friends isn’t just good for drinking beer on Thursday nights and playing video games.
A new study from Oakland University, recently published in the Journal of Comparative Psychology, found that women with a lot of men in their life — like friends or co-workers — have more sex with their boyfriends compared with couples in which the female partner has fewer male influences.
Researchers came to this conclusion by studying 393 men in committed relationships, with the mean relationship being 35.9 months long. These men were asked to report on several issues including their partner’s attractiveness, how many male friends and co-workers they perceived their female partner to have, how attractive they think these other men find their partner, and how many times they had sex with their partner in the last week.
The men who reported their girlfriends as having a lot of male attention from social and professional circles—and who felt those other men found their partner attractive—were associated with having more sex with their girlfriends.
According to the researchers this is all thanks to a concept called sperm competition.
If you didn’t know already, male sperm is very competitive. In fact, if sperm from two different males ends up inside the same female, the little guys will actually fight each other to the death in order to fertilize first.
Apparently this biological desire to fight off other sperm translates to dating world as a psychological desire to fight off other men (known as “sperm competition psychology”) by also using sperm…as in, loads of it.
For instance, as the study states, if a man is watching porn he will become more aroused and will release more sperm (into a tissue, of course) when he watches two men having sex with one woman rather than two women having sex with one man. This is because he senses other “sex rivals” in the vicinity — even though these rivals are literally on his screen and not present in real life — his competitive drive goes into overload and his body produces as much sperm as physically possible.
For this study, the same rang true when boyfriends perceived their female partners as having a lot of other men in their lives, a.k.a. “sex rivals.”
“A lot of work shows that men are sexually aroused by their partner when they estimate a greater likelihood of partner infidelity,” Michael Pham, lead author on the study, explained to Fusion in an email. “This does not mean that men want their partner to cheat on them. Rather, this means that if they estimate a greater likelihood of their partner’s infidelity, then they may (subconsciously) want to have sex with her to enter into sperm competition.”
Pham points out that this type of jealous behavior, as the result of a biological urge for sperm competition, isn’t necessarily a bad thing.
“This is human nature,” he tells Fusion. “We need to be reminded that our partner is valuable to us and desirable to others. This makes us keep working at maintaining relationship satisfaction.” Adding, “Finding that right balance of inducing your partner’s jealousy will optimize a couple’s sex life.”
Of course in today’s world of condoms and contraceptives the physiological response is still there, but the sperm packs less of a punch.
Taryn Hillin is Fusion's love and sex writer, with a large focus on the science of relationships. She also loves dogs, Bourbon barrel-aged beers and popcorn — not necessarily in that order.