Women don't just like menwith muscles — they go for them.
Men who are more muscularthan average are much more likely to have short-term affairs and multiple sexpartners than their scrawnier peers, according to new UCLA research publishedin the August issue of the Personality and Social Psychology Bulletin.
"If you're trying to figureout why men — especially young men — spend so much time at the gym, here's youranswer," said David Frederick, lead author and a UCLA doctoral candidate inpsychology. "The stereotype is that men work out to compete with each other,but our research suggests that pumping iron is a way for men to enhance theirattractiveness to women."
The series of studies,conducted by
"A lot of mate-selectionresearch focuses on what men find attractive," Haseltonsaid. "This shows women are putting a premium on attractiveness. Women careabout muscularity when they choose sex partners."
Frederick and Haselton lead a team that photographed 99 maleundergraduates. A panel of independent judges rated the young men on anine-point scale, with "1" being much less muscular than average and "9" beingmuch more muscular than average. The researchers then asked the men about theirsexual histories.
When compared with theirless-muscular peers, young men who were more muscular than averagewere twice as likely to have had more than three sex partners in theirlives.
In another study, Frederickand Haselton asked 120 undergraduate males to ratetheir own physiques on the same scale and then asked them about their sexualhistories.
The self-identified muscularmen had not only had more sexual partners than their less burly peers, but theywere twice as likely to have had brief flings or one-night stands with women. Thedifference in the number of sexual partners reported by the men who were moremuscular than average was also notable: They reported having had an average offour partners, compared with an average of 1.5 partners for men who reportedaverage or below-average muscularity.
In a similar study, Frederickand Haselton asked 60 undergraduate males anadditional question: How many affairs had they had with women who already had aboyfriend at the time of the affair? Muscularity mattered here as well. Themore muscular individuals were twice as likely as their less well-built peersto have hooked up with someone else's sweetheart.
The researchers, who areassociated with UCLA's Center for Behavior, Evolution and Culture, say thattheir findings on muscularity are consistent with research findings on thesecondary sexual characteristics of other animals, such as the attention-gettingtail feathers of male peacocks.
"Everybody knowsthat testosterone is a hormone that promotes strength in men, but less well-knownis the fact that the hormone is also associated with poorer immune systemfunctioning,"
"Evolutionary scientists havelong maintained that exaggerated secondary sexual characteristics — such aslarge muscles in men — are cues to genes that increase the viability ofoffspring or their reproductive success," Haseltonsaid. "In an age when medical advancements play such a large role in thesurvival and health of children and so many people use contraceptives, it's notclear whether these genes continue to offer reproductive benefits. But womentoday are still attracted to muscular men, just as their ancestors would havebeen, because that's how we've evolved."
Interestingly, women in thestudy seemed to be on to muscular men. When presented with six standardizedsilhouettes of men ranging from brawny to slender, 141 undergraduate womenconsistently identified the most muscular ones as not only less likely tocommit but also more volatile and domineering. In the study, the women rated "toned"guys — the physical type two notches down from "brawny" — as the most sexuallyattractive.
"Moderate muscularitydemonstrates that men are in good condition, but they're not so overloaded withtestosterone that they are volatile, aggressive and dominant,"
Still, in a study byFrederick and Haselton of 82 college coeds, mostwomen reported that their short-term partners were more muscular than theirlong-term ones. They characterized their long-term — and presumably lessmuscular — partners as more trustworthy and romantic than their one-nightstands or brief affairs.
"This suggests that thesweet-guy approach works better for less muscular men,"