No man is an island, and it turns out neither is his penis. New research suggests that size does matter (sorry, guys), but the penis is only one (sometimes) small contributor to manly allure. A man's overall attractiveness to a woman, researchers have found, depends in part on the trio of height, body shape, and penis size.
Although the assault of penis pill spam in your inbox might make you think that "bigger is better," scientific research has returned mixed results. Some findings say that women prefer longer penises, others say they like wider ones, and still others report that size doesn't matter at all.
Most of these studies had either asked women directly about their preferences or had them rate the attractiveness of different male figures that varied only in penis length. The penis doesn't exist in a vacuum, though, and biologists led by Brian Mautz, who was then at the Australian National University in Acton, wondered how penis size interacts with other body traits that are usually considered attractive or manly.
Using data from a large study of Italian men, the researchers created 343 computer-generated male figures that varied in penis size, as well as in height and shoulder-to-hip ratio—traits that other research has linked to attractiveness and reproductive success. Mautz and colleagues turned the figures into short video clips and projected them, life-sized, onto a wall for viewing by 105 women. Each woman watched a random set of 53 figures and rated their attractiveness as potential sexual partners on a scale of 1 to 7.
"The first thing we found was that penis size influences male attractiveness," Mautz says. "There's a couple of caveats to that, and the first is that the relationship isn't a straight line." Rather than the attractiveness rating consistently improving with each jump in penis size, the team found what Mautz calls "an odd kink in the middle." Attractiveness increased quickly until flaccid penis length reached 7.6 centimeters (about 3 inches) and then began to slow down, the team reports online today in the Proceedings of the National Academy of Sciences.
The reason, Mautz says, is that penis size isn't the only thing that matters. It interacts with other traits, and its effect depends on whether those other traits are already attractive to begin with. If one of the model men was tall and had a masculine, V-shaped torso with broad shoulders and narrower hips, for example, he was considered more attractive than his shorter, stockier counterparts, regardless of penis size.
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An increase in penis size was also a bigger benefit to attractiveness, and a smaller penis was less of a detriment, to the taller, fitter figures than it was to shorter or potato-shaped ones. For example, a model that was 185 cm tall (about 6 ft) with a 7-cm-long (about 3-in-long) penis got an average score for attractiveness. To get that same score, a model that was 170 cm (about 5'6") needed a penis of about 11 cm (about 4.5 in) in length. Boost the taller guy's penis by just about centimeter, and the shorter guy needs double that to keep up and get the same attractiveness score. After that, the shorter male pretty much can't continue to compete. To really reap the benefits of a big penis, a guy needs to be attractive in the first place, Mautz says. If he isn't, even the biggest penis in the world won't do him that much good.
So have women been responsible for the male penis getting larger—at least over the course of evolution? That's a distinct possibility, the researchers say. Women may have selected for larger penises because they're linked to higher rates of female orgasm and sexual satisfaction, which may explain why the human penis is proportionally larger than those of our evolutionary cousins.
That size matters, and that it matters in the context of other traits, makes sense, because proportionate features are attractive, says Adam Jones, a biologist who studies sexual selection and mate choice at Texas A&M University in College Station and who was not involved in the work. But he cautions that projections on a wall are no substitute for real life. Just because a woman prefers a man with a large penis doesn't mean that she's going to find one. Outside the lab, there's greater variation and more traits to consider, so penis size might not be as important. That's good, Jones says, because hurdles like competition with other women and her own perceived attractiveness could place her with a man who comes up a little short.