Men who whine about wearing condoms — villains of sex ed videos, defiers of Centers for Disease Control and Prevention reports and common sense — might protest even louder if they think their partners are hot.

When faced with the proposition of casually sleeping with a pretty woman, men are more eager to forgo condoms, according to a new scientific survey, than if they think their fling is less attractive.

Researchers at the University of Southampton and the University of Bristol asked heterosexual men to report their desire to have unprotected sex with 20 women, based on photographs of the women’s faces. The scientists discovered men were much less apt to wear a condom if they believed a hypothetical partner had a prettier face, as the researchers wrote recently in the British Medical Journal Open. The study was small, just 51 subjects, but it adds to a growing body of evidence that both men and women want to relax safe-sex standards for good-looking partners.

“Men are more willing to have condomless sex with attractive women,” wrote lead author and University of Southampton public health researcher Anastasia Eleftheriou, in an email to The Washington Post. That holds true “even though they might believe that those women are more likely” to have a sexually transmitted disease, she said.

The male subjects were not hugely varied in their demographics: The 51 heterosexual men who made up the survey ranged in age from 19 to 61 years old, and all spoke English. Most men had lost their virginity at an average age of 18; the youngest was 13 and the oldest, 30. But there was quite a bit of variance in reported number of sexual partners — the average was 10, though four responders had never had sexual intercourse and one man said he had had sex with 60 women.

While looking at a black-and-white portrait of a woman’s face, each man used a sliding scale, from of 0 to 100, to rate a) the woman’s attractiveness b) how likely he would be to sleep with her, if he were single c) how likely he would be to use a condom d) how many men like him, out a group of 100, would have unprotected sex with the woman and e) the odds he thought this woman had a sexually transmitted disease.

Not surprisingly, the closer a man rated a woman to 100, the higher his willingness was to have sex with her. But the study subjects were split on whether or not the attractive women were more likely to have a sexually transmitted disease.

Previous studies on perceived health and looks reflect this division, too. Some researchers have found that men view attractive women as more promiscuous, and therefore more likely to have been exposed to sexually transmitted disease; others indicate humans broadly link good looks to good health. (One evolutionary psychology theory argues that facial symmetry, a significant factor in attractiveness, indicates a high resistance to parasites. Because we want our mates to be parasite-free, symmetry becomes pretty.)

Humans make a lot of assumptions about attractiveness, and many of them do not quite hit the mark. (Beauty is not skin deep, for instance, as bone structure has a dramatic influence on what we find attractive.) In this study, the scientists reported a few surprising incongruities: Some men who rated the women at high risks for sexually transmitted diseases — the men who believed many other men would have unprotected sex with a woman — also rated themselves as likely to have unprotected sex. In other words, even though the men thought having sex with a particular woman was apt to be risky, they would not take any additional measures to protect themselves.

To explain the apparent incongruity, Eleftheriou’s co-author Roger Ingham, a sexual health expert at the University of Southampton, offered two possible reasons. First, it is lack of contraception as an evolutionary holdover, he wrote to The Washington Post in an email.  That is, “men want to reproduce with women they find to be more attractive,” he said. Or it could be that young men attach high status to having sex with attractive women, “and so are willing to take more risk to acquire this status.” Or, perhaps, it is a mixture of both motivations.

When asked if the reverse would seem to hold true — are men more likely to use condoms with women whom they find less desirable? — Eleftheriou replied, “Yes. We found a strong correlation between the two variables that works both ways.”

Eleftheriou and Ingham want to use this information to create better sex education. Ingham points out that sex ed traditionally assumes people are rational actors, but studies like this one show that is not the case when a man thinks about having sex with an attractive woman. Eleftheriou is exploring ways to create computer games to promote sexual health, targeted at young populations.

As mentioned, the sample size was small — though Eleftheriou pointed out it could still detect trends. In the paper, the scientists note that the survey was taken in the presence of a female researcher, which previous studies have shown to affect male responses. Likewise, this study did not take into account alcohol or arousal, both factors when making decisions about condoms. And, finally, Ingham acknowledged that the study was limited to heterosexual males. “It would indeed be of great interest to repeat the study using men who have sex with men,” he said, “to explore if similar patterns of results are obtained.”

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