New research suggests women turn down offers of casual sex for one good reason: They suspect — with some reason — they won’t enjoy it.

Would you have casual sex with a stranger? How about a close platonic friend?

How about with Johnny Depp?

Getting more interested, ladies? If so, you’re adding to the evidence that some widely accepted beliefs regarding men, women and short-term sexual encounters may be significantly off-base.

In a newly published paper describing a series of studies, University of Michigan psychologist Terri Conley asserts that “when women are presented with proposers who are equivalent in terms of safety and sexual prowess, they will be equally likely as men to engage in casual sex.”

Her research suggests women, like men, are motivated by pleasure-seeking when they enter the sexual arena. It’s just that women are less likely to be satisfied by a short-term encounter, and they know it.

Writing in the Journal of Personality and Social Psychology, Conley describes a series of experiments that refine the results of a seminal 1989 study widely cited in articles and textbooks. That study, by psychologists Russell Clark and Elaine Hatfield, found that when a female college student introduced herself to a male colleague and asked if he wanted to have sex with her, 69 to 75 percent of the guys said yes. When the genders were reversed, not a single woman was interested.

That huge difference has largely been explained in terms of Sexual Strategies Theory, an evolutionary approach that focuses on the desire, conscious or unconscious, to pass one’s genes to the next generation. If that’s our driving impulse, women need to be choosy about their sexual partners; they’re looking for men who are likely to stick around and provide support during their child-rearing years. Men, on the other hand, have an evolutionary incentive to spread their seed as widely as possible.

Although Conley also takes an evolutionary approach, her perspective is significantly different from that much-discussed thesis. She points to a relatively new approach called Pleasure Theory. It asserts “the pursuit of pleasure is the central force that motivates sexual behavior,” and that reproduction is a byproduct of this effort.

“If humans are having pleasurable encounters, enough instances of vaginal intercourse will occur to ensure the survival of the species,” she notes.

In other words, our motivation may be simpler than the first generation of evolutionary psychologists believed. Girls — and boys — just want to have fun, and biology takes care of the rest.

So why did the young men and women in the 1989 study — and in a repeat of that experiment that Conley conducted — react so differently to the offer of casual sex? After conducting a series of follow-up experiments, in which she tweaked Clark and Hatfield's sexual-invitation scenario in different ways, she came up with an answer sports-conscious men should be able to easily grasp: The playing field isn't level.

Men, after all, can almost be guaranteed a pleasurable sexual encounter if they’re with someone they find attractive. But Conley points to new, yet-to-be published research by sociologist Elizabeth Armstrong which finds “women orgasm only 35 percent as often as men in first-time sexual encounters.”

“Women’s perception that their heterosexual casual sex partners will be unlikely to give them pleasure is not unwarranted,” Conley states.

This lack of confidence in men as pleasure-givers was indirectly supported by another of Conley’s experiments, which focused on bisexual women. They were “significantly more likely to accept an offer (of a one-night stand) from a woman than from a man,” she reports.

This brings us back to Johnny Depp. In an attempt to learn if gender differences toward casual sex can be eliminated, Conley conducted yet another variation on the basic “Will you go to bed with me?” experiment. Only in this case, the scenario featured one very attractive and one unattractive suitor: Depp and Donald Trump for women, Angelina Jolie and Roseanne Barr for men.

The result: Women were just as likely as men to agree to have sex with the attractive celebrity. They were also “about equally likely” to reject the offer from the unattractive but famous individual.

This suggests a problem with the aforementioned Sexual Strategies Theory. If women were attracted at some deep level to men with the resources to care for them and their prospective children, The Donald would be a catch.

It’s worth noting that gender-specific biology, or at least psychology, does play into this equation. Conley notes that women tend to be more concerned about sexual assault, a fear that makes casual encounters more risky. It’s entirely possible that women, on average, get less pleasure out of casual sexual relations because they are more relaxed, and thus more receptive, when they are with partners they know and trust.

Still, it’s fascinating that when you remove that variable and give women the option of a casual encounter that is likely to be both safe and pleasurable, they are just as receptive as men. This research, Conley concludes, “suggests that women are more similar to men in their reactions to casual sex than would have initially been expected.”

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