Social scientists have a way of digging into just about every corner of social and sexual life. And Ryan Scoats, a researcher at Birmingham City University, has a very specific niche.

Years ago, Scoats and his then-girlfriend developed a friends-with-benefits-type relationship with another woman. Curious, Scoats went looking for academic studies about him and his ex-partner's new relationship coupling. He didn't find much, and what research did exist about threesomes often lumped them in with polyamory and swinging. But this didn't reflect his own experiences—he wasn't in an open relationship and didn't consider himself a swinger.

Wanting to know more about threesomes in their own right, he decided to conduct research on the subject himself. This led to a PhD about threesomes among two men and one woman (MMF), and a book on the same subject, to be published in 2018.

Why are threesomes worth studying? For one thing, they offer a window on attitudes toward gender roles and sexuality. "For women, for the longest time, there's been almost an inherent expectation of their inherent bisexuality or gender fluidity," Scoats notes. In some ways, in Western countries, women have more space to experiment with sexual orientation.

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Still, fewer women than men have had threesomes. According to one Canadian study published earlier this year, eight percent of women and 24 percent of men reported having had a mixed-gender threesome. This research also shows that participants were also kind of lazy about arranging threesomes—unless they were men. "It is likely," authors Ashley E. Thompson and E. Sandra Byers note, "that any increase in [mixed-gender threesome] experience among heterosexuals will be driven by men rather than by women."

This is also suggested by the usage stats for the dating app 3Somer. According to co-founder John Martinuk, who describes 3Somer as "the largest threesome dating app," the site has about 450,000 users. At 47 percent, men make up the largest group of 3Somer users. Female–male couples are 42 percent, while women are a paltry nine percent.

One reason for the difference between female and male interest in threesomes is that pop culture has traditionally pitched threesomes toward a male gaze. Researchers including Breanne Fahs and activists including Shiri Eisner have written of how TV and porn cultivate an expectation of women's "performative bisexuality," involving men as spectators and participants. And while the idea of being with two women is often exciting for a man, Scoats' research with women suggests that many are initially intimidated by the idea of a threesome with two men—but this is only if the expectation is that the two men won't touch. If all three are interacting sexually, women are more turned on.

As 26-year-old Isa, one of his survey participants, memorably puts it, "If there is no homo, there is no trio. I find it really annoying if they are reluctant to touch each other. I mean, they like it when I make out with someone, and I like it when they make out with someone." Kirsty, also 26, agrees: "If you're going to have a threesome, then it should be about all three of you… I would feel less apprehensive if [the men] were going to enjoy each other as well.'"

One of the major findings from Scoats' team is that the unwritten rules around permissible sexual activity are loosening for straight guys in the UK and North America, where much of this kind of research has been conducted. Scoats has documented a rapid increase in the acceptability of MMF threesomes, and not just the stereotypical straight male fantasy of the FFM encounter.

"In the past it would have been more stigmatized for men to have MMF threesomes," Scoats says. But among the young men he's interviewed, "they did seem comfortable telling at least their friends that they'd had an MMF threesome. I think because of the reduction of homophobia in general within society, this allows men to have these kinds of threesomes with no fear about what others are going to think of them for it."

Admittedly, Scoats' findings have been limited in scope to middle-class white college students. "We have predominantly found it among younger white British guys," he says of the greater open-mindedness when it comes to straight men's sexual boundaries, "but... there's also some research from the UK [of this happening with] of people from lower socioeconomic classes; there is some research starting to come out with people of color."

Photo by Guille Faingold via Stocksy

Straight men are more open-minded, but only up to a point. Plenty of the guys Scoats interviewed had had MMF threesomes without much interaction between the two men. The experience was less about sleeping with another guy than about bonding with a male friend. For instance, in Scoats et al.'s amazingly titled research paper "'I don't mind watching him cum,'" an interviewee named Brent says, "You get to 'high five' your mate over her back and that's about it really."

This is a pretty common attitude. "Men are more likely to have an MMF threesome if it's with someone that they know well, with someone that's a good friend," Scoats says. "If it's not a good friend, it reduces the chances of that happening."

In fact, much of the increasing male tolerance of mixed-gender threesomes seems to be limited to the MFM variety, where the two men don't touch each other, rather than MMF, where it's all hands on deck. (The letter in the center corresponds to the person in the middle of the sex sandwich, so to speak.) As one Reddit user on a thread about threesomes notes: "I don't want this dude touching me even if it's by accident."

According to Scoats, these attitudes are perpetuated by TV shows and films that treat mixed-gender group sex as hot, but not if the men accidentally touch each other. (The 2011 film A Good Old Fashioned Orgy demonstrates this amply.) Scoats thinks that teen drama Skins is one exception, but in general, "TV and pop culture has yet to catch up entirely with men sort of doing things together. It's very much a comedy trope."

So if you're a straight woman and your boyfriend is interested in arranging a threesome, tell him to consider simultaneous sex with a man and a woman. At the very least, it would set him apart from the pack.