The men who populate Ritch C. Savin-Williams’s book Mostly Straight: Sexual Fluidity Among Men, released last month on Harvard University Press, are—honestly, truly—interested in women. They may lust for furtive, late-night sexual encounters with a “buddy” or find themselves intensely admiring a male porn star’s biceps, but this does not occlude their love for their wives and girlfriends, nor women in general.

“Mostly straight,” as a male sexual identity, hasn’t entered the public’s consciousness the way gay or bi identities have, though that seems to be changing. According to one trend forecasting agency, only 48 percent of Gen Z identifies as exclusively heterosexual, compared to 65 percent of millennials. And millennials, it bears mentioning, are no slouch when it comes to dismantling hard-line conceptions of sexuality; when an actor like Josh Hutcherson loudly declares himself to be “mostly straight” in the press, he goes a long way in dismantling stigma against sexual fluidity.

Hutcherson’s phrasing, as it happens, inspired the title of Savin-Williams’s book, in which he interviewed 40 mostly straight men to better understand their relationship to same-sex sexuality and how they parse their desires. To the eternal consternation of men who identify as gay, mostly straights aren’t usually interested in long-term same-sex relationships, Savin-Williams writes, but they’re also refreshingly shame-free about their desires, with many not only comfortable with gay culture but even “enchanted” by it.

Savin-Williams, who also works as the director of the Sex and Gender Lab at Cornell University, spoke with VICE about why gay men seem culturally obsessed with mostly straight guys, the need to embrace all the messy nuances of the Kinsey spectrum, and why you can’t assume every guy in the local gay choir is actually gay.

VICE: What drew you to study “mostly straight” men?

Ritch C. Savin-Williams: Usually, straight guys are just very boring, but when I started interviewing them using the same protocol I used with gay guys, it appeared that some had same-sex attractions—and that these men were incredibly complex. At first I sort of dismissed these guys, but then I interviewed the main character of my book, Dylan, who was a hockey goalie, and he was so convincing that I realized there was something going on there. I reviewed everything we knew about “Kinsey ones,” men who deviate just a bit from exclusively straight guys on the spectrum. It was almost as if their status as mostly straight encouraged them to look at their development and realize, “Oh my God, that was a boy crush I had.” Or “I did make out with that boy, and it was kind of fun. I liked it.”

Do you think they’re more comfortable with their mostly straight identity because they’re part of the post-millennial generation, which is by many accounts queer as hell?

Yes, but I should add that historically, across generations, you’ll find individuals saying they’re “mostly” heterosexual on the Kinsey scale. The difference is that today it can be an identity, not just an orientation. It’s this increasing acceptance of sexual diversity that’s allowed these men to accept these parts of themselves. Even if they go back to a totally straight lifestyle, a lot of them would say, well, you just never know—maybe, in the future, my wife and I will invite a guy into the bed.

And you theorize that as many as nine percent of the total male population could be “mostly straight.” How did you find those numbers?

That’s somewhat optimistic. We read every study we could find that assessed men via the Kinsey spectrum, and 8 to 9 percent was the largest we saw. This is from polling data or from the CDC or the National Institute of Mental Health, whom tend to use the Kinsey spectrum. Another very valuable source was the Add Health Data Set, which is a longitudinal study that began following a sample of adolescents in 1994.

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Were these men also interested in gay culture?

Yes, the men I spoke to were kind of enchanted by gay culture, and I don’t know that I’ve ever met an exclusively straight guy who was enchanted by gay culture. Maybe it was because they felt some identification. I got a sense from some of them that they would have liked to be gay—one helped his roommate come out, and another sang in a gay chorus. I think the other guys in the chorus probably thought he was closeted, but I checked his pupil dilation while he was looking at porn, and I can assure them—he is really, really attracted to women.

You have the receipts.

Yeah, you can’t fake your pupils.

Do you think we’ve overlooked the nuances of the Kinsey spectrum to create orientations like gay, bi, and straight?

Absolutely. We collapse the Kinsey spectrum into categories. We lump sexual minorities together, as if they’re all the same—like there’s no distinction between having a little bit of same-sex attraction and a whole lot of it.

Hasn’t this historically helped with political expediency? It’s easier to agitate for political change when you simplify and streamline identities, no?

Yeah, but it’s like saying all Asians or Latinos are the same. By grouping us, we too frequently buy into the straight world. They want these simple categories—black or white, Latino or Asian.

I also believe that sexologists fully recognize that women are on a spectrum, but they don’t really believe that guys are on a spectrum. I think they believe that if you’re a guy and you have just a little bit of same-sex attraction, you’re either a closet case or you’re just sort of a wayward progressive.

It was interesting that the gay men you interviewed saw mostly straight men as closet cases.

I think a lot of gay guys have the same feeling about bisexual guys—that they’re on their way. And I think it’s because a lot of gay guys have their “bisexual phase.” They think just because they had that, mostly straight or bi guys are going through that as well. Gays don’t really believe mostly straight men exist.

One reviewer said that the hype surrounding Call Me by Your Name reflects gay men’s obsession with straight men as a sexual conquest.

Clearly there are gay guys who are very attracted to masculinity. Just read Craigslist ads! When Dylan (the main character in my book) goes to gay bars, they’re always betting on when he’ll turn gay.

I do think mostly straight guys have this dilemma, which is that they’re going to be largely appealing to gay men. And many of them are masculine-looking. They can pass. That’s a tough one, and I don’t know, if this identity were to become more widespread, how gay guys would react to it.

Gay men may also want to preemptively reject mostly straight men so they don’t get hurt, right? It seems like many mostly straight guys are interested in a onetime encounter, not a real relationship.

I think the big thing is that these mostly straight men are really into women. They’re not going to give that up. But this identity may help them understand their romantic attachments even more than their sexual attractions. They’ve heard of straight guys having sex with other guys when they’re drunk or in a gang or in prison. The way guys get attached to each other, they think, Oh, it’s just a bromance. But some of these guys really feel something more than just a bromance—they feel the fluttering in their stomachs; they get really attached to other men. One of them told me, if I could just meet a woman and have the same attachment as I have with my three male friends, that’d be fantastic.

Interview has been edited for length and clarity.