Even today, bisexual people face a torrent of discrimination, from stereotypes about being promiscuous to exclusion from both the LGBT and straight communities. For bisexual men in particular, they battle constant assumptions that they’re sexually confused gay men loitering in the closet—but a wave of new sexological research suggests otherwise.

One study, out of Northwestern University, looked at something called “transitional bisexuality” in gay-identified men. The term transitionally bisexual refers to gay men who once identified as bi as part of their coming out process. But the study also found a distinct subset of gay men who prefer having sex with men, but also find women sexually appealing.

The researchers recruited their participants through announcements on Facebook and Grindr (basically Tinder for gay men). Study participants were at least 18 years old but younger than 50 to ensure that they could experience a full erection when they came in to the lab (more on this in a second).

The study consisted of an online survey, including questions about their current and past sexual feelings, identity and behavior, whether they had ever identified as bisexual (and if so, why), a Kinsey scale to assess sexual attraction and a phallometric test to assess sexual arousal.

As a refresher for Hard Science readers, the Kinsey Scale is a seven-point scale evaluating sexual orientation, ranging from zero (“exclusively heterosexual”) to six (“exclusively homosexual”). If you’re a zero (like yours truly), you only feel sexual attraction toward people who are of the opposite sex. If you’re a six, you only ever experience attraction toward same-sex individuals.

A subset of gay-identified men do indeed find women sexually attractive and sexually arousing.

Kinsey categories two to four typically represent bisexuality, and Kinsey ones and fives—two oft-overlooked groups—represent “mostly heterosexual” and “mostly homosexual,” respectively. As you’ll see, male Kinsey fives are men who are predominantly gay but also, to some extent, sexually attracted to women.

As for the laboratory part of the study, penile plethysmography (also known as phallometric testing) is considered the gold standard when it comes to assessing sexual arousal in men. It is much more accurate than relying on a person’s self-report, since people tend to answer in a socially desirable way when asked about their sexual fantasies and behaviors. The test involves measuring the volume of blood in a man’s penis (or measuring around its circumference) while he is looking at porn and listening to accompanying sexytime sounds or stories.

A total of 58 men completed the entire survey and 36 of them also agreed to undergo phallometry. (If you want an idea of how tricky it is to do sexual orientation and sexual arousal research, consider the fact that 22 men dropped out after finishing the survey, presumably because they didn’t want to complete this part.)

The final sample consisted of 20 Kinsey fives (“mostly homosexual”) and 38 Kinsey sixes (“exclusively homosexual”). Twenty-eight men—almost half of the sample—said they had identified as bisexual in the past; of them, 61 percent reported having had sex with a woman compared with only 7 percent of gay men who had never identified as bisexual.

Those who had once identified as bisexual didn’t report greater sexual attraction to women, nor did they show greater sexual arousal to pornography depicting women, compared with never-bisexual gay men. This spoke to the reality that some guys do identify as bi for reasons other than being sexually attracted to both sexes.

We get a clearer picture as to why from the questionnaire data. About one in five men (21 percent) said they identified as bisexual because they did feel sexual attraction to both sexes, and a similar number (18 percent) said they masturbated thinking of both sexes. At the same time, 61 percent said it was easier to think of themselves as bisexual than fully gay, 68 percent said they thought that other people would be more likely to accept them as bisexual than gay and 21 percent said they wanted a future that included a wife and kids. (Some participants gave multiple reasons, which is why the percentages don’t add up to 100.)

When asked whether, at the time of identifying as bi, they truly believed that they felt that way, 46 percent of the 28 “previously bi” guys said “no.” When asked whether, today, they believed they were bisexual back then, 82 percent said “no.” So, this offered further evidence that for some men who identify as bisexual, and particularly gay men who were transitionally bisexual, the label does represent an in-between stage while coming out, despite never experiencing sexual interest in women.

But this isn’t to say that male bisexuality doesn’t exist; the researchers also found that a subset of gay-identified men do indeed find women sexually attractive and sexually arousing. Recent research in neuroscience and endocrinology similarly offer support for the notion that some men are sexually interested in both sexes.

Sliding down to the other end of the Kinsey scale, we are also seeing a growing number of men who are attracted to both sexes and would be considered Kinsey ones (“mostly heterosexual”). These guys prefer to date only women, but enjoy having sex with men. Similar to how Kinsey fives are more turned on by women than Kinsey sixes, “mostly heterosexual” Kinsey ones are more turned on by men than “completely heterosexual” Kinsey zeros.

If you’re wondering about bisexuality in women, it’s important that I mention how it’s conceptualized differently from bisexuality in men, since male and female sexual systems operate in dissimilar ways. Men have high sexual concordance, which means when they feel sexual desire, they’re also turned on down below. For women, however, sexual concordance is low, and it isn’t unusual for a woman to be physiologically turned on by both men and women when she isn’t necessarily attracted to both.

This goes to show that there are many different ways to be bisexual, and like many things in sexology, what may look like the same thing on the surface isn’t necessarily being driven by the same factors or motivations. One of the most exciting things about sexual orientation research is that we are constantly being exposed to new ways of thinking about human sexuality while simultaneously being challenged about what we thought we knew.

Debra W. Soh is a Toronto-based sex writer with a PhD in sexual neuroscience from York University. She has written for Harper’s, Scientific American, The Wall Street Journal, The Los Angeles Times, The Globe and Mail and many others. She tweets @DrDebraSoh.