Top, Bottom, Vers, or Side? What the Science Says

Main Ideas and Findings

The Study and Its Scope

Dr. Rafael Herrero describes a survey on anal-sex roles among men who have sex with men (MSM). The survey received nearly 10,000 visits over four months. Of those, 8,755 respondents met the study’s criteria and answered its core questions.

Participants were ages 18–85. The 104-question survey explored sexual-role identity, behavior, and preference, as well as possible physical, psychological, and social influences.

Herrero says the sample was broader than those in studies limited to specific clinics, relationship statuses, or age groups. He also cautions that survey figures can be interpreted in different ways.

Identity, Behavior, and Preference Are Different

A key lesson is not to treat these concepts as interchangeable:

• Identity: How someone describes their role—for example, top, bottom, versatile, or side.
• Behavior: What someone actually does in sexual situations, which may differ from their identity.
• Preference: What someone would choose if circumstances were ideal.

The study divided penetrative identities into more specific groups, including exclusively or mostly top or bottom, and versatile. The guest and host use the familiar terms “top” and “bottom”; more formal terms for these roles are insertive and receptive.

How Respondents Described Their Roles

• Identity: About 40.8% identified as bottoms, 30.8% as versatile, and 24% as tops.
• Behavior: About 46% primarily behaved as bottoms, nearly 30% as tops, and 17.5% as versatile. Herrero suggests versatility may be less visible in practice because it can depend on the partner and situation.
• Sides: About 2.9% identified as sides—people who do not want anal penetration—while 5.7% reported behavior without penetration. These figures suggest the category is meaningful, though identity and behavior do not map exactly onto each other.
• Preference: The discussion suggests many respondents would prefer greater versatility or some receptive role. Herrero gives a figure of about 85.8% for those wanting to be versatile, receptive, or passive, and describes roughly 60% as wanting to be versatile. The conversation leaves some ambiguity about how these preference categories are grouped.

Among respondents who identified as sides, the share who said they would prefer to remain sides fell to about 1.6%. The host raises the possibility that stigma or difficulty finding partners may influence what sides say they want. The survey figures alone, however, do not establish why preferences differ.

How Important Penetration Was to Respondents

About 85.6% said anal penetration was at least somewhat important; around 13.6% said it was only slightly important or not important.

Bottoms placed greater importance on penetration than tops and versatile respondents. About 70% of bottoms rated it very or quite important, compared with about 57% of tops and versatile respondents. Only 8.3% of bottoms said penetration was not important at all, compared with about 14% of tops and versatile respondents.

Appearance Does Not Reliably Reveal Someone’s Role

Herrero’s findings do not support the idea that a person’s appearance can reliably indicate whether they are a top, bottom, versatile, or side. The practical takeaway is that you cannot know without asking.

Tops were somewhat more likely to be fit or muscular in the study. However, because bottoms were more numerous, there were still more fit and muscular bottoms overall than fit and muscular tops.

Herrero also reports that partner traits may affect role preferences. Muscularity and a masculine appearance were the strongest influences overall; for versatile respondents, attractive buttocks could be especially influential. The study considered traits including a partner’s musculature, height, age, penis size, and buttocks.

Physical Differences Reported in This Study

Herrero says his data found that gay men were, on average, about 1–2 cm taller than heterosexual men, and that gay men and other MSM reported larger penises on average. He presents these as findings from the study, not as a way to identify an individual or predict sexual role.

Within the study, average penis size increased across the groups from bottom to versatile to top, with a difference of about 1 cm between averages. Herrero stresses that individual variation is substantial and that averages do not describe every person.

He also reports a better-than-average BMI in the sample, while offering possible explanations rather than establishing a cause. Overall, the discussion emphasizes that statistical group differences are small or limited in what they can tell us about any one person.

Flexibility and the Role of Social Context

Herrero says all role categories show some flexibility, though tops appeared less flexible than other groups in his data.

The speakers suggest that physical demands, psychology, culture, religion, and upbringing might affect flexibility. These are offered as possible explanations, not proven causes.

The broader takeaway is that sexual roles are not necessarily fixed by anatomy or appearance; identity, behavior, preference, and context can differ.

Speakers and Sources Featured

• Dr. Joe Kort — Host of Smart Sex, Smart Love. He discusses the term “side,” which he says he coined in 2013.
• Dr. Rafael Herrero — Guest; gynecologist, medical sexologist, researcher, and sexology educator who presents findings from his survey.
• Herrero’s survey of 8,755 men who have sex with men — The primary research source discussed in the episode.