New neuroimaging research has found that gay, bisexual, and straight men have different brain responses to sexual stimuli.

The fMRI study of 26 heterosexual, 28 bisexual, and 25 homosexual men found that sexual orientation was associated with distinct patterns of brain activation. In particular, the researchers uncovered that heterosexual and homosexual men showed different neural responses to erotic stimuli in the ventral striatum, an area of the brain associated with erotic desire.

The erotic stimuli consisted of pictures of nude men, nude women, and lesbian or gay couples engaged in sexual contact. Twelve video clips of men and women masturbating were also used.

As expected, heterosexual men showed greater ventral striatum responses to erotic stimuli of women and homosexual men showed greater ventral striatum responses to erotic stimuli of men, while bisexual men displayed a distinctly bisexual neural response.

The study was published February 1, 2017, in Scientific Reports.

PsyPost interviewed the study’s corresponding author, Adam Safron of Northwestern University. Read his responses below:

PsyPost: Why were you interested in this topic?

Safron: Our lab has studied human sexuality for many years, and we were interested to see what brain scanning technology might tell us about sexual orientation. We wanted to see whether straight, bisexual, and gay men would show patterns of brain activity that corresponded to their sexual orientations. We were particularly interested in an area of the brain called the ventral striatum, which is a highly dopamine-sensitive part of the brain involved in desire.

What should the average person take away from your study?

We found that desire-related brain activity corresponded to men’s self-stated orientations. Heterosexual men responded more strongly to images of women, gay men responded more strongly to images of men, and bisexual men did not show strongly different responses to erotic images of women and men. These brain activity patterns were consistent with what participants told us they liked and disliked, as well as with previously measured genital arousal patterns. While this may seem obvious, in science you don’t take anything for granted, particularly when it comes to something as complex (and emotionally charged) as human sexuality. Also, some people had doubted whether bisexual men actually had bisexual patterns of arousal and reward. This study suggests that bisexual men are indeed different from gay and straight men in their capacity to respond to both sexes.

Are there any major caveats? What questions still need to be addressed?

It would be interesting to replicate this research with narrative or other kinds of stimuli in the future. We’d also like to find out more about how people’s sexual desires change over time, and whether those vary based on gender and sexual orientation. Also, future research into sexual orientation could look into not just desire, but also aversion. For example, do straight and gay men differ in their degree of aversion toward their non-preferred sex? Do bi men potentially have less aversion toward either sex that leads them to be able to develop arousal toward both sexes? We don’t yet know, and answers to questions like these could shed light on what drives human sexual behavior.

Is there anything else you would like to add?

We are currently finishing research looking at the neural responses of straight, bisexual, and lesbian women, as well as research comparing men and women. Those papers will likely be published in the coming year.

The study, “Neural Correlates of Sexual Orientation in Heterosexual, Bisexual, and Homosexual Men“, was also co-authored by David Sylva, Victoria Klimaj, A. M. Rosenthal, Meng Li, Martin Walter and J. Michael Bailey.