While walking through a park in Budapest a few weeks ago, I spied a very strange sight. In that fleeting moment between sensation and perception, when images settle on the retina but aren’t yet processed in a form fully accessible to conscious awareness, what I saw was a multicolored, gyrating mass of vaguely human substance, squirming and twisting on a park bench in animalistic fervor. My brain, unfortunately, was soon able to peel apart what I was actually observing, which was a particularly corpulent young woman devouring a young man half her size in what can only be described as a feast of open-mouthed, public lovemaking. The expression, “get a room,” seemed wholly inadequate for this carnal scene. “Get a porn studio” was more like it.

My partner, Juan, and I witnessed many other public displays of “affection” like this one during our stay in Budapest, which was curious enough from a cross-cultural perspective and a bit counterintuitive for such a socially conservative country like Hungary. It put me in an ethnographic state of mind. Suddenly I became acutely aware of the many American and British tourists who—if not quite as passionate as these lustful Magyars—were similarly expressing their attachments to their partners in, say, an arm casually draped around the shoulder, a hand held or a possessive grip on the waist. And that’s when the sad truth struck me: with the exception perhaps of just a handful of places in the world (and even those are questionable), gay couples are not free to participate in this most basic, mindless and normal exhibition of romantic behavior. In both the UK and the US, for example, I’ve got to first scout out who’s in our immediate vicinity before daring to even brush my pinky finger against Juan’s hand as we’re walking side-by-side. Compared to the issue of gay marriage, gaining equality in the “right” to display such innocent feelings of affection for one’s same-sex partner is an even greater hurdle for gay rights advocates—and, in many ways, it’s an even more important one. This is because recent findings indicate that changing negative attitudes toward gays begins not with education, per se, but instead with exposing people more regularly to same-sex romantic behavior.

Now, I know what you’re thinking. Nobody is stopping gay couples from holding hands in public, or from kissing and hugging, for that matter. In most of the world, it’s not illegal to do so, after all. But the problem here isn’t a legal one. It’s a psychological one. Not only do gay couples wish to avoid being pummeled by the occasional homophobic thugs who can be lurking anywhere or being subjected to epithets spit at them by simpleminded onlookers. More simply, we’re just wary of making those around us uncomfortable. And what makes the situation complicated is the fact that, although many people hold the explicit belief that it’s okay for gay people to be affectionate with one another in public (that is to say, if you were to ask them whether it’s okay for gay people to kiss in public, they’d say of course it is), the same people nevertheless hold implicit negative attitudes on the subject. At least, that’s what Harvard University psychologist Yoel Inbar and his colleagues reported in a recent study in the journal Emotion.

In one experiment, the researchers randomly assigned 44 undergraduate students from the University of California, Irvine, to one of two different conditions. Half of the participants were asked to read a brief story about the director of a risqué music video which turned out to have the side-effect of encouraging gay men to French–kiss in public. (Think Katy Perry’s homoerotic “I Kissed a Girl” but, for this study, a male-on-male “I Kissed a Boy” equivalent.) The remaining participants read the same story, yet in this other version the video was said to have caused straight couples to French–kiss in public rather than gay men. It was stressed to participants in both conditions that the director knew the video was likely to induce public French–kissing but this was not his primary goal in making the video.

The participants were then asked the following questions: (1) Did the director intentionally encourage homosexual men [or straight couples] to French–kiss in public? (2) Is there anything wrong with homosexual men [or straight couples] French–kissing in public? (3) Was it wrong of the director to make a video that he knew would encourage homosexual men [or straight couples] to French–kiss in public? The second two questions in this list, the investigators reasoned, tapped into the participants’ explicit beliefs about the “rightness” or “wrongness” of French–kissing in public. And as predicted, these mostly college-aged participants agreed that there’s nothing wrong with either straight or gay couples displaying this type of affection in public, nor, for that matter, was it wrong for the director to encourage such behavior in either case. Intriguingly, however, in response to the first question, participants viewed the director’s actions as being more intentional when he encouraged gays to kiss in public than straights.

This peculiar finding is interpreted in relation to the well-documented “Knobe Effect,” a phenomenon first discovered by Yale philosopher Joshua Knobe whereby people are more inclined to say that a behavior was performed intentionally when they regard that behavior as being morally wrong. (In his original work in this area, Knobe asked people to suppose that the CEO of a corporation is presented with a proposal that would make the company a lot of money but, as a side effect, either “harm” or “help” the environment. In response to this scenario, participants who read the harm version of the story reasoned that the CEO harmed the environment intentionally, whereas those in the help condition said it was only accidental that he helped the environment.) To Inbar and his coauthors, this incongruous finding regarding the director’s intentions therefore reflects a visceral, intuitive and largely unconscious moral judging of homosexuality by otherwise open- and fair-minded individuals.

But what makes the authors’ position even more compelling is the finding that participants who were easily disgusted (as measured by the Disgust Sensitivity Scale, which assesses individual differences in aversion to things such as feces, rotting meat, bodily secretions, blood, gore and corpses) were especially likely to see the director’s actions as intentional—but only in the gay-kissing condition. In other words, people who have a weaker stomach in general are more prone to find expressions of male-male sexual behavior morally wrong. However, because these implicit (often unconscious) moral judgments are often in conflict with social prescriptions of fairness and equality for gay couples, such individuals are usually completely unaware of their own prejudiced attitudes.

The specific link between disgust sensitivity and intuitive attitudes toward gays, however, isn’t entirely understood at present. That said, Inbar and his colleagues offer a perfectly reasonable evolutionary interpretation:

Individuals belonging to unfamiliar groups, especially those who engaged in unusual practices regarding food, cleanliness and sex, posed a higher risk of carrying novel (and therefore particularly dangerous) infectious agents. Perceiving such individuals would thus activate the behavioral immune system and cause avoidance behavior and the accompanying emotion of disgust…. This hypervigilance may be especially acute in those individuals who are especially sensitive to disgust, the emotion that drives the behavioral avoidance system. Because gay people almost by definition engage in “unusual” sexual behavior, one would expect more negative reactions to this outgroup on the part of those who are particularly disgust sensitive.

It may not be entirely apparent from reading these findings, but all of this is actually very good news for gay people. Studies have shown that people can be habituated to stimuli that trigger disgust over time (for example, University of Pennsylvania psychologist Paul Rozin followed first-year medical students enrolled in a gross anatomy course and found that disgust levels toward dead bodies waned significantly over the course of the semester). The key to gay people feeling comfortable expressing their affection for one another in public places, therefore, is simply to engage in such behavior more routinely.

So, hold your partner’s hand! Kiss him (or her)! We’ve got to put our love in people’s faces, not confine it to “the privacy of our own bedrooms.” That tradition of secrecy is precisely the problem. As long as we remain out of sight, we remain foreign—and thus likely to trigger disgust in the minds of those prone to hypervigilance.

(Please note, if there’s even a modest spike in the number of gay couples French–kissing in public over the next few days, you can hold me personally accountable for that. I did it intentionally.)

In this column presented by Scientific American Mind magazine, research psychologist Jesse Bering of Queen's University Belfast ponders some of the more obscure aspects of everyday human behavior. Ever wonder why yawning is contagious, why we point with our index fingers instead of our thumbs or whether being breastfed as an infant influences your sexual preferences as an adult? Get a closer look at the latest data as “Bering in Mind” tackles these and other quirky questions about human nature. Sign up for the RSS feed or friend Dr. Bering onFacebook and never miss an installment again.