Public bathrooms are also (usually) gender-segregated, creating institutionalized single-gender spaces that you almost never see anywhere else. Perhaps because of this, most research on toilet graffiti has studied the differences between what men and women write in their respective stalls. Alfred Kinsey (yes, that Alfred Kinsey) was the first to do this, in the 1950s. He and his team found that men wrote more, and dirtier, things than women, who were more likely to write about romantic love.

“Kinsey and his colleagues suggested that women’s lesser tendency to produce erotic graffiti was due to their greater regard for moral codes and social conventions,” writes Nick Haslam, a professor of psychology at Melbourne University, in his book Psychology in the Bathroom.

These fairly stereotypical analyses persist in toilet graffiti studies over the years. Though some studies say women write just as much as men, men’s is typically seen as being more aggressive and more sexual, while women’s is more conversational and more likely to be about love. Though most bathroom graffiti research was done in the 60s, 70s, and 80s, a couple studies done in the past few years have found similar things.

Nicholas Matthews, a PhD candidate at Indiana University, was the lead author on a 2012 study that analyzed toilet graffiti in nine bars in a Midwestern town. He and his fellow researchers found that the most common type of graffiti was “presence-identifying” (just scrawling your name, for example), but men were identifying their presence more than women. Women, on the other hand, wrote more insults. Matthews explains this using evolutionary psychology, saying that boosting oneself up is a typical male mating strategy, whereas putting other women down is a classic female gambit.

These are tidy explanations, but if I can stop you from furiously scribbling a book proposal titled Women Draw Hearts, Men Draw Penises for just a moment, the difference between men’s and women’s bathroom graffiti isn’t necessarily indicative of hard-wired differences between the genders. The mere fact of being in a public bathroom could be skewing how people choose to present themselves when they uncap that Sharpie.

When a woman goes into a women’s restroom and finds herself surrounded by only women (in a room full of mirrors, no less), she may very well become hyper-aware of the fact that she is a woman. People might be putting on makeup, performing their gender, and behind closed doors, they’re dropping their pants. Meanwhile, next door in the men’s room, dudes are standing next to each other at the urinal, aggressively not making eye contact, trying to ignore the miasma of testosterone that I assume hangs in the air like a fog.

So it’s very gendery in the bathroom, and at least one researcher has suggested that this could cause people to exaggerate their maleness or femaleness—he found that in the mixed-gender space of study booths, “language style… was broadly in between that of the male and female toilets.”

When you write on a bathroom wall, “you have a staggeringly diverse audience,” Matthews points out. “Many different races, classes, all walks of life, but it’s completely confined to a single gender. So it suddenly lets gender-specific issues emerge.”