Over the past few months, we’ve been introduced to a phrase we thought we’d never hear: the “serial pooper,” which refers to someone who continually poops in public, leaving the fruits of their labor on display for all to see.

In September, it was the “mad pooper,” who, when out for her morning jogs—her “morning runs,” if you will—defecated in front yards, on sidewalks, and even in front of a drugstore.

More recently, Southern Illinois University reported on a “bowel movement bandit” who’d pooped in dorm washing machines not just once or twice, but eight times. Not in empty machines, either—the pooper was dumping into clothes that had already been through the wash cycle.

Are these public poopings due to extraordinarily loose bowels? Or are they the ultimate “screw you”? Most likely, it’s the latter, says clinical psychologist Sharon Chirban, Ph.D. of Amplify Wellness & Performance in Boston.

“It is the ultimate F.U. and vandalism crime,” she says. Now, she says, there are exceptions to the rule, like for those in full-blown psychosis, who may not realize where they are, and people on a bar crawl without access to a public bathroom—but even then, they tend to slip behind dumpsters for some measure of privacy. (Here's what to do if you get diarrhea on a run.)

Serial poopers, by contrast, are very intentional. And, in many cases like the neighborhood jogger, they don’t even go through any lengths to keep their identity anonymous.

“It’s a statement,” says Chirban. “They’re expressing aggression through an egregious act.”

A public dump certainly is egregious. But what’s the drive behind all that hostility? Well, without sitting the serial poopers down in front of a psychologist, all experts can do is speculate. But there are some leading thoughts on what’s triggering them.

“As with other vandalizing behavior like tire slashing, graffiti, or salting lawns, the motivation is anger or envy,” she explains. “Maybe the lawn pooper is envious of those in that neighborhood. Maybe the laundry pooper is angry about the laziness of others to empty washers in a timely fashion.”

Then, there’s the serial aspect of it: Once or twice could be explained away as a poop emergency. But seven or eight times in the same location? That becomes close to an addiction in some ways, according to Dr. Chirban.

And that addiction might be feeding the behavior even more.

“There can be a secondary gain from getting away with it,” she says. “That can lead to a kind of invincibility, and rationalizing as ‘they deserved it anyway.’ When the behavior continues, there’s no remorse. Instead, you see a growing sense of grandiosity, a type of vindictive rage getting acted out.”

The American Council on Science and Health refers to the phenomenon of public defecation as a potential “elimination disorder”—a diagnosable mental disorder marked by the inappropriate passage of feces or voiding of urine—but there could be much more at play for some people, according to clinical psychologist Bart Rossi, Ph.D.

He agrees that anger is the dominating force, but that it could be mixed with other problems. After all, you probably got mad at your boss once or twice, for instance—but when’s the last time you pooped on his doorstep as a result of it? So there are likely other things at play with the serial poopers, says Rossi, including possibilities like narcissistic personality disorder and obsessive-compulsive disorder.

“These people might also have a thought disorder, believing that this is what it takes to be recognized,” Dr. Rossi says. In other words, they may have had an issue with something else, but believe they wouldn’t be listened to or acknowledged—so they had to poop to make it known.

And of course, recognized they are. Poop is actually quite a powerful tool, Dr. Chirban, and it shows aggression in the most primal fashion possible.

So the act of serial public pooping isn’t really a laughing matter. And portraying them as kooky, light-hearted, and funny news stories might be masking the real issues at play—and it could be inadvertently condoning the behavior as socially acceptable, says Chirban. As a result, it might inspire copycats.

How to Tell If Your Poop is Normal:

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Bottom line: The urge to purge in public might be hinting at a more serious problem—not just a lack of readily-available bathroom facilities. (For more health news delivered right to your inbox, sign up for our Daily Dose newsletter.)