I am thrilled that my high school kid takes showers with no prompting. I do not miss the days of having to bathe kids in a tub because bathtime is a sh*t show. But my husband and I made a mistake, I think, in figuring that our son would learn from our example about how to use and leave the bathroom.

We thought he would at least realize that we hang up the towels.

But no, when he steps out of there, even after simply washing his hands (bravo for that, of course), it’s clear he grabbed a clean towel to dry — and then threw it on the floor. After a shower, the bath mat is soaked, as if he left the shower curtain open. Sometimes, when I go to clean, I worry that he is perhaps… missing the bowl when he pees. It’s all just gross, and what is confusing to the rest of us is how he doesn’t seem to notice any of it.

Help! Why are preteen and teen boys so gross?

For an explanation, I turned to pediatrician Cara Natterson, MD, author of a book I gave my son called Guy Stuff: The Body Book for Boys (published by the American Girl people). Dr. Natterson is also a mom of two kids, ages 17 and 19, and CEO of both Order of Magnitude, a company focused on puberty, and of the puberty-positive brand OOMLA.

First, Dr. Natterson said, before we get all gendered about it, bathroom mess is possibly less a gender thing and more of a birth-order thing. “Those who believe in birth order being tethered to personality would say that firstborns are pleasers, and parents like the bathroom clean,” Dr. Natterson says. She ventures that subsequent children might care less about pleasing and are therefore sloppier — and, in fact, my messy kid is my second kid. But Dr. Natterson’s firstborn, a female, is both a pleaser and a total bathroom slob, so it seems there are no hard rules for what kid is going to trash your bathroom.

Child athletes, too, have a greater amount of stinky stuff associated with them, and many kids who identify as male are into sports. “My son is an athlete and he comes home at the end of a practice and doesn’t want to put stinky clothes in the laundry basket in his room, so he dumps them in the bathtub,” Dr. Natterson says. “As if some magical fairy will pick them up.”

Can we blame teen brains for bathroom behavior?

Partially, according to Dr. Natterson, who says that consequential thinking is underdeveloped even in older teens. They’re excited to put a red streak in their hair; they don’t think through what that will mean for your white-tiled shower and white bath mat.

“There’s hair dying, hair trimming, makeup use where the product gets splattered — the kids are not wondering, ‘What should I put down on the surface to protect it?’ or ‘How quickly should I clean up so there’s no stain?’ That type of thinking is not there yet,” Dr. Natterson says. “They have that part of their brain, but it’s not sending and receiving messages as quickly as other parts of the brain. And so they are really not considering the long-term implications of, for instance, what they’re flushing down the toilet.”

But why don’t they ever notice the mess?

My husband and I are just stunned that our son doesn’t recognize that if he steps out of the shower dripping wet before he grabs a towel, he leaves a pool beneath him. Dr. Natterson blames it partly on the bathroom being a safe space for mess, as far as kid-thinking goes.

“The bathroom is where you take the grime off at the end of the day. It’s where you pull yourself together at the start of the next one, and things get dumped there. Don’t get me wrong; things get dumped on the bedroom floor too. But most parents don’t say, ‘Clean up the bathroom,’ the same way they say, ‘Clean up your bedroom.'”

And if you’re worried that it might be that kids simply don’t care… well, you may be on to something. They probably don’t. “I think this is the lowest-stakes issue for them,” Dr. Natterson says. “They’re juggling so much, and the very last thing on their list of things to be concerned about is what the bathroom looks like.”

It’s us adults who like neat countertops and garbage actually in the trash can. We get worked up, frustrated, and exhausted with the scene, especially if we share a bathroom with a kid like I do. Our apartment has one bathroom.

Seriously, though, WTF is up with their toilet etiquette?

Dr. Natterson and I compared notes about a bizarre mystery we both face: evidence of pee not so much on the floor but on the toilet pedestal, which curves in from the rim of the seat and should, theoretically, be out of target range. She and I both sit to pee, so we spent probably too much time trying to figure out where someone is looking if they stand to pee — and theorizing that maybe also some people who sit could be sloppy crouchers who don’t look behind to see what they left?

“It feels like people choose not to notice — or not to remember — that they peed on the floor,” Dr. Natterson says. They block it out and move on.

I actually ended up Googling “how does pee get on the toilet pedestal” and found an answer from, apparently, a plumber in Quora. He maintains that 30 years of plumbing gives him this insight: “A toilet in a woman’s home never has urine at the base of it. [If you stand] the splash or occasional errant stream will find its way down the outside of the bowl and on the surfaces nearby, like the wall. The ‘why’ part of it is that the urine dries very slowly and has time to run down the outside of the bowl. Over time it collects and becomes visible.”

OK, and ewwww. Also, my son will leave home eventually and share a bathroom with people who didn’t make him, so he needs to learn some neatness. There is no way around it — we have to have a bathroom talk.

“It’s a conversation that parents can and should have with their kids, which is: Acknowledge the mess and be thoughtful. Clean up after yourself,” Dr. Natterson says. “Just stop for a second and think, ‘Is someone else coming in here?’ How do you feel about what you’ve just left that person? Chances are, your kids have genuinely never thought about it before. Say it all out loud, and finally, they’ll be like, ‘Got it.'”

There is another alternative: friends who shame. “A friend’s blunt feedback, like a good friend of your kid telling them ‘Your bathroom is disgusting,’ will often get through,” Dr. Natterson says. But then, there’s always the danger that they’ll decide that’s the best bathroom for the next hair-dye experiment.