You’re abroad, somewhere far from home. Nature calls, and you need to drop the kids off at the pool. You run to a toilet, sit on the porcelain throne, and wait. You continue to wait. Nothing happens. This is an unmitigated disaster. You are but a poop package, refusing to empty itself.

Fret not, dear reader, for you are not alone. As explained in a rather glorious article over at The Atlantic, this is something that afflicts many around the world – as does the overwhelming urge to pinch one out when you walk into your very own bathroom back at home. Why is that?

Few would disagree that it’s a lot more comfortable to let the proverbial turtles loose while perched atop your own toilet. Nick Haslam, a professor of psychology at the University of Melbourne, explains why this is.

“In my view the experience of ‘unburdening’ upon returning from a trip is largely a Pavlovian response: The home is a safety signal, signifying that this is the right place to go,” he said. “If there has been any inhibition or retention at all during the trip the relaxation response is likely to kick in when you come home.” 

Essentially, when you’re abroad, the fear of unfamiliarity prevents you from dropping your stinky depth charges. This is sometimes referred to as "travel constipation", and Dr Brooke Gurland, a colorectal surgeon at the Cleveland Clinic, told The New York Times that this is simply because we are "creatures of habit." When this is altered, our bowels get spooked.

In addition to this, we often drink more alcohol, drink less water, and get jet lagged abroad, all of which makes it more likely we actually get conspitation. All in all, it's a bad mix, and pooping simply isn't as efficient as it used to be.

If we get nervous around toilets abroad, Gurland notes that we hold in our stools, which harden and dry inside our colons, much like a plug. Wonderful.

When you get back home, however, the kraken awakes.

Importantly though, you don’t actively think about this. You don’t look at your toilet and seriously consider the need to depressurize your hidden volcano. The evacuation of your rectal rocket happens automatically – and that, Haslam notes, is the interesting part.

When you walk through your door, you see, smell, and hear things that are familiar. You relax both mentally and physiologically in your fortress of solitude. Regular order has been restored and your body doesn’t feel like it needs to be on a defensive setting. It relaxes – and so do your bowels.

That’s the long and short of it. You don’t control your poop powers – they control you. You must obey them, even if you feel differently.

Clearly, Judy Garland was right: There’s no place like home, although we’re pretty sure that’s not quite what she meant by it over in Oz.