[♪ INTRO] *hic*.

Ah, hiccups. We've all been there.

Usually, they're no big deal – unless you're one of the 4,000 Americans admitted to the hospital every year for hiccups, or you're that Iowa farmer who hiccuped for 68 years straight. Still, even the occasional bout of hiccups can be annoying. And as you hold your breath or gulp down water to try to make them stop, you may wonder:.

Why is this happening to me? Well… scientists don't really know. But teeny little baby hiccups might provide a clue.

Hiccups mainly involve the diaphragm (that dome-shaped muscle below your lungs that drives your breathing) and the glottis (the opening between your vocal cords). Basically, they occur when your diaphragm spasms, causing you to rapidly inhale. That forces your glottis to audibly slam shut.

And everyone experiences them at some point — they're one of the first things we do in the womb. Fetuses begin hiccuping at just nine weeks old. And they continue to hiccup a ton (between 8 and 14 times per hour!) until they're about 24 weeks old.

Then, things settle down somewhat. Though, young babies still hiccup a bunch, especially if they were delivered early. For example, preterm newborns (those born before 37 weeks) spend an average of 15 minutes a day hiccuping!

Which got scientists at University College London thinking that there might be a developmental purpose behind all this convulsing. So for a study published in December 2019, they outfitted 13 newborns with a cute cap of electrodes and monitored their hiccups. They found that every time a baby's diaphragm contracted, it triggered two large brainwaves, then a third brainwave.

The third wave is the most interesting, because it looks similar to the brainwave created when we hear a noise. So, the researchers think the babies may be hearing the “hic” and connecting it in their brains with the sensation of their diaphragm contracting. This may allow their brains to form neural circuits which help them sense what's happening with their internal organs.

The fancy scientific term for this ability is interoception, and it's how you know you're having trouble breathing, or your stomach feels full, or your heart is beating fast. Creating these nerve connections between the brain and the diaphragm could also help them learn to control their breathing. The same scientists think something similar happens when fetuses kick in the womb.

Basically, those kicks may help them create mental maps of their bodies so they can sense where their legs are, and, eventually, learn to make voluntary movements. So why do adults hiccup if our brains don't need to learn how to breathe anymore? That's a good question.

It could simply be that we can't get rid of this reflex after it's served its purpose. But who knows? There aren't a whole lot of studies of run-of-the mill occasional hiccuping in adults since, well, it's not really something doctors are concerned about.

So maybe if scientists investigated hiccups more, they'd find these spasms have a weirdly amazing purpose in adults, too. Thanks for asking about hiccups, Michelle and Anne! And thanks in general to all of our patrons on Patreon.

We have the most wonderfully nerdy community of supporters! If you'd like to join them, you can learn more at Patreon.com/SciShow. And if you're already a patron and have a weird question like this about how the world works, drop it in our QQ inbox!

We not only read those questions, we make some of them into videos like this one. So your question could be next! [♪ OUTRO].