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Have you ever done something that required a ton of concentration, like threading a needle, and noticed that sometimes your tongue pokes out involuntarily? It turns out this reflex could be a leftover from the evolution of human language!

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Have you ever noticed that when you’re trying really hard to do something, like thread a needle, your tongue will just sort of stick out all by itself? In these moments of deep concentration, your tongue isn’t really doing anything.

So why does it happen? Well, researchers are still trying to pin down the answer, but they do have some good ideas. Right now, the best explanation for this phenomenon is that poking out your tongue is your brain’s way of stopping itself from getting distracted.

See, your tongue is a bit of an attention-seeker, and it’s constantly giving your brain updates about what’s going on in your mouth. Unfortunately, all those motor inputs get sent to the same areas of your brain that help you concentrate or coordinate movements— specifically, the prefrontal cortex and the cerebellum. According to this hypothesis, your tongue gets poked out or clamped between your lips to stop to all this annoying brain chatter when you’re trying to focus.

Of course, even though this idea is well supported, the debate isn’t over yet. Some scientists think that, at least in children, tongue protrusion might not really have a purpose at all. It might just happen because kids haven’t yet mastered using the different parts of their bodies separately.

As a result, they could make what are called overflow movements— movements that don’t have anything to do with the task at hand. Like sticking out your tongue while playing a hard video game. Another, fairly new explanation also suggests that this wayward tongue might not have a purpose.

Instead, it might just be a cool leftover from when humans developed spoken language. See, some scientists suggest that language began with gestures and facial expressions. Then, sounds were added in, and eventually, voice took over.

One key piece of evidence for this is that, in our brains, the same area in charge of speech, called Broca’s area, is also in charge of some hand movements. Of course, there are also a lot of other ideas about how language developed, so scientists are always looking for more evidence to support their hypotheses. And according to one team, some of that evidence might be your stuck-out tongue.

In their paper, published in 2015 in the journal Cognition, the researchers taped 14 kids as they played different games, most of which required them to use their hands. During the games, they recorded the number of times the kids poked their tongues out. They found that at least some children stuck out their tongues for all of the tasks, but that they poked them out more frequently during a language-like game.

In this game, when the experimenter knocked on a table, the child had to tap in response. And when the experimenter tapped, the child knocked. It was a lot like two people having a gesture-based conversation.

And when the kids stuck their tongues out, it seemed like the tongue just wanted to join in the party and start speaking. During this activity, the kids’ tongues also poked out to the right side most of the time, which might point to an activation in Broca’s area on the left side of the brain. If all these conversation-like games, gestures, and tongue protrusions really do relate to the same brain area, it could help support that language evolved from our hands to our mouths.

And even though it would mean that sticking out your tongue doesn’t have a compelling purpose today, it’s still fascinating. Of course, this study has been the only one so far testing this idea, so it’ll need more research. For it to be proven true, we’d need to show that the frequency and timing of tongue poking matched up really well with the timing of those hand movements.

Whether it’s because of a distracted brain or a hangover from our evolutionary past, tongue poking happens. But no matter why it does, you have to admit that, in terms of unconscious habits, this one’s pretty endearing. Thanks for watching this episode of SciShow!

And a special thanks to Patreon patron Dr. Carbonnier for asking us this question, and to the rest of our patrons for voting on it. If you’d like to ask us a question or vote on the next ones we answer, you can go to ♪ OUTTRO ♪.