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Long yawns may help bigger brains beat the heat

Before you go to bed tonight, odds are you’ll yawn a bit, unless your house happens to be especially hot or cold. This is because yawing may be more closely tied to the temperature of your brain than weather or not you could use a nap. While yawning has been a bit of a physiological mystery for a long time, researchers are finding more evidence that yawns are designed to help cool off our brains, which are calorically intense organs enclosed in skulls without a lot of ways to vent heat. The volume of bigger brains can build up more heat, which, according to YouTube, may be cooled by a nice big yawn.

Before your brain snaps at the idea of research being done alongside reaction vids and unboxing clips,¬†YouTube was actually where researchers from the State University of New York at Oneonta sourced videos of over 100 animals yawning on camera. The 19 different species represented gave a decent sampling of different types of animals, including humans, that regularly yawn. To tie that to the aforementioned brain-cooling hypothesis, yawns were timed and then compared against a species’ known brain size. A strong correlation emerged between bigger brains requiring long yawns, with humans topping both lists from this survey. This pattern supports the notion that those brains are likely to be heating up more, and therefore need more time to vent and regain a more optimal temperature.

Cranial cooling

No matter the size and duration, the basic premise would be the same for all yawning animals, from birds to humans. A big inhalation of air may be giving a boost to blood circulation, allowing brain-cooked blood to be drawn away and replaced with air-cooled blood a bit faster. Cooler air being drawn into our sinuses and throats may also contribute to this cooling process, which helps explain why yawning isn’t needed as much when it’s very cold, but isn’t as helpful when it’s very hot out. An alternative, or possibly auxiliary, benefit is that a good yawn may boost the flow of¬†cerebrospinal fluid, giving your brain a bit of a wake-up call.

Which brings us back to why, if temperatures are conducive, you’ll probably be yawning before bed. It’s easy to associate yawning near your bedtime with being sleepy, or with just waking up. These yawns probably aren’t due to your circadian rhythm though, but are more likely tied to times when your body temperature is naturally elevated. So while we often think of yawns as a sign of boredom or fatigue, it may just be time to open a window or turn on a fan.

Source: The bigger the yawn, the bigger the brain, scientists find by Sharon Begley, Stat News

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