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Why You Yawn

Everything you’ve learned about reading a person’s body language probably left out one of the most misunderstood and misinterpreted signals: the yawn

Let’s say you’ve started talking to someone you find attractive. Suddenly, they yawn. Does that mean they’re bored or disinterested? It could actually mean just the opposite.

Keep reading to find out what we know and don’t know about yawns, and what it might mean when they happen.

Who Yawns and When

Birds do it. Fish do it. But bees don’t. Every creature with a backbone yawns, it turns out.

Humans yawn when they’re tired, hot, or need to be hyper-alert. We sometimes yawn while getting ready to perform, enter danger, or compete in events, and some people do it before sex.

A few species – baboons, bonobos, chimpanzees, dogs, and humans – find it contagious and do it in groups. When one starts, others can pick it up, especially family and friends. Humans don’t usually pick up contagious yawning until they’re around five years old. And not everyone does it.

Babies have been seen yawning while still in their mother’s womb.

Dogs can yawn to calm themselves down when they’re stressed, or before getting ready to attack.

Just talking or reading about yawning can make us yawn. Have you done it yet while reading this?

What Happens When You Yawn

Yawning, like sneezing, is an involuntary response. When you yawn, your mouth opens wide, jaw drops, throat relaxes, and your abdominal muscles tighten and push your diaphragm down. Your arms may stretch out and up. You take a lot of air into your lungs, hold it for a bit, and then blow it out using more force than you normally would with an exhale. The whole process takes about six seconds.

After a yawn, you feel relaxed, like you do after sneezing or having an orgasm, two other involuntary responses.

Why You Yawn

Yawning seems to serve many different functions, and almost none of them are well understood. It’s all pretty theoretical. Here’s some current thinking about different kinds of yawns and what they might mean:

Sleepy yawns seem to have something to do with biological rhythms and hormones produced during sleep and just before waking.

Alert yawns are a bit more complicated. It’s thought they’re a way your body tries to help your brain function better. Scientists once thought “afternoon-meeting yawns” were to get additional oxygen to your body or expel carbon dioxide from it, but that’s been disproven. Instead, the deep-breath yawn may simply be a way to cool your body and the blood that’s going to your brain.

Under stress, excitement, or fatigue, the body and brain can heat up. A warmer brain doesn’t operate the same way it does when it’s the right temperature. Since outside air is usually cooler than your body’s 98.6 degrees, breathing it in can have a cooling effect. Scientists are starting to think the reason the maxillary sinuses between your nose and cheeks inflate and deflate quickly when you yawn is to cool your blood.

Contagious yawns are even more complex. Evolutionary theory suggests that survival is helped when an entire group stays alert. One member yawns to stay vigilant in response to danger, and the signal and alertness get passed to the rest of the group. Yawning can also show your teeth and make you look intimidating to predators.

Contagious yawning is also another type of social signal. It might be about empathy and showing you feel what someone else feels. However, this idea of empathy is falling out of favor as a main reason for contagious yawning.

Meet the Author

Amy Eva Swift-Johnson, MD is a family medicine physician at Aurora Medical Center in Burlington.

Read more posts from this author

The information presented in this site is intended for general information and educational purposes. It is not intended to replace the advice of your own physician. Contact your physician if you believe you have a health problem.

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