What makes us yawn?

Hi Am Marshall Brain with today's question, what makes us yawn? The next time you're in a meeting, try this little experiment. Take a big yawn, cover your mouth out of courtesy, and watch and see how many other people in the room yawn with you. There's a good chance that you'll set off a chain reaction of yawns. In fact, before you finish here, it's likely that you will yawn at least once. Just hearing about yawning will sometimes make people yawn.

Just to seeing or hearing someone else yawn makes us yawned. What's behind this mysterious epidemic of yawning? First, let's look at what a yawn is Yawning is an involuntary action that causes us to open our mouths wide and breathe in deeply. We know it's involuntary because we do it even before we're born. Research shows that eleven week old fetuses yawn. There are many parts of the body that are in action when you yawn. First, your mouth opens and your jaw drops, allowing as much air to be

taken in as possible. When you inhale, the air taken in is filling your lungs to capacity. Your abdominal muscles flex, and your diaphragm is pushed down. The air you breathe in expands the lungs, and then some of the air is blown back out. While the dictionary tells us that yawning is caused by being fatigued at drowsy or board, scientists are discovering that there is more to yawning. Most people think not much is known about why we yawn or if it serves any useful function, and very little

research has been done on the subject. However, there are several theories about why we yawned. Here are the three most common. The first is the physiological theory our bodies induced yawning to draw in more oxygen or remove a build up of carbon dioxide. This theory helps explain why we yawning groups. Larger groups produce more carbon dioxide, which means our bodies would act to draw in more oxygen

and get rid of excess carbon dioxide. However, if our bodies make us yawn to draw and needed oxygen, wouldn't we yawn during exercise? A leading expert on yawning has tested this theory. Giving people additional oxygen didn't decrease yawning, and changing the amount of carbon dioxide in the subject's environment also didn't prevent yawning, so this doesn't necessarily seem to be a very valid theory. Then there's the evolution theory.

Some think that yawning is something that began with our ancestors, the idea that yawning developed from early man as a signal for us to change activities or to do something differently. Then there's the boredom theory. In the Dictionary, yawning is said to be caused by boredom, fatigue, or drowsiness. Although we do tend to yawn when bored are tired, this theory doesn't explain why Olympic athletes yawned right before they compete in their event. It's doubtful that they're bored with

the world watching them. The simple truth is that even though humans have been yawning for possibly as long as they have existed, we have no clue as to why we do it. Maybe it serves some healthful purpose. It does cause us to draw in more air, but so does exercise. There's still much we don't understand about our brains, so maybe yawning is triggered by some area of the brain we have yet to discover. We do know that

yawning is not limited demand. Cats, dogs, even ish yawned, which leads aspect to the idea that yawning might be some form of communication. For more illness and thousands of other topics. Visit how stuff works dot com and don't forget to check out the brain stuff blog on the how stuff works dot com home page. You can also follow brain stuff on Facebook or Twitter at brain stuff hs W. Brain Stuff is sponsored by Harry's dot Com. Get a great shaving experience for a fraction of the price.

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