WEBVTT - What makes us yawn?

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<v Speaker 1>Hi Am Marshall Brain with today's question, what makes us yawn?

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<v Speaker 1>The next time you're in a meeting, try this little experiment.

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<v Speaker 1>Take a big yawn, cover your mouth out of courtesy,

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<v Speaker 1>and watch and see how many other people in the

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<v Speaker 1>room yawn with you. There's a good chance that you'll

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<v Speaker 1>set off a chain reaction of yawns. In fact, before

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<v Speaker 1>you finish here, it's likely that you will yawn at

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<v Speaker 1>least once. Just hearing about yawning will sometimes make people yawn.

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<v Speaker 1>Just to seeing or hearing someone else yawn makes us yawned.

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<v Speaker 1>What's behind this mysterious epidemic of yawning? First, let's look

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<v Speaker 1>at what a yawn is Yawning is an involuntary action

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<v Speaker 1>that causes us to open our mouths wide and breathe

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<v Speaker 1>in deeply. We know it's involuntary because we do it

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<v Speaker 1>even before we're born. Research shows that eleven week old

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<v Speaker 1>fetuses yawn. There are many parts of the body that

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<v Speaker 1>are in action when you yawn. First, your mouth opens

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<v Speaker 1>and your jaw drops, allowing as much air to be

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<v Speaker 1>taken in as possible. When you inhale, the air taken

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<v Speaker 1>in is filling your lungs to capacity. Your abdominal muscles flex,

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<v Speaker 1>and your diaphragm is pushed down. The air you breathe

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<v Speaker 1>in expands the lungs, and then some of the air

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<v Speaker 1>is blown back out. While the dictionary tells us that

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<v Speaker 1>yawning is caused by being fatigued at drowsy or board,

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<v Speaker 1>scientists are discovering that there is more to yawning. Most

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<v Speaker 1>people think not much is known about why we yawn

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<v Speaker 1>or if it serves any useful function, and very little

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<v Speaker 1>research has been done on the subject. However, there are

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<v Speaker 1>several theories about why we yawned. Here are the three

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<v Speaker 1>most common. The first is the physiological theory our bodies

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<v Speaker 1>induced yawning to draw in more oxygen or remove a

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<v Speaker 1>build up of carbon dioxide. This theory helps explain why

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<v Speaker 1>we yawning groups. Larger groups produce more carbon dioxide, which

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<v Speaker 1>means our bodies would act to draw in more oxygen

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<v Speaker 1>and get rid of excess carbon dioxide. However, if our

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<v Speaker 1>bodies make us yawn to draw and needed oxygen, wouldn't

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<v Speaker 1>we yawn during exercise? A leading expert on yawning has

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<v Speaker 1>tested this theory. Giving people additional oxygen didn't decrease yawning,

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<v Speaker 1>and changing the amount of carbon dioxide in the subject's

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<v Speaker 1>environment also didn't prevent yawning, so this doesn't necessarily seem

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<v Speaker 1>to be a very valid theory. Then there's the evolution theory.

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<v Speaker 1>Some think that yawning is something that began with our ancestors,

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<v Speaker 1>the idea that yawning developed from early man as a

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<v Speaker 1>signal for us to change activities or to do something differently.

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<v Speaker 1>Then there's the boredom theory. In the Dictionary, yawning is

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<v Speaker 1>said to be caused by boredom, fatigue, or drowsiness. Although

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<v Speaker 1>we do tend to yawn when bored are tired, this

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<v Speaker 1>theory doesn't explain why Olympic athletes yawned right before they

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<v Speaker 1>compete in their event. It's doubtful that they're bored with

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<v Speaker 1>the world watching them. The simple truth is that even

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<v Speaker 1>though humans have been yawning for possibly as long as

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<v Speaker 1>they have existed, we have no clue as to why

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<v Speaker 1>we do it. Maybe it serves some healthful purpose. It

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<v Speaker 1>does cause us to draw in more air, but so

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<v Speaker 1>does exercise. There's still much we don't understand about our brains,

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<v Speaker 1>so maybe yawning is triggered by some area of the

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<v Speaker 1>brain we have yet to discover. We do know that

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<v Speaker 1>yawning is not limited demand. Cats, dogs, even ish yawned,

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<v Speaker 1>which leads aspect to the idea that yawning might be

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<v Speaker 1>some form of communication. For more illness and thousands of

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<v Speaker 1>other topics. Visit how stuff works dot com and don't

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<v Speaker 1>hs W. Brain Stuff is sponsored by Harry's dot Com.

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<v Speaker 1>Get a great shaving experience for a fraction of the price.

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<v Speaker 1>The quality of the shave is so important that Harry's

0:04:30.680 --> 0:04:33.520
<v Speaker 1>purchased the factory that makes their blades. Fifteen dollars gets

0:04:33.560 --> 0:04:35.719
<v Speaker 1>you a set that includes a handle, three blades, and

0:04:35.720 --> 0:04:38.159
<v Speaker 1>shave cream. Go to Harry's dot com use the code

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<v Speaker 1>brain stuff to save five dollars off your first purchase.