Why do we yawn?

Answer:
I was always under the belief that it was you catching your breath again because as you start to drift into a sleep, you're breathing slows down. This catches that back up since we're actually awake and not sleeping...

But it's funny how addictive a yawn is, I read the question and yawned. x.x;

-Tim

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Technically it is a lack of oxygen. Mainly because we are tired and bored.

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cause were sleepy! lol

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we yawn because we are breathing slow at that moment not b/c we are tierd

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We either yawn because we are tired or bored, and when you yawn your eyes get watery so you fall asleep faster

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Not much is known about why we yawn, or if it even serves any useful function. In fact, very little research has been done on the subject because for most of us, yawning is not a problematic behavior. Although not yet fully understood, yawning involves complex interactions between unconscious parts of the brain and the body (1). A long standing belief is that yawning is caused by fatigue, drowsiness, or boredom. But as the fields of brain science and behavior explode in growth and research, scientists are discovering that there is much more to the simple act than we previously thought.
In the quest to discover why we yawn, scientists have discovered many interesting facts. Yawning is contagious: not only do 55 percent of people yawn within five minutes of seeing someone else yawn, but blind people yawn more after hearing an audio tape of people yawning.

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lack of oxygen or we're just tired thats why we yawn

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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 are born. Research shows that 11-week-old fetuses yawn.

While the dictionary tells us that yawning is caused by being fatigued, drowsy or bored, scientists are discovering that there is more to yawning than what 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 yawn. Here are the three most common theories:


The Physiological Theory -- Our bodies induce yawning to drawn in more oxygen or remove a build-up of carbon dioxide. This theory helps explain why we yawn in groups. Larger groups produce more carbon dioxide, which means our bodies would act to draw in more oxygen and get rid of the excess carbon dioxide. However, if our bodies make us yawn to drawn in needed oxygen, wouldn't we yawn during exercise? Robert Provine, a psychologist at the University of Maryland, Baltimore County, and a leading expert on yawning, has tested this theory. Giving people additional oxygen didn't decrease yawning and decreasing the amount of carbon dioxide in a subject's environment also didn't prevent yawning.
The Evolution Theory -- Some think that yawning is something that began with our ancestors, who used yawning to show their teeth and intimidate others. An offshoot of this theory is the idea that yawning developed from early man as a signal for us to change activities.
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 or tired, this theory doesn't explain why Olympic athletes yawn right before they compete in their event. It's doubtful that they are bored with the world watching them

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think it is a reaction to increase the oxygen flow into the body if it is lacking. If you get tired you get sluggish and breathe shallower so you yawn to increase the Oxygen. Don't quote me on this though - my source is not exactly reliable

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Because someone else did.

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Yawning is the body's way of reducing drowsiness. Drowsiness is created by the brain, to enable sleeping. The brain is run by oxygen. Yawning is to gather a large amount of oxygen for your brain, to help it function faster and control drowsiness.

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