why do we yawn? wat causes it?

Answer 1

We yawn by reflex due to lack of enough oxygen in the brain. It does seem to be catchy if you see someone else yawn, but yawning when tired or bored also has to do with too little oxygen, because you are breathing shallowly.

Answer 2

The article linked below has some interesting facts on yawning. The exact cause is not known. One can start yawning even by thinking about it.

Answer 3

Yawning helps regulate the carbon dioxide and oxygen levels in the blood.

Technically, a yawn is the reflex opening of the mouth followed by the deep inhalation and slow exhalation of oxygen.

A yawn is triggered either by fatigue, or by sheer boredom as, at those times, breathing is shallow, and little oxygen is carried to the lungs by the oxygen-toting cardiovascular system.

When you yawn, your alertness is heightened, as the sudden intake of oxygen increases the heart rate, rids the lungs and the bloodstream of the carbon dioxide buildup, and forces oxygen through blood vessels in the brain, while restoring normal breathing and ventilating the lungs.

Answer 4

Bill Nye had an article about this. Here's an excerpt

"It's an age-old question, one that can keep you awake at night, and there is no exact answer. Near as we can tell, yawning is a way to signal others around us that we feel like getting some shuteye."

Answer 5

It is a lack of oxygen to our brains. And yawning is our brains signal to the body to open our mouths and suck in a BIG gulp of air.

So if you start yawning....stop for a minute and just take some deep breaths. The yawning (unless you've been up for days) will stop.

Answer 6

When you breathe too slowly or shalowly, your body and particularly the brain need extra oxygen.
Yawning is the way the body forces you to a inhale plenty of oxygen.

It has nothing to do with boredom or tiredness.

Answer 7

lack of oxygen

Answer 8

We're tired.