Why do we yawn? Why are yawn's contagious?

Question

Why do we yawn? Why are yawn's contagious?

Answer 1

The latest research suggests that we yawn simply to keep us awake. An alternative answer here

http://www.sciencebase.com/science-blog/...

Answer 2

Yawning is actually when you don't have enough air, if you think of it, yawning is taking a big breath.

It's not really contagious, that's psychological, your brain thinks that you need to.

And usually, when someone yawns, other people are in the same room with not enough air.

Like in an elevator or a bus without an AC.

And usually you yawn when you're tired because when you're tired it's because of two reasons: either you used up all the energy in your body, or second, your body isn't clean enough in the inside because you don't drink enough and/or you don't have enough air.

Answer 3

Because any time we get tired.

Answer 4

To cool the brain.   Yes and who knows why.

Answer 5

I've heard that yawning is used to draw in air in to cool the brain and that its contagious because of mirror neurons cause you to mimic this action from others.

Answer 6

I heard a theory once, that it's the way that humans syncronize our bodies with one anothers. Also yawning is a sign that you aren't getting enough oxygen, alot of people make the assumption your tired when you yawn because when you feel fatigued your breathing slows denying your body of much needed, life sustaining oxygen. Yawning is basically a big gulp of air into your lungs it's your body's way of saying MORE....AIR.......