Yawning?

Why do animals, including man, yawn? What purpose does yawning have? Does excessive yawning an adverse medical symptom?

IANAD, but I heard that yawning is just a reflex which forces you to take a deep breath. It happens when the oxygen level in your brain gets a little low. My guess is that excessive yawning is not very serious, because if it was really serious, you would be feeling dizzy or passing out.

Actually, that’s not true. Once again (I’m on a roll), I’m far too lazy to find a cite, but seeing as how I’ve nailed every point thus far without a cite, it’s a safe bet to believe what I’m saying. In fact, I think Cecil wrote about it on this site.

Cecil on yawning:
http://www.straightdope.com/classics/a2_309.html

You may want to search GQ. There’ve been at least 3 threads within the past year.

I once read that not being susceptible to “contagious yawning” is a symptom of psychosis.

I dunnowhat cured it, but yawning became a compulsive disorder for me at about age 6. I think the doc told Momandad just to make me stop as I would become real geeky. I stopped of my own volition.
I have no circulatory problems, and my lung capacity is WAY HUGE. SO says I have some sysptoms of sleep apnea though.
I really think it became a habit 'cause it feels soooo…