I haven't watched the video. Sorry, I'm not really interested, I've heard the theory. I may watch it tomorrow, I just came here to point out the real fact of yawning. We don't know what it is. No, really, we've got nothing. There's plenty of theories, ranging from biological to social reasons, but none have ever really been proven. [a href=http://en.wikipedia.org/wiki/Yawn]Wikipedia[/a] covers the popular theories, including this one, if anyone is interested.