Hi all,
I was quite intrigued by the thread on yawning, since I too have that happen sometimes - even when I'm going into a cardio workout! I saw something on 20/20 a while back about the contagiousness of yawning and laughing. It's a little long so I've only posted the portion on yawning - I find it interesting.
-Liz
Not Just a Matter of Oxygen
The common theory about why we yawn is to get more oxygen to our brains. But according to Provine, it is not so simple. In scientific experiments, he discovered that even with 100 percent oxygen, his subjects yawned just as much as when they had less.
Yawning, says Provine, which occurs as early as the first trimester of prenatal development, is about transitions in the body’s biology. Of course, one of those changes is from a state of alertness to a state of sleepiness. But surprisingly, yawning can also be a behavior that marks a transformation from sleepiness to alertness.
“At track and field events,” says Provine, “sometimes you’ll find participants in the race of their life will be standing around on the sidelines or in the starting block and they may be yawning.” Or, for example, before a concert, a musician may yawn to prepare for an increasingly energized state.
Yawning is also a way for people to synchronize group behavior. “When you see someone yawn, you’re initiating a chain reaction of biology,” Provine says. “So whatever changes in our body are brought about by yawning, are synchronized in everyone that’s doing it.”