mise à jour du
25 janvier 2009
Surprising facts ans misleading myths about our health
Anahad O'Connor


Is yawning contagious
Prepare to yawn uncontrollably.
Dont worry. That statement is not a direct commentary on what you are about to read.
As most people may hat noticed, yawning can have such a strong and immediate impact that merely reading about it, thinking about it, or hearing someone else do it is enough to make us yawn. You can even set up your own little office experiment to confirm it. Sit at your desk at about 2 P.M. and observe the rippling chain reaction that one person's post-lunch-slump-induced yawn can trigger, much like a wave at a baseball game.
And it's a behavior that is not limited to us jaded modern types. Yawning is a mysterious act with ancient origins, one that can be seen in a diverse cross section of the animal kingdom fish, crocodiles, primates, dogs, even birds. Yawning has even been observed in newborn babies and human fetuses.
So surprisingly, yawning is contagious.
But the issue is not exactly black and white. In a series of good, old scientific experiments, researchers at the State University of New York found that it's generally people who score high on tests of self-awareness and empathy that fall prey to the contagiousness of yawning. That, they found, applies to about 50 percent of the American population.
Since people who score high on tests of empathy are more Likely to be liberals and Democrats, other studies show, you can carry these findings a little further and argue that liberals and Democrats who, go figure, make up roughly 50 percent of the voting population are more likely to make each other yawn. Somewhere in here, there is a joke about Democrats.
But on to the other 50 percent of the population. Studies show that people who don't find yawning contagious are more likely to have, problems with self-recognition, an extreme exampie of which is schizophrenics. These are people who score low on tests of empathy.
Animals can be infected by the yawn bug too. One study by researchers at the University of Stirling in Scotland found that a third of adult chimps exposed to videos of yawning chimps will end up yawning themselves.
But one thing no one can say for sure is why anyone man, woman, or chimp yawns to begin with. Conventional wisdom suggests that we yawn when we are bored. Sure. That's one reason. But scientists say they have also observed yawning in professional athletes just before a big event, in entertainers before they go onstage, and in dogs getting ready to pounce on one another.
The more scientifically minded argue that we yawn when we have a shortage of oxygen in the blood or a buildup of carbon dioxide in our systems. That deep breath and gaping of the mouth that characterize yawning supposedly counteract this. But studies have also found that breathing high levels of carbon dioxide does not trigger yawning, nor does breathing high levels of oxygen inhibit it.
Okay, you say, but how about sleepiness? Clearly sleepiness must be the underlying cause of yawning, right? Not exactly. While research confirms that people really do yawn when they are sleepy-obviously-it also shows that we yawn the most in the hour after we wake up. even after a long, sufficient night of sleep.
Rest assured, though, there are more than enough scientists working on this so that one day the mystery of yawning will be unraveled.