KIMBERLY WALTERS, PORTLAND, OREGON: My name is Kimberly Walters, I'm from Portland, Oregon, and my question is why do yawns seem to be contagious?</s>RHONDA ROWLAND, CNN MEDICAL CORRESPONDENT: Boredom and drowsiness are often associated with yawning, yet there is no sound scientific answer as to why we yawn, let alone why it seems to be contagious. Explanations run the gamut. Some say yawns synchronize sleep among group-living animals. Others say it prevents a loss of lung compliance during normal breathing. More recently, some scientists speculate it is an involuntary reaction to a rise in carbon dioxide: We yawn to get more oxygen. It has even been said that yawning has no physiological function at all. What we do know is that a yawn seems to be contagious. If you believe in the theory that we yawn to get more oxygen, seeing someone else yawn may be a trigger for you too to yawn, to test if there is too much carbon dioxide. So the jury is still out on exactly why we yawn. But I bet that even hearing about it -- just the suggestion -- makes you want to yawn.
Ask CNN: Why Do Yawns Seem to Be Contagious?