Q. What is the purpose of yawning?
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A. The involuntary reflex action of opening the mouth is usually a sign that you are not getting enough oxygen and that the body needs sleep, according to the World Book Encyclopedia. The 1991 Giant Book of Health Facts, by Rodale Press, says some scientists aren't so sure anymore. Dr. Robert Provine of the University of Maryland and Ronald Baenninger of Temple University theorize that yawning might be the body's way of keeping the person alert. After studying yawners and yawn-producing situaltions, they suggest this contagious, open-mouthed sigh is "the body's way of promoting arousal in situations where you have to stay awake."