From the book titled: oxymoronica (by Dr. Mardy Grothe), G.K. Chesterton was quoted as saying “A yawn is a silent shout.” I’ve heard that yawns were a sign of an oxygen deficiency to the brain and they generally occur during time of relaxation and drowsiness. There are several theories as to the why . . . physiological theory, evolution theory, boredom theory, brain-cooling theory . . . and who knows what other reasons may get posited at one time or another. What about the “contagious” theory? Here’s an interesting video to help explain it all. Or, if you want to read more, here’s a link to some additional information.