Aahh, the Science of Yawning

It can signal tiredness, boredom or even rudeness, and everyone does it. But, now, a new science may explain why people yawn, and even crack one of the world's most mysterious phenomena — the contagious yawn.

Some people think yawning stems from a need to stretch or change. Until recently, scientists thought people yawned to replenish oxygen supplies to their blood.

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