What makes yawning so contagious? it's harmless but it seems to very quite contagious.

YES: A recent study shows that yawning when others yawn is a sign of empathy and a form of social bonding. Kids don't develop this deeply rooted behavior until around age four. "emotional contagion seems to be a primal instinct that binds us together, " said molly helt, a graduate student in clinical psychology at the university of connecticut, storrs. "yawning may be part of that.".