Yawning: Why and What Could It Mean?

Contagious yawning: 
This is induced by witnessing another yawn. Thinking about a yawn is also known to cause one. Contagious yawning is triggered involuntarily when we observe another person yawn -- it is a common form of echophenomena -- the automatic imitation of another's words (echolalia) or actions (echopraxia). And it's not just humans who have a propensity for contagious yawning -- chimpanzees and dogs do it too.A growing body of evidence suggests that contagious yawning is closely linked to empathy. ... A recent study found that yawn contagion was highest among family members, lower for friends, lower still for acquaintances and lowest for strangers (the same is also true among chimpanzees and bonobos).