People in my audiances have asked me for many years why we yawn when someone else yawns. I tell them that is yawn contangion is due do to isopraxism, the pull towards the same enegry that occurs in nature. Isopraxisism explains why birds fly together in formation, fish swim together in schools and why we do the wave at football games. We pull towards the same energy to save energy. In human relationships we tend to match people we like and feel comfortable beting around. For years the research on yawning said that matching was not the cause of mutual yawning, but I disagreed.
Now recent research supports the matching hypothesis. Though the original yawner may yawn because they are tired and or lack oxyegen, the matcher, yawns back out of kindness. Steven Platek, a reserch professor bio medical science at Drexel University in Philadelphia did resarch empthy. He found highly emphathetic people could not help but match someone's yawn. You may notice this in Gorillas and great apes at the zoo as well. (Not quite a case of monkey see monkey do, more like gorilla see gorilla do.)
So next time someone matches your yawn, you will know they are a nice empathetic person. You might want to fake a yawn today, just to see if how much people care!