Here's Why Yawning Is So Contagious

Have you noticed the domino effect that occurs when someone in the room lets out an unnecessarily long yawn?

Well, there’s a reason why yawning is so contagious.

Take a look as we present some of the current theories below. Chances are you already yawned simply reading this. (Good luck with the video.) 

Produced by Justin Gmoser and Will Wei

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