I won't take offense if this article makes you look a bit sleepy. Just reading about yawns can — wait for it — induce one without warning. And it’s not because your brain needs oxygen, whatever the schoolyard myth.
But why is yawning contagious? Some current theories focus on yawning as a social cue (like laughing) that communicates information and helps organize group behavior.
By passing from person to person with unconscious ease, a yawn can convey some piece of information (perhaps "I’m tired" or "this opera is dull") around a social circle. Such a tool would have come in handy in pre-language days. But does the science back this up?
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One 2005 study scanned the brains of people watching yawns, and located unique activity patterns in brain areas related to behavioral mimicry. So next time you get a dirty look for yawning in a meeting, chalk it up to caveman communication.
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