Is Yawning Contagious? Why Do We Yawn?

Most people associate yawning with sleepiness, but the cause of the open-mouthed reflex remains a mystery. According to researchers, humans and many other animals yawn for a variety of reasons; fatigue is just one of them.

Scientists have tried for decades to figure out the physical mechanism behind yawning, and they still don’t have a definitive answer. A popular older theory held that yawning was a way to bring more oxygen into the bloodstream and move carbon dioxide out. That theory was shot down, however, after experiments showed that increased oxygen intake didn’t decrease the rate of yawning.

Another theory suggests that yawning is the body’s way of boosting heart rate and blood pressure in anticipation of an energetic or strenuous activity. There may be something to this concept, because it’s well-documented that Olympic athletes often yawn before a competition and paratroopers yawn before a jump. But that doesn’t explain the millions of other times we yawn.

We may not yet know why we yawn, but we do know when. Yes we yawn when we’re tired. We also yawn when we’re bored or nervous, and sometimes we yawn for no reason at all. In fact, just thinking about yawning can bring one on.

So the next time someone yawns in your presence, make no assumptions about his or her state of mind or degree of fatigue. Go ahead and yawn right back, yawning after all, is contagious. Or is it?

Yawning is also common in the animal world. Dogs for example, yawn when tired, just like their owners. But they also yawn when excited or tense, and they do it as a way to tell other dogs that they’re stressed and need to take a break.

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