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You don't yawn because you're tired

By Sam Frizell, TIME.com
updated 7:09 AM EDT, Fri May 9, 2014
STORY HIGHLIGHTS
  • A new study suggests we yawn because our brains get too hot
  • Researchers at the University of Vienna tested subjects in Austria and Arizona
  • Sex, season, age, humidity, time spent outside, and amount of sleep did not have an effect

(TIME.com) -- Chances are you read this sentence about yawning and you yawned. Right?

Well, a new study suggests that you may not really be yawning because it's contagious, or you're bored or tired.

You're actually yawning because your brain is too hot.

A group of researchers at the University of Vienna tested subjects in Austria and Arizona and tracked their activity, finding that that the only significant predicator of yawning was temperature: subjects were much more likely to yawn at higher temperatures.

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Other factors like sex, season, age, humidity, time spent outside, and hours of sleep the night before did not have a significant effect on the likelihood of a subject's yawning.

Ultimately, it appears that yawning is related to regulating brain temperature and creating a state where arousal in a yawner can be achieved.

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The idea is that if it's hot, but still cool enough so that a large intake of air will bring your body temperature down, you're in perfect storm territory for yawns.

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