(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.
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.
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.