In the latest SciShow, host Hank Green sets out to explain why humans — like nearly every other vertebrates — yawn. While he admits that science still isn’t entirely clear why we do it, research indicates that yawning is a built-in method our bodies have for cooling off.
Recent studies show that yawning is your body’s natural air conditioning system, bringing cool blood to chill out your overheated, overtired grey matter. Your brain actually heats up when it uses over 40-percent of your body’s metabolic energy, just like your laptop heats up when you’ve been playing video games for hours.
According to the theory, the act of yawning delivers blood to our skull by moving our jaw and helps bring fresh air into our oral cavities.