Yawning
Yawning isn’t just a not-so-subtle signal to your friend that their story is boring you. This natural bodily inclination actually helps to regulate the temperature of your brain, according to the experts at the Smithsonian Institute.
“When we stretch our jaws, we increase the rate of blood flow to the skull,” they note. “And as we inhale at the same time, the air changes the temperature of that blood flow, bringing cooler blood to the brain.” And given how much work the brain does each and every day, this is a very important—and protective—function.