Yawning is not something we usually aim to provoke among our readers, but have a yawn now. Does your brain feel cooler? Do you feel more attentive? According to psychologists Andrew and Gordon Gallup of the State University of New York at Albany, that is why we yawn: to boost blood flow and chill the brain.
Not only that, brain-cooling explains why you can “catch” a yawn, says Gordon Gallup. “We think contagious yawning is triggered by empathic mechanisms which function to maintain group vigilance.” In other words, yawn-catching evolved to help raise the attentiveness of the whole group.
Blood vessels in the nasal cavity send cool blood to the brain, so breathing through the nose or cooling the forehead cools the brain and eliminates the need to yawn, says Gordon Gallup. He argues that brains operate more efficiently when cool, and that yawning enhances brain function. “According to our hypothesis, rather than promoting sleep, yawning should antagonise sleep,” he says.
Yawning signals a transition between the behavioural states of wakefulness and sleepiness, and boredom to alertness.