Why do we yawn?

Scientists have reached little agreement about why we yawn. The average adult yawns around 20 times per day. Surely this universal reflex serves some purpose?

Humans do it, animals do it, even babies in the womb do it. But explaining why we yawn is tricky—there are many theories but little evidence to back most of them up.

One popular theory is that we yawn due to boredom. When bored, energy is low and we don’t breathe as deeply; low oxygen levels in the body therefore trigger a yawn in order to replenish our supply. Another idea is that the increased intake of air cools the brain. When we don’t get enough sleep, brain temperature increases, and this explains why we yawn when we are tired.

Yet another interesting suggestion is that yawning helps alleviate the feeling that you can’t breathe, which is common during times of stress and anxiety. Yawning helps by expanding the rib cage, sending a signal to the brain that the body has taken in sufficient oxygen.

PSYCHOPATHS DON’T YAWN

Contagious yawning, when someone yawns and you follow suit, seems to be linked to empathy—the ability to understand and feel affinity for another person’s emotions. Several studies show that psychopaths, who by definition lack empathy, are immune to contagious yawning. It’s also been suggested that this is a survival mechanism: when one person yawns, they suck the air out of the space they are in, so someone sharing that space automatically yawns to ensure they get their fair share of oxygen. While yawning may be one of science’s great mysteries, if you’re a contagious yawner, you can at least be fairly sure you’re not a psychopath!

“Reading this might make you yawn—just thinking about yawning triggers a yawn in 88% of people.”