We do it from the time we're infants - we do it as a result of watching someone else do it. We do it when we wake up in the morning, when we're getting ready to go to bed, and even when we're bored. We yawn for a particular reason - and that reason isn't as simple as building social bonds, as is commonly thought, nor is it to up for oxygen deprivation or an overload of carbon dioxide. Did you know that 60 to 70% of people who see someone yawn will yawn in turn? Or people who score higher in empathy are more likely to yawn after seeing someone else do it, or simply by looking at a picture? Did you know reading the word 'yawn' can trigger you to do it?
So why *exactly* do humans yawn? Turns out that the true answer to the eons-old question as to why yawning happens isn't as obvious as you'd think.
So why do we yawn? Our brains, which take up 20% of the body's metabolic energy, get overheated sometimes. When that happens, they need a quick way to cool off - and yawning is the speedy response the body needs. It's the ultimate thermo-regulator.
This theory is a recent one and has been put to the test by Dr. Andrew C. Gallup, a psychology professor at the State University of New York at Albany. The study found conclusive evidence that the warmer the brain, the more likely the body was to trigger a hearty yawn to cool it off, not unlike an overheated computer kicks on its vents.
Yawning when waking up makes us feel more refreshed, it's speculated, because it helps cool off the brain, which then helps it run more efficiently.
So how does yawning accomplish that, exactly?
When you yawn, you stretch your jaw wide, which directly increases blood flow to the skull. Air rushes through the oral and nasal cavities and cools the blood flow through web of veins throughout. The chilled-out blood makes its way to the brain, effectively lowering the temperature.
"A cooler brain," Dr. Gallup said, "is a clearer brain."
Does seeing someone else around you yawn, or even seeing a picture of someone yawning, elicit one from you in response? If so, that most likely means that you're high in empathy. Georgia Gwinnett College professor Steven Platek demonstrates this using a peculiar method. Through functional magnetic resonance imaging (fMRI) scans, Platek determined that the areas of the brain stimulated during contagious yawning, the posterior cingulate and precuneus, are responsible for processing our own and others' emotions.
“If I see a yawn, that might automatically cue an instinctual behavior that if so-and-so’s brain is heating up, that means I’m in close enough vicinity, I may need to regulate my neural processes,” says Platek.
In short, improving alertness improves the collective ability of the group to survive.Somewhere around 60-70% of people who see someone around them yawn do the same in return, in a complex dance of both empathy and the primal brain that's wired for survival.