The average adult yawns about 20 times a day. But why? We can’t all be that tired.
The science behind yawning is much more complex than just a few hours too little sleep.
Here are some facts about why we yawn and why yawning can be contagious — even over the phone and even between dogs and humans.
This reflex occurs most often due to what’s called state change — during periods of transition between waking and sleep. Think of a cartoon character starting the day with a hyperbolically large yawn, complete with outstretched arms and a gaping mouth.
State change isn’t the only known cause, though. We also yawn to promote alertness, or cortical arousal.
And sometimes it’s due to increases in brain temperature.
So we yawn to wake up and cool down our brains.
One hypothesis about contagious yawning cites a phenomenon called echopraxia in which people see a certain behavior and, if they’re sensitive to it, will mimic it. This is because of mirror neurons in the brain.
Sme research indicates that it’s an evolved form of synchronized group behavior: Of our 20 yawns, many of them occur during shared periods of transition throughout the day.
Contagious yawning also could be a tool for increased vigilance. Since yawning can prompt alertness, perhaps we evolved to use one another as indicators of when we should yawn to trigger a more vigilant brain.
When other people yawn, we also become more sensitive to our own physiological state — maybe we’re tired and didn’t know it until someone else’s yawn gives us a trigger.
Research shows yawning is extra-contagious when it comes with a sound effect: that “ahhh” noise a lot of us make. So if you hear that over the phone, it might be enough to trigger a sympathetic yawn.
If a dog or cat is socialized in the same house as you, you might experience contagious yawning with your pet. Lots of other animals also experience contagious yawning. Research shows that highly social species experience this.
Recent research suggests that the variability of contagious yawning could signal levels of empathy or ability for empathetic processing. This would seem to be supported by the fact we’re more likely to experience contagious yawning with friends than strangers and that yawning becomes contagious for us at 4 or 5 years old when we begin to understand others’ emotions.
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