We all do it. But why? Is it because we're bored? Tired? Growing our brains?
That's right. In a paper published on Tuesday, psychologist Andrew Gallup and his colleagues reported on a study of 109 individuals hailing from 19 species, including humans, elephants, mice and monkeys. The results?
"Analyses revealed that average yawn duration is a robust predictor of brain size and cortical neuron number across mammals," states the paper.
In other words, yawns just may promote brain growth--and activity.
Gallup has been studying the science of yawns for years. Back in 2007, he proposed what is now known as the "thermoregulatory theory of yawning." An article recently published on Scientific American's website explains:
[The theory] holds that opening our jaws and sucking in air cools the brain, something other labs have found support for. Yawning might also kick the brain out of its so-called default mode--a sort of background humming-along state--and into a paying-attention state by increasing the circulation of cerebrospinal fluid, a 2014 paper found.
Yawning can increase blood flow to the brain via jaw stretching and the deep inhalation of air, replacing warmed blood in the brain with cooler blood from the heart, and allowing heat exchange with the ambient air, which is almost always cooler than body temperature.
"Longer and/or [more] powerful yawns should provide greater physiological effects," Gallup said.
If yawns really do increase brain size and activity, the question naturally follows:
How can I make myself yawn?
You've surely heard of "contagious yawning," or at least the idea behind it. Studies indicate that seeing another person yawn increases the likelihood that you follow with a yawn of your own.
So, if you're interested in growing the power of your good old gray matter, try watching the video below. It shows 50 full yawns--and it may just get you going.
If it doesn't seem to work at first, don't despair. I didn't actually yawn while watching the video (except for a few half-yawns that didn't count). But since watching it, I actually can't stop yawning.
And I feel myself getting smarter by the second.