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Yawns have long confounded scientists: There’s little consensus on why we yawn, what yawns mean and why yawn’s seem to be contagious.

By Stephanie Soucheray

It happens in business meetings, at church, in line at the post office: Somebody yawns and soon enough everyone around them is covering their mouths. Yawns, we’ve been told, are contagious.

And because they can be “caught,” those who yawn after seeing someone else do it have long been considered more empathetic than those who don’t. But new research from Duke University shows that while yawns may be contagious, they have little to do with empathy.

Image courtesy Bjorn Rixman, flickr creative commons

“Yawns were not correlated with empathy levels in our test subjects,” said Elizabeth Cirulli, a professor and researcher at the Duke Center for Human Genome Variation. Cirulli’s work was published recently in the online journal PLoS One.

Cirulli has measured the yawns of more than 300 people after they watched a three-minute video of a person yawning. Each time the test participants yawned, they clicked a button that tallied their wide-open mouths.

“We tested for intelligence, age, gender, sleepiness, energy levels and empathy,” said Cirulli. “And nothing had a big impact. Most of the variation could not be explained, but older people did seem to yawn less.”

Empathy was measured by a standardized survey that asked participants how they thought or felt in a given situation.

Two thirds of the participants demonstrated contagious yawns, with some yawning up to 15 times during the three-minute video. Others resisted the urge to yawn completely. While yawning may be a curious research topic, it’s long been a mystery to scientists, who know very little about why we yawn.

“It can be related to boredom or tiredness,” said Cirulli. “A more recent hypothesis is that it’s cooling the brain.” She said modern science discredits the idea that spontaneous yawning has to do with oxygen levels, and now her work disproves the empathetic nature of contagious yawns.

Sam Kean, a science writer who’s written about yawns, said the subject is ripe for scientific exploration.

“Only humans, chimpanzees and some dogs yawn, so it’s a really fun and mysterious thing to study,” he said.

Kean said that while this study suggests empathy isn’t behind yawns, there are some interesting examples from science that show just how deeply ingrained social yawning is.

“Blind people sometimes contagiously yawn,” he said. “And people paralyzed on one side of their body can yawn and even stretch their arms. Because it originates in the brain stem, [yawns] are a really primitive reflex.”

“Contagious yawns may just be some form of mimicry,” said Cirulli.

Her work will now focus on finding a genetic link between people who yawn contagiously and those who don’t. She said she’s performing genetic analysis on more than 500 subjects to look for variants in the genome associated with yawning.

“The vast majority of genetic research is on disease,” said Cirulli. “I feel like there are a lot of other traits that are very interesting but neglected, and I focus on the ones that are easy to collect. Like yawning.”

Besides yawns, Cirulli works on time perception, facial recognitions and night vision.

“All these things have a really interesting biology,” she said.

And, said Kean, can help us understand the mysterious workings of our brain.

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