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If you’ve been wondering if that nasty, aggressive coworker is actually a psychopath in disguise, there might be a little clue: Try yawning and see if he or she yawns back.
People high in psychopathic personality traits often don’t “catch” the contagious yawn, according to a report published in Personality and Individual Differences. The reason is they aren’t particularly empathetic, said the study’s lead author, Brian Rundle, a behavioral scientist at Baylor University.
Contagious yawning — or yawning when you see someone else do it — is a very primitive form of communication and bonding, Rundle said. And according to a new study published in the journal Current Biology, it's true: If someone near you yawns, you're more likely to yawn, too (psychopaths excluded). It's not just humans who do this, chimpanzees and dogs do it, too. The study also found that it's difficult to resist yawning if we're instructed to stop.
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Rundle is quick to point out that diagnosing psychopaths is more complicated than just watching to see if they yawn after you do. That’s because the likelihood that someone will catch a contagious yawn is dependent on a number of factors, including age — you’re less likely to yawn after someone else if you’re older — and familiarity — you’re more likely to yawn after someone else if you know the person.
Still, he said, whether it’s in the boardroom or the bedroom, the study shows that you are more likely follow up on someone else’s yawn if you score low in psychopathic traits.
For the study, Rundle and his colleagues rounded up 135 college students and had them fill out a standard assessment of psychopathic traits, called the Psychopathic Personality Inventory. Questions were designed to ferret out traits such as cruelty, selfishness, impulsivity, aggression and empathy.
Normal folks fall in the 50 percent range, Rundle said, adding that there were some students who scored very low and some who scored up in the 90th percentile.
You might immediately think of serial killers burying bodies in the basement when you think of psychopathy, but Rundle said, “people high in psychopathic traits may just be hard to connect with, it doesn’t mean they are malicious individuals.”
The study volunteers were next asked to sit in front of a computer screen in a dark room wearing noise-canceling headphones as they watched 10-second videos of three different facial expressions: yawning, laughing or neutral. The volunteers also wore electrodes below their eyelids, next to the outer corners of their eyes, on their foreheads and on their index and middle fingers so that the researchers could monitor responses to the videos.
The volunteers who were lower in psychopathic traits were nearly twice as likely to yawn as those who were high in those traits. Still, there were individuals who were low in psychopathic traits who didn’t yawn at all. That indicates more research is needed with a larger number of volunteers, Rundle said.
While scientists don’t know exactly why we yawn, they do know what parts of the brain are involved in the process, said Steven Platek, an associate professor of psychology at Georgia Gwinnett College, who has spent some time studying yawning, but is unaffiliated with the new research.
“What’s interesting is the parts of the brain that are involved — the posterior cingulate and the precuneus— in yawning are also involved in instinctual kinds of empathetic processes,” Platek said.
“Scientists used to think that yawning was a way of dealing with oxygen deficiencies in our blood. That’s been disproven. The current thinking is that it’s a mechanism to help cool the brain. And the yawn is like a kick into action for the brain, as opposed to a sign of boredom.”
Platek isn’t surprised to see a link between psychopathy and immunity from the contagion of yawning, since there have been studies showing that empathy plays a role in whether or not you’ll be prompted to yawn when you see someone else doing so.
“I tell my friends jokingly, if you’re looking for a romantic partner, one of the things you can do is test them for contagious yawning,” Platek said. “It’s associated with empathy and the one thing you want is someone empathetic and caring, i.e., not someone who is sociopathic.”
Liz Cirulli, an assistant professor of medicine at Duke University, said the new findings are interesting, but agrees more research needs to be done. Her own research on contagious yawning has shown we’re less susceptible the older we get. But that’s just part of the answer to why some people are more impervious to contagious yawning, she said.
Cirulli said she’s been studying both yawning and psychopathy.
“I never thought of linking them up before,” she said. “But it makes sense.”
This story was originally published in August 2015.