FRIDAY, Sept. 4, 2015 (HealthDay News) -- People with psychopathic traits are less likely to catch "contagious yawning" than those with higher levels of empathy, a new study suggests.

Psychopathic characteristics include being selfish, manipulative, impulsive, domineering and lacking in empathy, Baylor University researchers explained.

Contagious yawning refers to yawning when other people yawn, and it is associated with empathy and bonding. It occurs in many social animals, including people, chimpanzees and dogs, the study authors explained in a university news release.

The study included 135 college students, who all completed a lengthy written psychological evaluation. Lead researcher Brian Rundle, a doctoral student in psychology and neuroscience at Baylor University in Waco, Texas, pointed out in the news release that the test doesn't tell specifically whether or not someone is a psychopath.

"It's not an 'on/off' of whether you're a psychopath. It's a spectrum," Rundle said.

Next, the researchers had the students sit in a dimly lit room, and wear noise-cancelling headphones. They also had electrodes placed in several spots on their face to measure their expressions. They were shown brief video clips of people yawning, laughing or with a neutral face.

The researchers found that the less empathy a person has, based on the results of their psychological evaluation, the less likely he or she was to "catch" a yawn.

The study was published online recently in the journal Personality and Individual Differences.

So, should you be worried if someone doesn't yawn after you do?

"The take-home lesson is not that if you yawn and someone else doesn't, the other person is a psychopath," Rundle said. "A lot of people didn't yawn, and we know that we're not very likely to yawn in response to a stranger we don't have empathetic connections with," he explained.

"But what we found tells us there is a neurological connection -- some overlap -- between psychopathy and contagious yawning. This is a good starting point to ask more questions," Rundle concluded.