Here's a new test to see if you're dating a psychopath: when you yawn, pay attention to whether or not he or she yawns back. According to new research, if they don't yawn back, they might be a psychopath.

A study conducted by psychologists from Baylor University in Texas suggests that people who are more coldhearted are less likely to engage in the natural behavior of "catching" yawns.

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Psychopaths are characterized by a lack of empathy and abnormal social behaviors, and mimicking yawning is a sign of empathy and a form of social bonding.

"Psychopaths are partly defined by lack of empathy and compassionate understanding of the feelings of others," says Brian Rundle, a doctoral researcher at the university and an author of the study. "The fact that they aren't able to contagious yawn suggests that the mechanics involved in the empathy process aren't functioning normally."

Researchers asked 135 students to fill out a questionnaire used to identify psychopathic personality traits like coldheartedness, Machiavellianism, egocentricity, callousness, and impulsivity. Afterward, students watched videos of people making various facial movements, including yawning. Their findings matched the hypothesis - the study found that those who possessed more psychopathic qualities were less likely to "catch" a yawn.

While the study's findings don't mean you're a psychopath if you don't contagious yawn, it still gives neuroscientists a better understanding of both psychopathy and yawning independently, as well as in relation to each other.