A psychopath can be identified by merely yawning at the person in question, suggests the findings of a latest study conducted by a team of researchers at the Texas Baylor University. According to the team, psychopaths are almost never affected by contagious yawning, that is, they do not feel the need to yawn if they see the other person doing the same.

A majority of individual end up yawning when they see someone around them show symptoms of tiredness. However, the researchers argue that people with psychopathic traits are far likely to be affected by whether the person sitting next to them is showing signs of tiredness or not.

During the study, the researchers analyzed a group 135 students for traits related to narcissism, cold-heartedness, egocentricity and rebellious nonconformity. Considering that people who see others yawn are likely to yawn themselves, the researchers showed clips of people with different facial expressions to the students.

The facial postures shown in the video also included people who were yawning. The researchers found that students who showed high cold-heartedness were less likely to yawn. The complete details of the study have been published in the journal Personality and Individual Differences.

"One of the biggest lines of evidence is that contagious yawning is very much related to empathy,” said Brian Rundle, a PhD scholar associated with the study. "While this is a really interesting finding, it doesn't mean that if you're not affected by a contagious yawn there's something wrong with you."

Yahoo UK reports that serial murderers such as Fred West, Ian Brady and Jeremy Bamber have some of the traits that are common among them. All three individuals are compulsive liars, lack empathy and are fantasists.