The contagious yawn. It's something we can all relate to. Someone in our general vicinity let's out a big old yawn and then no matter how had we try, moments later we're in on the act too.

You've probably wondered why this happens, especially considering the majority of the time you're not even tired. Well a new study released by Pyschology Today has shed some light on the issue.

One of the key findings of the study is that empathy is a major factor when it comes to people catching yawns. Given that a lack of empathy is one of the defining traits of psychopaths, it stands to reason that people defined as such would be immune to the power of the contagious yawn.

The study comes courtesy of researchers at Baylor University, who had 135 subjects take a test called the ‘Psychopathic Personality Inventory-Revised’ (PPI-R), before putting them through a contagious yawn experiment.

So the next time you're yawning and your partner doesn't follow suit, you might want to re-evaluate your relationship!