Lead study author Brian Rundle says the study came about after he'd had a theory about psychopaths yawning less often than non-psychopaths, due to the popular belief that catching someone's yawn is related to empathy, which is one of the main things that psychopaths are said to be lacking.
Rundle and his team tested 135 students to see where they fell on the psychopath spectrum and then placed electrodes on the students while showing them a computer videos of people yawning, laughing, and just sitting there, to see how often they had reactions like yawning in response.
They found that people who had less empathy were less likely to yawn when someone else did, which doesn't exactly make them psychopaths, since Rundle says, "We know that we're not very likely to yawn in response to a stranger we don't have empathetic connections with" but adds that this is just a great starting place to do further research.
So don't go diagnosing your non-yawning friends as psychopaths just yet, but also keep an eye out because hey, you never know.
This article originally appeared on Cosmopolitan.com. Minor edits have been made by the Cosmo.ph editors.