As is widely known, most people will yawn if someone around them yawns and shows signs of fatigue. The students were shown video clips of people using different facial expressions, including yawning.

The ones who scored highly for cold-heartedness were the ones less likely to yawn. 

Brian Rundle, a PhD student involved in the study, told The Times: ‘One of the biggest lines of evidence is that (contagious yawning is) very much related to empathy.

‘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.’

‘There’s some evidence that to show that in baboons or dogs or chimps the alpha male tends to yawn first,’ he added.