Well, University of Nottingham researchers have discovered that the human propensity for "contagious" yawning is triggered by reflexes in the brain, in an area called the primary motor cortex.
The academics explained that yawning is triggered involuntarily when others yawn because of a human trait called echophenomena.
For their study, 36 people were shown videos of people yawning. The researchers then counted the yawns each participant reciprocated and those yawns they fought against. They found the ability to suppress a yawn after someone else does it is "limited" and becomes more difficult if someone tells a person not to do it. In addition, the study found applying electrical stimulation drove the necessity to yawn, which could lead to medical advances.
Accordingly, the study results may help inform research on echophenomena, which can also be seen in a wide range of clinical conditions such as epilepsy, dementia, autism and Tourette’s syndrome.
"This research has shown that the 'urge' is increased by trying to stop yourself. Using electrical stimulation, we were able to increase excitability and in doing so increase the propensity for contagious yawning," said Professor Georgina Jackson. "In Tourette's, if we could reduce the excitability we might reduce the ticks and that's what we are working on."
The researchers added that it's not just humans who have a propensity for contagious yawning - chimpanzees and dogs do it too.
But the exact reason why humans yawn remains unknown to experts, with many theories lacking evidence.
The full study results have been published in the journal Current Biology.© Cover Media