London, Sep 1 (PTI): Ever wondered why we catch a yawn even if we are not tired? An area of our brain responsible for motor functions may be to blame, a study suggests.
Researchers at the University of Nottingham in the UK have found that our ability to resist yawning when someone else near us yawns is limited. Our urge to yawn is increased if we are instructed to resist yawning.
However, no matter how hard we try to stifle a yawn, it might change how we yawn but it would not alter our propensity to yawn, they said.
The study suggests that the human propensity for contagious yawning is triggered automatically by primitive reflexes in the primary motor cortex - an area of the brain responsible for motor function.
The researchers also found that the urge to yawn - our propensity for contagious yawning - is individual to each one of us.
"These findings may be particularly important in understanding the association between motor excitability and the occurrence of echophenomena in a wide range of clinical conditions linked to increased cortical excitability and decreased physiological inhibition such as epilepsy, dementia, autism, and Tourette syndrome," said Professor Stephen Jackson, who led the study.
Contagious yawning is triggered involuntarily when we observe another person yawn. It is a common form of echophenomena - the automatic imitation of another's words (echolalia) or actions (echopraxia).
It is not just the humans who have a propensity for contagious yawning - chimpanzees and dogs do it too.
To test the link between motor excitability and the neural basis for contagious yawning, the researchers used transcranial magnetic stimulation (TMS).
They recruited 36 adults to help with their study. These volunteers viewed video clips showing someone else yawning and were instructed to either resist yawning or to allow themselves to yawn.
The participants were videoed throughout, and their yawns and stifled yawns were counted. In addition, the intensity of each participant's perceived urge to yawn was continuously recorded.
Using electrical stimulation they were also able to increase the urge to yawn.
"This research has shown that the 'urge' is increased by trying to stop yourself," said Georgina Jackson, a professor at Nottingham.
"Using electrical stimulation we were able to increase excitability and in doing so increase the propensity for contagious yawning," said Jackson.