New York, Sep 1 (IANS): Ever wondered why even if we are not tired, we yawn if someone else does?

It is because the human propensity for contagious yawning is triggered automatically by primitive reflexes in a brain area responsible for motor function, a research suggests.

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).

The findings showed that our urge to yawn is increased if we are instructed to resist yawning. And no matter how hard we try to stifle a yawn, it might change how we yawn but it won't alter our propensity to yawn.

"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 Georgina Jackson, a Professor at the University of Nottingham.

"The findings may be important in understanding association between motor excitability and the occurrence of echophenomena in a wide range of conditions linked to increased cortical excitability and/or decreased physiological inhibition such as epilepsy, dementia, autism, and Tourette syndrome," added Stephen Jackson, a Professor at the varsity.

For the study, published in the journal Current Biology, the team used transcranial magnetic stimulation (TMS) to analyse volunteers who viewed video clips showing someone else yawning and were instructed to either resist yawning or to allow themselves to yawn.

"If we can understand how alterations in cortical excitability give rise to neural disorders we can potentially reverse them. We are looking for potential non-drug, personalised treatments, using TMS that might be affective in modulating imbalances in the brain networks," Jackson said.

Echophenomena isn't just a human trait, it is found in chimpanzees and dogs too.