Feeling tired? Even if we aren't tired, why do we yawn if someone else does? Experts have published research that suggests 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.
Their study -- 'A neural basis for contagious yawning' -- has been published in the journal Current Biology. The latest findings show that our ability to resist yawning when someone else near us yawns is limited. And our urge to yawn is increased if we are instructed to resist yawning. But, 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. Importantly, they have discovered that the urge to yawn -- our propensity for contagious yawning -- is individual to each one of us.
Senior author said: "We suggest that these findings may be particularly important in understanding further the association between motor excitability and the occurrence of echophenomena in a wide range of clinical conditions that have been linked to increased cortical excitability and/or decreased physiological inhibition such as epilepsy, dementia, autism, and Tourette syndrome."
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). And it's not just humans who have a propensity for contagious yawning -- chimpanzees and dogs do it too.
Echophenomena can also be seen in a wide range of clinical conditions linked to increased cortical excitability and/or decreased physiological inhibition such as epilespsy, dementia, autism and Tourette syndrome.
The neural basis for echophenomena is unknown. To test the link between motor excitability and the neural basis for contagious yawning the research team 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.
Another author said: "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. In Tourettes if we could reduce the excitability we might reduce the ticks and that's what we are working on."