Study reveals why yawning is contagious

Researchers at the University of Nottingham in the United Kingdom suggest that the propensity to automatically yawn when we watch someone else yawning, could be triggered by primitive reflexes in the primary motor cortex — the area of the brain associated with motor function.

The study of contagious yawning was another stage in the ongoing research into the underlying biology of neuropsychiatric disorders, and the search for new methods of treatment, by the researchers.

The latest findings from their research show that our ability to resist yawning when someone else near us yawns is limited, and that the urge to yawn is increased if we are instructed to resist yawning. Importantly, they also discovered that the urge to yawn — our propensity for contagious yawning —  is individual to each one of us.

The findings from the study may be particularly important in understanding further the association between motor excitability and the occurrence of echophenomena. Contagious yawning is a common form of echophenomena, which also includes the automatic imitation of another’s words (echolalia) or actions (echopraxia). Echophenomena can also be seen in a wide range of clinical conditions linked to increased cortical excitability and/or decreased physiological inhibition, such as in epilepsy, dementia, autism and Tourette syndrome.

The neural basis for echophenomena is so far unknown. To test the link between motor excitability and the neural basis for contagious yawning the researchers used transcranial magnetic stimulation (TMS). The use of TMS allowed the researchers to quantify motor cortical excitability and physiological inhibition for each participant and predict the propensity for contagious yawning across all the volunteers.

For the study, 36 adults were shown video clips of someone yawning and then instructed to either resist yawning or to allow themselves to yawn. Using electrical stimulation the team was also able to increase excitability and consequently the urge to yawn among participants. The results from the study showed that the ‘urge’ to yawn is increased by trying to stop yourself. Using electrical stimulation to raise excitability level also increased the propensity for contagious yawning.

The TMS measures proved to be significant predictors of contagious yawning and demonstrated that each individual’s propensity for contagious yawning was determined by the cortical excitability and physiological inhibition of their primary motor cortex.

Researchers say that if they could understand how alterations in cortical excitability give rise to neural disorders, then they could potentially reverse them and thereby modulate imbalances in brain networks.