Contagious Yawning and The Mirror Neuron System
A team of researchers led by Nicholas Cooper, University of Essex, UK, have found that the contagiousness of yawning might have much to do with the human mirror neuron system.
“Contagious yawning” refers to the phenomenon whereby simply hearing or seeing another person yawn, even thinking about or reading about yawning, can trigger yawning in a person.
Research has found that 40-60% of people are susceptible to the contagious yawn.
To date, research has explained this finding in terms of empathy. Thus, the more empathetic one is, the more one will be willing to yawn when yawning is primed. To extend this, one must imagine some sort of mechanism that connects the visualizing of the yawn which then triggers a like-response. This is where the mirror neuron idea comes to play.
Mirror neurons were originally discovered in monkeys and are still subject to ongoing debate as to their function and origin.
However, one way to test this idea is with the help of the electroencephalogram (EEG) to measure changes in mu activation during the observation of yawns. Previous work has found that suppression of mu is a useful index of motor neuron activation and is more sensitive in those with higher empathy.
In the current study, the experimenters tracked subjects EEG as they viewed 3-second long video clips of people either yawning or gaping their mouths with no sound track.
In two experiments, results found that there was greater mu suppression for yawns that for the control. This was found in the right motor and premotor areas of the brain and was particularly strong in those scoring higher in traits of empathy.
In the third experiment, subjects listened to audio recordings of yawns as well as the scrambled version of the same yawns. Again, the results showed the same suppression in the mu for yawns over the controls. Levels of empathy also played a strong role in this result.
“The results from these experiments support the notion that the hMNS [human motor neuron system] is involved in contagious yawning, emphasize the link between contagious yawning and empathy, and stress the importance of good control stimuli,” say the researchers.
Cooper, Nicholas R.; Ignazio Puzzo; Adam D. Pawley; Ruby A. Bowes-Mulligan; Emma V. Kirkpatrick; Pavlina A. Antoniou and Steffan Kennett. Bridging a yawning chasm: EEG investigations into the debate concerning the role of the human mirror neuron system in contagious yawning. Cogn Affect Behav Neurosci . 2012. 12:393–405.