Why is Yawning So Contagious?
Scientists don’t exactly know yet, but here are some theories
Does looking at a person yawning make you want to yawn? There is an increased propensity to yawn after somebody else does due to a phenomenon called ‘contagious yawning’. And when this urge to yawn comes about, it’s almost impossible to stifle it.
This urge is so easy to trigger that the mere sight of the word ‘yawn’ may in fact provoke a yawn. It’s also not uncommon to witness cross-species yawning contagion — dogs are known to yawn at the sight of human yawns, and vice versa. A Duke University study in 2014 enrolled 328 people and asked them to watch a 3-minute video of people yawning. On average, participants yawned between zero and 15 times, and 222 respondents contagiously yawned at least once.
I yawned on numerous occasions in the making of this article. I’m not sure if it was the catalog of footages and images I chanced upon during research of this article, or by constant exposure of the word ‘yawn’, but this phenomenon is something that really bugs me. Nothing — even the virus — seems to be able to spread as effectively as a yawn.
And this question has apparently bugged scientists for years too. So far, there is no one scientific consensus on why yawns spread the way they do. Luckily, there are set of theories that could help explain this beguiling phenomenon.
“A yawn might be a special kind of respiration, one that builds up oxygen quickly, while expelling carbon dioxide, even more than a deep breath”
Before we get to that, it’s fair to first ask ourself the fundamental question of why we yawn in the first place. Douglas Parham, a speech scientist at Wichita State University, says that yawning occurs as a way to remove excess carbon dioxide from our lungs. “When humans are tired, we stop taking deep breaths, which causes a build-up of carbon dioxide in the body”, says Parham. “A yawn might be a special kind of respiration, one that builds up oxygen quickly, while expelling carbon dioxide, even more than a deep breath”.
James Giordano, a neuro-ethicist and neuroscientist at Georgetown University adds that the state of fatigue, besides increasing carbon dioxide stores in the body, can be mirrored by a increase in a chemical compound called adenosine, which act as ‘yawn-gates’. “These chemicals send out a signal that triggers a yawn”, claims Giordano. “By yawning, we compress the muscles of the face, driving oxygen-enriched blood to the brain”.
Another 2014 research suggests that yawning may be one form of the brain’s cooling mechanism, due to counter-current heat exchange with the deep inhalation of ambient air.
Now the reason yawns are so contagious are still an area of much debate, but one theory that exists in science is echopraxia. Essentially, the word translate to ‘automatic imitation of another’s actions’. Like crossing your legs when your conversation partner crosses theirs, or scratching your head when someone in front of you does, it’s an example of non-conscious mimicry.
Non-conscious mimicry is thought to occur due to some preformed primitive reflex embedded within our primary motor cortex, though the neural basis for this phenomenon is yet unknown. The specific working units of this reflex is hypothesised to be mirror neurons, neurons that fires both when someone acts and when that someone observes the same action performed by another.
This neuron essentially mirrors the behaviour of the opposing subject, as though the observer were itself acting. Mirror neurons are thought to be a critical aspect of learning and self-consciousness. In several other studies, fMRI scans showed an increased mirror neuron activity after witnessing a yawn.
On a community level, this ensues like a domino effect, where the effect of a reflex (the yawn) doubles as a trigger for another yawn, cyclo-propagating this reflex cycle. This chain of reaction effectively only stops when there is nobody else left to witness the yawn.
Another theory surrounding yawn contagion talks about empathy, which is again related to the fixed-action pattern we saw in non-conscious mimicry. This 2013 article reveals that dogs were more susceptible to yawns when they witness their owners yawn (compared to strangers). The article’s researcher hypothesises that contagious yawning in dogs is emotionally connected in a way similar to humans.
In other words, empathy gets a sliver of the pie when it comes to yawning contagion. And this is apparently seen in humans as well. One article showed that yawns are induced more frequently among friends than strangers. In addition to that, children with autism are less likely to yawn contagiously, which is thought to be due to the disease’s association with social and communication difficulties. (and hence empathetic capabilities)
And the reason for this? One idea suggests that this seemingly banal trait could’ve been crucial for our prehistoric survival.
“If getting sleepy and climbing up into the trees as a refuge safe from predators was practiced by our ancestors, and if yawning facilitated that behaviour, it makes sense yawning would be evolutionarily selected for”, said Euclid Smith, an anthropologist at Emory University. “He who yawns last might be dinner for a predator.”
The neural pathway for such a behaviour to develop could by chance, be the same network that is responsible for non-conscious mimicry — the mirror neurons. The complexity of this neural matrix is one of the major hindrances towards stripping bare this phenomenon.
As I stated in the earlier paragraphs of the article, nobody knows why yawning is such a catchy quirk. The current consensus postulates that its catchiness may be useful to coordinate the level of alertness in a group, be a byproduct of empathy — signalling warmth and fellowship towards the people closest to us, which is beneficial at maintaining relationships — or it could be a delicate interplay of both things at once.