Why Is Yawning Contagious After Lunch?

After a substantial lunch at work, you head into a meeting with your colleagues. One person begins to yawn, followed by another, and before long you are yawning too.

Numerous biological theories have been proposed to explain this response, but where does scientific agreement stand?

Yawning is universal: it is seen from a very early age in humans and across many vertebrate species, including wolves and parrots. Yet why are we so inclined to yawn after watching somebody else do so?

Its persistence across so many species over such a long period suggests that yawning may be an essential mechanism for survival. But what function does it actually fulfil?

Why do we yawn?

There is no lack of theories, among scientists and the wider public alike. Suggestions include oxygenating the brain, controlling body temperature and sending a social signal.

The popular belief that yawning boosts the brain's oxygen supply has not been demonstrated. A further theory proposes that it helps us remain attentive, although no agreement has been reached on that explanation either.

A more firmly established connection is the one between yawning and the circadian rhythm, or biological clock.

Most yawns happen while we are resting, particularly around the times when we wake up or drift off to sleep. More specifically, they tend to occur when the body is less vigilant, such as when it is digesting a meal.

Could yawning be a means of communication?

While the underlying causes of yawning still await confirmation, its "contagious" quality is producing important findings in fields ranging from biology to social psychology.

Yawning may have a significant social role. Ostriches, for instance, use it to bring group behaviour into sync. Like humans, they commonly yawn as they move from wakefulness to rest, and in the opposite direction.

In this way, a yawn may indicate a shift in activity or alertness. It can ensure that every member of a group is awake or resting at the same moment, improving collective safety and preserving the group's rhythm.

Contagious yawning and group synchronisation

Nevertheless, yawning contagion appears to be mainly a human trait, apart from a small number of exceptions, including chimpanzees and lion monkeys.

This particular feature supports the view that, beyond any strictly physiological role, human yawning is a form of non-verbal communication. The leading hypothesis is that it helps coordinate behaviour within a group, much as it does among ostriches.

Watching or hearing another person yawn activates brain regions associated with imitation and empathy, notably through mirror neurons.

These neurons respond when actions are observed – for instance, when a child copies a parent's movements while tying their shoes. Some brain areas specifically implicated in contagious yawning, however, belong to neural networks connected with empathy and social interaction.

Is there a predisposition to contagious yawning?

Empathy seems to be central to how susceptible someone is to contagious yawning. People with social disorders, including autism or schizophrenia, appear less likely to pick up yawns from others.

Research also indicates that outside influences, such as breathing and body temperature, may respectively decrease and increase contagious yawning.

This finding strengthens the possibility that the apparent contagion is overstated. Studies frequently observe people in groups, and that setting may affect the rate of yawning recorded. It suggests that the trigger may not necessarily be watching someone yawn, but instead the group's presence and the interactions taking place within it.

So, if you yawn after a colleague does following lunch, their yawn may not be what influenced you. The shared circumstances – having enjoyed a filling meal together, in this case – may simply be what causes the synchronised response.

Astrid Thébault Guiochon, Engineer and Lecturer, Université Lumière Lyon 2

This article is republished from The Conversation under a Creative Commons licence. Read the original article.