Yawning is a very characteristic gesture not only of humans, but also of a large number of animals. Despite this, there is no common explanation for why it occurs or why it is so easily contagious.
Why we yawn: main theories
"We can put a man on the moon, but we don't understand the function of yawning." This seemingly exaggerated statement is entirely true and was made by Gary Hack, a professor at Baltimore State University (Maryland, USA). He wasn't at all off the mark or out of context: despite the numerous advances made in the world of science, we still haven't reached a consensus on why we yawn.
There are many theories attempting to explain this action, each with enough proponents to keep the issue from reaching a consensus. The most recent theory , however, which seems to be gaining considerable traction within the medical community, comes from this professor and his research group, who propose that it's a movement to pump air into the brain and thus lower its temperature.
When we yawn, the walls of the maxillary sinus expand and contract, allowing air to flow to our brain to cool it , thus maintaining our alertness. This effect has been demonstrated in laboratory studies with rats, in which a decrease in brain temperature was observed after yawning.
However, this is not the only theory, as we mentioned. Another similar one, but with a different purpose, is proposed by the Erie Medical School (Pennsylvania), where it is believed that the paraventricular nucleus of the hypothalamus—responsible for generating oxytocin , which triggers certain bodily contractions and stimulations—causes yawning when it detects that blood oxygen levels are insufficient, thus prompting the intake of a large amount of air through the mouth.
It is also believed that yawning is nothing more than a reflex with no benefit for the adult, but one that we retain from our time in the womb . Fetuses also yawn, and it is thought that this could be to keep their respiratory and digestive tracts clean, as they are surrounded by amniotic fluid. Obviously, we are no longer surrounded by this substance, but we would retain the gesture.
Yawning is also thought to be a response to stress . Yawning temporarily increases levels of cortisol, a hormone associated with stress, which could explain why some people yawn during times of high stress or anxiety, helping to keep them more awake and active.
And why the hell is it contagious?
It is another of the great questions that, of course, are linked to the origin of the yawn. Why is it so terribly contagious? What makes us yawn when we see someone else doing it?
Somewhat in line with the theories explained earlier, it's believed that contagion often occurs simply because we're in the same room (with the same temperature) as someone else, and they've simply gotten there first to "refresh their brain," something we'll also do due to the same environmental conditions . However, this wouldn't explain why yawning can be contagious, even just by watching someone yawn in a video.
There are theories that talk about imitation or synchrony between groups (we do it as a reflexive act of imitation between equals or to "synchronize" within the group, also reflexively), but there is one that is especially relevant and has to do with empathy.
According to some studies, we yawn because we put ourselves in the other person's shoes; it's a response that shows we understand how they feel. It might sound strange, but several studies point in this direction. It has been shown that yawning activates brain circuits that are also involved in empathy. Furthermore, 60% of the people who are more easily infected with yawns tend to show higher empathy scores on certain tests. Want another interesting fact? Children don't yawn contagiously until around age 5, coinciding precisely with the phase when they begin to develop their empathic capacity.
Finally, there is a study that suggests yawning as a form of communication . It indicates that people with autism, who experience difficulties in social communication, are immune to contagious yawning, supporting the theory of yawning as a primitive form of group communication. However, it has been shown that people with autism, rather than lacking empathy, develop a different kind of empathy, but this could still lend support to this theory.
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This idea of ​​yawning as a communication tool could be related to the fact that we are more easily infected if the person yawning is a family member than if it is a friend, and much more so than if it is a stranger.
Come on and now, admit it: how many times have you yawned reading this article?