Why is yawning contagious?

We're at a boring family reunion. Out of politeness we try to maintain our composure and pretend that we care minimally about what our older relatives talk about.

But the little ones in the house don't care about composure. They get bored and have no qualms about yawning as a manifest act of such a tedious meeting. The invisible breath of air travels through the room. Little by little, he approaches us. It takes shape from the depths of our interior and, without being able to avoid it, we answer the yawn by imitating it.

While the one who was speaking looks at us with an indignant face, we wonder... Why is yawning contagious? Let's find out below.

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Why do we spread yawning?

Yawning is a human and not so human act that, despite the fact that it has aroused the interest of the scientific community since science is science, it remains quite mysterious why it originates, and even more so why it is contagious However, some things are clear about such a peculiar involuntary act.

The first thing is that we manifest it very early, even before being fully formed, in the womb. You can already see how the fetus yawns just 20 weeks after conception.

Also, human beings are not the only ones who yawn. It has been seen that animals very close to us also yawn, as is the case with chimpanzees and dogs, respectively. Curiously, it has also been observed in fish, birds, wolves and elephants, animals that, to a lesser or greater extent, have very clear social behavioral patterns.

Although the general culture already came to indicate that we yawn more when we are about to leave to sleep and just woken up, scientific research has been in charge of confirming this assumption. Besides, we also yawn when we feel hungry and, of course, when we are very bored.

But what is surprising about yawning is its high degree of contagion, despite the fact that they do not physically exist, they are just actions. It has happened to almost all of us that someone around us yawns and, without being able to avoid it, we start yawning with him. This is not strange at all, given that it is noted that close to 60% of the population is sensitive not only to act of seeing others yawn, but is also sensitive to hearing others yawn and even reading the word "yawn". At this point, how many yawns have you already had?

Yawning theories

Let's go by parts. Before understanding how yawning is contagious, you need to understand why it is caused in the first place..

At first, yawning does not seem to have a good or bad effect on us. If it were something harmful, sooner or later we would have noticed some disadvantage associated with yawning and, without digging too hard, it doesn't seem to offer us any advantage.

However, taking into account that this involuntary act occurs in other species and that, therefore, has survived throughout evolutionary historyIt has to have some use.

It is for this reason that in the scientific community up to three theories have been raised, with enough support, to explain why yawning occurs.

1. The oxygenation theory

Already before our era the Greek physician Hippocrates of Cos (460 a. c. - 370 B.C. C.) supported the idea that we yawn as a mechanism to eliminate the harmful air that we accumulate inside. In a certain way, it seems that he was not going too far wrong.

The yawning oxygenation theory defends the idea that when our blood oxygen levels decrease, drowsiness occurs. To counteract it, the brain makes you yawn in order to get a lot of air into the body, to quickly raise the levels of the gas of life.

However, despite being quite logical, this theory has its detractors, basically due to the existence of another mechanism that seems to be very effective for this purpose: breathing fast, as happens when we do the sport.

If the levels of oxygen in the blood are reduced, it would be logical to think that, rather than yawning, the body would order to speed up the respiration, a process that implies a greater supply of oxygen to our bloodstream and that is relatively easy to check.

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2. The Activation Theory

As we have already seen, and almost a knowledge of general culture, it is the fact that yawning is known to be more frequent before and after sleep. That is, they occur when we feel very sleepy.

The idea behind the arousal theory is that you yawn to increase your alertness. That is, our brain sends us a message that we should be more on the lookout.

However, and despite the fact that there are many investigations that suggest that this theory could be true, it is still quite doubtful that alertness levels before and after yawning are significantly different. It's not that we yawn and are as alert as if we had just had a cup of coffee...

3. The theory of thermoregulation

Although the other two theories have some scientific support, the theory of thermoregulation is the one that has gained the most strength. This theory defends that yawning regulates the temperature of the brain, by way of cooling.

This makes sense, since it has been observed that the body temperature is just the highest of the day and that, by yawning, we would be able to reduce it and make our brain work better.

Also It has been observed that if the ambient temperature is warm, people yawn more, while low temperatures have the opposite effect. In fact, it has been seen that putting damp cloths in very cold water on the forehead makes yawning practically disappear.

Causes of this phenomenon

Although it has been seen that yawning is present in many species, the contagion of this involuntary act is somewhat less common.. Besides humans, other species such as dogs, wolves, chimpanzees, different types of fish and birds, and also elephants can catch yawning. Based on the fact that most species in which yawning is contagious also have complex social structures, it has been suggested that yawning may have a relational function.

1. Communication and synchronization

One of the hypotheses about yawning is that it is a communication and synchronization mechanism between individuals of the same species. That is, it would serve as a way to organize collective behavior, coordinating the behavioral patterns of group members.

This makes sense since yawning is not the only thing that is contagious. In the human case and also in dogs, if you see someone eating, you feel like doing it, and if you see someone move, you are more prone to not sitting still. The yawn would serve to put the group in sync either by maintaining the degree of activation or by making sure that everyone thermoregulates correctly.

2. Empathy

As surprising as it may seem, it could be that the degree of empathy is behind how contagious yawning is. In this case it would not be just a mechanism to make the rest of the group imitate it and thus synchronize, but a way of being able to tune behaviorally and emotionally with others.

Using neuroimaging techniques, it has been discovered that yawning activates the same neurological mechanisms involved with empathy., in addition to activating the well-known mirror neurons, cells specialized in mentally replicating the movements we see in others, allowing motor learning.

Bibliographic references:

• Bartholomew AJ, Cirulli ET (2014) Individual Variation in Contagious Yawning Susceptibility Is Highly Stable and Largely Unexplained by Empathy or Other Known Factors. PLOS ONE 9(3): e91773. https://doi.org/10.1371/journal.pone.0091773
• Rossman, Z. et al (2020). Contagious Yawning in African Elephants (Loxodonta africana): Responses to Other Elephants and Familiar Humans. Front. vet. Sci., 1-8.
• Gallup, A. c. and Gallup, G. (2008) Yawning and thermoregulation. Physiology & Behavior, 95(1–2, 3) 10-16.
• Gallup AC, Eldakar OT. (2013). The thermoregulatory theory of yawning: what we know from over 5 years of research. Front Neurosci. 2;6:188. doi: 10.3389/fnins.2012.00188.
• Guggisberg AG, Mathis J, Schnider A, Hess CW. (2010) Why do we yawn? Neurosci Biobehavi Rev. 34(8):1267-76. doi: 10.1016/j.neubiorev.2010.03.008.
• Guggisberg AG, Mathis J, Hess CW. (2010). Interplay between yawning and surveillance: a review of the experimental evidence. Front Neurol Neurosci 28:47-54. doi: 10.1159/000307079.