Yawning is this universal behavior, common to all vertebrate species. This particular movement results in a deep breath, preceding a brief breath hold and an exhale. From fish to birds, monkeys and horses, all are capable of yawning. So why are we yawning?

Known to be the oldest behavior of living things, and one of the few common to all vertebrates living on Earth, whether in the air or in the water, yawning is the respiratory cycle reaching its climax. In humans, the period we yawn the most is the… fetal period.

The successive movements of a yawn are:

• a deep and full breath, through the mouth wide open;
• the pharynx, area of ​​the throat connecting the nose to the mouth, stretches to its maximum;
• simultaneously, the larynx, a conduit which connects the throat to the trachea and containing the vocal cords, opens by spreading the vocal cords;
• after inspiration, the thorax filled, there is a brief stop of breathing, and an equally brief closing of the eyes;
• expiration, often noisy and slow in humans, is accompanied by relaxation of the muscles when the mouth is closed. The larynx falls back into place and spreads a feeling of general well-being.

But yawning is not just a broad, relaxing inhale and exhale: it is a general muscle stretching movement of the respiratory muscles, from the diaphragm to the intercostals, to the muscles of the face and neck, passing through. by the throat muscles (pharynx, larynx).

There is also a decrease in hearing during this movement, since the Eustachian tubes located in the ear canal open. Sometimes a tear can bead on the eyes, due to the compression of the tear duct when stretching the face.

This movement, much more complex than you might think, therefore encompasses a whole series of movements that can be qualified as reflex, because it is not done voluntarily. However, a yawn can be suppressed (more or less effectively) if it occurs at a socially inopportune time. Its intensity is also adjustable according to our desire to relax and stretch.

Stimulate our vigilance

There is a widely held misconception that yawning is a “call for oxygen” from the brain: this idea is false. However, yawning allows us to activate our vigilance and our concentration, especially at times when our awakening changes: when we wake up, after or before eating, or when we are tired, and after a period of rest.

Make the stress go away

This particular stretch thus stimulates our vigilance but also serves us as a method of intense relaxation. So much so that some athletes or students before an exam would indulge in yawning in order to arrive at the event totally relaxed and stress free.

Show empathy to others

Everyone has experienced it at least once. In a work meeting, or with family or friends, when someone yawns, it causes other people around her to yawn, by mimetic effect. This behavior would in fact be explained by the social and empathic bond that we unconsciously weave with other people. Seeing a yawn, we reproduce this behavior out of empathy, to join the other in his universe. It is a disguised social bond, a non-verbal communication allowing us to show our attachment to others and to decode their own emotional state.

Yawning is not that trivial as you might think. It is one of the rare physiological phenomena of our body which is capable of revealing pathologies … or of causing them:

• some people who let themselves go to open their mouths too wide while yawning may drop their jaw;
• in some diseases the frequency of yawning is changed. For example, a person with Parkinson’s disease sees the frequency of yawning drop, and even disappear. Conversely, depressed people, treated with serotonin reuptake inhibitors, yawn much more than normal, up to 200 times a day (the normal being between 5 and 10 times a day). An abundance of yawning can also be a sign of cranial hypertension, brain tumor or neurological disease;
• but yawning is not only a bad sign, nor seen as permanent fatigue or laziness. It can be useful, for example when taking an airplane, to unclog the ears at altitude and to regulate the problems of pressure in the eardrums.