The doctor says: "There are currently several hypotheses about the cause of yawning. According to one of these hypotheses, yawning helps regulate brain temperature . If the brain temperature rises, for example due to fatigue, yawning increases blood flow to it and ensures air is inhaled, allowing it to cool down and regulate heat exchange."
Another hypothesis points to a change in the level of consciousness . Yawning often occurs during the transition from sleep to wakefulness or vice versa. The deep breathing during a yawn causes the alveoli—microscopic structures in the lungs—to expand, increasing blood flow and briefly stimulating the heartbeat, which helps the body to become more alert and active or to relax, depending on the situation.
A third hypothesis suggests that yawning helps to open the Eustachian tube , which is responsible for equalizing pressure in the middle ear, just as happens during flight when pressure rises behind the eardrum, and yawning helps to normalize it.
She adds: "There is a common belief that yawning is caused by a lack of oxygen or an excess of carbon dioxide in the body, but studies have refuted this theory, because the levels of these gases in the blood do not affect yawning."
As for the so-called "yawn contagion ," this phenomenon is a form of involuntary motor imitation . This effect is due to psychological factors, in addition to the activity of mirror neurons in the brain.
The ability to "catch" a yawn is closely linked to empathy , the capacity to understand and share the feelings of others. The stronger the emotional connection with another person, the more likely one is to "catch" a yawn. The act of yawning itself is triggered by mirror neurons, which are activated when another person's action is observed.
Dr. Agayeva concludes by saying, "These cells mirror the action in the human brain, which triggers the urge to yawn in response. It is worth noting that children under the age of four or five are rarely susceptible to contagious yawning, because the brain regions responsible for empathy are not yet fully developed."
