Yawning is a normal conditioned reflex of the body, that is, the body's self-protection. As for why yawn, the reason may not be clear to everyone. Experts associate yawning with "expelling dirty air" and believe that yawning improves oxygen delivery to the brain. Physiologists Provine and Benninger theorize that yawning is a response that promotes physical arousal when people feel compelled to stay awake. In this sense, yawning is a reflection of a person's own "refreshment". A yawn lasts about six seconds, during which the person closes his eyes and listens, and the nerves and muscles of the entire body are completely relaxed. Yawning gives the best physical and mental rest and has an important physiological protective effect on the body.
A normal human being yawns 240,000 times during his life, starting from the time he is in the womb. And a person is most likely to yawn at about 20°C. If the external environment is too cold, the brain does not need to cool down with the help of yawning, and if the temperature is too high (e.g., around 37°C), yawning has little cooling effect and the body naturally yawns less.
The body increases oxygen in the blood and expels more carbon dioxide through the deep breathing exercise of yawning, which results in more energy.
Yawning also helps balance the pressure in the middle ear when the plane lands.
When yawning, the body secretes a melatonin. Melatonin stimulates the body while producing fatigue and then tears, which is a conditioned reflex. Once there are tears, it is good for the eyes, but also can play the role of wet eyes, with the role of eye protection, the German Health Association recommends that people who face the computer for a long time, if you want to give your eyes a break, a yawn when the most convenient and beneficial.
Is yawning really contagious? Actually, it is a psychological suggestion that seeing or hearing others yawn will stimulate the brain's action potential to excite and produce yawning action. Yawning contagion occurs most often among relatives, followed by friends, then acquaintances, and finally strangers. In other words, the closer the relationship, the higher the probability of being infected by yawning.
According to statistics, about 40-60% of the world's adults will follow a yawn when they see someone else yawn. The closer we are to each other, the more empathetic we are and the easier it is to feel each other's stress, anxiety, boredom or exhaustion. The most important thing is to resist yawning, which is not good for your health. This is because it can lead to an excessive buildup of carbon dioxide, which causes chest tightness and makes organs more fatigued, brain cells can't improve oxygen deprivation in time, and the body's stress capacity becomes worse.