Why People Yawn?So far, no one has succeeded to determine precisely why people begin to yawn when they look at a person who does it. One theory is based on the assumption that yawning is a form of nonverbal communication. Among baboons, for example, intensive yawning is a signal within the group that it is time to sleep. The leader (alpha male) of the group ends the ritual with loud yawn and wide gaping mouth. If our ancestors used yawn to communicate as today baboons, then the contagious yawn may be unwilling, genetically programmed phenomenon.
Describing why a yawn is contagious, we could answer the question why someone yawns. All people do it a dozen times a day, often early in the morning and late in the evening. In fact, the yawning begins before birth - fetus in the uterus starts yawning already in the 11th week of development.
However, there is not much knowledge about the yawn mechanism. Yawning, most likely, does not always show the need for sleep and it seems to has nothing to do with the assumption that the body does not have enough oxygen or has too much carbon dioxide (which, theoretically, could require a deep yawn). The second theory loses reliability after a study conducted in 1987. which showed that volunteers who inhaled large amounts of oxygen, didn't yawn less than those exposed to high concentrations of carbon dioxide.
Theories About the YawningBelow are some theories about yawn but none of them have received scientific confirmation. Yawn expands human lungs and surrounding tissue, thus protecting the delicate tissue of the lungs from cracking. This could explain why people yawn more at a time of shallow breathing - when they are tired, when they are bored or when they just got up from bed. Yawn distributes a substance called surfactant, which is attached to tiny liquid air pockets in the lungs, helping them to stay open. This substance is a critical substance that allows the infant to survive the exit from the uterus. This theory could explain why fetus yawns during development, as it prepares to begin to use its own lungs. Yawn expands muscles and joints and increases the volume of the heart. Therefore, it prepares the body to the higher level of caution, especially after relaxing. This explains, why athletes and professional musicians often catch themselves in yawning before their performance.
Sign of the DiseaseBelieve it or not, yawn may be a signal for the disease. Although it is rarely considered as the first signal, yawn is very intense markedly in patients with multiple sclerosis and amiotrophic lateral sclerosis. Yawn occurs after injury from radiation and also it was recorded in patients receiving therapy against Parkinson's disease. Occasionally, frequent yawning may signal the start of migraine. On the other hand, the yawn is rarely observed in patients with schizophrenia. It is not clear why the disease can determine the frequency of a person's yawn. Researchers have noted that stimulation of certain parts of the brain in animals and humans may provoke yawning. Certain substances, the messengers in the brain, may also affect yawning.