Why does yawning occur

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The mirror-neuron system. Annu Rev Neurosci. Norscia I, Palagi E. Yawn contagion and empathy in Homo sapiens. PLoS One. Ingroup-outgroup bias in contagious yawning by chimpanzees supports link to empathy. Yawns may be more likely when the blood needs oxygen.

A yawn causes a big intake of air and a faster heartbeat, which could theoretically mean that it is pumping more oxygen through the body. So a yawn may be simply designed to help clear toxins out of the blood and provide a fresh supply of oxygen. Yawning may cool the brain. A yawn causes the jaw to stretch out, increasing blood flow in the face and neck.

The large inhale and rapid heartbeat caused by the yawn also causes blood and spinal fluid to cycle through the body faster. This whole process may be a way to cool down a brain that has gotten too hot. Some researchers believe the reason humans yawn has more to do with evolution.

Before humans communicated vocally, they may have used yawns to convey a message. Yawns are considered a sign of boredom or sleepiness, and that could be what early humans were communicating as well.

However, early humans may have used yawning to signal their alertness to others, bare their teeth to aggressors, or serve as some other communication tool. Humans and chimpanzees are not the only animals that yawn. All vertebrates yawn, from fish and birds to wolves and horses. There are only three species that yawn contagiously, however: humans, chimpanzees, and the family of wolves and dogs.

One thing that many people agree on is that yawning appears to be contagious. Results revealed that the chimpanzees were more likely to catch the yawn when watching chimpanzees they were familiar with yawn. This supports the idea that empathy and familiarity are involved in the contagiousness of a yawn. There was little correlation between intelligence, time of day, or empathy in those tested.

The biggest factor they found was age. Older people were less likely to catch a yawn from others. Yawning is usually harmless, but it is possible to yawn too much. Answering this question is not nearly as easy as defining the action. There are a number of theories about why we yawn, but remarkably little good research on this topic.

There are several agreed upon causes for yawning, however. First, it that when changing elevation rapidly as in an airplane, you will both voluntarily on purpose yawn and also involuntarily not on purpose yawn to try and equalize pressures within your ear. This works and is an accepted reason for yawning.

Another indisputable cause of yawning is called social empathy. In fact psychologists have proven that the more empathetic you are, the more likely you are to yawn when someone else does. There has been fascinating research about the hierarchy of this suggestion.

If you are very close to a person emotionally, you will yawn if they do. The rank order of this suggestion is family, friend, stranger. The closer one is to the person who yawns, the more likely one is to yawn as well.