Why do we yawn?

Yawning can be termed as an involuntary reflex action of the body. While yawning, the mouth is opened wide with deep air inhalation and stretching of ear drum at the same time and followed by short exhalation. This involuntary action is controlled by the nerve and the spinal centers. In a more general sense, yawning may be the result of boredom and fatigue.


Possible causes

YawningSeveral theories have been proposed to establish the reasons for yawning but none of them are strongly supported.

  • As per one theory yawning occurs when carbon dioxide levels in the body increase. With the increased inhalation of air, there will be more oxygen absorption by the body. But this theory has been proven incorrect. In fact studies suggest that yawning reduces the oxygen levels in the body.
  • Based on the brain-cooling theory, yawning is a result of the brain’s effort to control body temperature. A German researcher Guttman suggests that there may be one among the three reasons that may be the result of yawning. Because of inhalation and exhalation of oxygen, the brain cools down, or because of the outflow of oxygen the pressure on the brain is reduced or because of inhalation of air, the pressure of the brain is increased.
  • Another study asserts the fact that yawning may take place when the body wants to stretch. It has been observed that the person who yawns often has the urge to stretch the body. This phenomenon is studied in animals. For them staying alert is the need of the hour and by way of yawing one animal in the group alerts the other animals. It is said that yawning is contagious and it has been established that it holds true for animals as well. There is evidence that yawning influences the alertness of the person. A person tends to stay more alert after yawning.
  • According to another theory, there are certain chemicals that affect the appetite, mood and emotions of a person. As these chemicals are activated, there will be increased yawning in a person. Endorphins in the brain reduce the yawning frequency in a person. Persons who take serotonin related medicines exhibit more yawning.
  • A researcher at Leeds University monitored the behavior of students who were asked to wait in the reception. He says, “We believe that contagious yawning indicates empathy. It indicates an appreciation of other people’s behavioral and physiological state”.
  • Yawning may be observed in persons who suffer from stroke, diabetes or other adrenal conditions.
  • If yawning is studied from evolutionary perspective, it can be termed as a “herd instinct”. If one member in the herd yawns, it gives a signal of tiredness to others and it results in a systematic sleeping and resting pattern.


Yawning has proved several times that it is contagious. It has been observed that a person tends to yawn if he sees the other person yawn, or just thinking about yawning or looking at a picture of a person who is yawning. In a behavioral study conducted in Italy in 2011, yawning was seen contagious only between those people who knew each other. Among strangers there was a delay in the yawning response.


Animal yawning
  • In animals yawning may be the result of being in a perilous situation.
  • Yawning serves the purpose of sending warning signals in animals. Charles Darwin explained in his book that baboons showed their teeth by yawning to the enemies. Guinea pigs also use yawning as an expression of anger against the enemies. Reptiles like snakes yawn to adjust their jaws and to expand their trachea. Fish also yawn but this behavior is seen when there is less oxygen or they yawn because of extensive heat.

 Cat Yawning

Tidbits about yawning
  • In ancient Greek and Mayan civilization, people believed yawning is an action wherein the soul tries to escape the body.
  • Yawning was believed to do harm to the person who yawns.
  • A loud yawn could be penalized by the court!
  • It is considered rude to yawn before elders as it shows that the person is bored.