A yawn is a reflex act in which air is inhaled deeply with the mouth wide open, and then exhaled. It has been discovered that about 50% of adults yawn after seeing another person yawn. This spontaneous act is known as “contagious yawning.”
There are a number of reasons why we yawn. Although the mechanism is not fully understood, some possible reasons to why we yawn include:
- A need for oxygen in the body due to increased levels of carbon dioxide in the blood.
- A way of cooling down the brain, thereby regulating brain temperature.
- When in a state of nervousness, tiredness, boredom or when hungry.
Contagious yawning could also be triggered just by watching a video of someone yawning, hearing the sound of a yawn, or even thinking of it! Studies done revealed that contagious yawning has been observed in some animals like chimpanzees, cats and dogs. Typically, humans do not exhibit contagious yawning till about the age of four.