Why is yawning contagious?

Why is yawning contagious?

Today we know that a yawn is a reflex of inhalation and exhalation that draws more oxygen into the bloodstream. A reflex is a built-in physical reaction that people often do not have control over. A yawn is often associated with a person being tired, but this is not always the cause for a yawn. People yawn for many reasons including stress, boredom, emotion and over-work.

If one person yawns, this appears to cause another person to yawn. Researchers have found that 40-60% of people who see a picture of someone yawning will yawn themselves. Even reading the word YAWN can make people yawn.

Although this “contagious” yawning behavior is not understood, it has been suggested that this could be the result of an unconscious herding behavior — a subtle way to communicate group behavior, such as when a birds follow the behavior of one bird, and all rise together as a whole flock.

Maybe a yawn is a signal to the group that it’s time to go to sleep. Or if someone yawns when they’re bored, it may be a sign to change the topic of conversation. Yawning is not limited to humans. Animals of all types yawn.

Some of the more scientific explanations of why we yawn are caused by physical needs. One likely explanation is that the yawning reflex is triggered when our blood needs more oxygen. The deep breath helps replenish the levels of oxygen in our blood. Another common theory is that the yawn help regulate our body temperature. Other hypotheses suggest that the same chemicals in our brain that affect our moods and emotions cause us to yawn.

Source:http://www.chevroncars.com/learn/wondrous-world/yawn-contagious