Yawning has fascinated people for hundreds or maybe even thousands of years. Hence, people made up different myths and stories about yawning over these years.
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.
Anyway, have you noticed that when somebody yawns, the person near or beside him/her later yawns too? Research shows that 40-60% of people who see a picture of someone yawning will yawn themselves. Even reading the word YAWN can make people yawn!
Some people believe in a theory about why yawning is contagious but it was proven to be incorrect. The theory goes like this. When you breathe, you take in carbon dioxide. Scientists used to think you yawned because you had too much Co2 in your body, and you yawned it out. When you yawn near someone else, scientists thought that they then breathed in the cloud of Co2 and then needed to yawn it out. And the theory was that when you are tired you take shallower breaths and so need to get rid of more carbon dioxide. This has recently been proved as a false theory.
Do you yawn when you see this?
References:
http://www.chevroncars.com/learn/wondrous-world/yawn-contagious
http://wiki.answers.com/Q/Why_are_yawns_contagious
Done by: Kimberly Kiong
3/4/2010
