5 Jan 11
(yawn) is a reflex movement inhale and exhale which often occurs when a person feels tired or sleepy. Not yet known reasons why people yawn, but it is often said that the cause is the amount of oxygen in the lungs is low.  Yawning is easy to spread - 55% of people who see someone yawning will also evaporate within the next five minutes.  In some cultures, yawning is an antisocial attitude so as to evaporate the people of these cultures will shut their mouths.
28 Dec 10
Yawning gives our brain an oxygen boost. Whenever our brain is feeling sluggish, whether it is due to lack of sleep, or boredom making us feel sleepy, we yawn. Too much carbon dioxide in the blood makes us yawn to get more oxygen. We also yawn if we see someone else yawning or think about yawning!
28 Dec 10
Lighting scientific claim that we yawn because of the physical needs us. Aside from fatigue, we also yawn when our blood oxygen deficiency.There is also a theory that states could evaporate harmonize our body temperature. Half of people think that we yawn when we are feeling bored...