Ok… here is what a yawn is:
btw.. these are all theories.. so some could be false… 8)
1. sometimes body doesn’t get enough oxygen so to get enough of it, we have to breathe deep…
2. sometimes it is just a reflex of tiredness
3. other researches say that yawn stretches the lungs and that helps keep the lungs lubricated, so that they don’t collapse. so if we didn’t yawn taking a deep breath would become harder and harder.
4. the last reason is that it is plain contagious…
What you are experiencing when you feel the need to yawn when you see others yawn is called “social facilitation.” Social facilitation is a process by which one member of a population does something, the rest do the same thing. This is also experienced when you see someone throwing up. You get the feeling like YOU have to throw up. While this is the reason, why yawning is controlled by social facilitation (contagious behavior) is yet unknown