It something we all just accept, but why do humans laugh, and why do we laugh when we are happy? i can’t think of any reason.
Let me guess, you get the magazine Scientific American? If not, they just did an article on why people laugh…you can probably find it on their site. http://www.sciam.com
If it’s at http://www.sciam.com, I couldn’t find it.
It’s in the August issue of Sci. Am., under the headline “More of the Best Medicine”. It may very well no be on the website. Oh well. The article doesn’t cover too much, it basically states that laughter is an evolutionary trait to show friendliness and build bonds. The article deals more with men and women laughing differently in various social situations.
I suppose because everyone else is doing it. That’s why most people do anything.
I know where to find it because I am the King of Sciam. http://www.sciam.com/2000/0800issue/0800scicit6.html