There's no punchline. Laughter is a serious scientific subject, one that researchers are still trying to figure out.
Laughing is primal, our first way of communicating.
Apes laugh. So do dogs and rats. Babies laugh long before they speak. No one teaches you how to laugh. You just do. And often you laugh involuntarily, in a specific rhythm and in certain spots in conversation. More...
Don't miss: