Why Laughter Matters Although most people believe that laughter is one of the nature's great treatments for a whole range of mental and physical diseases, it is still a serious scientific subject that researchers are trying to figure out. "Laughter above all else is a social thing," says Baltimore neuroscientist, Robert Provine, who has studied laughter for decades. "All laughter groups laugh 'ha-ha-ha' basically the same way. Whether you speak Mandarin, French or English, everyone will understand laughter. There is a pattern generator  in our brain that produces this sound." Laughing is our first way of communicating. Babies laugh long before they speak. No one teaches them how to laugh. They just do. People may laugh at a prank  on April Fools' day. But surprisingly, only 10 to 15 percent of laughter is the result of someone making a joke. Laughter is mostly about social responses rather to a joke. Deaf people laugh without hearing and people on cell phones laugh without seeing, showing that laughter isn't dependent on single sense but on social interactions. And laughter is not just a people thing. Chimps  tickle  each other and even laugh when another chimp pretends to tickle them. Jaak Panksepp, a Bowling Green University Psychology professor, studies rats that laugh when he tickles them. It turns out rats love to be tickled--they return again and again to the hands of researchers tickling them. By studying rats, scientists can figure out what's going on in the brain during laughter. Northwestern University biomedical engineering professor, Jeffrey Burgdorf has found that laughter in rats produces a chemical that acts as an antidepressant . He thinks the same thing probably happens in humans, too. This would give doctors a new chemical target to develop drugs that can fight depression. Even so, laughter itself has not been proved to be the best medicine, experts said. Margaret Stuber, a professor at University of California, studied whether laugher helped patients. She found that distraction  and mood improvement helped, but she could not find a benefit of laughter alone. "No study has shown that laughter produces a direct health benefit," Provine said, largely because it's hard to separate laughter from just feeling good. But he thinks it doesn't really matter: "Isn't the fact that laughter feels good when you do it enough?" According to the passage, scientists studied rats in order to find   _  .
if they can laugh if they like laughing what laughter in rats produces how rats react while being tickled