听力原文：M: Well, you seemed to be having fun watching the movie? W: Yeah, it was funny. I think it kept me in stitches right from the start. M: You know, whenever I watch a comedy, I always like to know why it is that people like to laugh. I mean, why does it feel so good to laugh? W: Yeah, I heard from my biology professor that even after centuries of scientific research, no one knows why human beings and just a few other primates laugh. M: I read that Charles Darwin thought that laughter begins with small babies. He believed that even prehistoric parents must have interpreted baby's laughter. The parents enjoyed the laughter, which encouraged them to continue caring for the child. W: Yes, apparently researchers have also found that it has a positive effect on many parents and that it produces certain hormones that actually switch on the body's immune system and actually help fight off diseases. So it could be to help fight off diseases. M: I also heard that some psychology professors found that men are more likely to make jokes than women are, and women are more likely to laugh at them than men are. W: If only your jokes are funny, I might laugh more and fit the pattern. M: Well, I've heard that apes also like laughing. W: I heard that too. Chimpanzees, apes, and a few other primates laugh, but no other animals do. I've seen them laugh at zoos, when tickling each other, and when playing chasing games. Their laugh sounds like rapid panting, but I've been assured it's a kind of laughing. M: Which reminds me I'd better get back to those apes I have for roommates before they eat all the chicken I left out in the kitchen! (9)