Orangutans, chimpanzees, and gorillas are all apes, and they all laugh when tickled. Their laughter is very much like human laughter. This discovery makes researchers want to find other ways that apes and humans are alike.
Source: Cell Press (2009, June 5). Ticklish Apes? Young Apes Hoot Holler And Laugh In Way Similar To Human Infants. ScienceDaily. Retrieved June 9, 2009, From http://www.sciencedaily.com/releases/2009/06/090604124013.htm