Koko (born July 4, 1971) is the name of a captive, enculturated gorilla trained by by Francine Patterson and other scientists at Stanford University to communicate certain signs using American Sign Language. Some scientists claim that Koko's actions indicate a capability to learn language. Many others claim that her actions are simply the result of operant conditioning, in that she does not understand the mechanisms behind what she is doing but learns to complete the signs simply because the researchers reward her for doing so.
Born in San Francisco, California, Koko's training began at the age of one. Patterson eventually claimed that Koko had a vocabulary of over 1000 signs. Countless documentaries have been made on Koko, including 1977's Koko - A Talking Gorilla. She has lived most of her life in Woodside, California.