Koko (born July 4, 1971, at San Francisco Zoo) is a Western Lowland Gorilla who, according to Francine ‘Penny’ Patterson, is able to understand more than 1,000 signs based on American Sign Language, and understand approximately 2,000 words of spoken English.
Francine Patterson (her longterm trainer) believes that Koko’s use of signs and her actions, which are consistent with her use of signs, indicate she has mastered the use of sign language. Other researchers argue that she does not understand the meaning behind what she is doing and learns to complete the signs simply because the researchers reward her for doing so (indicating that her actions are the product of operant conditioning). However, the latter position is not consistent with the claims that Koko uses the language freely and in novel ways, even when there is no foreseeable gratification. Another concern that has been raised about Koko’s ability to express coherent thoughts through the use of signs is that interpretation of the gorilla’s conversation is left to the handler, who may see improbable concatenations of signs as meaningful.
Patterson says she has documented Koko inventing new signs to communicate novel thoughts. For example she says that nobody taught Koko the word for “ring”, therefore to refer to it she combined the words “finger” and “bracelet”, hence “finger-bracelet”.
