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Koko was one of the most famous gorillas of our time, and appeared to have mastered her own form of sign language. But how good was she really? 
“Talented gorilla Koko playing the ukulele” Image courtesy of Flickr (CC0 2.0)
Koko, the gorilla, apparently mastered sign language and showed the world what apes can do. Recently, she passed away in her sleep at age 46. With her character and talent, Koko touched the lives of millions and was an icon for interspecies communication and empathy. Koko was astonishing, but is it all as it seems? From my scientific point of view (I’m a sign language researcher), let’s have a closer look at her language skills.
Koko’s life story in short
First, let’s see what all her fame is about. Koko was born at the San Francisco Zoo in 1971 and lived most of her life in Woodside, California. The researcher Dr. Patterson began working with Koko the following year, became her best friend, and taught Koko her own ‘sign language’. Francine Patterson reported that Koko was able to understand more than 1,000 signs. Patterson also taught Koko (spoken) English from an early age. Koko apparently understood around 2,000 words of spoken English, in addition to the signs. Koko’s life and learning process can be found back in a number of books and scientific articles.
Koko mastered a sign language?
The media and Koko lovers claim that Koko mastered a sign language. Can it be true? Let’s first discuss what the words ‘mastering and sign language’ mean. Mastering a language implies a native-like knowledge of using and understanding a language. Sign language, in Koko’s case American Sign Language, is a complex and natural language, containing a grammar and more articulators than only the hands such as the face, eye-gaze and the body. Taking all this together, did Koko master American Sign Language?
Certainly, Koko knew some sort of simplified signs or gestures, but probably only about 200 signs (maybe a bit more). This is the amount of words of roughly a two year-old. 200 words is not enough to master a language, especially when you consider that the average person has a vocabulary of around 40,000 words/ signs. Furthermore, her grammar was at this same two-year-old level, at best. In fact, Apes can gesture on their own! (click here for more details). As researchers found out, apes can communicate with each other using body and hand movements. Other apes even communicate with humans in a basic way by using those hand and body movements. Coming back to Koko, yes, she might have been able to communicate with gestures and sign language-related signs, but she did not master American Sign Language.
So, apes are capable of many things and they can even communicate with humans and each other, but in a basic way. Even though the gestural system apes use can consist of many gestures to express various things, it has not been shown that they can fully master a human language. Not a spoken language and also not a signed language. Nonetheless, Koko, you were a great and beloved gorilla, and you learned many gestures to communicate with your buddy Francine Patterson, and we were very impressed. May you rest in peace.
This blog was written by Francie Manhardt and edited by Annelies van Nuland and Marisha Manahova
You made a pretty pedantic set of observations here with little value to the debate on Koko . The point is the gorilla demonstrated clear signs of intelligence and insight . That it knew that nature is aware of man and his destruction of the earth is a sure and troubling wake up call if we are wise enough to heed that call . We should be disturbed. The animal has displayed a simple and yet profoundly powerful mastery of communication.
LMAO no she didn’t. Go rewatch the video. It’s made of so many different clips without any context that are all spliced together. It’s not shown what her trainers were signing to her. The entire video is much more grammatically complex and makes much more sense than any raw videos of koko communicating. Sorry but apes just don’t have the brain capacity for abstract ideas like representations nature, and ecological damage.