My classes were good practice, but as I worked with Koko, I quickly discovered that knowing American Sign Language is not the same as knowing Koko's language. Her language is a little different from the sign language that people use. We call Koko's language Gorilla Sign Language. There are several reasons why Gorilla Sign Language is different from American Sign Language. Gorilla's hands are shaped differently than human hands.
Gorillas have a long palm and a very short thumb.
This makes it hard for them to make some of the shapes used for human signs. Since their hands are different than ours, many of their signs look different. So even though I know a sign, I might not recognize it when Koko uses it. Also, Koko makes up some of her own signs. Koko invented a sign for browse, the salad-like snack we give her between meals.