Koko is a 40 year old gorilla with a sign language vocabulary of 2000 words, the intelligence to invent new compound terms from her existing vocabulary (eg "eye hat" for mask) and many qualities that humans can relate to. In an article about his visit to Koko, Alex Hannaford mentions that "Some sceptics have argued that Kok does not understand the meaning behind what she is doing and simply learns to sign because she'll be rewarded. Dr Patterson [President and scientific director of The Gorilla Foundation] admits that in the beginning she, too, thought [this] ... but the gorilla started stringing words together to describe objects that she didn't know the signs for." Hannaford adds that Koko "signed to achieve goals, but these goals weren't treats: They were to get me to follow her around the room, to get me to lie down, to get me to play with her - to interact."
Gorillas, I suspect, have no concept of money, and so it cannot take the place of the actual needs it in fact helps us to satisfy (at least in part). Koko enables us to see what gorillas are motivated by. In seeing how 'human' she is, we might learn about what really motivates people.