One of the humans working with her used sign language to ask her what she should do for an upset stomach. Koko signed back "stomach you there drink orange," "there" being the refrigerator, which Koko pointed at. Amazingly, ten days later Koko apparently remembered this and used sign language to find out if the woman was feeling better (p. 159). In another remarkable story, a chimpanzee learned to draw and sought the activity out although she was never rewarded for doing so (p. 203). The authors note that the animal may have started drawing to relieve the boredom of being in captivity, but point out that the animal still showed the desire to be creative artistically.
Ultimately the authors plainly state what they have been leading the readers to: "In the end, when we wonder whether to ascribe an emotion to an animal, the question to ask is not, 'Can we prove that another being feels this or any emotions?' But rather, 'Can we prove that this species of animal does not feel this emotion?'" (p. 225)
At the end of the book, Masson returns to something he touched on earlier, that humans tend to believe that anything different when compared to them is inferior to them. This relates not only to beliefs about animals but to racism as well. He suggests that those who use animals in experiments must rationalize that animals don't feel distress as humans do - otherwise, he or she would be acting quite cruelly. He argues that even in animals that cannot anticipate what's going to happen to them, or that don't remember it afterwards, still feel very real anguish and pain. In fact, he suggests that they may suffer more because painful experiences may flood them in a way they do not for humans (p. 227). He quotes animal rights activists such as Peter Singer, who wrote the book Animal Liberation, who argues that every animal has a life, and that when we wrench them from it and use them in experiments, we act despicably. Masson suggests that we have the power but perhaps do not have the right to do these things.
Those conclusions could be questioned. Animal experiments have saved many, many lives - pigs were used to develop bypass surgery for clogged arteries. Many people…