Harnad, Stevan (2016) Cross-species mind-reading Animal Sentience 2016.098
Stevan Harnad, Animal sentience: The other-minds problem
We can never be sure anyone else is sentient. But we can be sure enough in the case of other people, nonhuman primates, mammals, birds, fish, lower vertebrates and invertebrates as to make scepticism academic and otiose (not to mention monumentally cruel). The only genuinely uncertain kinds of cases are jellyfish, microbes and plants. The rest is not about whether but what they are feeling.