Mind: A Brief Introduction (John R. Searle) / quote 36 of 138
How I know my dog is conscious
I think the answer is that the basis on which I am confident that my dog is conscious and has a specific content to his consciousness is not simply that his behavior is appropriate, but that I can see that the causal underpinnings of the behavior are relatively similar to mine. He has a brain, a perceptual apparatus, and a bodily structure that are relevantly similar to my own: these are his eyes, these are his ears, this is his skin, there is his mouth. It is not just on the basis of his behavior that I conclude that he is conscious, but rather on the basis of the causal structure that mediates the relation between the input stimulus and the output behavior. In the case of humans, the input stimulus causes experiences, which in turn cause output behavior. The underlying physical structure that enables the input stimulus to cause experiences is relevantly similar in humans and higher animals. For that reason we are completely confident that dogs and chimpanzees have conscious states, in many respects like our own. When it comes to snails and termites, we have to leave it up to the experts to tell us whether or not they have a rich enough neurobiological capacity to have conscious life.