Here’s some more interesting reading, to add to Brian’s.
Jeff McMahan proposes the reduction of suffering by inducing the selective extinction of carnivorous species. This does not include human beings, of course, although he does concede that “(w)e should start by withdrawing our own participation in the mass orgy of preying and feeding upon the weak.”
One of the first dolphins I ever worked with was Circe. I’d bring her a fish when I wanted her to do certain things. If she didn’t do them, I did a “time-out” where I turned my back and walked away. Well, there was a certain type of fish that Circe loathed because it had a spiny tail. So I accommodated her by cutting the spines off of the tail. One day, I forgot to do that. Circe spit it out, swam to the other side of the pool and placed herself into a vertical position that mimicked my time-out. I wanted to test this. I gave her untrimmed fish on four different days. Whenever I gave her fish with spiny tails, she gave me a time-out. What that suggested was that she saw time out as a correction and used it back on me. Well, that’s how we learn to communicate.
And Dr. Guilo Tononi thinks he may be able to measure consciousness bit by bit.