At the Francis Crick Memorial Conference in Cambridge last month, a collection of internationally recognized experts on consciousness took an unusual step, as science conferences go: they issued a declaration (pdf). The subject was whether or not non-human animals could be considered "conscious." (See discussion by Octopus Chronicles, Christof Koch, io9.) The spirit of the declaration was in the direction of saying "pretty much, yeah," although they tried to stick to what could be scientifically discussed. Here's the upshot of the declaration:
The absence of a neocortex does not appear to preclude an organism from experiencing affective states. Convergent evidence indicates that non-human animals have the neuroanatomical, neurochemical, and neurophysiological substrates of conscious states along with the capacity to exhibit intentional behaviors. Consequently, the weight of evidence indicates that humans are not unique in possessing the neurological substrates that generate consciousness. Nonhuman animals, including all mammals and birds, and many other creatures, including octopuses, also possess these neurological substrates.
Even the experts don't necessarily agree on a definition of "consciousness," so the declaration doesn't come right out and say "animals are conscious." But the authors basically agree that the mental supervenes on the physical, so whatever consciousness may be, it must have some neurological substrate -- some parts of the brain that do the work. The point they're making is, whatever those parts are, some animals have them too. I don't have a well-thought-out position on this, at least as far as the big-picture consequences are concerned. Obviously human beings are animals, so we shouldn't be surprised that we share neurological workings. And obviously (I would argue) consciousness is not located somewhere simple and discrete in the brain (like the pineal gland) -- it has grown up gradually, and makes use of various parts of the brain, so it's not surprising to find aspects of consciousness involving pre-cortical structures. We are part of the evolution of the biosphere, not something standing outside of it. On the other hand, whether it's qualitative or merely quantitative, there is something different about human beings. We're the only species that builds cars, if you want a blunt way of putting it. We're the only species that sets up political action committees, and does contour integration. (Usually not at the same time.) The human brain seems to represent some kind of phase transition with respect to the brains of non-human animals. It might be a gradual, second-order transition, or it might be an abrupt, first-order transition. We don't really know, and that's why it's important to tackle these difficult scientific questions (and not make up our minds about the answers ahead of time). The real-world question is how our increasing understanding of the relationship between human and animal neurology should affect how we treat non-human animals. It's not an easy one, and saying "they're not people so we can do whatever we want" or "humans are just animals and we should treat every animal with equal dignity" both seem like simplistic cop-outs to me. I'm just glad the science is moving forward, so we can increasingly base our behaviors on reality rather than on vague guesses.