But that doesn't mean bats or other animals have the exact same set of sensations. We know that can't be true because many birds can see more than three primary colors, and presumably bats have a sonar sensation. Maybe it's a kind of color or sound, but it could be something altogether different as well. And what would it be like as an octopus, where the nervous system is as much distributed in the tentacles, which act semi-independently, as it is in the head? — Marchesk
Agreed. There would be variations. A new sense such as bats' sonar would theoretically imply a whole new set of qualia specific to that sense, of if you prefer, a typology of sensations specific to that sense. I agree that as of now, there's no way for us to even imagine what these theoretical sonar qualia would feel like. But this doesn't prove that we will never be able to do so. We obviously cannot tell in advance what discoveries science will make in the future, otherwise we would make them now... (Popper)
Another huge difference between humans and other animals is in the use of and dependency on symbolic language. We cannot think without language (though a human baby supposedly can).
The case of octopuses is interesting because bats are mammals, and hence very close to us humans in the darwinian tree. Cephalopods (squids, octopuses etc.) are invertebrate and thus very far from us. And their nervous system, as you say, is much more scattered than ours.
Nevertheless, invertebrate nervous systems use the same basic element than ours: neurons that appear similar to mammals' except that the cephalopod ones are larger in size. Octopuses have bigger neurons than we do, for some yet unknown reason.
An interesting consequence is that for a long time, we knew more about octopuses neurons that we did about our own, because it is far easier to stick electrodes into a big cell than into a small one. Studying cephalopod neurons was just easier. Of course the assumption was that we would learn something about neurons in general, including our own, by studying squids'. Just like we study genetics in mice or drosophilia because it's easier than on humans, but the results are supposedly applicable to humans.
So the assumption was, and still is, that
at neuronal level at least, what happens in a squid is comparable to what happens in you and me.
Now, my argument here is that, if indeed the neurons of squids and ours function in a similar way, then we should expect their mental world and ours to not be so very different. It might be less of this or more of that; some variations would apply, but all using a common basic material.