Here's a fascinating article: Thinking like an octopus by Alvin Powell of the Harvard Gazette. Powell writes about the ideas of Peter Godfrey-Smith, a Harvard philosopher who has spent time observing octopi in the wild and in captivity.
Godfrey-Smith has noted that when an octopus is in an unfamiliar tank with food in the middle, not all of its arms do the same thing. Some of them "seem to crowd into the corner seeking safety while others seem to pull the animal toward the food, as if the creature is literally of two minds about the situation."
The idea of a brain having more than one "mind" is not new. If the two halves of the human brain are severed, it becomes clear that the two hemispheres have very different desires and intentions. One hand buttons a shirt while the other simultaneously unbuttons it. One hand pulls down one's trousers, while the other pulls them back up. (See Rita Carter, Mapping the Mind, p. 50).
In The Bisected Brain the neuroscientist Michael Gazzaniga wrote that splitting the hemispheres "produces two separate, but equal, cognitive systems each with its own abilities to learn, emote, think, and act" (p. 2).
But the idea of an octopus having several minds is a new wrinkle. Octopi are very smart creatures. They can alter their color and skin texture to mimic the appearance and behavior of other undersea creatures such as kelp and flounder. (See, for this example, this astounding video of part of a kelp plant suddenly morphing into an octopus and fleeing from a diver.) They can change their skin color twenty times a minute, and it has been speculated that this could be a form of communication with other octopi. (See Eugene Linden, The Octopus and the Orangutan, p. 50.) Somewhat as it takes intelligence for an actor to take on gestures and accents unlike his own, an octopus may have the intelligence to observe and "inhabit" the ways of being of other creatures.
The thing with octopi, though, is that half of their 500 million neurons are in the arms rather than in the brain itself, leading Godfrey-Smith to speculate that the arms have "minds of their own." The octopus's intelligence may be distributed throughout its body, rather than residing wholly in the brain itself.
Godfrey-Smith speculates that learning about octopoid intelligence may help us understand which aspects of intelligence are universal and which are unique to the human species. Is it necessary for brains to be centralized in one location, as they are in humans? In what way is it important to have a unified consciousness -- that is, a sense of self? Does it necessarily follow that the members of an alien technological species must have a unified sense of self?
It's not easy to study octopi because they live in a profoundly different environment than we do. We have to be careful about not imposing our human categories of thinking onto them. Indeed, the qualifiers in the paragraph I quoted above are important: some arms "seem to" crowd into a corner while others "seem to" move toward the food. We really don't know why the octopus is behaving as it is at that moment.
But it does raise the question of whether octopi, if left to themselves for another few hundred million years, would evolve into an intelligent species with a decentralized brain and perhaps consequently a different kind of sense of self than humans do. Personally, I'm skeptical that octopi could ascend to technological intelligence; many scientists have argued that the development of intelligence was catalyzed by the development of tools, and it's hard to develop tools without access to fire and the metalworking it affords.
But that could just be my carbon-based, air-breathing, tool-using, bipedal-locomotion biases speaking. Perhaps there are forms of aquatic intelligence on other planets that focus on mimicry and language. Until we get to meet E.T., we really can't know what aspects of intelligence are inherently universal.
Read more about Michael Chorost's work on his website.