The Octopus, The Sea, and the Deep Origins of Consciousness (2016)
by Peter Godfrey-Smith (1965-)
Godfrey-Smith has a lot of experience observing and interacting with cephalopods, and says:
Cephalopods are an island of mental complexity in the sea of invertebrate animals. Because our most recent common ancestor was so simple and lies so far back, cephalopods are an independent experiment in the evolution of large brains and complex behavior. If we can make contact with cephalopods as sentient beings, it is not because of a shared history, not because of kinship, but because evolution built minds twice over. This is probably the closest we will come to meeting an intelligent alien.
He describes the background behind the evolution of nervous systems and brains, and the behavior and mental capabilities of octopuses. He makes a decent case for intelligence in octopuses. Along the way he describes many of the general characteristics that support consciousness in our brains; presumably a creature with some of these characteristics would have some form of subjective experience. It would be like something to be one of these creatures.
The evolutionary investment in a large nervous system and relatively large brain has to have had a favorable cost/benefit ratio. Near the end he surprises us with the news that this investment resides in animal with a typical lifespan of only two years.
In chapter 6, in the section “Conscious Experience”, he describes the “inner workspace” theory, which assumes that the content of consciousness is the sensory and derived information that is the subject of attention at any moment. This is related to the inner-speech phenomenon. He also describes higher-order thought (“thought about your own thoughts”), such as “Why am I in such a bad mood?” or “I hardly noticed that car.” I would add that thought about others’ thoughts is also a key aspect of our conscious experience. One of the limitations of the octopus is that they are not social; they probably have no mental representation of the thoughts of other octopuses.
In the section “Full Circle”, he splits the term afference (meaning the inputs to the brain, contrasted with efference for the outputs) into two parts: exafference meaning the inputs that are caused by the outside world; and reafference meaning the inputs that are due to our own actions, as when a movement of our head affects the visual appearance of the world. The feedback loops involved are parts of the mental mechanism that underlies subjective experience. As an example he discusses writing a note for yourself; at some future time that note will become an input that will affect your behavior.
There is a lot of interesting information about octopuses and cuttlefish (not much about squid), which is quite interesting. There is also a good deal about the evolutionary path to subjective experience, which I found even more interesting.