Eight arms and nine brains

 kw: book reviews, nonfiction, octopuses, intelligence, philosophy

After reading (and reviewing) Metazoa by Peter Godfrey-Smith, I just had to get his earlier book Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness.

The author has spent much time at a place near Australia called Octopolis, where as many as a dozen or more octopuses, which are usually solitary, live in rather close association. Near the end of the book he muses about how Octopolis came to be, and mentions in a glancing way a few other reports of these animals living near one another. He has also spent much time "visiting" giant cuttlefish (up to a meter in size) that frequent other areas, also near Australia. These experiences inform his thoughts about "What is it like to be an octopus" and about consciousness in general.

Theories of why we have large brains and consciousness tend to revolve around our sociability. At least among apes, brain size correlates with social environment. So why do octopuses have such large brains? Currently, only at Octopolis are they seen to associate socially, although much of that is fighting. I suppose society has to start somewhere.

The book opens with a quote from William James, which I reproduce here in full:

The demand for continuity has, over large tracts of science, proved itself to possess true prophetic power. We ought therefore ourselves sincerely to try every possible mode of conceiving the dawn of consciousness so that it may not appear equivalent to the irruption into the universe of a new nature, not-existent until then. —William James, The Principles of Psychology, 1890

This exactly accords with my understanding. René Descartes thought that only humans were conscious, leaving him free to unflinchingly torture a dog, claiming the animal's screams were robotic utterances. I titled my review of Metazoa "Is 1% of a mind still a mind?" Let's see if we can figure what proportion of a mind as we know it might reside in the common octopus, Octopus vulgaris.

The nervous system of the common octopus includes half a billion neurons. However, 60% of these reside in eight sub-brains, one near the base of each arm, and the other 40% are in a torus (a donut-shaped mass) that surrounds the esophagus. Thus, the main brain has about 200 million neurons, while each arm's sub-brain has about 37.5 million. We should probably consider the main torus as equivalent to the cortex in vertebrate brains, and the 8 sub-brains, taken together, as equivalent to the cerebellum, which runs the body and, so far as we know, does not contribute to consciousness. The size of the main torus is equivalent to the entire brain of a Norway rat. But if we consider the octopus torus-brain equivalent to the vertebrate cortex, it more closely matches that of an average house cat (250 million) or a less-familiar animal, the rock hyrax (200 million).

Octopuses are mollusks. Of mollusks, octopuses, squids, cuttlefish, and scarcer animals such as the nautilus and sepiolid ("Dumbo octopus") make up the order of cephalopods, which means "head-foot". Among mollusks, all the brains are found among the cephalopods. The largest snails and clams (members of two other orders of mollusks) have brains containing ten to twenty thousand neurons, not millions.

What is the size of the human cortex? We've all heard that we have "about 100 billion nerve cells". The actual number is close to 85 billion, but only 16 billion make up the cortex, where we think consciousness is created, the feeling of what it is to "be a person." Most of the rest are in the cerebellum, which runs the mechanics of our body. If there is a linear relationship at work here, 16÷0.5 = 32: our cortex is 32 times as large as that of an octopus. Does that mean we are 32 times as conscious? Maybe so! Or perhaps self-awareness (which may or may not be the same thing) is a less-than-linear function of brain size, such as a square root. Then we could say we are about 5.5 times as self-aware as an octopus. 

Let's speculate for a moment what it might "be like" to be a honeybee, which has a million neurons. Estimating that half are involved in its sense of self, the little bee may be 1/32,000th as conscious as we are, or perhaps as much as 1/180th. Whatever they think about, it's sure to be a lot slower, and less profound. Beyond that I dare not tread!

Regardless, it is pretty clear from the stories and analyses by Dr. Godfrey-Smith that octopuses are quite self-aware. He tells one story that touched me, of a SCUBA diver who saw an octopus in its den and reached his hand toward it. The octopus reached back and grasped his hand, then came out of the den and began "walking" (they do this on two or four of their arms, with the others coiled or held upward), leading the man on a "tour" of the area that lasted ten minutes. That incident may be the closest a person and an octopus have come to communication on any meaningful level. Far too frequently, the animals are brought into a lab and "tested" with mazes or food choices and so forth. Frequently, they express their frustration by squirting water on the experimenters. Perhaps they prefer not to be treated like the village idiot.

A side thought just occurred to me. The brains of birds and mammals are differently arranged, and the neurons of birds seem to be more efficiently packed and connected. Thus an African gray parrot, with a walnut-sized brain, nonetheless has about 2.5 billion neurons, and can learn to speak and hold conversations with humans. Rather simple conversations, true, but none of us has learned even a single word of "parrot".

As we ponder now we might communicate with residents of a different planet around some other star, we would do well to consider how we can better communicate with parrots, octopuses, and other critters among which we live. 

Do octopuses have a visual language? Their skin is akin to a video screen, and sometimes seems to reflect their thinking. Perhaps much of the time their skin patterns are akin to a visual EEG! I wonder what is on this one's mind.

I really like this author's writing. I've riffed on what he wrote more than reported about it. The best authors stimulate thought!