Other Minds is an engrossing account of how intelligence and ‘consciousness’ might have evolved in animals, specifically in cephalopods – that is, octopuses, cuttlefish and squid, those fascinating sea creatures who are “the closest we will come to meeting an intelligent alien”. Peter Godfrey-Smith, a professor of history and philosophy of science at the University of Sydney, writes in a clear, accessible manner about this very complex subject, with a great deal of warmth and humour and creativity (for example, he describes scallops as “swimming castanets” and cuttlefish as wearing “animated eyeshadow”).
He begins by discussing how neurons (nerve cells, the building blocks of the nervous system) might have evolved in our earliest common ancestors, then looks at how the cephalopods developed their vulnerable soft bodies and why they might have ended up with such large and complex nervous systems. An octopus has about 500 million neurons, comparable to a dog, but these are not distributed in the same way. Dogs and other vertebrates, including humans, have a large brain that directs the actions of the body using neurons, which branch off from a spinal cord. However, the octopus “is suffused with nervousness; the body is not a separate thing that is controlled by the brain or nervous system”. Its arms can act on the direction of its brain or can act completely independently of the brain and each other.
Octopus behaviour is as mysterious and strange as its neuroanatomy. They can perform well in experiments – learning how to navigate a maze, unscrew jars or operate a lever to receive food rewards – but they also have a tendency to cause mayhem. In one experiment in the 1950s, an octopus named Charles decided to break the lever he was meant to be pulling, snapped off the lamp above his tank, and directed jets of water at the experimenter. Octopuses in captivity often escape, cause floods or short-circuit the lights. Even if they decide to hang around and cooperate, they can recognise individual humans, are aware of when they’re being observed, and can behave in ways that seem deliberate:
“Octopuses love to eat crabs, but in the lab are often fed on thawed-out frozen shrimp or squid. It takes octopuses a while to get used to these second-rate foods, but eventually they do. One day, [Jean] Boal was walking down a row of tanks, feeding each octopus a piece of thawed squid as she passed. On reaching the end of the row, she walked back the way she’d come. The octopus in the first tank, though, seemed to be waiting for her. It had not eaten its squid, but instead was holding it conspicuously. As Boal stood there, the octopus made its way slowly across the tank toward the outflow pipe, watching her all the way. When it reached the outflow pipe, still watching her, it dumped the scrap of squid down the drain.”
Fortunately, most of the observations described in this book are not of poor captive octopuses, but octopuses in the wild, notably at an unusual site off the east coast of Australia, which the author and his colleagues named ‘Octopolis’. Although octopuses are usually solitary creatures, the octopuses living at Octopolis have built a little town, perhaps for protection from predators, and they interact in fascinating ways. The researchers make a point of not interfering with the octopuses, but the octopuses are curious about the divers and their camera equipment, and even make ‘friends’ with one particular researcher, Matt Lawrence:
“Once at a site close to this one, an octopus grabbed his hand and walked off with him in tow. Matt followed, as if he were being led across the sea floor by a very small eight-legged child. The tour went on for ten minutes, and ended at the octopus’s den.”
There’s also an intriguing chapter about the giant cuttlefish, which can change its skin colour and shape in seconds – as camouflage, to communicate with predators or prey or its own species, even as random patterns when resting. Remarkably, it can match its skin colour to its surroundings, even though the two eyes in its head seem to be colourblind. What it does have are thousands of photoreceptor and colour cells all over its skin, which can detect and reflect changes in light and then activate colour cells in response – in effect, ‘seeing with its skin’.
So much about cephalopods is still unknown, and a lot of this book consists of questions and tentative attempts at answers. Why do cephalopods need such a complex nervous system when most of them barely seem to communicate within their own species? Why do they have such enormous brains, when they have such short life spans to use those brains? How can a tree live for two thousand years and a boring rockfish for two hundred years, when the splendidly colourful cuttlefish and curious, clever, playful octopus live for only two years? (Also, who knew that there was such a thing as a vampire squid?)
Other Minds is highly recommended for readers interested in animal intelligence, and in cephalopod intelligence in particular. It would probably help readers to have some basic knowledge of the theory of evolution and how human cognition works, but I think the author does a good job of explaining complex ideas in an accessible way. There are some lovely photos in the book and the author has posted some interesting videos on his You Tube channel.