Intelligence is found on Earth in only a few groups of animals. Most are chordates—animals with backbones—including fish, reptiles, mammals and birds. Among these, still fewer groups exhibit a high degree of intelligence: primates, the elephant family, whales and dolphins, and some bird species, especially crows and parrots.
All these are comparative latecomers in evolution, whereas the cephalopods constitute a striking anomaly. They are molluscs, meaning they are related to slugs, snails, clams, and whelks, all of which originated in very remote times, long before the mammals and birds. None of the other molluscs possesses a complex nervous system.
Godfrey-Smith provides plenty of evidence for octopus intelligence. Some of this comes from formal testing in the laboratory, but not all; some is based on spontaneous behaviour. 'Octopuses in at least two aquariums have learned to turn off the lights by squirting water at the bulbs when no one is watching, and short-circuiting the power supply. At the University of Otago in New Zealand, this became so expensive that the octopus had to be released back to the wild.'
Godfrey-Smith is careful to point out that this behaviour may not be as astonishing as it seems. Octopuses dislike bright light and in the wild they squirt water at things that annoy them. Still, he is impressed by how quickly they have learned the new trick. This seems to be one aspect of their fondness for exploring their environment and even playing with objects, which they also do.
But perhaps the most remarkable story is told by Jean Boal, an experimenter who is known for the strictness of the criteria she applies to apparent evidence for intelligence in her subjects.
Octopuses have definite food preferences and don't much care for thawed-out squid or shrimp, although they will eat them. One day Boal was walking down a row of tanks giving a piece of squid to each occupant.
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, watching her all the way. When it reached the outflow pipe, still watching her, it dumped the scrap of squid down the drain.It's difficult to resist the idea that this story is evidence for recognition of another mind by an octopus. Another finding that points in the same direction is the fact that octopuses can recognise individual humans and react to them in different ways. One octopus, in the same laboratory that had the lamp-squirting problem, took an objection to a particular staff member, for no apparent reason, and squirted her whenever she walked past. At another lab an octopus took to squirting all new visitors although the regular staff were not squirted.
Godfrey-Smith has a chapter in which he tries to answer a question that I have wondered about for a long time. Why do such intelligent animals have such short life spans—only one or two years in most species? An advanced brain is a 'costly' item in a biological sense; it seems odd for evolution to go to the trouble of producing it and then to throw it away almost immediately. This is not true, for example of elephants, primates or birds, which are long-lived.
Godfrey-Smith thinks that at least part of the explanation may lie in the fact that the cephalopods evolved from animals with a shell. Early cephalopods had shells but the octopus has lost its shell entirely; squid and cuttlefish have retained it only internally. The lack of a protective shell makes the animals vulnerable to predators. Acquiring a complex nervous system enabled them to behave in ways that enhanced their chances of survival. Even so, they can't expect to live very long. A short life but a merry one seems to be the outcome.
It isn't only their highly evolved nervous system that makes the cephalopods so remarkable. Another characteristic of the group is their ability to make rapid complex colour changes. Octopuses use this mainly for camouflage. Cuttlefish carry out astonishingly complex colour displays, which are usually thought to be signals to other members of a group. But here we encounter another mystery: cephalopods are apparently colour-blind! This is based on the fact that their eyes contain only one kind of colour receptor, which is insufficient for colour vision; we usually have three. In part the explanation may be that the skin of cuttlefish is light-sensitive and may be able to perform some kind of colour recognition.
In any case, not all colour changes in cuttlefish seem to be intended for others. Godfrey-Smith describes witnessing a prolonged display of this kind by a giant cuttlefish. 'It reminded me of music, of chords changing amid and over each other.' And yet, to what end? There were no other cuttlefish in sight; Godfrey-Smith was the only witness.
It occurred to me that he was paying so little attention to me that all of this might have been going on while he was asleep or half-asleep in a state of deep rest. Perhaps the part of his brain that controls the skin was turning over a sequence of colors of its own accord. I wondered if this was a cuttlefish dream—I was reminded of dogs dreaming, their paws moving while they make tiny yip-like sounds.Although the book is primarily about cephalopods, Godfrey-Smith digresses at times to talk about consciousness in general and human consciousness in particular. He has an interesting discussion on the role of 'inner speech' which he thinks is important, although perhaps not essential, for 'higher-order thought', meaning the ability to think about one's own thinking,
This is not a long book but it contains much more than I can indicate in a review like this. Perhaps the dominant idea I'm left with is the feeling of familiarity coupled with strangeness that comes from the description of the cephalopod mind. One aspect of this that I hadn't known about is that although the octopus has a large brain, its awareness is not entirely centred there as it seems to be in us. The octopus's nervous system is widely distributed throughout its whole body, so that each tentacle is partly autonomous. The octopus mind seems to be diffused rather than sharply localised. Coupled with this, the octopus body itself lacks precise definition; it can take an almost infinite number of shapes and can squeeze through any space that is only a little larger than its eye. Octopus consciousness must be very different from ours in many ways, yet we can communicate with each other.
One final reflection. People often speak or write as if they thought it was the 'purpose' of evolution to produce intelligent life. But is it? Given its scarcity, that seems hard to believe. Do we perhaps over-value this trait because of its importance to us? Is it merely one manifestation of life among a myriad others, resembling the apparently pointless shifting colour patterns produced in sleep by Godfrey-Smith's cuttlefish friend?