Inches above the seafloor of Sydney’s Cabbage Tree Bay, with the proximity made possible by several millimetres of neoprene and a scuba diving tank, I’m just about eyeball to eyeball with this creature: an Australian giant cuttlefish.

Even allowing for the magnifying effects of the mask snug across my nose, it must be about 60cm (two feet) long, and the peculiarities that abound in the cephalopod family, that includes octopuses and squid, are the more striking writ so large.

Its body – shaped around an internal surfboard-like shell, tailing off into a fistful of tentacles – has the shifting colour of velvet in light, and its W-shaped pupils lend it a stern expression. I don’t think I’m imagining some recognition on its part. The question is, of what?

It was an encounter like this one – “at exactly the same place, actually, to the foot” – that first prompted Peter Godfrey-Smith to think about these most other of minds. An Australian academic philosopher, he’d recently been appointed a professor at Harvard.

While snorkelling on a visit home to Sydney in about 2007, he came across a giant cuttlefish. The experience had a profound effect on him, establishing an unlikely framework for his own study of philosophy, first at Harvard and then the City University of New York.

The cuttlefish hadn’t been afraid – it had seemed as curious about him as he was about it. But to imagine cephalopods’ experience of the world as some iteration of our own may sell them short, given the many millions of years of separation between us – nearly twice as many as with humans and any other vertebrate (mammal, bird or fish).

Elle Hunt with an Australian giant cuttlefish at Cabbage Tree Bay, Manly, Sydney. Photograph: Peter Godfrey-Smith

Cephalopods’ high-resolution camera eyes resemble our own, but we otherwise differ in every way. Octopuses in particular are peculiarly other. The majority of their 500m neurons are in their arms, which can not only touch but smell and taste – they quite literally have minds of their own.

That it was possible to observe some kind of subjective experience, a sense of self, in cephalopods fascinated Godfrey-Smith. How that might differ to humans’ is the subject of his book Other Minds: The Octopus, The Sea and the Deep Origins of Consciousness, published this month by HarperCollins.

In it Godfrey-Smith charts his path through philosophical problems as guided by cephalopods – in one case quite literally, when he recounts an octopus taking his collaborator by hand on a 10-minute tour to its den, “as if he were being led across the sea floor by a very small eight-legged child”.



Charming anecdotes like this abound in Godfrey-Smith’s book, particularly about captive octopuses frustrating scientists’ attempts at observation.

A 1959 paper detailed an attempt at the Naples Zoological Station to teach three octopuses to pull and release a lever in exchange for food. Albert and Bertram performed in a “reasonably consistent” manner, but one named Charles tried to drag a light suspended above the water into the tank; squirted water at anyone who approached; and prematurely ended the experiment when he broke the lever.

Most aquariums that have attempted to keep octopuses have tales to tell of their great escapes – even their overnight raids of neighbouring tanks for food. Godfrey-Smith writes of animals learning to turn off lights by directing jets of water at them, short-circuiting the power supply. Elsewhere octopuses have plugged their tanks’ outflow valves, causing them to overflow.

This apparent problem-solving ability has led cephalopods (particularly octopuses, because they’ve been studied more than squid or cuttlefish) to be recognised as intelligent. Half a billion neurons put octopuses close to the range of dogs and their brains are large relative to their size, both of which offer biologists a rough guide to brainpower.

The coconut octopus is one of the few cephalopods known to exhibit the behaviour of using a tool. Photograph: Mike Veitch/Alamy

In captivity, they have learned to navigate simple mazes, solve puzzles and open screw-top jars, while wild animals have been observed stacking rocks to protect the entrances to their dens, and hiding themselves inside coconut shell halves.

But that’s also reflective of their dexterity: an animal with fewer than eight legs may accomplish less but not necessarily because it is more stupid. There’s no one metric by which to measure intelligence – some markers, such as tool use, were settled on simply because they were evident in humans.

“I think it’s a mistake to look for a single, definitive thing,” says Godfrey-Smith. “Octopuses are pretty good at sophisticated kinds of learning, but how good it’s hard to say, in part because they’re so hard to experiment on. You get a small amount of animals in the lab and some of them refuse to do anything you want them to do – they’re just too unruly.”



He sees that curiosity and opportunism – their “mischief and craft”, as a Roman natural historian put it in the third century AD – as characteristic of octopus intelligence.

Their great escapes from captivity, too, reflect an awareness of their special circumstances and their ability to adapt to them. A 2010 experiment confirmed anecdotal reports that cephalopods are able to recognise – and like or dislike – individual humans, even those that are dressed identically.

It is no stretch to say they have personalities. But the inconsistencies of their behaviour, combined with their apparent intelligence, presents an obvious trap of anthropomorphism. It’s “tempting”, admits Godfrey-Smith, to attribute their many enigmas to “some clever, human-like explanation”.

A paradox: octopuses have big brains and short life spans. Photograph: Peter Godfrey-Smith

Opinions of octopus intelligence consequently vary within the scientific community. A fundamental precept of animal psychology, coined by the 19th-century British psychologist C Lloyd Morgan, says no behaviour should be attributed to a sophisticated internal process if it can be explained by a simpler one.

That is indicative of a general preference for simplicity of hypotheses in science, says Godfrey-Smith, that as a philosopher he is not convinced by. But scientific research across the board has become more outcome-driven as a result of the cycle of funding and publishing, and he is in the privileged position of being able to ask open-ended questions.

“That’s a great luxury, to be able to roam around year after year, putting pieces together very slowly.”

That process, set in motion by his chance encounter with a cuttlefish a decade ago, is ongoing. Now back based in Australia, lecturing at the University of Sydney, Godfrey-Smith says his study of cephalopods is increasingly influencing his professional life (and his personal one: Arrival, the 2016 film about first contact with “cephalopod-esque” aliens, was a “good, inventive film”, he says, though the invaders “were a bit more like jellyfish”).

When philosophers ponder the mind-body problem, none poses quite such a challenge as that of the octopus’s, and the study of cephalopods gives some clues to questions about the origins of our own consciousness.

Our last common ancestor existed 600m years ago and was thought to resemble a flattened worm, perhaps only millimetres long. Yet somewhere along the line, cephalopods developed high-resolution, camera eyes – as did we, entirely independently.

“A camera eye, with a lens that focuses an image on a retina – we’ve got it, they’ve got it, and that’s it,” says Godfrey-Smith. That it was “arrived at twice” in such vastly different animals gives pause for thought about the process of evolution, as does their inexplicably short life spans: most species of cephalopods live only about one to two years.

The study of cephalopods gives some clues to questions about the origins of our own consciousness. Photograph: Peter Godfrey-Smith

“When I learned that, I was just amazed – it was such a surprise,” says Godfrey-Smith, somewhat sadly. “I’d just gotten to know the animals. I thought, ‘I’ll be visiting these guys for ages.’ Then I thought, ‘No, I won’t, they’ll be dead in a few months.’”

It’s perhaps the biggest paradox presented by an animal that has no shortage of contradictions: “A really big brain and a really short life.” From an evolutionary perspective, Godfrey-Smith explains, it does not give a good return on investment.

“It’s a bit like spending a vast amount of money to do a PhD, and then you’ve got two years to make use of it ... the accounting is really weird.”

One possibility is that an octopus’s brain needs to be powerful just to preside over such an unwieldy form, in the same way that a computer would need a state-of-the-art processor to perform a large volume of complex tasks.

“I mean, the body is so hard to control, with eight arms and every possible inch an elbow.” But that explanation doesn’t account for the flair, even playfulness with which they apply it.

“They behave smartly, they do all these novel, inventive things – that line of reasoning doesn’t resolve things, by any stretch,” says Godfrey-Smith. “There’s still a somewhat mysterious element there.”