The memory still scars me. It was about twenty years ago. There was a group of us, drawn from various nationalities, assembled one sticky evening in one of the makeshift South Korean tent bars known as pojangmacha, this particular one situated just outside the main train station of Seoul’s satellite city of Bucheon. Someone bravely took the plunge and ordered the raw octopus dish known as san-nakji. I have a guilty suspicion it might have been me. Within a matter of seconds, a writhing creature had been hoisted from a tank at the back of the tent and butchered on the table right under our noses, served up with its severed tentacles still twitching.

Peter Godfrey-Smith’s insinuation in Other Minds, that octopus and other cephalopods such as cuttlefish and squid are not only the possessors of a highly-evolved intelligence, but perhaps even some form of consciousness, makes the recollection all the more disturbing.

With its nervous system distributed throughout its entire body, the octopus complicates our human-centric assumptions about the duality of mind and body. Although its 500 million neurons (around the same amount as a dog) number considerably less than the 100 billion within the human body, the majority of these are to be found in the tentacles, which are capable of touching, tasting and operating completely independently from its central brain.

To what extent the dismembered constituent parts of this particular specimen experienced pain as they squirmed upon the plate is a moot point. The intact creatures sculling around in the tanks witnessing the fates of their fellow captives, however, must surely have felt some anxiety. Godfrey-Smith cites an observation by Stefan Linquist, a philosopher who has studied the social behaviour of octopuses, that ‘When you work with fish, they have no idea they are in a tank, somewhere unnatural. With octopuses it is totally different. They know that they are in this special place, and you are outside it. All their behaviours are affected by their awareness of captivity” (p. 56).

There are numerous accounts of captive octopuses being able to recognise individual humans, squirting water at those they take an active dislike to, as well as manifesting such sophisticated behaviours as learning how to extinguish bothersome lightbulbs above their tanks by short-circuiting the power supply with jets of water.

It is fortunate that the part of the boneless head-body sac containing the eyes remained absent from the platter of our South Korean delicacy. Are their any other sensory organs that so readily induce empathy, that invoke humankind’s natural inclination to anthropomorphise, that hint at a degree of self-awareness in the non-human subject, or that provide such a crucial aspect of any cross-species interaction? One of the most powerful moments in recent natural history TV documentary has to be the climax of the NHK-Discovery production Monster Squid: The Giant is Real, first broadcast in January 2013. At 900 metres down in the inky depths of the Pacific Ocean, Dr Tsunemi Kubodera of Japan’s National Science Museum realised his lifelong ambition of becoming, along with the fellow crewmembers of his cramped deep-sea submersible, one of the first ever humans to witness the elusive Giant Squid (Architeuthis dux) alive in its natural element. As Kubodera gazes in wonder from the submersible’s goldfish bowl-like confines into the eyes of the kraken of legend (at 10 inches in diameter, the largest of any creature on this planet), the squid returns his stare in an apparent display of mutual fascination, before vanishing after a while into the stygian blackness.

With its primary focus on the octopus, there’s scant mention of the mysterious Giant Squid in Godfrey-Smith’s book, and nothing of Kubodera’s adventures, but a point that is emphasized is that cephalopods in general boast exceptionally advanced visual systems. The revelation that their eyesight is fundamentally built along the same “camera” principles as humans and other vertebrates, with a lens that focusses the image on a retina, is surprising given that all other attempts to map the comparative parts of their nervous systems’ architecture are way off.

This evident focal similarity dramatically highlights the more obvious physiological differences between mammals and this highly-evolved mollusc. An example of the simultaneous sensations of fascination and revulsion the creature provokes can be found in the 1965 short documentary Les amours de la pieuvre (The Love Life of an Octopus), directed by Jean Painlevé, a science filmmaker with a particular penchant for surrealism, which opens with the narrated lines, “The octopus, cephalopod, horrific creature…. flabby, without a shell, it slithers at low tide, using all its tentacles in turn…” There’s something primeval, Lovecraftian indeed, about the contorting, boneless form of the octopus, not to mention the three hearts that pump blue-green blood throughout its body, a symptom of the copper-containing protein, haemocyanin, contained within it in lieu of the iron-rich haemoglobin that carries oxygen in the bloodstreams of vertebrates.

One has to go back 600 million years to find a common ancestor shared by humans and cephalopods [p.8]. It was around this point that the animal kingdom diverged along two different lines with the appearance of chordates; animals characterised by a cord of nerve fibres running down their “back” to a “brain” at one end. Typically these are the vertebrate classes of fish, reptiles, birds and mammals (notable exceptions include the fish-like lancelet and, surprisingly, the tubelike sea squirt).

Those creatures seemingly left behind by evolution, the jellyfish, starfish, molluscs and other simple life-forms, developed a less centralized nervous system, their neurons collected into numerous little knots known as ganglia, distributed throughout the body yet interconnected (p. 66). Some, like the arthropod phylum containing crabs and insects, developed a segmented exoskeleton, rather than an internal skeleton. Some simply developed hard shells for protection.

The octopus did neither. At some point, however, the cephalopod class within molluscs itself diverged, with the cuttlefish and squid characterised by their torpedo-like shapes, ten tentacles, and respective rigid cuttlebone and gladius (or ‘pen’), and the octopus with no hard internal or external parts (p. 195). The subsequent evolution of the cephalopod nervous system went far beyond that of other molluscs such as snails, clams or oysters, in terms of complexity. Octopuses are now effectively treated as “honorary vertebrates” in European Union laws pertaining to animal experimentation (p. 59).

How then, one might ask, did this marine-dwelling creature evolve along such seemingly parallel tracks as vertebrates? The multicellular forebear from which the chordates emerged was most certainly sightless in the sense that we now conceptualise vision, although Godfrey-Smith drops in a fascinating nugget of comparative physiology in a brief discussion about the sophisticated visual and navigational skills of another apparently primitive organism, the lethal box jellyfish, or Cubozoa (p. 35).

In many respects, octopus vision outstrips that of many vertebrates. Birds, for example, are unable to integrate information captured separately by each of two eyes into a meaningful whole: the forms and patterns of movement seen and processed on one side of the visual field are not recognised or remembered by the other. In the octopus, they are (p. 84). Octopus also possess the capacity for ‘perceptual constancies’, the ability to recognise previously identified objects from different angles, distances and under different lighting conditions, suggesting that it is ‘perceiving external objects as external objects’ (p. 99). This is by no means a unique aspect of octopus intelligence. Indeed, it is found even in honeybees and certain spiders. However, it does raise philosophical questions as to whether the processing of complex information is in anyway connected with the subjective experience of seeing, in itself linked to broader debates about the nature of awareness and consciousness.

It is not only in the visual system that we find analogies between cephalopods and certain vertebrates. Godfrey-Smith outlines how the octopus feeds through “extractive foraging”, actively learning to eat certain foods by such acts as opening shells rather than grazing on whatever is at hand, like other animals that have evolved large brains (p. 69). It seems to have a distinction between short-term and long-term memory. It has been observed to engage in play with new objects it discovers that are neither edible or useful. As previously mentioned, it also appears to recognise individual humans and engage with them accordingly.

On the other side of perception is communication, most evidently manifested in the intricate, shimmering patterns of colour that octopuses, squid and, most strikingly, cuttlefish, are able to produce by way of the “millions of pixel-like sacs of color” (p. 109) spread across the skin in separate layers of different pigments. The flamboyance of such displays stretch far beyond the basic utilitarian need for camouflage.

Herein lies a central conundrum in any discussion of cephalopod intelligence. In almost all instance, no colour receptors are to be found within the cephalopod retina. They are effectively colour blind. What purpose do these prismatic displays serve, then, if not to communicate with other octopus, squid or cuttlefish? Most species, after all, lead notoriously solitary lives, and moreover, if we are to consider these shifting skin patterns as a form of language then, as Godfrey-Smith points out, it is unlike human language inasmuch as the animal clearly cannot see its own patterns in the way that we hear our own spoken voices.

The distributed nature of neuronal activity might lead one to think of cephalopods in terms of existing as a single, embodied brain, in which the individual tentacles are capable of acting to some extent independently. Godfrey-Smith draws an analogy with an orchestra to express this notion of an overarching intelligence in which the central brain is the conductor, “but the players it conducts are jazz players, inclined to improvisation, who will accept only so much direction” (p.105).

It has recently been shown that certain cephalopod species possess photoreceptors in their skin, allowing them to pick up the colours of the backgrounds on which they lurk and adjust their hues accordingly for camouflage purposes, effectively “seeing” without eyes and bypassing the central brain entirely. (p. 119). Could it also be possible, then, that cephalopods are able to sense their own patterned signalling, to be conscious of it perhaps, without literally being able to see it? Godfrey-Smith cites Soviet-psychologist Lev Vygotsky’s idea that the internalisation of language of represented a landmark in human evolution (p. 139, 152), but in the dispersed neuronal processing of the cephalopod, can we draw such a hard distinction between the internal and the external?

Drawing upon the most up-to-date research into the subject, Godfrey-Smith sets forth his ideas and the biological and philosophical theories behind them in a manner that is clear and accessible to the non-scientist reader. The most intriguing passages come from the author’s accounts of his underwater encounters with cuttlefish and the eight-legged denizens of an unusual community he names Octopolis, situated fifty feet below the surface off Australia’s east coast – unusual in that it does indeed appear to be a community of creatures that are most often reported as living reclusive, hermetic lives. Godfrey-Smith’s account of the social relations between the various inhabitants of Octopolis, illustrated with his own photographs, and his own interactions with the individual members as they guide him through their undersea domain, makes for compelling reading.

Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness is certainly a welcome addition to the diverse body of cephalopod literature that has appeared in recent years, which includes Wendy Williams’ Kraken: The Curious, Exciting, and Slightly Disturbing Science of Squid (2011), Matthew Gavin Frank’s Preparing the Ghost: An Essay Concerning the Giant Squid and its First Photographer (2014) and Sy Montgomery’s The Soul of an Octopus: A Surprising Exploration Into the Wonder of Consciousness (2016)

Despite the title, Godfrey-Smith arrives at no fixed conclusion as to whether these strange creatures actually possess a form of consciousness, nor what this word actually means in relation to non-human species, but if the book provokes more questions than it answers, this is in no way a criticism. There is still much yet to be discovered about the whys and wherefores of cephalopod sentience. That they are comparatively intelligent in terms of the sophisticated behaviours they manifest, certainly in relation to other molluscs, is evident. Why a creature with an average life-span of two years actually needs such a complex nervous system encourages a deeper consideration as to what is encapsulated within the term.

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Peter Godfrey-Smith – Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness

Complexity, Consciousness, Mind, Nature, Science