Thinking in the Deep Inside the Mind of an Octopus

If we met an alien whose intelligence derived through an entirely separate provenance from ours, would we recognize the sparkle in each
other’s eyes? In “Other Minds,” Peter Godfrey-Smith hunts the commonalities and origins of sentience. He is an academic philosopher but
also a diver. Watching octopuses watching him, our author considers minds and meanings.

Octopuses and cuttlefish — cephalopods — make surprisingly good foils here. Our last common ancestor, 600 million years ago, was a
wormlike creature. Cephalopods are therefore an independent voyage into complexity. “If we can make contact with cephalopods as sentient
beings, it is . . . because evolution built minds twice over,” Godfrey-Smith writes. “This is probably the closest we will come to meeting an
intelligent alien.” When seeking other minds, we find that “the minds of cephalopods are the most other of all.”

After hundreds of millions of years, we encounter beings familiarly strange, yet strangely familiar. Bone-free and shape-shifting, octopuses’
“body of pure possibility” lets them flow through cracks the width of their eyes. Vertebrates share a particular, inherited nervous-system
architecture. Cephalopods, though — different. With neuron numbers comparable to those of mammals, octopuses’ brains are distributed;
their arms harbor nearly twice as many neurons as their central brain (through which, incidentally, their esophagus passes. Not to mention:
They have three hearts). Neural loops may give the arms their own form of memory. Their skin itself senses light and responds. An octopus
is so suffused with its nervous system that it has no clear brain-body boundary.

Thus most amazing: recognition, their “sense of mutual engagement,” their disarming friendliness. “You reach forward a hand and stretch
out one finger, and one octopus arm slowly uncoils . . . tasting your finger as it draws it in. . . . Behind the arm, large round eyes watch.”
Godfrey-Smith watched his dive partner as “an octopus grabbed his hand and . . . Matt followed, as if he were being led across the sea floor
by a very small eight-legged child.” Ten minutes later they arrived at the octopus’s den.

Octopuses have personality (cephonality?), some shy, some confident or “particularly feisty.” Some — not all — play, blowing and batting
bottles around. They recognize human faces; one study confirmed that giant Pacific octopuses could even distinguish people wearing
identical uniforms. Octopuses become fond of certain people, yet at others they squirt disdainful jets of water. One cuttlefish squirted all new
visitors, but not familiar faces. (Giant cuttlefish look “like an octopus attached to a hovercraft” and seem “to be every color at once.”) So, like
humans, cephalopods can categorize. Some squirt their lights out at night, short-circuiting them. They “have their own ideas.”

The search for intelligent life starts astonishingly far back. Even bacteria sense and respond to the world, though that’s most likely analogous
to motion detectors rather than anything felt. Still, their complexity is mind-blowing. To approach the nutritious and avoid the noxious, the
author says, a bacterial cell “uses time to help it deal with space. . . . One mechanism registers what conditions are like right now, and
another records how things were a few moments ago. The bacterium will swim in a straight line as long as the chemicals it senses seem
better now than those it sensed a moment ago. If not, it’s preferable to change course.”

Much later, multicelled gelatinous animals evolved neurons. Nerves underneath coordinated cells’ “tiny contractions, contortions and
twitches” into propulsive pulsing. Other nerves wired light-sensing organs above to coordinate day-night rhythms. The motion-controlling
system may have eventually entangled the light sensors, whence light sensors aided motion guidance. Thus neurons convened into a
“chemo-electrical storm of repurposed signaling” — brains. (Deadly evidence: Box jellyfish, some of whose two dozen eyes have lenses and
retinas like ours, can navigate by watching landmarks on the shore as they pulse along at three knots.)

Then, a half-billion years ago, Cambrian animals first watched, seized and fled other animals. Senses, nervous systems and behaviors
escalated an arms race against the senses and behaviors of others. If a yardlong cockroach-looking appetite with two graspers on its head is
swimming rapidly at you, “it’s a very good thing to know, somehow, that this is happening, and to take evasive action.” With better sensory
processing and a need for decisions (fight or flee), the Cambrian delivered Earth’s first information revolution. “From this point on,” GodfreySmith
emphasizes, “the mind evolved in response to other minds.”

Amid explosive evolution, you’d assume that speedy, grasping creatures evolved often. Surprisingly, of about 34 basic animal body plans
(phyla), only arthropods (insects, crabs), vertebrates and one subgroup among mollusks — cephalopods — evolved “complex active bodies.”
Only vertebrates and cephalopods developed large, complex nervous systems.



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