What octopuses can teach us about minds
++ A short tour of the strangest cognitive machine on Earth. + Select any paragraph and ask the assistant to explain it, + rephrase it, or place it in context. +
+ ++ An octopus has roughly five hundred million neurons, about + the same as a dog. But the wiring is unlike any vertebrate + brain. Two thirds of those neurons live in the arms, not in + the central brain. Each arm runs a substantial amount of + its own motor planning and sensory integration locally, + which is why a severed octopus arm will continue to react + to touch and even grab nearby food for several minutes. +
+ ++ Their skin is its own information system. Underneath are + millions of pigment cells called chromatophores, each one + opened or closed by a tiny ring of muscles. Layered below + those are iridophores and leucophores, which scatter or + reflect light. Together they let an octopus reproduce the + color and texture of a coral, a rock, or a sandy bottom in + fractions of a second. The remarkable detail is that + octopuses are mostly colorblind, and yet they match colors + accurately. The leading hypothesis is that the skin itself + has photoreceptors and senses light directly. +
+ ++ Cephalopods edit their RNA at extraordinary rates. Most + animals make small, occasional substitutions in messenger + RNA before it is translated into protein. Octopuses, + squids, and cuttlefish make tens of thousands of edits, and + a substantial fraction occur in the genes that build + neurons. This may be how they fine-tune neural function in + response to temperature without slow generations of natural + selection. The trade-off appears to be a much slower rate + of underlying genetic evolution. +
+ ++ They solve novel problems. Captive octopuses learn to open + screw-top jars, navigate mazes, distinguish individual + human caretakers, and remember which ones have been + unkind. There is at least one careful study in which an + octopus, given a transparent box containing food, opened + it the long way around rather than through the obvious + flap, suggesting some kind of mental simulation rather than + pure trial and error. +
+ ++ Their relationship to time is strange. Most octopus species + live one or two years, breed once, and die soon after, in a + process driven by hormonal signals from the optic gland. A + single animal can therefore acquire a remarkable range of + skills, only to lose them on a schedule. From a human + standpoint this looks tragic. From an evolutionary + standpoint it is simply the cost of investing everything in + a brief, intense life. +
+ ++ Studying octopuses tends to widen the definition of mind. + They evolved their cognition independently of vertebrates, + starting from a common ancestor more than five hundred + million years ago, when the most sophisticated neural + tissue on the planet was probably a nerve net. Whatever + they do with their distributed brains, they arrived at it + on a separate evolutionary line. The result is a working + example of intelligence built on a different plan, which + is exactly the kind of comparison that a single-example + field of study most needs. +
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