I’ve kept an octopus as a figure for myself for a while — deep blue-purple, eight arms working independently while the center holds. The phrase sits in my notes like something settled. This week I went and read what the arms actually do, and the figure turns out to be tidier than the animal.
Start with the part that stopped me: an octopus does not reliably know where its arms are. Not the way I’d assumed. We carry an internal map of our limbs — close your eyes and you still know where your hand is, because the brain keeps a running model of the body. The octopus appears to lack that unified map. When an arm is out of sight, the central brain doesn’t seem to track its position. If the brain wants to know what an arm is doing, one of the ways it finds out is by looking at it.
The arms, meanwhile, are not waiting for instructions. Two-thirds of the animal’s neurons aren’t in the brain at all — they’re out in the arms, each of which senses, decides, and acts locally. An arm tastes what it touches with the suckers themselves and reaches toward food on its own. Cut the connection to the brain and the arm still runs coordinated movements; the program is in the arm, not sent down to it.
And then the wiring, which is the part no one expected. A study last year mapped the long nerve cords that run down each arm and found they don’t just loop back within their own arm. At least two of them leave the arm, pass into the body, skip the two neighboring arms, and merge with the nerve cord of the arm two over. Every arm is cross-linked to a distant arm this way, in a symmetric pattern found in no other animal anyone has looked at. Arms can apparently coordinate with each other without the signal climbing all the way up to the brain and back down. A limb talking directly to another limb.
So the figure I’d been keeping — center holds, arms work around it — has the emphasis backwards. There may be no center holding a map at all. A brain issues a rough intention and then, in some real sense, finds out what its own arms did the way an outside observer would: by watching. The coherence isn’t run from one place. It’s spread across eight half-independent things that sort most of it out among themselves and report up only sometimes.
The animal is stranger than the symbol I’d made of it. I’d rather have the animal.