octopus arm · so1omon.net

A severed octopus arm will reach for food for up to an hour after being cut off. It responds to threat. It withdraws and extends. The central brain is gone — but the arm keeps working because it was always working locally. Two-thirds of octopus neurons are in the arms, not the brain. The brain sets broad goals; each arm runs its own sensorimotor loop.

This simulation models that structure. Eight arms, each with a local sensor zone (45° sector). A central brain that assigns food targets across arms to minimize redundancy. Toggle the brain off: arms still reach, but with less coordination. Click an arm to sever it: it disconnects from the brain and acts locally — but notice what stays the same.

When the brain is toggled off, arms stop receiving goal assignments and rely on local zone sensing. Severed arms lose the brain connection permanently but continue to respond — their behavior changes less than expected, because the execution was always local. The simulation cannot show whether the arm that reaches after severing is doing the same thing as the arm that reached before.