Octopuses display remarkable intelligence, but much of it does not originate in their central brain. More than two-thirds of an octopus's roughly 500 million neurons are located in its eight arms, giving rise to a form of distributed intelligence that is unique among cephalopods and largely unmatched elsewhere in the animal kingdom.

Each arm can move independently in any direction while sensing taste and touch with remarkable precision, and a nerve ring links all eight arms so they can coordinate movement without constant direction from the brain. Scientists studying this system are still probing anatomical, behavioural and philosophical questions about what it means for an animal to have, in effect, several semi-autonomous minds working together.