An octopus's nervous system is distributed, not centralized like ours

Montgomery opens with the strangeness of octopus neuroanatomy: roughly two-thirds of an octopus's several hundred million neurons reside not in its central brain but distributed throughout its eight arms, each capable of some degree of independent sensing, tasting, and even limited decision-making without waiting for instructions from the head.

This means an octopus's arms can react to touch, taste a surface through specialized receptors along the suckers, and execute exploratory movements with a level of autonomy no vertebrate limb has — closer to eight semi-independent problem-solvers loosely coordinated by a central brain than to arms in the human sense.

Montgomery uses this to reframe the entire question of octopus intelligence: rather than asking whether an octopus's brain is smart in a way comparable to a mammal's, the more accurate question is what kind of cognition emerges from a body where thinking is distributed across the whole organism rather than concentrated in one place. Intelligence doesn't require a centralized brain — it can be a property of the entire distributed nervous system, arms included.