Most of an octopus's neurons are in its arms

An octopus has around 500 million neurons — comparable to a dog — but nearly two-thirds of them live in its arms, not its head. Each arm can taste, touch and act semi-independently. It may be the closest thing on Earth to meeting an intelligent alien.

— Peter Godfrey-Smith, Other Minds: The Octopus and the Evolution of Intelligent Life — 2016
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