Most of an octopus's brain is in its arms.
An octopus has about 500 million neurons, and around two-thirds of them are in its eight arms, not its head. Each arm can taste, touch and make decisions on its own. An octopus doesn't just move its arms; in a sense, it negotiates with them.
Octopuses are among the most intelligent invertebrates on Earth. They solve puzzles, open jars, escape from aquariums and use tools; the veined octopus has been filmed carrying coconut shell halves to use as a portable shelter. Their nervous system is built very differently from ours.
A common octopus has roughly 500 million neurons, a number comparable to a dog's. But only a minority are in the central brain wrapped around its oesophagus. About two-thirds are distributed along the arms, where clusters of nerve cells control the hundreds of suckers.
Those suckers are covered in chemical receptors, so an octopus effectively tastes what it touches. Experiments show arms can carry out complex movements with limited input from the brain: a severed arm, for instance, will still reach and grasp. Researchers think the brain sets broad goals while the arms work out many of the details themselves, a kind of distributed intelligence.
The octopus's intelligence evolved independently of ours. Our last common ancestor was probably a simple worm-like creature over 500 million years ago. That makes octopuses one of the closest things we have to studying an alien mind: a creature that arrived at problem-solving and curiosity by a completely separate route. The philosopher Peter Godfrey-Smith explores this in his book Other Minds.
Source: Wikipedia — Octopus · Text summarised from Wikipedia (CC BY-SA 4.0)
