The Animal with Nine Semi-Independent Brains

If you cut off a human arm, it stops moving. If you cut off an octopus arm, it will continue to crawl around and try to grab food for several hours.

This happens because two-thirds of an octopus's neurons are located in its arms, not its head. Each limb has its own mini-brain that can make decisions without waiting for a signal from the central nervous system.

An octopus doesn't have to 'think' about moving an arm. The arm tastes the water and feels the texture of a rock entirely on its own. While the central brain might decide to hunt, the arms decide exactly how to untie a knot or open a jar.

This distributed intelligence allows the octopus to multitask in ways humans can't process. It can use one arm to mimic a sea snake while using another to probe a crevice for a crab.

The arms even have a sense of self. They are programmed to recognize their own suckers, which keeps the octopus from accidentally getting tangled in its own knots.

Even more unsettling is that the central brain often doesn't know exactly what the arms are doing until it sees the results.