Why Each Octopus Arm Has a Mind of Its Own

Two-thirds of an octopus's neurons are in its arms--each operating independently--including the one it uses to have sex. Octopuses are clever enough to unscrew jars from the inside and throw sand at their annoying neighbors. But only a fraction of their smarts come from their doughnut-shaped brains. Over two-thirds of their roughly 500 million neurons reside in eight sucker-studded arms--a kind of distributed intelligence unique to cephalopods. Each of these powerful appendages can move in any direction and taste and feel with exquisite sensitivity.