Consider the octopus. Smart and sophisticated, it has a brain larger than that of any other invertebrate. With 500 million or so neurons, its nervous system is more typical of animals with a backbone. In lab experiments, the octopus can solve mazes, open jars, and complete tricky tasks to get food rewards. In the wild, they’ve been observed using tools—a benchmark of higher cognition.
Researchers have long been awed by their ability to camouflage, regenerate lost limbs, and release ink as a defense mechanism. They have been used for studies on how psychedelics affect brains, and they may even dream. Importantly, research shows that they also seem to experience pain.
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