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" The octopus, although an invertebrate—with no thalamus or cortex to speak of—behaves in ways that utterly belie its primitive label. It has around 500 million neurons, not too far from the numbers in a cat. But the octopus brain is decidedly unusual, with an exceptionally parallel architecture—almost always a positive quality when you are talking about brains. The majority of octopus neurons are to be found not in its brain, but in its arms. In effect, if you include the neuronal bundles in its limbs, the octopus has nine semi-independent brains, making it unique in the animal kingdom. The octopus is also a genius among ocean creatures. It has highly developed memory and attentional systems. In nature, this allows these invertebrates to take on a wide range of shapes to mimic other animals, rocks, or even plants. In the lab, octopuses can distinguish shapes and colors, navigate through a maze, open a jar with a screw-on lid, and even learn by observing the behavior of another octopus—an ability thought previously only to exist in highly social animals. "
― , The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning