Why Octopuses Are Smarter Than They Look

At first sight, an octopus seems an unlikely candidate for the title of the ocean's cleverest animal. It has no bones, it lives for only a few years, and it is, by all accounts, rather solitary. Yet scientists who study these creatures keep arriving at the same conclusion: octopuses are remarkably intelligent, and they achieved it by a route completely different from our own. The most obvious difference lies in the nervous system. An octopus has roughly five hundred million neurons, a number comparable to that of a dog, but around two thirds of them are located not in the brain but in the arms. This means that each arm can, to a large extent, taste, touch and make decisions independently. Researchers have observed arms exploring a crevice on their own while the animal's eyes were fixed on something else entirely. Evidence of problem-solving is abundant. Captive octopuses have learned to unscrew jars from the inside, and some have become notorious for escaping from their tanks at night, slipping through gaps barely wider than their eyes and, according to several aquarium staff, occasionally helping themselves to the fish in neighbouring tanks. In 2009, researchers in Indonesia filmed veined octopuses collecting discarded coconut shells, carrying them across the seabed, and assembling them into a shelter when needed. Many scientists regard this as a genuine example of tool use in an invertebrate. What makes all this puzzling is that octopuses do not seem to need such intelligence in the way that monkeys or dolphins do. They do not live in groups, and they rarely meet their parents, since most species die shortly after their eggs hatch. Learning from elders, which is so central to other clever animals, is therefore almost impossible. One popular explanation is that a soft body without a shell forces an octopus to rely on its wits to survive among predators; another suggests that a varied diet of crabs, shellfish and fish demands flexible hunting methods. Whatever the cause, the octopus challenges a comfortable assumption, namely that complex thinking must resemble our own. Its ancestors separated from ours more than five hundred million years ago, so its intelligence evolved independently. In that sense, meeting an octopus may be the closest we will ever come to encountering a different kind of mind.