How Smart Are Octopuses? Problem Solving and Escapes

How intelligent are octopuses compared with other animals?

Among animals without a backbone, octopuses, squid and cuttlefish stand far above the rest in learning and problem solving. Comparing them with vertebrates is harder, because most intelligence tests were designed for apes, monkeys and birds, which see, move and handle objects very differently. Even so, octopuses perform well on many tasks that also challenge mammals and birds, and many researchers place them among the smartest animals on Earth.

What makes them remarkable is how different they are from other clever animals. Crows, parrots, dolphins and apes are long-lived, social vertebrates that learn from parents and companions, as described in how smart are crows? Octopuses are short-lived, solitary mollusks, related to snails and clams, that never meet their parents.

A brain spread through the arms

The common octopus has about 500 million neurons, roughly as many as a dog has in its cerebral cortex. Only about a third of them are in the brain, a ring of tissue around the esophagus protected by cartilage. The other two-thirds are in the nerve cords of the eight arms.

This means the arms do much of their own thinking. An arm can search a crevice, taste what it touches and decide whether to grab it with little input from the brain, and a severed arm still reacts to touch for a while. The brain sets the goals, such as “find food over there”, while the arms work out the details. Inside the brain, a region called the vertical lobe plays a central role in learning and memory. How the arms gather information is explored in does an octopus have arms or tentacles?

What experiments show: mazes, jars and puzzle boxes

Scientists have studied octopus learning for more than 70 years, much of it at the marine research station in Naples, Italy. From the 1950s onward, common octopuses were trained to tell apart shapes, sizes, brightness levels, and horizontal from vertical rectangles, and to remember what they had learned.

• Mazes and navigation: in tanks, octopuses learn the way through simple mazes. In the wild, they travel out to hunt and return to their den by a different route, which suggests they remember the layout of their surroundings.
• Opening jars: in a 1990 study, common octopuses were given a crab inside a glass jar closed with a plug. They learned to pull out the plug and got faster with practice.
• Puzzle boxes: later studies offered transparent boxes with food inside that opened only if a part was pulled, pushed or slid the right way, and many octopuses learned the trick.
• Learning by watching: a famous 1992 study reported that octopuses copied a choice made by another octopus they had watched. Other scientists have struggled to repeat the result, so this claim remains disputed.

Tool use: the coconut octopus

The most celebrated case of octopus tool use comes from the veined octopus (Amphioctopus marginatus), a small species of the tropical western Pacific and Indian oceans. Biologists filming in Indonesia, reporting in 2009, watched these octopuses dig up discarded coconut shell halves from the seabed, stack them, and carry them under the body while walking stiffly on their arm tips. When they stopped, they turned the shells into a shelter or pulled two halves together around themselves.

Carrying the shells is clumsy and gives the octopus no benefit until later, which is why researchers classed it as tool use, a behavior once thought unique to people and a few other animals. Other octopuses also gather shells and stones to block the entrance of their dens.

At a site in eastern Australia, gloomy octopuses (Octopus tetricus) have been filmed throwing silt and shells by blasting them with a water jet from their funnel. A 2022 study reported that some throws appeared to be aimed at other octopuses.

Recognizing people, play and personality

Octopuses seem to know who is who. In a study at the Seattle Aquarium published in 2010, two people dressed identically repeatedly visited giant Pacific octopuses. One always fed them; the other always touched them with a bristly stick. Most octopuses soon treated the two differently, approaching one and showing defensive behavior, such as aiming jets of water, toward the other.

Octopuses also show behavior that looks like play. In one well-known study, giant Pacific octopuses repeatedly squirted jets of water at a floating pill bottle, sending it to the water inflow so the current carried it back, much like bouncing a ball. Studies of red octopuses in the 1990s found consistent differences between individuals in boldness and activity, which researchers described as personalities.

Famous octopus escapes

Octopuses are notorious escape artists, helped by their curiosity, strength and boneless bodies. The best-known case is Inky, a common New Zealand octopus at the National Aquarium of New Zealand in Napier. In 2016 he apparently slipped through a gap at the top of his tank, crossed the floor at night, and went down a drainpipe about 50 m (160 ft) long that led to the sea. He was never found.

Aquarium staff around the world tell similar stories of octopuses lifting lids, unscrewing caps, unplugging drains and taking apart equipment. Many aquariums now use locking lids and give their octopuses puzzle feeders and toys to keep them busy.

How different is an octopus mind?

The last common ancestor of octopuses and humans lived more than 500 million years ago and was probably a small, simple, wormlike animal. Everything clever about octopuses evolved independently, which is why the philosopher Peter Godfrey-Smith has compared meeting an octopus to meeting an intelligent alien.

Their senses are unlike ours. The common octopus appears to be color-blind, yet it matches the colors of its surroundings, and its suckers taste as well as touch. It learns alone, without parents to copy, and it lives only one or two years.

These findings have changed the law. In the UK, a 2021 review commissioned by the government concluded that octopuses and other cephalopods are sentient, able to feel pain and distress, and the Animal Welfare (Sentience) Act 2022 now includes them. In the European Union, cephalopods used in scientific research have been protected since a 2010 directive.