Why are octopuses so smart?

Octopuses are smart in a way that is very different from us. A common octopus has around 500 million neurons, close to the number in a dog's cerebral cortex, and about two thirds of them sit in its arms rather than its head. Each arm can feel, taste and react largely on its own, which lets the animal explore, solve problems and escape in ways that still surprise scientists.

A brain spread across the body

Most animals run everything from one central brain. An octopus shares the work. The central brain sets the goal, and the arms work out much of the detail themselves, such as how to grip, bend or search a crack in a rock. The suckers carry chemical receptors, so an octopus can taste what it touches.

What they can do

• Open screw-top jars to reach food inside, as seen in labs and aquariums.
• Change colour and skin texture in a fraction of a second to blend in, using special cells in the skin.
• Carry coconut shells or seashells around and use them as a shelter, in at least one species.
• Tell individual people apart, behaving differently with different keepers in aquarium studies.

The strange parts

Octopuses have three hearts and blue blood, because their blood uses copper rather than iron to carry oxygen. Most species are thought to be colour blind, yet they match the colours around them remarkably well, and scientists are still debating how.

Short lives, learned alone

For all that intelligence, most octopuses live only a year or two, and many species die soon after breeding. They also learn almost everything alone, with no parents to teach them, which makes their problem solving even more impressive.

In 2022 the UK's Animal Welfare (Sentience) Act recognised octopuses, along with crabs and lobsters, as sentient beings, following a government-commissioned review of the evidence.