§ 1. Ask a biologist what the most intelligent creatures are on Earth, and they'll probably come up with a fairly similar list: larger mammals such as horses, dogs, dolphins, pigs, the great apes as well as some birds like crows and ravens. But now some scientists believe that one of the most intelligent beings on Earth is in fact the octopus  — which doesn't belong to any of these groups.

§ 2. Every schoolchild knows that octopuses have eight legs and can shoot ink while trying to escape from enemies. But there are many other unusual things about octopuses. For example, if an octopus loses a leg, it can grow a new one. It also has three hearts and complex eyes, which seem to belong to a mammal rather than a Sea creature. Octopuses also seem to be experts at escaping  — they have extremely soft, flexible bodies and can escape through holes not much bigger than their eyes.

§ 3. However, even until quite recently, little was known about octopus intelligence. There are several reasons for this. Firstly, octopuses usually live at the bottom of river mouths and seas - areas which are not attractive to researchers. Secondly, they are not social animals so it can be difficult to study their interaction with others. Perhaps most importantly, octopus intelligence is not easy for humans to understand. Octopuses seem like strangers. Scientists need to have a lot of imagination to be able to understand what an octopus is thinking!

§ 4. In the 1950s, the US Air Force sponsored scientists to study the way octopuses use their brains. They hoped that they could use this knowledge to help them build better computers. However, their brains were so complex that the scientists quickly gave up. And even today the octopus brain is a mystery. Octopuses have a very complex nervous system and recent research suggests that they have some of their intelligence inside each arm, which means that each arm can 'think' for itself. It also appears that they have good memories, perhaps similar to a cat's. Some Octopuses in laboratories seem to play with objects as if they were toys  — a sure sign of intelligence. Others could pick up complicated skills like opening jars.

§ 5. Perhaps the most striking thing about octopuses is their ability to change their colour and body pattern. They do this to camouflage themselves and also to communicate with others. They can completely change their appearance in less than a second. A scientist once observed an octopus that changed its appearance nearly 1,000 times during seven hours of feeding!