3 Octopus : Octopuses are incredibly intelligent, and one of the smartest invertebrates in the world. Octopuses have displayed the ability to use both short and long term memory. Many aspects of their intelligence and behaviour is still a mystery to biologists, and it’s not certain how much influence their intelligence has on their behaviour. Unlike humans octopuses don’t learn from observing their parents, and actually spend very little time with their parents. Octopuses have a very complicated nervous system, two thirds of which is located in the nerve cords of it’s arms, which have limited functional autonomy.