The giant octopus has a reddish-brown body, called the mantle, plus four pairs of arms, measuring on average about 4.9 m long. The record weight for a giant octopus is 272 kg, but most weigh about 23-41 kg. Newly hatched young are the size of a grain of rice. Octopuses have the most complex brain of the invertebrates (animals without backbones). Like vertebrates, they also have long term and short-term memories. Octopuses learn to solve problems by trial-and-error and experience. Once the problem is solved, octopuses remember and are able to solve it and similar problems repeatedly.