Octopuses also have personalities. We used the same kind of setup people use when they want to study human personalities. You just ask what do the animals commonly encounter during the day in different situations and look at the variability. We put them in three common situations: alerting (opening the top of the tank), threatening (touching the octopus with a test tube brush) and feeding (the octopus was given a crab to munch). This takes awhile because we tested 33 animals, each for two weeks. We found there are three dimensions and we settled for names: activity, reactivity and avoidance. Avoidance is how shy you are. Activity is if you are very active or passive. And reactivity indicates whether you are very emotional or more blasé. Octopuses can have any mix of those traits. We didn't take it any further, but there's a former graduate student in Australia looking at the extent to which personality affects ecology.
Do octopuses have brains?
The molluscan nervous system has a bunch of paired ganglia (a cluster of nerve cells), which in an animal like a clam or a snail are not very big and are widely distributed through the body. They control different functions and are located in different areas. Well, the cephalopods—that's the octopuses, squids and cuttlefish—they are unique in that all these ganglias have condensed so they form a centralized brain. The other thing that is unique amongst the mollusks is there are two areas of this brain that have developed that are specialized for memory storage. It's not just that the brain is larger and condensed, but they have areas of the brain dedicated to learning. That's the kind of thing we humans have, but it’s a completely different brain.
By invertebrate standards it’s a huge brain, but by vertebrate standards, it’s a small brain. What's interesting about the octopus is about one third of the neurons (nerve cells) are in the brain. They have a huge neural representation in the arms, and there's a ganglion controlling every sucker, so there's quite a bit of local control. As humans, we're very proud of having a pincer grasp—the thumb and forefinger—and we say that's responsible for our ability to manipulate the environment so well. The octopus can fold the two sides of its sucker together to form a pincer grasp and it can do that with every single one. It has a hundred pincer grasps.
Why do you think octopuses evolved such big brains?
Probably because the tropical coral reef is the most complex environment in the world. There's such a huge variety of situations, lots of kinds of prey, lots of predators, and if you are not armored, you'd better be smart. The octopus has gone the smart route. Also, we talk about mammalian intelligence evolving in social situations, but clearly the octopus, a solitary organism, has evolved intelligence to solve ecological problems.
Do octopuses often cause trouble in aquariums?
They are very strong, and it is practically impossible to keep an octopus in a tank unless you are very lucky. One of the early researchers said if you leave a floating thermometer in a tank, it will last about five minutes. Octopuses simply take things apart. I recall reading about someone who had built a robot submarine to putter around in a large aquarium tank. The octopus got a hold of it and took it apart piece by piece. There's a famous story from the Brighton Aquarium in England 100 years ago that an octopus there got out of its tank at night when no one was watching, went to the tank next door and ate one of the lumpfish and went back to his own tank and was sitting there the next morning. The aquarium lost several lumpfish before they figured out who was responsible.