The intelligent octopus

I wrote about giant squid recently, which prompted thoughts on a related topic in my head. I’ve read before that octopus are really intelligent creatures. But I’ve never actually investigated that claim very closely; I’ve just taken it at face value. So I wondered – is it true? How smart are octopus, anyways? And how do we know how smart they are? Is there a little octopus IQ test given to all eight-legged water-dwellers currently residing in aquariums around the world?

Remember, an octopus is a kind of cephalopod. Cephalopods are classified by bilateral body symmetry, prominent heads, and a variation on a mollusk foot called a muscular hydrostat – aka arms or tentacles. (FYI, a muscular hydrostat is a piece of anatomy found in any animal that has muscle but no skeletal support and that is used to move stuff – such as food – around. Your tongue is a perfect example of one.) There are two major types of cephalopods – those with a mollusk shell (like the nautilus) and those without (like squid and octopus). The octopus takes being shell-less even one step further than many of its relatives, however, because it has no skeletal support at all. It doesn’t even have any vestiges of an internal shell or bones, unlike cuttlefish or squid. Its body is entirely soft.

You’d probably agree that an octopus does, indeed, have a noticeably large head. And housed within that head is a very large and complex brain. In terms of brain size relative to body mass, octopus brains rank higher than those of reptiles and fish. And while their brains are organized very differently from that of vertebrates, there is no denying that it is highly differentiated and organized into different sensory processing centers. So that brings us to the question of how intelligent these creatures are. If they have such large brains relative to their body size, it would make sense that they would be intelligent, right?

The answer is – maybe. It depends on whom you ask. Some scientists believe that the size of the octopus brain is not a sign of intelligence at all, but merely an indication that their entire brains are not built very efficiently. And there may be some backing for that. In fact, octopus have been discovered with spines lodged in their brains, from where a meal that they were eating went the wrong way through their system and got wedged in their heads. That’s a pretty good indication that there is something a little screwy about the way their digestive and nervous systems intersect.

However, others believe that octopus have large brains because they are intelligent. When they say “intelligent,” what they really mean is capable of highly complex behaviors above and beyond simple survival skills. Here are some examples of the evidence that scientists falling in to this camp cite as backing for their belief.

1. Captive octopi are extremely good escape artists. Lids of tanks must be heavily weight shut, or the creatures will use their arms to push their way out. Even then, the areas around octopi tanks are frequently carpeted instead of tiled. That’s because octopi can manage to squeeze through incredibly small spaces (remember, they have no bones). So even with a heavily weighted lid, they still sneak out. But they can’t crawl across a carpeted floor, so they have nowhere to go but back where they came from. When they do manage to escape, where do they go, you might wonder? Usually, they are found in neighboring tanks, snacking on whatever tasty treats they find there.

2. Octopi are highly adept at changing their appearance. They can change the color and texture of their skin at will to match their surroundings. Their appearance can change from solid colors to lightly speckled to dramatically striped very rapidly during hunting, courtship, male-to-male aggression and in response to a threat. They accomplish this through the stretching of chromatophores, which are multicelled organs consisting of pigment sacs and various colors. When their muscles fibers contract and expand, the chromatophores change within seconds, making the octopus much faster at changing appearance than any land-based camouflage artist.

3. Researchers have trained octopi to recognize shapes, colors and textures in much the same way that they would teach vertebrates like rats. In the 1950s and 1960s, scientists at the University of Cambridge taught young octopi how to recognize small and large squares, horizontal and vertical stripes, and black and white circles. And the octopi were quick learners, too, though it seems like their maximum level of knowledge is ultimately below that achieved by rats.

4. Octopi are highly skilled navigators underwater, and have been trained to run through mazes just like mice and rats. When presented with a new underwater terrain filled with holes, an octopus can quickly learn to navigate through the correct holes to get to its den (and a treat). And once it’s figured the route out, it is much faster at navigating it the second time through.

5. Octopi have been shown to be able to solve the “food in a container” challenge. If given a closed jar with a crab inside (crabs being a very tasty octopus snack), most octopi will figure out how to open the jar and get their treat, even if they’ve never seen such a jar before. Incidentally, this is a classic test of problem-solving ability in vertebrates such as non-human primates.)

6. There was even one study in 1992 claiming to show that octopi could learn by observing other octopi. According to the study, an octopus was allowed to observe another octopus being trained to prefer one color ball (red) to another (white). Later, the observer octopus showed a preference for red balls, even though he had not received the training himself. This study has been met with much skepticism, however, and it is generally agreed that it must be rigorously repeated before it can be taken at face value. To date, no one else has been able to reproduce the results under more rigorously controlled conditions, so the jury is still out on that question.

This debate rages on even now, as scientists try to come up with the perfect experimental set-up to test whether the octopus is really intelligent, or simply very good at navigating in its surroundings. Regardless, I love watching octopi at aquariums. Whether or not they are as smart as some claim, they are fascinating creatures nonetheless. I’ve never seen one in the wild, though I’ve often looked (while scuba diving). Who knows – maybe some day I’ll get lucky enough to see one in the ocean!