Are We Smart Enough to Know How Smart Animals Are?(76)
The Mollusk Mind
As a biology student, my favorite textbook was Animals Without Backbones. It may seem an odd choice given my current interests, but I was awestruck by all the exotic life-forms that I had never heard about or could scarcely imagine, some of them so tiny that you needed a microscope to see them. The book went into great detail of all invertebrates—from protozoans and sponges to worms, mollusks, and insects—which together make up 97 percent of the animal kingdom.20 Whereas cognition research focuses almost entirely on the tiny vertebrate minority, it is not as if the rest doesn’t move, eat, mate, fight, and cooperate. Obviously, some invertebrates show more complex behavior than others, but they all need to pay attention to their surroundings and solve problems that present themselves. In the same way that almost all these animals have reproductive organs and digestive tracts, they can’t survive without a degree of cognition.
The brainiest of the bunch is the octopus, which is a soft-bodied cephalopod, or “head-footed” animal. This is an apt name, since their squishy bodies consist of a head that directly joins eight limbs, while the body (the mantle) is positioned behind the head. The cephalopods are an ancient class that arose well before there were land vertebrates around, but the group to which the octopus belongs is a fairly modern offshoot. We seem to have almost nothing in common with them, both anatomically and mentally. Yet they have been reported to open a pill bottle protected by a childproof cap. Since this requires the cap to be pushed down and twisted at the same time, it takes skill, intelligence, and persistence. Some public aquariums show off octopus intelligence by locking the animal in a glass jar that they close with a screw top. Like a true Houdini, the octopus takes less than a minute to grab the cover from within with its suckers and unscrew it so as to escape.
The octopus has a most remarkable nervous system that allows it to solve challenging problems, such as how to escape from a glass jar closed with a screw top.
However, when octopuses were given a transparent jar that contained a live crayfish, they failed to do anything. This greatly puzzled the scientists, because the delicacy was clearly visible and moving about. Do octopuses perhaps have trouble unscrewing a lid from the outside? It turned out to be one of those human misjudgments. Despite having excellent eyes, octopuses rarely rely on vision to catch prey. They use mainly touch and chemical information and fail to recognize prey without those cues. As soon as the jar was smeared on the outside with herring “slime,” making it taste like fish, the octopus swung into action and started manipulating it until the top came off. It quickly removed the crayfish and ate it. With further skill development, the process became routine.21
In captivity, octopuses react to us in ways that we find hard not to anthropomorphize. One octopus was fond of raw chicken eggs—each day it would accept an egg and break it to suck out its contents. One day, however, this octopus accidentally received a rotten egg. Upon noticing, it shot the egg’s smelly remains over the edge of its tank back at the surprised human from whom it had received it.22 Given how well they distinguish people, octopuses probably remember encounters like these. In a recognition test, an octopus was exposed to two different persons, one of whom consistently fed it, whereas the other mildly poked it with a bristle on a stick. Initially, the animal made no distinction, but after several days it began doing so despite the fact that both humans wore identical blue overalls. Seeing the loathsome person, the octopus would withdraw, emit jets of water with its funnel, and show a dark bar through its eyes—a color change associated with threat and irritation. It would approach the nice person, on the other hand, without making any attempt at drenching her.23
The octopus brain is the largest and most complex of all invertebrates, but the explanation of its extraordinary skills may lie elsewhere. These animals literally think outside the box. Each octopus has nearly two thousand suckers, every single one equipped with its own ganglion with half a million neurons. That amounts to a lot of neurons on top of a 65-million-neuron brain. In addition, it has a chain of ganglia along its arms. The brain connects with all these “mini brains,” which are also joined among themselves. Instead of a single central command, as in our species, the cephalopod nervous system is more like the Internet: there is extensive local control. A severed arm may crawl on its own and even pick up food. Similarly, a shrimp or small crab can be handed from one sucker to the next, as if on a conveyer belt, in the direction of the octopus’s mouth. When these animals change skin color in self-defense, the decision may come from central command, but perhaps the skin is involved as well, since cephalopod skin may detect light. It sounds rather unbelievable: an organism with seeing skin and eight independently thinking arms!24
This realization has led to a bit of hype: that the octopus is the most intelligent organism in the ocean, a sentient being that we should stop eating. We shouldn’t overlook dolphins and orcas, though, which have vastly larger brains. Even if the octopus stands out among invertebrates, its tool use is rather limited, and its reaction to a mirror is as perplexed as that of a small songbird. It remains unclear whether an octopus is smarter than most fish, but let me hasten to add that such comparisons barely make any sense. Instead of turning the study of cognition into a contest, we should avoid putting apples next to oranges. The octopus’s senses and anatomy, including its decentralized nervous system, make it unparalleled.
If superlatives of uniqueness were allowed, the octopus might be the most unique species of them all. They defy comparison with any other group, unlike our own species, which derives from a long line of land vertebrates with structurally similar body plans and brains.