For many years, we’ve been trying to understand why the octopus is uniquely smart among cephalopods. Research answers some questions only to raise others, as a recent controversy shows.
A 2018 study (open access) sought to discover why octopuses are unusually intelligent—and this year another study disputed the findings. The issue is thorny because octopuses obey none of the rules for animal intelligence. Intelligent animals are supposed to be social animals that live a long time. That makes sense; managing relationships requires some intelligence and brains take a long time to mature. As Ed Yong notes in The Atlantic, apes, elephants, whales, and dolphins, crows and other corvids, and parrots (all vertebrates) share these traits. But the intelligent octopus shares the physical traits of the “dim-witted dynasty” of snails, slugs, clams, oysters, and mussels that are its own relatives. And it breaks the behavior rules for other smart life:
With rare exceptions, most of them [octopuses] are solitary animals that aren’t above cannibalizing one another when they meet. Even those that swim in groups, like some squid, don’t form the kinds of deep social bonds that chimps or dolphins do. Cephalopods also tend to live fast and die young. Most have life spans shorter than two years, and many die after their first bout of sex and reproduction.Ed Yong, “For Smart Animals, Octopuses Are Very Weird” at The Atlantic
Piero Amodio and colleagues’ 2018 paper builds on the history that the first cephalopods modified their shells 530 million years ago by filling them with gas. Gas enabled buoyancy so that they could walk and then swim on the ocean floor. But 275 million years ago, for unclear reasons, octopuses lost their shells. Squid and cuttlefish absorbed their shells as inner slabs. As Yong tells it,
Unencumbered by a shell, cephalopods became flexible in both body and mind, according to Amodio and his colleagues. They could move faster, expand into new habitats, insinuate their arms into crevices in search of prey. “This allowed them to feed on many more kinds of food, requiring more complex foraging techniques,” Amodio says. “We think this is one of the key challenges that pushed them to become smarter.”Ed Yong, “For Smart Animals, Octopuses Are Very Weird” at The Atlantic
They were also much more vulnerable: “Almost every major group of predators eats cephalopods, including dolphins, seals, fish, seabirds, and even other cephalopods,” he reports. Intelligence can, however, help a life form create new defense strategies. The nautilus offers a suggestive contrast:
It’s telling that the nautilus—the only living cephalopod that still has an external shell—bucks all of these trends. It lives for up to 20 years, reproducing several times during its life. It also has a much smaller brain than its shell-less relatives, and doesn’t seem to be anywhere as smart. The loss of the shell “has been linked to so many of the adaptations that make cephalopods special,” Amodio says.Ed Yong, “For Smart Animals, Octopuses Are Very Weird” at The Atlantic
The problem with this hypothesis, says critic Ernesto Mollo in the opposing 2019 paper, is that a shell-less octopus must avoid getting eaten while it is still developing the intelligence to think of a strategy. So the intelligence must have preceded the loss of the shell. Amodio concedes the difficulty, pointing out that even nautiluses, though less smart than octopuses, are still smarter than clams. Thus, he agrees, more or less, that there was a preceding journey that featured shelled intelligence. He hopes that researchers can continue by comparing the intelligence of different species of octopus to see if a general pattern prevails.
One difficulty is that just how a life form comes to evolve “intelligence” is a difficult question. Being intelligent ourselves, we can easily see the advantages of intelligence. But seeing that provides no information about how exactly intelligence is acquired. Not only are there no good theories of human consciousness, but there are also no good theories about how even an octopus comes to be smarter than we might have expected. And that problem underlies the disagreement between the two groups of researchers. Further research might unearth a wealth of interesting information without shedding much light on that conundrum.
One difficulty is that the interpretation of research into animal intelligence is sometimes guided by outdated assumptions. For example, a recent study confirmed that cats can recognize their names. But reports confounded the cat’s ability to recognize his name as a signal (an easy feat for a cat) with his ability to recognize an abstraction (too far out of his depth to be worth exploring).
Also, leaving humans and our abstractions aside, there is no “tree of intelligence,”, in the sense that, say, all mammals would be on a higher rung than all cephalopods. Intelligence is much less evenly distributed than such an image suggests. For example, crows can be as smart as apes and dogs may not be as intelligent as seals, despite dogs’ close connections with humans. Even lizards can be smart if they need to be, though they are handicapped by a metabolism that rides with the ambient temperature (exothermic). Octopuses, as we see, are unusually smart—and they are not even vertebrates. It’s not clear what drives intelligence in general so each case of unusual intelligence must be considered separately.
Also, we need to be clear how we define intelligence. Life forms are “purpose-driven” by nature, in the sense that they seek to remain alive. Even bacteria are purpose-driven. In pursuit of bread crumbs, an amoeba colony is definitely smarter than your computer. So is a fruit fly. In fact, AI experts are trying to develop AI that is as smart as an animal. Seeking to thrive and grow, even plants communicate extensively, without the need for a mind or a brain.
But in the absence of any apparent consciousness or sense of self, most of us would probably not describe a life form’s communications with other life forms as “intelligent” in the sense that we might think of a chimpanzee or a dog as intelligent. We mean that some of the chimpanzee’s or the dog’s mental processes remind us of our own.
See also: Is the octopus a “second genesis of intelligence”? Can its strange powers provide insights for robotics or the human mind?