Does Intelligence Depend on a Specific Type of Brain?
Editor's note: Find the full "Animal Minds" series to date here.
All life forms participate in some kind of intelligence and intentionality, in the sense that for billions of years they have sought to live and have adapted for that purpose. Nonetheless, animals that also demonstrate individual intelligence are orders of magnitude less intelligent than humans -- whether they are closely related to us physically (apes) or not (bird species).
We know their intelligence by its effects, in the same way we know gravity by its effects -- without being quite sure what it is. But we have some signposts.
Anatomy Probably Matters, But It Is Not Clear How
Even though shellfish, like octopuses, strive to stay alive, they could not open a jar to do so. Anatomy prevents it. Appendages may reward attempts at reasoning by expanding the search space for solutions. But they do not directly cause that search, any more than hands "caused" the Lascaux cave paintings. If they did, chimps would be painting caves too.
Painting? Domesticated elephants can be taught to "paint" identifiable figures with their trunks. But they are following a series of motions guided and rewarded by by their trainers. They don't know that they are painting, or how it looks to humans.
Chimpanzees have been taught to "paint" as well, but their problem is the opposite: They work readily with the materials, of their own volition, but don't attempt to represent anything, probably because their brains do not work that way.
Anatomy, it seems, can only expand search space for a purpose already envisioned by the mind. It does not expand the mind, so far as we can tell.
Tool Use May Be a Product of Definition
Use of tools is often used as a measure of intelligence, but the examples we have raises questions about what qualifies as tool use, and what it means. This becomes especially tricky when dealing with tool-use by invertebrates, or other creatures vastly different from humans in their complexity and anatomy.
Octopuses, which have very different brains from vertebrates, have been filmed carrying away halved coconut shells to use as shelters. Recently, crows were also filmed (via hidden close-up cameras) twisting sticks to make hooks to root insects out of tree bark:
Humans have previously seen the crows making the tools in artificial situations, in which scientists baited feeding sites and provided the raw tools; but researchers say the New Caledonian crows have never been filmed doing this in a completely natural setting
"Crows really hate losing their tools, and will use all sorts of tricks to keep them safe," Rutz said in a statement. "We even observed them storing tools temporarily in tree holes, the same way a human would put a treasured pen into a pen holder."
These findings are fascinating, but they also highlight the limits of assessing intelligence through tool use. First, confirming the crows' natural behavior is important, but it should not come as a surprise. Had the crows never behaved this way in nature and never been coached by humans either, it would be remarkable indeed if they tumbled to it all by themselves in captivity. Life forms of widely varying (apparent) intelligence store and hide things for later use, so that is not hard evidence of remarkable intelligence.
Brain imaging tests show that animals "treat sticks, hooks, and other tools as extensions of their bodies." If so, they probably do not abstract the concept of "tool" (that is, not-self), which limits their ability to envision other possible uses for a tool.
In any event, how we define tool use is complex, and somewhat muddled. As noted earlier, apes using stones are claimed to be entering the Stone Age. But no similar claim is made for great antshrikes, who apparently only recently started smashing snail shells using stones (the snails were a new arrival in their habitat).
Greater vasa parrots of Madagascar use pebbles for grinding minerals from seashells, though it is worth noting that many birds, including wild parrots, may eat little bits of insoluble minerals anyway, to aid in digestion. If the pebbles are tools, is the grit a tool? Are false teeth a tool? At any rate, the bird may not see any difference, and is probably not heading in any direction in particular in the use of tools.
The ability to modify tools -- often cited as evidence of additional intelligence -- prompts the same question: Does modifying a tool -- regarded as an extension of the appendage -- involve more intellectual effort than finding and marking a suitable scratching tree, as a sort of stationary comb? As you can see, even the seemingly simple task of identifying tool-use is difficult. We need much more observation of life forms in their natural habitats in order to spot larger patterns in (one hopes) a growing body of data on animal intelligence.
Sometimes, interpreting tool-use through the lens of naturalism leads to lapses in common sense. Take, for example, this section from an otherwise informative article by Annalee Newitz at I09, "The Mysterious Tool-Making Culture Shared by Crows and Humans" We are advised, "The fact that humans use tools doesn't make us unique among animals."
True, but we then hear:
Riskier environments seem to spur tool use, perhaps because food sources are more difficult to come by. And in addition, animals with large toolkits -- like humans -- seem to invent more tools as their populations grow. This could help explain why humanity's population explosion over the past century has been accompanied by an explosion in tool diversity, including radical new technologies.
Animals with large toolkits -- like humans?
If Newitz thought anything remotely similar had happened among non-human life forms, she did not mention it.
No matter how it is spun, the difference between the bent stick and the New Horizons satellite mapping Pluto is not merely one of degree. The crow is interested in rooting for grubs, and even if it develops other uses for the stick, it will never be interested in mapping Pluto. That isn't a "shared culture" at all, and we are back with the same conundrum of animal vs. human minds.
Are There Patterns in Invertebrate Brains and Intelligence?
Reptiles and fish sometimes show signs of intelligence despite having quite different brains from mammals. But, being exothermic, they don't do much of anything very often. For example, turtles may rescue each other, but can also spend months in a state of icy torpor with little adverse effect. At one time, it was assumed that the intelligence to rescue would not co-exist with lengthy inertia (the reptilian or triune brain hypothesis). Actually, the two qualities can co-exist, though they wouldn't be simultaneous.
Invertebrate just means "not a vertebrate," so there is no single type of invertebrate brain:
Invertebrates have immensely diverse nervous structures and body plans, revealing the variety of solutions evolved by animals living successfully in all kinds of niches.
And that is where things get a bit complicated. Starfish, essentially, do not have a brain or even ganglia, just a nerve ring. Their behavior has accordingly been attributed to "self-organized behavioral patterns" not strictly determined by external stimuli. It would be good to unpack what that implies.
Crayfish seem somewhere in the middle, that is, smarter than we used to think, even though the crustacean brain (a "microbrain" of three fused ganglia) is often studied on account of its comparative simplicity.
We keep learning new complexities of other invertebrate behavior too. For example, mantis shrimp use a polarizing light display to warn their fellows that a hiding place from predators is already taken.
U.S. researcher Dr. Clifton Ragsdale, from the University of Chicago, said: "The octopus appears to be utterly different from all other animals, even other molluscs, with its eight prehensile arms, its large brain and its clever problem-solving abilities."
It also has an unusually large genome, with more protein-coding genes than humans have (33,000 vs., 25, 000):
This excess results mostly from the expansion of a few specific gene families, Ragsdale says. One of the most remarkable gene groups is the protocadherins, which regulate the development of neurons and the short-range interactions between them. The octopus has 168 of these genes -- more than twice as many as mammals. This resonates with the creature's unusually large brain and the organ's even-stranger anatomy. Of the octopus's half a billion neurons -- six times the number in a mouse -- two-thirds spill out from its head through its arms, without the involvement of long-range fibres such as those in vertebrate spinal cords. The independent computing power of the arms, which can execute cognitive tasks even when dismembered, have made octopuses an object of study for neurobiologists such as Hochner and for roboticists who are collaborating on the development of soft, flexible robots.
It seems that a relatively big brain benefits even an invertebrate -- but we are now left to wonder how the octopus acquired one. Researchers consider it a striking example of convergent evolution -- with vertebrates.
What Do We Know About Insect Intelligence?
We don't know very much about insect intelligence. The envisioned long, slow continuum of intelligence from mite to man has meant that many explicitly non-human types of intelligence have been written off or explained away. Brain researcher Antoine Wystrach helps us understand how ants perceive the world:
Counter-intuitively, years of bottom-up research has revealed that ants do not integrate all this information into a unified representation of the world, a so-called cognitive map. Instead they possess different and distinct modules dedicated to different navigational tasks. ... These results demonstrate that the navigational intelligence of ants is not in an ability to build a unified representation of the world, but in the way different strategies cleverly interact to produce robust navigation.
He adds, "We need to keep in mind that this is only our current level of understanding. Even insect brains are far too complex to be fully understood in the near future. "
If the current description proves accurate, the ant may show considerable intelligence, but not have a unified sense of self, in the same way that a dog or raven probably does (all these sensations are happening to me). Other researchers are less cautious, claiming that insects may have consciousness and "could even be able to count."
But consciousness is the central conundrum in philosophy even for humans. And, as Clever Hans and similar co-operative animals have shown, the ability to count, like tool use, is not necessarily reliable evidence of intelligence. The count may be driven by metabolism, prompting, or simply the fact that a given number of efforts succeeds (without the number being abstracted in any way).
The way insect intelligence develops may be different as well. Bees, like many insects, exhibit "an incredibly wide variety of intelligent behaviors." But, according to some researchers, insect intelligence tends to increase when individuality is suppressed (the hive mind):
Compared to social species, they found solitary species had significantly larger brain parts known as the mushroom bodies, which are used for multisensory integration, associative learning and spatial memory -- the best available measure of complex cognition in these insects. The finding supports the idea that, as insect social behavior evolved, the need for such complex cognition in individuals actually decreased.
Some have described this "hive" model of intelligence as a "superorganism":
We will see that the 1.5 kilograms (3 pounds) of bees in a honeybee swarm, just like the 1.5 kilograms (3 pounds) of neurons in a human brain, achieve their collective wisdom by organizing themselves in such a way that even though each individual has limited information and limited intelligence, the group as a whole makes a first-rate collective.
If so, animal intelligences can be highly developed and yet quite different from each other. No specific type of brain is required and humans remain outliers.
But intelligence is not all we wonder about. There is also the question of subjectivity -- a sense of self. If jellyfish were conscious of their apparent intention to catch fish, would they have a mind without a brain? When starved amoebas form a slime mold, and act temporarily as a colony, do they have a hive mind, which simply dissipates when they find food and break up? Intelligence is today's unknown country. But some animal intelligences do encourage a sense of self, as anyone who has lived with a group of domestic animals will attest. Can there be a sort of minimal self?