Crows are really smart birds. Most people have probably heard this by now, but their intelligence continues to surprise researchers. A new study adds still more evidence for the problem-solving skills of these birds.

First, a little background on crows – they are members of the Corvidae family of birds, which includes crows, ravens, rooks, jackdaws, jays, magpies, treepies, choughs, and nutcrackers. This entire family of birds exhibit relative smarts, but crows and jays in particular have demonstrated surprising intelligence. Crows are one of the few animals to pass the mirror test – to recognize themselves in a mirror (actually this study was done on Eurasian magpies – in one study crows failed the mirror test), they can fashion and use tools, they have incredible memories, and exhibit impressive problem-solving skills.

The new study looked specifically at Caledonian crows. The researchers set up a “vending machine” that can be operating by putting a piece of paper of a certain size into a slot, which would then release a single treat. The crows quickly learned how to use the vending machine to get food. But that wasn’t the new bit – the new bit was that they then gave the crows paper, but not the right size for the vending machine. They also had no reference for how big to make the paper, they only had their memory of prior use.

The question for the researchers was – could the crows fashion the paper into the right size and shape for the vending machine purely from memory? They did, without any problem. The reason the researchers thought they could was because these crows already exhibit tool-making ability. They fashion hooks out of stems and use them for poke grubs or fish for food. They do this apparently from memory. Baby crows have also apparently learned this ability from their parents, which indicates the existence of a tool-making culture among these crows.

Crow Brains

What is most interesting is the implications of this research in terms of understanding animal intelligence and intelligence in general. We tend to use human intelligence as the generic example of “intelligence” but in fact there are many evolutionary paths that intelligence can take.

Crows have relatively large brains for their body size, compared to other animals. Their “encephalization quotient” is about equal to chimpanzees. The EQ is a ratio of brain to body size but adjusted for size, because there isn’t a linear relationship. Crows have an EQ of 4.1, chimps 4.2, humans 8.1. But that is not the whole story.

We can also look at neuronal density – the number of neurons per gram of brain. Birds in general have a high neuronal density – higher than primates. So they pack more processing power into their small brains. Some researchers have tried to come up with a more complete measure of processing power. They consider several variables: “the number of cortical neurons, neuron packing density, interneuronal distance and axonal conduction velocity.” Corvids score high on this measure as well, with humans scoring the highest.

Since corvids are flying birds, there is extreme evolutionary pressure to keep their weight down. Therefore, if there is simultaneous pressure to get more intelligent, it makes sense that they would pack in neurons more tightly, rather than just growing bigger brains (like humans did). They couldn’t fly around with a giant head.

In any case, the relatively large and powerful brains of corvidae matches their observed behavioral intelligence. But there is yet one more feature to consider – the organization of the brain. One of the reasons scientists were initially surprised at how intelligent corvidae are is the fact that they lack the frontal cortex seen in primates and especially humans. This is the part of the brain mostly associated with problem solving, understanding the self (hence the mirror test), and mental flexibility.

So, researchers suspect that crows simply evolved a different brain structure to carry out the same types of processing, and the evidence we have so far suggests this is true. Researchers looking at activity in the brains of crows during problem-solving tasks found activity in the nidopallium caudolaterale (NCL). It seems likely that this part of the crow brain evolved the circuitry necessary to carry out the flexible problem solving behaviors that crows display.

This, then, is an example of convergent evolution. Corvids and primates developed different parts of their brains to undertake flexible adaptive behaviors. Crows are intelligent, but with different brain anatomy than primates.

It’s fascinating to think where this might lead. If they are allowed to evolve for another 100 million years or so, is it possible for corvids to evolve into a technological species? What would that be like?

There are other species that also display high neuronal density paired with impressive problem-solving. Racoons, for example, are also really smart. It’s easy to imagine them evolving into a technological species.

And of course the same is true of most primates. What’s interesting, however, is that only one tiny evolutionary branch, and one surviving species, actually did evolve technological, civilization-building intelligence. This probably indicates that even if many of the traits are there, the probability is still low. A lot of things have to come together, not just cleverness.

And of course it is also fascinating to speculate about what an entirely alien intelligence might be like. The only reasonable supposition, in my opinion, is that they would be more different from human intelligence than we can imagine. Aliens in science fiction are mostly (there are some exceptions) impossibly human – not just anatomically, but intellectually. An entirely independent evolutionary path, even with convergent evolution solving similar problems in similar ways, would still likely result in an intelligence that would be vastly different from our own in surprising and enlightening ways.

Corvid intelligence is perhaps a tiny window into what we might expect when we eventually do encounter alien intelligence – meaning something very different.