Crows
are among the planet's most intelligent animals, teaching their young
to use tools for foraging and banding together to fight off intruders.
Now, the first study of how abstract reasoning works in these birds'
brains could shed light on how intelligence works in a truly alien,
non-mammal brain.
We've
studied brain structure pretty extensively in mammals from humans and
apes to whales and mice. But German neuroscientists Lena Veit and
Andreas Nieder are the first to watch what happens in crow brains as
these birds worked their way through a series of brain-teasers. They
actually wired the crows' brains up with electrodes, watching as
individual neurons fired when the crows did a test that required
abstract reasoning. What Veit and Nieder found reveals a lot about what
intelligence looks like in a brain that's nothing like our own.
The Evolution of Intelligence
The
crow, and some of its relatives in the corvid family (such as jays and
magpies), are among the only intelligent species we've encountered
outside the world of mammals. But their brains are utterly different
from ours. The mammalian seat of reason is in our prefrontal cortex, a
thin layer of nerve-riddled tissue on the outside of the front region of
our brains. Birds have no prefrontal cortex (PFC). Instead, they have
the nidopallium caudolaterale (NCL), which is located toward the middle
of their brains. You can see the different regions in the image, below.
The
thing that's really interesting about comparing bird and human
intelligence is that we did not evolve from a common, intelligent
ancestor. Our last common ancestor with birds lived during the Permian
period, about 300 million years ago, before the age of dinosaurs. It
probably looked like a cross between a reptile and a rodent, and was
roughly the size of a big raccoon.
This
ancestor's simple brain was ruled by instinct rather than higher-level
cognition. Still, lurking inside its rather small skull was a brain part
called the pallium, which over millions of years evolved into the PFC
in mammals and the NCL in birds. That makes mammal and bird intelligence
an excellent example of
parallel evolution — both groups of animals developed intelligence independently of one another.
Despite all their differences, the PFC and NCL have a few features in common. Veit and Nieder
write in Nature Communications that
both regions are involved in "working memory, reversal learning and
reward prediction." The areas also "share important properties such as
dense innervation by dopaminergic fibres and connectivity patterns with
multiple sensory input, limbic and motor output regions." What that
means is that the NCL and PFC are both packed with neurons, or nerve
cells, that respond to the crucial neurotransmitter dopamine. Its
neurons are also connected to the parts of the brain that handle memory,
emotion, and body movements. The PFC and NCL are brain command centers,
synthesizing information from a vast array of inputs and outputs.
Testing Crows' Ability to Reason
Given
that the NCL is the seat of crow intelligence, the researchers decided
to see whether they could actually watch in real time as a crow figured
out a puzzle. They used crows that had been raised in captivity, and
trained to do a test kind of like the Sesame Street "which one doesn't belong?" quiz. The crows had to identify whether two images were different or the same.
First,
the researchers put electrodes over the crows' NCL, to watch each
neuron firing. Then they would present the crow with an image. Next, the
crow would be prompted to choose an image that matched or didn't match
that image (they had already been trained to do this with a sound or
sign that either meant "match" or "don't match"). Finally, the crow
would be presented with two images and have to choose the matching or
not matching one.
This
is a test that requires abstract reasoning, because the images change
all the time and the crows have to apply the abstract idea of "match" or
"not match" to a variety of inputs. In addition, this test reveals that
the researchers defined intelligence as an ability to do abstract
reasoning. Obviously there are many ways to define intelligence, and
this is simply one way to do it.
What
the researchers found was pretty amazing. They identified what they
call "abstract rule neurons" which governed which answer the crows would
give. Basically, the birds' brains assigned one rule (match) to one
neuron, then the other rule (don't match) to another neurons. When the
crows correctly matched an image, the match rule neuron would fire. When
the crow gave an incorrect answer, or became confused, the abstract
rule neuron fired only very weakly.
Veit
and Nieder concluded that this was strong evidence that crows' brains
have developed to handle abstract rules, which is why the birds are good
at learning and responding to a variety of situations in a flexible
way. They note that "the ability to guide behavior by general rules
rather than by relying on fixed stimulus-response associations
constitutes a survival advantage." This is the same survival advantage
conferred on humans due to our intelligence. But our intelligence
occupies a very different structure in our brains.
Alien Intelligence on Earth
What
this experiment suggests is that two dramatically different species
might have similar abstract reasoning abilities — even if their brains
are completely unlike each other. If we imagine that intelligence can
only dwell in a mammal-like brain, we may miss out on discovering smart
life forms elsewhere. The crow brain may be the first truly alien
intelligence we'll be able to study
The
crow brain may also help us better understand what's required to build
an artificial intelligence, too. We can look at what the crow and human
brain share in common, and speculate about what it might take to create
an intelligence that resides in a non-brain structure. As I mentioned
earlier, both the PFC and NCL contain many neurons connected to other
parts of the brain, and they work a lot with the neurotransmitter
dopamine. These regions also appear to deal in abstract rules.
Most
of all, we can find hope in the idea that intelligence isn't just a
quirk of one type of brain. Many kinds of brains can become intelligent.
We are not alone.
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