In the animal kingdom, intelligence has evolved in many different ways, in many different
creatures.
We often think of our fellow primates at the top of the intelligence list, with their ability
to use tools like sticks and rocks to access food and their ability to recognize themselves
in the mirror.
Orcas too are among the most intelligent, with their unique language skills and orchestrated
hunting techniques.
And anyone with a dog is constantly surprised at complex feats of social intelligence and
emotional sensitivity.
Intelligence seems to thrive in animals like this - mammals - often carnivorous ones - that
live in tight social groups.
But if we survey the world of animals, one of the smartest is one that is perhaps unexpected
- an animal that isn’t a mammal at all, but a bird - crows, or more generally - corvids.
Corvids are mischievous, playful, and extremely intelligent.
They use tools to forage and to solve complex problems - they even drop nuts on a road for
cars to crack, and then pick them up with the safety of pedestrian lights.
They can also recognize faces and can hold a grudge against someone who was rude to them
for several years.
They can mimic sounds that they hear, and scientists have found that their problem-solving
skills rival that of a 7-year-old human.
How is it that corvids like crows are so profoundly intelligent, and how is it that we even measure
their intelligence in the first place?
Is bird intelligence wired in the same way as mammal intelligence, or is it something
different all together?
The corvid family is also known as the crow family, and includes includes jays, ravens,
rooks, and magpies.
The level of intelligence varies between the species, but scientists have found that the
New Caledonian crow is the most intelligent.
They’re to corvids what we are to the rest of the primates
There have been many experiments performed on these crows that show just how intelligent
they are.
In 2014, the crows were presented with various tubes filled with water with a treat floating
on top, which they couldn’t quite reach.
In one trial, when presented with a treat inside a tube of water and a treat sitting
on top of sand, the crows knew to drop rocks into the water-filled tube to raise the water
level to reach the treat, and ignored the tube with sand.
In the next trial, when presented with a single tube of water, and objects with various densities,
the crows knew to select the sinking objects rather than the floating ones to reach the
treat.
When presented with two tubes of differing water levels, the crows knew to drop objects
into the tube with the higher water level to reach the treat faster.
These trials demonstrated the crows’ abilities in both problem solving and tool use.
And the authors believe that their skill level at deciphering and completing these tasks
is similar to 5 to 7-year-old children.
However, in two more challenging tasks, the crows didn’t perform as well.
One required understanding the difference in a wide tube versus a narrow tube.
And another was a counter-intuitive task where the tube with the reward was connected to
another tube via a hidden u-bend.
The crows didn’t fully grasp these setups.
But in comparison, during tests with human children, only kids around 8 years old were
able to consistently solve such tests.
And in addition to using tools, New Caledonian crows can build tools.
And not just simple ones, but ones with multiple parts.
When given objects that were too short to retrieve food from a puzzle box, the crows
combined elements by inserting one stick into the hollowed opening of another to make a
tool long enough to reach the food.
One crow even made 3 and 4-part tools.
Compound tool construction like this has only been observed outside of humans in a few captive
great apes.
It is usually only associated with human intelligence.
And in addition to this, we now think crows might be better than we ever could have imagined
at making plans for the future.
The ability to take actions now that will give a benefit later is not something that
most animals are good at.
Delayed gratification and planning are high-order skills.
Even human children can’t do this, and neither can many of the adults I know.
It requires our memory of the past and foresight for future events.
Can crows, of all animals, really possess this ability?
In a study published in 2020 , New Caledonian crows were first shown one of three puzzle
boxes that they already knew how to open–each requiring a specific tool.
They were then removed from the test area for 5 minutes before being presented with
5 different objects: 1 tool for each of the boxes, and 2 distraction objects.
After selecting an object and waiting 10 minutes, they were allowed back into the test area.
The researchers discovered that not only did the birds choose the correct tool that would
open the corresponding puzzle box, but they would remember to bring the tool with them
into the test area.
In another study, researchers presented the birds with a locked box with a treat in a
similar manner.
But this time, the birds were then presented with an assortment of items including the
correct tool, a few distracter tools, and an immediate food reward - but one that was
less appealing than the one in the locked box.
And most of the time, the birds took the risk and delayed their gratification, kept the
correct tool, and later opened the box with the better treat.
This might seem easy, but it isn’t.
Only once human children reach 5 years old does this ability arise, and even then, it
doesn’t in all of them.
For some, it takes a few more years.
These mental skills certainly set crows apart from other animals, with their actions and
abilities more in line with the smartest of the primates.
How does this bird give the most intelligent primates a run for their money?
Why does a bird need to be this smart?
Even though crows may have a similar intelligence to many primates, bird brains and primate
brains are not at all the same.
Birds and mammals split on the evolutionary tree 320 million years ago.
And since then, their brains have become quite distinct from one another, making scientists
question exactly why corvids are so smart.
In vertebrates, the pallium is the grey and white matter that covers the brain.
Before the evolutionary split, both birds and mammals evolved a large pallium.
But, after their lineages split, the mammal pallium evolved into a layered structure known
as the cerebral cortex.
This is the most complex structure of the mammalian brain.
Each layer contains nerve fibers running horizontally and vertically that process and transmit information.
Here is where many important functions take place, including learning, memory, sensory
perception, and conceptual thinking.
Birds don’t have a cerebral cortex.
But a study published in 2020 found that the fibers and circuitry in the bird pallium are
organized very similarly to a mammalian neocortex - with fibers running both horizontally and
vertically.
The authors believe this explains where bird intelligence comes from.
Another reason why birds were initially thought to be incapable of this level of intelligence
was due to the small size of their brains.
But, its not the absolute size of an animal’s brain that matters, but the brain-to-body
ratio.
Crows tend to have big brains compared to their body size.
In mammals, the bigger-brained are humans and dolphins; in birds, it’s parrots and
crows.
However, as scientists’ understanding of the brain grew, they discovered it wasn’t
just size that mattered, or even brain size relative to body size.
A big proponent of an animal’s intelligence is the density of neurons.
This is because having tightly packed neurons leads to better communication between them.
And it turns out that certain bird species have very densely packed neurons.
In a 2016 study, researchers measured the number of neurons in various bird and primate
species.
They found that some birds, like corvids, have twice as many neurons as primates with
similar-sized brains, with numbers closer to that of larger primates.
While these findings tell us how crows are so smart, the question remains as to why.
Plenty of bird species thrive with fewer neurons and weaker mental abilities, so why did crows
evolve this way?
One theory is that it has to do with how they are raised.
Unlike other species, corvids spend more time with their parents.
New Caledonian crows, for example, are fed by their parents for up to two years.
During this time, they have ample access to role models who are making and using tools
and have the opportunity to use these tools themselves.This extended parenting time allows
skills to be transmitted vertically, meaning, from parent to offspring.
The family groups of many species of crow can be very tight, with young crows even helping
to defend their parent’s new nest of babies.
However, beyond tight family groups, adults of many species of corvids don’t lead particularly
social lives.
New Caledonian crows mate for life, but otherwise, don’t really interact with other adults.
Other species of corvid will often forage and roost in large groups, or work together
to mob a predator - but there isn’t a social hierarchy, or complex social bonds in these
settings.
This goes against one leading theory of intelligence, called the social intelligence hypothesis.
Chimpanzees, for instance, live in large and complex social groups, where they have to
interact with others outside their immediate family and keep tabs on many relationships.
It’s a constant game of politics.
Dogs, wolves, and even orcas, have to deal with a great amount of social complexity.
And this “social intelligence” needs a lot of brain power.
If adults of many of the smartest corvids don’t live in complex social groups, why
would a similar intelligence have evolved?
Adult corvids may rarely live in wide social groups, but often, juveniles do.
Before pairing up with a mating partner, during their ‘teenage’ years, some species of
corvids live in larger flocks - aptly called juvenile gangs.
And these gangs work exactly like it sounds - a bunch of teenagers hang out and bully
each other and fight.
In these angsty years, corvids, like ravens for example, form the many relationships that
they have to keep tabs on.
Here, there is a social hierarchy, with some individuals who rank more highly and get access
to better food, and some that are lower-ranking and submissive.
And, intriguingly, corvids may need social intelligence to interact with other species.
Outside of Yellowstone National park, certain ravens have been seen interacting with wolves
- especially wolf pups.
The animals can be seen to play tug-of-war, and the ravens teasing and enticing the puppies
to jump and grab sticks.
Sometimes, the ravens will even pull the wolves' tails.
By all accounts, it looks like the animals are playing.
Some scientists think that individual ravens may even develop special bonds with individual
wolves within a pack.
This relationship-building may help the ravens more readily scavenge the wolve’s kills.
This propensity to interact with other species has some groups wondering how we may be able
to cooperate with corvids.
One idea is to train crows and other corvids to pick up cigarette butts or garbage.
A few different companies are developing devices that will autonomously train them, giving
the birds a treat once they place the trash into the device.
A theme park in France has already been undertaking a similar operation.
They trained six rooks to pick up trash, four days a week, under the supervision of the
park’s falconer.
While it may seem like we’re taking advantage of these birds and their intelligence by having
them do something we should already be doing ourselves, those involved claim to have purer
intentions.
It helps the environment, teaches humans to cooperate with other species, and teaches
the public about these intelligent creatures.
By studying other intelligent species and what made them that way, scientists have gained
a better understanding of the brain and its development.
And for all we know, we could be overlooking other small-brained species that could harbor
a higher intelligence - other animals that can help us unlock the many of the secrets
of the brain.
I love talking about animal intelligence on this channel, because I love the way the brain
works.
I love its mysteries and its unbelievable power.
And because of this I love the feeling of learning - of grasping new concepts, of those
moments of sudden understanding washing over you, when physics and math and chemistry and
biology start to click together, feeling like one beautiful interconnected machine that
explains our universe.
I’d like to think crows feel this too when they get their treat out of the tube.
To engage myself in STEM learning, I use Brilliant.
Brilliant is an amazing tool for learning STEM interactively.
The quizzes, puzzles, and downright delightful animations make the learning engaging, where
it almost feels like a game.
And if you get stuck on a particular question, Brilliant doesn’t penalize you or impede
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one, so you can learn from your mistakes.
Its easy to learn in this low pressure environment, and most importantly its easy to learn by
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There are so many courses to dive into, from neural networks to algorithms, to logic and
probability, or my new favorite, scientific thinking.
Nature is a puzzle, and in this course you get to learn about principles of physics and
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To get started for free, visit to brilliant.org/realscience or click on the link in the description, and
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And if you’re looking for something else to watch right now, you can watch our previous
video about the jellyfish that lives forever - or watch Real Engineering’s latest video
about the way engineering solved the mystery of the Concord crash.