All language subtitles for nova.s44e27.bird.brain.480p.hdtv.x264.rmteam

Birds, one of nature's most
amazing success stories.

There are thousands
of different species,

found everywhere on earth.

They're beautiful...

inspiring...

and mysterious.

But could they be smart?

People commonly think of birds
as small-brained

and not worth looking at.

But in the last couple of years,

our view of bird minds
has been revolutionized.

Scientists are putting birds
to the test.

Can they solve problems?

Can they cooperate?

Are we friends again?

Do they feel emotion?

New research shows
just how clever they can be.

Every day with these birds
is interesting and different.

It's always fun
and exciting and new.

And perhaps they're more like us

than we could have
ever imagined.

We're starting to realize

that the simplest explanation

may be that they're seeing
the world in much the same way

that we do.

Exploring the "Bird Brain"

right now on "NOVA."

It's picnic time at a small zoo
in the English countryside,

and visitors are about to meet
a very special parrot.

His name is Rio,

and after three I want you to
shout "Rio" as loud as you can.

One, two, three.

Rio!

Rio is a ten-year old
scarlet macaw

from the South American
rain forest

who's been trained
as an entertainer.

Can you show everybody
your wings?

Come on then, Rio.

There we go.

Rio will fly on cue.

Give him a big round
of applause... well, done, Rio,

lovely flying today.

And he's a talented gymnast.

- Yeah, he's showing off today.
- Really Rio, definitely.

But today he's going
to try something

that's not in his repertoire
of show tricks.

It's called a string pull test.

Rio's favorite food... a peanut...
Is dangling on a string.

He'll have to pull the string up
to get the peanut.

Rio has not been trained
to do this.

In fact, he's never seen
this puzzle before.

And it isn't a skill
a parrot normally needs.

If you're a parrot in the wild,
you probably

will never come across a treat
dangling from a piece of string.

So it had to figure out
what to do.

That implies these birds
have the ability

to visualize a puzzle...

To visualize a physical action,

and then to foresee the
consequences of that action.

Rio can see the string,
and the peanut he wants.

At first, he's not interested.

But after a few minutes...
And a little encouragement...

He figures out what to do.

And once he's figured it out,

he can repeat it
without trial and error.

When a bird pulls a string
and secures food in that way,

it demonstrates a level
of insight into the problem.

It has worked out the mechanics
and the process beforehand.

And that's not something
we used to think

birds really did much of.

For many decades,
scientists thought

that most of a bird's behavior
was ruled by instinct.

In the 1930s, the Austrian
zoologist Konrad Lorenz

conducted some of the earliest
studies on the lives of birds.

Working with geese,

he saw that they learn
from the moment they're born.

It's called imprinting...

They follow the actions
of the first thing they see...

Which is usually their mother.

But Lorenz showed that even this
most basic instinctive behavior

can be learned in a new way.

These geese imprinted on him.

The significance

of the imprinting experiment
was it showed that

there were behaviors
such as following

that the behavior itself
is instinctive.

But the cue, what do you follow,
that's learned.

Lorenz spent years trying
to tease out the difference

between instinct
and intelligent behavior.

In one set of observations,
he discovered that

a goose sitting on a nest
reacts immediately

if an egg rolls away, she brings
it back to the clutch.

It looks like
an intelligent action.

But if the egg is removed, she
still continues the movement.

Her brain is responding
instinctively

to a simple trigger.

Even when the egg
is replaced with a cube,

she brings it back
into the nest.

When the bird continues
the motion

even after the egg is gone,
that implies

that the behavior
is more or less instinctive.

The bird isn't consciously
thinking through

the consequences of its actions.

Even what looks like an
incredibly complicated skill...

Flying... Requires
very little thought.

There are many aspects of flying
that are controlled

without ever sending signals
to the brain.

And they're controlled
right by feedback

from the feathers
to the spinal cord,

and control how the wings
are then moved to change flight,

without thinking about it
at all.

Huge groups of birds
can fill the sky

with beautiful and coordinated
patterns of flight.

This spectacle seems
like it would require

high levels of intelligence,

but it's mainly instinctive.

So is everything a bird does
ruled by instinct?

Or do they have what
we would consider intelligence?

Meet Bran...
A hand-reared young raven...

And his owner,
bird trainer Lloyd Buck.

Well, this is Bran,
and he's a three-year-old raven.

We've had him
since he was about ten days old,

so he's what you call

"complete social imprint"
on humans,

but he's particularly bonded
with me.

We share a very, very
close bond.

To keep Bran busy,
Lloyd will sometimes

give him a problem to solve.

Here's one he tried
a few months ago,

in Bran's aviary,
where there's a birdbath.

A piece of food is trapped
inside a plastic bottle

that's been crushed.

First, Bran adds water.

That alone doesn't free
the food,

so he swishes it around
so that liquid carries the food

out of the bottle top.

That's my boy!

Good boy!

Lloyd didn't teach Bran
how to solve this problem.

He just gave him the challenge

and let him figure it out
on his own.

So, we've presented him
with that problem,

and through his own intelligence
and problem-solving abilities,

he worked out
to use his own water,

what he had around him,
to his advantage,

which I think shows
a lot of intelligence.

Ravens like Bran
and parrots like Rio

belong to two families of birds
that are widely considered

to be among
the smartest species.

Ravens are part
of the crow family.

Crows live almost everywhere
on earth,

with an average lifespan
of ten to 15 years.

They have a starring role
in many classic myths

as cunning animals
who bring bad luck.

Parrots, on the other hand,
have been loved

as pets by humans
for thousands of years.

They also thrive
in many different environments,

and they can live
to be 80 years old.

Their long life span gives them
plenty of opportunity

to learn new things,

and that may be one reason
why they seem so smart.

At the Haidlhof Research Station
near Vienna,

scientists are studying
the intelligence

of many kinds
of crows and parrots.

What makes our center unique
is the fact that we have

multiple bird species here
at the same time,

and it is very interesting
to compare them.

They're working with
a type of parrot

called a kea, from New Zealand.

This is John,
and he'll be trying

a much harder string-pull test.

First, peanut butter
is hidden in a small tube

and tied to the end of a string.

Right away this is
a more complex challenge,

because the treat
is out of sight,

instead of hanging
right in front of him.

To complicate things further,
now there are two strings,

but the second one
just has a stick on the end.

John goes straight
to the correct string

where the reward hangs
directly below him.

Next, the two strings
are crossed.

So now the reward is no longer
directly below the attachment

to the right string.

And John has to decide
which string to pull.

When the string
is anchored here,

and the reward is here,
and a string is anchored here,

and the reward is here,
the position of the reward

is actually opposite to where
the bird might expect it to be.

So it implies an additional
layer of processing.

John immediately pulls
the right string.

Most of the kea parrots who try
this puzzle need some practice,

but even with the rewards
and strings swapped around,

they learn to pull the right one
most of the time.

If they pull a string that is
offset from the food,

this really implies
that they have a plan.

And that's a real key,

they're able to plan this out
mentally, work out the steps,

and employ it correctly
when they see the task.

Compared to other birds,

parrots and crows
have large brains

in relation to their body size,
and scientists believe

that may be one reason
why they can work out

solutions to problems they don't
encounter in the wild.

Most bird brains are small.

But they have one critical area

in common with humans
and other animals

with higher intelligence.

The executive center of the
bird's brain is right here.

And that's the part
that really allows them

to make plans and strategies

and organize ideas to use
to act upon things

that will happen in the future.

Birds brains may be tiny,

but for their size they seem
to contain more brain cells...

Or neurons...
Than many other animals.

The number of neurons is a
better indication of brain power

than the physical size
of the brain.

And this is an interesting thing
we've learned recently

that bird brains actually pack
a lot more neurons

into a particular area
than do mammal brains.

So even though they're
physically very small in size,

they have a lot of punch
in that size.

The intelligence of parrots
like kea

is also thought to be influenced
by where they come from.

In their natural habitat,

the highest mountains
of New Zealand, food is scarce.

Sometimes kea parrots can strip
berries from shrubs and bushes.

Other times they have to search
for insects.

They only find enough to eat
by being adaptable.

And that has an impact
on their brains.

Anything that involves
innovation

and trying new techniques

and having to solve problems

within the environment
to get food,

that all stimulates
a greater connection

of the neurons in one's brain.

So they're basically
building a strong brain

by having to explore

this complex and variable
environment.

Their explorations make
kea parrots inquisitive...

And fearless.

And they're fascinating
to watch.

Because they evolved
on New Zealand,

where they had few predators,

these birds don't seem
afraid of anything.

Until humans arrived,

there was little
to threaten them.

They could explore whatever
they wanted...

And still do.

This is very different
from the other super-brains

of the bird world.

Ravens and the rest
of the crow family

live alongside big predators.

Like kea parrots,

they must find food
wherever they can...

Even if they have to steal it.

But wolves and coyotes
are dangerous,

so crows and ravens
have to be cautious.

Crows are famous for being
afraid of new things

that they encounter
in their environment.

And most animals are.

It's a good strategy.
It keeps you out of trouble.

It pays to be wary.

But crows are famously wary.

Compared to parrots,

ravens and the rest of the crows
have a very different approach

to solving problems.

Auguste von Bayern
works with New Caledonian crows,

considered to be one of the most
intelligent bird species.

This is Wek.

She's wearing a collar because
she recently lost her mate.

Come on.

Crows mate for life,

and Wek started pulling out her
feathers when her partner died.

She's been raised by humans
since infancy.

Wek was hand-raised
and that's why she has

a very close relationship
with humans.

In all tests she's participated
in she was one of the best birds

and, yeah, she seems to be
clever

and enjoys to work
in our experiments.

This experiment is designed to
compare how New Caledonian crows

and kea solve problems.

Wek represents the crows,

and for the kea parrots,
this is Kermit.

A peanut.

Their challenge is called
a multi-access box.

As the name suggests,

the bird is presented
with a problem...

Food in the center of a
box, so out of reach.

And the special thing is that
it can be accessed

in four different ways.

So there are four different
solutions to get the food

out of that box.

The birds can pull the string
to get the peanut out

through the hole,

drop a ball down a chute
to dislodge it,

prod the nut with a stick,

or open the door
and reach inside.

This is a new approach
because usually animals

are just tested with one problem

and there's just one way
of getting the food,

and it's very interesting
to see how species differ

in the way they approach
a problem

and the way they explore
that box.

The first time both birds
see the puzzle

they make the same choice...

They just pull the string.

Then the researchers
take that solution away,

to see what they'll do next.

Wek uses the stick
to poke the nut free,

but this isn't a surprise.

New Caledonian crows
are very special

because they're the only
crow species that use tools

in the wild.

They obtain a lot of their diet
by using tools.

Kea parrots don't use tools
in the wild.

But Kermit figures out
a solution

with the ball and chute.

Again, the researchers remove
the option that's been used...

For Wek, the hole for the stick
is taped over.

Wek has to try something else...

so she tries the ball and chute.

With two choices left,
Kermit just opens the door,

reaches inside
and takes the peanut.

But Wek won't take
this approach.

The last thing a crow
wants to ever do

is stick its head in something.

They're extremely vulnerable
if they do that.

And to stick their head
inside that box,

it could trap them in it.

Wek still opens the door,

but rather than put her head
inside,

she pokes the nut free
with a stick.

Kermit's last option
is the stick.

His curved beak makes it
very hard to hold,

but he still sees this
as a potential solution.

Even though it's not easy.

Both birds found four different
solutions to the puzzle,

showing they're able to think
flexibly.

The ability to think flexibly

is certainly a hallmark of
a cognitively advanced animal.

So rather than having
this set response

to a stimulus every time,
as Lorenz worked upon,

now you've got
a whole battery of responses

that could be put into play.

And now it's a mental task
to sort among which ones

are best for a given situation.

A bird's environment can
encourage flexible thinking.

Like humans, birds seem to learn
new things by playing.

The great thing about keas

is that they are very playful
and curious.

They are not only interested
in new things,

but are also quite daring.

They have a notorious urge
to explore everything they see

and they want to play and
explore the physical effects

and consequences
of their actions.

Researchers noticed
that kea parrots

often try to put one object
inside another.

So they give them
a related challenge...

A selection of tubes
fixed to the floor.

The younger birds
are fascinated,

trying to put the toys
into the tubes.

There's no food reward,
just curiosity.

And they seem to get better
at learning which toys

fit which tubes.

Can they take this new knowledge

and apply it
in a different situation?

A peanut stuck in a tube
is a new problem to solve.

The younger birds
approach it first.

This one studies the problem
from all angles.

She picks up a block, but seems
to know that it's too big.

She then selects the one block
that fits the tube.

Only the birds that played
with the tubes and toys

can solve this on their own.

The ability to learn skills
in one context,

then transfer them
to another context,

is another thing that allows
researchers to infer

that this is a conscious process
going on.

That these are not just
instinctive behaviors,

that they're learning
new things,

and that they're able
to transfer this knowledge.

This is a similar challenge.

The reward is in plain sight,

but the tube is too long,
and the food can't be reached.

The catch can be released
by dropping a stone onto it.

To do that, Wek is going
to have to figure out

how the catch works.

The researchers replace the
long tube with a shorter one.

Now Wek can reach the catch,

and she quickly learns
how to open it with her beak.

When the crow experiences
the short tube,

they can release the food

through their normal process,
peck on something.

That's what crows typically do,

is bite or peck or probe
with their beaks.

So they learn the relationship...
To get food,

that lever needs to be tripped.

But once she's learned
how the catch works,

can she figure out
how to release it

when she can't use her beak?

Wek realizes that
she can release the catch

by dropping the stone on it.

And using a stone to get food
in this way

is not something a crow
would normally do in the wild.

The fact that the crow
is able to take a stone

and move the same object
that that bird

had previously moved
with its bill,

implies that the crow
is thinking ahead

and visualizing the action
that dropping the stone

will result in the same movement
that its bill did.

Using an unfamiliar tool to get
food is a demanding mental task,

even for New Caledonian crows.

At the Max Planck Institute
in Germany,

the researcher sets up a puzzle
to see if a crow can understand

how to get a reward
by pulling on a hook.

Two hooks are covered
by a plastic sheet.

Only one of them contains a
small white container with food.

This crow seems to get it
right away.

But was it a lucky guess?

Or was she using knowledge

that comes from her
natural environment?

New Caledonian crows
are the only species of bird

that's been observed to use
hook tools in the wild.

They use the stems
of pandanus plants

to make kind of like
jigsaw-bladed fish hook

sorts of tools.

They'll shove that down a hole
and a grub will either

grab onto it, or they'll
actually skewer the grub.

They make hooks that turn
to the left or to the right.

They use them appropriately.

What's interesting here
is that it seems

like they are able
to bring this skill

that they use in the wild
normally into a lab setting

that's completely unlike
the environment

that they normally use it in.

To a hook that isn't one
that they've made themselves,

that in fact looks nothing like
the hooks they make themselves.

But is still hook-shaped.

And they clearly understand

the repercussions
of that hook shape.

Crows are not only good
at solving problems,

they're also good at negotiating
complex sets of relationships,

because they live
in large groups.

Many scientists believe that
forming social relationships

within big groups

helps drive the intelligence
of animals

like chimps and dolphins.

Can this also be true for birds?

Living in a social group
is hard.

You have to remember alliances.

You have to remember
friendships.

And so there's a hypothesis,

the social intelligence
hypothesis,

that proposes that
the selective pressures

of living in these groups,

of having to meet
all these challenges,

has favored the evolution
of a brain

that can do more complex
cognitive processing.

But what happens
in birds' social groups?

Do they learn from each other?

Valerie Dufour
used to study great apes.

Now she applies some of the same
methods to studying rooks,

who are members
of the crow family.

She watches how they interact
with each other

and analyzes the results.

Valerie found a social network
as complex as those seen

in groups of monkeys
and other primates,

with a clear structure
and close friendships.

But how does this
social structure

relate to intelligence?

Valerie puts a group of rooks to
a test she's used with primates.

This box is... a little set up
that's created to see

whether birds can learn
from watching each other, okay?

So there's two ways
to open that box.

You can either pull
on the little rope there.

And in that case,

just lift the ball
and they can pick up the reward

that's in there.

Or, you can just simply

push on that box
and in that case,

you just need to put the beak
through and pick up the reward.

One bird is trained
to pull the ball,

and half the rooks
are allowed to watch.

When this group
tries the puzzle,

they all do the same thing,
and pull the ball.

Meanwhile, the other half
are watching a bird

trained to use the other
solution... to push the ball.

And when these birds
try the puzzle,

they repeat what they saw...
They push the ball.

This suggests these rooks
learned how to solve the puzzle

by watching another bird.

This is called social learning,

and it's considered
very high-level thinking.

It's certainly more advanced
than an imprinted behavior.

It's also much more advanced
than a behavior that you learn

by individual trial and error.

In this case, you're having to
watch others perform a behavior,

and then replicate that.

It's new and it's exciting

because it's something
we've known in other species

like in primates, for example.

Nobody would have guessed
about the rooks or the crows

or the ravens.

Nobody would have been able
to say, "Yes, I expect them

to be able to do that";
we had no idea.

Social learning in crows
and parrots could be a result

of their larger brains.

But what about birds
with smaller brains...

Like geese?

In the same place that
Konrad Lorenz studied his geese,

Isabella Schieber
of the University of Vienna

is exploring whether
there's more to the goose mind

than basic instinct.

Geese live in
a clear social hierarchy.

And this experiment
tests whether

their natural pecking order
helps them figure out

other relationships.

Isabella arranges
seven cards in a row

and assigns a value
to each one...

Blue being the highest,
and black the lowest.

The geese don't see
the complete row,

they only see one pair
at a time.

In the experiment, green
is higher than yellow,

so under the green
card is a treat

and the goose learns this pair.

But yellow is higher
than purple,

so on the next round, the reward
is under the yellow card.

Now he's been taught that green
is higher than yellow,

and that yellow, in turn,
is higher than purple.

Next, purple is higher
than red...

So now purple has the treat,

and so on down the row.

Once the geese have learned the
relative value of all the cards,

the next stage is to see
if they can apply this knowledge

to a harder challenge.

They're shown an entirely new
set of pairs,

with no food rewards.

Over and over, the geese choose
the higher value card,

even though they never saw
the entire row all at one time.

The ability to rank objects

in a hierarchy is, it's a form
of reasoning called inference,

transitive inference.

And it was formerly thought
that only apes

and very sophisticated animals
could do this.

So knowing that card A
is greater than card B,

and that card B
is greater than card C,

you might be able to infer
A is greater than C.

Well, and these birds
obviously did that.

It's clear that geese,

despite their small brains,
understand hierarchies.

And in their social groups,
they also seem to cooperate.

When they fly in formation,
they appear to work together,

whether it's intentional or not.

When geese fly in formation,
they gain aerodynamic benefits,

by riding the vortex of air
off of each other's wingtips.

There's a bit of extra lift
there that they gain.

So they do switch positions
as they're flying,

and get some assist
from the other individuals.

So can birds actually cooperate
to solve problems?

Like geese, kea parrots
live in social groups

with complex relationships.

This experiment tests
whether they can work together

as a group.

No one bird can lift the lid
off the food box by itself.

But if one bird sits
on the other end of the see-saw,

the lid rises
and the rest get to feed.

After a while, this kea
parrot hops off the seat,

and another takes its place.

Eventually,
each bird gets to eat.

That's a clear demonstration
of cooperation,

where some individuals
are up there opening the lid,

and others are feeding.

And then they switch off.

I think it shows they're all
working to the same goal.

They get to eat.

They're using the social group

to attain
their individual goals here.

This feat of cooperation
suggests that these birds

may be communicating
with each other in some way.

But can a bird communicate
with a human?

Jackdaws are members
of the crow family

with a pair
of very unusual eyes.

Jackdaw eyes
are quite conspicuous.

They are light on the outside

and dark in the middle,

so they are rather similar
to our own eyes.

So we were interested in testing
how responsive jackdaws were

to communicative eye signals.

This test was designed
for a jackdaw named Dhuli.

Food is hidden
under one of two cups.

Then Auguste gives Dhuli
a very subtle clue...

She just looks
at the correct cup.

Dhuli has to read Auguste's
eye movements

in order to choose
the right cup.

The gaze experiments
are interesting

on several dimensions.

One, they show that a bird
is very attentive

to the gaze of another animal,
another species.

In this case,
that it's bonded with the human.

Dhuli understands
that Auguste's eye signals

are directing her to the cup
with food under it.

She's able to grasp
this form of communication.

But she also seems to be
demonstrating

another cognitive ability.

She appears to know
there's food under the cup

even though she can't see it.

This is called
object permanency.

Object permanency is a concept

that humans develop when they're
three or four years old.

They can understand that
a hidden object is still there.

And so for birds to be able
to demonstrate this

has been profound, and,
again, suggests to us

that these birds
have those abilities

that a young human would too.

But some tests are really hard...
Even for young humans.

Like this one
involving chocolates.

These children
are given one chocolate

and their mothers explain
that they can either

eat that chocolate now,
or not eat it,

wait for five minutes and be
rewarded with two chocolates.

Understanding a trade-off
and planning for the future

is a kind of reasoning

that doesn't develop in children

until they're
three or four years old.

So it's very hard
for them to wait.

For those that try to wait,
five minutes is a long time

with a chocolate
right in front of them.

They try ignoring it.

Or distracting themselves.

Or even bending the rules.

Don't eat the chocolate.

At last, the time is
up, two chocolates.

I... watch what I can do.

Being able to delay
gratification...

Trade something now for
something better in the future...

Is a key developmental milestone
in children.

But can a raven
do something similar?

This is Rumo.

He likes bread,
but he prefers cheese.

Can he learn to wait
for the treat he likes better?

It's called
a delayed exchange test.

The exchange is a little bit
complicated

because it involves
two main difficulties.

First, you have something
in your possession,

so you possess something.

It might be valuable,

so obviously you want
to keep it.

And you have to accept
to lose it

to get something better
in return,

and you have to wait
a little bit.

And that's very difficult.

First, Rumo is taught
that he can trade his bread

for some cheese.

But then, he has to wait.

Sometimes Rumo drops the bread,

perhaps as a way
to make waiting easier.

And the more Rumo
likes a particular food,

the longer he will wait.

Sometimes he'll go
for several minutes

before he exchanges bread
for cheese.

But if the food on offer
is one he doesn't like...

Like a grape... he won't wait.

He just eats the bread.

Mastering a delayed exchange
had been documented in chimps,

but never before in crows.

The ability of these animals to
wait up to five or six minutes

implies a couple of things.

One, they're making a tradeoff,

a very sophisticated
calculation.

"I'm going to get
something better if I wait

this amount of time."

And that's a difficult
mental process.

It clearly shows
they're planning ahead,

because they're calculating
that tradeoff.

Another way many birds
plan ahead

is that when they have
more food than they can eat,

they hide it
and return to it later.

Rumo does the same...
As do most crows.

Many crows and many jays...

Which are also members
of the crow family...

Hide food.

And they come back to it later.

It's called caching.

And it's a really complicated
behavior,

and it's really challenging,

because they have to remember
the locations

of dozens or hundreds of spots
where they've hidden food.

And they might even
have to remember

things like whether another
individual was watching them

when they hid it,

and whether another individual
might steal it.

Ravens will also hide things
that they can't eat... like toys.

So can they learn
if a person watching them

is likely to steal
their treasure?

Two researchers watch the ravens
hide their toys.

And the ravens know
they're being watched.

One of the researchers
goes into the aviary,

in full view of the raven.

She approaches the hiding place.

She looks at the toy,
but leaves it where it is.

The second researcher
goes into the aviary,

but she is a thief.

The next time
the ravens are given food,

they're watched
by the honest researcher,

and they hide the food
in plain view.

But when the thief watches them,

the ravens hide their food

in a part of the aviary
out of her sight.

I think, in their brain,
they are learning

the association between
one individual

and a benign task, let's say,

they don't bother the cache.
They don't take it.

And with another individual,
they're learning

that this is
a dangerous individual.

It takes things of mine.

John Marzluff has done
his own experiments

to see if crows can recognize

the face of a person
who's a threat.

He and his team at the
University of Washington

went undercover
to test the birds' reactions

to being caught and tagged.

When we first captured birds
we were wearing this mask.

So the birds that were immobile
under a net

saw this person coming to them,
grabbing them,

stretching out their wings
to measure them,

applying rings to their legs
to identify them,

and then letting them go.

Crows don't like being caught,
even when they're unharmed.

So the question was
would they remember

that the masked man
was a threat?

A few days
after the initial tagging,

Marzluff walked across
the campus again.

He kept the mask on,
but he left the crows alone,

to see if he'd get any response.

It was very striking.

The first time
after we did this experiment,

and we walked
with the caveman mask,

the birds immediately
responded to that.

They scolded with harsh calls

that are indicative
of a predator.

And they gathered around us.

They attracted others in.

And they would even
dive down at us.

Marzluff discovered
that the crows

were somehow telling each other

that the person in the
caveman mask was dangerous.

And what's more amazing,
even though the team

never again caught crows
with the mask on,

that reaction has been
passed down

through several generations.

It's been 11 years
since we caught seven birds

on our campus with this mask.

And nearly half of all the birds
we encounter on a given day

respond strongly to that face.

Even though they weren't even
born at the time

we first did our capture.

The only experience they have
with that caveman is hearsay.

Now, Marzluff is studying
another remarkable behavior.

It's called a crow funeral.

His team puts a decoy
that looks like a dead crow

on the sidewalk,

and within just a few minutes,

the trees are filled
with screeching crows.

Marzluff showed the crows
a similar decoy in the lab

and brain scans reveal

that they're activating
their memory centers.

But are these memories
also linked to emotion?

I think birds do feel emotion.

Maybe not exactly like we do.

But they've got
the parts of the brain

that cause us to feel calm
or anxious or fearful.

And those feelings in us

are motivated by chemicals
that are released in the brain.

And birds have those
same chemicals.

So I think it would be unusual
if they don't.

Emotion in birds
is being studied

by scientists around the world.

In one example, researchers
noticed that a distressed raven

appears to be comforted
by a close friend.

This raises the possibility

that ravens might understand
what other ravens are feeling.

This is called theory of mind,

and it might be
the next frontier

in understanding
how birds think.

Theory of mind is the hypothesis
that animals are capable

of mentally putting themselves

in the perspective
of other animals.

Humans can do this.

We empathize with each other.

Can birds do this?

Do birds have theory of mind?

It's hard to know whether birds
feel emotions

in the same way that people do,

because we can't ask them
how they're feeling.

But we know that birds
get upset.

We know that they're happy.

And so the simplest explanation
is that their emotions

are probably quite similar
to ours.

Lloyd Buck would agree
with that.

When Lloyd's been away
for a few days,

Bran is excited to see him back.

Then he gets angry with Lloyd.

Yes, you're cross, aren't you,
because I left you?

I left you, eh?

You haven't seen me
for two days, have you?

You haven't seen me
for two days and you're angry.

But eventually Bran
takes hold of Lloyd's finger

and won't let go.

We've made up now,
we're friends again, eh?

We're friends again.

This can sometimes go on
for an hour before Bran lets go.

You've been a good boy.

Finally, Lloyd is forgiven.

Calming down now, yeah?

Yes?

Scientists once believed

that birds were driven
by pure instinct.

Now it's clear
that at least some species

are not only intelligent,

but may be emotional too.

Just how much their
minds resemble our own

is the next question to explore.

You can explain
a lot of animals' actions

through instinctive behaviors

that don't require
a lot of conscious thinking.

But now it's become harder
and harder

to ignore the evidence
that birds

are capable of solving problems,

of making friendships,
of learning,

of putting themselves

into the experiences
of other animals.

And I think we're starting
to realize

that the simplest explanation
may not be

that they're automatons.

The simplest explanation may be
that they're seeing the world

in much the same way that we do.

This "NOVA" program
is available on DVD.

To order, visit shopPBS.org
or call 1-800-PLAY-PBS.

"NOVA" is also available
for download on iTunes.