Transcriber: Denise RQ Reviewer: Patrizia C Romeo Tomasini
Thank you very much.
I thought I'd start today just by introducing myself
and explaining a little bit more
about how I came to have the quite unusual job
that I am now lucky enough to have.
So, as David alluded to,
I started life as a psychologist interested in the human mind.
And I've ended up chasing chimpanzees around the jungles of Africa.
So, how have I made this transition?
Well, after I had done my degree in psychology,
I was offered a PhD to study chimpanzee communication.
And when I was offered it, I thought:
"Why not? What an amazing adventure!"
Unfortunately, my enthusiasm for the choice
wasn't shared by all members of my family;
grandma, notably, when hearing the news, said:
"Hey, love, why on earth do you want to go and do that?
I can't think of anything worse!"
(Laughter)
And grandma remains a skeptic to this day
of why I have such a fascination with chimpanzees.
But for me it's been one of the best choices I've ever made,
and it enabled me to become an evolutionary psychologist.
This means I'm interested in
how the human mind has evolved through time.
So I'm interested in questions like:
What makes the human mind special compared to other animals?
Is it our culture? Is it our memory?
What about our language?
Our language particularly interests me.
And I really would love to know and understand more:
How did language evolve?
So now you know the kind of questions I'm interested in.
How can studying chimps actually help me to answer these?
Here, I've illustrated how we are related
to some of the members of the primate family.
What I am interested in is really tracing back
through our ancient past
and trying to understand what were our mental capacities like
millions and millions of years ago.
And by doing this, we can try and understand how things have changed
to result in the modern human mind that we see today.
So by studying other animals that are very closely related to us,
what we can try and do is actually reconstruct
the now-extinct common ancestors that we shared with those creatures.
And so the logic is, that if we take a mental ability
that we know humans have got - say, self-recognition -
we know that bonobos and chimpanzees can also do that.
So we make the inference, or the estimate,
that our last common ancestor was also capable of that ability.
And so, by comparing human abilities
to those of our closest living relatives, the chimpanzees and bonobos,
we can try and map out
which of our mental abilities are actually really ancient,
with their roots right back in our primate lineage,
and which are actually probably evolved
since we split off from the rest of the primate lineage,
and are really the things that make our minds unique,
the things that make us special as humans.
That's the logic of why I study chimpanzees,
and I've particularly tried to apply this comparative approach
to try and understand how we evolved language.
Human language is the most complex communication system
that we know of in the natural world.
So, what do we need
in order to communicate with language?
Well, first of all, we have to have the motivation or the intention
to communicate with others.
Our words have to have meaning.
When I say "bottle," you know that I am referring to this object here.
And I don't just say my words in any old order.
My language is highly structured and rule-governed.
So take the simple sentence "Lucy kicks the horse,"
and you may get an image like this in your head.
Take exactly the same words, but put them in a different structure,
and you get a very, very different meaning.
So, we know that language is incredibly complex
and we have all of these abilities and more,
that enable us to communicate in this very complicated way.
But to try and understand its evolution,
one way to go about this is to actually say:
"Well, let's take each of these elements
that we know we need for language,
and with each of these elements, ask,
"Which of these are uniquely human?
Or to what extent, actually, might they be older and shared?"
And therefore, maybe we'll be able to find something similar
in chimpanzee communication.
So when it comes to chimpanzees,
what do they communicate about?
Chimpanzees are incredibly social creatures.
They live in a very complex social environment,
so many of their vocalizations help them to navigate
those social interactions.
So when a subordinate individual greets a dominant,
he pant-grunts (Vocalizes) as he greets him.
When chimpanzees fight, they scream -
they scream to try and recruit others to come and help them in the fight.
But chimpanzees also communicate about their surrounding environment.
One really important aspect of that is food.
So whether that's bananas in the case of captivity,
or figs in the case of wild,
chimpanzees produce a range of different calls
when they're feeding.
So to let you hear what that sounds like,
I've got a recording from the wild.
This is Michelle,
she has just started to feed on this lovely fig tree
and this is the kind of noises that she makes.
(Audio: chimpanzee sounds)
OK, so, when I first heard this and started to observe it,
I thought, what is it that Michelle is communicating
to the other chimpanzees in her group?
Is she telling them simply that there's food here?
Or is she telling them something more specific?
Could she be telling them about the quality
of the food that she has found?
Or, even more specific,
maybe it's actually the type of food that she has discovered.
When I was observing this,
my thought was: well, maybe these calls are actually acting
in a similar way that my words are.
Maybe they really are referring to very specific things
in their external world.
In order to test this,
the first step was to establish
whether the chimpanzees give different calls
for different types or qualities or quantities of food.
Now, I started to try and address this in the wild, but unfortunately,
it's really difficult to assess things like the quantity of food
available in the wild,
and this video will show you why.
So this is Marnie and he's eating figs.
Each one of these yellow balls is a fig.
I just want you to estimate how many figs are in this tree.
As the camera pans out,
you'll see that there's another two chimps feeding above him.
OK, so I hope you appreciate the level of challenge that I faced there.
I thought, OK, to get a handle on what they might be communicating about
is really hard in the wild,
so for this study, I'll come back to captivity.
And so, in captivity I started with just trying to assess:
what do the chimpanzees think of the food quality that they receive?
I started just by objectively giving them a choice.
I threw in a bucket of oranges with a bucket of apples,
a bucket of apples with a bucket of bananas.
And I simply recorded which food they picked first.
And I did this all-possible pair-wise comparisons
of two different types of food,
until I could establish with some degree of certainty
that there were foods that the chimpanzees really valued.
We ended up with three really high-preference foods,
three medium-preference foods,
and three low-preference foods.
And then I went about recording the kind of sounds
that the chimpanzees gave when they encountered these foods.
So when they found food that they really loved,
that was high value --
(Audio: chimp voices)
the chimpanzees would give that kind of call,
similar to what you heard Michelle doing when she was eating the figs.
This is a visualization of the sound.
You can see, we've got time running along here,
frequency running up here.
You can see that these calls are quite long
and they have also quite a lot of energy in these higher frequencies.
As their preference for the food decreases,
the calls get lower in frequency and they get shorter.
(Audio: short, low-frequency chimp calls)
And that's the same chimp responding to a low-value food,
in that case, apples.
It's a very graded system, so the medium-preference [calls]
are somewhat in-between those two.
I recorded all these sounds,
and I then went about measuring them very precisely,
and we found that, yes, the callers really do seem
to be using this variation in their calling system,
systematically.
So the high-preference foods get these ah-ah-ah calls,
the low-preference ones get these ha-ha-ha ones.
But I thought, well, as a human I can do more than just tell someone,
"This is great food," or "This is not very nice food."
I can tell them, "I'm eating apples, grapes, bananas."
Are the chimps capable of being more specific?
For this, we looked to see if for the food in the low-preference category,
if they labeled the types of food differently.
But we found that apples, greens and carrots
got exactly the same kind of calls.
Same thing at the medium-preference level,
so, grapes, plums and chow, again, got very, very similar calls.
But at the high-preference end - I have to say, much to our surprise -
we found the chimps gave distinct calls
to mangoes, breads and bananas.
And we tracked these calls over different days
and again, they seemed very consistent,
so it really did seem that in this particular captive setting,
the callers are not only capable of labeling the value of the food source,
but also the actual, specific food types.
So this was a level of specificity that we really hadn't expected to find.
So that was great.
But it's never enough in communication to just look at the production.
Because maybe as scientists -- I've gone about and measured these calls,
and maybe I've picked up on some regularities
that the other chimps don't really understand.
For this to be proper communication about the food,
the listening chimps have to understand what these calls are referring to.
So we went about trying to ask:
Are these calls meaningful labels
to the ones who are listening to them?
For this we had to do what's called a playback experiment.
So I'm just going to walk you through how we went about testing this.
We had a very simple design.
We simply wanted to know: Can the chimpanzees distinguish
between low-value grunts given to apples,
the "ha-ha-ha" ones,
or the high-value grunts given to bread,
the "ah-ah-ah" ones?
So, again I conducted this study at Edinburgh Zoo,
and this is a plan of the old enclosure.
The zoo has since built the chimps an amazing six-million pound enclosure,
which is absolutely fantastic for them,
but this is the outdoor enclosure of the old facility.
It had a concrete gully running along this wall,
and the chimps couldn't see into that gully
until they came really up on top of it.
So it basically gave me two places
where I could hide food for them.
What we did is we established, over a number of weeks, two trees,
and these trees fruited regularly.
The bread tree produced tubes full of bread
and the apple tree produced tubes full of apples.
We also had a few rules.
To stop the chimps just sitting here,
waiting for the bread tree to produce its wonderful fruit,
we had the contingency that,
although both trees fruited their tubes together,
only one set of tubes was actually full.
So in reality, it meant we threw in bread tubes and empty tubes,
or apple tubes and empty tubes.
This also got the chimps into the habit
that they really had to get down and actually look through all the tubes
to find which location has actually got food in it.
We did this for a number of weeks,
until we were happy that the chimps had learned
that this is where apples appear, and this is where bread appears.
So then we were ready to test their understanding.
We popped a speaker equidistant between the two the trees,
so we never gave them a cue as to which the correct tree was,
based on the speaker position.
Then I asked the keepers to get all the chimpanzees inside,
so they couldn't see what I was doing.
Whilst they weren't looking,
I snuck empty tubes under both trees.
This is really important - we never rewarded them
for any behavior on a test trial,
because I was interested in what they can naturally understand
with these calls,
not what I could train them to associate with these calls.
Then we'd wait for the first individual to come out,
and then we would play him back a group member's call
given to either apples or bread,
and then saw where he went to search for food.
At the beginning of the study,
I had great plans to test maybe eight, nine
of the eleven available chimps -
I knew not of all of them would want to play my game.
But Liberius had other plans for me.
This is six-year-old Liberius, the youngest member of the group,
and he just loved this game!
He thought the tubes were brilliant.
So he made it his mission to always - without fail, almost -
be the first one out.
Whenever they went inside,
he'd always rush out to see: "Oh, I wonder if that weird woman has put
those things under those trees again?
So in the end, we had to admit defeat
and we had to just focus on Liberius.
The results I'll show you are from Liberius only,
which obviously is a bit of a weakness,
but I'm pleased to tell you that I went to Leipzig in Germany,
and the German chimps do the same thing.
So I'm now happy that this is no longer an exceptional chimp.
So what did Liberius do?
When he heard [bread] grunts,
he went and searched for longer
and searched more tubes under the bread tree
than he did under the apple tree.
And when he heard apple grunts, he did exactly the opposite -
he then went and spent longer
searching under the apple tree than he did under the bread tree.
By looking at his behavior,
we were able to deduce that he must understand the content
or the information in those calls.
So, what does this tell us?
Let's go back to the big picture
about the evolution of our own linguistic abilities.
We now know that this ability to refer to things
in the external world with our sounds,
we know that humans can do it - we do it all the time.
This showed us chimpanzees can also do it.
And after this work, we also know that bonobos can do this.
So we've got pretty strong evidence now
that our last common ancestor six million years ago
was probably also capable of this kind of communication.
And this work sits nicely with older work
that's shown that quite a number of species of monkey
can also communicate in this way.
So rather than just this last common ancestor
from about six million years ago being capable of this,
this probably represents a really ancient ability
that our last common ancestor with the old-world monkeys,
maybe 30 million years ago, might have been capable of.
So that's kind of a whistle-stop tour around some of the studies I've done.
But is the story I've told you so far really that simple?
When humans use these referential words like "apple," "bottle,"
we do it intentionally,
to tell each other about the external world.
When a chimp does the same thing, gives the "ha-ha-ha" calls to apples,
is he doing it to share information with other group members?
Or is he just excited?
Can he control this vocalization?
Maybe it's just an automatic response
he can't really control when he sees apples,
and other chimpanzees have learned to interpret that
as a meaningful signal.
So this is something I'm now looking at in the wild.
We're trying to run experiments in the wild to really try and test:
Why are the chimps making these calls?
What motivates them?
What are their intentions?
And work in the wild is fantastic; I'm incredibly lucky to do it.
But as you can see from the myriad of different creatures we encounter,
it's a huge adventure - fantastic, but also a real challenge
to get the science done.
Thank you very much for your time.
(Applause)