Tony, any other problems before we start? This is the Convergent Science Network podcast.
Leading researchers in the domain of neuroscience, brain theory and technology
are interviewed by Paul Vesure and Tony Prescott.
It's Paul Vesure at Convergent Science Network podcast, together with my colleague
Tony Prescott, co-chairing the BCBT Summer School.
And today we're with Dorothy Fregese, who was our speaker, and Dorothy,
who has a cough, so we will just ignore those sounds.
So Dorothy, your talk focused on your work on tool use in monkeys, right?
So why tool use in monkeys? What makes it interesting?
Well, tool use in primates as a whole is interesting from an anthropocentric
perspective, because humans are the quintessential tool users.
We have shown tool use from the dawn of our species.
It's something that we know is culturally important and is important in the success of our species.
It's something that children show spontaneously from very early in life.
It's a very essential component of being human.
So when we see tool use in another species, we automatically are curious about
whether they are using tools in the same way we are, if they are organizing
that activity in the same way.
So that's the anthropocentric perspective.
And of course, there are other reasons to be interested in it.
You might be interested in it solely from the point of view of the biology of
the animals themselves to understand what this behavior contributes to their way of life.
And you might also be interested in it from the point of view of understanding the...
The neural substrates or the anatomical substrates that go along with the forms
of tool use that are interesting to humans.
So in non-human primates, that means being interested in the use of the forelimbs
and especially the hands.
And we see tool use in that form in non-human primates that they're using tools with their hands.
So we're interested in how that whole system is coordinated.
Okay, so then you have tool use. How now do we define tool and how do we define use?
So what makes a tool? This is a very good question, and there is no clear consensus
in the animal behavior community about this.
We recognize a tool after it has been used, and it is a tool because it has been used.
So almost anything can be a tool for some purpose. It isn't necessarily something.
It's not an intrinsic quality of the object itself.
It's imposed upon it by the actor who uses it for something.
So, for instance, I have a little box here of cardboard, and I can use this,
if I wanted to, to knock over my cup of tea. I'm not going to do that.
But then if I did, I would be using this box, cardboard box, as a tool.
Well, when it's sitting here on the table without my doing anything with it,
nobody would say that that was a tool to knock over a cup. I could use Tony's
laptop to wipe away the tea.
Yes, you could. Right, exactly. He wouldn't like that. But then,
so the point you made there, which I think was really important,
is to realize that actually there's not a real theory at this point in time of tool use.
No, there's not. There's a lot of theories about why individuals should use
tools and some ideas about what kinds of individuals are able to do this,
but there's no single theory, there is no theory of tool use.
Is there a reason to think that tool use is evidence of a certain kind of cognition?
Is that a particular reason to focus on it?
In the animal behavior community, I would say no, because we see tool use defined.
You asked me about the definition, so I'll come back to that now.
What exactly is tool use? So, as we have no theory of tool use,
tool use is defined descriptively as the phenomenon wherein an individual uses
an object to produce a spatial or force relation,
a manipulatable object, so it has to be an unattached object that the actor
controls and moves and uses to produce a change in another object or a surface.
So for instance, I can use a shovel to dig a hole.
I can use a probe to put into a small opening to push something out.
All those are examples of tool use. But there are many gray areas if you have
as broad a definition as that.
And so this is a point of continuing discussion in the animal behavior community.
In the linguistic community and in the philosophical community,
there are other treatments of what constitutes a tool.
I think Hediger has talked about what constitutes a tool.
He talks about ready-to-hand and other things that some people have discussed in terms of using tools.
But the animal behavior community mostly doesn't worry about the philosophical definitions,
and they're more concerned with the very functional definition of controlling
an object and moving it in space to achieve an outcome on a distal target,
or sometimes even on the body itself.
Well, it's interesting also given Tony's question that actually your definition
is really emphasizing the pragmatics of tool use, right?
You gave four criteria of, let's say, a functional extension to act upon an
object, detainment of goals, and that there's a force relationship.
So why do you highlight these four properties of tool use?
Why do I highlight those? Yeah, but why do you emphasize those and why do you
leave out this reasoning component that also Tony was sort of asking about?
Because I study behavior.
I want it to be observable. So those are aspects that I can measure directly or observe directly.
And I can't observe reasoning directly.
So if you would include, let's say, a neurophysiological component that might
give you a correlate of reasoning, then you would be happy to entertain it.
I'm not ruling it out, but for me, to see, for example, if I had functional
fMRIs running the whole time I was watching an individual use an object as a tool,
I might be able to say something about the neural activation that accompanies
tool use, but I'm not sure I would be able to say which aspect of that image
I'm looking at constitutes reasoning. Mm-hmm.
Okay. But is this where the animal behavior community takes a different perspective than,
say, the people in human anthropology who are looking at hominid tool use as
evidence of a progression towards later forms of human cognition?
Well, there are people in anthropology who are sort of bridging anthropology and neuroscience.
I'm thinking, for example, of Dietrich Stout, who does neuroimaging of humans
as they are napping stone, for example.
So, I'm sorry, what was the question again? Well, is there a difference in perspective
perhaps between that community and the animal behavior community?
Oh yes, yeah, there is. Because an archaeologist or an anthropologist is approaching
it from a specifically anthropocentric perspective,
their interest is in explaining the origins
of human behavior and in examining the similarities between behavior of non-human
primates and human primates in an effort to help understand the fossil record
or the archaeological record of extinct hominids and early human ancestors.
So they have a vested interest in trying to understand what features of tool
use might correspond to what sorts of evidence they find about early forms of
tool use in our ancestors.
They look, for example, at transport and selection of materials and things that
are evident in the archaeological record.
We can look at those things in behavior of extant primates as well,
and there's a community of people that are doing that. Susana Carvalho is an
example of a person who does that, and Michael Haslam, and there are others.
You are bringing to your study some theoretical frameworks, but you're suggesting
that those would be different ones. Yes.
Well, my own work is….
I would say, inspired by, not so tightly constrained by, but inspired by a couple
of different streams of reasoning coming out of psychology and movement science out of psychology.
I've been inspired by the work of the Gibsons, J.J.
And Eleanor Gibson, who jointly contributed greatly to the formation of a school
of psychology known as ecological psychology.
Psychology, and they were both extremely active in the middle and later part of the 20th century,
and by the work of Nikolai Bernstein, who was a Russian physiologist,
movement physiologist,
whose professional career was actually in the first half of the 20th century,
but whose work was translated into English in the 1960s and became very influential
in the English-speaking community after that time.
And so the Gibsons emphasized the role of the individual in actively seeking information,
using the senses to gain information and the role of perceptual learning in
the development of skill.
And they emphasized that the information that an individual needs to perform
tasks is in the environment.
It's the individual's task to discover that information and to learn to make
use of it, but not to somehow construct the information.
And Bernstein's interest was in motor skills in particular, and so this is where
it dovetails for me with an ecological perspective.
So Bernstein was very interested in how humans with multi-joint limbs and many
degrees of freedom of movement,
how a system composed of many degrees of freedom could be a.
Could be organized to achieve a specific goal and to achieve that goal effectively
and with minimal effort, even when circumstances vary.
So, for instance, if you are swinging a baseball bat and someone is pitching
the ball to you and your goal is to hit the ball,
sometimes the ball is a little faster, sometimes it's a little slower,
sometimes you have a bat that weighs a little more or a little less,
Sometimes the pitch is a little inside or a little outside,
and a skilled batter can handle all of that, whereas a novice perhaps could handle one speed,
one bat, one position, but not handle the variability.
And Bernstein was very interested in how one assembled from all the multiple
degrees of freedom in the joints
and all the variation in the physical position of the body and so forth,
how one could arrive at effective action even in the face of all these variations.
So then you focus on non-human primates and in particular capuchin monkeys, right?
So but now you were telling us that right now among the experts who count the
number of non-human primates that are around, there are about 500 species of
non-human primates. More than.
More than? Yeah. Okay, so what? The number changes, but it's somewhere around 560.
Okay. But it may be a little more by now. New species discovered all the time.
Okay, but it's of that order, yeah?
And so now of all these species we know, how many are really known to use tools
in a way that would be, let's say, accepted?
So among the old world monkeys, the Burmese macaques, Macaca fascicularis,
and then there's a subspecies name that indicates the Burmese version.
I think it's Aurea, but I'm not exactly certain of the subspecies designation. And the orangutan?
And the common chimpanzee. And the bearded capuchin uses tools routinely and habitually.
And there are some other capuchins in the same genus as the bearded capuchins,
which is now recognized as belonging to the genus Sapajou, which is a sister genus to Cebus.
It has historically, for a long time, been in the genus Cebus,
and in 2012 split into Sapajou.
So this is very recent. And there are two other species of Sipaju that have
been observed to use tools in nature, and they are both in adjacent areas to
where the libidinosis is, the bearded capuchin.
Okay, so there's two things then. That means of these 500 plus,
or let's say 600 if you round it up,
species of non-human primates, there's a handful, let's say 1%,
that are known to routinely use tools? In the wild.
In the wild. Yeah. And of those, those six, they appear to be rather strongly,
more genetically related to each other than to the rest of these species or not?
Or there's no… Well, the New World monkeys, the capuchins, are very remotely
related to the Old World primates.
The split was somewhere around 35 million years ago. ago, and then so the split
between the New World and the Old World simian primates was about at that time.
And the split among the other apes, the chimpanzees, the orangutans,
and the humans is much more recent than that, perhaps 10 million years or less.
So there's a big temporal gap in the most recent shared ancestor between the
New World monkeys and the Old World monkeys. So the important conclusion being
that- This is probably independently- Exactly, right. Evolved, yeah.
Okay, so independently evolved, but also independent of, let's say,
or it's less likely to strongly depend on a genetic program,
on genetic pre-specification, right?
Well, it would be impossible for me to specify what sort of genetic program
could result in the suite of attributes that I think support tool use. Yeah.
They're very diffuse and they're related more to foraging style.
It's not a specific action or a specific problem that they use tools to solve.
It's something about these species' approach to what they can do with objects.
So if it's convergent…,
Are we looking at a set of features that are converging?
So, for instance, are there anatomical features that appear to be convergent? I would say no.
The forms of tool use that non-human primates perform involve using their hands
to hold an object, but it's usually holding the object in a relatively common
way, in what we would call a power grip.
Grip, they're not necessarily using very fine precision to manipulate very small objects.
They're not sewing, for example.
So a power grip would be using all your fingers? Yeah, in a convergent grip.
Right. And that's sufficient.
That's all you need. If what you want to use is a stick to probe into a hole,
you don't need a precision grip. You can use a power grip, and they do.
Mm-hmm. So it isn't a point of differential dexterity.
Right. But it is, if you look what is common across these species,
it's not unique to them, but it is common to them that they are extractive foragers.
And so from an ecological perspective, an individual that is finding food in
hidden locations and has to work to open up a substrate and get at what's inside,
That individual is oriented towards the possibilities of objects that it can't see.
You have to find something behind an exterior.
So you are interested in destroying objects and getting at things.
And this way of life promotes an interest in, I would say, acting roughly with
objects, with breaking them, with banging them, with moving them around,
with being proactive towards objects.
There's a lot of handling involved. And these species all do that.
So, but we have a precision grip where we can use our opposable thumb.
Humans do, yes. Precisely gripped.
Now, how common is that in the rest of the non-human primates?
So the precision grip in the human form where the thumb rotates to face the
other digits and you have a perfect opposition possible between the tip of the
index finger and the thumb,
old-world primates can do that.
So that includes old-world monkeys and it includes apes and humans.
Humans, the morphology of the human hand is a little bit different.
Each species' hand is a little bit different from the next species.
So we achieve this grip in a human way and other species accomplish it in a
slightly different way.
For example, the thumb of apes is much smaller than the thumb of humans,
so they have to bend the index finger farther to touch the thumb, for example.
But they still achieve a perfectly useful precision grip, despite the fact that
their thumb is much shorter than ours.
All old world monkeys have the joint morphology to achieve that kind of movement
of the thumb and opposition of the of the fingers.
New world monkeys, as far as we know, only one group of new world monkeys can
achieve that kind of a precision and grip,
but we actually haven't explored very much among all the species,
so I don't want to claim that no other New World monkey does this,
but I can say that so far we know that capuchins can do it, and that's both
genera, cebus and sapaju,
and we don't know very well about other species.
But capuchins, in any case, can achieve a functional opposition,
and they place the side of the thumb against the side or the pulp of the index finger.
And it works functionally. It's not as strong a precision grip as humans achieve, but it works.
You can pick up small objects in that way.
But that would be then the only species known to do that. New world monkeys.
Exactly. Yeah. All right.
But in terms of the kinds of tool use that you see among non-human primates,
it's not that you have so many variations on that, right?
So you talked about percussive tool use.
And probing. And then there's probing and sponging, I think you mentioned.
Yeah, sometimes sponging and a few other things. scraping and using a tool as
an extension of the arm to pull something in as in.
But are there common features among these forms of tool use?
Well they are structurally simple forms of tool use.
So an object held in the hand is used to create a force relationship,
a spatial force relationship with something out in front but it's a single order
kind of relationship. It's the tool to one other thing.
So it's not the tool to something else with joints and then another thing. And it's not bimanual.
It's a relatively simple form of tool use in terms of the number of spatial
relations that have to be produced and have to be monitored and have to be produced
concurrently. So they're generally producing one.
Right. But then in terms of their, if you'd characterize tool use in these animals
in terms of their complexity, are there any patterns that emerge in that?
Well, there are different metrics for complexity. Because we have no single
theory guiding our investigation of tool use, people arrive at different metrics
that make sense for their particular purpose.
So sometimes people are interested in the sequences of actions.
Sometimes they're interested in the hierarchical organization of actions,
that the sequence has to be done in a certain order for things to work.
Sometimes people are interested in the number of tools used to achieve a single
goal. So they talk about a toolkit.
There are probably a few others that I listed in my talk that are not coming
to my mind at this moment. Well, sequence, number of actions,
hierarchical organization, selection and transport of materials.
Yeah, which we already talked about a little bit. And the number and nature
of spatial relations. And the number and nature of spatial relations.
Yeah. So if you think about those characteristics, we know that at least….
Well, we know best for capuchins and for chimpanzees that they will transport
materials, both the objects,
in this case, it's percussive tool use, and chimpanzees also for probic tool
use, that they will transport the tool to the site of use.
And they also, in the case of nut cracking, they will transport the nut to the
site of the anvil. So there is transport happening.
The details of how far they transport and how selective they are about what
they transport are being investigated empirically, and I can't give you a lot of detail.
We know that chimpanzees will transport hammerstones up to 100 meters or so,
and we know that the same is true for capuchins, although we haven't done the
careful examination of that that It has been recently carried out by Giulia
Sirianni for the chimpanzees.
So that's something we need to work on with the capuchins, I can't tell you.
But I've seen them carry tools at least 80 meters.
So, I mean, I don't think there's a big difference between the chimps and the
capuchins in that domain.
They are selective in the tools they pick up and bring.
And this is when they are far enough away from an anvil that they can't have
the anvil in view when they're doing it.
So there is some prospective selection of materials.
And that's true in capuchins and chimpanzees. Probably also true in Burmese
macaques, although that's been discovered much more recently.
And so we don't know as much about that group. Right.
But so then in the actual data you were discussing was very much derived from Capuchin monkeys.
Exactly. My own knowledge is about Capuchin monkeys. Which seem a rather extraordinary
type of monkey, I have to say.
I mean, so you were telling us they were getting fairly old,
have large brains, also have a fairly long period of, let's say,
juvenescence and long periods also of, let's say, instruction and training, right?
So what are sort of for you the properties of tool use in these capuchin monkeys
that stand out and how have you assessed those properties?
Well, when we first discovered this, first of all, we couldn't believe our good fortune.
We could hardly believe our eyes, because it's truly impressive to watch, really.
And what I was struck by immediately is that it's very skillful.
It is extremely skillful. For one thing, it is physically very strenuous.
So these are relatively small monkeys weighing two or three or four kilos in
adulthood. And of course, the juveniles are smaller.
And they're picking up stones to crack very resistant palm nuts that they place on an anvil.
So there's a nut on the anvil. And then the monkey, this little monkey,
is picking up a stone that on average weighs at least half its body weight.
It's about a kilo. It's the normal weight of an average weight of a hammerstone in our area.
And they are lifting it shoulder or head height or sometimes even over the head
and bringing it down with great force in a directed way,
in a controlled way, on this nut, which is relatively large,
but it's still a fairly small target.
So they're bringing down this very heavy stone on top of the nut,
and they don't want to have the nut roll away, and they don't want to have the
stone fall off the anvil, and they don't want to hit their toes,
and they don't want to harm their hands.
And I can tell you that when humans try to do this, we're much bigger.
We can generate a lot of force with a stone. We are actually,
when we are novices, which most of the research team is novice at cracking nuts,
we are are not good at it at all and after three
strikes our hands hurt because we're hanging
on to the stone tightly when it
strikes the nut and the rebound force hurts so after a few strikes people say
well i think i'm done now and they haven't cracked the nut so but the monkeys
have have worked out a strategy to cope with this they do it repeatedly they're
they're they're not bruising their hands,
they don't leave the anvil, you know, shaking their hands as if they hurt or something.
So they are obviously managing the production of force in a precise trajectory
and monitoring in some way,
monitoring the position of the stone and the force that should be applied to the nut.
And doing this all in a way that is not evident when you first see it,
but you know that there's something like that going on because the whole system
is so smooth and so beautiful to watch. Right.
But then in some sense, what you also showed us is these monkeys are real experts
in this because they trained for quite a while. Yes, they have.
So how does this training process exactly work?
Well, it's self-initiated and self-supported in the sense that there is an intrinsic
motivation to manipulate objects and especially to percuss objects.
Which even very young monkeys will do.
And it's part of their normal foraging, so they do it all throughout their lives as part of normal life.
But when it becomes focused on nuts and on stones, initially the young monkeys,
the very young monkeys, are working directly with the nuts.
They're not big enough to pick up stones, and they don't really have the skill
to put the nut down and pick up the stone and strike the nut.
So they're initially focusing on the
nut itself, and there's just a lot of exploration of the nut in the hands.
They're rolling it, they're knocking it, they're sweeping it around on the top
of the surface, and doing many things with the nuts. We've seen monkeys juggle
with nuts a little bit, just kind of holding them up.
I mean, we've seen monkeys take the nut and stick it in a little knot in a tree,
in and out, in and out, in and out.
I mean, anything you can do with a nut in a sort of playful,
generative way, they will do that.
Sooner or later, a monkey will do that. They don't all do all these things,
but if you sit there and watch them long enough, you see amazing combinations
of things that make no sense initially, but they're all part of play.
And then the young monkeys, when they are between one and two years old and
they're spending quite a bit of time on the ground, about a third of their time
on the ground, as do the older individuals, all the adults,
they are attracted to places where adults are cracking.
And from the cracking activity of others, there is an accumulation of artifacts,
of debris, nutshells, and the stones that were used because the stones are typically
left on the anvil. They're not carted away.
So the anvil and the stone are relatively constant features and the nutshells
are there and the nutshells don't degrade. So they're there for a long time.
So a young monkey in the vicinity of others that are cracking can see and can hear.
And it's a very dramatic activity. It's attention grabbing.
You can't just not know that your neighbor is cracking a nut.
You hear it and you see it. It's a whole body motion.
It's dramatic. So the young monkeys see and hear this activity.
They see the adults eating. They can also smell what is going on.
And they also themselves sample the bits of nuts that are still in the shells
because there are shells around.
And the adults are quite tolerant of the very young monkeys near them at the
anvil site. They allow them to be very close and watch.
And even when they're done cracking to come up and collect bits,
we call that scrounging. So there is a certain amount of scrounging.
So the young ones are, I would say, inducted. They're into the cult of nutcracking,
and they're interested in all these materials and in this place.
So they are drawn to the place that has the appropriate materials,
and they are intrinsically motivated to interact with these materials,
and it proceeds from there. Okay.
So the learning you're describing is very much sort of the infants exploring
in a context in which nutcracking is going on. It's a socially supported context.
And one of your theoretical frameworks is the Gibsonian ecological psychology
in which the notion of the affordances that an object might have for behavior is very important.
And the famous example is that a doorknob affords turning, so that rather than
necessarily focusing on the properties of the doorknob, what you learn about
it is that if you turn it, the door opens.
So is that framework useful for you in thinking about what the monkeys are learning?
It is. I don't think that they think very much about what the stone is useful
for outside of nutcracking, although they sit on them. But, you know, they're not.
Anyway, it seems to me that when they are interacting with stones initially and with nuts,
they are, certainly when they're handling nuts, they are learning about the
affordances of the nut for direct percussion, but also how it moves in their
hand and how it moves on a surface.
Right, yeah. It rolls and they eventually have to manage that feature of nuts
because when you put it on an anvil and strike it, it's going to roll or fly
off the anvil unless it's in a relatively stable position,
which they achieve by putting the nut into a pit and by placing it specifically
in a certain orientation in the pit.
So I was wondering if the young animals play with stones, and if there's some
qualitatively qualitative differences between their play behavior with stones as compared to nuts.
We don't have great data on that.
So we have seen them. They do also strike stones directly.
They strike nuts directly far more often. This makes sense to me because the
nut is actually their goal object, so to speak. The stone is...
Secondary thing. So they're more interested in the nuts than in the stones,
but they do also strike stones directly.
So the combination of the nut and the stone, I think they are assisted in learning
that from hanging around the adults.
Also, the stones that the adults use as hammer stones,
especially rather soon after they've used them,
they still have a sort of oily residue from the nut shell and if they've cracked
a nut sometimes some of the residue of the kernel of the nut is also on the
stone so they smell good they smell like nuts.
So the so the young ones both see the adults using the stone on the nut and
the stones smell like nuts and they're on the anvil or near the anvil and they're
right there with all the nut shells so there's a lot of association
of the stone with the nut cracking area and activity,
even if the young ones are not themselves able to pick up the stone and move it.
They will often, though, take the nut and strike it on the stone. This is rather common.
The little ones do quite a lot of that. They do more direct percussion of nut
onto the anvil, but they will also just simply take the nut and strike it on
the stone, which is the closest they can get to picking up the stone and striking
the nut, because they can't pick the stone up.
And then does the combination of anvil, nut, and stone come later?
It does appear later developmentally. And what you see is a young one on the
anvil with a nut, and it puts the nut down, and it strikes the nut up and down.
But one thing that's actually, I didn't have time to talk about this in my talk
today, is that in previous work by Briseida Hacende in Sao Paulo.
And she did a longitudinal study of the onset of nut cracking in a semi-free
population of monkeys, provisioned monkeys in a regenerating forest in a park
outside of Sao Paulo City.
And in that population, they crack small palm nuts, Cyagris palm nuts that are
sort of the size of an acorn.
So they can do that with a much smaller stone, and they use much less force.
So in that situation, the young monkeys that she was following,
the parallels with the monkeys that we watch in Boa Vista are perfect.
I mean, they're doing the same things. Although the smaller size of the nuts
and the smaller size of the stones gives those monkeys an advantage.
They can manage these things when they're smaller.
So they have a bit of a temporal advantage in terms of the the physical strength
they need to manage the stones.
But in that population, what she found was that the young monkeys.
The last thing to appear in the whole sequence of cracking is to put the nut
on the anvil and then release it.
So think about it. If you're an arboreal monkey and you've got something you
want, the last thing you want to do is let go of it. It's just going to fall to the ground.
So on the ground, if you release something, it stays there. It might move a
little, but it just stays there.
And they have to learn to allow the thing they're interested in to be released
and then take the stone and hit it.
And at that point, they have to switch attention from one object to another.
So you're still interested in the nut, but you have to let go of it and leave contact with it.
And then you have to pick up a stone and then hit it. So it's an integrative
attentional problem that you have to bring the stone into the,
zone of attention, if you will, while you've still got the nut there.
And this is the hardest part for the capuchins. So it's interesting that for
chimpanzees, I think it's different.
Chimpanzees don't do a lot of percussion. They do far less percussion in just
an exploratory way than capuchins do.
And for the young chimp who's learning to crack stones, for them,
the difficult The difficult part is cracking with a stone.
It's the percussion act that they're not really likely to perform.
That's the least likely part of their sequence is to pick up the stone and whack something.
For the capuchins, the least likely part of the sequence is to leave the nut
down on the anvil and take your hand off it.
So I think they have different developmental challenges in learning this sequence.
And it means that also these elements will appear later in the developmental process Right.
Differentially for the capuchin and the chimpanzees. Right. So the last thing
to appear is that you put the nut down and you let it go and you pick up the stone and hit it.
And we often see, for example, young ones will have two pieces of shell or two
nuts or something and they'll be on the anvil and they'll be hitting one and
then they pick that one up.
But then they have to hit this one and they're going back and forth like they
can't figure out which one to hit because they can't figure out which one to let go of.
But now if we focus on this learning phase, right? So what are the minimal ingredients
with which this monkey must be thrown in the world to actually start to learn this?
And the point is that if you talk about an intrinsic motivation,
okay, that's fine, but an intrinsic motivation for what?
Yeah. Right? So what are these minimal ingredients that are required?
Well, it's conjecture here. Of course. I'm designing a monkey.
So I think that what they bring to this task is an intrinsic interest in interacting
with objects and especially in percussion, which is part of their normal foraging activity.
And it's part of exploring their world to know even what to eat and how to do
it. So you mean the infant cappuccino monkey would basically grab any object
of a certain size and just cross it on? Yeah, they do.
Anything that can be banged, they try that. Leaves, twigs, anything.
So they are interested from a very young age, actually from the age at which
they have enough postural stability to take one arm and swing it forcefully.
That's when they begin to bang. as soon as they can, basically.
So that's a key ingredient, because if you don't have that initial action to
work on, you're never going to get nutcracking without at least some of that.
And capuchins have a lot of that one.
So then secondly, you have to have enough motivation to do Once you have an
instrumental goal, you have to have enough interest in,
working towards that goal for a very long time, because for them,
the learning period where they're doing this activity in various forms is years.
It's literally something like
three or four years before they can actually crack a nut very effectively.
So in this long period of time, they must generate a lot of percussion,
and they must enjoy it enough to They keep doing it.
They have to get their 10,000 hours or so.
But then combined with that, now to get back to the notion of affordance,
you also indicated that the traces of nutcracking are around them, right?
So they will see the shells, they
might see the anvil, they might see the pits and the stones and so on.
How much is that residue or these traces of nutcracking also affording the learning
process? So it's really a trigger.
Yeah. I think they're a strong support. Our data show that being around an anvil
is associated with a very large increase in manipulation of nuts.
And it doesn't have to be that way because the nuts are very portable,
especially the shells. By nut, I mean nut or nutshell in this case.
And that's very portable. So if the infants wanted to, if the juveniles wanted
to, they can pick up a piece of nutshell and they can go somewhere else with
it. They don't have to stay right by the anvil and manipulate the thing near an anvil.
And in our data, the kids are manipulating nut materials, nut shells,
nuts, at especially high rates around the anvils.
So the anvil is a place where you go when you feel like manipulating nuts, you go there.
Or if you happen to go to an anvil, then you begin to manipulate nuts.
So it's kind of a trigger for the activity.
And so the fact that these are enduring artifacts...
It certainly supports it. And this is actually not so unlike a human situation
where we have artifacts of our cultures everywhere in our homes and in our towns.
And kids encounter chairs everywhere and they encounter common tools, cups, glasses.
But in the environment in which such a population of monkeys lives,
they would then have a few anvils to which they transport the nuts.
Or they just find a nut and then find an appropriate spot where they can crack it?
Both. See, if you find a nut somewhere, you would go to the nearest anvil,
because you have to go somewhere that has a hammerstone.
So the hammerstone is the limiting resource here, not the anvil per se,
because there are many possible anvil sites.
You need a relatively flat, hard surface. You can use virtually any boulder,
or sometimes a fallen log will also serve if it has a broad surface.
But the hammerstones are rare because the predominant stone in that area is
a relatively soft sandstone, and that's unsuitable for cracking nuts.
It just breaks in your hand. If you take a big chunk of sandstone and whack
it, it just falls apart. part. So they are mainly using siltstone and ironstone and quartzite cobbles.
Quartzite cobbles are washed in from some ancient flood who knows how many eons
ago, and probably more than one.
And they're in layers in the sandstone.
And as the ridges erode, the cobbles are exposed, and they either are just exposed
in situ or eventually they fall down.
So in the transition zone between the
cliff and in the talus area where the where the
um the the boulder fields
are for where the sandstone has eroded and fallen and
where there are ephemeral streams in the rainy season there there it can rain
hard and then there are these uh channels where water comes down off the off
the cliffs and the plateaus down into the valley and um there are um uh quartzite
cobbles pebbles that accumulate there.
They're mainly small little pebbles, but there are also occasionally larger
stones, and the monkeys use the larger stones to crack the nuts.
But then do you see that in their migration patterns these monkeys would sort of consolidate.
The locations where they find these stones or they are migration patterns are
not dependent on the possibility to find such hammer stones.
Their home range is not dependent on where the anvils are, but there are many
anvils scattered around in their home range.
But the stones, the hammer stones. The hammer stones are transported to an anvil site.
Okay. So they may be transported a very short distance if there is a suitable
boulder right next to this stream and you find a hammerstone in the stream,
then you just go two or three meters and you're at the anvil.
But we also find hammerstones in very unlikely places like the top of the ridge
and somewhere off in the, you know, distant from any water source.
So they transport these stones around as well. That's what I was wondering about,
because you could imagine that in this Capuchin culture, the scarce resource is the hammerstone.
So you can imagine when they migrate that they would actually carry hammerstones along.
Well, they don't migrate. They don't migrate. Let me correct that.
They have a home range that they move around during the day,
and they cover the home range.
They travel into different parts of their home range periodically.
So, they travel a few kilometers a day, perhaps, overall, linear distance.
And they sometimes take a hammerstone with them when they leave an anvil.
But they do that, especially if there is some competition.
So if a juvenile or a subordinate adult is on an anvil with a hammerstone and
is about to be displaced by a more dominant individual,
if the individual that's got to leave is able to do so, it will take that hammerstone.
If the hammerstone is too heavy, you're just stuck, you just have to leave and
you leave your hammerstone behind.
In any case, sometimes we see individuals transporting hammerstones from one anvil to another.
And sometimes we understand a competitive reason for it and sometimes we don't know why they do it.
So we're using the word Capuchin culture here to describe what's happening.
And when we think of that in human terms, we also think of things like cultural transmission.
So something might be invented in one place, but it rapidly spreads as other
tribes copy that initial invention.
I mean, do you think that there is cultural transmission between Capuchin?
Or is it much more something that they will discover for themselves?
Or do they have to see it? Let me back up to the word culture for a moment.
Because that's a loaded word.
That's what I was thinking. I brought it up as well, right? So I'm fully responsible for some words.
I use the word tradition because it avoids some of the extra meaning that's
associated with that word from an anthropocentric perspective.
Perspective because of course there are many components that people
think are critical to culture that
in humans that are not evident in capuchins
okay could you elaborate well for example religion symbolic
systems of i don't know there are many others that that are i'm not an anthropologist
so you have to forgive me if i don't have their list but but and and anthropologists
also have a tough time agreeing on exactly what is in culture but in any case
it's a longer list than what we can say is present in the capuchins,
or chimpanzees, or any ape, except humans.
Okay. So in any case, let's talk about traditions. But the question still stands.
If this is a socially aided learning system, is it likely that this particular
behavior would be evident in a group without these social supports for learning?
That's your question? Yeah. And is it possible that this is socially transmitted?
It's absolutely possible. And I think it's absolutely the case.
And that's exactly what our data show.
That is, they don't show what happens if an individual does not have social
support, because we don't take monkeys out of their social group and watch them
grow up without partners.
But in this natural setting where we have our observational data,
so we can't assign cause and effect.
But the pattern seems to be that the young monkeys are growing up in this socially
supportive setting with all
the right materials and all the right social prompts to do these things.
And they have the time to practice over a lengthy, over years,
and this supports the development of this skill that I think is,
in the way that they perform it, has to be seen as a kind of extreme skill in
terms of the difficulty of mastering all these components.
Components there are other groups of capuchins in other
places that also display nut cracking and
i imagine they have their own components of skill
in what they're doing i i just don't happen to know them as
well okay but it would suggest the possibility of maybe a lab-based experiment
where you take a new world monkey species not known to use tools in the wild
but but you expose them to a tool
use culture and you could see maybe from observing humans cracking nuts.
Would a non-tool using new old monkey perhaps pick up that skill?
No, I can tell you they don't. We've tried that.
It's not something that monkeys learn by just observing humans.
Without deep familiarity with the materials involved and deep interest in the
outcome of the activity.
And, you know, it would have to be a sort of live-in experience.
Well, I was thinking of, you know, a sort of a Kansi-like sort of immersion
in a tool-using environment.
You know, you're surrounded by them and people are showing you all the time
and playing with you. You know, in the way that we intensely expose our children
to the kinds of objects and things that we want them to engage with as they grow older.
I don't think it would be a success. That is, in the case of capuchin monkeys,
people have kept them as pets for a long time.
You know, Native Americans have kept capuchins as pets, and they still do for
lots of reasons. Sometimes they end up in the pot after a while,
but we won't talk about that.
In any case, capuchins that are kept in human homes will sometimes begin to
use objects for things that people don't intend them to do.
And they can be trained. This is the basis for a program that you might have
heard of, Helping Hands, and there have,
been some other programs where the goal is to use a non-human primate,
a capuchin monkey In fact, as an aid for a quadriplegic person to do things that require hands,
like opening the refrigerator and taking a glass out and attaching a straw and something like that.
And so capuchins can learn to do many things with objects,
but actually for those training programs, it hasn't been shown that using a
demonstration model helps in the training at all.
They use straightforward reinforcement shaping and training.
So that means in this case, in the literature on the development of skill,
at least in humans, there's a strong distinction between an imitation-based
interpretation versus an interaction-based interpretation.
So I understand from you that if you had to choose, you would say the Capuchin
acquires the skill very much through interaction and less through imitation.
Right. Is that correct? Yeah, that's correct, except I would add the proviso by interaction.
I wouldn't include direct interaction from the more proficient individual with
the less proficient because there's no teaching or intentional showing.
It's just in the course of daily life, the kids are exposed to this over and
over and over again in a supportive setting. Okay.
And the capuchins have become specialized for tool use away from the other new
world monkeys, is what I was getting at.
Yes, that's true. Yeah. And you can see that, I guess, morphologically as well in the...
The amount of dexterity they have yeah although i wouldn't attribute that to
tool use because all capuchins have this and only some capuchins species use
tools so the the uh enhanced mobility of the thumb and and dexterity of the
fingers that we see in the capuchin monkeys um is um,
is is i think better associated with their extractive foraging style which they
are specialized in extraction as well as in tool use.
So they're really more specialized in foraging, extractive foraging, than anything else.
And other than that, they're dietary generalists, they're habitat generalists.
They're very adaptable monkeys. And tool use is one example of an unusual adaptation
of behavior that they can acquire.
So these tool-using monkeys, are you able to show that there are other cognitive
tests, perhaps, on which they do better than some other?
Is there a program to look at that? Well, first you have to realize that the
taxonomy of the genus has been shifting under our feet the last few years. Yeah.
So at the moment, most of the lab colonies that work with tufted capuchin monkeys,
work with, we always called them Cebus sapella.
Now we no longer know what they are, so we don't even know exactly what species
we have for the most part.
There has to be some further analysis to even know what species we're working with.
Okay, now what did you ask me? I'm sorry, I lost the train of thought.
Whether there would be a program to look at more broadly.
Oh, a cognitive variation across the genus? Oh, a research program, no?
What would be interesting,
I think, in the context of particularly this week when we're looking at evolution
and development was whether these are animals that have evolved tool use as
part of a cluster of increased cognitive capacity.
Or is it very much just one thing that's improved?
Yeah, I wish I could, I wish I knew. And we don't have the, nobody is pursuing
that at the moment, because what you would need is a colony of,
you would need to know what form of tufted capuchin you had,
and then you would need another species that does not use tools.
And at the moment, what's surprising is that for the past 50 years,
people have worked with tufted capuchins identified as Cebus apella,
and our lab studies on tool use have used Cebus apella.
Now that we have revised the taxonomy, Sapaju apella actually doesn't use tools
in the wild, and Sapaju libidinosis does.
So what it would be really grand to do is to have Sapaju to apella,
the proper apella, and libidinosis, because they do not live in exactly the
same places, but they border one another. And actually, they...
They just border one another. And they inhabit rather similar habitat types.
They're ecologically rather similar. Or anyway, some other species that is morphologically
quite similar to libidinosis, but is not known to use tools in the wild and
set up captive colonies of those.
And we don't have that set up yet. But Dorothy, actually, across all All primatologists
are not already implicitly running such an experiment as you mentioned this morning.
Because you say, look, if these animals acquire this skill through interaction
with the materials and their affordances, it does mean they must have a certain
creative ability and an ability of insight.
And what you were describing this morning, if you just look at the way capuchin
monkeys are kept as compared to chimps, there are some striking differences.
Differences because these capuchins seem to be very capable in escaping,
essentially. Well, chimps can too.
Yeah, I didn't say that you didn't have to lock the cage for chimps.
I said if you- And they also use tools. Yes, yeah, yeah.
But if you have capuchins in a cage with a latch that a macaque will not undo,
the capuchin will undo it unless it's really padlocked.
What I was trying to get at is that maybe the faculty we want to look at is
just the creativity to explore an action space, right?
That's not the key in this case. Would you agree with that?
Yes, although the clean experiment that was suggested, we have yet to do.
We haven't done exactly that. That would be interesting to do.
But an experiment that you have done that you described to us was this one where
the animal's required to fit an object into a mold. Right, right.
And they're not able to do that with the more complex shape.
Right, once you exceed, well, they don't do it very well with one dimension,
one feature that is just the length of the stick.
When you add a second dimension that is a cross piece, then they are,
then they really have trouble.
And they get there, but it's brute force solution. Yeah. But for example,
I have not tried myself to do that kind of experiment with, say, squirrel monkey,
which is, you know, in some ways considered a close relative to the capuchins.
So, Dorothy, to get to the finish line, two questions.
So, I mean, it's marvelous work you've been exposing to us about skill,
tool use in the wild, right, which is extremely hard to study.
So, given all this experience you have in studying behavior under these ecologically
realistic conditions, what is really Dorothy's law that we should all adhere
to in understanding behavior and the brain?
Um that's a hard one a single law of course i can't have a whole set how about a menu,
um what's the first item on your menu that that the that the experimenter should
do that the scientist we should all do it might be advice to students,
look at the animal look at the behavior look at it in slow motion and look at
it again Again, that's my advice. Okay, cool.
So Tony likes traveling, so we're going to send him to your lab four years from now.
And he's going to check a prediction you're going to share with us today.
So what's the key specific prediction that you would like to commit yourself
to today in this domain of tool use in non-human primates?
I predict that young monkeys who are faced with a challenge of handling a novel stone,
that the trajectory for becoming expert at using a stone like that,
the ease of learning to handle this novel stone,
that there will be a developmental trajectory for that.
That the skill of handling stones develops slowly over time with a lot of practice,
and I'm not there to measure all the practice, so I'm just sampling at time points.
But I predict we're going to
see that it's not a very complicated prediction in the end. I don't know.
That's not a great prediction for you. It's not a theory-driven prediction at all.
He might be disappointed for you, Shona. We're going to see.
Yeah, if you gave me another five minutes, I might think of another prediction.
Dorothea Fergesi, thank you very much for this conversation. You're welcome.
Kind of a wimpy prediction, sorry. The CSN Podcast was produced by the Convergent
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