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- [Narrator] We are the paradoxical ape.
Bipedal, naked, large brained,
long the master of fire, tools, and language,
but still trying to understand ourselves.
Aware that death is inevitable,
yet filled with optimism.
We grow up slowly.
We hand down knowledge.
We empathize and deceive.
We shape the future from our
shared understanding of the past.
Carta brings together experts from diverse disciplines
to exchange insights on who we are and how we got here.
An exploration made possible by the generosity
of humans like you.
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- It is such an honor to be here
among all of these brilliant speakers
so thank you so much for having me.
Human beings occupy two worlds,
the real world is what actually happened in the past,
is actually happening right now,
and will actually happen in the future.
And while we certainly think about that world,
we also this enormous amount of time
considering all the many possible worlds.
What philosophers and psychologist typically
refer to as counterfactuals.
That is all the ways
that the world could have been but wasn't,
and all the ways that the world could be but aren't.
And not only is counterfactual thinking pervasive
in our every day thought,
perhaps you're doing it right now,
but engaging with these imagined possibilities
deeply effects us.
It effects our decisions,
it effects our judgements,
and it effects out emotional experiences.
And from an evolutionary perspective,
this initially seems a bit surprising, right?
Well, it's obvious why engaging deeply
with our actual real experience
would give us some sort of edge.
It's less obvious what we get from engaging so profoundly
and emotionally with these imagined worlds as well.
And this seems particularly paradoxical
when you consider the huge proportion of time
that very young children are engaging
with these imaginary worlds.
In fact, as soon as babies can talk,
they immediately begin talking about the possible,
in addition to the real,
they begin to spontaneously produce symbolic play,
substituting things like a mouse
from a computer for a telephone.
Very early on, around 18 months,
there's even evidence that 15 month olds
are recognizing pretend sequences
that are produced by adults in their environment,
so that's pretty early.
So, why, right?
Why would very, very young children,
who by their very definition
have so much that they have to learn about
the actual world, spend so much of their time,
and energy, and resources,
not to mention the resources of their caregivers
who are responsible for them,
engaging with unreality?
Right, we have to answer this question.
So classically, psychologists, including the father
of developmental psychology Jean Piaget,
but also our friend Sigmund Freud here
who pops up all over the place,
offered some pretty uncharitable characterizations
of pretend play in childhood.
They essentially attributed its prevalence
to children's inability to differentiate
between the products of their imaginations and reality.
Between fantasy and reality.
Decades of research have shown that, to the contrary,
children are actually quite proficient
and sophisticated at distinguishing
between real objects, events, and people,
and those that are products of their imagination
and the imaginations of other's around them.
I'm gonna give you just one example of a study,
this was conducted by Jackie Willy,
just to show you how this work is typically done with kids.
A child might enter a room with three boxes.
They'll watch as an experimenter puts a pencil in box one.
Box two is left empty, and box three,
the child is told to imagine
that there is a pencil inside the box.
Afterwards, the experimenter might ask
the child a bunch of questions and engage with them.
One of those questions will be,
is there a pencil in box three?
And children have no problem with this.
They say, yeah, sure, right?
They have no issue with transporting themselves
into this imagined space in which there is a pencil
inside of box three.
But if some person comes in from the other room,
who wasn't engaged in this fictional context initially
and says, hey I need a pencil, can you give me one?
Children even as young as two aren't going to make
the mistake of looking in box three.
They know there's no actual pencil in there.
Instead, they reach into box one
and give the experimenter
what it is that they actually asked for.
So even though children spend hours and hours
of their lives pretending,
they know that they're pretending.
And this ability then, to adopt this counterfactual
or false premise, like there's a pencil inside of this cup,
to make inferences about events that might happen
in a world in which there were a pencil in the cup,
but also to separate that imagined space
from the real world is already present
from as early as two years of age.
This is very, very early on.
In fact, there's other prominent features
of pretend play that suggest that it's the result
of competence rather than cognitive limitation.
So it's largely unique to human beings,
it's often social in nature,
like many of our more complex functions,
it becomes increasingly elaborate over time.
You'd expect the opposite if it was the result
of a cognitive limitation.
Young children do this object substitution,
as they get a little bit older they don't even need objects
to scaffold their pretend play with.
They just imagine things, completely imaginary events.
A little bit later, they might develop
an imaginary friend or companion.
This is an entity that has a consistent psychology
that they interact with over time.
A rich and complex psychology in social life.
Even later in late childhood, and adolescence even,
children engage with paracosms,
the little micro world that they construct
of their own design,
and, of course, as we know, this extends
into adulthood as well.
We all appreciate fictional artifacts
and this is continuous throughout the lifespan.
Given that very young children engage with imaginary worlds,
which seems obvious, and that this engagement
doesn't stem from their confusion,
which is a bit less obvious but not so much anymore,
then why are they doing it?
Why are they doing it and how?
How are they doing it?
Well, we know that play is characteristic
of young animals across a wide range of species
and that the behaviors that are involved in play
are also those that will typically be most important
for adults of that species.
And in this way, play is a form of exploratory learning.
So the immature animal can explore and practice
alternative forms of action in low cost,
low risk environment without any of the pressures
of having to actually achieve a particular goal,
like staying alive for example,
and, in fact, one of the most distinctive features,
biological features of human beings,
is our unusually long period of immaturity.
Compared with our closest primate relatives,
we've evolved to have this dramatically extended,
protected period of childhood.
Early, middle, late, adolescents,
after we go to college,
we're still protected in the spirit of immaturity,
and what we're encouraged to do
is explore during this period of time.
We're engaging in this exploratory learning.
So while it's sort of easy to see how physical forms
of exploratory play like play fighting and hunting,
and climbing, might translate into later adult skills,
pretend play is, sort of by its very definition,
severed from reality.
So in order to make this analogy with play,
with other forms of play work,
we have to really identify the role
that this particular type of cognition,
this counterfactual type of cognition plays in cognition.
So, to put this in the form of a question,
why might it be beneficial to draw conclusions
from false premises like there's a pencil in the cup?
So to answer this question we can consider
how children's minds are constructed to support
and also to encourage their generation of a wide array
of alternative possibilities.
And it turns out that new ideas about
children's earliest learning mechanism suggests
that the very same abilities that allow children to learn
so much about the world,
and to reason so powerfully about it,
also allows them to imagine alternatives to that world.
And more specifically, it's the ability to represent
cause and effect relationships that seems
to underpin some of the ability to imagine possible worlds.
And, not only that,
but the ability to imagine possible worlds,
feeds back to facilitate our reasoning
about cause and effect relationships.
So the rest of this talk, I'm going to,
very quickly try to unpack
the sort of theoretical grounds for making this claim.
So by about five years of age,
children have already developed complex causal theories
in variety of domains.
Everything from understanding biological principles
to other minds to the nature of other physical forces
and properties in the world.
And the question that motivates my research,
but also just sort of the field of cognitive development
in general is just how this ever happened.
How is that young children are able to learn
these abstract, structured, causal representations
of the world so quickly and accurately,
given the relatively limited information that's available
to them from their senses.
What's the origin of this knowledge?
And one classic answer from developmental psychology,
points to the similarities between children's learning
and learning in science.
And the idea here proposes that children's early theories
share, in a meaningful way, structure, function,
and dynamics to theory change in science.
And in particular, that children just like little scientists
are implicitly formulating hypotheses about the world,
and then testing and rationally revising those hypotheses
in light of new evidence that they observe.
So this sounds a bit far fetched when you first hear it.
To help you imagine this,
I'm going to show you a video of this idea.
What this child is doing in this video
is playing with a blicket detector,
which is a toy that we typically use in my lab.
This is just a flexible causal system.
It's a box that lights up, which is the effect,
for certain things, which is the cause.
And it allows us to explore
children's causalate inferences really well.
So I'm just gonna let you watch
and I want you to keep an eye out for the child
engaging in hypothesis testing behavior,
similar to a scientist.
- We need this on the box and this on the box, look.
- [Experimenter] Uh huh.
- This makes that light up the box.
- Mm hmm. - How about this.
That makes the other side.
- [Caren] Here is a new hypothesis.
- Uh oh.
Nothing.
This one's lighted up and this one's not.
So that means.
- [Woman] Here's another.
- What's making this light up?
Hmm.
- [Caren] That's a familiar expression to those
of us who do science. (audience laughing)
Despair.
- Oh no.
Oh it's because that this needs to be like this.
And this needs to be like that.
That's why.
Oh.
Probably the boxes are the wrong way.
- This was the child's idea, pretty imaginative.
(audience laughing)
And like in science, it ends with embarrassment
in front of our peers.
So even though these ideas about children's learning
have been around for quite some time,
recently there's been some major advances
in our ability to formally describe
the cognitive processes that might be taking place
and the way that this is done
is by integrating developmental psychology
so this kind of work with computational theories.
So one of the central ideas in this frame work
is that children's intuitive causal theories
can be expressed in a kind of causal map
or abstract picture of how the world works.
A little bit like this.
So for example, sunlight and water cause plants to grow,
forces and contact cause objects to move through space,
desires and beliefs cause someone
to act towards a particular goal.
And in many ways, these causal maps are analogous
to the more familiar spacial maps that depict
the various locations of objects
in relation to one another.
This is a cognitive feature
that we share with other animals,
including rodents, like depicted here.
So having a special map is useful
and this is mentioned earlier
because it allows for this
non egocentric representation of knowledge.
It doesn't matter where I am in the space,
I can still represent the space.
This means that it's flexible.
I can plan my route in advance
and think about the different ways
that I might approach this problem.
And it becomes updated as new information
about the space becomes available.
So in similar way,
having a causal map provides a complex representation
of the causal relationships or an abstract picture
of how one thing might be causally connected to another,
and, just like our special maps, it's updated
as new information becomes available to us.
So you can think of each of these different causal
models as a particular hypothesis
that we might hold about the true
causal structure of the world.
So, for example, if I notice that the flowers
in my window begin to wilt
I might entertain several possible causal models.
Each of which generate their own patterns of predictions.
So it could be that too much sunlight
is causing both the dry soil and the wilted flowers,
or it could be that the sunlight is actually
causing the dry soil and it's the dry soil,
right, that's causing my flowers to wilt.
And if I'm holding a causal model that happens to be correct
and the predictions that it generates will be accurate
with respect to my observations in the world.
But if it's incorrect, if I hold the wrong causal model,
my predictions are going to fail me.
And this will prompt me to adjust my causal model
to better approximate the true causal structure
of the world.
So in affect, this process, the process of early learning,
might be conceived as a process of comparing possible worlds
and updating those possibilities in light
of new evidence as you observe it.
And critically these casual maps also include
a means for representing possible future actions
for planning in the world.
So if we return to the two sort of versions
of the wilted flowers that I described earlier,
even though each of these representations
have the save variables, sunlight, soil, flowers,
the differences in their structure lead
to really different effects following some action
that I might take on the world.
So let's say I intervene on my dry soil
by watering my plants.
Hopefully what you can see here
is that depending upon which of the two causal structures
is an accurate representation of the world,
watering my plants here in the first one
is gonna have no effect on my flowers
right because it's the sunlight that's
directly causing them to wilt.
In the other case though,
watering the soil will actually have some effect.
And importantly these interventions could be real.
I could actually do them.
Or they can be imagined hypothetical actions.
I can just sort of think what it would be like
if I were to intervene on the world in a particular way.
And it turns out, that the evidence shows,
that even preschool aged children are able to do this.
Are able to reason about interventions,
both in the real world and also in their imaginations.
So this gives us an extremely powerful tool
for planning and considering in the outcomes
of potential actions in advance.
We start with a premise that might be false
with respect to the world
and then we just reason about the implications
of that premise downstream.
This leads us to the ability to design new interventions
and to literally change the future
for ourselves and our environment.
So now we have to push the pause button for a minute
'cause this all sounds really, really complicated to us.
All of these things are, of course,
happening implicitly not explicitly
but you might be wondering whether
or not kids could actually do this.
So if we return to pretend play for a minute,
we see that children are routinely considering premises
that contradict their own knowledge.
They ignore the fact that the teacup is empty
and they proceed to wipe up the imagined tea
when the cup is overturned anyway.
Any time, really, that children are acting out
the outcome of pretend events, they're necessarily
setting aside their interpretation, their causal model
of the real world, and reasoning
about the causal consequences of some pretend premise.
Some other possible world.
And in fact,
it's causation itself that gives fantasy its logic.
Despite the fact that children could, in principle,
pretend about anything at all, it's pretend after all,
if you've ever hung out with children,
you know that they don't actually usually do this.
Instead, some research by Paul Harris has shown
that if a child pretends to spill the sugar
during their tea party, they're gonna opt
to sweep it up with a broom.
If they spill the milk, then they'll grab a mop or a sponge.
And it's precisely this unique blend of knowledge
and imagination that really characterizes
early pretend play in childhood.
And in fact, the cognitive processes that are involved
in pretend play, aren't only useful for planning,
they're also critical for learning.
For example, children who create imaginary companions
tend to show increased theory of mind.
So this is just an increased understanding
of the cause and effect relationships
that dictate the psychological and social world.
So I propose then that pretend play is really
just a precocious display of children's developing abilities
in causal reasoning.
It arises out of those abilities quite naturally.
And that engagement in imaginary worlds actually feeds back
to serve as an engine of learning as well
promoting these abilities that we need.
So to sort of summarize the logic in a single slide here,
the long period of protected immaturity winds up leading
to increased time for exploratory learning through play.
Exploratory play allows for more flexible kinds of learning
mechanisms that support the development of causal models
that slowly adjust to the environment over time.
These models support counterfactual reasoning,
it's sort of inherent to the model to think about ways
that you might change it in order to think
of how things could be different.
And this is initially expressed in young children
in the context of pretend play
really as early as they can start to talk.
And finally that reasoning about these possibilities
feeds back to support the very mechanisms
that underlie causal learning in humans.
So I'm gonna end with a quote
from my colleague Alison Gopnik,
with whom I've coauthored all of my work in this area,
and I'd like to thank you for your attention.
(adience applauding)
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