Hi, my name is Jennifer Nagel. I teach philosophy at the University of Toronto,
and today I want to talk to you about the development of mindreading.
Most adults are good at mindreading: we can detect what others are aiming at,
what they can see, and roughly how they are feeling.
We can even pick up on subtle social moves like sarcasm,
where a person expresses something opposed to the literal meaning of their words.
Mindreading is easily taken for granted, although when we reflect on it,
we realize that it involves a complex set of skills.
We can learn something about that skillset by looking at how it develops over time.
Human babies are not born knowing what others can see.
But by two months of age, when babies are shown a picture of a face,
they look more at the eyes than other regions,
and by 4 months, babies prefer looking at eyes that are looking right back at them.
By 9 months, babies follow when an adult turns her head as if to look at something:
the baby orients towards whatever the adult is turning to.
But 9-month babies have only a crude form of gaze following,
because they will follow head turn towards distant objects
even when the adult’s eyes are shut;
babies learn the difference around 10-11 months of age,
now following gaze to a distant object
only when the adult who is turning her head towards something has her eyes open.
These developments are vital for joint attention, in which you and another person
not only focussed on the same object, but do so in the awareness that the other
is also looking at it, checking back with them to see where they are looking.
This capacity develops over time, with babies first following other agents’
bids for joint attention as early as 8 months,
and then learning to launch their own bids for joint attention by 10-12 months,
for example by pointing while looking at an object.
As babies are gaining a better understanding of what others can see,
they’re also gaining a better understanding of what others want.
By the one-year mark, babies understand agents as having goals,
expecting them to take the most direct path towards the thing that they want,
even if in the past, these agents took a different path,
for example because something was previously blocking their way.
Researchers test this with a “violation of expectancy” paradigm,
taking advantage of the fact that we look longer at unexpected events.
If babies have been watching an animated agent perform a hopping motion
to get over a barrier towards a goal, then when the barrier is removed,
they are more surprised to see that hopping motion continue
than to see the agent move straight through now towards the target.
So, one-year-old babies don’t just expect to see
the same surface patterns of movement from agents;
they expect agents to move in a way that makes sense, given some goal.
It is not clear that babies at this age can already understand
inner states like desires the way we do:
it's been argued that they just have some more primitive sense of
how things should turn out, so they couldn’t, for example,
think flexibly about agents who have different goals.
By 18 months, however, toddlers can see others
as having preferences different from their own,
expecting for example that a person who has been seen to prefer carrots over cookies
will choose a carrot at snack time, even if that is not the toddler’s own preference.
Tracking what others know and believe is harder than tracking what people can see,
because states of knowledge and belief are formed over extended periods of time:
to figure out what you believe, it is not enough
to know what you are looking at right now,
I also need to remember what you have seen in the past.
If I’m curious about what you do and don’t know,
I am just looking at the history of your relationship to reality,
and figuring out what parts of it are open or blocked for you.
Figuring out what you believe is even harder, because I also need to keep track
of contents that can be different from the way the world is now:
unlike knowledge, belief can diverge radically from reality.
It is not clear exactly when children understand belief.
By the age of 5, most children can watch an agent being tricked
and accurately report what this person will do as a result of their false belief.
But there are signs that children understand something about false beliefs earlier.
By their third birthday, children look in the right direction
when they anticipate the action of someone with a false belief.
Some researchers have reported substantially earlier implicit signs
of false belief comprehension, but those signs are hard to interpret,
and this research is controversial.
Some researchers (the minimalists) argue that infants have a simpler system
that just tracks constellations of agents and objects in a limited way,
until our full blown belief detection system launches in the fourth year of life.
Other researchers (the mentalists) think mental state understanding is innate
or very early developing, but not fully visible in early development
because of independent limits in following complex sequences of events,
and answering tricky questions.
One of the last milestones in development is the hidden emotion test:
imagine that someone Billy likes has given him a present he hates.
By the age of about seven, children expect that Billy will pretend to be happy,
but before that age, the notion that someone might
deliberately fake an emotion is hard to grasp.
There is something complex about hidden emotions:
to make sense of this split between how someone feels inside and how they look
on the outside, we need to understand that the agents we are mindreading
are themselves also mindreaders, who care what others will think of them.
Even as adults, we sometimes have have childlike tendencies in our mindreading.
For example, kids find it hard to grasp the perspective
of those who know less than they do about a scene.
Especially when we are busy and distracted, adults can also be biased
towards unreasonably expecting others to share their perspective.
Studying the development of our mindreading capacity
can give us a sharper view of its limits.
The next video in this series explores some
different theories of how mindreading works.