[school bell rings]

-If I eat 100 marshmallows,
I would be filled up!

(Richard Aslin)
Everybody knows that young children,

particularly toddlers--
two to four-year-olds--

are subject to impulsivity,

and it has been thought that
that is a characteristic

that children are born with.

-Do you know what?
It is snack time now.

-And so, what we wanted to know
is whether or not

some of these differences
between children

can be influenced by their own
rational thought processes.

-We wanted to manipulate
children's beliefs

about how reliable the environment
that they were in was.

We assign kids to one of two conditions:

either the reliable condition
or the unreliable condition.

-So, for the art supplies
that you get to use,

you actually have a choice.

You can either use these crayons
right now,

or if you can wait for me to go get some
from the other room,

you can use our big set of art supplies
instead.

(Celeste Kidd)
The kids in the reliable condition,

when the team member came back
into the room,

had the better thing,
and for the kids

in the unreliable condition,
the experimenter apologized,

and said she made a mistake,
we didn't have that available,

and then helped them use
the first option.

-I'm so sorry, but I actually don't have
that big set of art supplies

I told you about.
Sorry about that.

But you can still use these ones
to make your project.

(Aslin)
A classic example of a task

in which children show impulsivity

is what's called
the "marshmallow task".

-For your snack, you have a choice.
Look what I've got.

-[gasp] A marshmallow!

-Yeah! So, wait, just a second;
let me explain.

So, you can either eat
this one marshmallow right now,

or if you can wait for me to go get it
from the other room,

you can have two marshmallows instead.

-I want two marshmallows!

(Aslin)
And what we found,

which was an incredibly large effect,

the children who were in
the unreliable group

were more likely to fairly quickly

pick up the marshmallow
and eat it.

So, on average,
they waited about three minutes.

-And did you know,
I did not eat this marshmallow yet?

(Aslin) The children
who were in the reliable group

waited four times longer,
so they waited about 12 minutes,

which is an incredibly long time

for young children to wait
before they get a reward.

(Kidd) The difference
is maybe due to differing expectations

about what's likely to happen
in the world.

That's what this experiment
was designed to address.

-For any three year old,
self-control is not necessarily

at the top of their skill base.
[laughs]

But, in general,
when she sets her mind

that she's going to do something,
she's going to do it.

(Kidd) In the marshmallow task,
what you want to do

is you want to get
the most amount of marshmallow possible,

but there may be other considerations.

Given that I have this one marshmallow
now that's guaranteed,

what are the chances that if I wait,

there's going to be a second marshmallow
later?

-If it was a teacher he had
all the time, that if--

they would have that trust bond
a little bit longer,

then he'd probably wait longer.

(Aslin)
One of the lines of work

that evolved as a result
of the marshmallow task

was to look at the outcomes

of children's behavior
later in life,

but something that's been missing
from the equation

is this rational process
by which children

are accessing information
in their environment

and making decisions about
whether they should behave

in the short term
or behave in the long term.

So, if they're in an environment

in which long term gain
is very rare,

well then, it makes perfect sense
for them to behave impulsively

because that's going to maximize
their reward.

-How's it taste?
-Mmmm!

(narrator) A production
of the University of Rochester.

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[school bell rings]