[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]