How does income affect childhood brain development? | Kimberly Noble

What I'm about to share with you are findings from a study

of the brains of more than 1,000 children and adolescents.

Now, these were children who were recruited

from diverse homes around the United States,

and this picture is an average of all of their brains.

The front of this average brain is on your left

and the back of this average brain is on your right.

Now, one of the things we were very interested in

was the surface area of the cerebral cortex,

or the thin, wrinkly layer on the outer surface of the brain

that does most of the cognitive heavy lifting.

And that's because past work by other scientists has suggested

that in many cases,

a larger cortical surface area

is often associated with higher intelligence.

Now, in this study, we found one factor

that was associated with the cortical surface area

across nearly the entire surface of the brain.

That factor was family income.

Now, here, every point you see in color is a point where higher family income

was associated with a larger cortical surface area in that spot.

And there were some regions, shown here in yellow,

where that association was particularly pronounced.

And those are regions that we know support a certain set of cognitive skills:

language skills like vocabulary and reading

as well as the ability to avoid distraction

and exert self-control.

And that's important,

because those are the very skills

that children living in poverty are most likely to struggle with.

In fact, a child living with poverty

is likely to perform worse on tests of language and impulse control

before they even turn two.

Now, there are a few points I'd like to highlight about this study.

Number one:

this link between family income and children's brain structure

was strongest at the lowest income levels.

So that means that dollar for dollar,

relatively small differences in family income

were associated with proportionately greater differences in brain structure

among the most disadvantaged families.

And intuitively, that makes sense, right?

An extra 20,000 dollars for a family earning, say, 150,000 dollars a year

would certainly be nice, but probably not game-changing,

whereas an extra 20,000 dollars

for a family only earning 20,000 dollars a year

would likely make a remarkable difference in their day-to-day lives.

Now, the second point I'd like to highlight

is that this link between family income and children's brain structure

didn't depend on the children's age,

it didn't depend on their sex

and it didn't depend on their race or ethnicity.

And the final point --

and this one's key --

there was tremendous variability from one child to the next,

by which I mean there were plenty of children from higher-income homes

with smaller brain surfaces

and plenty of children from lower-income homes

with larger brain surfaces.

Here's an analogy.

We all know that in childhood,

boys tend to be taller than girls,

but go into any elementary school classroom,

and you'll find some girls who are taller than some boys.

So while growing up in poverty is certainly a risk factor

for a smaller brain surface,

in no way can I know an individual child's family income

and know with any accuracy

what that particular child's brain would look like.

I want you to imagine, for a moment, two children.

One is a young child born into poverty in America;

the other is also an American child,

but one who was born into more fortunate circumstances.

Now, at birth, we find absolutely no differences

in how their brains work.

But by the time those two kids are ready to start kindergarten,

we know that the child living in poverty

is likely to have cognitive scores that are, on average, 60 percent lower

than those of the other child.

Later on, that child living in poverty

will be five times more likely to drop out of high school,

and if she does graduate high school,

she'll be less likely to earn a college degree.

By the time those two kids are 35 years old,

if the first child spent her entire childhood living in poverty,

she is up to 75 times more likely to be poor herself.

But it doesn't have to be that way.

As a neuroscientist, one of things I find most exciting about the human brain

is that our experiences change our brains.

Now, this concept, known as neuroplasticity,

means that these differences in children's brain structure

don't doom a child to a life of low achievement.

The brain is not destiny.

And if a child's brain can be changed,

then anything is possible.

As a society, we spend billions of dollars each year, educating our children.

So what can we tell schools, teachers and parents

who want to help support kids from disadvantaged backgrounds

to do their best in school and in life?

Well, emerging science suggests

that growing up in poverty is associated with a host of different experiences

and that these experiences in turn may work together

to help shape brain development and ultimately help kids learn.

And so if this is right,

it begs the question:

Where along this pathway can we step in and provide help?

So let's consider first intervening at the level of learning itself --

most commonly through school-based initiatives.

Now, should we be encouraging teachers to focus on the kinds of skills

that disadvantaged kids are most likely to struggle with?

Of course.

The importance of high-quality education based in scientific evidence

really can't be overstated.

And there are a number of examples of excellent interventions

targeting things like literacy or self-regulation

that do in fact improve kids' cognitive development and their test scores.

But as any intervention scientist doing this work would tell you,

this work is challenging.

It's hard to implement high-quality, evidence-based education.

And it can be labor-intensive,

it's sometimes costly.

And in many cases, these disparities in child development emerge early --

well before the start of formal schooling --

sometimes when kids are just toddlers.

And so I would argue:

school is very important,

but if we're focusing all of our policy efforts

on formal schooling,

we're probably starting too late.

So what about taking a step back

and focusing on trying to change children's experiences?

What particular experiences are associated with growing up in poverty

and might be able to be targeted to promote brain development

and learning outcomes for kids?

Of course, there are many, right?

Nutrition, access to health care,

exposure to second-hand smoke or lead,

experience of stress or discrimination,

to name a few.

In my laboratory,

we're particularly focused on a few types of experiences

that we believe may be able to be targeted

to promote children's brain development

and ultimately improve their learning outcomes.

As one example,

take something I'll call the home language environment,

by which I mean, we know that the number of words kids hear

and the number of conversations they're engaged in every day

can vary tremendously.

By some estimates,

kids from more advantaged backgrounds

hear an average of 30 million more spoken words

in the first few years of life

compared to kids from less advantaged backgrounds.

Now, in our work, we're finding

that kids who experience more back-and-forth,

responsive conversational turns

tend to have a larger brain surface in parts of the brain

that we know are responsible for language and reading skills.

And in fact, the number of conversations they hear

seems to matter a little bit more than the sheer number of words they hear.

So one tantalizing possibility

is that we should be teaching parents not just to talk a lot,

but to actually have more conversations with their children.

In this way, it's possible that we'll promote brain development

and perhaps their kids' language and reading skills.

And in fact, a number of scientists are testing

that exciting possibility right now.

But of course, we all know

that growing up in poverty is associated with lots of different experiences

beyond just how many conversations kids are having.

So how do we choose what else to focus on?

The list can be overwhelming.

There are a number of high-quality interventions

that do try to change children's experience,

many of which are quite effective.

But again, just like school-based initiatives,

this is hard work.

It can be challenging,

it can be labor-intensive,

sometimes costly ...

and on occasion,

it can be somewhat patronizing for scientists to swoop in

and tell a family what they need to change in order for their child to succeed.

So I want to share an idea with you.

What if we tried to help young children in poverty

by simply giving their families more money?

I'm privileged to be working with a team of economists,

social policy experts and neuroscientists

in leading Baby's First Years,

the first-ever randomized study

to test whether poverty reduction causes changes in children's brain development.

Now, the ambition of the study is large,

but the premise is actually quite simple.

In May of 2018,

we began recruiting 1,000 mothers living below the federal poverty line

shortly after they gave birth in a number of American hospitals.

Upon enrolling in our study,

all mothers receive an unconditional monthly cash gift

for the first 40 months of their children's lives,

and they're free to use this money however they like.

But importantly, mothers are being randomized,

so some mothers are randomized to receive a nominal monthly cash gift

and others are randomized to receive several hundred dollars each month,

an amount that we believe is large enough

to make a difference in their day-to-day lives,

in most cases increasing their monthly income by 20 to 25 percent.

So in this way,

we're hoping to finally move past questions

of how poverty is correlated with child development

and actually be able to test whether reducing poverty causes changes

in children's cognitive, emotional and brain development

in the first three years of life --

the very time when we believe

the developing brain may be most malleable to experience.

Now, we won't have definitive results from this study for several years,

and if nothing else,

1,000 newborns and their moms will have a bit more cash each month

that they tell us they very much need.

But what if it turns out that a cost-effective way

to help young children in poverty

is to simply give their moms more money?

If our hypotheses are borne out,

it's our hope that results from this work will inform debates about social services

that have the potential to effect millions of families with young children.

Because while income may not be the only or even the most important factor

in determining children's brain development,

it may be one that,

from a policy perspective,

can be easily addressed.

Put simply,

if we can show that reducing poverty changes how children's brains develop

and that leads to meaningful policy changes,

then a young child born into poverty today

may have a much better shot at a brighter future.

Thank you.

(Applause)