Kimberly Noble: How family income affects child brain development At birth, babies' brains look pretty similar. But by age five, there are acute disparities in development. Through a series of studies, Kimberly Noble has found one major factor is family income.

By age five, children's brains can look very different—and family income is a factor

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It's the TED Radio Hour from NPR. I'm Manoush Zomorodi, and on the show today, the brain and how it changes at every stage of life, starting on Day 1.

SANAZ MESHKINPOUR, BYLINE: Mina, sleepyhead, wake up.

ZOMORODI: Because from the moment we're born, the world around us begins to shape how our brain works.


UNIDENTIFIED PERSON #1: Sweetheart, you have the hiccups. Yeah.

ZOMORODI: Within the first few days and weeks of a baby's life, she learns to recognize her parents, to coo and smile.


ZOMORODI: Another few months, and she'll giggle...


UNIDENTIFIED PERSON #2: You silly baby.

ZOMORODI: ...Show off new motor skills...

MESHKINPOUR: Are you trying to flip onto your stomach? You can do it, my love.

ZOMORODI: ...And start babbling to communicate, prompting us grown-ups to babble back.



ZOMORODI: Soon, little ones pick up words with real meaning.





UNIDENTIFIED PERSON #4: Can you say ball?


UNIDENTIFIED PERSON #4: Can you say dada?


ZOMORODI: And every day they understand more about the world around them.

UNIDENTIFIED PERSON #5: Show me your elephant, Mabel. What is it?

MABEL: (Blowing raspberry).

COOPER: I want to see it.

UNIDENTIFIED PERSON #6: Do you want to do it? Can Cooper have a turn?

UNIDENTIFIED CHILD #1: No, five minutes.

COOPER: I want to see.

ZOMORODI: And they'll work to build skills they'll use their whole lives...

UNIDENTIFIED CHILD #2: ...Five, six, seven, eight, nine, 10. Yay.

ZOMORODI: ...Which sometimes means singing along to the same song every single day.

UNIDENTIFIED CHILD #3: (Singing) Let it go. Let it go. Turn away and slam the door. Here I stand.

ZOMORODI: All this is to say there is a lot happening in a child's brain during those first few years.

KIMBERLY NOBLE: We're born with a hundred billion neurons or brain cells. And every minute in the first few months of life, we generate between 250,000 and 500,000 new brain cells or neurons - every minute.

ZOMORODI: This is Kimberly Noble. She's a professor of neuroscience at Columbia University.

NOBLE: But it turns out that most of our brain growth early in life isn't actually the development of new brain cells but the connections between cells. If you look at it under a microscope, we don't see that many connections between brain cells when we're born. But by the time we're 3 years old, we have a thousand trillion connections between our cells. And we know that early experience really helps to shape that synaptic developmental process. People have said that the human brain is the most complex three pounds in the universe. And I love that saying 'cause it really sort of gets to the amazing complexity that happens with all of us in the first few years of life.

ZOMORODI: During each stage of our life, our brain morphs and changes from those first moments through our cringy (ph) teens, well past adulthood, midlife and into our senior years. Our experiences shape how our brain develops, but so do our genetics, hormones and even what we eat. And so today on the show, ideas about the brain at every stage of life, how it changes from childhood into old age and the pivotal moments when a mind can either flourish or decline. Kimberly Noble's focus is on early childhood because those first few years, even before kids go to school, are really important for brain development. And she's wondering why some kids get to kindergarten and are able to hit every cognitive and developmental milestone while others struggle.

NOBLE: We know that by the start of school, we already see dramatic differences in what we call early school readiness skills - early literacy and early math. And those differences tend to persist across most schooling. So the gap doesn't ever really narrow and in some cases may widen, which of course leads to differences in high school achievement, high school graduation rates, college attendance rates and ultimately employment.

ZOMORODI: Here's Kimberly Noble on the TED stage.


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. 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.

ZOMORODI: Family income. The study looked at families with incomes ranging from $20,000 a year to $200,000 a year, and they found that families with more resources tend to have an advantage. There's less stress in the household, more time to interact and access to more nutritious food. And on average, higher income meant increases in brain surface area and higher cognition.

NOBLE: It's also very important to keep in mind that, you know, while we can say that on average, in this sample of more than a thousand children and teens - on average, higher family income was associated with larger brain surfaces, that's just an average. So 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. So in no way could I know an individual child's family income and predict with any accuracy what that particular child's brain surface would look like.

ZOMORODI: Right. But what you can say is that the chances are that - if you lived in a higher-income family, the chances are that that surface of the brain would be bigger, and you would have a higher aptitude.

NOBLE: That's right. That's right. And the relationship between income and children's brain structure was actually steepest at the low end of the income distribution. So an extra $10,000 a year for a family earning a hundred-thousand dollars a year would certainly be nice but probably wouldn't have a dramatic effect on their day-to-day lives, whereas an extra $10,000 for a family only earning $20,000 a year would likely make a pretty remarkable difference in their day-to-day lives.


NOBLE: 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% lower than those of the other child.

Later on, that child living in poverty will be 5 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.

ZOMORODI: OK, again, these are averages. And there are lots of factors at play here - for example, the systemic racism that makes it 3 times as likely that Black and Hispanic children will grow up in poverty compared to white children in the U.S. But Kimberly is strictly looking at the effects of income on brain development. And when she controlled for race, gender and genetic ancestry...

NOBLE: We didn't find any what we would call statistical interaction between income and gender or income and race, meaning that this effect of income was consistent whether the child was a boy or a girl and regardless of their racial backgrounds.

ZOMORODI: And so what's happening in these families that plays such a big role in the developing brains of their children?

NOBLE: So we think that there are likely a lot of mechanisms and pathways that sort of account for those links between family income and children's outcomes. You know, one thing we've been very interested in is differences in family stress. So we know from a great deal of research in both animals and humans that there are certain areas of the brain that are particularly sensitive to the experience of stress. And so we reasoned that since we see socioeconomic differences in those regions, they may be partially accounted for by differences in the experience of stress across families.

We have recently started measuring stress not just in terms of the perception of stress, but also in terms of stress physiology by taking small samples of hair, which can then tell us about the average levels of cortisol - stress hormone - for the last several months. And on average, more advantaged parents tend to have lower levels of hair cortisol, supporting this idea that the biology of stress really might account for socioeconomic differences in brain development in kids.

ZOMORODI: And stress for parents could present itself in lots of ways, like access to health care or nutritious food or hourly jobs where you can't leave to go pick up your kid or go to a doctor's appointment. Like, stress compounds in many, many ways when money is tight, right?

NOBLE: Absolutely. So there are lots of different experiences that contribute to stress and lots of different sort of ways to measure stress, right? So we try to get at numerous different facets of stress in the measures that we include.


NOBLE: But it doesn't have to be that way. As a neuroscientist, one of the 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. 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 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.

ZOMORODI: So if it's too late by the time kids get to kindergarten, how can we as a society make sure every child's basic needs are met? When we come back, Kimberly Noble shares one big idea. On the show today, ideas about the brain at all stages of life. I'm Manoush Zomorodi, and you're listening to the TED Radio Hour from NPR.


ZOMORODI: It's the TED Radio Hour from NPR. I'm Manoush Zomorodi. On the show today, life stages of the brain. And we were just talking to neuroscientist Kimberly Noble, who says that a huge factor in the way a child's brain develops is family income, with the biggest difference for kids living under the poverty line.


NOBLE: 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? Well, of course, there are many - right? - nutrition, access to health care, exposure to secondhand 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. 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?

NOBLE: We've known for decades from work by social scientists and others that growing up in poverty puts kids at risk for a host of negative outcomes in terms of their cognitive development, their social-emotional development, their brain development, their mental and physical health. However, there are many people who would say, well, poverty isn't the cause of those problems; it's all of the things that are associated with poverty that are really driving those effects. And from a scientific perspective, the only real way to answer that is through the gold standard of scientific study designs, which is a randomized controlled trial.

ZOMORODI: Which is what you did, right? In 2018, you started the Baby's First Years study and recruited about a thousand low-income mothers to participate after they gave birth, right?

NOBLE: Right. And upon enrolling in the study, all mothers began receiving an unconditional monthly cash gift every month for the first 40 months of their children's lives, so till just after their children turned 3. But we randomized the moms to either receive a large monthly cash gift of $333 a month or a nominal monthly cash gift of $20 a month. And that difference has been shown in the social science literature to be associated with improvements in children's academic achievement, improved time - more time spent in the labor force when children grow up and even better health when children grow up. But

again, the past work was really looking at correlational findings, so associations between higher income and children's outcomes, but they didn't rely on causal evidence. So here, we're able to actually examine, what's the causal impact of poverty reduction on children's cognitive, emotional and brain development in the first three years of life when we believe that the developing brain is most malleable to experience?

ZOMORODI: OK, but there are going to be some people who say, like, this sounds kind of simplistic, like you're throwing money at a problem. But this trial, which we should say is the first of its kind, could actually have huge policy implications, right? I mean, you know, ideally, we'd live in a more equitable society where the basic needs for a child's physical and emotional and cognitive health would be met from day one, but we don't. And so these findings could actually help us make policy to change that.

NOBLE: Yeah, you know, it's an interesting question. So, you know, I do think to the extent that neuroscience can help in convincing people about these very real needs, then, you know, I'm all for it. I also think it's important to think about shifting the conversation and shifting the spotlight onto children, right? So much of the intergenerational cycle of poverty has often been attributed to, you know, whether individuals are willing to pull themselves up from their bootstraps. But babies don't have bootstraps.

And so when we think about that - right? - so if we are shifting the spotlight onto children, who we all agree, it's not up to them if they're provided with resources or not, but if we take a step back even further and address income disparities themselves, and, you know, empower families to spend money on things that they actually need to support their own family's well-being, it's suddenly a very different conversation.


NOBLE: Now, we won't have definitive results from this study for several years, and if nothing else, a thousand 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 affect 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.


ZOMORODI: That's Kimberly Noble. She's a professor of neuroscience at Columbia University. You can find her full talk at

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