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.