Why do some children who grow up in poverty do well, while others struggle?
To understand more about this, a group of psychologists recently did a study.
It began in a small spare room where a series of very poor mothers and their 5-month-old babies came to watch a soothing video. Soothing the baby was the point, says Elisabeth Conradt, a postdoctoral researcher at Brown University's Brown Center for the Study of Children at Risk. The researchers needed to take measurements of the babies when they were calm.
On the screen, circles of gently colored shapes flickered and music softly played while a sensor taped to the baby's chest recorded how much the baby's heart beat when the baby breathed in, and how much the baby's heart beat when it breathed out.
This simple measure has a complicated scientific name that sounds vaguely like a disease — baseline respiratory sinus arrhythmia — but the researchers were interested in it because it can tell you something about how a baby responds to the world around it.
You see, while there's always a difference between how much the heart beats when a person inhales and when he or she exhales, everyone has a different set point. Sometimes there's a big difference, and sometimes it's small. And in very young babies, researchers have noticed that there are different temperaments associated with these different set points.
When there's a big difference and the set point is high, babies tend to have great attention and can focus for long periods of time on the things in their environment. "When you're presenting them with a new toy, they're going to really look at it and inspect it," says Conradt. "But they also may be more irritable and fussy when parts of their environment are changing."
In contrast, babies with a low set point "might lose interest after a couple minutes, but they're also not going to be as fussy or irritable," she says.
Babies with a high set point seem to have a more sensitive nervous system, which makes them more sensitive to their environment, in both good and bad ways. Babies with a low set point seem to have a less sensitive nervous system, which makes them less sensitive to their environment.
Conradt and her colleagues wondered if this simple measure could be used to predict how children in poverty would fare as they aged.
A year after taking this first measurement, the mothers and their children came back into the lab for two more tests.
The children were first evaluated for behavioral problems like aggression and anxiety. Then they were given a classic psychological test known as the strange situation procedure.
In this test, the mother and child — now around 17 months old — are led to a strange room. For a while the toddler plays happily, but then, abruptly and without warning, the mother leaves.
Because this is a strange room in a strange place, the baby reacts — most cry. But the part of the procedure that's most important to researchers happens when the mother returns three or four minutes later.
"It's how that baby greets or responds to her mother when her mother comes back that gives us some clue of the kind of history that these two have had together," says Jeffrey Measelle, a psychologist at the University of Oregon in Eugene, who worked on the study.
If the toddler is easily soothed by the mother, the researchers conclude that their attachment is strong and that the environment the toddler has grown up in is relatively secure. But if the toddler doesn't seem comfortable with the mother and can't be soothed, the researchers conclude that the attachment is poorer and that the environment the child is growing up in is probably unstable.
"It gives us some sense that that's probably the way those two have been interacting over time," says Measelle.
Which brings us back to that original measure of breathing and heart rate.
When the researchers looked at how a child's behavioral problems correlated with the early measurement, the researchers found that kids with high set points were significantly more sensitive to the environment they grew up in than the children with the low set points. If the baby had a high set point and an insecure attachment to his or her mother, the child's later behavior was often deeply troubled. These were by far the worst of all of the kids.
But if the child had a high set point and a secure attachment, "those were the kids that were doing the best — the absolute best — of all of the kids in our sample, and they had far and away the lowest reported problem behaviors," Measelle says.
The children with low set points were not as good or as bad, no matter their parenting.
The behavior of the children with high set points and secure attachments to their mothers compared favorably with the behavior of children whose environments were often much easier. "These babies were looking a lot better behaviorally than a lot of babies growing up in middle class and advantaged samples," says Measelle.
The researchers hope that this simple measure of a baby's breathing and heart rate might one day be used to flag children in poverty who have high set points — a biological marker of which children will be more sensitive to their environment — for better and for worse.
AUDIE CORNISH, HOST:
From NPR News, this is ALL THINGS CONSIDERED. I'm Audie Cornish.
Among children who grow up in poverty, some do well, others struggle. So why the difference? A group of researchers from Brown and the University of Oregon set out to find some answers.
NPR's Alix Spiegel has the story on their study and what they learned.
ALIX SPIEGEL, BYLINE: The experiment began in a small spare room. There was a chair for the mother to sit in, her five-month-old baby on her lap and then a television which played a soothing video. Soothing the baby, says researcher Liz Conradt, was the point of all of this. Because they needed to take a measure of the babies breathing and heart beat when the baby was calm. And so on the screen, circles of gently colored shapes flickered and music softly played.
LIZ CONRADT: One of Mozart's pieces. I can hum it if you want.
CONRADT: It goes like (humming)
(SOUNDBITE OF MUSIC)
SPIEGEL: In this video from the study, you can see a mother and child steadily rocking back and forth. The mother, like every mother in the study, lives in poverty and likely is struggling with other things as well: physical abuse, mental illness. This means that the child on her lap - the five-month-old with a curl of hair - probably won't have an easy time. So will this particular kid struggle with behavior problems and dysfunction? Or will she thrive despite the hard road she's on?
Liz Conradt wanted to know if there was some way to predict, to see into the future. So she taped a sensor to the baby's chest to monitor her breathing and heartbeat, a simple physical measure.
CONRADT: It's how your heart rate changes in response to breathing. When you inhale your heart rate increases, and when you exhale your heart rate decreases.
SPIEGEL: That happens with everybody?
CONRADT: It happens with everybody.
SPIEGEL: And this can tell researchers which babies are vigilant about their environment and which babies are less sensitive to what's going on around them. See, we all have different set points of this measurement. Sometimes there's a big difference between our heart rate when we breathe in and out. And sometimes the difference is small. And in very young babies, researchers have noticed that when there's a big difference and the set point is high, babies tend to have great attention, can focus for long periods of time on the things in their environment.
CONRADT: When you're presenting them with a new toy, they're going to really look at it and inspect it. But they also may be more irritable and fussy when parts of their environment are changing.
SPIEGEL: And in babies where the set point is low and there isn't much difference...
CONRADT: They might lose interest after a couple minutes, but they're also not going to be as fussy or irritable.
SPIEGEL: So this one valuable measurement, Conradt says, can tell you something about how the baby's nervous system responds to the world around it. Babies with high set points are sensitive babies when it comes to their environment. Babies with a low set points, not so much.
Which brings us back to the study. Conradt and her colleagues wanted to see if this simple measure, which is easy to get...
CONRADT: Something you can identify right away essentially, potentially even prenatally.
SPIEGEL: ...could be used to predict how children in poverty would do as they walked down their hard road. And so, a year after taking this first measurement, the same mothers and their children came back to the lab for two more tests. First, the children were evaluated for behavioral problems. The researchers asked the mothers questions about how often their toddlers were aggressive or anxious. And then the researchers turned to the babies to see how they actually behaved.
(SOUNDBITE OF BABY PLAYING)
SPIEGEL: This video is from the study. In it you see the mother and her toddler. They're in a strange room where the child has never been and the toddler is playing happily. Jeff Measelle, who co-authored the study, explains what happens next.
JEFF MEASELLE: At some point, the mom gets a signal from the researcher to leave the room. And for most babies when the mom leaves the room - because this is a strange weird place - the baby reacts.
SPIEGEL: You can see this on the video. For an instant there's a look of surprise as mom simply gets up and leaves without warning. The toddler's mouth falls open in disbelief and then come the tears.
(SOUNDBITE OF BABY CRYING)
SPIEGEL: But the part of the procedure that is most important to the researchers is what happens when the mother comes back.
MEASELLE: It's how that baby greets or responds to her mother when she comes back that gives us some picture, some clue of the kind of history that these two have had together.
SPIEGEL: If a toddler is easily soothed by the mother, researchers conclude that their attachment is strong and the environment the toddler has grown up in is relatively secure. But if the toddler doesn't seem comfortable with the mother and can't be soothed, the researchers conclude that the attachment is poorer and the environment the child is growing up in is probably unstable.
MEASELLE: It gives us some sense that that's probably the way in which those two have been interacting together over time.
SPIEGEL: Which finally brings us back to that original measure of breathing and heartbeats. The researchers found that the children who seemed less sensitive as infants ended up in the middle of the pack when it came to problem behaviors as toddlers. But kids who were sensitive as babies had two very different reactions to their worlds. If the baby had an insecure attachment to its mother, their behavior was deeply troubled - by far the worst. But if they had a secure attachment...
MEASELLE: Those were the kids who were doing the best, the absolute best of all the other babies in our sample at a year and a half. They had far and away the lowest reported problem behaviors.
SPIEGEL: In fact, the behavior of sensitive children with secure attachments compared favorably to the behavior of children whose environments were often much, much easier.
MEASELLE: These babies were looking a lot better behaviorally than a lot of babies growing up in middle-class and advantaged samples.
SPIEGEL: Better than a lot of babies growing up in middle-class and advantaged homes. So the researchers hope that this simple measure - breathing, heart beat - might one day be used to find sensitive children in poverty who need more stability and who prosper when they get it. They believe they found a biological marker which suggests that these children will be more sensitive to their environment, for better and for worse.
Alix Spiegel, NPR News, Washington.
(SOUNDBITE OF MUSIC)
CORNISH: This is NPR. Transcript provided by NPR, Copyright NPR.