emotions that always seemed on the verge of capsizing her. “Sometimes the stress is just too much for me to bear,” she told me one day. “I don’t see how people deal with it.”
For Monisha, the main effect of stress overload on her prefrontal cortex was that she had a hard time regulating her emotions. For many other young people, though, the main effect of stress is that it compromises their ability to regulate their thoughts. This has to do with a particular set of cognitive skills located in the prefrontal cortex known as executive functions. In wealthy school districts,
Executive functions, as we now understand them, are a collection of higher-order mental abilities; Jack Shonkoff, the head of the Center on the Developing Child at Harvard University, has compared them to a team of air traffic controllers overseeing the functions of the brain. Most broadly, they refer to the ability to deal with confusing and unpredictable situations and information. One famous test of executive-function ability is called the Stroop test. You see the word
7. Simon
For a while now, we’ve known that executive-function ability correlates strongly with family income, but until recently, we didn’t know why. Then in 2009, two researchers at Cornell University, Gary Evans and Michelle Schamberg, designed an experiment that for the first time gave us a clear look at exactly how childhood poverty affects executive function. The particular executive-function skill they examined was working memory, which refers to the ability to keep a bunch of facts in your head at the same time. It’s quite distinct from long-term memory— working memory is not about remembering the name of your first-grade teacher; it’s about remembering everything you’re supposed to pick up at the supermarket. The tool that Evans and Schamberg selected to measure working memory was a kitschy one: the electronic children’s game Simon. If you grew up in the 1970s, as I did, you might remember this Hasbro game: it’s a UFO-looking disk about the size of an LP record but fatter, with four panels that light up and make distinct sounds. The panels illuminate in various sequential patterns, and you have to remember the order of the beeps and the flashes.
Evans and Schamberg used Simon to test the working memory of 195 seventeen-year-olds in rural upstate New York, all part of a group that Evans had been studying since they were born. About half the children had grown up below the poverty line and the other half in working- and middle-class families. Evans and Schamberg’s first discovery was that the amount of time that children spent in poverty when they were growing up predicted how well they would do on the Simon test, on average—kids who had spent ten years in poverty, in other words, did worse than kids who had spent just five years in poverty. This, on its own, was not too surprising; researchers had previously found correlations between poverty and working memory.
But then Evans and Schamberg did something new: They introduced some biological measures of stress. When the children in the study were nine years old, and again when they were thirteen, Evans’s researchers took a number of physiological readings from each child, including blood pressure, body mass index, and levels of certain stress hormones, including cortisol. Evans and Schamberg combined those biological data to create their own measure of allostatic load: the physical effects of having an overtaxed stress-response system. When they sat down with all the data and compared each child’s Simon score, poverty history, and allostatic-load reading, they found that the three measures correlated—more time in poverty meant higher allostatic-load numbers and lower scores on Simon. But then came the surprise: When they used statistical techniques to factor out the effect of allostatic load, the poverty effect disappeared completely. It wasn’t poverty itself that was compromising the executive- function abilities of the poor kids. It was the stress that went along with it.
This was, potentially at least, a big deal in terms of our understanding of poverty. Picture two boys sitting together playing Simon for the first time. One is from an upper-middle-class home, and one is from a low-income home. The kid from the upper-middle-class home is doing a lot better at memorizing the patterns. We might be inclined to assume that the reason for this effect is genetic—maybe there’s a Simon gene that rich kids are more likely to possess. Or maybe it has to do with material advantages in the upper-middle-class kid’s home—more books, more games, more electronic toys. Or maybe his school is a better place to learn short-term memory skills. Or perhaps it’s some combination of the three. But what Evans and Schamberg found is that the more significant disadvantage the low-income boy faces is in fact his elevated allostatic load. And if another low-income boy came along with low levels of allostatic load—if, for whatever reason, he had had a less stressful childhood, despite his family’s poverty—he would in all probability do just as well at the Simon competition as the rich kid. And why does a low Simon score matter? Because in high school, college, and the workplace, life is filled with tasks where working memory is crucial to success.
The reason that researchers who care about the gap between rich and poor are so excited about executive functions is that these skills are not only highly predictive of success; they are also quite malleable, much more so than other cognitive skills. The prefrontal cortex is more responsive to intervention than other parts of the brain, and it stays flexible well into adolescence and early adulthood. So if we can improve a child’s environment in the specific ways that lead to better executive functioning, we can increase his prospects for success in a particularly efficient way.
8. Mush
It is in early childhood that our brains and bodies are most sensitive to the effects of stress and trauma. But it is in adolescence that the damage that stress inflicts on us can lead to the most serious and long-lasting problems. Partly, that’s just a practical fact of growing up. When you have trouble controlling your impulses in elementary school, the consequences are relatively limited: you might get sent to the principal’s office; you might alienate a friend. But the kind of impulsive decisions you are tempted to make in adolescence—driving drunk, having unprotected sex, dropping out of high school, stealing a wallet—can often have lifelong consequences.
What’s more, researchers have found that there is something uniquely out of balance about the adolescent brain that makes it especially susceptible to bad and impulsive decisions. Laurence Steinberg, a psychologist at Temple University, has analyzed two separate neurological systems that develop in childhood and early adulthood that together have a profound effect on the lives of adolescents. The problem is, these two systems are not well aligned. The first, called the incentive processing system, makes you more sensation seeking, more emotionally reactive, more attentive to social information. (If you’ve ever been a teenager, this may sound familiar.) The second, called the cognitive control system, allows you to regulate all those urges. The reason the teenage years have always been such a perilous time, Steinberg says, is that the incentive processing system reaches its full power in early adolescence while the cognitive control system doesn’t finish maturing until you’re in your twenties. So for a few wild years, we are all madly processing incentives without a corresponding control system to keep our behavior in check. And if you combine that standard-issue whacked-out adolescent neurochemistry with an
