The Working Poor (37 page)

The hollow sensation of hunger alone interferes with childhood learning. As anyone who has been without adequate food for more than a couple of days can attest, it narrows the focus of attention. Lethargic, light-headed, then intensely obsessive, the hungry person filters out the irrelevant. I experienced this myself when the navy sent me to a survival school run by the marines. After a few days scavenging for food in the woods, I began to slow down and think about little else—not politics, not literature, not even the interesting idiosyncrasies of my survival-class teammates. The only thing about them that mattered was whether they were facilitating or impeding my ability to acquire food. I certainly had no interest in reading a book. Teachers see it in their classrooms, where ill-fed children cannot concentrate. At Dunbar High School in Washington, D.C., an English teacher kept a supply of granola bars so he could toss them to hungry students. “Learning is discretionary,” said Dr. Frank, “after you’re well-fed, warm, secure.”

The syndrome is not easily broken. “Malnutrition impairs certain very important parts of your immune system,” the doctor explained. “Besides making your barrier—things like your mucous membranes and your skin—more penetrable, it also interferes with what’s called your cellmediated immunity, which is the immunity that fights viruses … and also your secretory … immunoglobulin that lines your respiratory tract and
your GI tract.… And the way the story works is as follows: When anybody’s kid in any kind of family gets sick—a little kid—they lose weight. They feel yucky they throw up, they have diarrhea, they have fever, and fever raises your metabolic rate and you use more calories. And anybody’s kid from a perfectly ordinary childhood illness—you know, ear infection, prevailing stomach crud, whatever’s going around—can lose a pound or two. But in my house or your house, when the kid gets over the prevailing crud or the ear infection or whatever, they get very hungry and they eat extra. You feed them second and third helpings on everything. Within a few days they’re back to baseline, and their immune function’s also back to baseline.

“In the families we serve, once the kid gets any kind of a deficit (and it doesn’t have to be from a rare illness, just from normal childhood, whatever’s going around) … there isn’t anything extra.” This happens especially toward the end of the month when the food money runs out, or during vacations when there are no school lunches. “So that the deficit gets established and doesn’t get repleted. And then the baby—or the child or anybody—is more susceptible to the next infection, which then drives him still further down. What generally kills malnourished kids in the Third World … is infections. Things like measles are absolutely lethal in malnourished kids.”

The incidence of malnutrition in the United States is difficult to measure. The Census Bureau conducts an annual telephone survey of “food insecurity” for the Department of Agriculture, but it depends on subjective self-reporting and misses families who are too poor to have phones. Dr. Frank thinks it understates the problem. Extrapolating from a sample of 50,000 families, the study found 5.4 percent, or 6.4 million of the country’s households, with at least one member who had been hungry at some point during the year 2010. They were part of a larger population of 17.2 million households (14.5 percent of the country’s total) who were deemed “food insecure” because they reported themselves as having been uncertain that they could afford enough to eat.
¹
Surveying food’s insufficient quantity, rather than its quality, may leave uncounted a larger number of families who would not label themselves “food insecure” but have children lacking nutrients vital to healthy brain development. The worsening problem of obesity illustrates the point that a lot of the wrong food is not helpful.

As scientific understanding of the brain has progressed in recent
decades, so has the chronicle of damage done by malnutrition. Inadequate iron is a critical example. Sobering studies have found that children who suffer from severe iron deficiency in infancy don’t catch up in brain function, even once the iron deficiency is eliminated. In adolescence, they still score lower “in arithmetic achievement and written expression, motor functioning, and some specific cognitive processes such as spatial memory and selective recall;” teachers also see them displaying “more anxiety or depression, social problems, and attention problems,” according to a lengthy National Academy of Sciences report,
From Neurons to Neighborhoods,
which compiles research on child development. Iron is necessary in many features of brain development, including growth of the brain in size and the creation of the myelin sheath (the fatty, insulating envelope around nerve fibers), which facilitates the transmission of impulses among neurons, the brain’s impulse-conducting cells. The most sensitive periods of brain growth come during the last trimester of pregnancy and the first two years after birth, so the timing of nutritional deficiency can determine what mental capabilities are damaged. Insufficient nutrition even earlier, during the second trimester, can reduce the creation of neurons. Malnutrition in the third trimester retards their maturation and inhibits the production of branched cells called glia.
²

Premature birth can be a “biological insult” to the brain, with disproportional impact on black and poor mothers and children. Some scientists see a genetic link with prematurity. Others note that racial disparities in maternal health—including inferior medical care, nutritional deficits, and untreated vaginal infections—seem primarily responsible for a higher incidence of prematurity among black than white women, and a consequent rate of infant mortality among blacks that is 2.4 times that of whites.
³
While advances in neonatal intensive care have increased the survival rate of premature underweight infants, other severe results can impose lifetime handicaps, including blindness, deafness, and cognitive impairment. Among the dangers faced by such babies are brain hemorrhages, inadequate glucose in the blood, and the denial of certain intrauterine nutrients and acids crucial for brain growth.
⁴
“Infants born at very low birth weight appear to account for approximately one-third of children with cerebral palsy and 10 percent of those with mental retardation,” write Drs. Barry Zuckerman and Robert Kahn.
⁵
Even minor brain hemorrhages that do not cause retardation place children “at higher risk of minor handicaps (e.g., behavior
problems, attention problems, memory deficits),”
From Neurons to Neighborhoods
reports. “Emerging data strongly suggest that the human brain continues to develop in a unique way in utero until the end of gestation and that early termination of pregnancy disrupts that development with subsequent behavioral consequences.” Some researchers have found that toddlers who were premature babies “cannot be assumed to have caught up with their full-term counterparts in all aspects of cognitive development.”
⁶

My Sunday school teacher, who was also a professor of philosophy, once pointed to a lamp and asked the class what we thought that lamp was least capable of doing. We came up with a few obvious answers: walk, talk, change its own light bulb. But he was looking for something else. There was no way, he told us, that the lamp could ever understand how it worked. He let us ponder that for a moment, and then continued: Nor could we human beings understand how we worked, not entirely. The mind and all its wonders were beyond our thorough comprehension, he said, and would probably be so forever.

That was more than forty years ago, long before the high-tech instruments that now observe the brain with magnetic resonance imaging (MRI) and positron emission tomography (PET). Using those tools and many others, mushrooming neurobiological and behavioral research has made significant discoveries by testing humans and experimenting on the brains of monkeys and mice. My Sunday school teacher would still be mostly right: The human brain remains a vast frontier, largely uncharted. But the newfound knowledge has also created a new discussion, one with solemn implications for the poor. The difficult conditions in which lower-income people live, their vulnerability to disease and stress, are now seen as affecting the brain itself. Many scientists and other researchers from various disciplines no longer recognize rigid boundaries between biology and experience, and between the genetic and the environmental. The dichotomies are mostly gone, replaced by a holistic concept of mental and emotional development guided by the interaction between “nature and nurture,” in the words of Jack Shonkoff, a pediatrician and dean of the Heller School for Social Policy and Management at Brandeis. “You’ve had behavioral scientists talk about what a powerful determinant experience is, environment is, on outcomes,” he said. “Now what you have is molecular biologists saying: No gene operates independently of the influence of the
environment…. that if it’s the genes, it’s not immutable. It’s a predisposition. It has to then interact with the environment.”

In this view, the elements of life are tied in an intricate web. No matter how unrelated they seem from one another, none can be dramatically altered without tugging on strands across a distance. Eating and learning, housing and health, a mother’s early nurturing and a child’s later brain function are connected. Advancing research into the science of children’s intellectual and behavioral growth is mapping this web, sometimes with the microscopic detail of laboratory work, sometimes with the bold strokes of systematic observation. Many findings are accompanied by cautionary notes. Because humans cannot ethically be subjected to experimentation involving trauma or deprivation, “a lot of what we say we’ve learned from brain research comes from nonhuman animal studies—rodents and primates,” Dr. Shonkoff noted. “We can infer, but we can’t say that’s the same thing as studying [human] brain development. Human brains are different from rat brains and even rhesus monkeys.”

Nevertheless, the biological development of the human brain is now understood partly as a function of early learning experiences. The number of synapses (junctions across which nerve impulses pass) increases from about 50 trillion at birth to a peak of one quadrillion at age three, then is halved by age fifteen. Such “pruning” is part of a natural process that some scientists call “use it or lose it.” Crudely put, it may mean that tasks or functions not performed are deemed unnecessary, and the brain adapts accordingly. In the first couple of years, for example, the brain can recognize any sound in any language; after exposure to a particular language for a few years, the brain loses the ability to perceive sounds that are not heard and used. “Thus, the child’s experience, like a sculptor carving a complex statue from a large block of stone, shapes the child’s brain,” write Drs. Zuckerman and Kahn. “But such ‘plasticity’ of the neural networks does not last forever.”
⁷
It is not a perfect metaphor because the brain is not carved in stone, of course, and its capacities continue developing well past adolescence. But early interactions can teach lifetime lessons.

Take a two-month-old infant who cries at 3 a.m. Drs. Zuckerman and Kahn offer two scenarios. John’s mother picks him up, “cradles him next to her body, then talks to him about being hungry. John nurses for about a half-hour, pausing occasionally to gaze up into the eyes of his mother, who responds by speaking softly to her son … puts John in the crib, kisses him, and covers him as he slowly begins to drift off to sleep.” The baby “is learning
about cause and effect,” the doctors note, “that the adults in his life are trustworthy and can be counted on to help him if he is frustrated or in need.”

Another two-month-old, Sean, gets different treatment. His mother “has just fallen asleep after a fight with her husband. She has difficulty getting out of bed and shouts, ‘Just a minute, just a minute. I’m coming.’ … She lifts him up abruptly and puts him to her breast. She stares fixedly ahead, going over the recent fight with her husband.… Sean responds to his mother’s tension by squirming restlessly, stiffening, and finally arching and drawing back from her nipple to cry. The mother responds, ‘You don’t want to eat, fine, don’t eat.’ She puts her somewhat hungry baby back into the crib and goes back to bed yelling, ‘Shut up, just shut up.’ ” What Sean is learning, Drs. Zuckerman and Kahn observe, is that “to be handled and held can be uncomfortable and distressing, and that being hungry and crying only leads to a harsh tone, rough handling, and partially met needs. He is learning to be wary and distrustful of others. Even learning about cause and effect is tainted for Sean because of the negative affect. John, by contrast, may develop a love of learning because the brain circuitry connects cause and effect to pleasure.”
⁸

There is reciprocity here: The mother is also learning that her baby is not cuddly and malleable, and she becomes less warm as a result; child behavior and parenting styles influence each other. Children with a sense of “secure attachment” induce better parenting, according to research summarized by the study
From Neurons to Neighborhoods:
“The children, in effect, are more receptive to the parent’s instruction, guidance, and teaching, which then reinforces the parent’s sensitive parenting and, in all likelihood, further binds their secure attachment.”
⁹
Maternal depression can be part of the same cycle: The mother doesn’t nurture, the child doesn’t respond, and that worsens the mother’s depression. “Depressed mothers have been shown to display less spontaneity, more unhappy affect, fewer vocalizations, and diminished physical contact with their four-month-olds,” write Dr. Steven Parker and colleagues in a 1988 paper. “These infants already manifest fewer vocalizations and happy expressions toward their mothers.”
¹⁰
Children’s cognitive outcomes can also be affected, according to some studies, one of which found reduced reading skills among eight-year-olds who were three when their mothers suffered from depression.
¹¹

The specific biology of such mechanisms is still poorly understood, but sketches are being drawn, based mostly on animal research into neurochemical
changes induced by fear and anxiety. One line of investigation has focused on cortisol, a steroid hormone that is elevated by danger or stress. It is one of multiple “chemical messengers” that affect brain function through receptors in nerve cells and elsewhere. Cortisol “helps to break down protein stores, liberating energy for use by the body,”
Neurons
explains, “suppresses the immune system, suppresses physical growth … and affects many aspects of brain functioning, including emotions and memory.”