Brains, Schools and a Vicious Cycle of Poverty
Research spotlights the grim effect of poverty on education
A fifth or more of American children grow up in poverty, with the situation worsening since 2000, according to census data. At the same time, as education researcher Sean Reardon has pointed out, an “income achievement gap” is widening: Low-income children do much worse in school than higher-income children.
Since education plays an ever bigger role in how much we earn, a cycle of poverty is trapping more American children. It’s hard to think of a more important project than understanding how this cycle works and trying to end it.
Neuroscience can contribute to this project. In a new study in Psychological Science, John Gabrieli at the Massachusetts Institute of Technology and his colleagues used imaging techniques to measure the brains of 58 14-year-old public school students. Twenty-three of the children qualified for free or reduced-price lunch; the other 35 were middle-class.
The scientists found consistent brain differences between the two groups. The researchers measured the thickness of the cortex—the brain’s outer layer—in different brain areas. The low-income children had developed thinner cortices than the high-income children.
The low-income group had more ethnic and racial minorities, but statistical analyses showed that ethnicity and race were not associated with brain thickness, although income was. Children with thinner cortices also tended to do worse on standardized tests than those with thicker ones. This was true for high-income as well as low-income children.
Of course, just finding brain differences doesn’t tell us much. By definition, something about the brains of the children must be different, since their behavior on the tests varies so much. But finding this particular brain difference at least suggests some answers.
The brain is the most complex system on the planet, and brain development involves an equally complex web of interactions between genes and the physical, social and intellectual environment. We still have much to learn.
But we do know that the brain is, as neuroscientists say, plastic. The process of evolution has designed brains to be shaped by the outside world. That’s the whole point of having one. Two complementary processes play an especially important role in this shaping. In one process, what neuroscientists call “proliferation,” the brain makes many new connections between neurons. In the other process, “pruning,” some existing connections get stronger, while others disappear. Experience heavily influences both proliferation and pruning.
Early in development, proliferation prevails. Young children make many more new connections than adults do. Later in development, pruning grows in importance. Humans shift from a young brain that is flexible and good at learning, to an older brain that is more effective and efficient, but more rigid. A change in the thickness of the cortex seems to reflect this developmental shift. While in childhood the cortex gradually thickens, in adolescence this process is reversed and the cortex gets thinner, probably because of pruning.
We don’t know whether the low-income 14-year-olds in this study failed to grow thicker brains as children, or whether they shifted to thinner brains more quickly in adolescence.
There are also many differences in the experiences of low-income and high-income children, aside from income itself—differences in nutrition, stress, learning opportunities, family structure and many more. We don’t know which of these differences led to the differences in cortical thickness.
But we can find some hints from animal studies. Rats raised in enriched environments, with lots of things to explore and opportunities to learn, develop more neural connections. Rats subjected to stress develop fewer connections. Some evidence exists that stress also makes animals grow up too quickly, even physically, with generally bad effects. And nutrition influences brain development in all animals.
The important point, and the good news, is that brain plasticity never ends. Brains can be changed throughout life, and we never entirely lose the ability to learn and change. But, equally importantly, childhood is the time of the greatest opportunity, and the greatest risk. We lose the potential of millions of young American brains every day.
