New research shows that low-income kids may be lagging behind their peers because a crucial part of their brains is underdeveloped.

Researchers from MIT’s McGovern Institute for Brain Research compared the brains of affluent 12- and 13-year-olds to the brains of less affluent peers. They found that one particular area of the brain — the neocortex, which plays a key role in memory and learning ability — is thinner in children from lower-income households.

This is an important part of the brain for young students, who are often tested based on their ability to recall large chunks of information. Children who had a thinner neocortex performed poorly on standardized tests, researchers found.

More than 90% of high-income students scored above average on a statewide math and English/Language Arts standardized test, compared to less than 60% of low-income students. Differences in cortical thickness could account for almost half of the income-achievement gap in this sample, researchers wrote, mostly because the neocortex plays such a crucial role in performance on math and language arts exams.

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“Just as you would expect, there’s a real cost to not living in a supportive environment. We can see it not only in test scores, in educational attainment, but within the brains of these children,” says psychological scientist John Gabrieli, a professor of brain and cognitive sciences at MIT and one of the study’s authors.

Differences in how children succeed academically have long been studied, but mostly through the lens of racial impact. Since a 2011 study published by Stanford University professor Sean Reardon found that the gap between standardized test scores of affluent and low-income students has grown by about 40% since the 1960s, there’s been a lot more research aimed at finding links between income and achievement, rather than race alone. The MIT study found low-income children were equally likely to have a thinner neocortex, no matter their race.

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Gabrieli and his co-authors can’t say exactly why poor children’s brains develop differently because there are too many possibilities to count. Everything from nutrition, health care, early education, stress levels, and quality of schools can impact a child’s learning ability and brain development.

Their findings do, however, underline the importance of early intervention to ensure that low-income kids get the tools they need to succeed.

“We know a lot from research and with certainty that the brain is highly plastic at all ages,” he says. “This is all the more reason to promote things in schools and within communities that will nurture these brains. And maybe [brain scans] can give you some way to monitor whether programs that are meant to support children are making those differences rather than waiting many years for those outcomes.”

The MIT study comes a few weeks after a similar one by Stanford University researchers found that children from low-income backgrounds tend to have smaller brains, overall, than their wealthier peers. The brain of a child whose family earns less than $25,000 annually is 6% smaller in surface area than a child whose parents earned more than $150,000, according to the study, published in Nature Neuroscience.

The MIT study, “Neuroanatomical Correlates of the Income-Achievement Gap,” is published in the Association for Psychological Science.

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