Out of all the devastating effects of poverty, this one may be most devastating of all: Researchers have found that the brains of children raised in poor households have less surface area than the brains of wealthier children, which has a major impact on their development of language, memory and reasoning skills.

It is a finding with enormous consequences because it could explain so much of the outcomes in American society. As the nation sees a widening chasm between rich and poor, with more children sliding into poverty, the implications are monumental for the future of the nation and even the productivity of the economy. More than one out of every five children in America currently lives below the poverty line.

These findings are particularly powerful for African-American children. Though the researchers don’t separate out their results by race, they do posit some theories as to why the brains of poor children might fail to develop at the same rate: the children may experience more stress, live in more polluted areas, have less cognitive stimulation in their daily lives, be spoken to less and their mothers may have had poorer diets while pregnant.

Those all happen to be conditions researchers in the past have found are much more likely to exist in the lives of Black children, many of them directly attributable to racism. So what the findings suggest is that even if all children are born with the same potential, the same brain structure, once the vicious effects of racism and American capitalism are done with them, African-American children and poor children have had the basic biology of their brains altered.

Scientists found that the effects were the greatest among the poorest families, and even modest increases in wages had a significant impact on the structure of the child’s brain.

It is an accepted truism in education circles that the academic performance of poor children lags behind their wealthier counterparts, with the correlation between family income and child academic performance direct and strong. Now educators are closer to understanding why.

In conducting the study, which appeared in the journal Nature Neuroscience, researchers did MRI brain scans of 1,099 children age three to 20 years old in nine major cities. They studied every detail they could in the children’s lives — family income, family education, genetic lineage, age, etc. They found that the surface area of the children’s cerebral cortex tended to expand as family income rose; the surface area of the cerebral cortex was typically 6 percent larger in children from families with an income greater than $150,000, when compared to families earning $25,000 or less.

The education level of the parents had an effect on the children’s brains as well. Children from more educated families had a larger hippocampus, which plays a pivotal role in short term memory and spatial navigation.

But the relationship was greater between income and a child’s brain surface area. And remarkably, at the lowest income levels small increases in income made a big difference in brain surface area. The differences grew less pronounced as income levels grew, meaning the difference between children whose family income was $20,000 and $40,000 was much greater than the difference between children whose family income was $100,000 and $120,000.

“Families who have financial difficulties tend to have much more stress in their lives. Decisions need to be made on how to spend. Limited resources such as food and shelter might not always be guaranteed in those with the lowest incomes. So the quality of life for a family with an income of $50,000 might be much less stressful than a family with an income of $30,000,” Elizabeth Sowell, a senior author on the study and director of the developmental cognitive neuroimaging lab at Children’s Hospital, Los Angeles, told The Guardian.

Sowell wanted to stress this point: “The message is not ‘if you are poor, your brain will be smaller, and there is nothing that can be done about it.’ That is absolutely not the message. Improving access to resources that enrich the developmental environment could potentially change the trajectories of brain development for the better, even in children and adolescents in the age range we studied.”

In doing the research, the team divided families into groups based on income, ranging from less than $5,000 a year to more than $300,000 a year. The education levels of the parents ranged from less than seven years of schooling to advanced professional degrees such as PhD and MD.

In the journal, the researchers wrote that the differences in surface area were most prominent in the brain regions related to language, reading, executive functions and spatial skills. The researchers don’t yet know if the differences are permanent or can be changed if a family’s financial fortunes improve. To that end, they are starting a new study in which they give cash to low-income families to see if it makes a difference.

The team also is going to delve deeper into the reasons behind the differences they found. For instance, do better educated parents simply earn more, or do they interact with their children in different ways than less educated parents? Do richer parents perhaps buy more nutritious food for their children; are they able to stimulate them in superior ways, or does being able to relax and not worry about safety and day-to-day survival help brain development?