Expert Commentary

Child cognitive development and socioeconomic status: What do we know?

2015 study in Nature Neuroscience showing the relationship between a child's family income and parental education levels and the amount of brain surface area.

The “achievement gap” among American students has become a renewed area of focus, as compelling data underscore deep structural problems and the urgent need for targeted early interventions at younger ages. This gap is particularly stark along racial lines: The National Center for Education Statistics, part of the U.S. Department of Education, has studied outcomes for white and black students, as well as white-Hispanic students, and found large, persistent divisions, despite some progress in recent years. (Data tools are available for making state-level comparisons by race.)

A student’s race is typically highly correlated with family income. The quality of, and availability, of early childhood education continues to vary widely in the United States, and there remain large inequities in the funding of public elementary schools. Although there is an “extended sensitive period for intellectual development” and IQ into early adolescence, neuroscience suggests that, tragically, children whose families have fewer resources can begin their schooling with a much greater need to catch up in terms of brain growth. The precise reasons for this have yet to be pinpointed — Is it added stress for low-income youth? Less access to healthful foods and resources? Language exposure? Or something else? — but the underlying science has begun to solidify in recent years, stirring further interest from policymakers.

A 2015 study from Harvard and MIT performed brain imaging on a group of 12- and 13-year-olds, and found those from lower-income families had thinner brain cortex around key intellectual areas. Further, a 2015 study published in Nature Neuroscience, “Family Income, Parental Education and Brain Structure in Children and Adolescents,” analyzed brain surface area — a measure different than cortical thickness — of 1,099 persons from ages 3 to 20 and correlated that with socioeconomic status, representing the largest study of its kind to date. More than two dozen researchers, led by Kimberly G. Noble of Columbia University, performed brain imaging and looked at relationships with household income levels, as well as education levels of the subjects’ parents.

The study’s findings include:

  • Parental education was “significantly associated” with brain surface area independent of age, scanner, sex and genetic ancestry (race). The data suggest that “any increase in paren­tal education, whether an extra year of high school or college, was associated with a similar increase in surface area over the course of childhood and adolescence.”
  • Family income was associated with greater brain surface area, and the relationship was even more substantial for lower-income children: “For every dollar in increased income, the increase in children’s brain surface area was proportionally greater at the lower end of the family-income spec­trum.”
  • Strong conclusions about causes cannot be drawn from the data: “It is unclear what is driving the links between SES and brain structure. Such associations could stem from ongoing disparities in postnatal experience or exposures, such as family stress, cognitive stimulation, environmental toxins or nutrition, or from corresponding differences in the prenatal environment.”
  • Further, the “results should in no way imply that a child’s socioeconomic circumstances lead to an immutable trajectory of cog­nitive or brain development. Many other factors account for variance in brain morphometry; indeed, our data show marked variability in brain structure at all SES levels, including among the most disad­vantaged children.”

“If this correla­tional evidence reflects a possible underlying causal relationship, then policies targeting families at the low end of the income distribution may be most likely to lead to observable differences in children’s brain and cognitive development,” the researchers conclude.


Keywords: Youth, children, education, income disparity, poverty, parenting

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