The Effects of Low SES on Brain Development
It has long been known that children from homes at the lower end of the Socioeconomic spectrum do more poorly on intelligence and achievement tests than well off children. These less fortunate children also tend to do more poorly in school, have increased learning and behavioral disorders, and increased drop out rates. A great deal of effort has been directed toward understanding these differences, and mounting evidence points squarely at the effects of environmental deprivation. You might think that this conclusion is a “no brainer,” but, for some time, it has not been so clear. Some researchers have found evidence to implicate genetic factors for these differences. Over the last several years more conclusive evidence is pointing at environmental rather than genetic determinates.
Last week I discussed some ground breaking evidence from behavioral geneticists that asserted that environmental determinates play a crucial role in mental ability scores, but only for Low Socioeconomic Status (LSES) children. I noted that “For [LSES] children, the environment remains the key variable associated with differences in mental ability. Perhaps as much of 70% of the variance in mental ability is attributable to the shared home environment. While for [High SES (HSES)] children, genes become the predominant variable associated with the differences in mental ability scores. Environment still plays a role but much less so. Smart parents have smart kids unhampered by environmental constraints.”
Questions have persisted for quite some time as to what factors influence these differences. Research to date has implicated variables like parental attention, number of words spoken in the home, access to books, and familial stressors; however, the actual physiological or anatomical mechanisms (e.g., neurocognitive processes) that result in these discrepancies have remained elusive. You see, many factors have been found to correlate with the underachievement of LSES children, but not until a study by UC Berkley Neuroscientists, did we have conclusive direct evidence of how these factors may actually produce neurological differences that play out in these cognitive, achievement, and behavioral gaps.
Scientists at UC Berkeley’s Helen Wills Neuroscience Institute and School of Public Health report in a study published in the Journal of Cognitive Neuroscience that typically developing nine- and ten-year-olds who only differ in terms of SES, have detectable differences in prefrontal cortext responsiveness. The prefrontal cortex is the part of the brain that is known to be involved in problem solving and creativity.
In a press release about this study it was noted (Sanders, 2008):
Brain function was measured by means of an electroencephalograph (EEG) – basically, a cap fitted with electrodes to measure electrical activity in the brain – like that used to assess epilepsy, sleep disorders and brain tumors.
“Kids from lower socioeconomic levels show brain physiology patterns similar to someone who actually had damage in the frontal lobe as an adult,” said Robert Knight, director of the institute and a UC Berkeley professor of psychology. “We found that kids are more likely to have a low response if they have low socioeconomic status, though not everyone who is poor has low frontal lobe response.”
Previous studies have shown a possible link between frontal lobe function and behavioral differences in children from low and high socioeconomic levels, but according to cognitive psychologist Mark Kishiyama, first author of the new paper, “those studies were only indirect measures of brain function and could not disentangle the effects of intelligence, language proficiency and other factors that tend to be associated with low socioeconomic status. Our study is the first with direct measure of brain activity where there is no issue of task complexity.”
Co-author W. Thomas Boyce, UC Berkeley professor emeritus of public health who currently is the British Columbia Leadership Chair of Child Development at the University of British Columbia (UBC), is not surprised by the results. “We know kids growing up in resource-poor environments have more trouble with the kinds of behavioral control that the prefrontal cortex is involved in regulating. But the fact that we see functional differences in prefrontal cortex response in lower socioeconomic status kids is definitive.”
These scientists suspect that “stressful environments” and “cognitive impoverishment” are responsible because in previous research on animals, these very factors have been shown to affect development of the prefrontal cortex. “UC Berkeley’s Marian Diamond, professor of integrative biology, showed nearly 20 years ago in rats that enrichment thickens the cerebral cortex as it improves test performance. And as Boyce noted, previous studies have shown that children from poor families hear 30 million fewer words by the time they are four than do kids from middle-class families.”
These factors lead to important differences in brain functioning. As the lead author noted in an interview: “Those from low socioeconomic environments showed a lower response to the unexpected novel stimuli in the prefrontal cortex that was similar to the response of people who have had a portion of their frontal lobe destroyed by a stroke.” (Sanders, 2008)
One question that arose in my mind as I reviewed this paper was whether something other than SES was responsible for this effect. I asked Dr. Robert Knight this question:
“The HSES and LSES kids differed in both prefrontal cortex response level and standard scores on intelligence test subtests [Intelligence data was also collected as part of the study. On multiple incidences LSES children obtained significantly lower subtest scores than HSES children.] Is it not possible that genetic traits (i.e., lower IQ) might be responsible for the lower prefrontal cortex activity level, not SES?“
Dr. Knight referred this question to the led author, Dr. Mark Kishiyama, who responded in personal correspondence:
“This study was designed to reveal the effects of poverty on brain function rather than to identify specific causes. While we cannot rule out the potential effects of genetic factors, on the basis of prior evidence, we proposed that the primary influences were environmental (e.g., stress and a cognitively impoverished environment). There is considerable evidence in both human and animal studies indicating that stress and environmental factors can contribute to disruptions in brain development. In addition, we believe that these effects can be reversed with early childhood interventions (see also Raizada & Kishiyama, 2010).“
The implications of these findings are profoundly important and grim. If we accept these results and do nothing, then we all are complicit in perpetuating the cycle of poverty. We know that there are important differences in how LSES and HSES children are raised. Education, training, and intervention programs must focus on narrowing this gap. I contend that parent education programs like Baby College administered by the Harlem Children’s Zone must must be closely examined and if shown to be effective, replicated on a broad scale. I also contend that programs like Early Head Start and Head Start should focus their efforts on proven strategies that close these gaps. This is essential in order to build a just society whereby we all get a more fair shot at rising up and contributing fully to society.
Kishiyama, M. M., Boyce, W. T., Jimenez, A. M., Perry, L. M., and Knight, R. T. (2009). Socioeconomic Disparities Affect Prefrontal Function in Children. Journal of Cognitive Neuroscience. 21:6, 1106-1115.
Sanders, R. (2008). EEGs show brain differences between poor and rich kids. UC Berkley Press Release.
Tucker-Drob, E. M., Rhemtulla, M., Harden, K. P., Turkheimer, E., & Fask, D. (2011). Emergence of a Gene × Socioeconomic Status Interaction on Infant Mental Ability Between 10 Months and 2 Years. Psychological Science. 22(1) 125–133.