It has been long established that IQ and poverty are negatively related. In a recently study published in the journal Nature Neuroscience, Kimberly Noble (of Columbia), and Elizabeth Sowell (of Children’s Hospital in Los Angeles) imaged the brains of 1,099 children and young adults between the ages of 3 and 20 across the US and mapped the results in terms of volume of the brain to parental income brackets. Controlling for a number of confounding factors including parental education, the authors founds that the brain surfaces associated with language, memory, and executive function, were 6% larger for the children who were born to parents earning more than USD150,000 annually, relative to children whose parents earned less than USD25,000 annually. The areas of the brain that were imaged are all known to be critical to academic success. The authors also found that children from lower income families also performed more poorly on a battery of cognitive tests.
This result is consistent with a body of prior research that linked brain size (as measured by MRI scan) and cognitive ability (Luder et. al, 2008 and McDaniel 2005). In particular, McDaniels’ research paper was a meta analysis covering 37 studies and found a correlation coefficient of 0.33 between brain volume and IQ score.
But Noble and Sowell’s findings are also in line with a recent unpublished study by Martha Farah (or the University of Pennsylvania) who scanned the brains of 44 1-month old babies from African American families and found that brain sizes were also smaller than wealthier controls. Poverty and brain size are therefore negatively related variables. We know that brain size and IQ are positively related variables, which means that IQ and poverty are also negatively correlated.
The two studies were empirical in nature in that neither could advance a definitive explanation for the results, although the authors suggested that nutrition, environmental stress factors (including during the pregnancy), and a lack of resources could in fact be partly responsible for the results.
Noble and Sowell aim to go on to see whether they can replicate the results of a Mexican study by Fernald et al. (2005) in which parental incomes of poor families were supplemented to find that the cognitive abilities of children were improved within an 18 month period. An ability to replicate Fernald’s study results would be a victory for policy makers, and would no doubt, if used as a policy tool, garner the political support of nations.
IQ and poverty: what about genetics?
This set of studies is particularly interesting as neither of the authors have discuss genetic influences as possible explanatory factors for the results. Charles Murray expressed his surprise in this regard, citing that the genetic evidence presented in the Bell Curve could not be ignored when interpreting the results of this study.
A large number of recent studies have found that IQ in inheritable, with genetics found to account for a greater proportion of the variance in IQ scores relative to environmental factors. Again, the relative influence of genetics to environment is roughly 2:1. On this basis, it is somewhat surprising that Noble and Sowell would have ignored this aspect of the literature in discussing the results; although a culture does seem to be emerging in academia whereby unflattering results that are not politically correct are immediately branded as controversial and spark outcry.
The link between IQ and income is a well established one, as is the link between different professions and average IQ levels. It therefore comes as no surprise that people with higher average IQs will be able to achieve higher levels of education, which in turn will lead to a greater propensity to be in a professional job, and therefore the potential to earn a higher level of income. Professionals mating with professionals (or at the very least, university graduates getting together with other graduates) will lead to higher average IQ of offspring, which most probably perpetuates the IQ gap vs. poorer cohorts.
What is interesting with this new study is that it reveals that not only do offspring from poorer families have lower IQs, but they also have smaller brain volumes. This latter finding again would appear to reinforce the heritability of intelligence line of argumentation.
Income per se cannot be responsible for the results. Greater income does in fact offer parental scope to foster better learning environments, but alas, improving learning environments will only ever achieve so much, as genetic differences are unlikely to be able to be overcome through environmental engineering. As a society, we must work towards ensuring equal opportunity, whilst recognising that such equal opportunity is only likely to lead to unequal outcomes.
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