Poverty & the BrainShare
A look at the possible causal connection between poverty and brain development
A key part of the American mythology is the belief that a person can rise to the pinnacle of success from the depths of poverty. While this does occur, most understand that poverty presents a considerable obstacle to success. In fact, the legendary tales that tell of such success typically embrace an interesting double vision of poverty: they praise the hero for overcoming the incredible obstacle of poverty while also asserting that anyone with gumption should be able to achieve this success.
Outside of myths and legends, it is a fact that poverty is difficult to overcome. There are, of course, the obvious challenges of poverty. For example, a person born into poverty will not have the same educational opportunities as the affluent. As another example, they will have less access to technology such as computers and high-speed internet. As a third example, there are the impacts of diet and health care—both necessities are expensive and the poor typically have less access to good food and good care. There is also recent research by scientists such as Kimberly G. Noble that suggests a link between poverty and brain development.
While the most direct way to study the impact of poverty and the brain is by imaging the brain, this (as researchers have noted) is expensive. However, the research that has been conducted shows a correlation between family income and the size of some surface areas of the cortex. For children whose families make under $50,000 per year, there is a strong correlation between income and the surface area of the cortex. While greater income is correlated with greater cortical surface area, the apparent impact is reduced once the income exceeds $50,000 a year. This suggests, but does not prove, that poverty has a negative impact on the development of the cortex and this impact is proportional to the degree of poverty.
Because of the cost of direct research on the brain, most research focuses on cognitive tests that indirectly test for the functionality of the brain. As might be expected, children from lower income families perform worse than their more affluent peers in their language skills, memory, self-control and focus. This performance disparity cuts across ethnicity and gender.
As would be expected, there are individuals who do not conform to the general correlation. That is, there are children from disadvantaged families who perform well on the tests and children from advantaged families who do poorly. As such, knowing the economic class of a child does not tell one what their individual capabilities are. However, there is a clear correlation when the matter is considered in terms of populations rather than single individuals. This is important to consider when assessing the impact of anecdotes of successful rising from poverty—as with all appeals to anecdotal evidence, they do not outweigh the bulk of statistical evidence.
To use an analogy, boys tend to be stronger than girls but knowing that Sally is a girl does not entail that one knows that Sally is weaker than Bob the boy. Sally might be much stronger than Bob. An anecdote about how Sally is stronger than Bob also does not show that girls are stronger than boys; it just shows that Sally is unusual in her strength. Likewise, if Sally lives in poverty but does exceptionally well on the cognitive tests and has a normal cortex, this does not prove that poverty does not have a negative impact on the brain. This leads to the obvious question about whether poverty is a causal factor in brain development.
Those with even passing familiarity with causal reasoning know that correlation is not causation. To infer that because there is a correlation between poverty and cognitive abilities that there must be a causal connection would be to fall victim to the most basic of causal fallacies. One possibility is that the correlation is a mere coincidence and there is no causal connection. Another possibility is that there is a third factor that is causing both—that is, poverty and the cognitive abilities are both effects.
There is also the possibility that the causal connection has been reversed. That is, it is not poverty that increases the chances a person has less cortical surface (and corresponding capabilities). Rather, it is having less cortical surface area that is a causal factor in poverty.
This view does have considerable appeal. As noted above, children in poverty tend to do worse on tests for language skills, memory, self-control and focus. These are the capabilities that are needed for success and it seems reasonable to think that people who were less capable would thus be less successful. To use an analogy, there is a clear correlation between running speed and success in track races. It is not, of course, losing races that makes a person slow. It is being slow that causes a person to lose races.
Despite the appeal of this interpretation of the data, to rush to the conclusion that it is the cognitive abilities that cause poverty would be as much a fallacy as rushing to the conclusion that poverty influences brain development. Both views do seem plausible and it is certainly possible that there is causation going in both directions. The challenge, then, is to sort the causation. The obvious approach is to conduct the controlled experiment suggested by Noble—providing the experimental group of low income families with an income supplement and providing the control group with a relatively tiny supplement. If the experiment is conducted properly and the sample size is large enough, the results would be statistically significant and provide an answer to the question of the causal connection.
Intuitively, it makes sense that an adequate family income would generally have a positive impact on the development of children. After all, this income would allow access to adequate food, care and education. It would also tend to have a positive impact on family conditions, such as emotional stress. This is not to say that throwing money at poverty is the cure; but reducing poverty is certainly a worthwhile goal regardless of its connection to brain development. If it does turn out that poverty does have a negative impact on development, then those who are concerned with the well-being of children should be motivated to combat poverty. It would also serve to undercut another American myth, that the poor are stuck in poverty simply because they are lazy. If poverty has the damaging impact on the brain it seems to have, then this would help explain why poverty is such a trap.