Poverty & the Brain



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

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

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.



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Tags: brain, causation, education, mike labossiere, poverty

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