December 17, 2013

Poverty directly damages brain development

Children that at early ages have similar or even greater gray matter than their wealthier peers, get stuck in a weaker development as they grow just for being poor. That is what a new study has found:

Jamie L. Hanson et al., Family Poverty Affects the Rate of Human Infant Brain Growth. PLoS ONE 2013. Open access → LINK [doi:10.1371/journal.pone.0080954]


Living in poverty places children at very high risk for problems across a variety of domains, including schooling, behavioral regulation, and health. Aspects of cognitive functioning, such as information processing, may underlie these kinds of problems. How might poverty affect the brain functions underlying these cognitive processes? Here, we address this question by observing and analyzing repeated measures of brain development of young children between five months and four years of age from economically diverse backgrounds (n = 77). In doing so, we have the opportunity to observe changes in brain growth as children begin to experience the effects of poverty. These children underwent MRI scanning, with subjects completing between 1 and 7 scans longitudinally. Two hundred and three MRI scans were divided into different tissue types using a novel image processing algorithm specifically designed to analyze brain data from young infants. Total gray, white, and cerebral (summation of total gray and white matter) volumes were examined along with volumes of the frontal, parietal, temporal, and occipital lobes. Infants from low-income families had lower volumes of gray matter, tissue critical for processing of information and execution of actions. These differences were found for both the frontal and parietal lobes. No differences were detected in white matter, temporal lobe volumes, or occipital lobe volumes. In addition, differences in brain growth were found to vary with socioeconomic status (SES), with children from lower-income households having slower trajectories of growth during infancy and early childhood. Volumetric differences were associated with the emergence of disruptive behavioral problems.

Figure 2. This figure shows total gray matter volume for group by age.

The data is clear (for details of the localized frontal and parietal evolution see figs. 3 and 4). The question is: why does this happen? The paper attempts also to discuss that:

These results extend a consistent literature in rodents, non-human primates, and humans suggesting that early environments marked by stress or deprivation negatively influence brain development [65][69]. This emerging body of research has found differences in brain structure in portions of the frontal lobe, which fits well with the analysis presented here [68]. These findings suggest that aspects of low SES environments have important functional implications for children's health and adaptation [70], perhaps by influencing key features of central nervous system development. In regards to neurobiological mechanisms, the differences in volume we find are likely due to neuronal remodeling, rather than birth of new neurons (or neurogenesis) [27], [71], [72].


Candidate factors might include the effects of household resources, environmental stimulation, crowding, exposure to pathogens and noise, parental stress, and nutrition. It is also possible that pre-natal experiences affect brain development and reflect other disadvantages and risks related to poverty. Because humans are able to adapt to a range of environmental conditions, we must understand more about the level at which impoverished environments become toxic for children.

And quite suggestively in the introduction they mention as well that:

Conditions such as the variety and complexity of the stimuli in an animal's cage can influence different aspects of brain structure, including the number of neurons, glial cells, myelination, dendrites, synapses, and neurogenesis (for review, see Ref. [23][24]). 

The specific causes can be many but I'd dare say that "caging", i.e. the limitation of stimuli for living in smaller, impoverished, artificial habitats (including of course whatever limitations that the adults around them may have, such as low culture or emotional instability) is likely to be a key negative environmental factor for brain development.

On the other hand I can imagine that certain enrichment (cultural, health even technological, why not?) that has happened to our species in general in the last centuries, may be behind the so-called Flynn effect, which is that the measured IQ has been growing everywhere quite steadily. 

But in any case it is quite worrying that these social differences have such a big effect on the children and emphasizes the need to overcome them and to provide the best possible environment for the development of the future generations.


  1. This study fits well with the hypothesis that genes code maximum potential IQ in peak conditions, but that deprivation seriously impairs the ability of a person to meet that potential. It also supports the notion that early childhood is much more important in social class based differences in educational achievement than later interventions (e.g. at secondary and higher education levels). Alas, at least in my part of the world, the social safety net is particular weak for families with young children with poverty in the 0-5 age range approaching 50%, despite a quite strong social safety net for school age children and seniors. Also early childhood and elementary school teachers are among the lowest paid and capture only a very small relative share of the top academic performing secondary school graduates. We'd be better off skimping on secondary education and higher ed in favor of quality early childhood education and elementary education with high salaries for those teachers than for teachers later on. The difficulty is in demonstrating and implementing the fuzzy line between excellent teachers for young children and merely mediocre but adequate teachers for them.

    1. Do you really think that genes code IQ as such or rather that genes code (among other things) brain structure in manifold aspects and that this has direct correlation with IQ every thing else equal? I really do not think that intelligence or whatever measurements of it can be codified in genes, but the architectural blueprints for it instead.

      Maybe it's just a matter of wording but the blueprint concept seems to explain better all things genetic, including intelligence, because one thing is the blueprint and another one the finished building or machine, which depends not just on design but also, and decisively so, on the actual implementation of that design by the constructors. They all are going to follow the blueprint but different kind of materials, masons' skills, etc. will affect the final product critically. A cheapskate constructor company will make bad buildings out of the best designs and an good one instead will make quite decent buildings even out of poor blueprints. The same happens with the script and the movie, and so on.

      "... early childhood and elementary school teachers are among the lowest paid"...

      In Finland instead only the top performance students are allowed in such key positions. That's part of the reason why Finland outperforms nearly every country in educational achievement and satisfaction. See for example:

      This is not the approach most states take but it's clearly a winning one. But only in Finland a refugee kid gets a royal kind of education if and when he really needs it.

      The teaching method is also very non-competitive, with no exams before ending high school (but superior education success is still extremely high). Ironically Finland spends only 70% per student than the USA, teachers spend less time in classroom and homework almost does not exist. Naturally there's nearly no poverty in Finland, and that also helps a lot.

      Teachers are paid less than in the USA but still top-performing master degrees apply massively for some reason, among others that they can expect to make as much as any other average graduate after 15 years of career (unlike what happens in the USA). Source:

      Linked from that source: who works the most in Europe? →

      Greeks of course. It doesn't seem to pay off however. Luxembourgians work the least and they're the richest ones by far.


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