A recent study published in the prestigious journal Nature Neuroscience claimed that there is a correlation between parental income and children’s brain size. The publication was followed by researchers arguing that “These early life circumstances make it tougher for many children and it’s on many of us in society to make sure that children have equal possibilities”. Hum… There is always something fishy in this type of correlation studies where well-meaning social scientists try to deal with very complex issues. It was pretty obvious that the research would be picked up as a scientific endorsement by The Guardian, but when you see it splashed on other newspapers, you know it is time for discussing some unsupported-claims.
Let’s forget for a second that the size of the brain does not determine intelligence (otherwise the elephants would be ruling the earth and men would be more intelligent than women(1)…). Let’s also overlook the fact that correlation does not mean causation and that it is always tricky to draw conclusions from correlations alone.
Several studies(2,3,4) involving twins and adoptive families have shown that a big chunk of variability in intelligence is heritable (30 to 80%); no study has concluded otherwise. The authors of this study -tacitly admitting that there is also a genetic basis to brain size- took care in correcting their measurements by ethnicity (because –the horror, the horror- it is known that brain’s size differs among races). However, the authors completely ignored the direct effect of parental genes (they did not measure the brains of the parents); they simply assumed that parental income was more important than parental genes. When they investigated the relation between children’s brain size and the parents’ years in education (which is not the same as intelligence, not to mention brain size) they did find a correlation. They did not investigate the correlation between parental education and income, something of capital importance if you really want to prove that children’s brain size is affected by parents’ income and not by other factors such as parents’ education/intelligence or (following the authors’ quasi- interpretation of the world) brain size.
In summary, the work has the taste of research that has been conducted not to provide a valid scientific insight but to prove a pre-conceived point: being poor is bad for children. Not being concerned with the truth this type of research is generally carried out in a sloppy fashion. I by and large agree with the point that being poor is bad for children, but I cannot agree with the article’s evidence or implications.
I am a firm believer in government intervention to provide good quality free education for all and to prevent child suffering. I do not think however, that we need to deface science to promote these policies; this is bad for science and bad for policy. The defence of state-supervised child protection and nurture (both physical and intellectual) must be done on moral grounds or on valid scientific grounds but not on sloppy research.
(1) Mol Psychiatry. 2011 Oct;16(10):996-1005 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3182557/
(2) Nat Rev Neurosci. 2010 Mar;11(3):201-211 http://www.nature.com/nrn/journal/v11/n3/full/nrn2793.html
(3) Behav Genet. 2012 Sep;42(5):699-710 http://link.springer.com/article/10.1007%2Fs10519-012-9549-9547
Image: Poor mother and children by Dorothea Lange; the United States Library of Congress.