Does poverty reduce your IQ?

Only in America, allegedly.  That poverty CORRELATES with low IQ has long been known.  Poor people are often that way because they make dumb decisions -- spending all their money on beer, drugs and cigarettes, for instance.  A much more interesting question, therefore is whether poverty CAUSES low IQ.  We know that low IQ causes poverty but does poverty cause low IQ?

A recent very extensive and very sophisticated study set out to examine that -- and the results have been reported enthusiastically -- as showing that poverty DOES have an effect on IQ.  I reproduce a popular report of it below.

I have however, in my usual pesky way, gone back to the underlying academic journal article and read it. I have even looked at the numbers!  Despite its great methodological care and statistical complexity, it is an amusing example of failing to do something that the best journals now recommend:  Pre-register your expectations.  Studies that do not do that are very prone to data dredging effects -- looking for any correlation in the data that seems large and changing your hypothesis to say that's what you expected all along.

And the authors below did not pre-register their expectations.  They data-dredged.  After all the hard work they did in gathering and analysing their data, they initially found NO EFFECT of poverty on IQ.  So they desperately looked at their data to see what was in fact going on.  And they found that if they used U.S. data only, there was a weak effect in the direction expected.

Findings that were not pre-registered can of course still be accepted and there are long-standing procedures to allow for data dredging -- adopting an experiment-wise error-rate approach, for instance.  That is however very rarely done in fact.  It would take all the fun out of a lot of research. But some approach to allowing for that sort of thing is now being given emphasis in journal review policies.  In simple words, a much stronger effect is required for an unplanned relationship to be taken seriously. A weak relationship could be just a random oscillation.

The effects reported below were however very slight so I think that by current academic standards we should accept the null hypothesis.  We should conclude that poverty does NOT demonstrably affect IQ.

I don't like to flog a dead horse but a second defect in the study is that the findings were not controlled for race. Could race alone account for the aberrant U.S. results?  Knowing as we do how atypical are the IQs of persons with sub-Saharan African ancestry ("blacks", to use non-academic language) the researchers  should clearly have excluded blacks from all analyses on the grounds that they are a quite separate population requiring study in their own right.  The authors admit this but did not do it.

The original study is rather misleadingly titled: "Large Cross-National Differences in Gene × Socioeconomic Status Interaction on Intelligence"

Poverty has long been linked with lower levels of intelligence, especially among children, but a new study has suggested its impact may depend on where you live.

Scientists believe a person's intelligence is formed by a complex interplay between the genes they inherit from their parents and the environment they grow up in.

But a study of twins has determined that childhood poverty appears to 'dampen down' the potential contained within a person's genes - and the situation varies from country to country.

The study, conducted by researchers at University of Texas at Austin and the University of Edinburgh in Scotland, found people born in the US tend to suffer the effects of poverty more.

Elsewhere, the link between poverty and a lower IQ was less noticeable in Western Europe and Australia, and in fact the opposite may be true in the Netherlands.

The study, which is published in the journal Psychological Science, analysed the findings of 14 peer-reviewed papers.

Combined, they drew upon almost 25,000 sets of twins and siblings from the US, Australia, England, Sweden, Germany and the Netherlands.

The researchers said the differences between the US and European countries may be due in part to more universal access to healthcare, which has helped to close some socioeconomic gaps.

Differences in the education systems in the countries may also play a role.

The researchers behind the study added that the results could prove useful in helping to tackle gaps between socioeconomic groups.

They said that providing more uniform access to education and healthcare can counter and even reverse the negative effect of poverty on genes involved in IQ.


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