Thinning IQ

Human beings enjoy continuity. What do you do when get up in the morning? Is it different every day or do you tend toward the same routine? How distressed are you when you find that you have run out of your favourite muesli? On a broader scale just look at how we have to debate and discuss any change we contemplate. This happens whether it is changing the brand of coffee used in the office kitchenette or altering social welfare spending; the scale of the change doesn’t matter, humans are challenged by change and it is as if discussion and rumination gives us time to come to terms with the changes that must come. At every opportunity though, we seek to create constancy as bedrock upon which we can then express our own exciting individualism. You can see this in our attitudes to a multitude of things but let’s take IQ as an example. For quite a while now, since the early 1900s when Alfred Binet developed his IQ tests on behalf of the French government, IQ has been regarded as a fixed measure of a person’s intellectual capacity. Yet this perception of IQ tells us more about our need for constancy and categorisation than the nature of IQ itself. Indeed a new study has shown that not only does IQ change, it does so in line with changes in the structure of your brain.

The study involved children and adolescents across the United States who were tested over a period of two years. The testing involved both IQ tests and MRI scans to measure the thickness of the cortex in each subject’s brain. The cortex is the outermost layer of your brain. It contains nerve cell bodies and is essential for cognitive function but is only a few millimetres thick. As a rule the cortex tends to become gradually thinner after the age of six as a “normal” part of ageing.

The results showed that changes in IQ corresponded to changes in cortical thickness. For example, people who showed a significant increase in IQ did not show the expected cortical thinning over the two years of the study. By contrast, people whose IQ stayed the same had the normally expected cortical thinning and people with a significant decrease in IQ showed exaggerated cortical thinning.

In the past small differences in IQ for an individual when tested over a period of time have been put down to limits in testing. What this suggests though is that IQ can change and that the change is reflected in brain’s cortex.

The researchers point out that this evidence indicates the folly of judging someone based on an IQ test taken years ago. The more weighty social concern though is the inaccuracy of statements intended to indicate stupidity such as, “Gee you’re thick”. The new accusation of moronic qualities might more aptly go along the lines of, “Your cortex is so thin!”.