IQ – a short and (over)simple FAQ for parents and teachers

There is something distasteful about IQ. Leaving aside the fact that it is often used by those who want to make race-based claims about merit, it reduces the educational project to the merely quantitative, crowding out other virtues. However, these objections should not mean that IQ be buried – as it has been largely since the publication of The Bell Curve in the 1980s. Educationalists seem increasingly to be taking an interest in the subject, and this piece seeks to answer a few of the most basic questions.


What is IQ? How is it tested? Does it really exist? Does it change over your life?

IQ stands for “intelligence quotient”, and is a total score derived from several standardized tests designed to assess human intelligence. IQ tests (example on this blog) tend to measure skills like speed of cognitive processing, pattern recognition, problem solving and memory. People who do well at one aspect on an intelligence test, tend to do well at all aspects.

Despite the many attempts by politicians, sociologists and educationalists to wish it way (e.g. Prospect, Claxton, Gladwell), that IQ describes something real is one of the most well-attested facts in the scientific community, not to mention a commonly-held belief by the general public.

As to whether it changes, the consensus seems to be that your IQ might go up or down a few points over your life, but does not change meaningfully.


Do children inherit IQ from their parents?

As with the question of whether intelligence exists, the answer to this question divides mainstream common sense opinion from many experts. The man on the street will tell you that intelligent parents tend to have intelligent children, although the implications for this position (see below) are so troubling for social policy interventions that it is an unpopular position within the education establishment.

From my cursory reading on the subject, IQ is, in the jargon, highly “heritable”, which is proved by the use of identical twin and adoption studies. Plomin is one of the most highly respected scientists on the issue; he lays out the heritability question well here.

Other important points:

  • Genes seem account for 50%-60% of a child’s IQ; the rest is made up by one’s home environment (NB also subject to parental influence of course) and factors called “the non-shared environment”, which relates to a child’s peer group, individual teachers, interests in, say, reading or memory games etc.


  • Because of these facts, intelligence is more impervious to adaptable environmental influences than many people think, or that many social policy people / teachers would like to think.


  • The genetic influence emerges more and more as a child grows older. This stands to reason because as we wield more agency over our lives as we grow older and environmental influence decrease, the more we choose a lifestyle (e.g. friends, extracurricular activities, schools and universities) that is in line with our IQ.


  • NB Dominic Cummings on individuals and heritability: “everything about heritability involves population statistics, not individuals – to put the point crudely, if you smash an individual over the head with a bat, the effect of genes on performance will fall to zero, hence the unsurprising but important finding that heritability estimates are lower for very deprived children.”


Why does IQ matter? What are the implications of having a particular IQ score? Does IQ = destiny?

High IQ scores correlate to all sorts of widely-agreed and somewhat unexpected benefits: examination success of course, but also a longer life, higher wages, weight, lower divorce rate etc. This blogpost goes into more detail.

Importantly, IQ is a measure that is more accurate the more people we are looking at. To predict one child’s life, it is only marginally helpful to know their IQ score. However, a school district, a school, even a class can be much better predicted by looking at average IQ scores.

How predictive is IQ for an individual child? Although children should always be encouraged to push themselves beyond any abstract numerical limitation, it is true that IQ is something of a minimum requirement in certain pursuits. As Charles Murray points out, it plays the same role that weight done is rugby pack as a forward. It’s not everything, but you need a minimum amount to do certain jobs, e.g. high level mathematics, astrophysics, etc.

As to IQ and destiny, the “Flynn effect” shows that IQ scores have been going up throughout the past century, giving hope that the non-heritable environment can be sufficiently manipulated to lead to changes in IQ. More on this here. It is nonetheless worth remembering that benefits of a high IQ are really the benefits of a higher IQ – i.e. relative to others in a given population rather than absolute.


For teachers – should an understanding of IQ affect my teaching?

Apart from being sensitive to the realities of intelligence and to the need for some individualised treatment, knowledge of IQ shouldn’t affect a classroom or school too much. As David Didau writes,.

“In a school with a well-designed curriculum and where children are well taught, all pupils will learn more (although some will, of course, learn more than others) whereas in a school with little in the way of curricular provision and where most of the teachers are bumbling loons, all pupils will learn less (although some will, of course, learn less than others).”


For parents – should an understanding of IQ affect my parenting?

I hope I have written enough about the importance of environments – both home and particularly school – to suggest that IQ does not absolve parents of their role as parents. (Though do read this provocative piece to the contrary!) It also seems likely that factors unrelated to IQ such as conscientiousness, motivation, perseverance and self-control are involved in educational success. And beyond educational success, establishing a happy home is of course a good in itself – rooting children hopefully to a place of love, security and happy memories.


Further reading:


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