The IQ taboo

While IQ research seems to be be emerging from its taboo phase, Anneli Rufus has written an article in Alternet which asks why the study of human intelligence was off the agenda for so long.

The analysis points to the usual suspects – the shadow of eugenics and racial research – but the article does have a couple of interesting quotes from Stephen Murdoch and Dennis Garlick. First, in much of the literature on IQ, the focus is on finding ‘g’, a single measure of general intelligence. Murdoch is agnostic as to whether ‘g’ exists:

“The science underlying IQ tests isn’t like experiments in the life or hard sciences,” Murdoch insists. “IQ proponents believe in something they call general intelligence. That is, they believe there is one singular, measurable, inheritable kind of intelligence that we can all be ranked on. I have no idea if this is correct or not. Nor do I care.”

While many of the debates about how well IQ captures ‘g’, if it exists, don’t seem to bear much fruit, IQ is clearly an important variable and has significant predictive power. I find it hard to be agnostic about a measure with such important life implications. And alternatives to ‘g’ do not seem to have more promise:

“There is still little evidence to support many of the claims made by proponents of alternative intelligences,” Garlick says, “yet it is advocated that life-changing decisions should be made based upon them. One is tempted to say that the alternative intelligence industry is a reminder that snake-oil salesmen are alive and well in this day and age.”

Garlick points to the need for IQ research:

“”I find it ironical that so much research is devoted to disorders like autism that only affect less than 1 percent of the population, but little research is devoted to understanding differences in IQ. … If the deficits of autism can be improved through research, why not IQ?”

As low IQ can have such significant costs, IQ research is an important basis for any policy discussion. Even if differences in IQ are intractable (which to an extent they certainly are), we can’t be any worse off for that knowledge.


  1. Because IQ tests be waaaaaycist.

    Seriously, though, people don’t like to hear things that make them sad. An implication of the g factor is that, by definition, half of all people are below average in overall mental ability, and that knowledge makes many people very unhappy. Alternative intelligences are comforting to people who don’t score high on standard IQ tests (or, more likely, have kids or friends who score low on standard IQ tests), because they can imagine that they’re good at something that isn’t measured by standard IQ (which may be true in some cases. I honestly don’t know enough about the g versus multiple intelligence debate to speak authoritatively on it).

  2. IQ is very nearly the most thoroughly researched aspect of human psychology, and new developments in those studies are ongoing (e.g. this month we saw a publication indicating that differences in IQ results between test takings by teens may be due to neurological change evidence by fMRI studies, rather than IQ test instrument error as previously often assumed).

    Nobody in the professional pychological field is seriously suggesting that IQ or something like it doesn’t exist. But, quite a few studies are converging on the notion that some traits orthogonal to IQ, some of which map approximately to Big Five Personality Traits like conscientiousness and extraversion have socio-economic impacts that rival IQ in order of magnitude impact and are substitutable in some contexts (e.g. hard work can make up for somewhat lower IQ). We are also developing a better understanding of a lot of mental health traits (e.g. sexual orientation, gender identity, schizophrenia, bipolar disorder, unipolar depression, anxiety, ADHD, propensity to be succeptible to substance abuse, psychopathy, vulnerablity to emotional trauma, dyslexia) that are relevant to significant numbers of people and don’t fit naturally on an IQ scale.

    There has also been a fair amount of work on what influences IQ driven by evidence that the heritability of IQ is lower for those in poverty, the Flynn effect, and public health research on breast feeding and lead exposure. Critical time periods for language acquisition and other nuture driven functions are becoming better understood. For example, study of schizophrenia is better operationalizing what is going on at a neurological level during adolescence in a way that has widespread application to educating adolescents who are not so afflicted. Autism research showing the condition to be caused by a large set of novel mutations is helping us develop a fuller catalog of the large set of genes implicated in the cognitive functions that autism impairs.

    Also, even accepting IQ as a dominant and critical element of functionality that is largely fixed at some point in life doesn’t obviously lead to specific policy implications. If we accept IQ should we dispense with overcredentialism, or better target educational resources on those most able to benefit? Should it follow that redistributive tax policy is better because earning more is easier for high IQ high earners, or that incentives for high producers matter more than incentives for everyone else?

    And, we are increasingly observing that while IQ may be important, that it is not nearly so simple a genetic trait as had been supposed when the Victorians started digging into it. Mechanically, vast numbers of genes appear to make small contributions, so a monolithic “g” doesn’t reflect a monolithic genetic cause.

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