Why IQ Tests May Not Measure Intelligence

Last Updated on November 2, 2026 by Karl Thompson

IQ (intelligence quotient) tests claim to measure intelligence, and they’ve been used to argue that educational success reflects natural ability. Sociologists are sceptical. The key points are:

1. IQ tests measure a narrow kind of reasoning, and even psychologists who defend them admit intelligence is easier to measure than to define.
2. Otto Klineberg’s studies in the 1920s showed that test scores depend on culture, for example on how much a culture values speed.
3. Tests may favour the middle class, because they’re largely designed and standardised by and on middle-class groups.
4. Even high IQ doesn’t guarantee success: Malcolm Gladwell argues there is a threshold beyond which extra IQ points make little difference.
5. All of this matters for the meritocracy debate. If IQ partly reflects class background, then “ability” can’t simply be separated from privilege.

This is relevant to social class differences in educational achievement and to the debate about meritocracy, within the sociology of education on AQA Paper 1 (7192/1).

What IQ tests try to measure

The American psychologist Arthur Jensen, in a famous and highly controversial 1969 article, described intelligence as “probably best thought of as a capacity for abstract reasoning and problem solving”. In other words, the ability to discover the rules, patterns and logical principles behind things, and apply them to new problems.

IQ tests try to measure this. So they avoid questions that test factual knowledge, such as “What is the capital of the USA?”, and instead ask questions such as “What is the next number in this sequence: 1, 8, 27, 64, __?”

Jensen himself admitted that “intelligence, like electricity, is easier to measure than to define”, and that in practice “intelligence, by definition, is what intelligence tests measure”. That’s the critics’ main point. Abstract reasoning is only one part of the full range of mental abilities, so a test of it may not be a valid measure of intelligence as a whole.

Culture and intelligence: Klineberg’s research

In 1926 the Canadian-born psychologist Otto Klineberg gave performance tests to 120 Native American children on and near the Yakima Reservation in Washington State, and to 107 white children in a nearby town. One test timed how long it took the children to fit differently shaped wooden blocks into the matching holes in a frame.

The Yakima children took longer, but they made fewer errors. Klineberg argued that the differences in speed reflected differences in economic and cultural environment, and that the greater accuracy probably came from working more slowly. A fast pace, he suggested, was a feature of modern American life that hadn’t become part of Yakima culture. He published the study in 1928.

The implication is that it is inappropriate to compare the intelligence of people from different cultures using tests built around one culture’s values. Any test that rewards speed favours cultures that value speed.

Culture, class and IQ

Critics argue that the same applies to social classes within one society. IQ tests have largely been constructed by, and standardised on, middle-class groups, so they may reward middle-class ways of thinking and middle-class experience. If cultural deprivation theorists are right that working-class children are socialised differently, or if cultural capital theorists are right that schools reward middle-class culture, then working-class children may do less well on IQ tests for cultural reasons rather than because they are less intelligent.

What else affects a test score?

Klineberg argued that at least the following factors influence how well someone does in an IQ test:

• their previous experience and education
• how familiar they are with the kind of material in the test
• their motivation to do well, in the time allowed
• their rapport with the person giving the test
• how well they know the language the test is in
• their physical health and well-being

Every one of these is likely to vary with social class.

IQ scores change over time

One of the strongest pieces of evidence that IQ isn’t a fixed natural quantity is the Flynn effect. James Flynn (1987) compared IQ data across a generation in 14 countries and found gains of between 5 and 25 points, far too fast for genetic change to explain. In the Dutch data, he estimated that unidentified environmental factors accounted for most of the gain. His own conclusion was striking: IQ tests seem to measure something that is only weakly linked to intelligence itself. If environment can shift IQ across a whole population, it can shift it between social classes too.

Does high IQ lead to success? Terman and the IQ threshold

In his book Outliers (2008), the journalist Malcolm Gladwell tells the story of the psychologist Lewis Terman. From the 1920s Terman tested huge numbers of American schoolchildren, picked out a group with exceptionally high IQ scores, and followed them through their lives, publishing the results as Genetic Studies of Genius. He expected them to become the country’s future elite.

According to Gladwell, they mostly didn’t. Some were very successful, but most had good, ordinary careers, and some ended up in quite average jobs. Gladwell also points out that two children Terman rejected because their scores weren’t high enough went on to win Nobel Prizes. He reports the sociologist Pitirim Sorokin’s critique: a group chosen at random from the same family backgrounds would probably have done about as well.

Gladwell’s conclusion is that IQ has a threshold. Up to a point, a higher IQ does go with more education and more success. But once you’re clever enough for a field, extra IQ points make surprisingly little difference. Gladwell uses a basketball analogy: you need to be tall to play professionally, but once you’re tall enough, being even taller matters much less than speed and skill. What makes the difference above the threshold is other things, such as creativity, opportunity and family background.

Gladwell is a journalist, not a sociologist, and the threshold idea is his reading of the evidence. It’s still a useful point to make: if IQ beyond a certain level doesn’t predict success, then the very top jobs aren’t simply going to the very cleverest people.

IQ and the meritocracy debate

This is where IQ matters most for A-level sociology. Functionalists argue that education is meritocratic, sorting people by ability. If ability means IQ, and IQ tests measure something real and fair, that argument gets support.

Marxists Bowles and Gintis disagreed. They argued that IQ explains only a small part of how far people get in education and how much they earn, and that family background is a much better predictor of both. Returning to the question in 2002, they estimated that genetically inherited IQ explains only a very small part of why incomes run in families. If the tests themselves favour the middle class, the case against the functionalist view is stronger still: “ability” would partly be class background measured in another way.

Evaluation

Supporters of IQ testing point out that IQ scores do predict educational attainment reasonably well, and that test designers have tried to reduce cultural bias, for example with non-verbal tests.

HOWEVER, predicting attainment isn’t the same as measuring natural ability. IQ tests and school exams may simply measure many of the same learned skills, so of course they agree. And non-verbal tests still depend on familiarity with the kinds of task they set, as Klineberg’s speed findings show.

The balanced conclusion is that IQ tests measure something, but not “intelligence” in any pure, culture-free sense, and certainly not something that can be cleanly separated from a child’s background.

How this comes up in the exam

IQ is useful evaluation in two kinds of Paper 1 (7192/1) essay:

• Meritocracy. June 2021, Q04: Applying material from Item B and your knowledge, evaluate the view that the education system is meritocratic. [30 marks] Use IQ to question what “ability” means.
• Social class differences in achievement. June 2018, Q04: Applying material from Item B and your knowledge, evaluate sociological explanations of social class differences in educational achievement. [30 marks] Use IQ to challenge explanations based on natural differences in ability between classes. See my essay on this question.

Sociology of Education Revision Bundle

Signposting and Related Posts

This post has been written primarily for students studying the education topic, as part of the AQA’s A-Level Sociology course.

For the debate IQ feeds into, see meritocracy and education. For cultural explanations of class differences, see cultural capital and cultural deprivation.

You can find the full set of notes on the sociology of education page.

Please click here to return to the homepage – ReviseSociology.com

Sources

Bowles, S. and Gintis, H. (2002) Schooling in Capitalist America revisited. Sociology of Education.

Flynn, J. R. (1987) Massive IQ gains in 14 nations: what IQ tests really measure. Psychological Bulletin, 101(2), 171.

Gladwell, M. (2008) Outliers: The Story of Success. New York: Little, Brown.

Jensen, A. R. (1969) How much can we boost IQ and scholastic achievement? Harvard Educational Review, 39(1), 1–123.

Klineberg, O. (1928) An experimental study of speed and other factors in “racial” differences. Archives of Psychology, No. 93.