Advantages of IQ Testing: What an IQ Test Is Good For

The advantages of IQ testing are real but specific: a standard way to compare reasoning ability across people, early identification of children who need support or enrichment, group-level prediction of school and work results, and a profile of cognitive strengths and weaknesses that grades cannot give. Each benefit holds only when the test is properly normed and given under standard conditions, and none of them makes a score the whole person. This guide sets out the main benefits of IQ tests, the evidence behind each one and where each one stops. The full list of drawbacks is in our guide to the pros and cons of IQ testing.

• Standard comparison: the same tasks and conditions, scored against a norm sample, so a score means the same thing for different people.
• Early identification: Binet and Simon built the first practical scale in 1905 to find pupils who needed extra help, and modern tests still inform decisions on intellectual disability and giftedness.
• Prediction in groups: .81 with national exam results in more than 70,000 English children (Deary and colleagues, 2007) and .56 with education and .43 with occupation across longitudinal studies (Strenze, 2007).
• A profile, not only a number: the WISC-V reports five primary index scores, so a strong reasoner with slow processing speed shows up.
• Limit: any single score carries about 5 points of error either side.

What is the main advantage of an IQ test?

Standardisation. Every test taker gets the same tasks in the same order under the same conditions, and the result is placed on a scale built from a norm sample of thousands of people of the same age, with an average of 100. That is what lets a score from one examiner be compared with a score from another, and what an informal impression from a teacher or an interviewer cannot do. A score also comes with a published margin of error (an IQ score is a range, not a number), a kind of honesty that most other judgements about ability lack. Our guide to how IQ tests work explains how the norm sample turns answers into a score.

How does a score turn into something everyone can read?

Raw points mean little on their own, because a test can be easy or hard. The norm sample fixes where each raw score falls, and the result is printed as a position on a bell curve with an average of 100 and a standard deviation of 15. That shared scale is a second advantage: a 115 means the same thing, the 84th percentile, whoever gave the test. The table shows how scores, percentiles and the WISC-V labels line up.

Our IQ percentile calculator gives the position for any score, and the IQ score converter moves a score between scales, which matters because the same performance prints as a different number on a standard deviation 15, 16 or 24 scale.

Do IQ tests help identify learning needs and giftedness?

They were built for exactly that. Alfred Binet and Theodore Simon published the first practical intelligence scale in 1905 to identify schoolchildren who needed extra help, and Lewis Terman’s 1916 Stanford-Binet carried the idea to the United States (see the Stanford-Binet). Today a full test is one input in decisions about intellectual disability, which needs a low score, commonly about 70, plus evidence of difficulty in everyday life (see an IQ of 70), and in decisions about gifted programmes, whose typical cut-offs are collected in gifted cutoff scores. For adults, US disability rules write IQ numbers into the listing for intellectual disorder, inside a three-part test (what the score rules say).

The advantage is early and consistent identification: a child whose results are puzzling in class can be assessed against the same yardstick as every other child. It also helps in the other direction. A child can be both gifted and learning-disabled, and a profile that shows high reasoning beside low processing speed is how twice-exceptional children are found.

Do IQ scores predict school and work success?

In groups, yes. In a study of more than 70,000 English children, intelligence at age 11 correlated 0.81, at the level of underlying traits, with national exam results in 25 subjects at age 16 (Deary and colleagues, 2007). A meta-analysis of longitudinal studies found correlations of .56 with educational attainment, .43 with occupational level and .20 with income (Strenze, 2007). Squared, those figures say how much of the spread in an outcome goes with the score: about 31% for education, 18% for occupation and 4% for income.

That is useful for planning and research, because it lets a school or a study account for a known influence on results, but it is not a forecast for one person. Most of the variation in how people do sits outside the test. For the detail see does IQ predict school success and does IQ predict income, and for how sound the evidence is, do IQ tests really work.

What can an IQ profile show that grades cannot?

A full-scale score averages several abilities, and the pieces can differ. The WISC-V, the main children’s Wechsler test, reports five primary index scores: Verbal Comprehension, Visual Spatial, Fluid Reasoning, Working Memory and Processing Speed (see WISC-V scores explained). A child with high reasoning and low processing speed reads differently from the single number, and that difference is where a clinician looks for support. Our guide to ADHD and IQ shows where the gap tends to sit in a Wechsler report, in working memory and processing speed.

Which test gives which advantage?

Different tests suit different jobs, which is part of why a clinician chooses one rather than using a single instrument for everyone.

See our guides to the WPPSI-IV, the WISC-V, the Stanford-Binet and the KBIT-2, and professional IQ tests for how each is used.

Are IQ tests more objective than other ways of judging ability?

In one respect, yes: scoring rules are fixed and the norm sample is documented, which is an advantage over references, interviews and teacher impressions that vary with the judge. Objectivity is not the same as fairness. Test developers check items for bias in a narrow statistical sense and usually find little, but that does not settle whether the questions suit every background; cultural bias in IQ tests covers both meanings of the word.

Are there advantages for adults?

Three. First, hiring: a short ability test is a cheap, consistent screen, and the best-known review found general mental ability among the stronger predictors of job performance (Schmidt and Hunter, 1998), although a 2022 re-analysis lowered the mean validity estimates of many selection procedures by .10 to .20 points (Sackett and colleagues, 2022); see IQ tests for job interviews. Second, self-knowledge: an individually given test can show strengths and gaps (how to use your IQ test for self-improvement). Third, entry to societies and programmes with a cut-off, such as those in Mensa IQ score requirements and high IQ societies.

Where do the advantages stop?

The old norms figure is the 0.28-point-a-year gain from a meta-analysis of 271 samples (Pietschnig and Voracek, 2015). The balance sheet, including cultural bias, narrow scope and misuse, is in the pros and cons of IQ testing.

Quick answers about the advantages of IQ testing

• What is the main advantage of an IQ test? A standard way to compare reasoning ability, scored against a norm sample of people the same age.
• Do IQ tests have benefits for children? Yes: they help identify children who need support and children ready for enrichment, and they show strengths and gaps in a profile.
• Do IQ tests predict success? In groups, loosely: .56 with education, .43 with occupation, .20 with income.
• Are IQ tests useful for hiring? They are among the better single predictors, but a 2022 re-analysis lowered the validity estimates of many selection methods by .10 to .20 points.
• Is an IQ test accurate enough to rely on? To about 5 points either side of a reported score, when properly normed and given one-to-one.
• Does a higher score make someone better at everything? No: creativity, motivation and practical judgement sit outside the score.

Sources

• Deary, I.J., Strand, S., Smith, P. and Fernandes, C. (2007): Intelligence and educational achievement, Intelligence, 35(1), 13-21.
• Strenze, T. (2007): Intelligence and socioeconomic success: a meta-analytic review of longitudinal research, Intelligence, 35(5), 401-426.
• Schmidt, F.L. and Hunter, J.E. (1998): The validity and utility of selection methods in personnel psychology, Psychological Bulletin, 124(2), 262-274.
• Sackett, P.R., Zhang, C., Berry, C.M. and Lievens, F. (2022): Revisiting meta-analytic estimates of validity in personnel selection: addressing systematic overcorrection for restriction of range, Journal of Applied Psychology, 107(11), 2040-2068.
• Pietschnig, J. and Voracek, M. (2015): One century of global IQ gains: a formal meta-analysis of the Flynn effect (1909-2013), Perspectives on Psychological Science, 10(3), 282-306.