Myths and famous claims
Do IQ tests only measure how good you are at IQ tests?
What is documented
IQ tests measure more than skill at IQ tests. In about 70,000 English children, intelligence at 11 correlated 0.81 with exam results at 16, and a review of 85 years of research put the validity of general mental ability for job performance at 0.51. They do not measure creativity, character or personality.
Want your own number? The test is 25 visual puzzles, about 12 minutes, no sign-up.
The myth
A common objection is that IQ tests only measure how good you are at IQ tests: a narrow, learnable knack for puzzles with no connection to anything people care about. If that were true, scores would not predict much outside the testing room.
The short verdict
The objection is wrong about prediction and partly right about limits. IQ scores predict school, work and other outcomes moderately to strongly across large groups. They also leave out a great deal, and they predict much less about any single person than the group figures suggest.
What the evidence shows
| Outcome | Correlation with intelligence | Source |
|---|---|---|
| Exam results at 16 (about 70,000 English children, tested at 11) | 0.81 | Deary et al., 2007 |
| Job performance (85 years of personnel research) | 0.51 | Schmidt & Hunter, 1998 |
| Education | 0.56 | Strenze, 2007 |
| Occupational level | 0.45 | Strenze, 2007 |
| Income | 0.23 | Strenze, 2007 |
Sources: (Deary, Strand, Smith & Fernandes, 2007) (Schmidt & Hunter, 1998) (Strenze, 2007). The APA task force reached similar conclusions in 1996: IQ correlates about .50 with school grades and about .55 with years of education, and typically .30 to .50 with job performance measures before correction (Neisser et al., 1996). It also noted that critics of the psychometric approach do not dispute that scores are stable and predict school achievement rather effectively.
Scores are stable over very long spans too. The same test taken at age 11 and age 90 correlated .54 in the Lothian Birth Cohort 1921 (Deary et al., 2013). And early-life test scores are linked to health: one standard deviation higher was associated with a 24% lower risk of death over 17 to 69 years of follow-up (Calvin et al., 2011).
Try one · Logical Reasoning
Which tile completes the second pair?
Tap the option you think is right, or show the answer.
Show the answer
The missing panel shows a large solid triangle pointing right on its own (option 4).
How to solve it
- Compare the first two panels and name exactly what changed.
- The whole figure turns a half turn.
- The large shape becomes solid.
- Nothing else changes.
- Apply the same changes to the third panel: a large hatched triangle pointing left on its own.
- So the missing panel shows a large solid triangle pointing right on its own.
That was 1 puzzle. The full test has 25.
Why scores predict anything
In 1904 Charles Spearman proposed a general intelligence factor, g (Wikipedia: g factor), an idea the g factor guide explains. A 1994 statement by 52 researchers described intelligence as a very general capability that "is not merely book learning, a narrow academic skill, or test-taking smarts" (Gottfredson, 1997). That breadth is why a short set of puzzles can relate to grades and jobs.
What scores do not show
- The same statement said intelligence tests do not measure creativity, character or personality, and are not intended to (Gottfredson, 1997).
- A correlation of .50 accounts for only about 25% of the variance, and tests predict considerably less than half the variance of job-related measures (Neisser et al., 1996).
- Lewis Terman, who followed children with IQs of 135 or above, concluded that the link between intelligence and achievement is far from perfect (Kell & Wai 2018).
As the 1994 statement put it, a high IQ "no more guarantees success than a low IQ guarantees failure in life" (Gottfredson, 1997).
Why the myth persists
Practice does raise scores a little, by about 4 IQ points on a retest (Hausknecht et al., 2007), and that makes the knack idea feel plausible. But a small practice effect is a different thing from measuring nothing. Some of the data above, such as the exam study, link scores taken at 11 to results five years later.
For more, read IQ and life outcomes, does IQ predict success and what an IQ test measures. See also the myth that IQ tests are biased, and the intelligence and health page.
Sources
- Deary, I. J., Strand, S., Smith, P., & Fernandes, C. (2007). Intelligence, 35(1), 13-21. doi.org/10.1016/j.intell.2006.02.001
- Schmidt, F. L., & Hunter, J. E. (1998). Psychological Bulletin, 124(2), 262-274. doi.org/10.1037/0033-2909.124.2.262
- Strenze, T. (2007). Intelligence, 35(5), 401-426. doi.org/10.1016/j.intell.2006.09.004
- Neisser, U., Boodoo, G., Bouchard, T. J., Jr., Boykin, A. W., Brody, N., Ceci, S. J., Halpern, D. F., Loehlin, J. C., Perloff, R., Sternberg, R. J., & Urbina, S. (1996). Intelligence: Knowns and unknowns. American Psychologist, 51(2), 77-101. doi.org/10.1037/0003-066X.51.2.77
- Gottfredson, L. S. (1997). Mainstream science on intelligence: An editorial with 52 signatories, history, and bibliography. Intelligence, 24(1), 13-23. doi.org/10.1016/S0160-2896(97)90011-8
- Calvin, C. M., Deary, I. J., Fenton, C., Roberts, B. A., Der, G., Leckenby, N., & Batty, G. D. (2011). Intelligence in youth and all-cause-mortality: Systematic review with meta-analysis. International Journal of Epidemiology, 40(3), 626-644. doi.org/10.1093/ije/dyq190
- Deary, I. J., Pattie, A., & Starr, J. M. (2013). The stability of intelligence from age 11 to age 90 years: The Lothian Birth Cohort of 1921. Psychological Science, 24(12), 2361-2368. doi.org/10.1177/0956797613486487
- g factor (psychometrics). Wikipedia. en.wikipedia.org/wiki/G_factor_(psychometrics)
- Kell, H. J., & Wai, J. (2018). Terman Study of the Gifted. In B. B. Frey (Ed.), The SAGE Encyclopedia of Educational Research, Measurement, and Evaluation (pp. 1665-1667). SAGE. doi:10.4135/9781506326139.n691 doi.org/10.4135/9781506326139.n691
- Hausknecht, J. P., Halpert, J. A., Di Paolo, N. T., & Moriarty Gerrard, M. O. (2007). Journal of Applied Psychology, 92(2), 373-385. doi.org/10.1037/0021-9010.92.2.373