The science of intelligence
Theories of intelligence
Short answer
The main theories of intelligence are Spearman's general factor g (1904), Cattell's fluid and crystallized intelligence (1963), Carroll's three-stratum model (1993) and the combined Cattell-Horn-Carroll (CHC) model, plus Gardner's multiple intelligences (1983) and Sternberg's triarchic theory (1985). The first four have strong research support; the last two are popular but weakly supported.
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The theories at a glance
Theories of intelligence split into two broad camps. Psychometric theories start from test scores and ask how they cluster. Broader theories start from the everyday idea of being smart and argue that tests miss much of it. The table sums up the main ones.
| Theory | Year | Core claim | Evidence status |
|---|---|---|---|
| Spearman's g | 1904 | One general factor runs through all mental tests | Strong: the pattern of correlated test scores is robust |
| Cattell's fluid and crystallized | 1963 | General ability splits into reasoning with new material and acquired knowledge | Strong: the two follow different paths with age |
| Carroll's three-stratum model | 1993 | A hierarchy: g, broad abilities, narrow skills | Strong: built from more than 460 data sets |
| Cattell-Horn-Carroll (CHC) | 1999 | Umbrella for the Cattell, Horn and Carroll models | Strong: broad abilities supported in a 2023 network analysis |
| Gardner's multiple intelligences | 1983 | Several separate intelligences, including musical and bodily-kinesthetic | Weak: judged to lack adequate empirical support |
| Sternberg's triarchic theory | 1985 | Analytic, creative and practical intelligence | Contested: practical intelligence claims strongly criticized |
| Emotional intelligence | 1990 | Skills for perceiving and managing emotion | Mixed: modest links to job performance |
Spearman and the general factor
In 1904 Charles Spearman proposed a general intelligence factor, g, to explain why people who score well on one kind of mental test tend to score well on others (Wikipedia: g factor). The pattern itself is not in dispute. Different cognitive and learning abilities correlate about 0.30 on average at the observed level, and about 0.60 or higher genetically (Plomin & Deary, 2015). Our g factor guide covers how factor analysis extracts it.
Cattell: fluid and crystallized
In 1963 Raymond Cattell distinguished fluid intelligence, reasoning with novel material, from crystallized intelligence, acquired knowledge (Wikipedia: Fluid and crystallized intelligence). The split earns its keep because the two behave differently: processing speed and some reasoning measures peak in the late teens and twenties, while vocabulary and knowledge keep rising into the sixties (Hartshorne & Germine, 2015). See fluid vs crystallized intelligence.
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 outlined circle, with small solid shapes: a circle at the top (option 5).
How to solve it
- Compare the first two panels and name exactly what changed.
- The whole figure turns a quarter turn counterclockwise.
- The large shape becomes outlined.
- Nothing else changes.
- Apply the same changes to the third panel: a large solid circle, with small solid shapes: a circle at the right side.
- So the missing panel shows a large outlined circle, with small solid shapes: a circle at the top.
That was 1 puzzle. The full test has 25.
Carroll and the CHC family
John Carroll's 1993 book reanalyzed more than 460 data sets from the factor-analytic literature and presented a hierarchical, three-stratum theory of cognitive ability (Carroll, 1993). In 1999 Richard Woodcock brokered the Cattell-Horn-Carroll umbrella term with John Horn and Carroll (McGrew, 2023). A 2023 bifactor reanalysis supported Carroll's conclusion that his model represents the structure of intelligence better than two prominent alternatives (McGrew, 2023), and a 2023 network analysis of a large test norm sample supported the main CHC broad abilities (McGrew et al., 2023). The full model is on the CHC theory page.
Gardner's multiple intelligences
Howard Gardner proposed in 1983 that there are several intelligences, including musical, bodily-kinesthetic and personal intelligences alongside spatial, linguistic and logical-mathematical abilities (Neisser et al., 1996). The APA task force wrote that tests in these new domains had yet to be shown to be stable and valid (Neisser et al., 1996), and a 2006 review concluded the theory lacks adequate empirical support (Waterhouse, 2006). More on the multiple intelligences page.
Sternberg's triarchic theory
Robert Sternberg's 1985 theory proposes analytic, creative and practical intelligence, and holds that mainstream tests measure only the analytic part to any significant extent (Neisser et al., 1996). A 2003 critique concluded that the evidence for a practical intelligence distinct from g, and predicting success as well as g, collapses on close examination (Gottfredson, 2003). See the triarchic theory page.
Emotional intelligence
Salovey and Mayer framed emotional intelligence in 1990 as skills for appraising, expressing and regulating emotion and using feelings to plan and achieve (Salovey & Mayer, 1990). A 2011 meta-analysis found corrected correlations of 0.24 to 0.30 with job performance (O'Boyle et al., 2011). The emotional intelligence page covers the competing models.
How to read the disagreement
The theories are less opposed than they look. The psychometric models describe how test scores hang together, and on that question the evidence is strong. The broader theories argue that the word intelligence should cover more than tests sample. That is a reasonable point about the word, but their specific claims about separate, measurable intelligences have not held up well when tested.
Sources
- g factor (psychometrics). Wikipedia. en.wikipedia.org/wiki/G_factor_(psychometrics)
- Fluid and crystallized intelligence. Wikipedia. en.wikipedia.org/wiki/Fluid_and_crystallized_intelligence
- Carroll, J. B. (1993). Human cognitive abilities: A survey of factor-analytic studies. Cambridge University Press. doi.org/10.1017/CBO9780511571312
- McGrew, K. S. (2023). Carroll's three-stratum (3S) cognitive ability theory at 30 years. Journal of Intelligence, 11(2), 32. doi.org/10.3390/jintelligence11020032
- McGrew, K. S., Schneider, W. J., Decker, S. L., & Bulut, O. (2023). A psychometric network analysis of CHC intelligence measures. Journal of Intelligence, 11(1), 19. doi.org/10.3390/jintelligence11010019
- 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
- Waterhouse, L. (2006). Multiple intelligences, the Mozart effect, and emotional intelligence: A critical review. Educational Psychologist, 41(4), 207-225. doi.org/10.1207/s15326985ep4104_1
- Gottfredson, L. S. (2003). Dissecting practical intelligence theory: Its claims and evidence. Intelligence, 31(4), 343-397. doi.org/10.1016/S0160-2896(02)00085-5
- Plomin, R., & Deary, I. J. (2015). Molecular Psychiatry, 20, 98-108. doi.org/10.1038/mp.2014.105
- Hartshorne, J. K., & Germine, L. T. (2015). Psychological Science, 26(4), 433-443. doi.org/10.1177/0956797614567339
- Salovey, P., & Mayer, J. D. (1990). Emotional intelligence. Imagination, Cognition and Personality, 9(3), 185-211. doi.org/10.2190/DUGG-P24E-52WK-6CDG
- O'Boyle, E. H., Humphrey, R. H., Pollack, J. M., Hawver, T. H., & Story, P. A. (2011). The relation between emotional intelligence and job performance: A meta-analysis. Journal of Organizational Behavior, 32(5), 788-818. doi.org/10.1002/job.714