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The Three Strata Theory of Carroll Intelligence

The Three Strata Theory of Carroll Intelligence

January 25, 2022

The theory of the three layers of the intelligence of John B. Carroll proposes that the factor structure of human cognitive abilities is composed of a general intellectual capacity (the g factor), a set of 8 broad skills, such as the speed of mental processing or memory, and a third stratum that would include more specific intellectual skills and dependent on one of the previous ones.

In this article, we will analyze the Carroll model, which today is usually studied and applied in conjunction with the theory of fluid and crystallized intelligences proposed by Cattell and Horn. We will pause in a particular way in the analysis of each of the layers of intelligence that were described by this author.


  • Related article: "The theories of human intelligence"

John Carroll's theory of intelligence

The American psychologist John Bissell Carroll (1916-2003) is known mainly for his contributions in the field of psychometrics around the measurement of phenomena such as intelligence, language skills or academic performance. On the other hand, their theoretical approaches to cognition and language are also very relevant.

In particular, he stresses his theory of the three strata, model based on the results of hundreds of factor analyzes on samples of numerical data that can serve as predictors of intelligence, such as IQ tests or grades obtained in academic assessment tests.


Carroll presented the results of his studies along with his theory of intelligence in the work entitled "Human Cognitive Capacities: An Investigation of Analytic-Factorial Studies," which was published in 1993. In this book he emphasized the distinction between skills related to individual differences and those derived from the quality of education.

At present the theory of the three strata of Carroll is considered complementary to the model of Raymond B. Cattell and John L. Horn (focused on the division between fluid intelligence and crystallized intelligence), which Carroll himself had defended before creating his own. The assimilation of both perspectives into one can be attributed to Kevin McGrew (2012).

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The three strata of cognitive fitness

The theoretical proposal of Carroll can be included in the category of hierarchical models about intelligence, since it describes three strata that range from the most specific samples of cognitive aptitude to its general aspect, which is specified in the construct "factor g". These skills would have a stable character, according to the author.


Carroll stated that these capacities can probably be attributed to physiological variables . In this sense it is worth mentioning that authors such as Philip Vernon (who elaborated his own theory on the structure of intelligence) and Hans Eysenck have related cognitive aptitudes with the efficiency and quality of neuronal transmission.

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1. First stratum: primary mental aptitudes

According to Carroll, the lower stratum of the structure of intelligence is formed by the primary mental abilities, which include a large number of cognitive abilities: quantitative reasoning, spelling, visualization , aptitude for foreign languages, discrimination of speech sounds, fluency of ideas, reaction time, etc.

The results of the factor analyzes handled by Carroll and other later authors reveal that each of these skills, which have a high degree of specificity, ponder on one of the complex factors of the second stratum depending on the characteristics of the stimulating material and the overall ability on which they depend.

2. Second stratum: complex factors

At this level we find a set of broad cognitive skills. Originally Carroll proposed the presence of 10 factors in the second stratum, although later research reduced the number to 8:

  • Fluid intelligence: ability to reason and solve problems using new information.
  • Crystallized intelligence: referred to the depth and quantity of acquired verbal knowledge and to the handling of this type of data.
  • General memory and learning: ability to learn in general along with specific skills such as retaining information or recovering it in the short term.
  • Extensive capacity for recovery: includes the skills to manage ideas and associations fluently, both verbally and in images.
  • Visual processing: ability to perceive, analyze, remember and operate with visual stimulation.
  • Auditory processing: ability to discriminate and process sounds, including those associated with speech and music.
  • Broad cognitive speed: refers to the speed to handle stimuli during tests (eg numbers) and to complete them.
  • Processing speed : ability to execute automatic cognitive processes, particularly while maintaining selective attention.

Each of these factors includes various factors of a lower order corresponding to the first stratum. Thus, for example, crystallized intelligence includes reading comprehension, spelling and aptitude for foreign languages, while the capacity for extensive recovery is derived from creativity and fluency tests with different types of material.

3. Third stratum: general intelligence or g factor

The third stratum of the structure defined by Carroll is constituted by the general intelligence factor , a construct known as "factor g" and that is used by a large number of psychologists. This higher order ability would influence all the skills included in the second stratum, and therefore also in the third stratum indirectly.

  • Maybe you're interested: "Intelligence: G Factor and Spearman's Bifactorial Theory"

Bibliographic references:

  • Carroll, J. B. (1993). Human cognitive abilities: A survey of factor-analytic studies. New York: Cambridge University Press.
  • Hogan, T. P. (2004). Psychological tests: A practical introduction. Buenos Aires: Modern Manual.
  • Horn, J. & Cattell, R. (1966). Refinement and test of the theory of fluid and crystallized general intelligences. Journal of Educational Psychology, 57: 253-70.
  • McGrew, K. (2012). Cognitive abilities In D. P. Flanagan & P. ​​L. Harrison (Eds.), "Contemporary intellectual assessment: Theories, tests, and issues". New York: Guilford Press.

Cattell-Horn-Carroll theory - Intro to Psychology (January 2022).


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