Three-stratum theory

The three-stratum theory is a theory of cognitive ability proposed by the American psychologist John Carroll in 1993.^[1][2] It is based on a factor-analytic study of the correlation of individual-difference variables from data such as psychological tests, school marks and competence ratings. These analyses suggested a three-layered model where each layer accounts for the variations in the correlations within the previous layer.

The three layers (strata) are defined as representing narrow, broad, and general cognitive ability. The factors describe stable and observable differences among individuals in the performance of tasks. Carroll argues further that they are not mere artifacts of a mathematical process, but likely reflect physiological factors explaining differences in ability (e.g., nerve firing rates). This of course does not alter the effectiveness of factor scores in accounting for behavioral differences.

Carroll proposes a taxonomic dimension in the distinction between level factors and speed factors. The tasks that contribute to the identification of level factors can be sorted by difficulty and individuals differentiated by whether they have acquired the skill to perform the tasks. Tasks that contribute to speed factors are distinguished by the relative speed with which individuals can complete them. Carroll suggests that the distinction between level and speed factors may be the broadest taxonomy of cognitive tasks that can be offered. Carroll distinguishes his hierarchical approach from taxonomic approaches such as Guilford’s Structure of Intellect model (three-dimensional model with contents, operations, and products).

Carroll's three-stratum model. Key: fluid intelligence (Gf), crystallized intelligence (Gc), general memory and learning (Gy), broad visual perception (Gv), broad auditory perception (Gu), broad retrieval ability (Gr), broad cognitive speediness (Gs), and processing speed (Gt). Carroll regarded the broad abilities as different "flavors" of g.

Development of the three-stratum theory

Since the development of cognitive psychology from 1950s, more researchers tend to consider intelligence as a type of cognitive abilities, such as the three-stratum theory of cognitive ability. It is based on theories from Spearman (1927) ^[3] and Horn & Cattell (1966),^[4] which are g-factor theory and crystallized-fluid theory. By factor-analysis, in 1993, Carroll put the three-stratum theory. More accurately, Carroll modified the two models.

This model suggests that intelligence consists with three strata.

Stratum III (highest, the most important): general intelligence, g factor

Stratum II (in the middle of stratum III and I, broad level): 8 factors —— fluid intelligence, crystallized intelligence, general memory and learning, broad visual perception, broad auditory perception, broad retrieval ability, broad cognitive speediness, and processing speed.

Stratum I (specific level): more specific factors under the stratum II^[5]

The three-stratum theory is developed from Horn & Cattell’s model (people may also call it CHC model) and has been widely accepted by 2000. Then in 2005, two psychologists questioned this model of intelligence structure. Johnson and Bouchard ^[6] compared three intelligence structure model: Gf-Gc model, three-stratum model and verbal-perceptual model. Then they conclude that all of these three models do not fit well according to their standard. Then they develop a new model called g-VPR model which has four stratum. Johnson and Bouchard claimed that their model fit better and is more logical.

See also

• CHC theory
• g factor
• Fluid and crystallized intelligence
• g-VPR model

References

1. J. B. Carroll (1993), Human cognitive abilities: A survey of factor-analytic studies, Cambridge University Press, New York, NY, USA.
2. J. B. Carroll (1997), "The three-stratum theory of cognitive abilities" in D. P. Flanagan, J. L. Genshaft et al., Contemporary intellectual assessment: Theories, tests, and issues, Guilford Press, New York, NY, USA, pp.122-130.
3. Spearman, C. (19927), The abilities of man, London: MacMillan
4. Horn, J. & Cattell, R. (1966). "Refinement and test of the theory of fluid and crystallized general intelligences.". Journal Of Educational Psychology 57: 253–270.
5. http://www.intelltheory.com/carroll.shtml
6. JOHNSON, W.& BOUCHARDJR, T. (2005). "The structure of human intelligence: It is verbal, perceptual, and image rotation (VPR), not fluid and crystallized. Intelligence". Intelligence 33: 393–416.

Further reading

• Hunt, Earl (2011). Human intelligence. Cambridge: Cambridge University Press. ISBN 978-0-521-88162-3. Lay summary (2011).
• Keith, T. & Reynolds, M. (2010). Cattell-Horn-Carroll abilities and cognitive tests: What we've learned from 20 years of research. Psychology in the Schools, 47(7), 635-650.