CHC Theory RightPeople

10 Jul 2024

Why having a theory underpinning Psychometrics is important

Many psychometric tests used in business nowadays make no reference to how they were developed or even worse, have no well recognised theory guiding their development at all.

The Cattell-Horn-Carroll (CHC) theory is a prominent model in the field of psychometrics that RightPeople use to guide test development, which provides a scientifically validated and comprehensive framework for understanding human cognitive abilities. This post provides an overview of the history and importance of CHC theory:

Origins and Development

Raymond B. Cattell

  • Early Work: The origins of CHC theory can be traced back to the work of Raymond B. Cattell, a British-American psychologist. In the 1940s and 1950s, Cattell developed the concept of fluid and crystallised intelligence.
    • Fluid Intelligence (Gf): Refers to the ability to solve novel problems, use logic in new situations, and identify patterns.
    • Crystallised Intelligence (Gc): Refers to the ability to use knowledge, experience, and learned information.
  • Investment Theory: Cattell proposed that fluid intelligence invests in the development of crystallised intelligence over time.

John L. Horn

  • Expansion: John L. Horn, a student of Cattell, expanded on his mentor’s work in the 1960s and 1970s. Horn identified several additional broad cognitive abilities beyond Gf and Gc, contributing significantly to the development of the Gf-Gc theory.
    • Broad Abilities: Included factors such as visual processing (Gv), auditory processing (Ga), short-term memory (Gsm), long-term storage and retrieval (Glr), and processing speed (Gs).

John B. Carroll

  • Three-Stratum Theory: In the 1990s, John B. Carroll, an American psychologist, conducted a comprehensive re-analysis of hundreds of data sets on cognitive abilities. He proposed the Three-Stratum Theory, which organised cognitive abilities into a hierarchical model:
    • Stratum III: General intelligence (g) at the top.
    • Stratum II: Broad abilities (similar to those identified by Cattell and Horn).
    • Stratum I: Narrow abilities, representing specific skills and tasks.

Integration and CHC Theory

  • CHC Integration: In the late 1990s and early 2000s, the work of Cattell, Horn, and Carroll was integrated into what is now known as the CHC theory. This integration was spearheaded by researchers such as Kevin McGrew and colleagues, who recognised the complementary nature of the Gf-Gc and Three-Stratum models.
    • Comprehensive Model: CHC theory combines the broad and narrow abilities identified by Cattell and Horn with the hierarchical structure proposed by Carroll.

Impact and Applications

  • Standardised Tests: CHC theory has significantly influenced the development and revision of various standardised intelligence tests, such as the Woodcock-Johnson Tests of Cognitive Abilities and the Wechsler Intelligence Scales.
  • Educational Assessment: The theory provides a framework for understanding individual differences in cognitive abilities, which is valuable in educational assessment and intervention.
  • Neuropsychological Evaluation: CHC theory is also used in neuropsychological evaluations to diagnose and understand cognitive deficits and strengths.

Current Status and Research

  • Ongoing Research: CHC theory continues to be a focus of ongoing research in psychometrics and cognitive psychology. Researchers are continually refining the model and exploring its implications for understanding human intelligence.
  • Global Influence: While originating in the United States, CHC theory has gained international recognition and is used by psychologists and educators around the world.


The CHC theory represents a significant advancement in the understanding of human cognitive abilities. By integrating the pioneering work of Cattell, Horn, and Carroll, the theory provides a robust framework that continues to shape research, assessment, and practical applications in psychometrics and cognitive psychology.

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