Theoretical Framework

The CHC
Model.

Exploring the Cattell-Horn-Carroll theory—the most comprehensive and empirically supported framework for understanding human cognitive abilities.

1 What is the CHC Model?

The Cattell-Horn-Carroll (CHC) theory is the gold standard framework for understanding human cognitive abilities. It emerged from the integration of two of the most influential theories in the history of intelligence research: Raymond Cattell and John Horn's Gf-Gc theory and John Carroll's three-stratum theory.

Carroll's theory was based on his monumental 1993 work, "Human Cognitive Abilities: A Survey of Factor-Analytic Studies", which reanalyzed over 460 datasets spanning the entire 20th century of intelligence research. This meta-analytic approach provided unprecedented empirical support for a hierarchical model of cognitive abilities.

The formal integration of these theories into CHC occurred in the late 1990s and early 2000s, primarily through the work of Kevin McGrew. Today, CHC theory represents the consensus framework in differential psychology and serves as the foundation for virtually all modern intelligence tests. For an authoritative overview, see Flanagan & Harrison's Contemporary Intellectual Assessment (2012).

2 The Three-Stratum Structure

CHC theory organizes cognitive abilities into three hierarchical levels (strata), each representing a different degree of generality:

Stratum III: g (General Intelligence)
Stratum II: Broad Abilities (Gf, Gc, Gv, Gs, Gsm, Glr, Ga, Gq...)
Stratum I: Narrow Abilities (70+ specific cognitive skills)
  • Stratum III - General Intelligence (g): The apex of the hierarchy, representing the common variance shared across all cognitive tasks. This general factor accounts for the positive manifold—the observation that people who do well on one cognitive test tend to do well on most others. ACIS measures this as Full Scale IQ (FSIQ).
  • Stratum II - Broad Abilities: Approximately 16 broad cognitive domains that represent major categories of cognitive function. These include Fluid Reasoning (Gf), Crystallized Intelligence (Gc), Visual Processing (Gv), Processing Speed (Gs), and more.
  • Stratum I - Narrow Abilities: Over 80 specific abilities that cluster within the broad domains. For example, within Gc (Crystallized Intelligence), narrow abilities include Lexical Knowledge, General Information, and Language Development.

3 The Primary Broad Abilities

CHC theory currently recognizes approximately 16 broad abilities. ACIS measures the six most g-loaded and clinically relevant abilities:

Fluid Reasoning Gf

The ability to solve novel problems using logic, pattern recognition, and abstract thinking without relying on prior knowledge. Gf is considered the "purest" measure of reasoning ability—research by Conway et al. (2003) shows it correlates .80-.90 with working memory. Tasks include matrix reasoning, figure series, and inductive/deductive logic problems. Gf peaks in early adulthood (mid-20s) and shows gradual decline with age, as documented by Salthouse (2004).

Crystallized Intelligence Gc

The breadth and depth of acquired knowledge and the ability to apply it. Gc reflects cultural learning and educational experience—vocabulary, general information, verbal reasoning. Unlike Gf, crystallized intelligence continues to grow throughout most of the lifespan, often not declining until very late in life.

Visual Processing Gv

The ability to perceive, analyze, synthesize, and mentally manipulate visual patterns and spatial relationships. Includes visualization (imagining how objects would look rotated or transformed), spatial relations, and visual memory. Critical for fields like architecture, engineering, surgery, and art.

Processing Speed Gs

The speed and efficiency with which simple cognitive tasks can be performed, particularly under time pressure. Reflects how quickly the cognitive system can execute basic operations. Gs is highly sensitive to brain health and shows notable decline with aging and neurological conditions, as documented in the Scottish Mental Surveys.

Short-Term/Working Memory Gsm/Gwm

The ability to apprehend and maintain information in immediate conscious awareness (Gsm) and to manipulate that information to produce a result (Gwm). Working memory is strongly implicated in complex cognition—it's the "mental workspace" where we hold and process information. See D'Esposito & Postle (2015) in Nature Reviews Neuroscience for neural basis research.

Quantitative Knowledge Gq

The store of acquired mathematical knowledge and the ability to apply quantitative concepts to solve problems. Includes numerical facility, mathematical achievement, and quantitative reasoning. Gq is partially crystallized (learned) but also involves fluid reasoning with numbers.

4 Additional Broad Abilities

Beyond the six abilities measured by ACIS, CHC theory recognizes several other broad abilities:

  • Auditory Processing (Ga): Perceiving, analyzing, and synthesizing patterns among auditory stimuli. Important for language acquisition and music.
  • Long-Term Storage & Retrieval (Glr): The ability to store and fluently retrieve information from long-term memory. Includes associative memory and ideational fluency.
  • Reading & Writing (Grw): Acquired knowledge and skills related to written language, including reading decoding, comprehension, and writing ability.
  • Reaction Time/Decision Speed (Gt): The speed of making very simple decisions or responses, often measured in milliseconds.
  • Psychomotor Speed (Gps): The speed and fluidity of physical body movements (beyond cognitive speed).
  • Olfactory Abilities (Go): The ability to detect and process information via the sense of smell.
  • Tactile Abilities (Gh): The ability to detect and process information via touch.
  • Kinesthetic Abilities (Gk): The ability to perceive body position and movement.
  • Domain-Specific Knowledge (Gkn): Specialized knowledge in particular domains (e.g., mechanical knowledge, knowledge of games).

5 Narrow Abilities: The Foundation

Each broad ability comprises multiple narrow abilities. Understanding these helps interpret specific test performance:

Within Fluid Reasoning (Gf):

  • Induction (I): Discovering underlying rules or patterns from specific instances
  • General Sequential Reasoning (RG): Logical step-by-step reasoning
  • Quantitative Reasoning (RQ): Reasoning with numbers and mathematical concepts

Within Crystallized Intelligence (Gc):

  • Lexical Knowledge (VL): Vocabulary breadth and depth
  • General Information (K0): Store of general factual knowledge
  • Language Development (LD): General language ability and understanding
  • Listening Ability (LS): Comprehending spoken language

Within Visual Processing (Gv):

  • Visualization (Vz): Mentally manipulating visual objects
  • Speeded Rotation (SR): Quickly rotating mental images
  • Spatial Relations (Cs): Perceiving spatial patterns and relationships
  • Closure Speed (CS): Identifying partially obscured patterns

6 Why CHC Matters for Testing

CHC theory has become essential for modern cognitive assessment because it provides:

  • Comprehensive Coverage: Ensures that tests sample the full range of human cognitive abilities rather than just a subset, reducing construct underrepresentation.
  • Theoretical Grounding: Allows test developers to build assessments based on a well-validated empirical framework rather than intuition or tradition.
  • Clinical Utility: Enables practitioners to identify specific cognitive strengths and weaknesses with greater precision, leading to better intervention planning.
  • Cross-Battery Assessment: Provides a common language (the "CHC nomenclature") for integrating results from different test batteries to create a comprehensive cognitive profile.
  • Research Integration: Allows findings from different studies and instruments to be compared and synthesized within a unified framework.
  • Developmental Understanding: CHC abilities show distinct developmental trajectories, helping interpret age-appropriate performance.

All major intelligence tests developed in the 21st century—including the WAIS-IV/V, WISC-V, Stanford-Binet 5, Woodcock-Johnson IV, and KABC-II—are explicitly grounded in CHC theory.

7 CHC in ACIS

ACIS was designed from the ground up with CHC theory as its foundation. The test's 20 subtests systematically assess abilities across six broad CHC domains, providing comprehensive coverage of the most g-loaded abilities:

  • Verbal Comprehension Index (VCI): Measures Crystallized Intelligence (Gc) through Antonyms, Information, Paragraph Reading, Vocabulary, and Similarities subtests.
  • Fluid Reasoning Index (FRI): Assesses Fluid Reasoning (Gf) through Matrix Reasoning, Figure Weights, Visual Number Series, Graph Mapping, and Figure Series subtests.
  • Visual Spatial Index (VSI): Evaluates Visual Processing (Gv) through Visual Puzzles, Block Design, and Spatial Relations subtests.
  • Working Memory Index (WMI): Measures Working Memory (Gwm) through Digit Span, Alphanumeric Sequencing, and Visual Sequence subtests.
  • Processing Speed Index (PSI): Assesses Processing Speed (Gs) through Coding and Symbol Search subtests.
  • Quantitative Reasoning Index (QRI): Measures Quantitative Knowledge (Gq) through Mathematical Achievement and Arithmetic subtests.

This comprehensive structure gives ACIS its remarkable .99 g-loading while also providing clinically meaningful index and subtest-level information.

8 The Evolution of CHC Theory

CHC theory continues to evolve as researchers refine our understanding of cognitive abilities:

  • 1941: Raymond Cattell proposes the distinction between fluid (Gf) and crystallized (Gc) intelligence.
  • 1965-1998: John Horn expands Gf-Gc theory to include additional broad abilities (Gv, Gs, Gsm, Glr, Ga, Gq).
  • 1993: John Carroll publishes "Human Cognitive Abilities," establishing the three-stratum model based on factor analysis of 460+ datasets.
  • 1998-2005: Kevin McGrew and colleagues formally integrate Horn-Cattell and Carroll frameworks into unified CHC theory.
  • 2012: Major update distinguishes between Short-Term Memory (Gsm) and Working Memory Capacity (Gwm) as separate constructs.
  • 2018-Present: Ongoing refinements including better articulation of processing speed factors and addition of new abilities like Domain-Specific Knowledge (Gkn).

ACIS incorporates the latest CHC research and updates to provide the most current and accurate assessment of cognitive abilities.

9 Key References

For those wishing to explore CHC theory in greater depth:

  • Carroll, J.B. (1993): Human Cognitive Abilities: A Survey of Factor-Analytic Studies. WorldCat.
  • McGrew, K.S. (2009): CHC theory and the human cognitive abilities project: Standing on the shoulders of the giants of psychometric intelligence research. Intelligence, 37(1), 1-10. DOI: 10.1016/j.intell.2008.08.004
  • Schneider, W.J. & McGrew, K.S. (2018): The Cattell-Horn-Carroll theory of cognitive abilities. In D.P. Flanagan & E.M. McDonough (Eds.), Contemporary intellectual assessment (4th ed.). Guilford Press.
  • Horn, J.L. & Cattell, R.B. (1966): Refinement and test of the theory of fluid and crystallized general intelligences. Journal of Educational Psychology, 57(5), 253-270. DOI: 10.1037/h0023816
  • Flanagan, D.P. & Harrison, P.L. (2012): Contemporary Intellectual Assessment: Theories, Tests, and Issues (3rd ed.). Guilford Press.
  • McGrew, K.S. (CHC Definitions): Broad and narrow ability definitions and updates. IAPsych CHC Definitions.
  • Conway, A.R.A. et al. (2003): Working memory capacity and its relation to general intelligence. PubMed.
  • D'Esposito, M. & Postle, B.R. (2015): The neural basis of working memory. Nature Reviews Neuroscience.
  • Salthouse, T.A. (2004): Age-related changes in cognitive abilities and processing speed. ScienceDirect.
  • Deary, I.J., Penke, L. & Johnson, W. (2010): The neuroscience of human intelligence differences. Nature Reviews Neuroscience. DOI: 10.1038/nrn2793.
  • AERA, APA, & NCME (2014): Standards for Educational and Psychological Testing. APA Standards.