CHC theory organizes intelligence into three strata
CHC theory—the Cattell–Horn–Carroll theory—describes intelligence in three strata: a general ability shared across many intellectual tasks, broad abilities covering major domains, and narrower, more specific processes. Cattell distinguished fluid and crystallized intelligence, Horn expanded the model to memory, visual processing, processing speed, and other abilities, and Carroll organized a large body of research into these three strata.
| Stratum | What it represents | Example |
|---|---|---|
| Stratum III: general ability | Overall ability shared across many intellectual tasks | g factor |
| Stratum II: broad abilities | Major domains such as knowledge, reasoning, visuospatial processing, memory, and speed | Gc, Gf, Gv, Gwm, Gs |
| Stratum I: narrow abilities | More specific processes within a broad ability | Vocabulary knowledge, induction, visualization, perceptual speed |
Within this model, finding a rule in an unfamiliar sequence of figures is described at three levels: g at the highest stratum, Gf at the broad-ability stratum, and induction at the narrow-ability stratum. The g factor and IQ explains the highest level in more detail.
What Gc, Gf, Gv, Gwm, and Gs represent
Broad abilities at Stratum II are central to understanding a cognitive profile.
| Ability | Central ability | Example |
|---|---|---|
| Gc: crystallized intelligence | Use knowledge gained through learning and experience | Explain a word or express the relationship between concepts |
| Gf: fluid reasoning | Discover relationships and rules in unfamiliar problems | Find a rule in a figure sequence or derive a conclusion from conditions |
| Gv: visuospatial processing | Understand and mentally transform shapes and spatial relationships | Rotate a shape or imagine a whole from its parts |
| Gwm: working memory | Hold information temporarily while using it to think | Reverse digits or calculate while retaining several conditions |
| Gs: processing speed | Process relatively simple, repeated information quickly and accurately | Compare symbols and find a match within a time limit |
CHC theory also includes broad abilities such as auditory processing, learning, long-term retrieval, reading, and writing.
The same overall IQ can come from different ability combinations
Overall IQ combines performance across several cognitive tasks. People with similar overall IQ scores can therefore have different ability profiles.
A person with stronger verbal comprehension and reasoning but relatively lower working memory and processing speed may understand complex material yet experience more demand when several conditions must be retained and processed quickly. A person with stronger visuospatial processing may grasp a diagram or layout more readily than a verbal explanation alone.
CHC theory describes both the general level represented by overall IQ and the ability differences within it. Understanding cognitive profiles connects these combinations to work, conversation, and learning.
How WAIS indexes relate to CHC theory
In WAIS-IV, VCI is closely related to Gc, WMI to Gwm, and PSI to Gs, while PRI combines tasks that place greater weight on Gf and Gv. Matrix Reasoning is primarily a fluid-reasoning task, whereas Block Design places greater weight on visuospatial processing.
WAIS-5 separates the former PRI into a Visual Spatial Index and a Fluid Reasoning Index. How CHC abilities relate to WAIS explains the subtest mapping and the changes between WAIS-IV and WAIS-5.
The five abilities measured by BrainTypeIQ
BrainTypeIQ uses nine tasks to measure Gc, Gf, Gv, Gwm, and Gs. These are five selected CHC domains used to construct overall IQ and a cognitive profile, not every broad ability in CHC theory.
The nine-task, five-domain measurement design explains how the tasks map to the five abilities. You can complete all nine tasks and receive your overall IQ and brain type report for free. The detailed report includes the five domain scores, nine task scores, GAI, and CPI.