— Cognitive science

Three-Stratum Theory

Term

Carroll model

Domain

Cognitive psychology

First introduced

20th century

IQ relevance

Direct

Three-Stratum Theory (Carroll model) refers to Carroll's hierarchical model: g at top, broad abilities in middle, narrow abilities at bottom. The concept is central to modern cognitive psychology and psychometrics — particularly to how IQ is theorized, measured, and interpreted.

What three-stratum theory actually means

In cognitive psychology, three-stratum theory is operationalized as Carroll's hierarchical model: g at top, broad abilities in middle, narrow abilities at bottom. It is distinct from related constructs in that it specifically captures a distinct, measurable aspect of cognitive function.

How it's measured

Measured through standardized testing batteries and laboratory paradigms specific to the construct.

Relationship to IQ

Three-Stratum Theory is integrated into the broader theory of IQ and cognitive function. It contributes to and is partially measured by composite IQ scores.

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Why this matters

Understanding three-stratum theory is foundational for anyone trying to interpret an IQ score meaningfully. The single composite IQ number conceals significant variation across cognitive functions; understanding the components is how you go from "I scored 130" to "I scored 130, with particular strength in [X] and relative weakness in [Y]."

Frequently asked

What is three-stratum theory?

Three-Stratum Theory (Carroll model) refers to Carroll's hierarchical model: g at top, broad abilities in middle, narrow abilities at bottom. It is a central concept in cognitive psychology and IQ measurement.

How is three-stratum theory different from general IQ?

Composite IQ is a weighted aggregate of multiple cognitive abilities. Three-Stratum Theory is one specific component or property that contributes to but is not identical to the IQ score.

Can three-stratum theory be improved?

Generally limited room for improvement in trait-level cognitive properties; significant variability in measured performance day-to-day.