Human Intelligence
Theory of Fluid and Crystallized Intelligence
Raymond Cattell · 1963 · Journal of Educational Psychology
Distinguished fluid intelligence (novel reasoning) from crystallized intelligence (accumulated knowledge).
Research objective
Refine the structure of g by separating biologically grounded reasoning capacity from experience-dependent knowledge.
Methodology
Factor analysis of cognitive ability tests across age groups, identifying two distinct higher-order factors within g.
Key findings
- Fluid intelligence peaks in early adulthood, then declines.
- Crystallized intelligence increases throughout life until late adulthood.
- The two factors are correlated but functionally distinct.
Strengths
- Reconciled apparent contradictions in age-related cognitive change.
- Influenced the Cattell-Horn-Carroll model, now dominant in psychometrics.
Limitations
- Boundary between the two factors is fuzzy in modern testing.
- Cultural confounds in measuring crystallized intelligence remain.
Practical implications
- Foundation of modern intelligence testing batteries (WAIS, Woodcock-Johnson).
- Informs lifespan cognitive science and expertise research.
Related entities
Related research
'General Intelligence,' Objectively Determined and Measured
Proposed the existence of a general intelligence factor (g) underlying performance across cognitive tasks.
Read summary
Thinking, Fast and Slow (Dual-Process Theory)
Synthesized decades of research into a dual-process model: fast intuitive System 1 and slow deliberative System 2.
Read summary