What is fluid intelligence?

Fluid intelligence (Gf) is the ability to solve novel problems, reason abstractly, and think flexibly without relying on prior knowledge.

What is crystallized intelligence?

Crystallized intelligence (Gc) is knowledge acquired through education and experience, including vocabulary, facts, and procedural skills.

Fluid intelligence peaks in early adulthood and declines gradually; crystallized intelligence increases through midlife and declines less.

Understanding both types helps explain cognitive aging, learning differences, and the multidimensional nature of intelligence.

Peter Kolomiets

|March 28, 2026|Updated Apr 13, 2026|7 min read

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Cattell, R. B.. Cattell, R. B. (1963). Theory of Fluid and Crystallized Intelligence
Horn, J. L. & Cattell, R. B.. Horn, J. L. & Cattell, R. B. (1967). Age Differences in Fluid and Crystallized Intelligence
Salthouse, T. A.. Salthouse, T. A. (2004). Localizing Age-Related Individual Differences in a Hierarchical Structure

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The g factor represents general intelligence underlying all cognitive abilities. It explains why people who excel in one domain often excel broadly.

Fluid intelligence peaks around age 20, then declines; crystallized intelligence increases until midlife. Overall IQ remains relatively stable.

Peter Kolomiets

|March 28, 2026|Updated Apr 13, 2026|7 min read

Ready to discover your Iq Test?

Cattell, R. B.. Cattell, R. B. (1963). Theory of Fluid and Crystallized Intelligence
Horn, J. L. & Cattell, R. B.. Horn, J. L. & Cattell, R. B. (1967). Age Differences in Fluid and Crystallized Intelligence
Salthouse, T. A.. Salthouse, T. A. (2004). Localizing Age-Related Individual Differences in a Hierarchical Structure