The concepts of fluid intelligence (gf) and crystallized intelligence (gc) were introduced in 1963 by the psychologist Raymond Cattell.[1][2] According to Cattell's psychometrically-based theory, general intelligence (g) is subdivided into gf and gc. Fluid intelligence is the ability to solve novel reasoning problems and is correlated with a number of important skills such as comprehension, problem-solving, and learning.[3] Crystallized intelligence, on the other hand, involves the ability to deduce secondary relational abstractions by applying previously learned primary relational abstractions.[4]
^Cattell, R. B. (1963). "Theory of fluid and crystallized intelligence: A critical experiment". Journal of Educational Psychology. 54: 1–22. doi:10.1037/h0046743.