<P> The terms are somewhat misleading because one is not a "crystallized" form of the other . Rather, they are believed to be separate neural and mental systems . Crystallized intelligence is indicated by a person's depth and breadth of general knowledge, vocabulary, and the ability to reason using words and numbers . It is the product of educational and cultural experience in interaction with fluid intelligence . </P> <P> Fluid and crystallized intelligence are thus correlated with each other, and most IQ tests attempt to measure both varieties . For example, the Wechsler Adult Intelligence Scale (WAIS) measures fluid intelligence on the performance scale and crystallized intelligence on the verbal scale . The overall IQ score is based on a combination of these two scales . </P> <P> Fluid and crystallized intelligence were originally identified by Raymond Cattell . Concepts of fluid and crystallized intelligence were further developed by Cattell's student, John L. Horn . Since Cattell's and Horn's publications, the concepts of fluid and crystallized intelligence have become so ingrained in the field of intelligence that they are no longer routinely attributed to Cattell or Horn--much as Cattell's scree plot became ingrained in the practice of factor analysis or Freud's concept of the subconscious is ingrained in psychology and in the public's perceptions of the mind . </P> <P> Fluid and crystallized intelligence are discrete factors of general intelligence, or g . Although formally recognized by Cattell, the distinction was foreshadowed by Charles Spearman who originally developed the theory of g and made a similar observation regarding the difference between eductive and reproductive mental ability . </P>

Who came up with the theory of crystallized vs fluid intelligence