who came up with the theory of crystallized vs fluid intelligence
Fluid and crystallized intelligence Fluid and crystallized intelligence were originally identified by Raymond Cattell.[3] 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 Hornâ€”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.