Fluid & Crystallized Intelligence

British psychologist Raymond Cattell in the early 1940s introduced the concepts of fluid and crystallized intelligence. Cattell defined fluid intelligence as the ability to reason, analyze, and solve novel problems. Innovators typically have an abundance of fluid intelligence. It is highest relatively early in adulthood and diminishes starting in one’s 30s and 40s. Crystallized intelligence, in contrast, is the ability to use knowledge gained in the past. Think of it as possessing a vast library and understanding how to use it. It is the essence of wisdom. Because crystallized intelligence relies on an accumulating stock of knowledge, it tends to increase through one’s 40s, and does not diminish until very late in life. Careers that rely primarily on fluid intelligence tend to peak early, while those that use more crystallized intelligence peak later. 

Arthur C. Brooks writing in The Atlantic