The basic power of reasoning and problem solving according to Raymond B. Cattell. Fluid intelligence can also be described as mental flexibility and involves the type of intelligence needed to solve problems quickly, perceive relationships among patterns, remember newly acquired information, form and recognize concepts, and reason abstractly and rapidly. Crystallized intelligence, in contrast, is a specific and often fact-based knowledge gained as a result of applying fluid intelligence. Fluid intelligence declines with age, while crystallized intelligence shows less decline and may even improve in certain areas (e.g., increased vocabulary). For more information, see Cattell (1987).