and crystallized intelligence
, respectively) are factors of general intelligence
originally hypothesized by Raymond Cattell
intelligence is the ability to find meaning in confusion and solve new problems. It is the ability to draw inferences and understand the relationships of various concepts, independent of acquired knowledge. Crystallized
intelligence is the ability to use skills, knowledge, and experience. It should not be equated with memory or knowledge, but it does rely on accessing information from long-term memory. The two "forms" of intelligence are believed to be separate neural and mental systems.
Fluid and crystallized intelligence are 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 (Lee, et al., 2005).
Fluid and crystallized intelligence are described as discrete factors of general intelligence
, or g
(Cattell, 1987). Charles Spearman
(1927), who originally developed the theory of the g
, made a similar distinction between eductive and reproductive mental ability. It should be noted that Spearman's original work was harshly criticized and refuted by Alfred Binet
In his critique, Binet goes as far as to say that Spearman actually fabricated his data, or at the least manipulated the data to support his hypothesis. In any case, Cattell (1987) continued Spearman's work and developed the concepts of fluid and crystallized intelligence. According to Cattell (1987), "...it is apparent that one of these powers… has the 'fluid' quality of being directable to almost any problem. By contrast, the other is invested in particular areas of crystallized skills which can be upset individually without affecting the others." Thus, his claim was that each type, or factor, was independent of the other, though many authors have noted an apparent interdependence of the two (Cavanaugh & Blanchard-Fields, 2006).
Fluid versus crystallized
Fluid intelligence includes such abilities as problem-solving, learning, and pattern recognition. As evidence for its continuity, Cattell suggests that gF abilities are rarely affected by brain injuries. The Cattell Culture Fair IQ test, the Raven Progressive Matrices, and the performance subscale of the WAIS are measures of gF.
Crystallized intelligence is possibly more amenable to change as it relies on specific, acquired knowledge. For example, a child who has just learned how to recite the fifty states of America now owns a new piece of crystallized intelligence; but his or her general ability to learn and understand gF has not been altered. An example of the flexibility, or ability to revise, crystallized intelligence can be seen in beliefs about Santa Claus. A five year-old child may believe that Santa Claus lives at the North Pole. Later, when the child is eight years old, he learns there is no Santa Claus. His belief that Santa lives at the North Pole was then invalidated and new knowledge is gained, there is no Santa Claus. The prior knowledge was revised in order to accommodate the new learning. Vocabulary tests and the verbal subscale of the WAIS are considered good measures of gC.
Not surprisingly, people with a high capacity of gF tend to acquire more gC knowledge and at faster rates. This is sometimes called investment. Researchers have found that criminals have disproportionately low levels of crystallized intelligence. This may be a result of these people investing their ability into skills that are not measured on IQ tests.
Fluid intelligence generally correlates with measures of abstract reasoning and puzzle solving. Crystallized intelligence correlates with abilities that depend on knowledge and experience, such as vocabulary, general information, and analogies. Paul Kline (1998) identified a number of factors that shared a correlation of at least r=.60 with gF and gC. Factors with median loadings of greater than 0.6 on gF included induction, visualization, quantitative reasoning, and ideational fluency. Factors with median loadings of greater than 0.6 on gC included verbal ability, language development, reading comprehension, sequential reasoning, and general information. It may be suggested that tests of intelligence may not be able to truly reflect levels of fluid intelligence. Some authors have suggested that unless an individual was truly interested in the problem presented, the cognitive work required may not be performed because of a lack of interest (Messick 1989, 1995). These authors contend that low scores on tests that measure fluid intelligence may reflect more of a lack of interest in the tasks rather than the ability to complete the task successfully.
Development and physiology
Fluid intelligence, like reaction time
, peaks in young adulthood and then steadily declines. Cavanaugh and Blanchard-Fields (2006) indicate that it increases gradually, stays relatively stable across most of adulthood, and then begins to decline after age 65, and that a lack of practice, along with the age-related change in the brain may contribute to the decline. It's been speculated that working memory
capacity is closely related to gF. Research on exercising working memory appears to lend some support to the idea that it can help maintain or improve gF, though it's also possible that what these same exercises are strengthening is actually the power of attention, a gF factor proposed by Spearman.
According to recent research, gF and gC can be traced to two separate brain systems. Fluid intelligence involves the dorsolateral prefrontal cortex, the anterior cingulate cortex, and other systems related to attention and short-term memory. Crystallized intelligence appears to be a function of brain regions that involve the storage and usage of long-term memories, such as the hippocampus (Geary, 2005). Not all researchers have replicated these findings, however (Lee, et al. 2005).
- Cattell, R. B. (1971). Abilities: Their structure, growth, and action. New York: Houghton Mifflin. ISBN 0395042755.
- Cavanaugh, J.C., & Blanchard-Fields, F (2006). Adult development and aging (5th ed.) Belmont, CA: Wadsworth Publishing/Thomson Learning. ISBN 0534520669.
- Cattell, R. B. (1987). Intelligence: Its structure, growth, and action. New York: Elsevier Science Pub. Co.
- Carroll, J. B. (1993). Human cognitive abilities: A survey of factor-analytic studies. New York: Cambridge University Press. ISBN 9780521387125.
- Geary, D. C. (2005). The origin of mind: Evolution of brain, cognition, and general intelligence. Washington, DC: American Psychological Association.
- Kline, P. (1998). The new psychometrics: Science, psychology and measurement. London: Routledge.
- Lee, J., Lyoo, I., Kim, S., Jang, H., Lee, D., et al. (2005). Intellect declines in healthy elderly subjects and cerebellum. Psychiatry and Clinical Neurosciences, 59, 45-51.
- Messick, S. (1989). Meaning and values in test validation: The science and ethics of assessment. Educational Researcher, 18, 5–11.
- Messick, S. (1995). Validity of psychological assessment. American Psychologist, 50, 741–749.