Fluid and crystallized intelligence

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In psychology, fluid and crystallized intelligence (abbreviated gF and gC, respectively) are factors of general intelligence originally identified by Raymond Cattell.[1] Fluid 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 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.

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. The overall IQ score is based on a combination of these two scales.

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[edit] Theoretical development

Fluid and crystallized intelligence are discrete factors of general intelligence, or g.[2] 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.[citation needed]

According to Cattell, "...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."[3] 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.[4]

[edit] 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 of, 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.[citation needed] Researchers have found that criminals have disproportionately low levels of crystallized intelligence.[citation needed] This may be a result of these people investing their ability into skills that are not measured on IQ tests.

[edit] Factor structure

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 identified a number of factors that shared a correlation of at least r=.60 with gF and gC.[5] 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.[6] 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.

[edit] Development and physiology

Fluid intelligence, like reaction time, peaks in young adulthood and then steadily declines. This decline may be related to local atrophy of the brain in the right cerebellum.[7] Other researchers have suggested that a lack of practice, along with age-related changes in the brain may contribute to the decline.[8] Crystallized intelligence increases gradually, stays relatively stable across most of adulthood, and then begins to decline after age 65.[9]

Working memory capacity is closely related to fluid intelligence, and has been proposed to account for individual differences in gF.[10] Furthermore, recent research suggests that cognitive exercise can increase working memory and also improve gF. Preliminary experiments found that healthy young adults who practiced a demanding working memory task (dual n-back) approximately 25 minutes per day for between 8 and 19 days had statistically significant increases in their scores on a matrix test of fluid intelligence taken before and after the training than a control group who did no not do any training at all.[11] As of now, it remains to be seen whether the results extend to other kinds of fluid intelligence tests, and if so, whether, after training, fluid intelligence measures retain their correlation with educational and occupational achievement or if the value of fluid intelligence for predicting performance on other tasks changes; it is also unclear whether the training is durable of extended periods of time.[12]

According to David Geary, 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.[13]

[edit] See also

[edit] References

  1. ^ Cattell, R. B. (1971). Abilities: Their structure, growth, and action. New York: Houghton Mifflin. ISBN 0395042755.
  2. ^ Cattell, R. B. (1987). Intelligence: Its structure, growth, and action. New York: Elsevier Science Pub. Co.
  3. ^ Cattell, R. B. (1987). Intelligence: Its structure, growth, and action. New York: Elsevier Science Pub. Co.
  4. ^ Cavanaugh, J.C., & Blanchard-Fields, F (2006). Adult development and aging (5th ed.) Belmont, CA: Wadsworth Publishing/Thomson Learning. ISBN 0534520669.
  5. ^ Kline, P. (1998). The new psychometrics: Science, psychology and measurement. London: Routledge.
  6. ^ 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.
  7. ^ Lee, J., Lyoo, I., Kim, S., Jang, H., & Lee, D. (2005). Intellect declines in healthy elderly subjects and cerebellum. Psychiatry and Clinical Neurosciences, 59, 45-51.
  8. ^ Cavanaugh, J.C., & Blanchard-Fields, F (2006). Adult development and aging (5th ed.) Belmont, CA: Wadsworth Publishing/Thomson Learning. ISBN 0534520669.
  9. ^ Cavanaugh, J.C., & Blanchard-Fields, F (2006). Adult development and aging (5th ed.) Belmont, CA: Wadsworth Publishing/Thomson Learning. ISBN 0534520669.
  10. ^ Kyllonen, P. C., & Christal, R. E. (1990). "Reasoning ability is (little more than) working-memory capacity?!" Intelligence, 14, 389–433.
  11. ^ Jaeggi, Susanne M.; Buschkuehl, Martin; Jonides, John; and Perrig, Walter J. (2008). "Improving fluid intelligence with training on working memory." PNAS- Proceedings of the National Academy of Sciences. [1]
  12. ^ R.J. Sternberg (2008). "Increasing fluid intelligence is possible after all (Commentary)". Proc. Natl. Acad. Sci. U.S.A. 105 (19): 6791-6792. 
  13. ^ Geary, D. C. (2005). The origin of mind: Evolution of brain, cognition, and general intelligence. Washington, DC: American Psychological Association.
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