In over 30 years of extensive research (1, 2), Raymond Cattell and colleagues identified that general intelligence could be split into two highly correlated subtypes of mental ability- crystallised intelligence and fluid intelligence.
Crystallised intelligence is the ability to use knowledge and skills that have been acquired through experience. This type intelligence correlates with measures of abilities such as vocabulary, general knowledge, verbal and numerical reasoning, and analogies. It therefore reflects the type of culture and education to which the individual has been exposed.
However, crystallised intelligence is also affected by what many psychologists consider to be intellignece in its purest form- fluid intelligence. This is the ability to analyse new problems using logic to identify their underlying patterns and relationships. It enables an individual to draw inferences and recognise relationships between different concepts and according to Cattell (4) it can be applied to almost any problem. Another important feature of fluid intelligence is that, according to research, it is relatively independent of educational experience (3) and strongly influenced by genetic factors.
After a peak in early adulthood, fluid intelligence steadily declines. This could be due to factors such deterioration and age-related change in the brain combined with lack of practice.
Progressive Matrices
Fluid intelligence includes abilities such as pattern recognition, learning and problem-solving. Abstract reasoning tests are therefore widely considered to be the best way to assess the construct. Tests like the Ravens, the Norwegian matrices, the Belgian Shapes test, the Jenkins test, and the Horn test all attempt to measure fluid intelligence.
Progressive matrices, originally developed by Dr John Raven (5), are multiple choice abstract reasoning tests which ask candidates to identify the missing segment required to complete a larger pattern. The name originates from the fact that most test items are 3x3 or 2x2 matrices. Tests are availble in different forms such as standard, coloured (aimed at children) and advanced. All become increasingly difficult as the candidate progresses through the items.
Tests of fluid intelligence try to encourage problem solving and minimise the need for learned skills. An interesting finding, however, is that results have increased over time at a rate of approximately 15 points per generation (6). Is mankind becoming more intelligent?
1. Cattell, R.B. (1941). Some theoretical issues in adult intelligence testng. Psychological Bulletin, 38, 592.
2. Cattell, R. B. (1971). Abilities: Their structure, growth, and action. New York: Houghton Mifflin.
3. Cavanaugh, J.C., & Blanchard-Fields, F (2006). Adult development and aging (5th ed.) Belmont, CA: Wadsworth Publishing/Thomson Learning.
4. Cattell, R. B. (1987). Intelligence: Its structure, growth, and action. New York: Elsevier Science Pub. Co.
5. Raven, J.C. (1938). Progressive matrices: A perceptual test of intelligence. London:H.K. Lewis
6. Flynn, J. R. (1987). Massive IQ gains in 14 nations: What IQ tests really measure. Psychological Bulletin, 101,171-191.
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