Fluid Intelligence

History

Early research in intelligence proposed that intelligence was composed of a single, unitary characteristic (known as general intelligence, or g) and a relatively large number of specific abilities. Whereas g was viewed as broad ability having a profound effect on learning, problem solving, and adaptation, specific abilities were viewed as narrow and largely trivial. However, subsequent research differentiated intellectual abilities that were based, in large part, on culturally specific, acquired knowledge (known as crystallized abilities, or gc) and intellectual abilities that were less dependent on prior knowledge and cultural experiences (known as fluid abilities, or gf). Although this work was primarily influenced by factor analysis of relationships among cognitive tests, prediction of future learning, experimental studies, and other forms of evidence also supported the crystallized versus fluid distinction. More modern research has identified other abilities in addition to crystallized and fluid abilities (e.g., working memory, quantitative reasoning, visualization), although scholars have not yet agreed on the exact number and nature of these abilities and whether these abilities are independent faculties or subordinate to g. In contrast, there is strong consensus on the distinction between fluid and crystallized intellectual abilities and their substantial roles in human learning and adaptation.

Nature

Contemporary neuroscience defines fluid intelligence as cognitive processing independent of specific content. Fluid intelligence is characterized by the ability to [Page 407]suppress irrelevant information, sustain cognitive representations, and manage executive processes. Measures of fluid intelligence are strong predictors of cognitively demanding tasks, including learning, education, vocational performance, and social success, particularly when such performance demands new learning or insight rather than reliance on previous knowledge.

Research also suggests strong biological influences on the development of, and individual differences in, fluid intelligence. For example, studies demonstrate that (a) fluid intelligence is more heritable than most other cognitive characteristics; (b) localization of fluid intelligence operations in the prefrontal cortex, anterior cingulate cortex, amygdala, and hippocampus; (c) life-span changes associating neurotransmitter decreases with decrements in fluid intelligence; (d) moderate associations between neural speed of response/ conduction and (untimed) measures of fluid intelligence; (e) that unusual exposure to language (e.g., deafness, nonstandard language background) has little effect on the development and performance of fluid intellectual abilities; and (f) fluid abilities have been rising steadily in Western countries for over a century in contrast to relatively stable crystallized abilities (i.e., the Flynn effect). Although there is an association between environmental advantages (e.g., parental education, socioeconomic status) and fluid intelligence, this association may be partly or entirely explained by gene-environment correlations. There is little evidence to suggest that deliberate environmental interventions (e.g., compensatory education programs) substantially influence fluid intelligence, although such programs may have at least short-term effects on crystallized intelligence.

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