Fluid intelligence (gf) is the ability to solve novel reasoning problems and is correlated with a number of important skills such as comprehension, problem-solving, and learning.
Crystallized intelligence (gc), on the other hand, involves the ability to deduce secondary relational abstractions by applying previously learned primary relational abstractions
Fluid intelligence (gf) involved basic processes of reasoning and other mental activities that depend only minimally on prior learning, such as formal and informal education, and acculturation.
Measuring fluid reasoning require the ability to solve abstract reasoning problems: figure classifications, figural analyses, number and letter series, matrices, and paired associates.
Crystallized intelligence (gc) includes learned procedures and knowledge.
Crystallized intelligence (gc) reflects the effects of experience and acculturation.
Crystallized intelligence (gc) results from experience from the prior application of fluid ability that has been combined with the intelligence of culture: vocabulary, general information, abstract word analogies, and the mechanics of language.
Fluid intelligence is a predictor of a person’s capacity to work in environments characterised by complexity, uncertainty, and ambiguity.
Fluid intelligence measured in childhood predicts labor market earnings.
Fluid intelligence peaks at around age 20 and then gradually declines.
This decline may be related to local atrophy of the brain in the right cerebellum, a lack of practice, or the result of age-related changes in the brain.
Crystallized intelligence typically increases gradually, stays relatively stable across most of adulthood, and then begins to decline after age 65.
The exact peak age of cognitive skills remains elusive.
Working memory capacity is related to fluid intelligence.
Working memory capacity suggested to account for individual differences in gf.
gf and gc suspected to be involved with 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.
Memory training programs appear to produce short-term, specific training effects that do not generalize.
Thus the balance of findings suggests that training for the purpose of increasing working memory can have specific short-term effects but no effects on gf.