There is no hard and fast consensus in the academic literature about how many different types of intelligence exist. In the early twentieth Century, the English psychologist Charles Spearman observed that a general factor (G or g factor), served to explain much of the consistency in baseline performance of an individual across a multitude of intelligence tests. In simple terms, the g-factor could therefore be likened to a global or general intelligence. The higher someone’s G, the better they were likely to perform across a variety of IQ tests, even though each of these might measure a different aspect of human intellect. Spearman also believed that people possess specific or special abilities, but that G was more closely related to the concept of general intelligence. Spearman could therefore be viewed as a proponent of the single, global IQ score.
Cattell proposed two different types of intelligence
Spearman’s doctoral student Raymond Cattell in the 1940s decomposed his mentor’s theory of G into two principal components: (1) Fluid Intelligence (Gf); and (2) Crystallized intelligence (Gc). Fluid intelligence represents an individual’s ability to solve ‘novel’ or new problems. Crystallized intelligence on the other hand, is the aspect of human intelligence that can be learned in school. So Gf can be likened to raw processing power of the brain, while Gc is closer to a body of knowledge. This is often known as Gc-Gf theory.
Cattell’s theoretical foundation of human intelligence did not gain prominence until the 1960s, when his doctoral student John Horn decided to re-popularize his mentor’s forgotten Gc-Gf theory. This theory was eventually merged with that of John Carroll, which resulted in what is widely known as CHC theory of cognitive abilities.
CHC theory further dissects G, and Gf-Gf to include seven broad abilities including:
- Quantitative reasoning (Gq)
- Reading and writing ability (Grw)
Gf-related sub indexes:
- Short-term memory (Gsm)
- Long-term storage and retrieval (Glr)
- Visual processing (Gv)
- Auditory processing (Ga)
- Processing speed (Gs)
CHC is today the most widely accepted theory of intelligence with several of the major professional IQ tests having been reviewed to incorporate test items to measure several of these broad abilities. Well-known tests such as the Stanford-Binet V and Weschler Adult Intelligence Scales IV typically incorporate four of the seven broad abilities:
Factor indexes (different types of intelligence) of WAIS-IV:
- Verbal comprehension index (Gc)
- Perceptual reasoning index (Gv / Gf)
- Working memory index (GSm)
- Processing speed index (Gs)
Glr and Ga may be difficult to measure in a short IQ test. Nonetheless, it becomes clear that there are different types of intelligence.
Although G is perhaps an overly simplistic concept, it still resonates in society with the global IQ score being given significant consideration. However, it is important to realize that Global intelligence can be decomposed into different types of intelligence as shown above.
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