GF-GC Theory of Intelligence

There are a number of widely known and respected theories of human intelligence (e.g., Howard Gardner's [Page 404]Theory of Multiple Intelligences, Robert Sternberg's Tir-archic Theory of Intelligence), but in recent years, the Gf-Gc theory has become increasingly important in the field of intellectual assessment. This is at least partially due to the fact that the Gf-Gc theory is based on factor analytical studies of the results from IQ tests. Many of the other theories, although intriguing, do not have a means of actually measuring their constructs in an individual.

In the early 1900s, Charles Spearman applied statistical analyses to the concept of mental ability and arrived at the conclusion that there is one general factor (g) that is related to all aspects of intelligence. Although this is expressed in many different ways, underlying it all is one thing that we think of as intelligence. This concept took root and is the basis for the single IQ score that was generated with early measures of intelligence and, although controversial, continues to be reflected in the Full Scale IQ or similar score found on most measures of cognitive ability today.

It was not until the 1940s that Raymond Cattell, building on Spearman's work, proposed the existence of two general types of intelligence: fluid intelligence (Gf) and crystallized intelligence (Gc). Fluid intelligence was related to biological and neurological factors and is exemplified by inductive and deductive reasoning. Although experience may influence it indirectly (e.g., introduction of new paradigms allows for different ways of organizing problems), it is not dependent upon learned information. Conversely, crystallized intelligence was seen as being the direct result of experience, learning, and education, and was relatively free from the influence of biological and neurological factors. This dichotomy was frequently thought of loosely as innate and learned abilities, right and left hemisphere abilities, or nonverbal and verbal abilities, respectively. Although useful conceptually, these alternative ways of thinking about the two types of intelligence were not fully supported by the research and remain controversial at best.

In the early 1980s, John Horn, using the decades of factor analytic research on human cognitive abilities since Cattell's original postulation, added to the original Gf-Gc theory to form what became known as the Cattell-Horn Gf-Gc theory of intelligence. This new theory contained 9 to 10 broad abilities by the mid-1990s and began to be used more and more as a basis for interpreting the results of intelligence tests.

At this same time, John Carroll conducted a meta-analysis of more than 400 different data sets that had been collected from 1925 on. He looked at the raw scores, conducted exploratory factor analyses, and concluded that the results fit a hierarchical three-stratum model: 69 narrow abilities at the first level; 8 broad abilities (that roughly corresponded to the broad abilities articulated by Horn-Cattell) at the second level; and a general factor, g, above them all at the third level. Subsequently, these two models were merged by Kevin McGrew and others to form the Cattell-Horn-Carroll (CHC) theory of cognitive abilities. CHC theory and Gf-Gc theory are now essentially analogous.

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