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What is the g factor?
The IQ score you get from a standardized IQ test is a measure of the g factor (or simply g)- so let’s first be clear about what this is.
The psychologist Charles Spearman in the early 1900s saw that scores across seemingly unrelated subjects – from history to languages to science – were all positively correlated. Scores tended to rise and fall together. Generally, if someone scored above average on one test, they would score above average on other tests. He called this the positive manifold.
The positive manifold is a well-established fact. Statistically speaking, performance on all cognitively demanding tests with different content – from languages to math, from GCSEs or SATs to music theory exams – are positively correlated.
Spearman explained the positive manifold by a general ability factor (g) common to scores on all cognitive tasks. The terms IQ, general intelligence, general ability and g, are used interchangeably to refer to this common core.
Definitions of general intelligence (g factor)
Here are some working definitions of general intelligence – measured by IQ tests.
A consensus-definition of fifty-two intelligence researchers defines intelligence as:
the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience. It is not merely book learning, a narrow academic skill, or test-taking smarts. Rather, it reflects a broader and deeper capability for comprehending our surroundings —”catching on,” “making sense” of things, or “figuring out” what to do.
From artificial intelligence (AI) we get these definitions of intelligence:
Achieving complex goals in complex environments. B. Goertzel
And
Intelligence is the ability to use optimally limited resources – including time – to achieve goals. R. Kurzweil
And in the context of our careers and professional lives we have these definitions of intelligence:
I prefer to refer to it as ‘successful intelligence.’ And the reason is that the emphasis is on the use of your intelligence to achieve success in your life. So I define it as your skill in achieving whatever it is you want to attain in your life. R. Sternberg
For more definitions of the g factor and general intelligence, this is an excellent resource.
Fluid Intelligence = IQ
The well-established CHC (Cattell-Horn-Carroll) theory of general intelligence uses a statistical technique called factor analysis to reveal a second level of ‘broad ability’ subfactors below the g factor. These include visual processing (Gv), comprehension -knowledge (Gc), fluid reasoning (Gf) and processing speed (Gs).
The broad ability with the highest g-loading is fluid intelligence (Gf).
Gf tests – sometimes called ‘culture fair’ IQ tests – such as Raven’s Matrices tests or number/letter series tests (see below) – assess your power of reasoning (inductive and deductive) and your ability to infer patterns, relationships and rules without the need for specialized cultural knowledge or education. These are very general-purpose information processing skills here.
Fluid intelligence tests load predict g-factor scores so well that Gf can be understood as the g-factor itself, and tests of Gf can be used as a substitute for full-scale IQ tests. If you do a matrices or letter series test, you get a good estimate of your general intelligence (g) from this test alone.
References
Legg, S. & Hutter, M. (2007). A Collection of definitions of intelligence. Frontiers in Artificial Intelligence and Applications, Vol.157 (2007) 17-24.
McGrew, K. S. (2009). CHC theory and the human cognitive abilities project: Standing on the shoulders of the giants of psychometric intelligence research. Intelligence, 37(1), 1–10.
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