The Dark Core of Personality

Over 100 years ago Charles Spearman made two monumental discoveries about human intelligence. First, a general factor of intelligence (g) exists: people who score high on one test of intelligence also tend to score high on other tests of intelligence. Second, Spearman found that the g-factor conforms to the principle of the "indifference of the indicator": It doesn't matter what test of intelligence you administer; as long as the intelligence test is sufficiently cognitively complex and has enough items, you can reliably and validly measure a person's general cognitive ability.
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