Short for a ‘general (ability) factor’, it contributes to the observed correlations among many measures of cognitive ability and thereby constitutes one way of conceptualizing general intelligence. It first appeared in a paper published by Charles Spearman (1863-1945) in 1904. Based on his analysis of the performance of school-aged children on a wide variety of tests, he concluded that because the resultant measures were positively correlated there must be an underlying ‘g’ factor that accounts for their associations. Thus was born his two-factor theory of intelligence, and which led to the application of factor analysis in psychology. According to this theory, there is not only a ‘g’ factor, but also a number of specific factors (‘s’ factors) that have low correlations among them. Over the years, the theory has engendered vigorous debate about the nature of human intelligence. One of its severest critics was Stephen Jay Gould in his book The mismeasure of man (1981) in which he claimed that the ‘g’ factor had been reified as physically residing in the brain, and also that there are a number of factor analytical solutions of test data that do not yield a ‘g’ factor. His claims have been regarded by some also as a form of dogma. There is also a debate about whether a ‘g’ factor is also evident in other animals as revealed in performances, for example, of mice, rhesus monkeys and rats on a variety cognitive tasks.
See Crystallized intelligence, Factor analysis, Fluid intelligence, Intelligence, Learning disability, Reification, Theory of multiple intelligences, Triarchic theory of Intelligence