Intelligence, IQ, and g

Intelligence, IQ, and g are very different. Intelligence is the term used in ordinary discourse to refer to cognitive ability.

However, it is usually regarded as too imprecise to be useful for a scientific treatment of the subject. The intelligence quotient (IQ) is an index calculated from the scores on analysis items judged by experts to encompass the abilities coverd by the term intelligence.

IQ measures a multidimensional magnitude: it is an amalgam of dissimilar kinds of abilities, the proportions of which may differ between IQ tests.

The dimensionality of IQ scores can be premeditated by factor analysis, which reveals a single dominant factor underlying the scores on all IQ tests.

This factor, which is a hypothetical construct, is called g. Variation in g corresponds very much to the intuitive notion of intelligence, and thus g is sometimes called general cognitive ability or general intelligence.