Intelligence, IQ, and g

Intelligence, Intelligence quotient (IQ), and g are distinct. Intelligence is the term used in ordinary discourse to refer to cognitive ability. However, it is generally 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 test items judged by experts to encompass the abilities covered by the term intelligence. IQ measures a multidimensional quantity: it is an amalgam of different kinds of abilities, the proportions of which may differ between IQ tests. The dimensionality of IQ scores can be studied 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 closely to the intuitive notion of intelligence, and thus g is sometimes called general cognitive ability or general intelligence.