The IQ factor: implications for intelligence theoryand measurement

The history of intelligence test development is considered with special reference to thedrift away from verbal tests and to the contemporary assumption that every factor produced bystatistical analysis of cognitive performance variables is an intelligence factor. To test thisassumption of universal test validity the Wechsler Adult Intelligence Scale (WAIS) and RavensAdvanced Progressive Matrices (RAPM) test were administered to 76 subjects, with equalnumbers of males and females and ages representing the whole adult life-span. Principalcomponents analyses (PCA) and multiple linear regression analyses (MLR) demonstrated thatage and sex account for 3% of the variance of IQ scores as compared to 1, 28 and 64% forCattells Gc, Gsar, and Gf factors, respectively. In addition, with IQ as a marker variable, andincluding age and sex, PCA was used to ascertain factor loadings for IQ on the three G factors.The highest loading of 0.77 was found for Gc whereas the loadings for Gsar and Gf were only0.31 and 0.19, respectively. These results support the conclusion that while there are multiplecognitive performance factors there is only one IQ factor and therefore only one validintelligence factor. Theoretical, social and research implications are discussed.