Increased educational level is related with higher IQ scores but lower g-variance: Evidence from the standardization of the WAIS-R for Italy

The interactive relationship between educational level and IQ scores is still a matter of discussion, mainly because the latter combine the influence of (1) the general factor of intelligence (g), (2) cognitive abilities, and (3) cognitive skills. As underscored by Jensen (1998), among others, it is relevant to know how much of IQ scores is due to g and how much is due to specific abilities and skills. Separating the influence of these components may shed light regarding their relationship with educational level. Here we analyzed the standardization sample of the WAIS-R for Italy (N = 1630). We considered a) measurement invariance across four educational levels, and b) IQ variability and IQ differences due to g (general intelligence), VC (verbal comprehension), PO (perceptual organization), and MFD (Memory/Freedom from Distractibility). Results showed that (a) the WAIS-R provides a valid measure of latent g, (b) individual differences in intelligence are properly measured by IQ scores at different educational levels, (c) there is an average increase equal to 1.9 IQ points in the IQ global composite score per year of education, and (d) the relevance of g decreases at increased educational levels.