Structure of the Wechsler Adult Intelligence Scale – Revised in the Italian Normal Standardisation Sample

Six multifactor correlated traits models and a single-factor model of the WAIS-R's factor pattern were examined by confirmatory maximum likelihood factor analyses of a data matrix from the WAIS-R's Italian normative sample raw scores (N=2284). The main aim was to identify what model(s) best fit(s) the data for the different age groups considered. Analyses were designed to determine which of seven hypothesised factor solutions best explained the intellectual ability of four age bands (16 to 74 years of age) and of all samples. Results showed the same three-correlated-factors model (Verbal, Performance, and Freedom From Distractibility) for the younger (16 to 24 years of age) and for more aged (65 to 74 years of age), and two different three-factor models for the adult (band from 25 to 64 years of age) that had in common the presence of Digit Symbol loading on Freedom From Distractibility, that in the younger and aged band loaded on Perceptual Organisation. The individuals may use different strategies when performing a given task on the WAIS-R. Such differences in latent variability may represent real differences in neuropsychological functioning, and as such can account for some of the variability in results noted in the literature. Differences in latent variability across distinct demographic and clinical groups could provide important insight into brain–behaviour relationships.