Advanced interpretation of WAIS-IV. The application of the CHC model to a WAIS-IV protocol

A relevant change occurs with the publication of the fourth generation Wechsler Scales (WPPSI-IV, WISC- IV and WAIS-IV), determined by the different theories of cognitive neuroscience based on clinical and neuropsychological research. The first confirmatory factor analyses conducted on the US and Italian standardization samples of the WAIS-IV show the same four-factor structure. The WAIS-IV, in particular, allows the calculation of four indices (or factors): Verbal Comprehension Index (VCI), Perceptual Reasoning Index (PRI), Working Memory Index (WMI) and Processing Speed Index (PSI). Each of the indices contributes to the total composite score or Intellectual Quotient. However, at the end of the last century, numerous models of intelligence appeared, some of which led to the creation of new tools for assessing the construct or updating existing ones, and subsequent U.S. and Italian research have shown that the WAIS-IV data can also be read in the light of the Cattell, Horn, Carroll theory of intelligence (or CHC theory) distinguishing 5 factors: Crystallized Intelligence (Gc); Visual Processing (Gv); Fluid Intelligence (Gf); Short-Term Memory (Gsm); Processing Speed (Gs). The objective of this paper is to highlight through a clinical case the usefulness of using the five-factor CHC model instead of the four-factor model, particularly when one of the first factors is not interpretable as a unitary and cohesive ability.