The new WAIS-IV scale, published in Italy by Giunti OS in 2013, involves significant and very important structural innovations from previous versions, inaugurated by the 1955 WAIS scale. The WAIS-R scale, universally known in past years as the most accurate and comprehensive scale for measuring intelligence, used internationally, built in the USA in 1981, translated and calibrated in Italy in 1997, was substantially modified with the subsequent WAIS-III in the USA in the same 1997, because in the meantime important innovations in knowledge related to intelligence theory demanded a structural revision. WAIS-III was never translated or calibrated for Italy, as meanwhile the new and current WAIS-IV, published in the US in 2008 and translated and calibrated in Italy in 2013, was already being studied in the US.
These were the reasons for the need for a new scale:
1) the so-called Flynn effect: this consists of the increase in the value of the average IQ of the population over the years, completely independent of the culture to which it belongs. This phenomenon, which has been known since the 1980s and observed in more than 20 different countries, including Italy, has reported that the value of IQ has increased steadily, with an average growth of about 3 points per decade. The U.S. population, for example, gained more than 13 points from 1938 to 1984. This increase affects more subtests that relate to fluid intelligence than to crystallized intelligence and does not depend on school learning (which affects crystallized intelligence more). The Flynn effect results in the need to update the scales periodically. As for Italy, it is known that the same subject, assessed with the very old WAIS and with the less obsolete WAIS-R, based on a more recent normative sample, is found to have an average IQ 8 points lower in the second, more up-to-date WAIS. Essentially, as the average cognitive level of the population progressively rises, not updating normative samples falsifies the results appreciably, and it is also particularly disadvantageous for deficit individuals who are artificially found to be less deficient than they actually are, with the risk that they will lose the socioeconomic protections and safeguards arising from their condition.
2) It has always been observed by leading authors that the WAIS-R scale was insensitive to extreme values of the scale, and therefore unsuitable for assessing excellent-performing and poor-performing subjects. Therefore, with the WAIS-R, because of these biases, we often found ourselves unable to assess with the ordinary procedure subjects with medium and severe deficits, and these subjects were therefore often generically ‘unassessable’ accurately because they were below the minimum assessable (i.e., below IQ=45). For this, differentiated procedures with ‘adjustments’ had been introduced in 2009 for these individuals, as well as, since 2003, for those over 65 years old.
3) the research revealed sensitive cultural and gender biases in the WAIS-R (and WAIS-III ) items.
4) neuropsychological evidence has made it possible to observe that higher brain functions, understood as functional rather than anatomical loci, involve more complex and more articulated functions and articulations than was thought before the advent of new theories and neuroimaging techniques, in particular the new CHC (Cattel-Horn_Carrol) theory/model of intelligence has revealed multiple and complex factors, which can be summarized  into 16 “broad” factors, underlying the general intelligence factor “g,” and in 81 “specific” factors.
2) These are the main changes and innovations in the WAIS-IV scale:
1) The following new subtests are added in WAIS-IV:
- comparison of weights (CP)
- puzzle (PZ)
- cancellation (CA)
- reasoning with matrices
- rearrangement of letters and numbers
- search for symbols
the following subtests are deleted :
- Rearrangement of figured histories (SF)
- Reconstruction of objects (RO)
Finally, all the old subtests already in place are radically transformed and improved.
3) Therefore, the new scale increases from 11 to 15 subtests (of which 5 are optional for nonclinical subjects, while all 15 are necessary for a complete profile of clinical subjects). It consists of the following subtests:
1. Drawing with cubes (DC)
2. Similarities (SO)
3. Memory of digits (MC)
4. Reasoning with matrices (RM)
5. Vocabulary (VC)
6. Arithmetic Reasoning (RA)
7. Symbol Search (RS)
8. Puzzle (PZ)
9. Information (IN)
10. Cipher (CR)
11. (Rearrangement of enumerated letters – LN) – SUPPLEMENTARY.
12. (Comparison of weights – CP) – SUPPLEMENTARY.
13. (Comprehension – CO) – SUPPLEMENTARY.
14. (Cancellation – CA) – ADDITIONAL.
15. (Figure completions – CF) – SUPPLEMENTARY.
4) One and the same scale and assessment procedure apply from age 16 to 90, both for normal subjects and for cognitive disability, with no need for adjustments in procedures.
5) the macro factors of intelligence assessed are increased from 2 to 4, so that, next to the global IQ score, the additional scores consist not of the Verbal IQ and Performance IQ, but of 4 composite indices, based on the new cognitive factors highlighted by the research, landed on the CHC model:
- Verbal Comprehension Index (VCI)
- Index of Visual-Perceptual Reasoning (IRP)
- Index of Working Memory (IML)
- Index of Processing Speed (IVE)
In conclusion, the WAIS-IV, with these substantial modifications, constitutes an irreplaceable tool that serves, as part of the overall psychodiagnostic process, to provide necessary foundations for different diagnostic hypotheses, and in particular to enable
- An effective and accurate assessment of both global intelligence and the 4 main factors
- Scientifically based hypotheses on the differential diagnosis between cognitive and emotional disorders, identifying the influence the latter may have on the cognitive profile and suggesting further specific insights
- Scientifically based hypotheses on the differential diagnosis between cognitive disorders (mental retardation and ASD), possibly suggesting the need for specific tests
- Accurate assessment of actual disability for civil disability assessment
- accurate assessment of the cognitive profile to help prepare appropriate individualized rehabilitation plans and to assess residual work and socialization skills.
 for a brief summary see Flanagan and Dixon, 2014