The fourth edition of the Wechsler Adult Intelligence Scale (WAIS-IV) is a revised and substantially updated version of its predecessor. The purposes of this research were to determine the constructs measured by the test and the consistency of measurement across large normative and clinical samples. Competing higher order WAIS-IV four- and five-factor models were analyzed using the WAIS-IV’s sample of 1,800 normative adults and 411 clinical adults. When all 15 WAIS-IV subtests were considered, both four- and five-factor models were suitable, but the five-factor model provided a better fit. The WAIS-IV PRI differentiated into two composites as follows: POI(Gv) consisting of Block Design, Visual Puzzles and Picture Completion; and FRI(Gf) consisting Matrix Reasoning, Arithmetic and Figure Weights. The five-factor solution included Quantitative Reasoning (RQ), consisting of Arithmetic and Figure Weights, as a narrow ability subsumed under FRI(Gf). Arithmetic, Vocabulary, and Figure Weights subtests had the highest g loadings. Cancellation had the lowest g loading. The WAIS-IV generally demonstrated full factor invariance between clinical and nonclinical samples.

This discussion article addresses issues related to expansion of the Wechsler model from four to five factors; multiple broad CHC abilities measured by the Arithmetic subtest; advantages and disadvantages of including complex tasks requiring integration of multiple broad abilities when measuring intelligence; limitations of factor analysis, which constrain test developers to creating specific broad and narrow abilities as opposed to integrative tasks; implications from brain imaging research showing the critical role of neurological pathways that integrate brain regions; close relationship of the fluid reasoning factor to g, and the inadequacies of factor analytically driven statistical definitions of g in the development of improved models of intelligence. In this rejoinder to the commentaries in this special issue on structural models of the WAIS-IV and WISC-IV, the advantages and disadvantages of Schmid–Leiman’s transformation, which removes the effects of g on the broad abilities, and the use of nested or bifactor models in evaluating models of intelligence are also discussed.

Many Flynn effect (FE) studies compare scores across different editions of Wechsler’s IQ tests. When construct changes are introduced by the test developers in the new edition, however, the presumed generational effects are difficult to untangle from changes due to test content. To remove this confound, we use the same edition of Wechsler Intelligence Scale for Children–Fourth Edition (WISC-IV) across an 11-year period. Whereas previous research has reported the FE to be less than half the theoretical rate when comparing WISC-IV with Wechsler Intelligence Scale for Children–Fifth Edition (WISC-V), we find the rate of gain to be nearly identical to Flynn’s prediction when comparing only WISC-IV scores over the same time period. The FE is shown to vary significantly across the domains of cognitive ability, and thus changes to the construct coverage of the WISC-V Full Scale IQ (FSIQ) composite between editions significantly affect FE findings. Implications for future FE research are discussed.

Flynn has proposed a grand integrative theory, which he calls “scientific spectacles,” to explain the phenomenon of rising IQ scores across multiple decades known as the Flynn effect (FE). In his theory, he purports that modern society has placed increasing value and emphasis on the application and education of scientific principles—which include abstract fluid reasoning—and this has mirrored larger score increases in the abstract fluid reasoning tasks included as part of most intelligence tests. He highlights huge gains in the Wechsler Similarities subtest over time as one linchpin supporting his theory that fluid reasoning is rising faster than other aspects of intelligence, but further points to large increases in Wechsler performance tasks (i.e., perceptual organization and reasoning) relative to crystallized tasks, and to the many studies of Raven’s Progressive Matrices, which is widely held to be a fairly pure measure of fluid reasoning. As with any new theory of this magnitude, Flynn’s grand proposal has invited numerous criticisms that must now be addressed—and this is as it should be in the spirit of scientific progress. Each of these issues is multilayered and has many legitimate perspectives. The present article attempts to carefully consider each issue and perspective in sequence.