Higher Order, Multisample, Confirmatory Factor Analysis of the Wechsler Intelligence Scale for Children--Fourth Edition: What Does It Measure?.

Abstract. The recently published fourth edition of the Wechsler Intelligence Scale for Children (WISC-IV) represents a considerable departure from previous versions of the scale. The structure of the instrument has changed, and some subtests have been added and others deleted. The technical manual for the WISC-IV provided evidence supporting this new structure, but questions about consistency of measurement across ages and the nature of the constructs measured by the test remain. This research was designed to determine whether the WISC-IV measures the same constructs across its 11-year age span and to explicate the nature of those constructs. The results suggest that the WISC-IV indeed measures consistent constructs across ages. The scoring structure of the test was not supported in these analyses, however. Comparison of theory-derived alternative models suggests a model more closely aligned with Cattell-Horn-Carroll theory provides a better fit to the WISC-IV standardization data than does the existing WISC-IV structure. In particular, it appears that the WISC-IV measures crystallized ability (Gc), visual processing (Gv), fluid reasoning (Gf), short-term memory (Gsm), and processing speed (Gs); some abilities are well measured, others are not. We recommend that users regroup the Perceptual Reasoning tests, and Arithmetic, to better reflect the constructs measured by the WISC-IV. Specific suggestions are also provided for interpretation of WISC-IV scores. ********** Long considered the "gold standard" for intelligence testing, the Wechsler Intelligence Scale for Children (WISC) is now in its fourth revision (Wechsler, 2003). Inherent in updating such a widely used and venerated instrument is the challenge of balancing test continuity with modernizing the test to reflect contemporary intelligence theory. In the previous revision of the WISC, this challenge was described as "walking on a tightrope" (Keith & Witta, 1997, p. 89). Historically, revisions to the WISC provided continuity to its users. The Full Scale Verbal IQ and Performance IQ were preserved throughout the instrument's first 60 years of development. Yet the WISC, like many pioneering tests, lacked a firm grounding in theory. Because WISC revisions have chosen to provide continuity, the test has been criticized for its failure to integrate modern theories of cognitive abilities (Jensen, 1987; Witt & Gresham, 1985). The WISC's progression from a two-factor (WISC) to a three-factor (WISC-R) to a four-factor (WISC-III) instrument was met with contention as each new factor was added. Originally intended to strengthen a third factor, the addition of the Symbol Search subtest in the WISC-III resulted in two small, less robust factors incorporating two subtests each. The Freedom from Distractibility factor's relevance to attentional issues was questioned (Kaufman, 1994; Keith, 2005; Keith & Witta, 1997), and the relative contributions of working memory (Kranzler, 1997) and quantitative ability (Keith, 1997) to this factor were debated. The name "Processing Speed" was also questioned, based on the inconsistency between g loadings of psychometric versus laboratory processing speed tasks (Keith, 1997; Kranzler, 1997). WISC-IV Revisions The WISC-IV represents the boldest departure from previous editions. The two-factor Verbal IQ and Performance IQ interpretation has been abandoned; five new subtests have been added; the Mazes, Object Assembly, and Picture Arrangement subtests have been dropped; and Arithmetic, Information, and Picture Completion are now supplemental subtests. The WISC-IV recognizes four factor indices: Verbal Comprehension Index (VCI), Processing Speed Index (PSI), Working Memory Index (WMI), and Perceptual Reasoning Index (PRI). The VCI and PSI have retained their names, representing the continuity of these factors in the transition from the WISC-III to the WISC-IV. The previous Perceptual Organization Index of the WISC-III has been changed to the PRI to recognize an "increased emphasis on fluid reasoning abilities in this index" (Wechsler, 2003, p. …