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WAIS-IV subtest covariance structure: conceptual and statistical considerations.
L Charles Ward1, Maria A Bergman1, Katina R Hebert1
1Psychology Service, Veterans Affairs Medical Center.
Psychological Assessment
|September 21, 2011
Summary
This study re-examined Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) factor structures. A new model better explains subtest relationships and aligns with intelligence theories.
Area of Science:
- Psychometrics
- Cognitive Psychology
- Intelligence Testing
Background:
- Confirmatory factor analyses (CFAs) of the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) initially supported four oblique factors: Verbal Comprehension, Working Memory, Perceptual Reasoning, and Processing Speed.
- However, unexplained covariance between Perceptual Reasoning subtests (Block Design and Visual Puzzles) and an added path from Working Memory to Figure Weights were noted in previous analyses.
Purpose of the Study:
- To investigate alternative structural models for the WAIS-IV using existing standardization data.
- To address unexplained covariance and evaluate theoretical adherence in factor models of intelligence.
Main Methods:
- Re-analysis of confirmatory factor analyses (CFAs) data from the WAIS-IV standardization sample (N = 1,800).
- Comparison of an initial four-factor model with an alternative four-factor model and a five-factor model based on Cattell-Horn-Carroll theory.
- Evaluation of model fit, conceptual coherence, and theoretical adherence.
Main Results:
- The original model's path from Working Memory to Figure Weights increased the association between Working Memory and Matrix Reasoning.
- Specifying both paths improved model fit but led to Figure Weights and Matrix Reasoning being equally determined by Perceptual Reasoning and Working Memory.
- The proposed alternative four-factor model successfully explained theory-implied covariance and maintained compatibility with the WAIS-IV Index structure, comparing favorably to a five-factor model.
Conclusions:
- The proposed four-factor model offers a more theoretically coherent explanation of WAIS-IV subtest interrelationships.
- Covariance model comparisons require consideration of conceptual coherence and theoretical adherence alongside statistical fit.
- Findings highlight the importance of theoretical grounding in psychometric model development for intelligence scales.
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