Introduction to the Special Section on Advancing WAIS-IV and WMS-IV Clinical Interpretation

The Wechsler Adult Intelligence Scale (WAIS) and Wechsler Memory Scale (WMS) are two of the best validated and most frequently used assessment instruments used by clinical psychologists and clinical neuropsychologists (Ball, Archer, & Imhof, 1994; Lees-Haley, Smith, Williams, & Dunn, 1996; Rabin, Borgos, & Saykin, 2008). They have been and will likely continue to be the gold standard in the assessment of cognitive ability and memory in adults. Prior Wechsler editions (WAIS-III and WMS-III) served clinicians well for more than a decade, providing a comprehensive evaluation of verbal and nonverbal abilities, processing speed, working memory, and verbal and nonverbal episodic memory. Nevertheless, several factors necessitated revision of these sturdy and well-worn instruments. First, as with any ability measure, updated normative data were required to maintain the integrity of clinical interpretation of age-adjusted scores. Second, the substantial and growing use of the Wechsler scales across clinical environments and populations, including neurologically impaired populations with unique needs and challenges, called for less culturally biased and more user-friendly administration procedures and materials. Third was the increasing call from both clinicians and researchers for fine-grained parsing of cognitive and memory abilities. The widespread availability of brief ability measures pushes longer instruments to provide more detailed information about specific facets of ability. And finally, a large body of previous studies of the Wechsler scales had raised important conceptual, psychometric, and clinical interpretive issues. Together, these forces pushed for a thoughtful revision, which enhanced the clinical and research utility of the scales. Through a careful revision process, the WAIS-IV and WMS-IV address many of the concerns and challenges identified in previous versions, evolving well beyond a normative update. The intention of the special issue is to draw attention to these improvements and introduce clinicians to two enhancements included in WAIS-IV/WMS-IV Advanced Clinical Solutions–assessment of social cognition and daily living skills. The authors of each article present data that address and resolve important conceptual or psychometric issues impacting clinical interpretation of the WAIS-IV and WMS-IV instruments. Two articles address the structure of the Wechsler scales, with strong relevance for scoring, interpretation, and use of the scales in other populations. Holdnack et al. evaluate several competing structural models to determine the most useful cross-instrument (WAIS-IV/WMS-IV) factor structure. They identify two models with important implications for future scoring algorithms and interpretation in settings in which both scales are routinely administered. Bowden et al. examine the portability of the WAIS-IV to the Canadian population by comparing measurement structures across US and Canadian samples. Results demonstrate measurement invariance—a property that ensures that test scores have the same meaning across populations—across ages and national samples. Furthermore, they found a slight performance advantage for Canadians, which emphasizes the need for local norms rather than relying on the original standardization sample. Replication of these findings in other populations will be essential to ensuring widespread use of the revised scales. Another two papers evaluate the clinical interpretation of subtest and index score variability and low scores. Gregoire et al. provide prevalence rates for discrepancies from the average index score, supplementing the WAIS-IV technical manual’s presentation of pairwise index score comparisons. The data in this article provide important supplemental data to both clinicians and researchers. They find that statistically significant discrepancies between the average and a given index score are quite common and that only very large discrepancies occur rarely in the standardization sample (>15). This discrepancy information is crucial for clinicians who regularly evaluate patients with neurological and neuropsychiatric disorders and the discussion and appendices provide a treasure trove of clinically useful information for analysis of cognitive strengths and weaknesses. Brooks and colleagues present a very careful analysis of low