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The purpose of the present article is to provide the normative data needed to compute the Cognitive Proficiency Index (CPI) for the Wechsler Adult Intelligence Scale-Fourth Canadian Edition, using the Canadian WAIS-FV standardization sample. The CPI comprises working memory and processing speed subtests which are used to measure the proficiency at which an individual processes cognitive information. The CPI was developed to use in a complementary fashion with the General Ability Index (GAI) and, therefore, the prevalence or frequency of an observed GAI-CPI score difference (base rate) in the normative sample is also provided. The CPI, along with the GAI, provides clinicians with further insight into the cognitive functioning of clients, particularly in circumstances where there is significant variability across the four primary index scores. Two case studies are provided to illustrate the potential clinical benefits of using this optional index.
Keywords: assessment, intelligence, index scores, WAIS-IV
The Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV; Wechsler, 2008a) offers five composite scores: the Verbal Comprehension Index (VCI), the Perceptual Reasoning Index (PRI), the Working Memory Index (WMI), the Processing Speed Index (PSI), and the Full Scale IQ (FSIQ). In addition to these, the WAIS-IVCDN also provides an optional composite score, the General Ability Index (GAI), a comparatively new addition to the Wechsler intelligence scale composites. The GAI was initially developed for use with the Wechsler Intelligence Scale for Children-Third Edition (WISC-III; Wechsler, 1991) by Prifitera, Weiss, and Saklofske (1998) and the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III; Wechsler, 1997) by Tulsky, Saklofske, Wilkins, and Weiss (2001). It was derived from the subtest scaled scores that contribute to the VCI and the PRI, excluding the contribution of any subtest scaled scores contributing to both the WMI and the PSI. The GAI is now fairly routinely used by clinicians for describing components of intellectual ability assessed using both the WISC-IV and WAIS-IV (Zhu, Raiford, & Coalson, 2009).
To complement the GAI, the Cognitive Proficiency Index (CPI) was recently introduced as an optional Wechsler composite score. The CPI is derived from those scales that comprise the WMI and the PSI including: Digit Span (DS), Arithmetic (AR), Symbol Search (SS), and Coding (CD), and excluding any contribution from VCI and PRI subtests. The development of the CPI is arguably the...