Utility of Vocabulary Minus Digit Span as an Embedded Measure of Validity within the Wechsler Adult Intelligence Scale 4th Edition

In clinical and forensic evaluations, clinical neuropsychologists measure performance validity using standalone and embedded measures. Given the need to capture neuropsychological functioning through a variety of cognitive tests, newer, more sensitive measures should be evaluated for their utility in comparison to already established measures. Prior iterations of the Weschler Adult Intelligence Scale (WAIS) utilized Digit Span scaled score subtracted by Vocabulary scaled score as an embedded measure of validity, with success (Iverson & Tulsky, 2001; Mittenberg et al., 1995). This study retrospectively investigates the utility of WAIS-IV Vocabulary minus Digit Span (VC-DS) in clinical and forensic contexts compared to established criterion measures. Methods: A sample of 95 patients over the age of 18 were examined. Patients underwent a neuropsychological evaluation for varying medicolegal or clinical reasons. Chi-square test of independence was used to examine the relationship between VC-DS and criterion measures in medicolegal and clinical evaluations and across Racial and Ethnicity diverse groups. Results: A significant relationship was found between WAIS-IV Reliable Digit Span and VC-DS using liberal cut points (P=0.014). The relationship between RDS and VC-DS was found in the Caucasian cohort (p=0.34). A significant relationship was revealed between VC-DS and Test of Memory Malingering (TOMM) trial two (p=0.041)and the California Verbal Learning Test Second Edition forced-choice trial using a liberal cut point in forensic populations (p=0.005). Frequency analysis found that among the clinical and forensic evaluations, 74% passed three or more PVTs across the evaluation. Conclusion: The utility of VC-DS is limited, given the current findings and the statistical limitations. Future directions should include further investigation of how culturally and linguistically diverse groups and functionally impaired groups perform on VC-DS in relation to other established measures of validity. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]