In the present study, we examined the accuracy of the age-corrected total scaled score and the traditional RDS index calculated from the new version of Digit Span in the detection of malingering, and we explored whether patterns of performance that include the new Sequencing subtest could be used to identify new embedded measures of malingering. A much larger change was the introduction of a new subscale, Sequencing, which was designed to increase the working memory demands of the task ( Wechsler, 2008).
Thus, the items within these two subscales are not identical to their previous versions, although this likely has minimal effect on the overall difficulty level of the test. First, individual items in Digit Span Forward and Backward were modified so that the numbers 1–9 were evenly distributed throughout the trials and were also reordered within some items so that numbers with similar sounds (e.g., 5 and 9) did not appear in the same trial. The WAIS-IV (2008) Digit Span subtest differs from the Digit Span used in all prior studies in two ways. However, given recent revisions of the Wechsler scales, further examination of the malingering indices on this measure is important.
As the accuracy of RDS was more consistent across studies, they suggested that it may be a preferable measure of malingering. Based on the results of 22 studies, they found RDS and age-corrected scaled score to be equally effective in their ability to distinguish malingering from non-malingering groups (of note, all control groups were either patient populations or had history of head injury or other neurological condition). Jasinski, Berry, Shandera, and Clark (2011) recently conducted a meta-analysis of two Digit Span malingering indices, including Reliable Digit Span (RDS Greiffenstein, Baker, & Gola, 1994) and age-corrected scaled score, from the revised or third editions of the Wechsler Adult Intelligence Scale (WAIS) and Wechsler Memory Scale. One neuropsychological test commonly used as an embedded measure of malingering is Digit Span. Embedded measures of malingering (i.e., patterns of performance on traditional neuropsychological measures that are not consistent with neurological injury) may be more robust to coaching, although they may also be less sensitive to malingering ( Gutheil, 2003 Suhr & Gunstad, 2007). Although there are many well-validated standalone measures of malingering ( Bauer & McCaffrey, 2006 Grote & Hook, 2007), access to information about such measures is readily available, making them potentially vulnerable to coaching ( Bauer & McCaffrey, 2006 Lees-Haley, 1997 Ruiz, Drake, Glass, Marcotte, & van Gorp, 2002 Wetter & Corrigan, 1995). Malingering of cognitive impairment remains a primary concern for neuropsychological researchers and practitioners alike, given the high base rates of probable malingering, especially in mild head injury ( Bender & Rogers, 2002 Larrabee, 2007 Mittenberg, Patton, Canyock, & Condit, 2002). Head injury, Malingering, Assessment Introduction
Two potential alternative RDS scores were introduced, which showed better sensitivity than the traditional RDS, while retaining specificity to malingering. Patterns of RDS length using all three subscales of the new scale were different in malingerers when compared with both head-injured and non-head-injured controls. Previously established cutoffs for the age-corrected scaled score and Reliable Digit Span (RDS) performed similarly in the present samples. Undergraduates with a history of mild head injury performed with best effort or simulated impaired cognition and were also compared with a large sample of non-head-injured controls. Using a simulated malingerer design, we examined the predictive accuracy of existing Digit Span validity indices and explored whether patterns of performance utilizing the new version would provide additional evidence for malingering. However, the Wechsler Adult Intelligence Scale-IV ( Wechsler, 2008) altered Digit Span in meaningful ways, necessitating another look at Digit Span as an embedded measure of malingering. Prior research shows that Digit Span is a useful embedded measure of malingering.
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