Detection of Suboptimal Effort with Symbol Span: Development of a New Embedded Index

Abstract

Developing embedded indicators of suboptimal effort on objective neurocognitive testing is essential for detecting increasingly sophisticated forms of symptom feigning. The current study explored whether Symbol Span, a novel Wechsler Memory Scale-fourth edition measure of supraspan visual attention, could be used to discriminate adequate effort from suboptimal effort. Archival data were collected from 136 veterans classified into Poor Effort (n = 42) and Good Effort (n = 94) groups based on symptom validity test (SVT) performance. The Poor Effort group had significantly lower raw scores (p < .001) and age-corrected scaled scores (p < .001) than the Good Effort group on the Symbol Span test. A raw score cutoff of <14 produced 83% specificity and 50% sensitivity for detection of Poor Effort. Similarly, sensitivity was 52% and specificity was 84% when employing a cutoff of <7 for Age-Corrected Scale Score. Collectively, present results suggest that Symbol Span can effectively differentiate veterans with multiple failures on established free-standing and embedded SVTs.

Indicators of suboptimal performance embedded in the Wechsler Memory Scale–Fourth Edition (WMS–IV)

“…This design differs from our study that recruited mixed-etiology neurological patients. Another study (Young et al, 2012) found that the SSP subtest differentiated well between adequate and inadequate effort in a mixed clinical group of veterans, which we did not find. However, no other WMS-IV subtests were administered in Young et al (2012).…”

“…Another study (Young et al, 2012) found that the SSP subtest differentiated well between adequate and inadequate effort in a mixed clinical group of veterans, which we did not find. However, no other WMS-IV subtests were administered in Young et al (2012). Finally, it should be stressed that the authorized Dutch version of the WMS-IV is equivalent to the originally published U.S. version (Hendriks et al, 2014;Wechsler, 2009), with a similar factor structure (Bouman et al, 2015).…”

“…B. Miller et al, 2011;Young et al, 2012), but lower than the AUC value of 0.95 that was found for the WMS-IV ACS package (including the WMS-IV recognition tasks, the Word Choice Test and reliable digit span: J. B.…”

“…B. Miller et al, 2011). Furthermore, a recent study by Young, Caron, Baughman, and Sawyer (2012) identified the Symbol Span subtest as an indicator of suboptimal performance. This is not surprising as the Symbol Span is a visual analogue of the Digit Span task, which has proven to be able to detect malingering according to a number of validation studies (Axelrod et al, 2006;Babikian, Boone, Lu, & Arnold, 2006;Heinly et al, 2005;Iverson & Tulsky, 2003).…”

“…We selected a number of tasks that we expected to distinguish between malingering participants and nonmalingering neurological patients. First, we selected the visual working memory tasks Spatial Addition (SA) and Symbol Span (SSP), as working memory tests were previously found to be sensitive in other WMS studies (Lange et al, 2006;Young et al, 2012). Secondly, we selected the recognition tasks LM-Rec, VPARec, DE-Rec, and VR-Rec, because these subtests were already shown to be sensitive in previous research using the WMS-IV (Holdnack & Drozdick, 2009;J.…”