Verbal fluency and digit span variables as performance validity indicators in experimentally induced malingering and real world patients with TBI

Abstract

Objective: This study was designed to examine the classification accuracy of verbal fluency (VF) measures as performance validity tests (PVT).

Method: Student volunteers were assigned to the control (n = 57) or experimental malingering (n = 24) condition. An archival sample of 77 patients with TBI served as a clinical comparison.

Results: Among students, FAS T-score ≤29 produced a good combination of sensitivity (.40–.42) and specificity (.89–.95). Animals T-score ≤31 had superior sensitivity (.53–.71) at .86-.93 specificity. VF tests performed similarly to commonly used PVTs embedded within Digit Span: RDS ≤7 (.54–.80 sensitivity at .93–.97 specificity) and age-corrected scaled score (ACSS) ≤6 (.54–.67 sensitivity at .94–.96 specificity). In the clinical sample, specificity was lower at liberal cutoffs [animals T-score ≤31 (.89–.91), RDS ≤7 (.86–.89) and ACSS ≤6 (.86–.96)], but comparable at conservative cutoffs [animals T-score ≤29 (.94–.96), RDS ≤6 (.95–.98) and ACSS ≤5 (.92–.96)].

Conclusions: Among students, VF measures had higher signal detection performance than previously reported in clinical samples, likely due to the absence of genuine impairment. The superior classification accuracy of animal relative to letter fluency was replicated. Results suggest that existing validity cutoffs can be extended to cognitively high functioning examinees, and emphasize the importance of population-specific cutoffs.

Keywords:

• Experimental malingering
• performance validity
• population-specific cutoffs
• verbal fluency

Ethical approval

Relevant ethical guidelines were followed throughout the project. All data collection, storage and processing was done with the approval of relevant institutional authorities regulating research involving human participants, in compliance with the 1964 Helsinki Declaration and its subsequent amendments or comparable ethical standards.

Disclosure statement

The last author provides forensic consultation and medicolegal assessments, for which he receives financial compensation.