Detecting Cognitive Malingering: State of the Art David Stigge-Kaufman Forensic Neuropsychology July 13, 2006

Malingering Definition –Intentional production of false or greatly exaggerated symptoms for the purpose of attaining some identifiable external reward (Iverson & Binder, 2000) Often viewed as pejorative and controversial –“In contrast to making the diagnosis of malingering, clinicians seem to be much more comfortable diagnosing people with brain damage, schizophrenia, alcohol or drug abuse, or personality disorders.” (p. 831) Diagnostic Considerations –V65.2 (DSM-IV-TR) “Additional condition that may be a focus of clinical attention” –Differential diagnosis: Factitious Disorder, Somatoform Disorders, Depression

Malingering Checklist A.Presence of a substantial external incentive B.Evidence from neuropsychological testing 1.Definite negative response bias (below chance on a forced-choice measure of cognitive function) 2.Probable response bias on a validity test 3.Discrepancies between test data and known patterns of brain functioning 4.Discrepancies between test data and observed behavior 5.Discrepancy between test data and reliable collateral reports 6.Discrepancy between test data and documented background history C.Evidence from self-report 1.Self-reported history discrepancy with documented history 2.Self-reported symptom discrepancy with known patterns of brain functioning 3.Self-reported symptom discrepancy with behavioral observations 4.Self-reported symptom discrepancy with reports from close informants 5.Evidence of exaggerated or fabricated psychological dysfunction D.Behaviors meeting criteria from groups B and C not fully accounted for by psychiatric, neurologic, or developmental factors Slick et al., 1999; Lezak et al., 2004

Malingered Neurocognitive Dysfunction (MND) Definite MND –Presence of a substantial external incentive –Definite negative response bias –Negative response bias cannot be otherwise accounted for. Probable MND –Presence of a substantial external incentive –> 2 types of NΨ evidence*, or, 1 type of NΨ evidence plus 1 type of evidence from self-report –Behaviors cannot be otherwise accounted for * not including negative response bias Slick et al., 1999

Case Example: A middle aged electrician had passed out at work due to a heat stroke. He was evaluated to determine if the residual memory difficulty was sufficiently severe to preclude his return to work. Across all three delay sets for easy items of the Victoria Symptom Validity Test, this man had 24/24 recognition. In contrast, he gave only three correct responses on the 24 “hard” items. Clinical Application Lezak et al., 2004, p. 776 “Easy” Trial vs “Hard” Trial vs Example 53921

Case Example: Because 24/24 easy items were correct but only 3/24 hard items were correct, this did not suggest a random response pattern. Normal, above chance performance on the easy items demonstrated the patient’s understanding of the instruction and that he was not confused about how to respond. The below chance performances for the three hard conditions have corresponding statistical probabilities of.14,.004, and.004. Thus, when treated as independent samples, the probability of occurrence is (.14 X.004 X.004). This success/failure pattern cannot be explained away as due to confusion or misunderstood instructions. Clinical Application Lezak et al., 2004, p. 776

Frederick et al., 2000 Effort, Motivation, & Response Styles

Case Studies –Examine test data from individual cases, looking for performance levels below chance on forced-choice tests. Simulation Studies –May involve comparisons of 4 groups: 1) Normals faking impairment 3) Normals responding honestly 2) Patients responding honestly 4) Patients faking impairment Known-Group Designs –Establish criterion groups (e.g., patients, malingerers), and conduct a systematic analysis of similarities and differences between groups Differential Prevalence Designs –Compare groups known to be higher in malingering to those who are not Researching Malingering

What about the roles of perceived difficulty, face validity, or test modality? Sample Malingering Test

Test Popularity Among Experts Forced-choice testing: –Digit Recognition Digit Memory Test (DMT) Portland Digit Recognition Test (PDRT) Victoria Symptom Validity Test (VSVT) Computerized Assessment of Response Bias (CARB) –Word Recognition 21-Item Test Word Memory Test (WMT) –Verbal & Nonverbal Abilities Validity Indicator Profile (VIP) Slick et al., 2004 Forced-choice testing: –Visual Recognition Test of Memory Malingering (TOMM) Letter Memory Test 48-Pictures Test Simplistic tests: –Rey 15-Item Test –Dot counting Test –The b Test Always/Often Used: > 40% Always/Often Used: 30-39% Always/Often Used: 20-29% Always/Often Used: 10-19%

Test Sensitivity* Forced-choice testing: –Digit Recognition Digit Memory Test (DMT) Portland Digit Recognition Test (PDRT) Victoria Symptom Validity Test (VSVT) Computerized Assessment of Response Bias (CARB) –Word Recognition 21-Item Test Word Memory Test (WMT) –Verbal & Nonverbal Abilities Validity Indicator Profile (VIP) Forced-choice testing: –Visual Recognition Test of Memory Malingering (TOMM) Letter Memory Test 48-Pictures Test Simplistic tests: –Rey 15-Item Test –Dot counting Test –The b Test Sensitivity: > 85% Sensitivity: 70 – 84 % Sensitivity: 50 – 69 % Sensitivity: < 49 % Lezak et al., 2004, Vickery et al., 2001 * Sensitivity = % of malingerers correctly classified

Test Specificity* Forced-choice testing: –Digit Recognition Digit Memory Test (DMT) Portland Digit Recognition Test (PDRT) Victoria Symptom Validity Test (VSVT) Computerized Assessment of Response Bias (CARB) –Word Recognition 21-Item Test Word Memory Test (WMT) –Verbal & Nonverbal Abilities Validity Indicator Profile (VIP) Forced-choice testing: –Visual Recognition Test of Memory Malingering (TOMM) Letter Memory Test 48-Pictures Test Simplistic tests: –Rey 15-Item Test –Dot counting Test –The b Test Specificity: > 85% Specificity: 70 – 84 % Specificity: 50 – 69 % Specificity: < 49 % * Specificity = % of non-malingerers correctly classified Lezak et al., 2004, Vickery et al., 2001

Malingering Patterns in NΨ Tests Pattern Analysis –WMS-R Malingerers: Attention/Concentration < General Memory Opposite pattern to typical head injury –WAIS-R: Digit Span Malingerers: Low digit span performance (ss < 4) Reliable Digit Span (sum of longest correct span for both trials < 7) Vocabulary – Digit Span (low digit span while vocabulary is high) –CVLT Malingerers: Low recognition (hits & forced-choice) Cutoff scores for recall trials produce variable false-positive rates Iverson & Binder, 2000; Larrabee, 2005

Malingering Patterns in NΨ Tests Pattern Analysis –Word Memory Test Malingerers: Inconsistent responding, poor initial recognition Pattern should reflect severity of impairments –Category Test Malingerers: Poor performance on first 2 subtests –Wisconsin Card Sorting Task Malingerers: Poor ratios of categories completed compared to both perseverative errors and failure to maintain set –Motor Functioning Malingerers: Suppress motor functioning to extreme levels Motor decline should only be associated with severe brain injury Iverson & Binder, 2000; Larrabee, 2005

Symptom Exaggeration Self-Report of Symptoms –May be exaggerated due to other variables (depression, pain, stress) e.g., Post-Concussive Syndrome persisting for more than 3 months MMPI-2 –Malingerers tend to show elevations in clinical scales 1, 2, 3, 7, and 8, the Fake Bad Scale (FBS), VRIN, TRIN, the Infrequency- Psychopathology Scale [F(p)]. –The F Scale and F – K does not appear to be as sensitive, and therefore “valid” profiles may be obtained. –Caution should be given to interpreting the clinical scales and F Scale derivatives, as these can be easily influenced by psychiatric comorbidities. Iverson & Binder, 2000; Larrabee, 2005

Summary & Conclusions Defining Malingering –External reward, negative response bias, and discrepancies in NΨ data and/or self-report Combination of effort and motivation –Case studies, simulation studies, known-group designs, differential prevalence designs Detection of Malingering –Numerous symptom validity tests Most forced-choice tests demonstrate excellent specificity, but not all show high sensitivity –Pattern analysis of NΨ data –Symptom exaggeration

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