Detecting Cognitive Malingering: State of the Art David Stigge-Kaufman Forensic Neuropsychology July...

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 ChecklistA. Presence of a substantial external incentive

B. Evidence from neuropsychological testing1. Definite negative response bias (below chance on a forced-choice measure of

cognitive function)2. Probable response bias on a validity test3. Discrepancies between test data and known patterns of brain functioning4. Discrepancies between test data and observed behavior5. Discrepancy between test data and reliable collateral reports6. Discrepancy between test data and documented background history

C. Evidence from self-report1. Self-reported history discrepancy with documented history2. Self-reported symptom discrepancy with known patterns of brain functioning3. Self-reported symptom discrepancy with behavioral observations4. Self-reported symptom discrepancy with reports from close informants5. 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

46780 vs. 53921

“Hard” Trial

54821 vs. 53921

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 .0000022 (.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 honestly2) 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%



Test Sensitivity*• Forced-choice testing:






(WMT)









– 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:






(WMT)









– 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


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.


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

Frederick, R.I., Crosby, R.D., & Wynkoop, T.F. (2000). Performance curve classification on invalid responding on the Validity Indicator Profile. Archives of Clinical Neuropsychology, 15, 281-300.

Iverson, G.L., & Binder, L.M. (2000). Detecting exaggeration and malingering in neuropsychological assessment. Journal of Head Trauma and Rehabilitation, 15, 829-858.

Larrabee, G.J. (2005). Forensic Neuropsychology: A Scientific Approach. New York: Oxford University Press.

Lezak, M.D., Howieson, D.B., & Loring, D.W. (2004). Neuropsychological Assessment (4th ed.). New York: Oxford University Press.

Slick, D.J., Sherman, E.M.S., & Iverson, G.L. (1999). Diagnostic criteria for malingered neurocognitive dysfunction: Proposed standards for clinical practice and research. The Clinical Neuropsychologist, 13, 545-561.

Slick, D.J., Tan, J.E., Strauss, E.H., & Hultsch, D.F. (2004). Detecting malingering: a survey of experts’ practices. Archives of Clinical Neuropsychology, 19, 465-473.

Vickery, C.D., Berry, D.T., Inman, T.H., Harris, M.J., & Orey, S.A. (2001). Detection of inadequate effort on neuropsychological testing: a meta-analytic review of selected procedures. Archives of Clinical Neuropsychology, 16, 45-73.

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