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personal_injury_II_08 - Forensic Neuropsychology in...

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Unformatted text preview: Forensic Neuropsychology in Personal Injury Cases II 1 Russell M. Bauer, Ph.D. July 17, 2008 Assessment of Malingering and Poor Effort 2 v Issues with definition – – – Intentional (intention) Fabrication or exaggeration (action) For purposes of gain (motive) v Explanatory models (Rogers, 1997) – – – Pathological (mental disorder) Criminological (fake) Adaptational (meeting adversarial demands) v Cognitive vs. Somatic Malingering Diagnosis Threat (Suhr & Gunstad, 2002) 3 v 37 MHI (17 in “diagnosis threat” condition threat” v Diagnosis threat: told selected because of a MHI history; “a growing number of studies show that many individuals with head injury show cognitive deficits in cognitive neuropsychological tests” tests” 4 5 6 Effort, Motivation, & Response Styles 7 Slick (1999) v Considers evidence from NP and self report v NP criteria – Definite or probable response bias – Discrepancies/inconsistencies between NP data and patterns of brain functioning, brain collateral reports, reports of past functioning 8 1 Slick et al, 1999 (cont’d) DEFINITE MND Presence of financial incentive v Definite negative response bias v Behaviors that meet criteria for negative response bias that are not fully accounted for by psychiatric, neurological, or developmental factors v PROBABLE MND v Presence of financial incentive v Two or more types of evidence from NP, excluding definite response bias, or one piece of evidence from NP response and one from self-report selfv v 2 9 Malingering Research Literature v v Case study Simulation studies – Interpretive issues – Appropriate designs v Differential prevalence design – contrasting high and low baserate groups (e.g., groups with and without financial incentives) – Valuable mostly for determining average performances v Known-groups design Known– Selecting groups on the basis of malingering criteria (e.g., Slick, et al) Slick, – Examining differences between the groups 10 Selecting Specialized Cognitive Effort Tests v Ease of use v Credibility of rationale v Operating Characteristics – Incremental validity – TBI vs. PPCS v Coaching issues v There is not likely to be a “best” test in all circumstances best” 11 Commonly Used Specialized Tests Portland Digit Recognition Digit Memory Test v Computerized Assessment of Response Bias (CARB) v Word Memory Test (WMT) v Victoria Symptom Validity Test v Test of Memory Malingering v Validity Indicator Profile v Rey 15-Item Test 15v Dot Counting Test v v 12 Detecting Anomalous Results with Embedded Measures and Performance Patterns Performance v Measures within standard NP tests that signify noncredible or ‘suspect’ suspect’ performance v Identification of such measures can be “rational” or “empirical” rational” empirical” v May be less subject to coaching than separate measures 13 Pattern Analysis v Pattern Analysis – With HRNB, DFA outperforms clinicians (80-90% v. 50-60%) (8050– Most DFA’s multivariate , consisting of attention and memory measures DFA’ u Generally, malingers score better on hard measures – DFA’s exist for WMS-R, WMS-III, WAIS-R, WAIS-III and other tests DFA’ WMS- WMSWAIS- WAIS– Before using, investigate whether the DFA was validated/cross validated with known validated groups or simulators 14 Embedded Measures – Motor, Sensory, and Perceptual-Motor PerceptualPerceptual-motor pseudoabnormality should not be overlooked b/c of emphasis on “higher” cognitive Perceptualhigher” disabilities v Approaches v – Neurologic exam – Sensorimotor impairments on NP exam v Findings – – – – RCFT copy 50% sensitive with lots of FP Malingering groups favor memory over visuoconstructive impairment (e.g. memory trials of RCFT discriminate better) Generally large grip strength effect size in NG designs Reduced FT speed in the context of MHI 15 Embedded Cognitive Measures – WMS-R/WMS-III WMS- R/WMSu u u Malingerers: Attention/Concentration < General Memory Opposite pattern to typical head injury Rarely-missed index on LM delayed recognition trials Rarely- – WAIS-R/WAIS-III: Digit Span WAIS- R/WAISu Malingerers: Low digit span performance (ACSS < 5) Reliable Digit Span (sum of longest correct span for both trials < 8) (sum u Vocabulary – Digit Span (low digit span while vocabulary is high) u – CVLT u u u 16 Malingerers: Low recognition (hits & forced-choice) forcedCutoff scores for recall trials produce variable false-positive rates falseVariable results with most widely used cutoffs (Millis et al): Total < 35, LDCR <7, delayed recognition <11, discriminability < 81; sensitivity in question, not specificity Malingering Patterns in NΨ Tests v Pattern Analysis – Word Memory Test u u Malingerers: Inconsistent responding, poor initial recognition Pattern should reflect severity of impairments – Category Test u Malingerers: Poor performance on first 2 subtests – Wisconsin Card Sorting Task u Malingerers: Poor ratios of categories completed compared to both perseverative errors and failure to maintain set both 17 18 Why being a knowledgeable neuropsychologist is important v You know likely patterns of impairment v You know psychometric relationships among tests v You know course of recovery v You know about contributory factors (e.g., LD, depression, etc.) v You can compare what you see to what you expect 19 Common “suspect” neuropsychological signs on NP testing suspect” v Recognition << recall (hits, discriminability) discriminability) v Extremely poor DS in the context of normal auditory comprehension (RDS) comprehension v Motor slowing (e.g., reduced tapping) relative to overt motor disability disability v Excessive failures-to-maintain-set on WCST failures- to- maintainv Discrepancies between test level and level during informal interaction interaction v Other “impossible” signs impossible” 20 Some Take Home Messages v Use multiple measures (forced choice, embedded, etc.) v Clarify your goals: sensitivity, specificity, etc. v Be aware of correlations among malingering measures v Look for emerging research on sensitivity/specificity of multiple indicators multiple 21 Symptom Exaggeration v Self-Report of Symptoms Self– May be exaggerated due to other variables (depression, pain, stress) stress) u e.g., Post-Concussive Syndrome persisting for more than 3 months Post- v MMPI-2 MMPI– Malingerers tend to show elevations in clinical scales 1, 2, 3, 7, and 8, the Fake Bad Scale (FBS), VRIN, TRIN, the InfrequencyInfrequencyPsychopathology Scale [F(p)]. [F(p)]. – The F Scale and F – K does not appear to be as sensitive, and therefore “valid” profiles may be obtained. valid” – Caution should be given to interpreting the clinical scales and F Scale derivatives, as these can be easily influenced by psychiatric comorbidities. comorbidities. 22 Detecting Somatic Malingering v Symptom report, as well as cognitive performance, can be controlled by the litigant controlled v Use of MMPI-2 MMPI- – – – – – F-scale, F(p) VRIN, TRIN Subtle-Obvious SubtleF-K index Revised Dissimulation Scales v These scales may not be sufficiently sensitive to TBI-related claims, despite neuroTBIneuro- psychological differences 23 Lees-Haley FBS v Model of goal-directed behavior: goal- – – – – – – 24 Want to appear honest Want to appear psychologically normal except for the influence of injury of Avoid admitting longstanding problems Minimize pre-existing complaints preMinimizing pre-injury antisocial or illegal behavior prePresenting plausible injury severity Lees-Haley FBS (cont’d) v 18 “True” , 25 “False” True” False” v Does not correlate very strongly with F-scale derivatives Fv Most scale items overlap with “neurotic” side of MMPI neurotic” v Cut-off mid 20’s, with varying false positive rates; increasing security with scores Cut20’ scores > 25-27 25- 25 FBS Operating Characteristics v Most frequently failed indicator of MND (Larrabee) v FBS > 27 has Sn=.46 , Sp=.96, better than F or Fb (Greve et al) Sn=.46 v Sensitive to symptom exaggeration in personal injury, not just litigation litigation v Cutoffs determine TP, FP rate 26 Critical Studies v Butcher et al (2003) – – – – – v Bury & Bagby (2002) – – – – – 27 Unacceptably high FP of FBS (24% of males, 37.9% of females exceeded cutoffs) exceeded Psychiatric, corrections, medical, pain, VA, personal injury litigants litigants No measures of symptom validity external to the MMPI No report of who was litigating Can’t compute specificity or sensitivity without this information Can’ PTSD vs. students (standard and exaggeration instructions) F family produced best overall classification rates Entire PTSD sample were being evaluated for workplace disability Mean PTSD FBS was 26.31 No independent measures of malingering or exaggeration 28 ...
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