1. Exaggeration Affects Test Scores Far More Than Severe Brain Injury Paul Green, Ph.D. Neurobehavioural Associates, Edmonton, Alberta, CA Martin L. Rohling, Ph.D. University of South Alabama, Mobile, AL Paul R. Lees-Haley, Ph.D. Lees-Haley Psychological Corporation, Huntsville, AL Lyle M. Allen, III, M.S. CogniSyst, Inc., Durham, NC

2. Abstract 904 consecutive compensation claimants were referred for assessment, including 470 patients with head injuries. They were given the Word Memory Test (WMT), containing measures of effort. To define patients with severe versus relatively mild head injuries, the patients were divided several ways into two groups, based on Glasgow Coma Scale (GCS), post-traumatic amnesia duration (PTA), duration of loss of consciousness (LOC), or CT/MRI brain scan abnormalities. A composite mean score from 43 neuropsychological test scores was computed (Rohlings overall test battery mean or OTBM). The OTBM scores of the most and least severe cases of head injury were no different. However, there were highly

3. Abstract (continued) significant differences in neuropsychological test scores between those who passed or failed the WMT. The WMT scores explained 53% of the variance in the neuro- psychological test results, whereas each of the severity variables explained less than 5% of the variance in the same data. When cases failing effort tests were removed from the analysis, those with the most severe injuries scored significantly lower on the OTBM than those with less severe injuries. If incomplete effort is not controlled, spurious results will be obtained from group studies. Effort plays a greater role in determining neuropsychological test scores than do conventional measures of brain injury severity.

4. Study Purposes Three primary purposes: 1) Measure the extent to which effort accounts for the statistical variance in neuropsychological tests. 2) Identify the best predictor of test performance among several independent variables, including measures of effort, age, education, and diagnosis. 3) Determine the degree of influence that effort has on ability test scores in contrast to brain injury severity and neurological disease.

5. Study Participants Canadian Workers Compensation Board (n = 376) Medical disability claimants (n = 317) Personal injury litigation (n = 196) Private referrals with disability (n = 15) The sample included head injured patients (n = 470) neurological patients (n = 80). psychiatric patients (n = 107) medical patients (n = 246)

6. Independent Variables: Head Injury Severity Details of head injury severity recorded, including Lowest GCS within 24 hours of injury 32 patients with a GCS between 3 and 8 ( M = 5.0, sd = 1.8) 22 patients with a GCS between 9 and 13 (M = 11.2, sd = 1.5) and 170 patients with a GCS of 14 to 15 (M = 14.8, sd =.4) Presence/absence of intracranial CT/MRI abnormalities 195 patients with abnormalities Duration of post traumatic amnesia (PTA) 90 patients with PTA > 24 hrs Duration of loss of consciousness (LOC) 44 patients with LOC > 30 min

7. Dependent Variables: Neuropsychological Ability Dependent Variable EFWCST-Cats SortedWMT-DFR & LDFRCVLT-Trials 1 & B WCST-Persev ErrorsRCFT-DR & RgPORCFT-Copy & IR Category TestWarrington Wd & FcBenton JLO Ruff Figural FluencyVCWAIS-R or MAB VIQWAIS-R or MAB PIQ Gorhams ProverbsWRAT-III ReadingPSFTT-Dm & Nd MLCVLT-Total & T-5WRAT-III ArithmeticGrip Dm & Nd CVLT-SDFR & LDFRWRAT-III SpellingGrooved Peg-Dm & Nd CVLT-Rg HitsAWTrails A & BSVCARB Total Story Recall IR & DRDigit Span F & BWMT-IR, DR, & Con1 WMT-PA & MCVisual Span F & BCVLT-Logit Formula

8. Study Results: Influence of Effort on Ability

9. Study Results: Effort vs. Brain Injury Severity

10. Study Conclusion The effects of suboptimal effort on the mean scores on a broad range of neuropsychological tests: A strong correlation between three separate symptom validity measures, considered separately, or combined, and the overall test battery mean (OTBM). We studied the effects of exaggeration or suboptimal effort on a wide range of neuropsychological test scores, represented by the OTBM Poor effort resulted in an average OTBM that was 1.57 SD units lower than that of genuine patients. Effort explained 53% of the variance in these data. Severity variables explained less than 5% of the variance.