Exaggeration Affects Test Scores Far More Than Severe Brain Injury

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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

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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

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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.

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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.

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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)

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Independent VariablesHead 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 gt 24 hrs
• Duration of loss of consciousness (LOC)
• 44 patients with LOC gt 30 min

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Dependent Variables Neuropsychological Ability
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Study ResultsInfluence of Effort on Ability
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Study ResultsEffort vs. Brain Injury Severity
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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.