By: AMFS Board Certified Clinical Neuropsychologist
When it comes right down to it, the most important question in any neuropsychological evaluation is whether you can trust the scores: Are these findings a valid representation of the claimant’s true abilities?
In fact, validity accounts for more of the variation in neuropsychological findings than moderate to severe traumatic brain injury! Without valid scores, no one really knows whether a criminal defendant is truly mentally retarded and thus cannot be served with the death penalty in Atkins cases; whether the head injury from the car accident has been so traumatic as to have brain functioning consequences that create damages; or whether the hypoxic damage in a disability or worker’s compensation case has created impairment severe enough to be truly disabling.
Neuropsychologists have developed a variety of techniques codified into strict guidelines for assessing malingering, but it usually comes down to an assessment of whether the subject has willfully lowered performance or created symptoms in order to obtain the desired result: avoidance of punishment, or the securing of damage awards. While there are other challenges to the validity of the examination concerning non-credible findings, this article focuses on malingering, which has been found in numerous peer-reviewed studies to occur at approximately a 40% rate in the medico-legal arena.
In a low-functioning claimant, the assessment of malingering has been criticized on the grounds that the tests frequently used are actually sensitive to being failed because of low intellectual ability. In other words, according to this criticism, impairment itself and not the willful manipulation of the findings in order to appear impaired is causing test failure.
In a medico-legal case, this presents a conundrum, as low scores by themselves cannot be used to prove either side: Do low scores represent actual impairment? Or the willful lowering of test findings?
To resolve this conundrum, I and my students set out to determine whether low IQ by itself would determine the findings, or whether motivation might have something to do with it. In one study, we compared three groups of low functioning claimants: a Disability group motivated to obtain compensation for a disabling illness; a Work Rehab group motivated to find work in order to support themselves; and a child Protection group motivated to do everything they could to get their children back from State custody.
The findings were most revealing. In the low functioning Disability group, about 46% produced validity failure, but in the low functioning Work Rehab group only about 7% failed, and the in the Child Protection Group, 0% (none) of the claimants failed. When we went back and examined the failures in the Work Rehab group, we found that they had been sent by Disability Determinations to examine the work they might still be able to do. In other words, there was the distinct possibility that in this “work motivated” group, these claimants were still acting so as to protect disability compensation. In the Child Protection group, with high motivation to look especially good, there was no validity failure. The only pronounced validity failure arose in the group of claimants seeking compensation while claiming disabling mental problems.
In another study, which focused on Atkins death cases because of the seriousness of the life and death issues, we further studied validity tests in Child Protection claimants, all of whom had IQ below 76. In these well-motivated claimants with IQ between 60 and 75, all of the validity tests and indicators were passed by 100% of the claimants, except one test on which two of the claimants (6% failed). It was noted that this test has a large ability component.
Therefore, in low functioning claimants who are well-motivated, validity testing for malingering can be used with confidence as an aid in identifying which of the claimants/defendants are presenting with malingering. Of course, the neuropsychologist still must provide further analysis vis-a-vis the guidelines in any individual case.
 Chafetz, M., Prentkowski, E. & Rao, A. (2011). To work or not to work: Motivation (not low IQ) determines SVT findings. Archives of Clinical Neuropsychology, 26, 306-313.
 Chafetz, M, & Biondolillo, A. (2012). Validity issues in Atkins death cases. The Clinical Neuropsychologist, DOI:10.1080/13854046.2012.730674