Deception is different: Negative validity test findings do not provide "evidence" for "good effort".

The purpose of this paper is to determine whether negative validity test findings should be used in the Bayesian aggregate along with positive test findings for the determination of malingering as the condition of interest (COI). Evidence-based diagnostic methods for conditions in neuropsychology and medicine were reviewed for comparison with their use in cases of malingering. Logical and Bayesian analyses of these cases were applied. A case study showed that negative validity test findings did not indicate "good effort". Deception about illness is fundamentally different from other constructs/diseases in evidence-based medicine and neuropsychology. This is because deception involves a deliberate process that may involve coaching, claimant research, and/or focusing the deception on one aspect (e.g., slowness) as opposed to other neurocognitive problems (e.g., memory). Comparatively, other conditions in medicine and neuropsychology are unlikely to be manipulated by the patient. The assertion by Frederick (2015) and Black, Necrason, and Omasta (2016) that both positive and negative validity test findings must be used together in the aggregate does not stand up to this comparative scrutiny. The fundamental assumption by these authors that a negative test finding concerning malingering represents "good effort" is flawed; it simply represents lack of evidence of malingering, which cannot be construed as evidence of lack of malingering. We recommend that in forensic determination of malingering, negative validity test findings should not be used in a Bayesian aggregation. This conclusion is consistent with current practices in the field.