A re-examination of the Meyers and Volbrecht motor equation for the identification of suspect effort

Abstract

Neuropsychologists are frequently called upon to evaluate cognitive functioning and to participate in determining disability status, particularly in the wake of traumatic brain injuries, strokes, and other health events that compromise central nervous system functioning. A critical component of each evaluation is effort assessment. Ideally, the methods for assessing the credibility of effort are neither obvious to test-takers nor vulnerable to coaching. One of the promising ways to evaluate effort is to use a combination of test scores that assess a common domain, such as motor functioning. The purpose of the present study was to cross validate a linear regression formula developed by Meyers and Volbrecht (2003) to evaluate the credibility of effort on selected tests of motor functioning. The formula utilized scores from the Rey-Osterrieth Complex Figure Test, the WAIS-III Digit Symbol and Block Design subtests, and the Finger Tapping Test. The advantages of such a formula for evaluating effort include that it relies upon embedded measures, resulting in heightened efficiency and greater subtlety of assessment.

The current archival study re-examined the Meyers and Volbrecht (2003) formula using 281 ethnically diverse patients who were referred for neuropsychological evaluation. The sample included 101 patients who met criteria for noncredible effort and 180 patients who met criteria for credible effort. Cut-off scores for the formula were selected to maintain specificity in the credible patients of at least 90%. The associated sensitivity rate when the original cut-offs were applied to the noncredible group was 30.7%. Closer examination of the individual tests that comprised the formula revealed that the Finger Tapping Test had unacceptably low sensitivity (29.7%). Therefore, the Finger Tapping component of the equation was removed, which increased the formula's sensitivity to 70.3% while maintaining specificity of at least 90%. The revised formula provides neuropsychologists a novel way to assess effort that is neither vulnerable to coaching nor adds time to the testing battery. Other findings, limitations of the current study, and recommendations for future research are discussed.