The Validity of the Letter Memory Test as a Measure of Memory Malingering: Robustness to Coaching
The present study examined the utility of the Letter Memory Test (LMT) in the identification of malingerers of cognitive deficits. The LMT is a computerized forced-choice test that includes two face validity manipulations: increase in stimulus length and increase of response choices. Performance on the LMT was compared in healthy controls and in participants with head injury, some of whom were asked to perform with best effort and others asked to simulate cognitive impairment following head injury. As an additional manipulation, those asked to simulate head injury were either warned about the potential for malingering detection or not. The LMT was administered in the context of a clinically relevant battery of neuropsychological assessments, using a counterbalanced design regarding early or late administration of the LMT and the 15-Item Test (FIT). A cutoff of 9 correct on the FIT and 93% correct on the LMT were used. As expected, the LMT was found to be insensitive to head injury, but sensitive to malingering and robust to detection warning. When comparing the two simulator groups (warned and naïve) with the two best effort groups (head injury and healthy), the LMT yielded 76% sensitivity, 96% specificity, 95% positive predictive accuracy and 81% negative predictive accuracy. The FIT yielded 17% sensitivity, 100% specificity, 100% positive predictive accuracy, and 56% negative predictive accuracy. Additionally, the LMT correctly identified all of the malingerers that were identified by the FIT, but the FIT missed 32 of the malingerers that were identified by the LMT. Detrimental order effects were found for the FIT but not the LMT. The two face-validity manipulations of the LMT were also examined. For the two best effort groups and the warned simulator malingerers, performance across both target stimuli length and number of responses remained stable, while performance by the naïve group worsened as stimulus length and number of response choices increased. These results replicate earlier findings that indicate the LMT is an adequate measure of malingering of cognitive deficits and superior to the FIT. The results also extend earlier findings by demonstrating relative robustness of the LMT to coaching.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:memory malingering cognitive deficits letter test coaching
Date of Publication:01/01/2004