Evaluation of the WMS-III Rarely Missed Index in a naive clinical sample

We examined the WMS-III Rarely Missed Index as a reliable predictor of fabrication of memory difficulties. A total of 31 outpatients referred for neuropsychological evaluation completed the WMS-III Logical Memory Delayed Recognition Test (LMDR) before having heard the stories and again after hearing the stories. Of the 30 items from the LMDR completed by participants who had not heard the stories, 5 were found to significantly differ from chance; only 1 of those items was found to do so in the original RMI studies. Conversely, of the six items in the original RMI study, only one was found to differ from chance in the present study. A Monte Carlo randomization of the original six RMI items found that 69% of random responders fell below cutoffs for incomplete effort, suggesting that those with memory impairment severe enough to result in random responding are likely to be classified as demonstrating less than optimal effort. An examination of response bias found no differences among negative, positive, or no-bias responders in terms of overall memory performance. However, RMI was indicative of incomplete effort more often with individuals presenting with a negative response bias. The present study provides evidence of the limitations of using the RMI to detect incomplete effort using the LMDR. The relative values of specificity versus sensitivity are particularly important in clinical evaluations, with the prevention of false accusations of malingering an important goal. The use of multiple indicators of effort is reinforced by this study, and the conservative interpretation of the RMI in particular is recommended.