Simulation Index: A Method for Detecting Factitious Errors on the WAIS-R and WMS

An attempt was made to detect simulated failures on the WAIS-R and WMS through the qualitative analysis of error types. In the preliminary phase of the study, test protocols of a group of subjects sustaining severe head injury were compared with those of a group of patients claiming severe and persistent mental impairment following minor head injury. Error types relatively specific to each group were identified and given a different numerical weighting. Scores for the error types were summed to produce a Simulation Index score for each subject and a cutoff score for the Simulation Index was established that produced a perfect separation of the groups. In the validation phase, the Simulation Index scoring procedure was applied to two new groups: one sustaining severe head injury and one presenting with independent clinical evidence of simulation. The same cutoff score produced only one misclassification error for the 20 subjects studied.