This article describes the development of the Inventory of Problems-29 (IOP-29), a new, short, paper-and-pencil, self-administered measure of feigned mental and cognitive disorders.Four clinical comparison, simulation studies were conducted. Study 1 (n = 451) selected the items and produced an index of potential feigning. Study 2 (n = 331) scaled such index to produce a probability score, and examined its psychometric properties. Study 3 tested the generalizability of Study 2's findings with two additional samples (ns = 128 and 90). Results supported the utility of the IOP-29 for discriminating bona fide from feigned psychiatric and cognitive complaints. Validity was demonstrated with mild traumatic brain injury, psychosis, PTSD, and depression. Within the independent samples of studies 2 and 3, the brief IOP-29 performed similarly to the MMPI-2 and PAI, and perhaps better than the TOMM.Classifications within these samples with base rates of .5 produced sensitivity, specificity, positive predictive power, and negative predictive power statistics of about .80. Further research is needed testing the IOP-29 in ecologically valid field studies.

This article introduces the Inventory of Problems (IOP)-a new, computerized, 181-item tool designed to discriminate bona-fide from feigned mental illness and cognitive impairment-and presents the development and validation of its focal, feigning scale, the False Disorder Score (IOP-FDS). The initial sample included (a) 211 patients and 64 offenders who took the IOP under standard conditions and (b) 210 community volunteers and 64 offenders who feigned mental illness. We split this sample into three subsamples. The first (n = 301) was used to select the variables to generate the IOP-FDS; the second (n = 148) scaled the IOP-FDS into a probability score; and the third (n = 100) tested its validity with an independent dataset. In this third subsample, the IOP-FDS had sensitivity = .90, specificity = .80, and a greater AUC (= .95) than the IOP-29 (= .91). For 40 participants, the PAI was available too. Within this subgroup, the IOP-FDS outperformed the selected PAI validity scales (AUC = .99 vs. AUC ≤ .85).