Development and Validation of the Malingering Discriminant Function Index for the MMPI–2

A New Index for the MMPI-2 Test for Detecting Dissimulation in Forensic Evaluations: A Pilot Study

This pilot study is the starting point of a potentially broad research project aimed at identifying new strategies for assessing malingering during forensic evaluations. The forensic group was comprised of 67 males who were seeking some sort of certification (e.g., adoption, child custody, driver's license, issuance of gun permits, etc.); the nonforensic group was comprised of 62 healthy male volunteers. Each participant was administered the MMPI-2. Statistical analyses were conducted on obtained scores of 48 MMPI-2 scales. In the first step, parametric statistics were adopted to identify the best combination of MMPI-2 scales that differentiated the two groups of participants. In the second step, frequency-based, nonparametric methods were used for diagnostic purposes.

RESULTS

A model that utilized the best three predictors ("7-Pt", "L," and "1-Hs") was developed and used to calculate the Forensic Evaluation Dissimulation Index (FEDI), which features satisfactory diagnostic accuracy (0.9), sensitivity (0.82), specificity (0.81), and likelihood ratio indices (LR+ = 4.32; LR- = 0.22).

A Comparative Analysis of MMPI-2 Malingering Detection Models Among Inmates

There are several strategies, or models, for combining the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) validity indicators to detect malingered psychiatric symptoms. Some scholars have recommended that an elevated F (Infrequency) score should be followed by the inspection of Fp (Infrequency—Psychopathology), whereas a recent meta-analysis indicated that Fp and Ds (Gough’s Dissimulation Scale) should be examined. For correctional settings, one model of malingering suggests that F, Fp, and F - K (Gough’s Dissimulation Index) should be inspected for one or more elevated scores. Although a large body of research has examined malingering detection with the MMPI-2, this research has typically focused on the contributions of individual validity indicators to differentiate malingered from genuine psychiatric symptoms. Therefore, the current study compared these models of malingering detection on the MMPI-2. Inmate simulators were contrasted with inmates who were hospitalized for psychiatric treatment. Results from classification and logistic regression analyses supported the sequential use of F and Fp in malingering detection.

The utility of the MMPI-2 malingering discriminant function index in the detection of malingering: a study of criminal defendants

This study examined the utility of the Minnesota Multiphasic Personality Inventory-2's (MMPI-2) malingering discriminant function index (M-DFI), recently developed by Bacchiochi and Bagby, in the detection of malingering in a forensic sample. Criminal defendants were divided into "malingering" and "not malingering" groups using the structured interview of reported symptoms (SIRS) criteria proposed by Rogers. Logistic regression analysis (LRA) revealed that the MMPI-2 infrequency (F) scale had the best predictive utility of the traditional infrequency scales. Although the M-DFI did significantly differentiate the malingering from the not malingering groups, it did not add significantly to the predictive utility of the MMPI-2 F scale. Receiver operating characteristics analyses demonstrated acceptable sensitivity and specificity for the MMPI-2 F scale, but poor sensitivity for the M-DFI scale. The results are discussed in terms of the utility of the M-DFI in detecting malingering and problems of extending the findings of simulation studies to the forensic context.