Development and validation of an inconsistent responding scale for an abbreviated version of the Psychopathic Personality Inventory — Revised

Abstract

An abbreviated version of the Psychopathic Personality Inventory — Revised (PPI-R; Lilienfeld & Widows, 2005) was recently developed to facilitate assessment in settings with time constraints (PPI-R-40; Eisenbarth, Lilienfeld, & Yarkoni, 2015). However, the shortened measure precludes use of the Inconsistent Responding (IR) scales embedded in the full PPI-R. In the present study, we develop a new inconsistent responding scale for the PPI-R-40 and provide initial evidence of its reliability and validity in a sample of undergraduate students (N=974) and a sample of forensic psychiatric inpatients (N=200) that previously completed the PPI-R. Across both samples our newly constructed scale, the Inconsistent Responding-Short-10 (IRS-10), correlated moderately with existing IR scales of the PPI-R (rs=.35–.48) and was associated with several external indicators of inattentiveness, including trait conscientiousness among undergraduates and symptoms of psychosis among forensic inpatients. ROC curve analyses demonstrated that IRS-10 scores strongly discriminated between respondent and randomly-generated protocols and tentative cut scores for profile invalidity are proposed based on rates of sensitivity and specificity. Overall, our findings suggest that the IRS-10 is capable of detecting inconsistent or careless completion of the PPI-R-40 and may improve the integrity of future research and clinical practice with this instrument.