Examining the Criterion and Incremental Validity of the MMPI-3 Impulsivity Scale

The Minnesota Multiphasic Personality Inventory-3 (MMPI-3) includes a new Impulsivity (IMP) scale designed to assess for poor impulse-control and non-planful behavior, which was added to broaden the utility of the instrument. The current study aimed to examine the criterion and incremental validity of the IMP scale. A university student sample (n = 1,440) and a community sample oversampled for externalizing tendencies (n = 231) were used for this purpose, and IMP scores were compared to scores on various well-validated criterion measures of impulsivity and externalizing psychopathology. To examine the scale's incremental validity, hierarchical multiple regression analyses were conducted to determine whether IMP adds to other MMPI-3 Specific Problem (SP) scales in the prediction of relevant criteria. The IMP scale primarily showed meaningful correlations with the Negative Urgency and Positive Urgency on the UPPS-P. Significant correlations were also observed with the cognitive, behavioral, disinhibition, and lifestyle domains of various psychopathy measures, as well as measures of antisocial personality disorder and substance use. The IMP scale scores accounted for incremental variance in most of the directly relevant criterion measures above and beyond scores of other MMPI-3 SP scales. Several important caveats, limitations, and future directions are discussed.