Assessment of Psychopathy Among Justice-Involved Adult Males With Low Versus Average Intelligence: Differential Links to Violent Offending

Psychopathic personality is a multidimensional construct (De Brito et al., 2021) and the dimensions have differential associations with general and violent offending. Impairment in cognitive functioning, particularly intelligence (IQ), is another construct linked to both general and violent offending. However, the evidence is mixed on whether the combination of elevated psychopathy and low IQ increases the risk for violent offending (Hampton et al., 2014; Heilbrun, 1982; Walsh et al., 2004). Also, before this interaction can be firmly established, assessment of whether psychopathic traits are equivalent among individuals with different levels of IQ, especially those in the justice system, is needed. Using multiple-group confirmatory factor analysis (MG-CFA), this study of justice-involved adult males tested whether Psychopathy Checklist-Revised (PCL-R; Hare, 2003) item parameters were invariant among those with low (<85) versus average IQ (>= 85). In addition, moderated nonlinear factor analysis was conducted using continuous IQ scores to test for its effect on a range of model parameters. Both approaches provided evidence of measurement invariance. Adding criminal offenses to the MG-CFA revealed differential associations of the psychopathy dimensions with violent offending. Finally, analysis of variance results suggested an interaction between psychopathy status and IQ level-that is, those meeting diagnostic criterion for psychopathy with low IQ had the highest number of violent offenses. This study provides evidence of measurement invariance for the PCL-R among justice-involved persons with varying levels IQ and helps to extend research on the dynamic associations between psychopathy, IQ, and violent behavior. Public Significance Statement This study found that psychopathic personality features can be reliably assessed without bias among justice-involved adult males with low intelligence, as with those with average intelligence, and that lower intelligence in combination with elevated psychopathic features increases risk of violent behavior.