A bifactor approach to modeling t...
A BIFACTOR APPROACH TO MODELING THE STRUCTURE OF THE PSYCHOPATHY CHECKLIST-REVISED Christopher J. Patrick, PhD, Brian M. Hicks, MA, Penny E. Nichol, BS, and Robert F. Krueger, PhD From the University of Minnesota���Twin Cities Abstract To date, models of the structure of psychopathy as assessed by the Psychopathy Checklist-Revised (PCL-R) have taken a higher-order approach in which the factors of the PCL-R are modeled as correlated elements of a higher-order psychopathy construct. Here, we propose an alternative structural model of the PCL-R, the bifactor model, which accounts for the covariance among PCL- R items in terms of a general factor reflecting the overlap across all items, and independent subfactors reflecting the unique coherency among particular groups of items. We present examples of how this alternative structural model can account for diverging associations between different subsets of PCL- R items and external criteria in the domains of personality and psychopathology, and we discuss implications of the bifactor model for future research on the conceptualization and assessment of psychopathy. The dominant assessment instrument in the field of psychopathy research for the past several years has been Hare���s (1991, 2003) Psychopathy Checklist-Revised (PCL-R). The PCL-R was developed to assess a unitary psychopathy construct and its 20 items are all intercorrelated. Nonetheless, the instrument also shows evidence of distinctive underyling factors with diverging external correlates (Hare, 2003 Patrick, 2007). Alternative structural models of the PCL-R have been proposed, including two-factor (Harpur, Hakstian, & Hare, 1988 Hare et al., 1990), three-factor (Cooke & Michie, 2001), and four-factor models (Hare, 2003 Hare & Neumann, 2006). These models differ in the number of factors posited, but they all assume that the factors of the PCL-R represent correlated elements (facets) of a higher-order psychopathy construct. Here, we propose an alternative structural model of the PCL-R, the bifactor model, which accounts for the covariance among PCL-R items in terms of a general factor reflecting the overlap across all items, along with separate uncorrelated subfactors reflecting the unique coherency among particular subgroups of items. We present examples of how this alternative model can help to elucidate diverging associations between different subsets of PCL-R items and varying external criteria in the domains of personality and general psychopathology, and we discuss implications of the model for further work on the conceptualization and assessment of psychopathy. THE PCL-R: ORIGINS AND CONTENT COVERAGE Hare���s (1991, 2003) PCL-R was devised to identify individuals within prison or forensic settings who appear psychopathic according to Cleckley���s (1976) definition of the syndrome. The original PCL (Hare, 1980) developed out of a global rating system that had been used by Hare and his colleagues for many years in experimental investigations of male offenders. In Address correspondence to Christopher J. Patrick, Department of Psychology, University of Minnesota, Elliott Hall, 75 East River Road, Minneapolis, MN 55455 E-mail: firstname.lastname@example.org. NIH Public Access Author Manuscript J Pers Disord. Author manuscript available in PMC 2008 February 13. Published in final edited form as: J Pers Disord. 2007 April 21(2): 118���141. doi:10.1521/pedi.2007.21.2.118. NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
the global diagnostic system, raters familiar with the background and recent behavior of the participant assigned scores from 1���7 to indicate the degree of match to Cleckley���s description of the prototypic psychopath (1 = clearly nonpsychopathic 7 = definitely psychopathic). Interrater reliability for this global rating system was high, but nonetheless, the inherent subjectivity of this approach prompted requests for a more systematic, criterion-based procedure. Hare���s strategy in developing the PCL was to identify items from among a large set of candidate indicators that discriminated between individuals assigned low versus high scores on the global rating system. The original version of the PCL consisted of 22 items. Two of these items (���previous diagnosis as a psychopath or similar,��� and ���antisocial behavior not due to alcohol intoxication���) were eliminated in the revised PCL (Hare, 1991), and the scoring criteria for the remaining 20 items were modified somewhat. The item labels and scoring criteria remained the same from the first edition of the PCL-R (Hare, 1991) to the second (Hare, 2003). It is instructive to compare the item content of the PCL-R with Cleckley���s original diagnostic criteria for this disorder. Reflecting his characterization of psychopathy as a ���Mask of Sanity,��� Cleckley���s (1976) criteria included 4 indicators of positive psychological adjustment (superficial charm and good intelligence, absence of delusions or irrationality, lack of nervousness, and disinclination toward suicide) along with 12 indicators of emotional- interpersonal and behavioral deviancy. In the PCL-R, the emotional-interpersonal and behavioral deviance features described by Cleckley are well represented in, but the positive adjustment indicators are not. Patrick (2006) suggested an explanation for this in terms of the procedures used to select items for the PCL-R. Items were retained if they helped to discriminate between individuals assigned high versus low scores on the Cleckley global rating system, and if they exhibited ���good psychometric properties��� (Hare, 1980). The latter criterion implies that indicators were chosen if they contributed to the reliability (internal consistency) of the overall instrument as well as helping to discriminate extreme groups. This would have operated to homogenize the final PCL item set: good-discriminating indicators that correlated with many other discriminating indicators would be retained, whereas indicators that correlated with fewer other indicators would be dropped. As a function of this, positive adjustment indicators that failed to coalesce with the larger proportion of (pathologic) indicators would have been selected out. The end result would be an item set more uniformly indicative of deviance and psychological maladjustment than Cleckley���s original criterion set. Consistent with this perspective, overall scores on the PCL-R are substantially correlated with symptoms of antisocial personality disorder (cf. Hare, 2003), which comprise for the most part indicators of behavioral deviance. The personality traits that are related most strongly to overall scores on the PCL-R are traits reflecting aggressiveness and impulsivity���for example, the Agreeableness and Conscientiousness dimensions of the Five Factor Model (negative correlations in each case Lynam & Derefinko, 2006), and the lower-order Aggression and higher-order Constraint scales of Tellegen���s (in press) Multidimensional Personality Questionnaire (positive and negative correlations, respectively Verona, Patrick, & Joiner, 2001). In addition, total PCL-R scores show significant positive correlations with various behavioral indices of aggression (Hare, 2003) and with measures of alcohol and drug problems (Reardon, Lang, & Patrick, 2002), and weaker positive associations with suicidal behavior (Verona et al., 2001). Moreover, in opposition to Cleckley���s description of psychopaths as lacking in anxiety, overall PCL-R scores show negligible relations with measures of trait anxiety (Hare, 2003) and weak positive correlations with Neuroticism as represented in the Five Factor Model (Lynam & Derefinko, 2006). In summary, the strategy that was used to develop the PCL-R resulted in a set of correlated indicators more uniformly reflective of deviancy and maladjustment than Cleckley���s original diagnostic criteria for psychopathy. At the same time, as discussed in the next section, factor Patrick et al. Page 2 J Pers Disord. Author manuscript available in PMC 2008 February 13. NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
analytic research on Hare���s instrument and affiliated validity studies nevertheless indicate that the PCL-R contains distinctive subgroups of items (i.e., factors) that exhibit discriminant validity in their associations with external criterion variables. DISTINCTIVE FACTORS OF THE PCL-R Considerable effort has been devoted to formally investigating the factor structure of Hare���s PCL-R. The dominant structural model for many years has been the two-factor model (Harpur, Hakstian, & Hare, 1988 Hare, Harpur et al., 1990). In this model, Factor 1 is marked by items reflecting the interpersonal (charm, grandiosity, and deceitfulness/conning) and affective features of psychopathy (absence of remorse, empathy, and emotional depth, and blame externalization). Factor 2 is marked by items describing a chronic antisocial lifestyle, including child behavior problems, impulsivity, irresponsibility, and a lack of long-term goals. Scores on these two PCL-R factors are typically correlated around .5 (Hare, 1991, 2003). Cooke and Michie (2001) noted that a significant weakness of the two-factor model is its failure to meet conventional criteria for goodness-of-fit within a confirmatory analytic framework. To address this problem, these authors proposed an alternative three-factor model of the PCL-R, in which the items of Factor 1 were parsed into two separate (but correlated) factors: ���arrogant and deceitful personality style,��� marked by charm, grandiosity, deceitfulness, and manipulation and ���deficient affective experience,��� consisting of absence of remorse or empathy, shallow affect, and failure to accept responsibility. The third ���impulsive- irresponsible behavioral style��� factor consisted of a truncated version of Factor 2, comprising the five items considered to be most trait-like. Using confirmatory factor analysis, Cooke and Michie demonstrated that this three-factor model did achieve an adequate fit to the data. However, a limitation of this model is that it incorporates only 13 of the 20 items of the PCL- R. More recently, Hare (2003 see also Hare & Neumann, 2006) has advanced a four-factor model that incorporates all but two PCL-R items (sexual promiscuity, numerous marital relationships). In this model, Factor 1 of the original two-factor model is divided into ���Interpersonal��� and ���Affective��� facets (mirroring Cooke and Michie���s first two factors) and Factor 2 is divided into a ���Lifestyle��� facet (mirroring Cooke & Michie���s third factor) and an ���Antisocial��� facet (incorporating the remaining four antisocial deviance indicators from Factor 2, plus one additional item, ���criminal versatility���). Most of the available data concerning the discriminant validity of these PCL-R item subsets pertains to the factors of the original two-factor model. PCL-R Factors 1 and 2 show markedly different associations with various criterion measures of personality and behavior, particularly when their shared variance is controlled for using partial correlation or hierarchical regression methods. For example, the unique variance in PCL-R Factor 1 (affective-interpersonal features) is negatively associated with measures of trait anxiety (Hicks & Patrick, 2006 Patrick, 1994 Verona et al., 2001), and positively correlated with measures of social dominance (Verona et al., 2001 see also Harpur, Hare, & Hakstian, 1989, and Hare, 1991), and in some work, with achievement (Verona et al., 2001) and trait positive affect (Patrick, 1994). Recently, Hall, Benning, and Patrick (2004) reported that these associations are evident mainly for the ���interpersonal��� component of Factor 1 (cf. Cooke & Michie, 2001), reflecting charm, grandiosity, deceitfulness, and manipulativeness. These results indicate that the positive adjustment indicators included in Cleckley���s conceptualization may be tapped to some extent by the variance in Factor 1 that is unrelated to behavioral deviance���particularly that associated with the interpersonal items of the PCL-R. On the other hand, Factor 2 of the PCL-R shows selective positive associations with measures of alcohol and drug dependence (Smith & Newman, 1990 Reardon et al., 2002) and child symptoms of DSM APD, and markedly stronger associations than PCL-R Factor 1 with adult APD symptoms (Hare, 2003 Verona et al., 2001). Also in contrast with Factor 1, PCL-R Factor 2 shows positive relations with trait Patrick et al. Page 3 J Pers Disord. Author manuscript available in PMC 2008 February 13. NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript