Psychopathic Personality Inventory (PPI)

The Psychopathic Personality Inventory (PPI) is a widely used self-report measure designed to detect the principal personality traits of psychopathy. Revised in 2005 as the Psychopathic Personality Inventory-Revised (PPI-R), it consists of 154 items arrayed in a 4-point Likert-type format. The PPI-R, like the original PPI, yields a Total score reflecting global psychopathy as well as eight-factor analytically derived content scales reflecting specific facets of psychopathy: Machiavellian Egocentricity, Rebellious Nonconformity (formerly Impulsive Noncomformity), Blame Externalization (formerly Alienation), Carefree Nonplanfulness, Social Influence (formerly Social Potency), Fearlessness, Stress Immunity, and Coldheartedness. The PPI-R also contains three validity scales designed to detect aberrant response styles that are potentially problematic among psychopathic individuals: Virtuous Responding (formerly Unlikely Virtues), Deviant Responding, and Inconsistent Responding (formerly Variable Response Inconsistency).

Construction of the PPI and PPI-R

The PPI, consisting of 187 items, was developed over the span of several years in the late 1980s. It was constructed largely in response to a perceived need for an easily administered questionnaire measure of psychopathy that would facilitate research on, and the clinical assessment of, psychopathy. In contrast to most previous measures of psychopathy, it was developed to be applicable to nonclinical (e.g., student, community) as well as clinical (e.g., offender, substance abuse) samples. Prior to the construction of self-report measures of psychopathy, most of the research on this condition was limited to offenders, primarily because extant measures of psychopathy required access to detailed file information. The development of the PPI and other self-report measures of psychopathy has facilitated research concerning the manifestations of this condition in community and student settings, permitting investigators to examine the characteristics of “successful” or “adaptive” individuals with high levels of psychopathic traits.

The PPI was designed to detect the key personality traits of psychopathy, such as superficial charm, dishonesty, manipulativeness, guiltlessness, callousness, fearlessness, self-centeredness, externalization of blame, and poor impulse control. The initial constructs targeted for inclusion in the PPI were derived from a comprehensive review of the clinical and research literatures on psychopathy, including the seminal writings of Hervey Cleckley, Benjamin Karpman, David Lykken, Robert Hare, and Herbert Quay. In an effort to distinguish psychopathy from cognate but separable constructs (e.g., antisocial personality disorder, crime proneness), items explicitly assessing antisocial and criminal behaviors were not included in the prospective item pool. To enhance the likelihood that the psychopathic respondents would be willing to endorse trait-relevant items, most PPI items were phrased to be socially normative.

The PPI items and constructs were progressively refined by means of factor analyses on three successive undergraduate samples, with a total sample size of 1,156 participants. The eight lower-order factors that make up the PPI emerged across all three rounds of test development and appeared to assess the core affective and interpersonal traits of psychopathy. The three validity scales of the PPI assist with detection of socially desirable responding and malingering, which may be particular causes for concern in forensic settings.

The PPI was revised in 2005 to reduce its length, decrease its reading level, eliminate psychometrically suboptimal and culturally specific items, and develop norms for general population and offender samples. Based on factor analyses of large student, community, and offender samples, a number of inadequately functioning PPI items were eliminated or rewritten. The revised version of the test, the PPI-R, consists of 154 items divided into the same eight content scales and three validity scales as the PPI.

Higher-Order Factor Structure

Higher-order-factor analyses of the PPI-R content scales have generally yielded a two-factor structure. One factor, called “Fearless Dominance,” consists of the Social Influence, Fearlessness, and Stress Immunity content scales. The other factor, called “Self-Centered Impulsivity,” consists of the Machiavellian Egocentricity, Rebellious Nonconformity, Blame Externalization, and Carefree Nonplanfulness content scales. The eighth PPI-R content scale, Coldheartedness, does not load substantially on either higher-order factor. The analyses indicate that the two PPI-R higher-order factors display markedly divergent corre-lates. For example, Fearless Dominance correlates negatively with indices of depression, anxiety, and suicidality, whereas Self-Centered Impulsivity correlates positively with these indices.

Reliability of the PPI-R

The test-retest reliability of the PPI-R Total score (average 20-day retest interval) in a general population sample is .93, with the test-retest reliabilities of the PPI-R content scales ranging from .82 to .95. The internal consistency (Cronbach’s alpha) of the PPI-R Total score in a general population sample is .92, with internal consistencies of the PPI-R content scales ranging from .78 to .87. These test-retest and internal consistency figures are comparable with, and slightly higher than, those generally reported for the PPI. The internal consistency of the PPI-R Total score in an offender sample is somewhat lower (.84), with the internal consistencies of the PPI-R content scales ranging from .71 to .83.

Validity of the PPI-R

Numerous studies in college and offender samples provide support for the construct validity of the PPI and PPI-R. The Total scores on these measures correlate moderately to highly with other self-report, interview-based, and observer measures of psychopathy. The PPI Total score correlates moderately with measures of personality disorders known to overlap with psychopathy, such as narcissistic, histrionic, and borderline personality disorders, but weakly with measures of most other (e.g., schizoid) personality disorders. Moreover, the PPI and PPI-R Total scores display adequate discriminant validity from measures of constructs that are theoretically distinct from psychopathy (e.g., depression, schizotypy, psychosis proneness, social desirability).

In addition, the PPI and PPI-R Total scores correlate negatively with several traits of the well-known “five-factor model” of personality, especially Conscientiousness and Agreeableness, and positively with measures of sensation seeking and Machiavellianism. Finally, the PPI Total score demonstrates positive correlations with measures of delinquent behaviors and substance abuse, laboratory measures of poor impulse control and planning, and offender disciplinary infractions. Future research should help determine whether (a) the PPI-R exhibits incremental validity above and beyond other well-validated measures of psychopathy (e.g., the largely interview-based Psychopathy Checklist-Revised), (b) observer reports of psychopathy can supplement the PPI-R by filling in some of the “blind spots” generated by psychopathic individuals’ lack of insight regarding the nature of their symptoms, and (c) the PPI-R can help identify potentially adaptive expressions of psychopathy, such as charismatic leadership and heroic forms of altruism.

References:

  1. Cleckley, H. (1988). The mask of sanity: An attempt to clarify some issues about the so-called psychopathic personality (5th ed.). Augusta, GA: Emily S. Cleckley.
  2. Lilienfeld, S. O., & Andrews, B. P. (1996). Development and preliminary validation of a self-report measure of psychopathic personality traits in noncriminal populations. Journal of Personality Assessment, 66, 488-524.
  3. Lilienfeld, S. O., & Widows, M. R. (2005). Psychopathic Personality Inventory-Revised (PPI-R) professional manual. Lutz, FL: Psychological Assessment Resources.

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