Levenson Self-Report Psychopathy Scale

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The Levenson Self-Report Psychopathy scale (LSRP) is a 26-item, 4-point Likert scale, self-report inventory to measure primary and secondary psychopathy in non-institutionalised populations. It was developed in 1995 by Michael R. Levenson, Kent A. Kiehl and Cory M. Fitzpatrick. The scale was created for the purpose of conducting a psychological study examining antisocial disposition among a sample of 487 undergraduate students attending psychology classes at the University of California, Davis. [1]

Contents

Primary and Secondary Psychopathy

Background

Benjamin Karpman first theorised that psychopathy should be divided into two clinical subtypes in 1941. [2] He believed that psychopathy presented itself in either a symptomatic or idiopathic manner. Symptomatic psychopathy referred to an individual who would exhibit psychopathic traits usually as a result of an underlying psychoneurosis or character neurosis. Idiopathic psychopathy, on the other hand, presented itself without a cause and rarely reacted to treatment. [3] Karpman's theory has helped researchers to identify two subgroups of those who display psychopathic traits. These were subsequently labelled as primary and secondary psychopaths. [4]

Primary Psychopathy

The subtype known as "primary" psychopathy refers to individuals who are completely rational, lack anxiety and have high levels of interpersonal charm. Whilst these behaviours appear incredibly adaptive, primary psychopaths are also prone to dysfunctional and pathological traits such as an inability to learn from past mistakes and a lack of responsibility. [4] Primary psychopaths may present few symptoms of having a major psychological disorder. This may go hand in hand with the more manipulative personality traits characterising primary psychopathic behaviour. In addition, manipulation is also a key component featured in the Dark Triad personality test (Machiavellianism), which is positively correlated with primary psychopathy. [5] It has also been further suggested that primary psychopathy and Machiavellianism reflect similar constructs, with Machiavellian behaviour being positively associated with the main traits of primary psychopathy. [5] [6] Further research has shown that psychopathy and Machiavellianism are "barely distinguishable" and features of the two often "overlap". [6] This is further supported by research showing that Machiavellianism and primary psychopathy are situated in much of the same areas of the Interpersonal Circumplex., i.e., "cold-hearted" and "high dominance" sections. [5] Other traits include impaired interpersonal skills, not being able to function adequately in social situations due to the mere nature of the traits such as a lack of empathy.

Secondary Psychopathy

"Secondary" psychopaths are individuals not dissimilar to primary psychopaths in the sense that they still share many of the same characteristics and traits. However, unlike the primary psychopath, the secondary psychopath is more likely to suffer from intense emotional arousal and psychological issues. As well as this, research conducted on adult psychopaths has suggested that secondary psychopaths are more prone to participate in drug abuse, suicide and interpersonal aggression. Research suggests that secondary psychopathic traits may include remorse and being more tense in contrast to individuals labelled as primary psychopaths. Karpman believed that behaviours carried out by secondary psychopaths aren’t grounded in lack of empathy which is seen in primary psychopaths. [7] An integral finding amongst secondary psychopathic traits is the tendency to be less risk averse and more risk tolerant. For example, a study showed that individuals with secondary psychopathic traits were more likely to consistently choose cards with considerably higher net loses opposed to ones that posed less risk and gain. [7] This is consistent with other research, which also suggests a consistent positive association between impulsivity and secondary psychopathy. Whilst controlling for impulsivity, risky decision making was still prevalent amongst secondary psychopathic behaviour. [7] [8] Overall, what differentiates secondary psychopaths from primary psychopaths is their destructive behaviour as well an increased reactivity and impulsivity and an inability to control their emotions effectively. [4]

Evaluation

Studies have supported the existence of these two subgroups. For example, after, a questionnaire assessing personality was distributed to 96 psychopathic male prisoners, the researchers conducting the study concluded the best-fitting model for the differences in personality was two separate groups. One group was labelled "emotionally stable psychopaths" and the other was labelled "aggressive psychopaths". The aggressive psychopaths were more emotionally reactive and lacked control whereas the emotionally stable psychopaths had high levels of achievement and social skills and low levels of stress reaction. [9]

Development and Scoring

The purpose of the scale was to test for these two sub-groups of primary and secondary psychopathy as identified by Karpman as well as their attributions with "prosocial and antisocial behaviours". This was aimed at “non-institutionalised” populations in Levenson’s study. [1] [7]

The LSRP is partially based on Robert D. Hare's diagnostic Psychopathy Checklist-Revised (PCL-R) and consists of 26 statements which participants must decide their attitudes towards using a 4-point Likert scale ("disagree strongly", "disagree somewhat", "agree somewhat" and "agree strongly"). Seven of the items were reversed to reduce response bias. [10]

The PCL-R is one of the key assessments used to signal psychopathy and traits associated with it in individuals, mainly used on institutionalised individuals in the population in contrast to the LSRP. The LSRP aimed to measure similarly what the PCL-R does by using similar “descriptors” for behavioural traits. These include tendency for regular deception, lack of empathy and remorse and Machiavellian behaviour. [1]

Examples of items from the self-report scale include: "I tell other people what they want to hear so that they will do what I want them to do" and "I often admire a really clever scam". [1] These statements aimed to focus on typical moral dilemmas one may face as opposed to accentuating criminal behaviour. [1] [10] This was to account for the LSRP’s use on university students, making the scale easier to conceptualise. [11] The wording of these response options is made to lessen the stigma around personality traits by reducing any means of condemnation. [1] [7]

A factor analysis was initially conducted on the items in the LSRP and two factors (primary and secondary psychopathy) were derived from the scale. [10] 16 of the statements from the scale determined primary psychopathy and the remaining 10 determined secondary psychopathy. The statements that were attributed to primary psychopathy were more to do with manipulation and a lack of empathy whereas the statements attributed to secondary psychopathy were focused on behavioural issues. [1] : 152–153 

Based on the results of the initial study, the following thresholds for the results were established:

Criticism

Validity

Construct validity

The LSRP intends to measure the same constructs as the PCL-R. Significant correlations suggest that the LSRP does correlate with the PCL-R for both factors of psychopathy. A study by Chad Brinkley in 2001 tested the concurrent and construct validity of the LSRP with the PCL-R with a sample of prison inmates. [10] Small to moderate correlations were found between the LSRP and PCL-R, as well as associations between primary and secondary psychopathy ("factor 1" and "factor 2" in the PCL-R). Although the total correlations between the two measures were small, this was still nevertheless a significant finding from further statistical testing. This finding was also predominantly consistent across different demographics within the sample. However, these correlations being small to moderate suggest that the LSRP and PCL-R are measuring somewhat different constructs. [10] : 1035 

A study by Martin Sellbom in 2010 also studied male inmates and college students to assess construct validity in the LSRP. [12] It was compared with various other measures such as the "Psychopathic Personality Inventory” (PPI), the “Machiavellianism Inventory-IV” and the “Emotional Empathy Scale”. Results signalled the LSRP had strong correlations with some aspects of these measures which tested for narcissistic, impulsive traits and prevalence of substance abuse. [12] There were overall moderate correlations between the LSRP and the PPI but no significant correlations with the Emotional Empathy Scale. The LSRP therefore partially correlates with other predominant measures of psychopathy, but these correlations are not consistent across all self-report measures, with some differences seen between institutionalised and non-institutionalised populations. [10] [12]

Further research tested the LSPR against a range of other self-report measures which explored concepts associated with psychopathic behavioural traits. After analysing this, findings showed that there were correlations between the LSRP and other self-report measures assessing similar conducts such as "harm avoidance". [1] [10]

Internal validity

The LSRP suffers much of the same problems as other self-reported data. As the participant is completing the form themselves, they are more likely to be subject to biases that can change how they answer questions and thus jeopardise the internal validity of the data. An example of such is the recall bias in which participants must recall what they believe to be relevant information to complete the self-report. However, without the presence of an interviewer who is able to guide the participants thought process, the participant may be using incorrect information that they called upon to answer a question. The potential for this problem is much higher in self-reported data than interviews. [13]

Self-report psychopathy measures are susceptible to social desirability bias, in which individuals may alter their given responses according to what they think is socially acceptable or “desired”, therefore possibly giving unrepresentative psychopathy characteristics for that individual. This could stem from certain stigmas surrounding mental health disorders. This threats the internal validity of the assessment as the nature of the questionnaire may produce inaccurate findings of the population’s behavioural dispositions and thus the scale is not measuring what it intends to measure. For example, in Levenson’s study, responses could lead to wrong grouping of individuals, such as being classed as non-psychopathic when actual responses may lead to being put into the psychopathic group due to “underreporting”. However, an analysis into the effects of this bias on the LSRP and other measures found a negative relationship between psychopathy measures and social desirability, indicating that there was limited social desirability bias in the results. [14] Alternatively, it has been suggested that due to dishonesty being a key feature of psychopathy, using self-report methods to assess people will no doubt lead to mistrust in results. [14]

The cognitive burden of self-reported data is also higher than interviews. The LSRP, being a visual questionnaire, requires literacy skills, a lack of visual impairment and ability to use your hands as well as the ability to follow instructions. Compared to interviews, this increased cognitive burden could result in a lower quality of data. [13] : 281–282 

External validity

To create the LSRP, Levenson et al. only used undergraduate students studying psychology at a specific university. This is an example of selection bias and is likely to have negative implications for the external validity of the scale as the wider population does not consist of only undergraduate students. [15] The development of the LSRP also used a WEIRD sample. This refers to a sample from a western, educated, industrialised, rich, democratic society. The problem with this is that due to the restricted sample, the LSRP may not be generalisable to the other 88% of the population who do not live in WEIRD societies, once again decreasing the external validity of the scale. [16]

Reliability

Internal consistency reliability

Findings on the internal consistency reliability of the LSRP are mixed. A study in 2007 found Cronbach's alpha and mean interitem correlations were sufficient to determine good internal consistency reliability for the total LSRP score as well as the subgroup scores. [17] However, a slightly later study found that the reliability of the items in the LSRP was low and attributed this to a few items in the scale. Once these items were removed, reliability improved. [11]

Related Research Articles

Emotional intelligence (EI) is most often defined as the ability to perceive, use, understand, manage, and handle emotions. People with high emotional intelligence can recognize their own emotions and those of others, use emotional information to guide thinking and behavior, discern between different feelings and label them appropriately, and adjust emotions to adapt to environments.

Antisocial personality disorder is a personality disorder characterized by a limited capacity for empathy and a long-term pattern of disregard or violation of the rights of others. Other notable symptoms include impulsivity and reckless behavior, a lack of remorse after hurting others, deceitfulness, irresponsibility, and aggressive behavior.

<span class="mw-page-title-main">Remorse</span> Distressing emotion experienced by a person who regrets actions they have done in the past

Remorse is a distressing emotion experienced by an individual who regrets actions which they have done in the past that they deem to be shameful, hurtful, or wrong. Remorse is closely allied to guilt and self-directed resentment. When a person regrets an earlier action or failure to act, it may be because of remorse or in response to various other consequences, including being punished for the act or omission. People may express remorse through apologies, trying to repair the damage they've caused, or self-imposed punishments.

<span class="mw-page-title-main">Empathy</span> Capacity to understand or feel what another person is experiencing

Empathy is the capacity to understand or feel what another person is experiencing from within their frame of reference, that is, the capacity to place oneself in another's position. Definitions of empathy encompass a broad range of social, cognitive, and emotional processes primarily concerned with understanding others. Types of empathy include cognitive empathy, emotional empathy, somatic empathy, and spiritual empathy.

Psychopathy is a mental health condition characterized by persistent antisocial behavior, impaired empathy and remorse, and bold, disinhibited, and egotistical traits. Different conceptions of psychopathy have been used throughout history that are only partly overlapping and may sometimes be contradictory.

<span class="mw-page-title-main">Psychopathy Checklist</span> Psychopathy scale

The Psychopathy Checklist or Hare Psychopathy Checklist-Revised, now the Psychopathy Checklist—revised (PCL-R), is a psychological assessment tool that is commonly used to assess the presence and extent of the personality trait psychopathy in individuals—most often those institutionalized in the criminal justice system—and to differentiate those high in this trait from those with antisocial personality disorder, a related diagnosable disorder. It is a 20-item inventory of perceived personality traits and recorded behaviors, intended to be completed on the basis of a semi-structured interview along with a review of "collateral information" such as official records. The psychopath tends to display a constellation or combination of high narcississtic, borderline, and antisocial personality disorder traits, which includes superficial charm, charisma/attractiveness, sexual seductiveness and promiscuity, affective instability, suicidality, lack of empathy, feelings of emptiness, self-harm, and splitting. In addition, sadistic and paranoid traits are usually also present.

Prosocial behavior, or intent to benefit others, is a social behavior that "benefit[s] other people or society as a whole", "such as helping, sharing, donating, co-operating, and volunteering". Obeying the rules and conforming to socially accepted behaviors are also regarded as prosocial behaviors. These actions may be motivated by empathy and by concern about the welfare and rights of others, as well as for egoistic or practical concerns, such as one's social status or reputation, hope for direct or indirect reciprocity, or adherence to one's perceived system of fairness. It may also be motivated by altruism, though the existence of pure altruism is somewhat disputed, and some have argued that this falls into philosophical rather than psychological realm of debate. Evidence suggests that pro sociality is central to the well-being of social groups across a range of scales, including schools. Prosocial behavior in the classroom can have a significant impact on a student's motivation for learning and contributions to the classroom and larger community. In the workplace, prosocial behaviour can have a significant impact on team psychological safety, as well as positive indirect effects on employee's helping behaviors and task performance. Empathy is a strong motive in eliciting prosocial behavior, and has deep evolutionary roots.

<span class="mw-page-title-main">Dark triad</span> Offensive personality types

The dark triad is a psychological theory of personality, first published by Delroy L. Paulhus and Kevin M. Williams in 2002, that describes three notably offensive, but non-pathological personality types: Machiavellianism, sub-clinical narcissism, and sub-clinical psychopathy. Each of these personality types is called dark because each is considered to contain malevolent qualities.

Social adroitness is a personality trait measured in the Jackson Personality Inventory and the Jackson Personality Inventory-Revised. Adroitness is not explicitly measured by these tests, but rather the characteristics are measured through different scales.

In psychology, grandiosity is a sense of superiority, uniqueness, or invulnerability. It may be expressed by exaggerated beliefs regarding one's abilities, the belief that few other people have anything in common with oneself, and that one can only be understood by a few, very special people. The personality trait of grandiosity is principally associated with narcissistic personality disorder (NPD), but also is a feature in the occurrence and expression of antisocial personality disorder, and the manic and hypomanic episodes of bipolar disorder.

The Narcissistic Personality Inventory (NPI) was developed in 1979 by Raskin and Hall, and since then, has become one of the most widely utilized personality measures for non-clinical levels of the trait narcissism. Since its initial development, the NPI has evolved from 220 items to the more commonly employed NPI-40 (1984) and NPI-16 (2006), as well as the novel NPI-1 inventory (2014). Derived from the DSM-III criteria for Narcissistic personality disorder (NPD), the NPI has been employed heavily by personality and social psychology researchers.

In psychology, manipulation is defined as subterfuge designed to influence or control another, usually in a manner which facilitates one's personal aims. The methods used distort or orient the interlocutor's perception of reality, in particular through seduction, suggestion, persuasion and non-voluntary or consensual submission. Definitions for the term vary in which behavior is specifically included, influenced by both culture and whether referring to the general population or used in clinical contexts. Manipulation is generally considered a dishonest form of social influence as it is used at the expense of others.

<span class="mw-page-title-main">HEXACO model of personality structure</span> Six-dimensional model of human personality

The HEXACO model of personality structure is a six-dimensional model of human personality that was created by Ashton and Lee and explained in their book, The H Factor of Personality, based on findings from a series of lexical studies involving several European and Asian languages. The six factors, or dimensions, include Honesty-Humility (H), Emotionality (E), Extraversion (X), Agreeableness (A), Conscientiousness (C), and Openness to Experience (O). Each factor is composed of traits with characteristics indicating high and low levels of the factor. The HEXACO model was developed through similar methods as other trait taxonomies and builds on the work of Costa and McCrae and Goldberg. The model, therefore, shares several common elements with other trait models. However, the HEXACO model is unique mainly due to the addition of the Honesty-Humility dimension.

The Psychopathic Personality Inventory (PPI-Revised) is a personality test for traits associated with psychopathy in adults. The PPI was developed by Scott Lilienfeld and Brian Andrews to assess these traits in non-criminal populations, though it is still used in clinical populations as well. In contrast to other psychopathy measures, such as the Hare Psychopathy Checklist (PCL), the PPI is a self-report scale, rather than interview-based, assessment. It is intended to comprehensively index psychopathic personality traits without assuming particular links to anti-social or criminal behaviors. It also includes measures to detect impression management or careless responding.

The Honesty-Humility factor of the HEXACO model of personality is one of the six basic personality traits. Honesty-Humility is a basic personality trait representing the tendency to be fair and genuine when dealing with others, in the sense of cooperating with others, even when someone might utilize them without suffering retaliation. People with very high levels of the Honesty-Humility avoid manipulating for personal gain, feel little desire to break rules, are uninterested in wealth and luxuries, and feel no special right to elevated social status. Conversely, persons with very low levels on this scale will compliment others to get whatever they want, are inclined to break the rules for personal gains, are motivated by material gain, and feel a strong sense of self-importance.

Callous-unemotional traits (CU) are distinguished by a persistent pattern of behavior that reflects a disregard for others, and also a lack of empathy and generally deficient affect. The interplay between genetic and environmental risk factors may play a role in the expression of these traits as a conduct disorder (CD). While originally conceived as a means of measuring the affective features of psychopathy in children, measures of CU have been validated in university samples and adults.

Structure of Temperament Questionnaire (STQ) is a test to measure 12 biologically and neurochemically based individual differences.

The Dark Triad Dirty Dozen (DTDD) is a brief 12-question personality inventory test to assesses the possible presence of three co-morbid socially maladaptive, dark triad traits: Machiavellianism, narcissism, and psychopathy. The DTDD was developed to identify the dark triad traits among subclinical adult populations. It is a screening test. High scores on the DTDD do not necessary correlate with clinical diagnoses.

<span class="mw-page-title-main">Machiavellianism (psychology)</span> Psychological trait

In the field of personality psychology, Machiavellianism is a personality trait characterized by interpersonal manipulation, indifference to morality, lack of empathy, and a strategic focus on self-interest. Psychologists Richard Christie and Florence Geis named the trait after Niccolò Machiavelli, as they used edited and truncated statements inspired by his works to study variations in human behaviors. Their Mach IV test, a 20-question, Likert-scale personality survey, became the standard self-assessment tool and scale of the Machiavellianism construct. Those who score high on the scale are more likely to have a high level of deceitfulness and a cynical, unempathetic temperament.

The influence of childhood trauma on the development of psychopathy in adulthood remains an active research question. According to Hervey M. Cleckley, a psychopathic person is someone who is able to imitate a normal functioning person, while masking or concealing their lack of internal personality structure. This results in an internal disorder with recurrent deliberate and detrimental conduct. Despite presenting themselves as serious, bright, and charming, psychopathic people are unable to experience true emotions. Robert Hare's two factor model and Christopher Patrick's triarchic model have both been developed to better understand psychopathology; however, whether the root cause is primarily environmental or primarily genetic is still in question.

References

  1. 1 2 3 4 5 6 7 8 Levenson, Michael R.; Kiehl, Kent A.; Fitzpatrick, Cory M. (1995). "Assessing Psychopathic Attributes in a Noninstitutionalized Population". Journal of Personality and Social Psychology. 68 (1): 151–152. doi:10.1037/0022-3514.68.1.151. PMID   7861311.
  2. ↑ Karpman, Ben (1941). "On the need of separating psychopathy into two distinct clinical types: the symptomatic and the idiopathic". Journal of Criminal Psychopathology. 3: 112–137. Retrieved 14 April 2020.
  3. ↑ Arieti, Silvano (October 1963). "Psychopathic personality: Some Views on Its Psychopathology and Psychodynamics". Comprehensive Psychiatry. 4 (5): 301–303. doi:10.1016/S0010-440X(63)80056-5. PMID   14055428.
  4. 1 2 3 Vaughn, Michael G.; Edens, John F.; Howard, Matthew O.; Smith, Shannon Toney (July 2009). "An Investigation of Primary and Secondary Psychopathy in a Statewide Sample of Incarcerated Youth". Youth Violence and Juvenile Injustice. 7 (3): 173. doi:10.1177/1541204009333792. S2CID   143989190.
  5. 1 2 3 McHoskey, John W.; Worzel, William; Szyarto, Christopher (1998). "Machiavellianism and psychopathy". Journal of Personality and Social Psychology. 74 (1): 192–210. doi:10.1037/0022-3514.74.1.192. ISSN   1939-1315. PMID   9457782.
  6. 1 2 Miller, Joshua D.; Hyatt, Courtland S.; Maples-Keller, Jessica L.; Carter, Nathan T.; Lynam, Donald R. (2017). "Psychopathy and Machiavellianism: A Distinction Without a Difference?: Psychopathy and Machiavellianism". Journal of Personality. 85 (4): 439–453. doi:10.1111/jopy.12251. PMID   26971566.
  7. 1 2 3 4 5 Dean, Andy C.; Altstein, Lily L.; Berman, Mitchell E.; Constans, Joseph I.; Sugar, Catherine A.; McCloskey, Michael S. (2013). "Secondary psychopathy, but not primary psychopathy, is associated with risky decision-making in noninstitutionalized young adults". Personality and Individual Differences. 54 (2): 272–277. doi:10.1016/j.paid.2012.09.009. PMC   3505104 . PMID   23185100.
  8. ↑ Miranda Jr, Robert; MacKillop, James; Meyerson, Lori A.; Justus, Alicia; Lovallo, William R. (2009). "Influence of Antisocial and Psychopathic Traits on Decision-Making Biases in Alcoholics". Alcoholism: Clinical and Experimental Research. 33 (5): 817–825. doi:10.1111/j.1530-0277.2009.00901.x. PMC   2846168 . PMID   19298325.
  9. ↑ Hicks, Brian M.; Markon, Kristian E.; Patrick, Christopher J.; Krueger, Rober F.; Newman, Joseph P. (2004). "Identifying Psychopathy Subtypes on the Basis of Personality Structure". Psychological Assessment. 16 (3): 276–281. doi:10.1037/1040-3590.16.3.276. PMID   15456383.
  10. 1 2 3 4 5 6 7 8 Brinkley, Chad A.; Schmitt, William A.; Smith, Steven S.; Newman, Joseph P. (28 September 2000). "Construct validation of a self-report psychopathy scale: does Levenson's self-report psychopathy scale measure the same constructs as Hare's psychopathy checklist-revised?". Personality and Individual Differences. 31 (7): 1025. doi:10.1016/S0191-8869(00)00178-1 . Retrieved 11 April 2020.
  11. 1 2 Gummelt, Haley D.; Anestis, Joye C.; Carbonell, Joyce L. (2012). "Examining the Levenson Self Report Psychopathy Scale using a Graded Response Model". Personality and Individual Differences. 53 (8): 1002–1006. doi:10.1016/j.paid.2012.07.014.
  12. 1 2 3 Sellbom, Martin (2011). "Elaborating on the construct validity of the Levenson Self-Report Psychopathy Scale in incarcerated and non-incarcerated samples". Law and Human Behavior. 35 (6): 440–451. doi:10.1007/s10979-010-9249-x. ISSN   1573-661X. PMID   20953972. S2CID   20110327.
  13. 1 2 Bowling, Ann (3 May 2005). "Mode of questionnaire administration can have serious effects on data quality". Journal of Public Health. 27 (3): 287. doi: 10.1093/pubmed/fdi031 . PMID   15870099 . Retrieved 11 April 2020.
  14. 1 2 Watts, Ashley L.; Lilienfeld, Scott O.; Edens, John F.; Douglas, Kevin S.; Skeem, Jennifer L.; Verschuere, Bruno; LoPilato, Alexander C. (2016). "Does response distortion statistically affect the relations between self-report psychopathy measures and external criteria?". Psychological Assessment. 28 (3): 294–306. doi: 10.1037/pas0000168 . ISSN   1939-134X. PMID   26121383. S2CID   11125633.
  15. ↑ Fritz, Kyra N.; Lim, Nicholas K. (2018). "Selection Bias". The SAGE Encyclopedia of Educational Research, Measurement, and Evaluation. Thousand Oaks: SAGE Publications, Inc. pp. 1490–1491. ISBN   9781506326139 . Retrieved 12 April 2020.
  16. ↑ Henrich, Joseph; Heine, Steven J.; Norenzayan, Ara (2010). "The weirdest people in the world?". Behavioral and Brain Sciences. 33 (2–3): 61–83, discussion 83-135. doi:10.1017/S0140525X0999152X. hdl: 11858/00-001M-0000-0013-26A1-6 . PMID   20550733. S2CID   220918842 . Retrieved 12 April 2020.
  17. ↑ Falkenbach, Diana; Poythress, Norman; Falki, Marielle; Manchak, Sarah (December 2007). "Reliability and Validity of Two Self-Report Measures of Psychopathy". Assessment. 14 (4): 344–345. doi:10.1177/1073191107305612. PMID   17986652. S2CID   2293298.
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