Journal of Personality Disorders, 26(3), 402-413, 2012 © 2012 The Guilford Press

This article was accepted under the editorship of Paul S. Links. From Department of Psychology, Glasgow Caledonian University (M. K. F. K., D. J. C., C. M.); Faculty of Psychology, University of Bergen (D. J. C.); Centre for Research and Education in Forensic Psychiatry, Haukeland University Hospital (H. A. H.); and Greater Manchester West Mental Health NHS Founda-tion Trust, and Department of Psychiatry, University of Manchester (C. L.). Mette K. F. Kreis is now at Section of Clinical and Health Psychology, University of Edinburgh, and NHS Forth Valley. This study is part of the doctoral dissertation of Mette K. F. Kreis. Preliminary data were presented at the annual meeting of the International Association of Forensic Mental Health Services (June 2007), the in-ternational congress of the International Society for the Study of Personality Disorders (September 2007), and the Scottish Personality Disorder Network conference (May 2008). The research was supported by a Studentship and Research Student Travel grant from Glasgow Caledonian University, and research grants from NHS Greater Glasgow and Clyde Research and Development Directorate, and the Carnegie Trust for the Universities of Scotland. We thank Stephen D. Hart for his advice on the study design, the mental health professionals who took part in the study, and the organizations who allowed us to recruit from their members. Mette K. F. Kreis thanks Lisa Marshall, Liz Gilchrist, and Corine de Ruiter for their help-ful suggestions for improving the results.Address correspondence to Mette K. F. Kreis, Section of Clinical and Health Psychology, School of Health in Social Science, University of Edinburgh, Medical School, Teviot Place, Edinburgh, EH8 9AG, UK; E-mail: mettekreis@nhs.net

CONTENT VALIDATION OF THE CAPPKREIS ET AL.

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THE COMPREHENSIVE ASSESSMENT Of PSYCHOPATHIC PERSONALITY (CAPP): CONTENT VALIDATION USING PROTOTYPICAL ANALYSIS

Mette K. F. Kreis, PhD, David J. Cooke, PhD, FRSE, Christine Michie, BSc, Helge A. Hoff, MSc, and Caroline Logan, DPhil

The Comprehensive Assessment of Psychopathic Personality (CAPP; Cooke, Hart, Logan, & Michie, 2004) is a new personality-based model and clinical assessment of psychopathy. This study was the first to examine the content validity of the English-language CAPP. Content validation is a crucial part of the development and refinement of any new instrument. Prototypical analysis was used to evaluate the representativeness of CAPP symptoms to the psychopathy construct in adults. Symptoms were rated by international mental health professionals (N = 132). Findings support good content validity of the CAPP, with most symptoms rated as highly represen-tative of psychopathy. Domains relating to interpersonal style were par-ticularly prototypical. Confirmatory factor analyses further suggested that CAPP domains are highly unidimensional. However, some CAPP symptoms may be weaker items in the model and further refinement is needed.

The Comprehensive Assessment of Psychopathic Personality (CAPP; Cooke, Hart, Logan, & Michie, 2004) is a new model and clinical assessment of

CONTENT VALIDATION OF THE CAPP 403

psychopathy, comprising a semistructured interview and a staff rating scale. The CAPP was developed to provide a clinically informed, dynamic, person-ality-based conceptualization of psychopathy, with the potential to measure change in symptom severity over time, for example as a response to treat-ment. Current psychopathy measures (e.g., the Psychopathy Checklist-Re-vised [PCL-R]; Hare, 2003) are static and not designed to measure change. The CAPP was developed through a systematic and rigorous process as a comprehensive model of psychopathic personality disorder, covering the full range of psychopathic symptoms (see Comprehensive Assessment of Psycho-pathic Personality, 2008; Cooke et al., 2004; Cooke, Hart, Logan, & Michie, 2011). The CAPP model comprises six domains (i.e., Attachment, Behav-ioral, Cognitive, Dominance, Emotional, and Self) and 33 symptoms, each symptom defined by a number of trait-descriptive adjectives. The focus is on personality traits rather than potential behavioral consequences of personal-ity pathology. In this way the CAPP avoids the confounding of personality traits and specific behavioral acts (e.g., antisocial and criminal behavior), which adversely affects certain measures of psychopathy (e.g., Lilienfeld, 1994; Skeem & Cooke, 2010a, 2010b).

The CAPP model was developed using a lexical approach, which de-scribes traits using natural language descriptors (Goldberg, 1993). Impor-tantly, the CAPP items were broadly sampled with a focus on breadth over narrowness to avoid construct underrepresentation. Broad sampling of con-struct criteria is critical in the early stages of instrument development to ensure adequate representation of the construct (Clark & Watson, 1995; Smith, Fischer, & Fister, 2003). Systematic analyses help establish the ap-propriateness of content and refine an instrument. It was assumed from the outset that some CAPP items would be more relevant to psychopathy than others. The process of identifying potentially weak items and strengthening the CAPP model starts with content validation.

Content validity refers to the degree to which instrument items or diag-nostic criteria adequately represent the target construct (Blashfield & Lives-ley, 1991; Broughton, 1990; Haynes, Richard, & Kubany, 1995). It is not only an essential part of the overall construct validation process but also its key starting point (Clark & Watson, 1995; Cronbach & Meehl, 1955; Foster & Cone, 1995; Haynes et al., 1995) and is fundamental to accurate diagno-sis of mental disorders, including personality disorders (Blashfield & Lives-ley, 1991; Livesley, Reiffer, Sheldon, & West, 1987). Failure to perform this crucial first step in the construct validation of a new measure significantly limits the meaning of instrument scores in relation to the target construct (Haynes et al., 1995).

Content validity can be examined through prototypical analysis, an ap-proach developed from prototype theory as a way of evaluating a construct’s core characteristics (Broughton, 1990). A prototype is the best example of a category or concept, characterized by features central to members of that particular category (Rosch, 1978). Yet the prototype is a theoretical ideal or a measure of category members’ “goodness-of-fit” (i.e., his or her prototypi-cality) rather than a description of discrete membership criteria. Category boundaries are not clear-cut; members must have some of the prototype’s

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features but will match it to varying degrees. However, the more a member resembles the prototype, the more that member exemplifies the construct (Broughton, 1990; Rosch, 1978).

Prototypical analysis frequently uses a panel of expert judges to evaluate the representativeness of the construct criteria (Blashfield & Livesley, 1991; Livesley et al., 1987). The approach is useful in the content validation of personality disorders because they have fuzzy boundaries with a high degree of criterion overlap. Prototypical analysis has previously been successfully used in the construct validation of personality disorders, including antisocial personality disorder and psychopathy (e.g., Cruise, Colwell, Lyons, & Baker, 2003; Rogers, Duncan, Lynett, & Sewell, 1994; Salekin, Rogers, & Machin, 2001). However, previous psychopathy prototypicality studies focused on adolescent psychopathy with an overemphasis on behavioral criteria (i.e., for conduct disorder, oppositional defiant disorder, and antisocial personality disorder). This is problematic because, although overlapping in some cri-teria, antisocial personality disorder is not equivalent to psychopathy (e.g., Hare, 1998; Lilienfeld, 1994).

This study provides the first content validation of the original English-language CAPP. The CAPP is translated into 16 languages, with several in-ternational research projects on its construct validity (e.g., content, conver-gent, discriminant, and predictive validity) and reliability either completed or ongoing (see Comprehensive Assessment of Psychopathic Personality, 2008; Hoff, Rypdal, Mykletun, & Cooke, in press; Pedersen, Kunz, Elsass, & Ras-mussen, 2010). The aim of the present study was to use prototypical analysis to determine the general relevance of CAPP symptoms to psychopathy in adults, both in terms of sensitivity and specificity.

METHODPARTICIPANTS

Mental health professionals experienced in working with (as practitioners or researchers) adult psychopathic male and female clients/research participants were sampled from a variety of sources: The International Association of Fo-rensic Mental Health Services (IAFMHS), the Society for the Scientific Study of Psychopathy (SSSP), the International Society for the Study of Personality Disorders (ISSPD), the British and Irish Group for the Study of Personal-ity Disorder (BIGSPD), the Scottish Personality Disorder Network, PCL-R training workshops, and personal contacts. Approximately 1,200 people were contacted and invited to take part in the study. The exact number of people contacted is unknown due to the use of a “snowballing” method whereby contacts forwarded the questionnaire to colleagues. In total 138 questionnaires were returned, resulting in a low response rate of 11.5%. A number of people also responded to say they were ineligible for participa-tion. Four questionnaires were discarded due to incomplete data, and two were excluded at the analysis stage due to a high level of extreme outliers, suggesting misinterpretation of the response scale.

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The final sample consisted of 132 international mental health profession-als, with an even gender split of 67 men (50.8%) and 65 women (49.2%). The mean age was 42.4 (SD = 10.3, range 24–63). Twenty-one different nationalities and six world regions were represented, with most participants from Europe (67.4%) and North America (24%). Most were psychologists (61.5%) and psychiatrists (26.9%), with other professions reported as com-munity psychiatric nurse, criminologist, or other. Most participants worked in hospitals (43.5%) or academia (31.3%). Approximately 60% worked mainly as clinicians (63.8%) and 36.2% mainly as researchers.

Participants had on average 9.5 (SD = 7.3, range 0–31) years of experi-ence working in forensic settings, 12.1 (SD = 7.7, range 0–31) years average experience working with personality disorders in general, and 9.7 (SD = 7.6, range 0.5–35) years average experience working specifically with psychopa-thy. Most participants (90.9%) used structured assessments of personality in their work, the majority on a regular basis (66.9%), with the PCL (e.g., PCL-R; Hare, 2003) instruments the most frequently used (62.7%).

MEASURE

A two-part questionnaire was developed based on the CAPP model (Cooke et al., 2004). Part 1 asked participants to rate 42 symptoms according to how prototypical they thought these were of psychopathy in general. Part 2 asked them to rate the symptoms in relation to a specific psychopathic client they had worked with, as well as a specific nonpsychopathic client, thus pro-viding information about both sensitivity and specificity to psychopathy. The 42 symptoms consisted of the 33 CAPP symptoms and nine foil or control symptoms (i.e., Self-conscious, Shy, Considerate, Strange, Perfectionist, Re-strained, Conscientious, Cautious, and Dependent) considered theoretically irrelevant to psychopathy. Prototypicality of psychopathy was rated on a 7-point Likert scale from 1 (low prototypicality) to 7 (high prototypicality).

PROCEDURE

Participants were sampled through various methods. Delegates were ap-proached personally at international forensic mental health conferences (e.g., the IAFMHS) and invited to participate in the study. If they agreed, they were provided with a copy of the questionnaire, which was returned to a drop-box at the conference or by post. An electronic version of the question-naire was also developed and e-mailed to members of relevant international organizations (e.g., ISSPD) or their conference delegates, and to attendees at PCL-R workshops run by one of the authors. Finally, participants were sampled from universities and forensic mental health facilities through per-sonal contacts, and some participants forwarded the electronic questionnaire to colleagues.

The study had ethical approval from the Ethics Committee, School of Life Sciences, Glasgow Caledonian University. Participation was voluntary and confidential, and no identifying information was attached to completed questionnaires.

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ANALYSES

The data were mainly analyzed using prototypical analysis, a descriptive analysis using means and standard deviations. Distribution of scores was further explored using histograms and median and modal values. Group dif-ferences were examined using t tests. Confirmatory factor analyses examined the CAPP model at domain level to determine the dimensionality of domains (Smith, McCarthy, & Zapolski, 2009).

TaBle 1. General Prototypicality Ratings

Symptom M SD Mdn Mode Range

Lacks remorse E 6.56 0.72 7.0 7.0 2–7Unempathic A 6.49 0.85 7.0 7.0 1–7Self-centered S 6.48 0.69 7.0 7.0 4–7Manipulative D 6.44 0.74 7.0 7.0 3–7Lacks emotional depth E 6.40 0.82 7.0 7.0 3–7Deceitful D 6.27 0.73 6.0 7.0 4–7Insincere D 6.26 0.83 6.0 7.0 3–7Self-aggrandizing S 6.14 0.84 6.0 6.0 2–7Sense of entitlement S 6.03 1.29 6.0 7.0 1–7Self-justifying S 6.03 1.03 6.0 6.0 1–7Unreliable B 5.99 1.19 6.0 6.0 3–7Uncaring A 5.93 0.98 6.0 6.0 2–7Reckless B 5.75 1.07 6.0 6.0 1–7Domineering D 5.72 1.13 6.0 6.0 2–7Aggressive B 5.64 1.10 6.0 6.0 2–7Detached A 5.64 1.32 6.0 6.0 1–7Sense of invulnerability S 5.61 1.08 6.0 6.0 1–7Disruptive B 5.58 1.04 6.0 6.0 2–7Sense of uniqueness S 5.58 1.18 6.0 6.0 2–7Intolerant C 5.40 1.18 6.0 6.0 2–7Uncommitted A 5.37 1.35 6.0 5.0 1–7Antagonistic D 5.19 1.35 5.0 6.0 1–7Restless B 5.16 1.42 6.0 6.0 1–7Lacks anxiety E 5.11 1.55 6.0 6.0 1–7Lacks planfulness C 5.00 1.46 5.0 5.0 1–7Lacks perseverance B 4.83 1.39 5.0 5.0 1–7Suspicious C 4.83 1.33 5.0 5.0 1–7Lacks emotional stability E 4.74 1.72 5.0 6.0 1–7Inflexible C 4.60 1.49 5.0 5.0 1–7Garrulous D 4.50 1.51 5.0 5.0 1–7Unstable self-concept S 3.96 1.69 4.0 5.0 1–7Lacks concentration C 3.84 1.48 4.0 5.0 1–7Lacks pleasure E 3.22 1.59 3.0 2.0 1–6Self-conscious F 3.14 2.01 2.0 1.0 1–7Strange F 3.03 1.47 3.0 2.0 1–7Perfectionist F 2.63 1.50 2.0 2.0 1–7Restrained F 2.46 1.48 2.0 2.0 1–7Dependent F 2.41 1.41 2.0 2.0 1–7Cautious F 2.12 1.31 2.0 1.0 1–6Conscientious F 1.96 1.52 1.0 1.0 1–7Considerate F 1.67 1.25 1.0 1.0 1–7Shy F 1.66 1.13 1.0 1.0 1–7

Note. Gray highlight = foil symptoms; high prototypicality = M ≥ 5; where multiple modes exist, the smallest value is shown; A = Attachment domain, B = Behavioral domain, C = Cognitive domain, D = Dominance domain, E = Emo-tional domain, S = Self domain, F = foil symptom.

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RESULTSGENERAL PROTOTYPICALITY RATINGS: SYMPTOM SENSITIVITY

Table 1 presents the results for the general prototypicality ratings. Twenty-five out of 33 CAPP symptoms were rated as highly (M ≥ 5) prototypical of psychopathy, with 10 symptoms (i.e., Lacks remorse, Unempathic, Self-centered, Manipulative, Lacks emotional depth, Deceitful, Insincere, Self-aggrandizing, Sense of entitlement, and Self-justifying) rated as very high (M ≥ 6). Notably, many of these symptoms are also part of the PCL-R (Hare, 2003). Only three CAPP symptoms have medium to low mean ratings (i.e., Unstable self-concept, M = 3.96, SD = 1.69; Lacks concentration, M = 3.84, SD = 1.48; Lacks pleasure, M = 3.22, SD = 1.59). As would be expected, the nine foil symptoms have the lowest prototypicality ratings (M = 2.34, SD = 0.50), with most individual mean scores below 3 (range = 3.14 to 1.66), indicating they were generally judged to be unrepresentative of psychopathy. The results suggest that the vast majority of CAPP symptoms are highly rep-resentative of psychopathy, supporting good content validity of the CAPP instrument and the sensitivity of CAPP items to the psychopathy construct.

Most symptoms have standard deviations above 1.00 and were rated with the full range of the Likert scale (from 1 to 7), suggesting a high degree of variation in scores. However, the median and modal values indicate that any variation is likely due to outliers. All CAPP symptoms, except for the three lowest in prototypicality (i.e., Unstable self-concept, Lacks concentra-tion, Lacks pleasure), have central values (medians) of 5 or above, with most of them 6 or above. The most frequently occurring values (modes) are also 5 or above for all but the lowest CAPP symptom (i.e., Lacks pleasure). In contrast, all foil symptoms have medians of 3 or below and modes of 2 or below. Inspection of the distribution of scores using histograms confirmed that the variation in scores was due to inconsistent outliers. This may re-flect rating errors but could also reflect natural variation in scores due to various sample factors. Possible rating differences related to culture (Europe vs. North America), rater gender, professional background (psychologist vs. psychiatrist), and professional status (academic vs. clinician) were explored with independent t tests. No significant differences were found for any of these factors beyond what would be expected by chance when conducting multiple significance tests, with no pattern emerging. Differences related to level of experience with psychopathy were explored with an independent one-way ANOVA, but power was too low to detect any pattern.

GENERAL PROTOTYPICALITY RATINGS: CAPP DOMAIN RANKS

The prototypicality ratings were also explored at CAPP domain level. Do-main ranks were found by adding up the mean ratings of all symptoms in each domain and calculating their respective standard deviations. All but the Cognitive domain were highly (M ≥ 5) prototypical of psychopathy, with the following rank order: 1. Attachment (M = 5.85, SD = 0.41), 2. Dominance (M = 5.73, SD = 0.69), 3. Self (M = 5.69, SD = 0.76), 4. Behavioral (M = 5.49, SD = 0.38), 5. Emotional (M = 5.20, SD = 1.27), and 6. Cognitive (M

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= 4.73, SD = 0.51). Thus this sample of mental health professionals con-sidered domains relevant to interpersonal style—Attachment, Dominance, and Self—most prototypical of psychopathy. The Emotional domain has the largest standard deviation, which is not surprising as two symptoms from this domain (i.e., Lacks remorse and Lacks pleasure) have both the highest and the lowest general prototypicality ratings overall (see Table 1).

DIMENSIONALITY OF DOMAINS

The dimensionality of the CAPP domains is important both theoretically and from the perspective of developing a good measurement model. The theoretical importance of identifying unidimensionality of domains is clearly stated by Smith and colleagues (2009): “Only measures of unidimensional constructs can lay claim to explaining psychological processes and hence to explaining possible causal activity” (p. 277). Following Smith et al. (2009), we applied confirmatory factor analytic (CFA) procedures to evaluate wheth-er the symptoms within the domains could be characterized as measuring unidimensional constructs. We examined each domain in turn. Maximum likelihood estimation with robust fit statistics and standard errors was used. The correlations were polychorics. Recommendations in the electronic help manual for the EQS 6 software suggest that this estimation approach is the best EQS approach for data of this type. The overall fit of the model was assessed using the Satorra–Bentler Scaled χ2 test (Bentler & Wu, 1995). This fit index is more likely to have the expected distribution when the assump-tion of normality is not met. It is well recognized that this test is sensitive to sample size and will generally be significant in samples even of moder-ate size. A nonsignificant value of Satorra-Bentler Scaled χ2 test is indicative of unidimensionality. We also considered the robust Comparative Fit Index (CFI) following convention; adequate fit was determined as a CFI coefficient greater than .90 (Byrne, 1994; Greenbaum & Dedrick, 1998). We did not

TaBle 2. Confirmatory Factor analysis of the CaPP Domains

Fit Statistics

Domain χ2 df CFI RMSea

Attachment 0.8ns 2 1.00 0.00

Behavioral 10.3ns 9 0.99 0.03

Cognitive 13.0* 5 0.86 0.11

Cognitive – C5 1.0ns 2 1.00 0.00

Dominance 32.9*** 9 0.88 0.15

Dominance – D1 8.4ns 5 0.98 0.08

Emotional 15.4** 5 0.75 0.13

Emotional – E2 3.2ns 2 0.96 0.07

Self 26.9* 14 0.92 0.09

Self – S7 15.9ns 9 0.96 0.08

Note. C5 = Lacks planfulness symptom, D1 = Antagonistic symptom, E2 = Lacks pleasure symptom, S7 = Unstable self-concept symptom; ns = nonsignificant, * = p < .05, ** = p < .01, *** = p < .001.

CONTENT VALIDATION OF THE CAPP 409

interpret the RMSEA values because they can be misleading when there are few variables in the model and the sample size is not large.

Examination of Table 2 found that the Attachment domain (4 symp-toms) and the Behavioral domain (6 symptoms) both achieved a good fit with the χ2 test values being nonsignificant in each case. These results in-dicate that in each case a unidimensional construct is being measured. The other four domains required modification before good fit could be achieved. The Cognitive domain (5 symptoms) did not achieve an adequate fit. Consid-eration of factor loadings and intersymptom correlations suggested that the symptom Lacks planfulness should be removed because it resulted in mul-tidimensionality in the measurement of the domain. Removal of that item resulted in a good fit. The Dominance domain (6 symptoms) did not achieve an adequate fit. Removal of the symptom Antagonistic resulted in a good fit. Similarly, for the Emotional domain (5 symptoms), removal of the symptom Lacks pleasure resulted in a good fit. With the Self domain (7 symptoms), the initial model with all 7 items provided a poor fit; however, the removal of the symptom Unstable self-concept resulted in a good fit.

SPECIFIC CLIENT PROTOTYPICALITY RATINGS: SYMPTOM SPECIFICITY

Part 2 of the questionnaire provided information about the specificity of symptoms to psychopathy. When symptoms are rated as high in prototypi-cality of psychopathy, it only indicates that they are sensitive to the construct, meaning that they will pick up the majority of psychopathic individuals. If the same symptoms are rated as low in prototypicality for nonpsychopathic clients, it would indicate that symptoms are also specific to psychopathy and not to personality disorder in general. The most common main psychiatric diagnoses for the psychopathic clients were antisocial personality disorder (31.8%) and psychopathy (21.3%). For the nonpsychopathic clients, they were personality disorder (30.2%), most commonly borderline personality disorder (51.7%) and dependent personality disorder (13.8%), schizophre-nia or other psychotic disorder (28.4%), and mood disorder (18.1%).

As demonstrated in Figure 1, there were clear differences in the proto-typicality ratings for psychopathic and nonpsychopathic clients, also com-pared to the general prototypicality ratings. Noticeably their ratings are almost mirror images of each other, in opposite directions. For the psycho-pathic client, 23 CAPP symptoms were rated as high in prototypicality of psychopathy (M ≥ 5), similar to the general prototypicality ratings (see Table 1), and all the foil symptoms as moderate to low (M < 4) in prototypicality. The nonpsychopathic client has no high prototypicality ratings, and all but two of the CAPP symptoms (i.e., Unstable self-concept and Lacks emotional stability) were rated as low in prototypicality, with the majority rated below 3. The foil symptoms have medium to low prototypicality ratings. A paired t test (two-tailed) found a significant difference in the mean symptom ratings between the psychopathic and nonpsychopathic client for all but three of the CAPP symptoms (i.e., Unstable self-concept, Lacks concentration, and Lacks pleasure). These symptoms were also low in general prototypicality (Table

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1), with two of them (i.e., Unstable self-concept and Lacks pleasure) found to provide a poor fit in the CFA. This suggests that in addition to being sensi-tive to psychopathy, the majority of CAPP symptoms are also highly specific to the construct. Yet it further suggests that Unstable self-concept, Lacks concentration, and Lacks pleasure are weaker items in the CAPP model.

DISCUSSION

This study was the first to examine the content validity of the original English-language CAPP (Cooke et al., 2004) using prototypical analysis. The study found good content validity of the CAPP, with the majority of CAPP symp-toms highly representative of psychopathy, both in sensitivity and specificity. This suggests that most CAPP symptoms are not only sensitive to picking up psychopathy but also highly specific to the construct.

The symptoms considered particularly prototypical of psychopathy were Lacks remorse, Unempathic, Self-centered, Manipulative, Lacks emotional depth, Deceitful, Insincere, Self-aggrandizing, Sense of entitlement, and Self-justifying. Of note, many of these also feature in the PCL-R (Hare, 2003). This could mean they are simply core to the construct; yet it might also re-flect the fact that most participants reported regularly using the PCL instru-ments (e.g., the PCL-R; Hare, 2003) in their practice, together with these instruments’ great influence over the field’s conceptualization of psychopathy (Salekin, 2002; Skeem & Cooke, 2010b). This means ratings may have been subject to a degree of PCL measurement bias. However, in a prototypical-ity study of the Norwegian-language CAPP, Hoff et al. (in press) found no significant differences between how lay people and mental health profession-

FIGURE 1. Specific client prototypicality ratings compared to general prototypicality ratings. A = Attachment domain, B = Behavioral do-main, C = Cognitive domain, E = Emotional domain, S = Self domain, F = foil symptom.

CONTENT VALIDATION OF THE CAPP 411

als rated the symptoms. This suggests that measurement bias may not be an issue.

The symptoms Unstable self-concept, Lacks pleasure, and Lacks con-centration were given the lowest (medium to low) prototypicality ratings, which suggests that they are less representative of psychopathy and possibly weaker items in the CAPP model. A CFA confirmed this for Lacks pleasure and Unstable self-concept and suggested that the symptoms Antagonistic and Lacks planfulness may also be weaker items. Of course, the CAPP model was specifically developed to be broad to avoid construct underrepresentation. Some of the weaker items (e.g., Lacks pleasure) were regarded by the devel-opers as being at the margin of the construct. It is through content validation that weaker items are identified and the model refined. The current findings have also been confirmed by Hoff et al. (in press) and in other analyses of the CAPP model (Cooke et al., 2011).

Importantly, the fact that some CAPP symptoms may be less representa-tive of psychopathy than others does not mean they should necessarily be eliminated from the CAPP model. According to prototype theory, a prototype is a theoretical ideal that not all—or possibly any—members of the category will perfectly resemble (e.g., Broughton, 1990). Thus not all psychopathic individuals are expected to present precisely the same symptom profile. Rare or less prototypical symptoms may have clinical significance in relation to, for example, violence risk management (Cooke, 2010).

At domain level, the mental health professionals in this study considered the CAPP domains relevant to interpersonal style—Attachment, Dominance, and Self—to be most prototypical of psychopathy, followed by the Behav-ioral and Emotional domains. Importantly, both Attachment and Self are domains clearly articulated in the CAPP. In our opinion, attachment to oth-ers and self-awareness are not sufficiently represented in current measures of psychopathy, and neither is interpersonal style generally. The Cognitive domain was considered least prototypical of psychopathy. This could reflect the fact that cognitive symptoms are not generally well represented in com-mon measures of psychopathy or are harder to access and assess. Further-more, it would appear that it is possible to demonstrate that unidimensional measures of each domain can be achieved, in some cases through the use of the total symptom set in the domain, and in other cases through the removal of a symptom that does not conform. If replicated across samples and data collection methods, this information should lead to more coherent and theo-retically defensible measures of the core domains of psychopathy (Smith et al., 2009).

Some potential limitations of the study should be noted, one being the possible “PCL psychopathy” measurement bias mentioned earlier. The low response rate limits the generalizability of the current findings and suggests that the questionnaire may have been too long. Future studies may use either Part 1 or Part 2 of the questionnaire rather than both. Online survey software would also provide a more efficient way of collecting data, enabling a larg-er sample size. Another potential limitation was the lack of clarification of symptoms. Feedback from some participants, particularly nonnative English speakers, indicated they would have found clarification useful. CAPP trait

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adjectival descriptors of symptoms were not included in the questionnaire to keep the focus on symptoms, which were developed to be easily understood (Cooke et al., 2004). However, future studies would benefit from including them in brackets to help clarify and define the meaning of symptoms.

Overall, the findings support the comprehensiveness of the CAPP model relative to current measures and conceptualizations of psychopathy. Natural-ly, the CAPP needs further content validation as part of its ongoing construct validation process. The current findings need to be replicated across larger samples and other cultures, using both the English CAPP and its translations. Yet, like other findings on the CAPP model (Hoff et al., in press), these find-ings suggest that the CAPP captures the psychopathy construct well. This has important implications for practice and research. If the CAPP provides a more accurate representation of psychopathy than other measures, it will enable more valid and reliable assessment of the construct, and ultimately improve risk formulation, risk management, and intervention.

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