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Research Article                                                                                                                                        Open Access

## Assessment of the Affective Dimensions of Psychopathy with the Danish version of the Inventory of Callous-Unemotional Traits among Incarcerated Boys: A study of Reliability, Criterion Validity, and Construct Validity

Mickey T. Kongerslev 1* , Sune Bo 1 , Adelle E. Forth 2 , Erik Simonsen 1,3

1 Psychiatric Research Unit, Region Zealand, Denmark 2 Department of Psychology, Carleton University, Ottawa, ON, Canada 3 Institute of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark

*Corresponding author: psymtk@me.com

## Abstract

Background: Callous-unemotional (CU) traits have been found to index an important subgroup of antisocial youth who are at high risk for developing psychopathic personality pathology, and for becoming severe and persistent offenders. On the basis of such research findings, the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, have included a 'with limited prosocial emotions' specifier in the diagnostic criteria for conduct disorder to designate a subtype with high levels of CU traits.  This  creates  the  need  for  psychometrically  sound  measures  for  the  assessment  of  these  traits.  The  self-report questionnaire  Inventory  of  Callous-Unemotional  Traits  (ICU)  was  designed  to  provide  an  efficient,  reliable,  and  valid measure of CU traits among youth populations.

Method: Eighty  Danish  adolescent  boys  between  the  ages  of  15  to  18  years  in  secure  institutions  were  assessed concurrently with the ICU, the Psychopathy Checklist: Youth Version (PCL:YV), self-report measures of aggression and empathy, and ratings of psychosocial problems. Approximately nine days later, the ICU was readministered in a subset of the sample ( n = 40) to examine test-retest reliability.

Results: Internal consistency was satisfactory, and test-retest reliability was excellent. Concurrent validity associations with the PCL:YV ranged from moderate to high. The ICU displayed excellent discriminative validity for identifying persons who displayed  high  levels  of  psychopathic  traits.  CU  traits  were  also  found  to  be  associated  with  psychosocial  impairments, aggression, and reduced empathy.

Conclusions: Overall, these findings support the reliability; construct validity, and criterion validity of the ICU.

Keywords: callous-unemotional  traits;  psychometric;  psychopathy;  PCL:YV;  conduct  disorder;  with  limited  prosocial emotions, personality disorder

## Introduction

## Background

A  growing  research  base  supports  the  notion  that the  presence  of  callous-unemotional  (CU)  traits (e.g.,  lack  of  remorse,  guilt,  or  empathy;  lack  of concern  about  performance;  shallow  or  deficient affect)  is  a  promising  construct  for  designating  a distinct subgroup of conduct-disordered youth who tend to show the most severe, aggressive, and stable patterns of antisocial behaviors (1-4). Available longitudinal follow-up studies indicate that CU traits are relatively stable during childhood (5,6) and from childhood into early adolescence (7,8) and that they are predictive of later antisocial behavior (2), clinical severity  (9),  and  future  psychiatric  difficulties  (10). Studies furthermore suggest that high levels of CU traits during adolescence are associated with psychopathy  in  adulthood  (11-13).  Together  these findings  also  support  the  notion  that  CU  traits constitute the core affective features of the psychopathy (14-18).

Current empirical evidence suggests that CU traits are highly heritable (19) and associated with deficits in  emotional  empathy  in  boys  (20),  processing  of negative  emotional  stimuli  (21-23),  a  proclivity  for proactive and  instrumental aggression (24),  low levels  of  anxiety  and  fearful  inhibition  (25,26),  and decreased sensitivity to punishment cues and reward-oriented response styles (27,28); these findings  are  consistent  with  research  on  psychopathy  in  adulthood.  Furthermore,  studies  suggest that  high-levels  of  CU  traits  are  associated  with differential and  oftentimes poorer responses to typical parenting practices (29-33) and psychotherapeutic treatments (34,35).

On the basis of this research, the construct of CU traits  is  important  to  the  legal  and  mental  health systems, because it seems to help with the identification  of  a  subgroup  of  severely  antisocial and conduct-disordered youth who are at heightened risk of developing psychopathic personality  pathology  in  adulthood,  who  are  more likely  to  reoffend,  and  who  have  unique  treatment requirements (36,37).  Moreover, from a theoretical and research perspective, CU traits are valuable for understanding  the  developmental  psychopathology of  antisocial  behaviors  and  psychopathy,  including early precursor signs and symptoms, course, stability and malleability, risk and protective factors (38,39), links with research on conscience development and temperament (40), and social cognition (41-44).

## Psychopathy and Callous-Unemotional Traits

The  relationship  between  CU  traits  and  psychopathy is not surprising, considering that the concept of CU traits historically emerged from research into the  latent  factor  structure  of  psychopathy  (45-47) and  the  downward  extension  of  this  construct  to include  children  and  adolescents  in  an  effort  to investigate the developmental origins of adult psychopathy  (27,48).  Although  the  number  and content of latent dimensions underlying the construct  of  psychopathy  are  still  debated  (17,49), CU traits have consistently emerged as an underlying factor across studies, samples, and measures  and  as  distinct  from  other  factors  (e.g., impulsivity, antisocial behavior, narcissism) of psychopathy (16,47,48,50-52). Indeed, in latent variable analyses of the  Psychopathy Checklist: Youth Version (PCL:YV) (53) and the Psychopathy Checklist-Revised (PCL-R) (54), the affective factor, which specifically measures CU  traits, has, on average, the strongest set of factor loadings, thereby highlighting  the  prominence  of  these  traits  in  the overall conceptualization of psychopathy (46).

## Callous-Unemotional  Traits  in  the  Diagnostic and  Statistical  Manual  of  Mental  Disorders, Fifth Edition

Given the strong evidence in support of the clinical importance of CU traits, this construct has recently been included in the current edition of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) (55) as a specifier to allow for subtyping of the  conduct  disorder  diagnosis  on the  basis of the presence of CU traits. Specifically, individuals who meet  the full diagnostic criteria for a  conduct disorder diagnosis and who also meet two or more of four characteristics of CU traits can be designated with the specifier 'with limited prosocial emotions.'  The  four  CU  characteristics  that  are evaluated are as follows: 1) lack of remorse or guilt; 2)  callous  lack  of  empathy;  3)  unconcerned  about performance in important activities; and 4) shallow or deficient affect. With the inclusion of CU traits within  the official diagnostic system,  it  can  be expected that there will be a rise in the assessment of  CU traits  in  both  research  and  applied  settings. Hence, the development and psychometric evaluation  of  assessment  instruments  of  CU  traits becomes all the more important.

## Assessment of Callous-Unemotional Traits

With the inclusion of CU traits in the DSM-5 and given  the  evidence  regarding  the  salience  of  CU traits  for  indexing  psychopathy  and  understanding delinquent  youth,  there  is a need  for  efficient, comprehensive, reliable, and valid measures of these traits  that  are  suitable  for  use  with  both  offender and community  samples  of  youth. Although  a number of measures for the assessment of psychopathy in children and adolescents are available  (51,56,57),  with respect  to  the  assessment of CU traits, most of these measures include only a limited  number  of  items,  that  specifically  assess these  traits,  and  have  limited  response  options. Perhaps, this contributes to some of the psychometric shortcomings of some of these scales, such  as  relatively  modest  internal  consistency  (58) and restricted range of measurement (50). Furthermore, some of these measures are primarily suitable for use in offender samples; some are quite time-consuming  and  require  specialist  training  to obtain  reliable  ratings  (57).  To  overcome  these challenges, the 24-item self-report  Inventory  of Callous-Unemotional Traits (ICU) (59) was developed  to  specifically  assess  CU  traits  in  youth across offender, clinical, and community samples.

Studies of the factor structure of the ICU generally  suggest  that  a  bifactor  structure  fits  the data best, with a general CU factor (the total scale) accounting  for  covariance  among  all  items,  and three subfactors (uncaring, callousness, and unemotional) capturing unique patterns of covariance  among  subsets  of  the  items  (50,60-62). However, a recent study by Feilhauer and colleagues (63)  failed  to  replicate  this  factor  structure.  Alpha coefficients for the ICU scales in past research have generally ranged from .77 to .89, thereby indicating acceptable  reliability.  In  addition,  the  studies  have provided evidence in support of the ICU's construct validity by demonstrating associations with delinquency, aggression, reduced empathy, various personality dimensions, and psychophysiological measures of emotional reactivity. These  studies  have  also  demonstrated  differential associations between the ICU's three subscales and important external criteria, thereby elucidating how the different dimensions of CU traits are related to various aspects of personality functioning, psychopathology, and aggression (50,60-67). Overall, the ICU seems to have overcome some of the psychometric limitations of previous scales.

However,  only  a  few  studies  have  examined  the criterion-related  validity  of  the  ICU  as  compared with established rater-based assessment instruments of psychopathy, which rely on semi-structured interviews in combination with collateral information  (e.g.,  from  parents,  staff,  and  files). Although  semi-structured  interviews  can  be  timeconsuming and costly and may require the specialized training of interviewers, for the assessment  of psychopathy,  they are potentially important; they can be presumed to be less susceptible to malingering and impression management as compared with self-report questionnaires.  That  said,  other  researchers  have argued  in  favor  of  self-report  instruments  for  the assessment  of  psychopathic  traits,  considering  that these  are  subjective  traits  and  processes  to  which the individual might have better access. Yet, skepticism about the feasibility of self-report measures  to  assess  psychopathic  traits-especially among offender populations-is perhaps warranted and to some extent supported by research findings regarding their criterion-related validity. Correlations of self-report measures with interviewbased measures such as the PCL:YV and the PCLR, often lie within low to moderate range, and they have  a  tendency  toward  correlating  more  highly with the behavioral (impulsive and antisocial) features of psychopathy than with the interpersonal and affective (i.e., CU) features (51,57,68). Although it  is  still  unclear whether such findings suggest that one method is more valid than the other or whether this  is  primarily  the  result  of  method  variance  or other unestablished variables, these results do highlight the need for further studies of the criterion-related  validity  of  the  ICU  as  compared with established rater-based assessments of psychopathy.

Within  both  applied  and  research  settings,  the PCL:YV (53) has become one of the most commonly  used  measure  of  psychopathic  traits among delinquent adolescents (69,70). This instrument  combines  a  semi-structured  interview with the integration of collateral information (from files and other relevant sources) to allow the administrator  to  rate  the  presence  of  psychopathic traits.  From  a  theoretical  perspective,  one  should expect  the  ICU  to  show  good  convergent  and discriminative  validity  when  using  the  PCL:YV  as reference  standard.  However,  to  the  best  of  our knowledge, currently only two studies have examined the validity of the ICU  against the PCL:YV.  The  study  by  Fink  and  colleagues  (70) investigated  the  validity  associations  of  the  ICU with the  PCL:YV  in  a  sample  of incarcerated adolescent  American boys and girls and found the scales to be only somewhat weakly correlated and to have  no  significant  discriminative  validity  in  terms of differentiating between high and low psychopathy  groups  as  identified  by  the  PCL:YV. The study by Feilhauer and colleagues (63) examined the relationship between the two instruments in a sample comprised of Dutch detained  adolescents.  In  this  study,  the  researchers reported very weak and non-significant associations between the ICU and the PCL:YV total scale.

## The Current Study

The  current  study  was  designed  to  examine  the psychometric  properties  of  the  Danish  ICU  in  a sample of incarcerated adolescent boys. To this end, the study had several specific aims. First, the reliability  of  the  ICU  was  investigated  in  terms  of internal consistency indices and test-retest reliability.

Second, because of the discrepancies in the results demonstrating  weak  to  non-significant  associations between the ICU and PCL:YV, the criterion-related validity  of  the  ICU  remains  in  question,  especially for use with offender populations, where the labeling  of  young  offenders  as  psychopathic  could have  negative  consequences  (71,72).  Hence,  we sought to further investigate the convergent validity of the ICU with the PCL:YV by examining correlations between the two instruments. We also examined the robustness of the potential relationship  between  the  ICU  and  PCL:YV  after controlling for other potential predictors of psychopathy,  which  have  been  described  in  the literature (53,62,66,73-75). In addition, we aimed to assess  the  discriminative  validity  of  the  ICU  for identifying  high  versus  low  psychopathy  groups  as determined by the PCL:YV.  On  the basis of theoretical considerations and previous research, we expected  the  ICU  to  show  moderate  convergent and discriminative validity for psychopathy in general and for the affective dimension in particular when using the PCL:YV as a reference standard.

Third,  to  assess  construct  validity,  we  examined associations between the ICU, self-reported measures  of  aggression  and  empathy,  and  expert ratings of psychosocial impairment. On the basis of previous  research,  we  expected  the  ICU  to  be positively associated with aggression and psychosocial impairment and negatively with empathy.

Finally, because prior studies have had a tendency to confirm the three-factor structure of the ICU, we also  examine  and  report  the  associations  of  these factors with the PCL:YV  and  other construct validity  measures  to  identify  potential  differential associations.

## Method

## Participants

Participants were recruited consecutively from three secure institutions and a prison section for juvenile offenders in Denmark. Participants were considered eligible for the study if they were male, between 15 and 18 years old, remanded or sentenced, sufficiently fluent in Danish, and willing and able to give  informed  consent.  Exclusion  criteria  included profound mental retardation, alcohol and substance intoxication  or  withdrawal  symptoms  on  days  of assessment,  or  productively  psychotic  on  days  of assessment.  Staff  approached  eligible  participants during times when the first author was visiting the sites. All participants were given verbal and written information  regarding  study  aims  and  procedures, and informed consent was obtained in writing.

From August 2010 to November 2011, 127 young people were assessed for eligibility: 15 did not fulfill inclusion  criteria,  5  met  exclusion  criteria,  and  27 refused to participate. The final sample was comprised of 80 adolescent boys, as detailed elsewhere  (76).  The  mean  age  of  the  sample  was 16.5 years (SD = 0.8). The majority of the participants were remanded ( n = 67; 84%), and the most common offenses were robbery ( n = 49; 61%) and  assault  ( n =  18;  23%).  Approximately  half  of the participants ( n = 39; 49%) were descendants of immigrants or immigrants themselves, primarily from the Middle East, Northern Africa, and Europe. Thirty-six (45%) did not have any contact with  the  education  system  before  their  placement, and 51 (64%) came from single-parent households. According to the results of a structured diagnostic interview,  the  most  common  psychiatric  diagnoses were  conduct  disorder  ( n =  61;  76%),  alcohol  and substance  abuse  ( n =  46;  58%),  attention  deficit/ hyperactivity disorder ( n = 18; 23%), anxiety disorders ( n = 14; 18%), and mood disorders ( n = 6; 8%).

## Assessment Materials

Inventory of Callous-Unemotional Traits. The ICU (59) is a  24-item  self-report  questionnaire  developed  to assess  CU  traits.  Each  item  is  rated  on  a  4-point Likert scale ranging from 0 ('Not at all true') to 3 ('Definitely  true').  Twelve  items  require  reverse scoring before the calculation of scale scores. Items can be summed to yield a total score. On the basis of  factor  analytic  studies  (50,62),  three  factors  or subscales have generally emerged: uncaring (e.g., the reversed-scored item 'I always try  my best'), callousness  (e.g.,  'I  do  not  care  who  I  hurt  to  get what  I  want'),  and  unemotional  (e.g.  'I  hide  my feelings from others'), which consists of 8, 11, and 5  items,  respectively.  The  ICU  is  also  available  in parent- and teacher-rated formats, but in this study only the self-report version was used.

Psychopathy Checklist:  Youth  Version. The  PCL:YV (53,77)  is  a  20-item  clinical  construct  rating  scale designed  to assess psychopathic  traits in  youth between the ages of 12 and 18 years. The PCL:YV was adapted from the PCL-R (54). On the basis of a semi-structured interview and file reviews, each item is rated on a 3-point scale as either 0 (the item does not apply), 1 (the item applies to some extent), or 2 (the  item  applies  to  the  youth).  Scores  on  the  20 items can be summed to yield a dimensional score that ranges from 0 to 40 and measures the number and  severity  of  psychopathic  features  present.  The PCL:YV manual does not recommend any particular  cut  score  for  a  categorical  diagnosis  of psychopathy,  but  previous  research  has  used  cut scores  that  have  ranged  from  20  to  30.  In  this study-consistent with other studies within the field (78,79)-we used a cut score of 25 on the PCL:YV for  dividing  the  sample  into  two  groups  of  highscoring versus low-scoring participants.

The underlying factor structure of the PCL:YV is still under investigation, with studies finding support  for  various  three-  and  four-factor  models (47,80-82), thereby suggesting that the construct of psychopathy  is  essentially  multidimensional.  Given the unresolved nature of the underlying factor structure of the PCL:YV, for this study we chose to follow  the  PCL:YV  manual,  which  uses  the  fourfactor model. Regardless of the debate regarding the threeor  four-factor  structure  of  the  PCL:YV, because the four-factor model is used in the official PCL:YV manual, we thought it would enhance the ecologic validity of the study, because it is presumably the scales recommended in the manual that most clinicians will use in routine practice. The four-factor  model  is  based  on  18  of  the  PCL:YV

items (53), and Factors 1, 2, and 3 are identical to the three factors of the modified Cooke and Michie model (45). Factor 1 consists of four items (impression  management,  grandiose  sense  of  selfworth, pathological lying, and  manipulation for personal gain) and measures the interpersonal features associated with psychopathy. Factor 2 also consists  of  four  items  (lack  of  remorse,  shallow affect, callous/lack of empathy, and failure to accept responsibility), and it measures the affective impairments and deficits associated with psychopathy. It is generally presumed  that the affective factor of psychopathy in particular corresponds with the construct CU traits. Factor 3 measures  the  behavioral  features  of  psychopathy and  consists  of five items  (stimulation seeking, parasitic  orientation,  lacks  goals,  impulsivity,  and irresponsibility).  Factor  4  captures  the  antisocial aspects  of  psychopathy  and  consists  of  five  items (poor anger controls, early behavior problems, serious criminal behavior, serious violations of conditional release, and criminal versatility).

Research suggests that the PCL:YV has acceptable psychometric  properties  (53,83,84).  In  this  study, inter-rater agreement in a subset of the sample ( n = 20) was excellent (intra-class correlation coefficients (ICCs) for PCL:YV scales was: total = .91; Factor 1 =  .80;  Factor  2  =  .79;  Factor  3  =  .77;  Factor  4 = .82). The PCL:YV total scale scores ranged from 3  to  35,  with  a  mean  of  20.58  (SD  =  8.16).  Mean scores for Factors 1,  2,  3,  and  4  were  3.73  (SD  = 2.36), 4.49 (SD = 2.46), 5.64 (SD = 2.30), and 5.29 (SD  =  2.46),  respectively.  A  total  of  27  (34%) participants received a PCL:YV total score of 25 or higher.

Interpersonal Reactivity Index. The Interpersonal Reactivity  Index  (85,86)  is  a  28-item  self-report questionnaire  comprised  of  four  discrete  7-item subscales,  each  of  which  assesses  a  specific  aspect of the global construct of empathy. Items are scored on a 5-point Likert scale that ranges from 0 ('Does not  describe  me  very  well')  to  4  ('Describes  me very  well').  Scores  on  the  four  scales  can  range from 0 to  28,  with  higher  scores  indicating  higher empathy. The perspective-taking scale taps the respondent's ability or proclivity to adopt the psychological  point  of  view  of  others;  the  fantasy scale assesses the respondent's tendency to transpose himor herself imaginatively into fictitious characters' inner lives in books and movies. The empathic concern scale taps feelings of sympathy and concerns for unfortunate others, and the  personal  distress  scale  measures  respondents' feelings of anxiety and unease during tense interpersonal situations. Mean scores obtained during the current study for the perspective-taking, fantasy,  empathic  concern,  and  personal  distress scales  were  12.24  (SD  =  4.77),  13.54  (SD  =  5.96), 13.59 (SD = 6.97), and 9.13 (SD = 5.42), respectively. The internal consistency were found to be adequate (coefficient alpha =  .80, .85, .93, and .84 for the perspective-taking, fantasy, empathic concern, and personal distress scales, respectively).

Reactive-Proactive Aggression Questionnaire . The Reactive-Proactive  Aggression  Questionnaire  (RPQ) (87)  is  a  23-item  self-report  questionnaire  for  the assessment  of  reactive  and  proactive  aggression tendencies  in  children  and  adolescents.  Items  are rated  on  a  3-point  scale  from  0  ('Never')  to  2 ('Often') and summed to yield scores for a reactive scale (11 items) and a proactive scale (12 items) as well as for a total scale score based on the summing of  all  items.  Higher  scores  reflect  higher  levels  of aggression. Mean scores for the reactive, proactive, and total scales were 11.16 (SD = 6.01), 8.19 (SD = 4.51), and 19.35 (SD = 9.49), respectively. Internal consistency  values  for  the  reactive,  proactive,  and total scales were acceptable (coefficient alphas = .93, .85, and .93, respectively).

Health  of  the  Nation  Outcome  Scales  for  Children  and Adolescents. Health  of  the  Nation  Outcome  Scales for Children and Adolescents (HoNOSCA) (88,89) is a rating scale that measures emotional and behavioral  problems.  HoNOSCA  is  comprised  of 15 items. The first 13 items are used to compute the A section total score that indicates the overall level of  psychosocial  impairments;  the  items  measure problems related to disruptive/aggressive/antisocial behaviors, overactivity/concentration, self-injury, substance  misuse,  scholastic  skills,  physical  illness, hallucinations/delusions, nonorganic somatic symptoms, emotional symptoms, peer relationships, self-care  and  autonomy,  family  relationships,  and school  attendance.  These  13  items  can  then  be further grouped into four subscales: A) behavior; B) impairment; C) symptoms; and D) social problems. The last two items, which constitute the B section, rate parental understanding of the children's problems and information regarding available services.  These  last  two  items  were  omitted  in  the present  study,  so  only  the  13  items  from  the  A section were used in this study.

Items  are  rated  from  0  ('No  problems')  to  4 ('Severe problems'). HoNOSCA has been found to have  acceptable  reliability  and  validity  (90).  In  the current  study,  the  total  scale  scores  ranged  from  3 to  33,  with  a  mean  of  19.35  (SD  =  7.77).  For subscales A, B, C, and D, the mean scores were 7.89 (SD  =  2.88),  2.33  (SD  =  1.66),  1.51  (SD  =  1.64), and 7.63 (SD  =  3.65), respectively. Inter-rater agreement  in  a  subset  of  the  sample  ( n =  20)  was excellent for the total scale (ICC = .91) and good to excellent  for the subscales and items (ICCs ranged from  .71  to  .88).  The  internal  consistency  for  the total  scale  was  also  satisfactory  (coefficient  alpha = .80).

Schedule for Affective Disorders and  Schizophrenia for School-Age  Children-Present  and  Lifetime  Version. The Schedule for Affective Disorders and Schizophrenia for School-Age Children, Present and Lifetime Version  (K-SADS-PL)  (91),  is  a  semi-structured diagnostic  interview  for  the  assessment  of  current and past psychopathology in children and adolescents  between  the  ages  of  six  and  18  years according  to  DSM-IV  criteria.  This  measure  was used to describe the psychiatric characteristics in the sample.  In  this  study,  inter-rater  agreement  in  a subset  of  the  sample  ( n =  20)  was  excellent,  with kappa and ICC values for categorical agreement on specific  diagnoses  and  dimensional  agreement  on the number of emotional and alcohol and substance use disorders ranging from .77 to .86.

Wechsler  Intelligence  Scale,  vocabulary  subtest .  We  used the vocabulary subtest of the Wechsler Intelligence Scale  for  Children,  Third  Edition  (WISC-III)  (92), and  the  Wechsler  Adult  Intelligence  Scale,  Third Edition (WAIS-III) (93), to estimate verbal intelligence.  Younger  participants  (those  16  years old or younger) were assessed with the WISC, and older  participants  (those  17  years  old  and  older) were  assessed  with  the  WAIS.  The  vocabulary subtest is a test of accumulated verbal learning that generally reflects the nature and level of an individual's  schooling  and  learning  environments. The  vocabulary  subtest  is  the  most  reliable  of  the verbal  subtests  and  the  single  best  indicator  of general intelligence (94). Raw scores were converted to scaled scores with a mean of 10 and a standard deviation of 3. In this sample, scaled scores ranged from  6  to  11,  with  a  mean  of  8.51  (SD  =  1.14). Inter-rater agreement in a subset of the sample ( n = 20) was excellent (ICC = .82).

## Translation of the Inventory of CallousUnemotional Traits

The English version of the ICU was translated and adapted  into  Danish  in  accordance  with  published guidelines  for  the  translation  of  instruments  for cross-cultural research  (95).  First,  the  ICU  was translated independently into Danish by two psychologists,  who  then  met  and  agreed  upon  an initial  version.  Next,  a  third  psychologist  backtranslated  the  instrument  into  English,  at  which point  all  of  the  translators  met  to  make  decisions about the final version.

## Ethics

The  study  was  approved  by  the  Research  Ethics Committee  for  Region  Zealand  acting  under  the Danish Act on a Biomedical Research Ethics Committee System and the Processing of Biomedical  Research  Projects  as  well  as  by  the Danish Data Protection Agency. Because the participants  were  minors,  it  would  generally  be required that informed consent be obtained from a parent  or  guardian.  However,  the  Research  Ethics Committee for Region Zealand gave special permission for the young people participating in this study to give informed consent without the researcher  also  asking  for  parental  consent.  This procedure  was  chosen  to  minimize  the  rejection rate. All participants chose to give informed consent in writing, without parental involvement. Participants were not offered any remuneration for their participation.

## Procedure

All assessments were performed at the secure sites in quiet areas.  The first author conducted all assessments. Before the assessments were undertaken,  participants  were  informed  about  the study aims  and  procedures  and  told  that  their assessment results would be treated with confidentiality  and  would not be shared with staff, relatives, or anyone else unless the participants gave special permission for this. Participants were provided with clear instructions for completing selfreport  inventories  and  told  that,  apart  from  the WISC/WAIS  test,  there were no preferred or 'correct' answers to any of the questions but that they should try to respond as honestly as possible. To minimize test fatigue, the participants were also told to ask for breaks whenever they felt the need. Finally, all participants were explicitly instructed not to share or discuss their responses on the self-report questionnaires with the researcher. They were instructed to put their responses in a sealed envelope  when  they  finished  so  that  the  PCL:YV administration  and  ratings  could  be  done  blind  to ICU  results. We  deliberately decided that  ICU assessments would be conducted first and that the PCL:YV  interview would  occur last. All other assessments  were  performed  in  between.  Within this scheme, the order of presentation was randomized  with  the  use  of  www.randomizer.org (96) to counteract  potential order effects.  This scheme was chosen to ensure that the respondents were not fatigued by the comprehensive assessment battery  when  filling  out  the  self-report  inventory. Moreover, we were keen to maximize the time gap between the administration of the ICU and PCL:YV to minimize the risk of priming effects.

If  participants  had  reading  difficulties  ( n =  37), the  researcher  read  the  self-report  items  out  loud while the participants marked their responses on a separate copy of the questionnaires, out of sight of the  researcher.  This  procedure  was  in  accord  with previous  research  practices and  served  to  maintain standardized administration procedures.

The PCL:YV, WISC/WAIS, HoNOSCA, and KSADS-PL  assessments  were  audio  recorded  for purposes of later estimation of inter-rater agreement. After approximately nine days (M = 9; SD = 1.1; range, 7 to 12), ICU follow-up assessments  were  conducted  to  assess  test-retest reliability.  Retest  assessments  were  only  conducted with  half  of  sample  ( n =  40).  To  counteract  the effects  of  recall  bias,  participants  were  explicitly instructed  not  to  try  to  remember  their  previous responses  but  rather  to  respond  as  they  felt  was most appropriate at present.

When data collection was finished, an experienced clinical psychologist (the second author) read through  file  information  and  listened  to  randomly selected  recordings  of  the  PCL:YV,  K-SADS,  and WISC-III/WAIS-III ( n = 20) assessments and recoded them, blind to the original ratings done by the primary  investigator, to compute  inter-rater agreement.  The  same  psychologist  also  completed HoNOSCA  ratings on the basis of files and interviews.IBM  Statistical  Package  for  the  Social Sciences (SPSS) software for Mac, version 20.0 (97), was used to randomly select the cases that were to be re-rated.

Before data collection began, the two psychologists  who  conducted  the  PCL:YV  ratings were trained by the first author of this instrument, A. E. Forth, and checked for reliability. Both senior authors of this article were available throughout the data collection process to supervise clinical ratings.

## Data Analytic Strategy

The  Kolmogorov-Smirnov  test  was  used  to  test whether the distribution  of  scores  was  normal. To assess  the  internal  consistency  of  the  ICU,  we calculated Cronbach's alpha, mean inter-item correlations, and item-total correlations. In accordance with conventional standards, we considered alpha coefficients of more than .70 (98) and  mean  inter-item  correlations  within  the  range of  .15  to  .50  (99)  to  be  acceptable.  Test-retest reliability  was  assessed  with  the use of ICCs. ICCs were  also  used  to  assess  inter-rater  agreement  on dimensional  ratings  using  absolute  agreement  for single  measures.  ICC  values  were  characterized  as follows: poor agreement: < .40; fair to good agreement:  .40  to  .75;  and  excellent  agreement: > .75 (100).

Bivariate correlation analyses, namely the Pearson product-moment  correlation,  were  used  to  assess criterion and construct validity for continuous scores.  Correlations  were  interpreted  as  follows: r < .30 = low; r from .30 to .50 = moderate; and r s > .50 = large (101).

To  examine  the  independent  and  incremental effects of the ICU  for predicting variance in PCL:YV  scores  over  and  above  demographic  and clinical  predictor  variables,  a  series  of  hierarchical linear regressions were conducted. PCL:YV continuous  scale  scores  were  used  as  outcome variables. In Step 1, age, Danish/non-Danish ethnicity, verbal intelligence scores, number  of alcohol  and  substance  use  disorders,  number  of emotional disorders (anxiety plus affective disorders), number of positive attentiondeficit/hyperactivity  disorder  criteria,  and  number of  positive  conduct  disorder  criteria  were  entered. In Step 2, the ICU score was entered. Multicollinearity  was  not  considered  a  problem  in these analyses if the variance inflation factor (VIF) was less than 10 (102) and the tolerance statistic was more than 0.1 (103).

Receiver  operating  characteristic  (ROC)  analysis was used to assess the discriminative validity of the ICU for detecting psychopathy. A cut score of 25 or more on the PCL:YV was used for these analyses. ROC curves  were  obtained  for  ICU  total  and  the three subscales by plotting pairs of sensitivity (truepositive rate) against 1-specificity (false-positive rate) for all possible cut scores. The area under the ROC  curve  (AUC)  is  an  index  of  the  measure's overall diagnostic efficiency or discriminative ability. The AUC can range from 0 to 1, and .50 indicates chance-level  accuracy.  We  interpret  AUC  values <.70 as low accuracy; from .70 to .90 as moderate accuracy;  and  >.90  as  high  accuracy  (104).  In  this study, the AUC can be interpreted as the probability that the ICU will yield a higher score for a randomly selected adolescent with a score of 25 or more on the PCL:YV as compared with a randomly chosen adolescent  with  a  score  of  less  than  25  on  the PCL:YV.

Although we report all validity correlations for the interest  of  the  reader,  due  to  the  large  number  of statistical tests performed, in common with previous research within the field  (105),  a  minimal statistical  significance  level  of  .01  (two-tailed)  was required  for  results  to  be  considered  significant  in this study.

Data  were  analyzed  with  the  use  of  IBM  SPSS software  as  described  previously,  except  for  the ROC analyses, which were performed with MedCalc for Windows, version 12.0.

## Results

## Descriptive Statistics and Distribution of Inventory of Callous-Unemotional Traits Scores

Table 1 displays descriptive statistics and the distribution of ICU scale scores in the total sample. The  mean  of  the  ICU  total  scale  score  was  33.88 (SD  =  11.61),  and  the  median  score  was  31.50. Visual inspection of histogram plots and the Kolmogorov-Smirnov  test  indicated  that  the  ICU total, callousness, and unemotional scales were nonnormally distributed.

## Reliability: Internal  Consistency,  Test-Retest Reliability, and Inter-Scale Correlations

Information about the internal consistency and testretest reliability of the ICU is provided in Table 2. Cronbach's  alpha  and  mean  inter-item  correlations were all acceptable as judged by conventional standards (99,106), and they were comparable with those previously published (50,60-62,70,107).

Inspection  of  the  item-total  correlations  did  not suggest that the removal of any items could improve  the  ICU  scales'  internal  consistency  as measured by Cronbach's alpha, except for item 10 ('I  do  not  let  my  feelings  control  me').  Deleting this  item  would  raise  the  alpha  for  the  ICU  total from  .89  to  .90  and  for  the  callousness  subscale from .78 to .81. Considering that the potential raise in  alpha  by  deleting  item  10  from  two of  the  ICU scales would only be marginally higher, we decided to retain all items for further analyses.

Test-retest reliability of the ICU  scales in a subsample of participants ( n = 40) after a period of 9 days was excellent. ICCs ranged from .82 to .88.

TABLE 1. Descriptive statistics and distribution of Inventory of Callous-Unemotional Traits scale scores

* p < .05 (two-tailed)

| Inventory of Callous- Unemotional Traits   | Descriptives   | Descriptives   | Descriptives   | Distribution   | Distribution   | Kolmogorov-Smirnov Test   | Kolmogorov-Smirnov Test   |
|--------------------------------------------|----------------|----------------|----------------|----------------|----------------|---------------------------|---------------------------|
| Scale                                      | Mean           | SD             | Observed Range | Skew           | Kurtosis       | D                         | df                        |
| Total                                      | 33.88          | 11.61          | 12 to 60       | .24            | -.82           | .10 *                     | 80                        |
| Uncaring                                   | 15.08          | 4.41           | 4 to 24        | -.18           | -.48           | .07                       | 80                        |
| Callousness                                | 11.65          | 5.65           | 2 to 27        | .67            | -.08           | .13 **                    | 80                        |
| Unemotional                                | 7.15           | 3.20           | 2 to 15        | -.01           | -.77           | .12 **                    | 80                        |

** p < .01 (two-tailed)

TABLE 2 . Internal consistency and test-retest reliability of the Inventory of CallousUnemotional Traits

| Inventory of Callous- Unemotional Traits Scale   | Internal Consistency ( N = 80)   | Internal Consistency ( N = 80)   | 9-Day Test-Retest Reliability ( n = 40)   |
|--------------------------------------------------|----------------------------------|----------------------------------|-------------------------------------------|
|                                                  | Coefficient Alpha                | Mean Inter-Item Correlations     | Intra-Class Correlation Coefficient ***   |
| Total                                            | .89                              | .26                              | .88                                       |
| Uncaring                                         | .78                              | .32                              | .82 ***                                   |
| Callousness                                      | .78                              | .24                              | .86 ***                                   |
| Unemotional                                      | .78                              | .41                              | .82 ***                                   |

*** p < .001 (two-tailed)

As shown in Table 3, all three ICU subscales were highly  correlated  with  the  total  scale  ( rs ranged from  .80  to  .92).  Inter-subscale  correlations  were also large ( rs ranged from .61 to .72), although they were  somewhat  lower  than  those  obtained  for  the subscale-total correlations.

TABLE 3. Inventory of Callous-Unemotional Traits inter-scale correlations

|             | Pearson Correlation Coefficients   | Pearson Correlation Coefficients   | Pearson Correlation Coefficients   |
|-------------|------------------------------------|------------------------------------|------------------------------------|
|             | Total                              | Uncaring                           | Callousness                        |
| Uncaring    | .88 ***                            |                                    |                                    |
| Callousness | .92 ***                            | .72 ***                            |                                    |
| Unemotional | .80 ***                            | .61 ***                            | .62 ***                            |

p < .001 (two-tailed)

***

## Criterion  Validity  of  the  Inventory  of  CallousUnemotional Traits with the Psychopathy Checklist: Youth Version

Concurrent  associations  for  continuous  scores  between  the Inventory of Callous-Unemotional Traits and the Psychopathy Checklist: Youth Version. Bivariate correlations  between  the  ICU  and  PCL:YV  are presented in Table 4. All correlations were positive and  statistically  significant,  and  they  ranged  from moderate to large. As expected, the highest correlations  was  obtained  for  the  ICU  total  and subscales  with  the  PCL:YV  total  and  the  affective factor (Factor 2).

Independent  effects  of  the  Inventory  of  Callous-Unemotional Traits for predicting Psychopathy Checklist: Youth Version scores. To  examine  whether  the  ICU  total was associated with psychopathy and its subfactors above  and  beyond  other  demographic  and  clinical characteristics,  a  series  of  block-wise  hierarchical regression analyses were conducted, with the covariates entered in Step 1 and the ICU total added in  Step  2.  Table  5  reports  the  standardized  beta coefficients,  adjusted R 2 ,   and R 2 changes  for  these analyses. VIF ranged from 1.05 to 2.30 and tolerance ranged from 0.44 to 0.95, thereby indicating  that  multicollinearity  was  not  a  problem in these analyses.

TABLE 4. Bivariate correlations between the Inventory of Callous-Unemotional Traits and the Psychopathy Checklist: Youth Version

| Inventory of Callous-   | Psychopathy Checklist: Youth Version   | Psychopathy Checklist: Youth Version   | Psychopathy Checklist: Youth Version   | Psychopathy Checklist: Youth Version   | Psychopathy Checklist: Youth Version   |
|-------------------------|----------------------------------------|----------------------------------------|----------------------------------------|----------------------------------------|----------------------------------------|
| Unemotional Traits      | Total                                  | Factor 1: Interpersonal ***            | Factor 2: Affective ***                | Factor 3: Behavioral ***               | Factor 4: Antisocial ***               |
| Total                   | .76 ***                                | .41                                    | .77                                    | .61                                    | .52                                    |
| Uncaring                | .71 ***                                | .31 **                                 | .63 ***                                | .65 ***                                | .54 ***                                |
| Callousness             | .67 ***                                | .41 ***                                | .69 ***                                | .51 ***                                | .40 ***                                |
| Unemotional             | .61 ***                                | .34 **                                 | .70 ***                                | .41 ***                                | .42 ***                                |

** p < .01 (two-tailed)

*** p < .001 (two-tailed)

TABLE 5. Hierarchical multiple regression analyses for variables predicting Psychopathy Checklist: Youth Version total and factor scores

|                              | Psychopathy Checklist: Youth Version Scales   | Psychopathy Checklist: Youth Version Scales   | Psychopathy Checklist: Youth Version Scales   | Psychopathy Checklist: Youth Version Scales   | Psychopathy Checklist: Youth Version Scales   |
|------------------------------|-----------------------------------------------|-----------------------------------------------|-----------------------------------------------|-----------------------------------------------|-----------------------------------------------|
|                              | Total ß                                       | Factor 1: Interpersonal ß                     | Factor 2: Affective ß                         | Factor 3: Behavioral ß                        | Factor 4: Antisocial ß                        |
| Step 1                       |                                               |                                               |                                               |                                               |                                               |
| Age                          | -.07                                          | -.08                                          | -.18                                          | -.03                                          | .06                                           |
| Danish ethnicity             | .13                                           | .27 *                                         | .25 *                                         | .05                                           | -.11                                          |
| Verbal intelligence quotient | .14                                           | .33 **                                        | .24 *                                         | -.02                                          | -.04                                          |
| Substance use                | .04                                           | -.17                                          | .04                                           | .22 *                                         | .06                                           |
| Emotional disorder           | .00                                           | -.08                                          | .00                                           | .03                                           | .13 *                                         |
| Attention-deficit/           | .04                                           | -.06                                          | -.06                                          | .16                                           | .05                                           |
| hyperactivity disorder       |                                               |                                               |                                               |                                               |                                               |
| Conduct disorder             | .87 ***                                       | .59 ***                                       | .72 ***                                       | .61 ***                                       | .74 ***                                       |
| Adjusted R 2                 | .69                                           | .29                                           | .41                                           | .56                                           | .72                                           |
| ∆ R 2                        | .72 ***                                       | .35 ***                                       | .46 ***                                       | .60 ***                                       | .75 ***                                       |
| F(72,79)                     | 26.54 ***                                     | 5.53 ***                                      | 8.82 ***                                      | 15.45 ***                                     | 30.56 ***                                     |
| Step 2                       |                                               |                                               |                                               |                                               |                                               |
| Age                          | -.00                                          | -.05                                          | -.08                                          | .01                                           | .06                                           |
| Danish ethnicity             | .01                                           | .22                                           | .06                                           | -.04                                          | -.12                                          |
| Verbal intelligence quotient | .10                                           | .32 **                                        | .18 *                                         | -.04                                          | -.04                                          |
| Substance use                | .01                                           | -.18                                          | -.00                                          | .20 *                                         | .06                                           |
| Emotional disorder           | .03                                           | -.07                                          | .04                                           | .05                                           | .14 *                                         |
| Attention-deficit/           | .00                                           | -.08                                          | -.11                                          | .13                                           | .04                                           |
| hyperactivity disorder       |                                               |                                               |                                               |                                               |                                               |
| Conduct disorder             | .60 ***                                       | .47 **                                        | .29 **                                        | .41 ***                                       | .71 ***                                       |
| Inventory of Callous-        | .38 ***                                       | .17                                           | .61 ***                                       | .29 **                                        | .05                                           |
| Unemotional Traits total 2   |                                               |                                               |                                               |                                               |                                               |
| Adjusted R                   | .77                                           | .29                                           | .61                                           | .60                                           | 72                                            |
| ∆ R 2                        | .07 ***                                       | .02                                           | .19 ***                                       | .04 **                                        | .00                                           |
| F(71,79)                     | 33.86 ***                                     | 5.09 ***                                      | 16.33 ***                                     | 15.81 ***                                     | 26.51 ***                                     |

The ICU total provided a unique and significant contribution to the concurrent prediction of variance in the PCL:YV total scores, affective scale scores,  and  behavioral  scale  scores  but  not  to  the prediction of variance in the interpersonal  and antisocial  factor  scores.  Incremental R 2 values  for including  the  ICU  total  in  the  block  of  predictor variables for the PCL:YV  total, affective, and lifestyle factors were 7%, 19%, and 4%, respectively.

The largest significant increase in predicted variance was for the affective factor, which suggests that the ICU  total  was  a  specifically  robust  and  relatively strong  predictor  of  CU  traits,  as  measured  by  the PCL:YV,  over  and  above  the  other  demographic and  clinical  predictors.  The  presence  of  conduct disorder symptoms was the only covariate to remain a significant predictor for all of the PCL:YV scales when the ICU was entered in Step 2; this suggests Sensitivity (True-positive rate)

that, in this sample, the amount of conduct problems was significantly associated with all of the PCL:YV  scales.  Also  in  Step  2,  it  was  found  that verbal intelligence independently added to the prediction of the interpersonal factor scores on the PCL:YV.

Discriminative accuracy of the Inventory of CallousUnemotional Traits for high versus low psychopathy groups. To investigate the discriminative accuracy and validity  of  the  ICU  for  detecting  participants  with high psychopathy scores (PCL:YV total, ≥25), ROC analyses were conducted for each of the ICU scales. Figure 1 displays the ROC curve for the ICU total scale.

FIGURE 1. Receiver operating characteristic curve for the Inventory of CallousUnemotional Traits total scale demonstrating discriminative criterion validity for psychopathy on the Psychopathy Checklist: Youth Version

Note. This receiver operating characteristic curve for the Inventory of CallousUnemotional  Traits  total  scale  demonstrates  the  discriminative  criterion validity  for  psychopathy  on  the  Psychopathy  Checklist:  Youth  Version  (total ≥25).  This  curve  was  significantly  different  from  the  non-informative  45degree diagonal reference line ( p < .0001), with an area under the curve of .90 (SD = 0.04). A cut score of 38 yielded the optimal balance between sensitivity and specificity (.85 and .87 respectively).

<!-- image -->

The ROC curve for the ICU total was significantly  different  ( p <  .0001)  from  the  45degree non-informative diagonal reference line. The AUC for the ICU total was .90 (SE = 0.04; 95% CI =  .83  to  .96),  which  indicates  moderate  to  high discriminatory accuracy. Sensitivity was perfect (100%)  for  scores  of  less  than  approximately  20, and  specificity  was  perfect  (100%)  for  scores  of more than approximately 52. A score of 38 on the ICU  total  scale  correctly  classified  86%  of  the participants and yielded the highest values for both sensitivity  (.85;  95%  CI,  .66  to  .96)  and  specificity (.87; 95% CI, .75 to .95).

Significant  ROC  curves  ( p <  .0001)  were  also obtained  for  the  ICU's  uncaring,  callousness,  and unemotional subscales, with an AUC of .87 (SE = 0.04; 95% CI = .78 to .94), .89 (SE = 0.04; 95% CI =  .80  to  .95),  and  .80  (SE  =  0.05;  95%  CI  =.69 to  .88),  respectively.  Comparison  of  the  AUC  for each  of  the  three  ICU  subscales  with  the  AUC  of the  ICU  total  revealed  that  only  the  unemotional subscale was significantly different (z, 3.28; p < .001), which indicates a somewhat lower discriminatory accuracy of this subscale as compared  with  the  ICU  total  for  discriminating between  groups  with  high  and  low  psychopathy scores.

## Construct Validity of the Inventory of CallousUnemotional Traits

Results  of  the  associations  between  the  ICU  and indices  of  aggression,  empathy,  and  psychosocial functioning are listed in Table 6.

Reactive  and  proactive  aggression. As  expected,  all  ICU scales were  statistically  significant  and  positively correlated with self-reported reactive and proactive aggression  (see  Table  6).  The  magnitude  of  the obtained correlations ranged from .40 to .61, which indicates moderate to high associations between CU traits and self-reported aggressive tendencies. Of all of  the  ICU  scales,  the  total  scale  displayed  the highest  correlations  with  all  three  RPQ  scales  ( r s ranged from .53 to .61). In terms of reactive versus proactive aggression, the ICU total, callousness, and unemotional scales displayed their largest associations  with  the  proactive  scale.  In  terms  of ICU  subscales,  the  callousness  scale  showed  the largest correlations with the RPQ total and proactive scales ( r s = .57 and .58, respectively).

Empathy .  The  ICU  total  was  moderately  to  highly negatively correlated with all self-reported dimensions  of  empathy  ( r s  ranged  from  -.47  to  .82;  see  Table  6),  as  predicted.  For  all  ICU  scales, the largest negative correlations were obtained with the empathic concern scale ( r s ranged from -.68 to -.82); this indicates that a lack of feelings of sympathy and concern for unfortunate others seems to be an especially pronounced feature of individuals with CU traits as measured by the ICU.

Psychosocial functioning. The ICU total was moderately to  highly  correlated  with  psychosocial  impairments as  measured by the HoNOSCA total and the four subscales ( r s ranged from .33 to .80; see Table 6). At the level of specific HoNOSCA items, the ICU total was moderately to highly correlated with problems concerning disruptive and aggressive behavior, hallucinations and delusions, peer relationships, selfcare and independence, and poor school attendance.

TABLE 6. Bivariate correlations between the Inventory of Callous-Unemotional Traits and measures of aggression, empathy, and psychosocial functioning

| Scales                                       | Inventory of Callous-Unemotional Traits   | Inventory of Callous-Unemotional Traits   | Inventory of Callous-Unemotional Traits   | Inventory of Callous-Unemotional Traits   |
|----------------------------------------------|-------------------------------------------|-------------------------------------------|-------------------------------------------|-------------------------------------------|
|                                              | Total                                     | Uncaring                                  | Callousness                               | Unemotional                               |
| Reactive-Proactive Aggression Questionnaire  |                                           |                                           |                                           |                                           |
| Total                                        | .61 ***                                   | .53 ***                                   | .57 ***                                   | .48 ***                                   |
| Reactive                                     | .53 ***                                   | .50 ***                                   | .47 ***                                   | .40 ***                                   |
| Proactive                                    | .59 ***                                   | .45 ***                                   | .58 ***                                   | .48 ***                                   |
| Interpersonal Reactivity Index               |                                           |                                           |                                           |                                           |
| Perspective-taking                           | -.52 ***                                  | -.53 ***                                  | -.41 ***                                  | -.44 ***                                  |
| Fantasy                                      | -.50 ***                                  | -.45 ***                                  | -.38 **                                   | -.54 ***                                  |
| Empathic concern                             | -.82 ***                                  | -.70 ***                                  | -.74 ***                                  | -.68 ***                                  |
| Personal distress                            | -.47 ***                                  | -.33 **                                   | -.47 ***                                  | -.43 ***                                  |
| Health of the Nation Outcome Scales for      |                                           |                                           |                                           |                                           |
| Children and Adolescents                     |                                           |                                           |                                           |                                           |
| Total                                        | .46 ***                                   | .48 ***                                   | .37 **                                    | .35 **                                    |
| Item 1: Disruptive/aggressive                | .38 ***                                   | .35 **                                    | .30 **                                    | .38 **                                    |
| Item 2: Overactivity/attentional difficulty  | .22 *                                     | .31 **                                    | .14                                       | .13                                       |
| Item 3: Non-accidental self-injury           | .03                                       | .06                                       | .02                                       | -.01                                      |
| Item 4: Alcohol, substance/solvent misuse    | .19                                       | .25 *                                     | .12                                       | .11                                       |
| Item 5: Scholastic or language skills        | .26 *                                     | .26 *                                     | .22 *                                     | .19                                       |
| Item 6: Physical illness/disability problems | .18                                       | .21                                       | .18                                       | .06                                       |
| Item 7: Hallucinations and delusions         | .51 ***                                   | .43 ***                                   | .43 ***                                   | .48 ***                                   |
| Item 8: Nonorganic somatic symptoms          | -.01                                      | -.04                                      | .02                                       | -.01                                      |
| Item 9: Emotional symptoms                   | -.20                                      | -.13                                      | -.28 *                                    | -.07                                      |
| Item 10: Peer relationships                  | .49 ***                                   | .44 ***                                   | .42 ***                                   | .41 ***                                   |
| Item 11: Self-care and independence          | .35 **                                    | .31 **                                    | .31 **                                    | .27 *                                     |
| Item 12: Family life and relationships       | .27 *                                     | .35 **                                    | .18                                       | .18                                       |
| Item 13: Poor school attendance              | .46 ***                                   | .42 ***                                   | .44 ***                                   | .33 **                                    |

All ICU subscales were statistically significant and moderately to highly associated with the HoNOSCA total, impairment, symptoms, and social problems scales. However, only the ICU's uncaring subscale was statistically significantly ( p <  .01) associated with the behavior subscale of the HoNOSCA.  The  uncaring scale was the only subscale to be correlated with overactivity, attentional difficulties, and problems with family life and relationships.

## Discussion

This study was the first to investigate the psychometric  properties  of  the  Danish  version  of the  ICU,  and  the  results  generally  support  the reliability, criterion validity, and construct validity of this tool. The participants in this study were adolescent boys who had been remanded or sentenced to secure institutions in Denmark. Because  most  of  the  reliability  and  validity  data from this study were comparable to those previously reported for both community and incarcerated samples in North America and Europe, by  extension,  this  study  also  lends  further  support to  the  cross-cultural  validity  of  the  ICU  as  a  selfreport  measure  of  CU  traits.  Moreover,  for  nonEnglish-speaking  countries  such  as  Denmark,  the adaptation of important measures and the evaluation of their psychometric strengths and weaknesses are vital to make these tools available to national  researchers  and  clinicians.  Although  most of the current results are consistent with those that have been previously published, some warrant further discussion.

## Reliability  of  the  Danish  Inventory  of  CallousUnemotional Traits

Results for internal consistency and test-retest reliability were satisfactory by conventional standards  and  comparable  with  those  previously published, which indicates that the Danish ICU is a reliable  measure  of  CU  traits  among  incarcerated adolescent boys. Item-total correlations revealed that item 10 was the only item to lower alpha values for two of the ICU scales; this was also reported in some previous studies (62). It should be noted that estimates of test-retest reliability were obtained from  a  somewhat  small  subsample  and  only  for  a period  of  approximately  nine  days.  Given  that  CU traits are conceptualized  as  personality  traits, it could  be  argued  that  longer  test-retest  periods  are warranted  before  we  are  able  to  draw  more  firm conclusions regarding this aspect of the  ICU's reliability.

Criterion  Validity  of  the  Inventory  of  CallousUnemotional  Traits  Against  the  Psychopathy Checklist: Youth Version In this study,  the  ICU  showed  good  criterion validity  with  the  PCL:YV;  this  was  as  expected  on the basis of theoretical grounds but not in accordance  with  that  of  two  previously  reported studies comparing the ICU with the PCL:YV. The correlations  obtained  in  the  present  study  ranged from moderate to large. Furthermore, we found that the ICU total scale was significantly associated with the  PCL:YV  total  as  well  as  the  affective  and behavioral  factors,  which  yielded  incremental  gains for  the  (cross-sectional)  prediction  of  variance  on the three PCL:YV scale scores over and above other demographic and clinical variables. Results from the ROC  analyses  further  corroborated  these  findings by demonstrating good discriminatory ability of the ICU for the categorical classification of participants in  high  and  low  psychopathy  groups  based  on  a score of 25 on the PCL:YV as the threshold. Taken together,  these  findings  suggest  that  the  ICU  has good concurrent and discriminative criterion validity with the PCL:YV, particularly with regard to the total and affective scales.

However,  there  are  some  discrepancies  between the  results  of  this  study  and  the  two  previously published investigations addressing this topic. Fink and colleagues (70) reported obtaining a somewhat low  but  significant  correlation  ( r =  .27; p <  .05) between the ICU and PCL:YV total scales, whereas Feilhauer  and  colleagues  (63)  obtained  a  small  and non-significant association ( r =  .13; p =  nonsignificant). In the Feilhauer study, however, one of the  ICU subscales  was  reported  to  be  significantly correlated  with  both  the  PCL:YV  total  ( r =  .24; p <  .05) and  the  interpersonal/affective  factor ( r = .27; p < .05). How can these disparate findings be explained? First, it may be important to contextualize the findings of the two studies. Indeed, studies examining various other self-report measures of psychopathy associations with the PCL:YV have reported comparably disparate results,  with  correlations  varying  from  low  to  high in  magnitude  and  with  a  general  tendency  toward obtaining moderate associations (51,57). Similar tendencies  have  also  been  found  within  the  adult literature  (108).  Thus,  the  discrepancies  are  not specific  to  the  ICU  but  actually  characteristic  of most self-report instruments that measure psychopathic traits  when  they  are  validated  against rater-based  measures  such  as  the  PCL:YV.  Part  of the  explanation  of  this  tendency  toward  obtaining primarily moderate associations between the PCL:YV and other self-report measures of psychopathic traits in youth is due to heteromethod assessment effects (73,109). Within this context, the difference between results of the studies is perhaps not so unexpected or unusual.

Second, sample and cross-cultural differences could have influenced the results. In  the  Feilhauer study, a Dutch sample of detained youth was used. Fink's  American  sample  was  comprised  of  both girls and boys with a mean age of 17 years who were incarcerated  at  a  Southwestern  juvenile  maximumsecurity  detention facility.  With  regard  to  ethnicity, 73% of the participants were classified as Hispanic. Moreover, participants in the studies were volunteers, and very little information was presented regarding the participants who refused to participate.  Such  sample  differences  may  explain some of the discrepancies

Third,  characteristics  of  the  PCL:YV  could  be invoked as part of the explanation. For instance, the reliability for PCL:YV factor scales in both the Fink and  Feilhauer  studies,  as  assessed  with  Cronbach's alpha,  was  below  .70;  in  our  study,  the  reliability ratings  were  above  this  threshold. 1   In  terms  of internal  consistency  as  measured  by  Cronbach's alpha,  it  is  likely  that  the  low  reliability  of  the PCL:YV  factor  scales  has  to  do  with  the  low number of items on the PCL:YV factor scales (53). Stronger  statistical  indices  of  the  reliability  of  the PCL:YV factor scales obtained from factor analytic and  structural  equation  modeling  as  well  as  itemresponse analysis does in fact support the reliability of these scales (46,57). Moreover,  in all three studies,  internal  consistency  of  the  PCL:YV  total scale was acceptable, thus making it unlikely that the reliability of the PCL:YV scales can actually add to the explanation of the divergent results.

Fourth, sample size was a general limitation in all three studies, including the present one, effectively reducing  statistical  power  and  perhaps  introducing sampling  bias  (110,111).  This  may  also  help  to explain  the  discrepancies  between  our  results  and those found in the literature. Regardless, this remains  certainly an important  issue for future researchers to address by focusing on the associations between  self-report and  rater-based assessment of psychopathic and CU traits as well as potential mediators and moderators of these associations across samples and cultures.

## Construct Validity

The  obtained  results  provide  further  evidence  for the  cross-cultural  construct  validity  of  the  ICU  by demonstrating  expected  convergent  and  divergent associations  with  ratings  of  self-reported  empathy and aggression and expert-rated psychosocial impairments.

The associations with elevated scores of reactive and proactive aggression are consistent with previous research regarding links between CU traits and types of aggression (4,62,63,112-114). The tendency  of  the  ICU's  callousness  and  uncaring subscales to be particularly correlated with aggression  is  also  consistent  with  the  results  of previous research (50,61,107).

Reliability data for the PCL:YV scales are available at request from the

1 first author and will be published in another article.

Regarding empathy, as predicted and as reported in earlier studies (4,62), the ICU was highly negatively  correlated  with  all  four  dimensions  of empathy  as  measured  with  the  IRI,  especially  the empathic  concern  scale.  This  is  consistent  with developmental  research,  which  suggests  that  CU traits in boys  are  associated with  less affective empathy  or  reduced  responsiveness  to  distressing stimuli (20,22,44,115,116). It is also consistent with developmental  research,  which  has  indicated  that high levels  of  empathy or sympathy for others are negatively related with antisocial behavior (117,118).

Although most research into CU traits has tended to focus on aggression and criminal behavior, comparatively  little  research  has  investigated  their association  with  psychosocial  functioning.  In  this study,  we  found  that  CU  traits  were  positively associated  with  psychosocial  impairments.  These findings are consistent with recent research that has suggested  that  CU  traits  are  independently  and longitudinally  associated  with  psychiatric  problems in  the  community  (10)  and  clinical  severity  (9). Together,  these  results  suggest  that  CU  traits  are associated  with  considerable  psychiatric  treatment needs. Moreover, CU traits were significantly associated with social problems, and this is consistent with previous research (9,60,61).

At the item level of the HoNOSCA, two notable findings  emerged  that  warrant  comment.  First,  in this study, the ICU was significantly and moderately associated  with  poor  school  attendance  (item  13) but not with scholastic and language skills problems (item 5); however,  the  latter item was  actually correlated with the ICU total ( r =  .26),  uncaring ( r =  .26),  and  callousness  ( r =  .22)  scales  at  the  .05 level  of  significance.  One  could  interpreted  these results  as  indicating  that  problems  with  academic achievement are more related to a lack of concern about educational performance, as indicated in the DSM-5 conceptualization of CU traits, rather than with  learning difficulties.  Such  an  interpretation would  be  consistent  with  previous  studies,  which have shown that clinically referred boys with conduct problems and high levels of CU traits are less likely to be assigned to special teachers and thus experience  fewer  learning  difficulties  as  compared with boys with low levels of these traits (9). However, another study failed to obtain any significant association between CU traits and academic  performance  (119),  which  indicates  that further  research  is  needed  to  discover  the  links between CU traits and academic performance.

The association between the ICU and the HoNOSCA item concerning hallucinations, delusions,  and  abnormal  perceptions  (item  7)  was also  notable.  Although  none  of  the  participants were  currently psychotic when  included  in the study, many participants showed a tendency toward suspicious and paranoid thoughts, which is rated on this item (88). The obtained association is consistent with studies reporting a relatively high prevalence of paranoid  and  schizotypal  personality  disorders  in offender samples (120,121). Paranoid and schizotypal personality disorders are severe disorders  on  their  own,  but  they  also  increase  the risk  of  the  future  development  of  psychosis  or schizophrenia  (122,123),  which  suggests  that  they can be viewed as prodromes of the future psychotic illnesses  that  are  common  in  forensic  populations (124).  Furthermore,  the  tendency  toward  paranoid thoughts  and  perceptions  is  in  accordance  with recent research that has focused on distorted social cognition and dysfunctional mentalizing characteristics of psychopathy and antisocial personality disorder (43,125-127).

## Limitations and Future Directions

Several  methodological  limitations  must  be  taken into  account  when  interpreting  the  results  of  this study. Sample size was the most important limitation.  The  sample  size  was  relatively  small  as compared  to  some  other  studies  of  the  ICU.  The small sample size may  have reduced statistical power for identifying weak but significant correlations  between  the  ICU  and  other  measures. In  addition,  the  sample  size  did  not  allow  for sufficient  power  to  explore  the  underlying  factor structure or the structural validity of the ICU nor to assess the extent to which the ICU and the PCL:YV are concordant with latent-variable statistics, including  item  response  theory,  which  is  generally considered statistically stronger than the correlation and regression analyses used in this study (128,129). Future research using item response theory models is  needed  not  only  to  examine  the  concordance of the ICU  and  PCL:YV  but  also  to assess the differential  item  functioning  of  the  ICU  across cultures and samples.

The nature of the sample was another limitation that  may affect the  generalizability  of  our  findings. In this study, the sample was comprised of remanded and sentenced adolescent boys in secure institutions.  Future  studies  are  needed  to  examine whether the findings of this study are reproducible in  different  samples,  including  samples  of  female offenders, clinical samples, and community samples. The study design was cross-sectional, which implies that cause and effect cannot be inferred. We can also not infer anything about predictive validity.

Furthermore,  the  results  of  this  study  should  be interpreted  with  respect  to  the  research  context  in which  it  was  conducted.  Participants  were  aware that their test results would  only  be  used  for research purposes and treated confidentially, so the test results had no practical consequences for their institutional stays or their court cases. Accordingly, the  participants  in  this  study  may  have  been  more honest in their responses on the ICU than they may have been if they were assessed in contexts in which the  results  affect  case  management  and  judicial decision  making.  It  is  therefore  unclear  whether similar  results  would  be  obtained  if  the  data  were gathered in the context of routine clinical and court assessments. This is an important applied issue for future studies to address.

Finally,  it  should  be  emphasized  that  the  ROC analysis of the ICU against the PCL:YV, as reported in this study, should not be interpreted as indicating that the ICU could or should be used as a screening tool for psychopathy.

## Clinical Implications

The  ICU  seems  promising  as  an  extended  selfreport  measure  of  CU  traits  that  can  be  used  in research to shed light on the developmental precursors of psychopathy. With an improved understanding  of  the  complex  causative,  risk,  and protective  factors  as  well  as  the  developmental trajectories of psychopathy, clinicians and researchers are better equipped to develop targeted prevention and treatment programs, thereby ultimately  lessening  the  burden  of  this  debilitating disorder on society, families, victims, and individuals with CU traits. The ICU may be a useful assessment instrument for the diagnostic evaluation of conduct-disordered youth.

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