The first aim of this study was to examine the factor structure of the original and five shortened versions of the ICU in a UK sample. The second aim was to investigate the measurement invariance of the best-fitting model in the UK sample, and then use this model to examine its measurement invariance (i) across gender, and (ii) between the UK and Chinese samples of school children. Our results indicated that the two-factor ICU-11 featuring Callousness and Uncaring dimensions produced the best fit and was invariant across girls and boys in the UK sample. The ICU-11 had a similar item-factor combination and factor loadings for the UK and Chinese samples; however, item thresholds were not equivalent across groups, indicating that it is not meaningful to compare average scores for school students in these two nations.
Confirmatory Factor Analysis
The current study tested and compared the original 24-item ICU and five different shortened versions. Consistent with past studies (see [
18] for a review), the three-factor model of the original ICU was a poor fit in the UK sample. The strongest support was found for the two-factor second-order model, consistent with past studies examining the item-factor structure of the ICU [
28,
37,
38]. The ICU-11 was the best fitting model, outperforming the ICU-12 on two indices (CFI and TLI values), but with slightly lower RMSEA than the ICU-12. Both the ICU-11 and ICU-12, however, were a much better fit for the data than the other shortened versions. Past research has also shown the strongest support for the two-factor, 11- and 12-item versions using different sample types [
19,
24,
25,
28,
37]. The ICU-11 and the ICU-12 contain a two-factor structure and similar items—the only difference between the two versions is that the ICU-12 includes item 6 ‘do not show emotions’—therefore it is not surprising that they yielded similar fit results.
The ICU-11 does not include any items from the Unemotional scale, suggesting that these items index a construct that is distinct from the Callousness and Uncaring dimensions. Furthermore, the internal consistency of the ICU-24 and ICU-11 in the UK and Chinese samples was acceptable or good for all total and subfactor scores, except for the unemotional factor of the ICU-24. The poor construct validity, low internal consistency and poor external validity of the Unemotional scale has been replicated in many studies [
14]. The Unemotional scale items may not be precisely measuring emotion as related to CU features. Rather than a global reduction in affect, the intensity of emotion for children with CU traits appears to differ across emotion types. CU traits are associated with reduced guilt, fear and sensitivity to others’ distress, while anger appears to be experienced more intensely [
6]. It is challenging to assess the affective features of CU traits given the complexity of emotions that are rapidly elicited, experienced and expressed in constantly changing sequences of social interaction in the few short words permitted within a questionnaire format [
50]. Self-report questionnaire ratings have shown weak associations between CU traits and positive affect [
51], but studies examining positive emotion in context found that children with elevated CU traits displayed intense positive affect (e.g., joy, excitement) when engaging in risk-taking activities, bullying others, or witnessing others’ conflict [
52], and reported feelings of pride when failing to reciprocate to others who have helped them [
53]. The affective features of CU traits may necessitate multiple assessment methods, including ‘other’-informant interviews and experimental tasks.
Similar to past research [
36], latent means were lower for girls on uncaring traits, but there was no gender difference for the latent means for callousness. The factor structure and strengths of factor loadings of the ICU 11 were equivalent across boys and girls, consistent with past research examining the gender invariance of the ICU [
12,
22,
23,
36]. Furthermore, results indicated that mean scores of the ICU-11 might be directly comparable for both genders. Therefore, while there is strong evidence for gender differences in terms of the severity of CU traits, degree of psychosocial impairment and patterns of comorbidity [
12,
52‐
54], studies examining the gender invariance of the ICU have uniformly found that ICU scores are equivalent across boys and girls. Given that boys show greater social and academic impairment than girls in the school setting [
8,
33,
36], it is important that measures demonstrate equivalence across gender to ensure the accurate identification of at-risk children for school-based intervention.
Examination of the measurement invariance of the ICU-11 across nations indicated that it has a similar item-factor structure and factor loadings for Chinese and UK school students. Only one item “The feelings of others are unimportant to me” showed a stronger association with the Callousness factor in the Chinese sample than the UK sample. This may reflects a cultural difference in that Chinese culture more promotes Zhongyong thinking style (encourages individuals to consider others’ thinking and a willingness to ‘step back’ during conflict to promote interpersonal harmony) and vertical collectivism (willingness to sacrifice one’s own benefits for the sake of the group benefits) [
39].
A strict invariance model of the ICU-11 only achieved adequate model fit when item intercepts were freed for four items—more than a third of the total scale items. It is difficult to establish strict measurement invariance between Chinese and UK samples. This indicates that mean ICU-11 scores may not be directly comparable across UK and Chinese school children, although comparison of ICU-11 scores with reference to external criteria (e.g., antisocial behaviour, empathy) are feasible. The variation of item intercepts or thresholds may be due to UK or Chinese school children systematically rating some items much higher or lower than the other group, potentially due to a social norm. The item that displayed the largest difference was the item “I do not care about doing things well”. Chinese children were more likely to endorse option 1 (slightly true for me) while the majority of UK children endorsed the option 0 (not true at all). One possible explanation is that Chinese schools and parents usually hold high expectations for children in relation to achievement [
55]. Chinese children endorsed option 1, suggesting they may perceive that their level of effort may not meet the expectations of parents and teachers. Other items that showed differences included the item “I apologize (“say I am sorry”)” to persons I hurt”, where Chinese children were more likely to score 1 or 2 (somewhat true or very true for me), while UK children were slightly more likely to score 3 (definitely true); and the item “I do not feel remorseful when I have done something wrong” where Chinese students were more likely to score 0 or 1 (not at all true or somewhat true), while UK students were slightly more 2 and 3 (very true or definitely true). This is interesting as it suggests that while UK students understand the social value in apologizing, they do not actually feel sorry. Apologizing is heavily socialized in England [
56], but it may also be that the slightly older age of students in the UK sample enabled them to better understand the importance of an apology for self-presentation and the preservation of social relationships following a transgression [
57], even if the apology is not ‘felt’.
Thus, while items appear to be interpreted in the same manner by UK and Chinese school children, there are cultural differences in the strength of item endorsement. Past research on CU traits in East Asian cultures have indicated differences in the severity of CU traits across nations [
41]. Furthermore, CU traits assessed via the APSD failed to demonstrate significant relationships with aggression and antisocial behaviour in East Asian children [
58,
59], despite the status of these constructs as well-established correlates of CU traits in Western samples [
1]. East–West comparisons of adult psychopathic traits has provided support for the universality of this construct [
39]; however, research in children appears to suggest cultural variation in the manifestation of CU traits and externalizing problems. Now that the reliability and validity of the ICU-11 has been established in community and detained samples [
37,
38], future work should extend investigation to understanding East–West cultural variation in the psychological processes underlying CU traits.
Limitations and Future Directions
This study has several limitations that should be acknowledged. The UK and Chinese samples were non-referred children from a single school in each nation. It is important to validate brief measures in nonclinical samples before CU traits and antisocial behaviour becomes severe and impairing. However, our findings may not generalize to clinical, forensic or adjudicated samples due to the restricted range of CU traits likely to be present in mainstream school samples. The UK sample also featured secondary school students whose average age was slightly older than that of the Chinese primary school students. While norms for the ICU [
60] indicate higher total scores for adolescents (15–17 years) compared to children (11 to 14 years), past research in children aged 11 to 14 years found that ICU scores did not differ across grade level [
36]. Thus, increasing CU traits severity with age appears to be present across a larger age range that is present in the current study. Increasing CU trait severity with age has been attributed to various factors, including the effects of puberty [
61], lesser ability of children to engage in self-reflection regarding their own attributes, and increased uncaring and antisocial attitudes in adolescence [
22]. However, differences in the mean value of ICU does not mean that the factor structure differs across age groups. Indeed, past research indicates that while younger children had lower scores on the Uncaring scale than older children, ICU scores were invariant across child age, showing similar factor variances and factor loadings [
22]. This study also focused solely on the self-report version of the ICU. Inclusion of the parent and teacher versions of the ICU would enable the examination of cross-informant invariance. Nevertheless, self-report information is crucial for gaining insight into subjective experiences that teachers and parents may be unaware of, particularly antisocial tendencies and attitudes [
13,
23]. It should be noted that there are differing norms depending on the country in which the sample is tested. Future research should develop norms for the ICU-11 in different nations.
Current study findings highlight the importance of investigating the equivalence of measures across cultures, due to potential differences in item interpretation and ratings based on cultural values and perceptions of deviance from social norms. Future research should include external correlates of CU traits to better identify the construct invariance of this measure between UK and Chinese school children. Ideally, this would go beyond antisocial behaviour to encompass the emotional, cognitive and biological correlates of CU traits (e.g., reduced amygdala activation). Nevertheless, to the best of our knowledge, this study it is the first to compare the ICU in a Western and an East Asian nation. This is also the first study to examine the factor structure of the original and short forms and gender invariance of the ICU in a UK sample. The validation of a brief measure enhances our understanding of CU traits, enables greater precision in its measurement and reduces the assessment burden for future research participants.
In conclusion, this study found that a short form of the self-report ICU featuring 11 items and a two-factor structure (Callousness and Uncaring dimensions) demonstrated better construct validity than the original form. Our findings provide further support for the gender invariance of the ICU [
12,
22,
23,
36] and extends prior work by showing that the 11-item, self-report version shows acceptable to good internal consistency and is invariant for boys and girls in the UK. The ICU-11 may therefore be preferred to the original form in UK children aged 11 to 14 years. There is increasing interest in CU traits and school-related risk factors [
9,
33,
52]. As such, a reliable, valid and time-efficient measure of CU will facilitate research in children attending mainstream schools. The cross-cultural comparison indicated that the item-factor structure and factor loadings were equivalent for Chinese and UK school children; however, mean ICU-11 scores are not directly comparable for these two groups. The extension and replication of the current findings into other Western and East Asian nations would increase our understanding of the cultural implications of the manifestation and development of CU traits in children.