The aims of the present study were to investigate the fundamental factor structure of psychopathic personality traits in a community sample of children and to examine the extent to which genetic and environmental factors influence these traits. EFA and CFA were performed to investigate the underlying factor structure of the data. Consistent with previous literature, our results revealed a two-factor solution to be the best fitting for psychopathic personality traits within our sample. This two-factor structure was confirmed on our pre-adolescent sample using 12 of the 14 CPS subscales. Two subscales, grandiosity and lack of guilt, were dropped due to lack of clear factor loadings.
These results fall in line with previous studies that have also found a two-factor structure to account for psychopathic traits in children and adolescents (Frick et al. 1994
; Brandt et al. 1997
; Salekin et al. 2001
). The present study found and confirmed a two-factor structure that is somewhat different from the factor structures obtained in the adult literature (Hare, 1991
; Cooke & Michie, 2001
). Hare’s (1991)
two factors comprise ‘affective-interpersonal’ features (e.g. glibness, superficial charm, lack of empathy; factor 1) and ‘socially deviant life-styles and behaviors’ (e.g. impulsivity, sensation seeking, irresponsibility, poor behavioral control; factor 2). The first factor identified in the present study, the callous/disinhibited factor, includes characteristics and traits such as behavioral dyscontrol, callousness and lack of empathy, while the second factor, the manipulative/deceitful factor, includes characteristics such as glibness and untruthfulness. Differences in the factor structures – notably the alignment of the callous and poverty of affect subscales with the factor reflecting behavioral dyscontrol instead of the more interpersonal one reflecting manipulative deceit of others – may be due to the fact that the sample comprises a young, pre-adolescent community sample that has yet to experience the influences of others, including peers. Differences may have also arisen due to changes in development. One might not necessarily expect to find identical factor structures in adults and in children at such a young age (Salekin, 2006
). Adult psychopathy may be confounded by the fact that adult psychopaths have experienced years of drug abuse, multiple incarcerations and physical fighting (Hare, 1983
), whereas in children we can ‘observe the development of the disorder before it has had an opportunity to destroy its host’ (Lynam, 1997
, p. 434). It is also possible that the differences in factor structure may be specific to the CPS instrument, which was essentially created as a downward extension of an adult construct. Perhaps a different approach to developing an instrument designed to assess affective, interpersonal and dysregulated behaviors specifically in children might yield a factor structure more closely aligned to Hare’s conceptual framework in adults.
Subsequent genetic analyses conducted on the two psychopathic personality dimensions (composite factors) demonstrated significant heritable as well as unique environmental effects of psychopathic personality traits, with significant differences between boys and girls. Specifically, heritability estimates for factor 1 (callous/disinhibited) were 0.64 in boys and 0.49 in girls, whereas for factor 2 (manipulative/deceitful), 0.46 of the variance was due to genetic effects in boys and 0.58 in girls. No significant shared environmental influences were found in psychopathic personality traits within our child sample.
These results are consistent with those found in previous twin studies assessing psychopathic traits in children and adolescents, which have also found strong genetic and unique environmental influences, but no significant shared environmental effects (Taylor et al. 2003
; Viding et al. 2005
; Blonigen et al. 2006
; Larsson et al. 2006
). However, those studies either did not explore sex differences or did not find any sex differences within their samples. The present findings revealed significant genetic influences on both callous/disinhibited and manipulative/deceitful traits in both girls and boys just prior to adolescence.
Furthermore, the relationship between the callous/disinhibited and manipulative/deceitful traits in both boys and girls was mediated by both genetic and environmental factors common to both traits. Specifically, the bivariate genetic correlation between the two factors was rg=0.48 in boys and rg=0.57 in girls. The unique environmental correlations were re=0.41 in boys and re=0.30 in girls. Two traits may be related because they share genetic or environmental influences. Nonetheless, both the genetic correlation and the unique environmental correlation were significantly less than 1.0, indicating a less than complete overlap in the etiologies of callous/disinhibited and manipulative/deceitful traits. These results give further support to the notion of a two-factor structure underlying psychopathic traits in children and highlight the significant overlap (as well as distinctions) in the etiologies of these two emerging factors.
The results of the present study were consistent with a recent study conducted by Viding et al. (2005)
on the genetic effects of psychopathy in 7-year-olds. Viding et al
. found a significant heritability for their assessment of callous/unemotional psychopathy traits in children (h2
=0.67). However, they did not look to see whether there were any significant sex differences in their data. Our heritability results of the callous/disinhibited factor were comparable to those of Viding et al
=0.64) in the boys, but not in the girls (h2
=0.49). However, when the sexes are combined in our sample, our callous/disinhibited factor yields a heritability of approximately 60%.
Given the fact that psychopathy is mostly studied in adult males (Hare, 1991
; Lalumiere et al. 2001
) and not much is known about the core construct of the disorder in children (Cruise, 2003
), the present study’s demonstration of significant genetic and unique environmental effects of psychopathic traits in both young boys and girls may be a considerable break-through or finding for the advancement of psychopathy research. However, we did not find any significant shared environmental influences in psychopathic personality traits. This could be due to the fact that DZ male correlations are anomalously low, perhaps due to biases in caregiver reports.
The present study found and confirmed a two-factor solution for children’s psychopathy traits. This is consistent with the fact that Salekin et al. (2001)
also found a two-factor solution for psychopathy in children, but inconsistent with other studies that have also found a three-factor structure in children’s psychopathic traits (Frick, 1998
; Frick et al. 2000
). This could be due to the fact that we split our twin sample into two to both explore and confirm our factor structures, whereas Frick et al
. did not have a twin sample. It could also be due to the fact that their sample contained children who were a bit older.
Study strengths and limitations
Several factors must be considered when interpreting these results. First, the study used only caregiver reports of the twins’ psychopathic-like behavior, whereas the use of other raters, including self-reports, might yield different results. Child self-reports of behaviors might also be used in a multi-rater approach in future studies to help corroborate the observed and reported psychopathic personality behaviors. However, studies that employ children’s self-reports could be affected by social desirability, poor reading skills and a general lack of comprehension, which may occur in children (Lyons et al. 1995
). Caregivers may be able to comprehend difficult and complex behaviors and constructs, such as psychopathy, better than children (Lyons et al. 1995
; Lynam, 1997
Second, the examination of psychopathic traits in children could also be questioned. It has been argued that it might not be developmentally appropriate to diagnose this syndrome in children and adolescents (Vincent & Hart, 2002
). However, there is evidence that psychopathic personality traits are developmental and may be found in child samples (Lynam, 1997
; Viding et al. 2005
). Finally, one may question the occurrence of low DZ male correlations in our sample. This might be due to some bias in the mother reports of the CPS or perhaps due to non-additive or dominant genetic effects. However, comprehensive model fitting analyses of the data revealed that an AE (AIC=−29.44) model fit the data better than a model taking dominance effects into account. Even though the low DZ male correlation might suggest dominant genetic effects at work in the boys, the moderate resemblance among DZ opposite sex pairs suggests otherwise.
Another limitation might be due to the fact that lack of guilt and grandiosity, which may be considered to be ‘core’ traits of psychopathy did not load well onto either factor in this child sample. This may be due to the fact that these traits might not properly or fully develop until later adolescence or adulthood and might not be present in children as young as 9 and 10 years old. Some aspects of psychopathy may be unsuitable or developmentally unbefitting for children (Salekin et al. 2001