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INTRODUCTION: Callous-unemotional behaviors (CU) predict antisocial behavior in youth. Reduced capacity for theory of mind (ToM) skills has been connected to psychopathology and may underlie lack of empathy, a component of CU. Previous research has demonstrated a link between ToM and CU, but genetic and environmental contributions to this association have not been explored. The current study seeks to examine CU and ToM in a sample of twin pairs to assess the relation between the two domains as they emerge in early childhood, as well as the genetic and environmental contributions to this relation.
METHODS: The current sample of twin pairs (n=304) consisted of monozygotic (n=141) and dizygotic (n=163) twin pairs in the Boston University Twin Project, a longitudinal study of early child behavior and temperament. The twin pairs were assessed at age 3. CU was assessed using a 5-item screening measure from the CBCL 1½-5(α=.61). Theory of mind was assessed using items from the Strengths and Difficulties Questionnaire and the Revised Rutter Parent Scales. These items target ToM skills that underlie prosocial intentions (nice ToM), and ToM skills that underlie antisocial, manipulative intentions (nasty ToM). Biometric modeling was used to estimate genetic, shared environmental and nonshared environmental contributions to these traits and their associations.
RESULTS: CU was significantly associated with nasty ToM (r=.23) and with nice ToM (r=-.15). Moderate to high heritabilities were found for CU (64%) and for nasty ToM (75%). For each variable, the remaining variance was explained by nonshared environmental factors. The association between CU and nasty ToM was completely explained by genetic factors. Lower heritability was found for nice ToM (28%). Shared and nonshared environmental factors also accounted for variance in nice ToM (Shared=27%, Nonshared=45%). The association between CU and nice ToM was completely explained by nonshared environmental factors.
CONCLUSION: The results parallel previous findings of a relationship between CU and ToM. Genetic influences underlie the correlation between CU and nasty ToM, while the correlation between CU and nice ToM is explained by nonshared environmental factors. The results indicate nasty ToM as a possible genetically-based risk factor for CU and later antisocial behavior, while nice ToM can be seen as a protective factor fostered by the environment. This suggests that nice ToM may be a malleable target for early intervention.
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