 callous-unemotional traits, social interaction and social communication difficulties.  (DOCX)  ######   Click here for additional data file.  ###### Cross-twin within-trait and cross-trait correlations, stratified by zygosity and gender using teacher-report data for callous-unemotional traits, and parent-report data for social interaction and social communication difficulties.  (DOCX)  ######   Click here for additional data file.  ###### Model fitting results for the Independent Pathway Models using teacher-report data for callous-unemotional traits, and parent-report data for social interaction and social communication.  (DOCX)  ######   Click here for additional data file.  [^0]: **Competing Interests:**The authors have declared that no competing interests exist.  [^0]: Conceived and designed the experiments: EO 