Is callous always cold? A critical review of the literature on emotion and the development of callous–unemotional traits in children

Low emotional responsiveness is considered a core feature of callous–unemotional (CU) traits in childhood and, in the context of antisocial behavior, a precursor of psychopathic traits in adulthood. However, recent findings suggest that CU traits are not always characterized by low emotional responsiveness and the evidence base requires review. This review asks a fundamental question— ‘Is callous always cold?’—with a specific focus on emotional responsiveness and CU traits in children with conduct problems (CPs). PRISMA review protocols were followed to identify literature reporting on emotional responsiveness for children 3–18 years with CPs and varying (high and low) CU traits. Results from eligible studies were contrasted by age (children 3–11 years, adolescents 12–18 years), emotional responsive measurement type (physiological, behavioral, self-report), emotion-eliciting stimuli type (interactive activities, static imagery, film) and socio-emotional context of the stimuli (other-orientated, self-orientated, neutral). This review highlights considerable variation in results across studies: reduced emotional responsiveness was not synonymous with participants demonstrating high CU traits. A more consistent picture of reduced emotional responsiveness in participants with high CU traits was found when studies used physiological measures, when stimuli were other-orientated in socio-emotional context, and in older, adolescent samples. In conclusion, this paper advocates for a more nuanced understanding of the relationship between high CU traits and the specific factors involved in emotional responsiveness, ultimately suggesting that callous is not always cold. Given that emotional responsiveness is central to theories of moral development, these findings may suggest innovative approaches to early intervention.