Studies on young children have identified a genetic link for some such disorders, but environmental factors also have an effect

Humans have succeeded as a species in large part because of our ability to cooperate and coordinate with each other. These skills are driven by a range of “moral emotions” such as guilt and empathy, which help us to navigate the nuance of social interactions appropriately.

Those who lack moral emotions are classed as having “callous-unemotional” traits: persistent personality characteristics that make negotiating social situations difficult. The combination of callous-unemotional traits and antisocial behaviour in adolescents and adults is typically diagnosed as psychopathy.

Moral emotions can be measured in children as young as three. Persistent personality traits aren’t measured in children this young, but recent research has begun to explore whether repeated callous-unemotional behaviours might be evident even in preschoolers. Such behaviours include parental observations that punishment doesn’t change behaviour, that the child shows little affection toward people and seems unresponsive to affection from others.



What happens to children who show callous-unemotional behaviour?

At least half of children who exhibit callous-unemotional behaviours will naturally grow out of them. Only if they persist into adolescence do they become classified by psychiatrists as persistent personality traits.



However, callous-unemotional behaviours in a young child in combination with other risk factors can be a warning sign for later social difficulties and behaviour disorders. For instance, callous-unemotional behaviours in early childhood have been shown to predict aggressive behaviours, attention deficit hyperactivity disorder and oppositional defiant disorder and are a risk factor for later psychopathy.

Research into callous-unemotional behaviours in young children is important because this is when intervention is most effective. Recognising what factors underpin callous-unemotional behaviours, attention deficit hyperactivity disorder and oppositional defiant disorder will support better and earlier interventions.

Untangling the roots of behaviour disorders

Megan Flom and Prof Kimberly Saudino at the Boston University Twin Project have been exploring genetic and environmental influences that predict callous-unemotional and other behaviour disorders in children.



Callous-unemotional behaviours are associated with moral maladaptations, oppositional defiant disorder with emotional regulation problems and attention deficit hyperactivity disorder associated with lack of impulse control. No research before has explored the relative contribution that genes and environment make to these disorders.

Flom and Saudino’s study followed a sample of over 300 twins assessed at two and three years of age to examine change over time. To assess callous-unemotional behaviour, parents rated their child on a series of questions measuring typical examples of this. Genetic information was collected from cheek swab samples and information on their environment was provided from questionnaires completed by their parents.

The study replicated findings from previous studies: callous-unemotional behaviour is underpinned by genes, meaning that in the instance of one twin exhibiting callous-unemotional behaviours, callous-unemotional behaviours were significantly more likely to be shared by an identical twin than a fraternal twin.

However, the study also provides novel insight into the genetic and environmental links between callous-unemotional behaviours, attention deficit hyperactivity disorder and oppositional defiant disorder. The results show that all three share the same genetic root and environmental factors determine which of the disorders the child experiences.

Approximately 50% of the genetic and environmental influences are unique to each of the three behaviours. In other words, the shared genetic factors account for approximately half of the influence deciding which disorder is exhibited. The remaining half of the influence is explained by individual genetic and environmental factors that were crucial to each specific disorder.

Although the effect was weaker, environmental factors also predicted callous-unemotional behaviours in children. While identical twins share many of the same environmental influences such as the house they live in and the school they attend, they also differ. For instance, they usually have different friends and teachers. The study found that non-shared environmental factors largely accounted for the differences between behaviour disorders.

Real-world consequences

Researchers are interested in exploring the onset of callous-unemotional behaviours because they are an early warning sign in some children of later behaviour difficulties and, potentially, mental health disorders. One particular concern is that children who show high rates of callous-unemotional behaviour in combination with antisocial behaviour at seven years of age are at substantial risk of being diagnosed with psychopathy later in life.

Psychopathy isn’t always linked to violent outcomes. In a clinical sense, psychopathy is characterised by a lack of empathy, superficial charm, persistent antisocial behaviour, insensitivity to punishment and impulsivity. In some contexts, these traits can be an advantage. However, psychopathy is more commonly linked in the public imagination with crime.

Psychopathy is rare, affecting approximately 1% of the general population. But psychopaths are 20 to 25 times more likely to be imprisoned compared with non-psychopaths. Both in monetary terms for the criminal justice system and the social damage that their crimes inflict, the cost of psychopathy is disproportionately high.

Callous-unemotional behaviours are a vital piece of the puzzle when studying psychopathy. Research on callous-unemotional behaviours in young children furthers the understanding of the influence of genes and environment and the links between callous-unemotional and other behaviour disorders. This understanding could potentially contribute to more effective interventions and treatments for these disorders.