*The following is excerpted from an online article posted on PsychCentral.
A new study of identical twins found that the child who experienced harsher behavior and less parental warmth was more aggressive and exhibited more callous-unemotional traits, such as a lack of empathy and a moral compass.
In a study of 227 identical twin pairs, researchers at the University of Pennsylvania, the University of Michigan and Michigan State University analyzed small differences in the parenting that each twin experienced to determine whether these differences predicted the likelihood of antisocial behaviors. They found that the twin who experienced stricter or harsher treatment and less emotional warmth from parents had a greater chance of showing aggression and callous-unemotional (CU) traits.
“Some of the early work on callous-unemotional traits focused on their biological bases, like genetics and the brain, making the argument that these traits develop regardless of what is happening in a child’s environment, that parenting doesn’t matter,” said Dr. Rebecca Waller, an assistant professor in Penn’s Department of Psychology, who led the study.
“We felt there must be something we could change in the environment that might prevent a susceptible child from going down the pathway to more severe antisocial behavior.”
The work is the latest in a series of studies from Waller and her colleagues using observation to assess a variety of aspects of parenting. The initial research, which considered a biological parent and child, confirmed that parental warmth plays a significant role in whether CU traits materialize.
A subsequent adoption study of parents and children who were not biologically related turned up consistent results.
Knowing this led Waller and University of Michigan psychologist Dr. Luke Hyde to team with Dr. S. Alexandra Burt, co-director of the Michigan State University Twin Registry. Using 6- to 11-year-old participants from a large, ongoing study of twins that Burt directs, the team turned its attention to identical twins.
For 454 children — 227 sets of identical twins — parents completed a 50-item questionnaire about the home environment. They also established their harshness and warmth levels by rating 24 statements such as “I often lose my temper with my child” and “My child knows I love him/her.”
The researchers assessed child behavior by asking the mother to report on 35 traits related to aggression and CU traits.
“The study convincingly shows that parenting — and not just genes — contributes to the development of risky callous-unemotional traits,” said Hyde, an associate professor in Michigan’s Department of Psychology. “Because identical twins have the same DNA, we can be more sure that the differences in parenting the twins received affects the development of these traits.”
According to Waller, a potential next step is to turn these findings into interventions for families trying to prevent a child from developing these traits or to improve troubling behaviors that have already begun.
“This provides strong evidence that parenting is also important in the development of callous-unemotional traits,” Hyde said. “The good news is we know that treatments can help parents who may need extra support with children struggling with these dangerous behaviors.”
The study was published in the Journal of the American Academy of Child and Adolescent Psychiatry.