In a study of twins aimed at teasing out answers to an aspect of the classic nature-versus-nurture debate, researchers have found that the child who was more harshly disciplined than the sibling twin was more likely to develop more behavior problems.
This was determined by researchers at three prominent universities who studied sibling pairs treated differently by their parents. Among the 1,030 sets of twins studied were 426 pairs who were genetically identical. Among the latter group, the difference in the level of behavioral problems they developed could only be attributed to the difference in how they were parented, and not in their genetic makeup, researchers at the University of Texas at Austin, Michigan State University and the University of Michigan concluded in a recently published study.
The results of this research are consistent with many other studies that have linked children’s antisocial behaviors, especially more severe ones, to being yelled at or spanked by their parents. But in this case, the research team wanted to explore a common counterargument: that children act out and develop aggressive and antisocial behaviors because they inherit parental genes linked to such behaviors.
“Studies into the effects of physical punishment have led the American Academy of Pediatrics to recommend against physical punishment and numerous countries to ban physical punishment including spanking,” said Elizabeth Gershoff, professor of human development and family sciences at the University of Texas at Austin and an author of the study. “This is the latest research to show that harsh punishment has a direct line to more, not fewer, behavior problems in children.”
Lead author Alexandra Burt, a professor of psychology at Michigan State added that her team “found no evidence to support a genetic explanation” for the difference in levels of the kids’ misbehavior within a given pair of identical twins. “The differences in the harsh parenting each twin received predicted differences between the twins in antisocial behavior, even when they shared 100% of their genes.”