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Nature versus nurture is a topic that is often visited by researchers. In a new study, researchers examined the effects of genetics and the environment on toddlers' aggression. They concluded that aggression in young children could be mostly attributed to genetic factors as opposed to environmental ones.

For this study, headed by Eric Lacourse from the University of Montreal and CHU Sainte-Justine Hospital, the team followed identical and non-identical twins in order to examine their behavior. The twin's data came from the Twins Cohort Study that was initiated by Michel Boivin of Laval University and Richard Tremblay from the University of Montreal and the University College Dublin. The study recruited parents of identical and non-identical twins who were born from April 1995 to December 1998 in Canada. The children's level of aggression characterized by hitting, biting, fighting and kicking was reported by their mothers.

They used three general patterns when assessing the effects of genetics and environment. The first involved a general viewpoint on environment and genetics, which was that "both sources of influence are ubiquitous and involved in the stability of physical aggression," the press release wrote. The second was a genetic set point model, which states that one set of genetic factors contribute to the development of physical aggression over time. The last pattern was that new environmental factors could lead to short-term physical aggression.

"The gene-environment analyses revealed that early genetic factors were pervasive in accounting for developmental trends, explaining most of the stability and change in physical aggression," Lacourse said. "However, it should be emphasized that these genetic associations do not imply that the early trajectories of physical aggression are set and unchangeable. Genetic factors can always interact with other factors from the environment in the causal chain explaining any behavior."

The study, "A longitudinal twin study of physical aggression during early childhood: Evidence for a developmentally dynamic genome," was published in Psychological Medicine.