'Nature not nurture' is to blame for aggressive children

Young children have an innate tendency to be aggressive that they have to learn to control in their pre-school years if they are to avoid being violent and antisocial later in life, an expert in childhood behaviour has found.

Toddlers are born with aggressive instincts rather than learning to be violent from their surroundings. What they do have to learn, however, is how to control this instinctive behaviour in the critical years before they start school, Professor Richard Tremblay of the University of Montreal said.

"Physical aggression in children is a major public problem," he said. "It is not only an indictor of aggression in adulthood, but is also leads to other behavioural problems such as alcohol and drug abuse, violent crime and continues the cycle of abusive parenting.

"Developmental studies show that infants aged three to four years old are more physically aggressive than adults," Professor Tremblay added. "We clearly see that the frequency of physical aggressions among children decrease substantially from the pre-school years to adolescence, except for a small group who use physical aggression most often throughout that period."

Professor Tremblay, a professor of paediatrics, psychiatry and psychology, will review his findings today at a lecture on the origins of aggression at the Royal Society in London.

There is much debate about whether children learn to be violent or are born with aggressive instincts but the most recent studies suggest that aggression is the "default" position and that it is a child's ability to learn to control it that results in stark differences in behaviour between older children and adolescents.

If toddlers are surrounded by adults and other children who are physically aggressive, they will probably learn that physical aggression is part of everyday social interactions, Professor Tremblay explained.

"On the other hand, if a child lives in an environment that does not tolerate physical aggression, and rewards pro-social behaviour, it is likely that the child will acquire the habit of using means other than physical aggression to obtain what he or she wants, for expressing frustrations," he said.

"This is the case for most children. All but a very small minority are using physical aggression more often in early childhood than later on. Apparently we do not need to learn to 'aggress'. We need to learn not to 'aggress'," Professor Tremblay added.

Various factors have been linked to childhood aggression, such as whether the parents are separated at the time of birth, low parental income, whether the mother has a history of antisocial behaviour and physical abuse within the family. Being able to identify the children most at risk could lead to better intervention and prevention.

"Identifying the factors which stop children becoming well-socialised adults should help us design preventative measures which are employed at the right time in a child's development," the Professor Tremblay said. "These should put an appropriate emphasis on the behaviour of the parents, as well as that of the child.

"Learning how not to be violent ... is dependent on both genetic and environmental factors. These range from the type of parental care a child receives to whether its mother smoked when pregnant.

"Research has shown, for example, that nicotine affects the development of areas of a baby's brain which are responsible for emotional control."