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Most people agree that aggression is a predictable—and even acceptable—part of childhood. But children who do not learn to control their aggressive tendencies as they mature are at risk for a number of problems, including poor educational and occupational outcomes and participation in violent crime.
Genetic and environmental factors have been shown to play a role in aggression, but effective interventions can prevent—and correct—negative outcomes.
While adolescence is often considered to be the most aggressive stage in an individual’s life,[1] aggression actually begins much earlier in life. Research shows that most children first exhibit aggressive tendencies around the time they learn to control their limbs.
Aggression levels rise over the toddler and preschool years peaking around the age of three-and-a-half years, after which they drop off.[2], [3] In Canada, data from the National Longitudinal Survey of Children and Youth indicate that 83% of children show a gradual decrease in aggressive behaviours between the ages of two and 11.[4] Aggression appears to be a normal part of childhood that is moderated through the process of socialization.
Even extreme aggression can be eliminated by socialization or adult interventions. For example, a recent study of aggressive kindergarten students (who picked fights and disobeyed instructions), found that, by Grade 5, most of these students had learned to control their aggression and were able to keep pace with their classmates in reading and math achievement.[5] When teachers respond appropriately to disruptive preschoolers and encourage them to observe the rewards of less aggressive, more acceptable behaviour, the aggression can be curtailed with few lasting effects.
Parental rejection: Absence or withdrawal of warmth, love or affection by parents toward their children.
Punitive parenting: Parents who often yell, threaten to hit their children or do not engage in problem-solving with their children.
Parental nurturance: Parents who seem proud, say nice things and show their children they are appreciated.
Parental monitoring: Parents know where their children are, what they are doing, who they are with and when to expect them home.
Physical aggression: hitting, slapping, kicking, biting, pushing, grabbing, pulling, shoving, beating, limb twisting, etc.
Verbal aggression: use of hostile words to insult, threaten, anger or intimidate; often accompanied by threatening gestures and frequently followed by physical aggression.
Indirect aggression: a more complex form of aggression that involves spreading rumours, attempts to humiliate or demean, or excluding the victim from a group.
Tremblay, R.E., Gervais, J. & Petitclerc, A. (2008). Early Learning Prevents Youth Violence. Centres of Excellence for Children’s Well-Being: Early Childhood Development. Accessed February 19, 2010.
Rohner, R.P., & Khaleque, A. (2002). Parental acceptance-rejection and life-span development: A universal perspective. In W.J. Lonner, D.L. Dinnel, S.A. Hayes, & D.N. Sattler (Eds.), Online Readings in Psychology and Culture. Center for Cross-Cultural Research, Western Washington University, Bellingham, WA.
Canadian Institute for Health Information (2008). Improving the Health of Canadians: Mental Health, Delinquency and Criminal Activity. Ottawa: CIHI.
Aggression can become problematic when children do not learn to curb their aggressive tendencies. Research has shown that about 5 to 10% of elementary-school students continue their aggressive behaviours, and are much more likely to become physically violent as teenagers and adults.[6]
Longitudinal research indicates that eight- to 10-year-olds who display significantly higher levels of aggression than their peers are more likely to be convicted of a violent crime as adults. They are also more likely as adults to become repeat offenders and to abuse alcohol and drugs.[7]
Children who do not learn to moderate their aggression once they start school can present a number of challenges in the educational context. Students with aggression problems often struggle with learning and academic achievement[8] and are less likely to participate in class and complete high school.[9] Aggressive outbursts can be disruptive to other students’ learning in the classroom and detrimental to student safety.[10] Integrating aggressive students who exhibit complex forms of behaviour into the school can also be a challenge, making it difficult to meet their learning needs.
Longitudinal research suggests that the academic difficulties that aggressive children encounter can persist into adulthood. A study of more than 1,200 people (856 from America and 369 from Finland) showed that those who were more aggressive as eight-year-olds were less educationally successful by their 30s and less occupationally successful by their mid-40s, compared to non-aggressive children.[11]
Both genetic and environmental factors contribute to persistent aggression in young children. Up to 50% of the variance in aggression across individuals can be attributed to genetic effects, but parenting also plays an important role.[12] Practices such as parental rejection and punitive parenting (see textbox) are associated with higher levels of aggression among children, while parental nurturance and monitoring (see textbox) are associated with lower levels of aggression.[13] The relationship between genetics and environment can also contribute to aggression. For example, children born with difficult temperaments can elicit harsh parenting responses, which in turn contribute to aggressive behaviours.[14]
Environmental factors which are often associated with aggressive behaviour among children and youth include:
According to research, half of the children who are subject to four or more of these factors go on to develop aggression problems.[15]
Another factor that contributes to aggression problems is a child’s relationship with their peers. Aggressive children are more likely to perceive the actions of others as hostile, which leads to poor relationships with their parents, teachers and peers.[16] Children who experience peer rejection are typically more prone to aggression than children who have earned the acceptance of their peers.[17] Peer rejection reinforces an aggressive attitude toward the world, which in turn perpetuates further rejection and aggressive behaviour.[18], [19], [20]
Behavioural approaches
Teach parents to alter the factors that predict problem behaviour through social learning techniques such as positive reinforcement, negotiation and finding alternatives to punishment. Group sessions allow parents to practice these techniques.
Relationship approaches
Provide parents with listening and communication skills to understand how their children relate to other children and adults.
Parenting programs can also help parents to
[i] Gibbs, J. Liabo, K., Newbery, J. et al. (2003). Group-based parenting programs can reduce behaviour problems of children aged 3-12 years. What Works for Children group Evidence Nugget.
Research has shown that problem aggressive behaviour can be greatly reduced by teaching good parenting practices. Parent Management Training (PMT) is one of the most common family-based therapies used to help manage behavioural problems at home and at school (see text box).[21]
PMT promotes positive, pro-social behaviours in children by developing proper disciplinary practices and positive social interactions between parent and child. Parents receive training on how to use reinforcement and punishment techniques appropriate to their child's behaviour. They are taught to provide consequences consistently, to encourage appropriate behaviours and to apply techniques to manage future problems. Research findings show that this training improves parenting skills, decreases family conflict and improves children’s behavioural problems.[22]
The Incredible Years is one well-known PMT program. It uses a set of training programs that are designed to promote social competence and prevent, reduce and treat problem aggression in babies, toddlers, young children and youth. The program incorporates numerous approaches to training that involve all aspects of a child’s life (parent, child and teacher) and is founded on developmental theory that sees all aspects as interacting in the development of aggression and conduct problems.
Evaluations of the Incredible Years indicate that the best and most long-lasting improvements are obtained by children whose mother (or mother and teacher) receive the training. Child training alone is not as effective as skills training for mothers or mothers and teachers.[23]
To reduce cognitive deficits that are predictive of aggression, a wide variety of learning interventions have been developed. These interventions focus on teaching children to solve interpersonal problems and help them develop stronger social skills and coping skills. Social cognitive approaches teach problem-solving and anger management skills to foster social competence and adjustment in aggressive children. They have been tested on young children with positive improvements in problem-solving and peer relationships.[24]
I Can Problem Solve (ICPS), is a school-based program for children aged four to 12 that has been shown to be particularly effective with under-privileged urban students. Through games and exercises children learn to: identify a problem, recognize thoughts, feelings and motives that generate interpersonal problem situations, generate alternative solutions to problems, and consider the consequences of these solutions.
The program teaches students to think for themselves and find their own way of solving interpersonal problems. As a way of promoting pro-social behaviour, children are encouraged to develop awareness of the emotions and thoughts that lead to conflict with peers.
Developed in 1969, the Good Behaviour Game is a classroom management strategy widely used in Grade 1 and Grade 2 classrooms throughout the United States. Children are encouraged to work together to reinforce each other’s good behaviour. Student teams are penalized with demerit points if they display inappropriate behaviour during a lesson. At the end of the day the winning team receives a prize. The key to the game’s success is the participation of all students not just those with behaviour problems. Evidence indicates that the program helps prevent problem behaviour.[25]
Although aggression is a typical occurrence during early childhood, children must learn more appropriate ways of addressing conflict and frustration. If they do not, aggression will become part of their behavioural repertoire, impeding their educational attainment, occupational success and social relations. A number of interventions available to parents and schools show promise in helping children learn to moderate aggression.
[1] Centre of Excellence for Early Childhood Development (2002). Opinion Poll Regarding Aggression among Young Children in Canada. Accessed February 19, 2010.
[2] Tremblay, R.E. (2004). Decade of behaviour distinguished lecture: Development of physical aggression during infancy. Infant Mental Health Journal, 25, 399-407.
[3] Alink, L.R.A., Mesman, J., Van Zeijl, J., Srolk, M.N, Juffer, F., Koot, H.M., et al. (2006). The early childhood aggression curve: Development of physical aggression in 10- to 50-month-old children. Child Development, 77, 954-966.
[4] Côté, S., Vaillancourt, T., LeBlanc, J.C., Nagin, D.S. & Tremblay, R.E. (2006). The development of physical aggression from toddlerhood to pre-adolescence: A nationwide longitudinal study of Canadian children. Journal of Abnormal Child Psychology, 34(1), 71-85.
[5] Duncan, G. J., Dowsett, C. J., Claessens, A., Magnuson, K., Huston, A. C., Klebanov, P.,et al. (2007). School readiness and later achievement. Developmental Psychology Vol. 43, No. 6, pp. 1428–1446.
[6] Broidy L.M., Nagin, D.S., Tremblay, R.E., Brame, B., Dodge, K., Fergusson, D., Horwood, J., et al. (2003). Developmental trajectories of childhood disruptive behaviors and adolescent delinquency: a six-site, cross-national study. Developmental Psychology 2003;39(2):222-245.
[7] Farrington, D.P. (1991). Childhood aggression and adult violence: Early precursors and later-life outcomes. In D.J. Pepler & K.H. Rubin (Eds.), The Development and Treatment of Childhood Aggression. Hillsdale, NJ: Lawrence Erlbaum.
[8] Campbell, S.B, Spieker, S., Burchinal, M. & Poe, M.D. (2006). Trajectories of aggression from toddlerhood to age 9 predict academic and social functioning through age 12. Journal of Child Psychology and Psychiatry, 47, 791-800.
[9] Jimerson, S., Egeland, B., Sroufe, L.A. & Carlson, B. (2000). A prospective longitudinal study of high school dropouts examining multiple predictors across development. Journal of School Psychology, 38(6), 525-549.
[10] Frick, J. (2004). Developmental pathways to conduct disorder: implications for serving youth who show severe aggressive and antisocial behaviour. Psychology in the schools. 41(8): 823-833.
[11] Dubow, E.F., Huesmann, L.R., Boxer, P., Pulkkinen, L., Kokko, K. (2006). Middle childhood and adolescent contextual and personal predictors of adult educational and occupational outcomes: A meditational model in two countries. Developmental Psychology, 42, 937-949.
[12] Miles, D. R., & Carey, G. (1997). Genetic and environmental architecture of human aggression. Journal of Personality and Social Psychology, 72, 207-217.
[13] Canadian Institute for Health Information (2008). Improving the Health of Canadians: Mental Health, Delinquency and Criminal Activity. Ottawa: CIHI.
[14] Martorell, G.A. & Bugental, D.B. (2006). Journal of Family Psychology, 20(4), 641-647.
[15] Jenkins, J., Keating, D. (1998). Risk and resilience in 6 and 10 year old children. Human Resources Development Canada. Accessed February 15, 2010.
[16] Offord, D., Bennet, K. (1994). Conduct disorder: Long-Term Outcomes and Intervention effectiveness. Journal of American Academic Child and Adolescent Psychiatry, 33(8), 1069-78.
[17] Cairns, R., Cairns, B., Gariépy, J., et al. (1988). Social networks and aggressive behaviour: peer support or peer rejection? Developmental Psychology. 24(6): 815-823.
[18] Hay, D., & Loeber, R. (1997). Key issues in the development of aggression and violence from childhood to early adulthood. Annual Review of Psychology. 48:371-410.
[19] Dishion, T., Patterson, G., Stoolmiller, M. & Skinner, M. (1991). Family, school, and behavioural antecedents to early adolescent involvement with antisocial peers. Developmental Psychology. 27:172-80.
[20] Keena, K. Loeber, R., Stouthhamer-Loeber, M. et al. (1995). The influence of deviant peers on the development of boys’ disruptive and delinquent behaviour: a temporal analysis. Developmental Psychopathology. 7:715-26.
[21] Feldman, J. & Kazdin, A. (1995) Parent management training for oppositional and conduct problem children. The Clinical Psychologist. 48(4): 3-5.
[22] Hartman, R., Stage, S. & Webster-Stratton, C. (2003). A growth curve analysis of parent training outcomes: examining the influence of child risk factors (inattention, impulsivity, and hyperactivity problems), parental and family risk factors. Journal of Child Psychology. 44(3): 338-398.
[23] Reid, M.J., Webster-Stratton, C. & Hammond, M. (2003) Follow up of children who received the Incredible Years intervention for oppositional defiant disorder: Maintenance and prediction of 2-year outcome. Behavior Therapy, 34, 471-491.
[24] Offord, D. & Bennet, K. (1994). Conduct disorder: Long-term outcomes and intervention effectiveness. Journal of American Academic Child and Adolescent Psychiatry, 33(8), 1069-78.
[25] van Lier, P. A. C., Muthén, B. O., van der Sar, R. M., & Crijnen, A. A. M. (2004). Preventing disruptive behaviour in elementary schoolchildren: Impact of a universal, classroom based intervention. Journal of Consulting and Clinical Psychology, 72, 467–478.