The Early Childhood Aggression Curve: Development of Physical Aggression in 10- to 50-Month-Old Children


  • This study is part of the research project “Screening and Intervention of Problem Behavior in Toddlerhood” (SCRIPT), conducted at the Centre for Child and Family Studies, Leiden University, the Netherlands. The study is supported by grant 2200.0097 from the Netherlands Organisation for Health Research and Development (Zorgonderzoek Nederland) to Marinus H. van IJzendoorn and Femmie Juffer.
    We thank the parents and children who participated for their contributions to this study. We are also grateful to Elise Dusseldorp for her advice on statistical analyses.

concerning this article should be addressed to J. Mesman, Centre for Child and Family Studies, Leiden University, P.O. Box 9500, 2300 RB, Leiden, the Netherlands. Electronic mail may be sent to


This study examines the prevalence, stability, and development of physical aggression, as reported by mothers and fathers, in a sample of children initially recruited at 12, 24, and 36 months (N=2,253) and in a subsample followed up 1 year later (n=271) in a cross-sequential design. Physical aggression occurred in 12-month-olds, but significantly more often in 24- and 36-month-olds. The rates of physically aggressive behaviors increased in the 2nd year of life, and declined from the 3rd birthday onward. Stabilities were moderate for 12-month-olds and high for 24- and 36-month-olds. At the ages of 24 and 36 months, boys were more aggressive than girls. The results confirm and extend R.E. Tremblay's (2004) hypothesis about the early development of physical aggression.