Physical aggression in toddlers not caused by frustration over language problems

Physical aggression in toddlers has been thought to be associated with the frustration caused by language problems, but a recent study by researchers at the University of Montreal shows that this isn't the case. The researchers did find, however, that parental behaviours may influence the development of an association between the two problems during early childhood. Frequent hitting, kicking, and a tendency to bite or push others are examples of physical aggression observed in toddlers.

"Since the 1940s, studies have observed an association between physical aggression problems and language problems among children and adolescents. It was also demonstrated around ten years ago that physical aggression problems arise in early childhood when language develops. We wanted to see if this physical aggression/language association existed in toddlers between 17 and 72 months, and if so, who influenced whom," said Lisa-Christine Girard, a postdoctoral researcher with the Research Unit on Children's Behaviour Problems (GRIP) and lead author of the study.

The team of researchers used a longitudinal study of 2,057 French- and English-speaking Quebec children recruited from the Quebec Longitudinal Study of Child Development (QLSCD), conducted by GRIP in association with Quebec's Ministry of Health and Social Services and the Québec Institute of Statistics. Parents were asked to evaluate the frequency of physical aggressions and the language abilities of their children at 17, 29, 41, 60, and 72 months. The parents' behaviours – punitive and affectionate behaviour – were also assessed.

The results of the research show an association between the frequency of physical aggressions and the quality of language development between 17 and 41 months. In fact, children who had low language skills at 17 months committed more acts of physical aggression at 29 months, and the frequency of this aggressive behaviour at 29 months was associated with lower language skills at 41 months. However, according to the researchers, this association was quite low, and the fact that it disappeared at 41 months could be explained by the fact that the 17-to-41-month period was marked by a significant development of language abilities and a high frequency of physical aggression. “Humans use physical aggression most often between 17 and 41 months", explained Richard E. Tremblay, a professor in the Departments of Psychology and Pediatrics at the Université de Montréal, who supervised Girard's research. "After this period, the vast majority of children have learned to use other means besides physical aggression to get what they want, which reduces the likelihood of an association between aggression and language delays in a representative population sample.”

Therefore, these findings from a large representative population sample suggest that aggressive behaviours in toddlers are not motivated by language delays, and vice-versa. “We must look elsewhere for an explanation. We know that genetic and neurological factors play a role in the development of these two types of behaviour,” said Tremblay.

However, the researchers also noted that during this period, affectionate parenting is associated with low aggression levels and good language development in the children. This observation may indicate that affectionate behaviours of parents can facilitate language learning and the learning of acceptable alternatives to physical aggression. However, it is also possible that low aggression levels and good language development in children encourage parents to be affectionate toward them.

"This study, which is the first longitudinal study to examine associations between physical aggression and language abilities throughout early childhood, is in line with our work on the development of children's physical aggression. It allowed us to look at what the problem was exactly, and when it appears during early childhood," said Tremblay. “Other studies during the first three years of life are necessary; in particular, to better understand the effects of parenting behaviour and genetics that may explain the association between physical aggression and language development.”