The development of individual physically aggressive behaviors from infancy to toddlerhood.

Abstract

In the present investigation, we studied the development of six physically aggressive behaviors in infancy and toddlerhood, posing three questions (1) How do the prevalences of individual physically aggressive behaviors change from 8, 15, and 24 months? (2) Are there groups of children who show distinctive patterns in the way individual physically aggressive behaviors develop over time? (3) What are the behavioral pathways leading from 8-to 24-month acts of physical aggression? Mothers and fathers (N = 272) from a moderately at-risk population reported on their children's physical aggression at each time point. The results revealed the commonality of physical aggression at all ages studied and the diverging developmental patterns of individual behaviors. Some physically aggressive behaviors became less common (e.g., hair pulling), while others became more common (e.g., hitting), with age. Roughly 42% of the children exhibited an increased propensity, relative to their peers, to aggress at all ages. Kicking, biting, hair pulling, and pinching/scratching at 8 months were the first steps on behavioral pathways leading to physical aggression at 24 months.These pathways principally suggested heterotypic continuity in physical aggression.Keywords: physical aggression, infancy, toddlerhood, longitudinal, development. Development of Physical Aggression 3The Development of Individual Physically Aggressive Behaviors from Infancy to Toddlerhood Nearly all children are thought to exhibit at least some form of physical aggression in the first few years of life (Hay, 2005;Tremblay & Nagin, 2005). Physical aggression is known to be particularly common in toddlerhood (Hay, 2005;Tremblay & Nagin, 2005; Naerde, Ogden, Janson, & Daae Zachrisson, 2014) -exemplified by the so called "terrible twos." Yet a growing body of research has shown that these behaviors are common prior to age 2 Naerde et al., 2014), having been reported in children as young as 6 to 8 months of age (Hay et al., 2010;Lorber, Del Vecchio, & Slep, 2015). The present report is a continuation of this new wave of research in which we probe the development of physical aggression between 8 and 24 months. Tremblay and Côté (2005) argued that "[t]aking a developmental perspective means, first, to understand the development (change over time) of the phenomenon we are trying to predict, and second, to describe the causal chain of events over time that explain the development" (p. 449). In this spirit, we investigated which aggressive behaviors develop when, and in whom, and identified behavioral pathways leading from physical aggression at 8 months to physical aggression at 24 months.At the outset, it is important to clarify our approach to the phenomenon of aggression in the early months of life. As pointed out by several writers (Hay, 2016;Lorber, Del Vecchio, & Slep, 2014;Tremblay, 2000), there is disagreement about whether it is appropriate to refer any behavior as "aggressive" when performed by infants. Some theorists prefer a definition of aggression tha...

Normative Trends in Physically Aggressive Behavior: Age-Aggression Curves from 6 to 24 Months

“…The findings on the prevalences of hitting and pushing people were consistent with previous research, as were the year 2 findings on kicking people. 6,7 However, the year 1 increase in the prevalence of kicking stood in contrast to previous findings indicating a slight decrease between 8 and 15 months. 7 Yet not all physically aggressive behaviors increased with age.…”

“…6,7 However, the year 1 increase in the prevalence of kicking stood in contrast to previous findings indicating a slight decrease between 8 and 15 months. 7 Yet not all physically aggressive behaviors increased with age. Hair pulling, in particular, exhibited pronounced decreases in prevalence and frequency.…”

“…This was the most common behavior at 6 months, reminiscent of the findings reported in 2 previous studies at 6 and 8 months. 5,7 As in the study reported by Lorber et al, hair pulling also became much less prevalent with age, as predicted. 7 Among children who pull others' hair, the behavior became less frequent as well, dropping from nearly 4-6 days a week at 6 months to nearly 1-3 days a week at 24 months.…”

“…5,7 As in the study reported by Lorber et al, hair pulling also became much less prevalent with age, as predicted. 7 Among children who pull others' hair, the behavior became less frequent as well, dropping from nearly 4-6 days a week at 6 months to nearly 1-3 days a week at 24 months. As predicted, scratching people decreased in frequency as well, although less dramatically than hair pulling.…”

“…17 Thus, our default prediction was increases in both the prevalence and the frequency of most physically aggressive behaviors. However, we tempered those predictions with the available evidence suggesting decreases in hair pulling and combined pinching/scratching, 7 as well as curvilinear trends in hitting, kicking, and biting. 6,7…”