Developmental Trajectories of Physical Aggression in Low-Income African American and Hispanic Children: Relations to Household Risk and Child Inhibitory Control

This dissertation examined developmental trajectories of physical aggression in low-income African American and Hispanic preschoolers as they transitioned to primary school. Three developmental trajectories were expected to be identified in the data: a low physical aggression group, a group that begins higher in physical aggression that the low group but declines to near zero levels by Wave 4, and a group high in physical aggression across all four time points. More boys and African American children were expected to be classified into the high physical aggression group whereas children with higher inhibitory control competency were expected to be classified into the low physical aggression group. Additionally, cumulative risk was measured at all four time points and more cumulative risk was expected to be characteristic of the high physical aggression group. Data from the Dallas Preschool Readiness Project (DPReP), a longitudinal study of 407 low-income African American and Hispanic children and families, were used to estimate developmental trajectories across four waves beginning when the children were 2½ years of age. Additional waves were included when children were 3½, in kindergarten, and in first grade. Using group-based trajectory modeling, a model consisting of four trajectories of physical aggression was selected. The model identified a no physical aggression group (18%), a low declining group (41%), a high declining group (32%), and a high chronic group (9%). The groups did not differ by child gender but more Hispanic children were classified into the no physical aggression and low declining groups while more African American children were classified into high declining and high chronic groups. To gain a better understanding of the trajectories, cumulative risk and inhibitory control were modeled as predictors of physical aggression group membership but in different ways. Cumulative risk was modeled as a time-varying covariate of physical aggression and showed to distinguish the low declining and no physical aggression groups from high chronic and high declining physical aggression groups. Higher levels of cumulative risk characterized the high chronic physical aggression group and lower cumulative risk characterized the no and low declining physical aggression groups. Inhibitory control at Wave 2 when children were 3½ distinguished the no physical aggression from the low declining and high chronic groups. No differences related to cumulative risk or inhibitory control were found between the high chronic and high declining groups. This study extends extant research on the developmental course of physical aggression at these early ages by examining individual differences related to variations in risk and inhibitory control within a high-risk sample of ethnic minority children. Most of the prior research investigating physical aggression in young children has included predominantly middle-income, Caucasian samples. The current study addressed the unanswered question of whether the developmental course of physical aggression in very young, low-income, African American and Hispanic children is similar to that found in Caucasian-majority samples in prior studies. The findings reported here show substantial within-group variability in physical aggression in low-income African American and Hispanic children. The current study findings appear to indicate consistency with prior research. That is, distinct high chronic, high declining, low declining and no physical aggression groups were identified from the analysis, with significant between group differences between the extreme groups. Inconsistencies with past research are discussed at length.