Temperament dimensions of shyness and inhibitory control relate to how a child presents themselves socially in uncertain situations. Although prior research has found evidence linking temperament and aggression, little attention has been given to temperament dimensions of shyness and inhibitory control and the subtypes of aggressive behaviors. This distinction could be crucial as some children may be more likely to use aggression to interact with others due to their shy nature or may act react aggressively in situations that are unfamiliar. The goal of this study was to understand how the temperament dimensions of shyness and inhibitory control and gender are associated with reactive and proactive aggression among 4-year-old children using parent-report measures. 124 parents of 4-year-old children (M=4.4 years, SD = 3.22 months; 53% female; 79.03% White) reported their child’s temperament using the Short Version of the Children’s Behavior Questionnaire Shyness and Inhibitory Control subscales (Rothbart, Ahadi, Hershey, & Fisher, 2001). Additionally, parents completed the Proactive Reactive Aggression Questionnaire (Dodge & Coie, 1987). Participants were recruited from area preschools and organizations serving children and families. Multiple ordinary least squares regression analyses were used for hypothesis testing. Model A tested whether inhibitory control, shyness, gender, and the interactions between gender and shyness and between gender and inhibitory control predicted reactive aggression. Specifically, it was hypothesized that low inhibitory control, high shyness, and gender (boys) would demonstrate an increase in reactive aggression with the interactions between gender and shyness and gender and inhibitory control being exploratory with no formal predictions. Model B tested whether inhibitory control, shyness, gender, and the interactions between gender and shyness and between gender and inhibitory control predicted proactive aggression. No significant effects were expected for any of the variables or interactions in Model B. As predicted, results indicated that low inhibitory control significantly predicted an increase in reactive aggression, β = -2.249, t(122) = -5.567, p \u3c .001, yet shyness did not significantly predict an increase in reactive aggression, β = .353, t (122) = .119, p = .315, while the overall model explained a significant amount of variance, R2 = .229, p \u3c .001. The multiple regression model for reactive aggression explained a significant amount of variance, R2 = .310, p \u3c .001. Furthermore, low inhibitory control significantly predicted an increase in proactive aggression, β = -.949, t(122) = -4.087, p \u3c .001, whereas shyness did not significantly predict an increase in reactive aggression, β = -.018, t (122) = -.011, p = .950,. These findings provide important details about links between a child’s temperament and their displays of aggression
