Baseline autonomic nervous system arousal and physical and relational aggression in preschool: the moderating role of effortful control.

The current study investigates whether established associations between physical aggression and low autonomic nervous system arousal, as indexed by heart rate and blood pressure, also apply to the study of the development of relational aggression. Baseline heart rate and blood pressure were collected in two samples of preschoolers, and teachers reported on classroom physical and relational aggression. In Study 1, lower systolic and diastolic blood pressure were related to increased engagement in relational aggression among older preschoolers. In Study 2, lower heart rate and blood pressure predicted increased engagement in classroom physical and relational aggression concurrently and across a preschool year in some cases. Low baseline arousal-aggression associations were strongest for children with poorer self-regulation abilities, whereas high self-regulation appeared to protect children with low heart rate and blood pressure from engagement in aggressive classroom behavior. These findings suggest the utility of examining baseline physiological measures in the study of relational aggression as well as physical aggression. Implications for interventions targeted to physical and relational aggression in early childhood are discussed.