Physical aggression occurs already at age of twelve months and although most children learn to regulate their behavior, in some children the aggressive behavior exists until adulthood. Little is...Show morePhysical aggression occurs already at age of twelve months and although most children learn to regulate their behavior, in some children the aggressive behavior exists until adulthood. Little is known about the causes of persistence of aggressive behavior in children. Some studies with mostly older participants found a correlation with stress reactivity. Therefore in this study the correlation between physiological response (pre-ejection period and heart rate), behavioral response (intensity of facial fear, intensity of distress vocalizations and intensity of bodily fear) and self-regulation (self/object engagement and attention to the researcher) will be examined in relation to aggressive behavior in twelve-months-old children (N = 71). Mother and child visited the Leiden University and child’s behavior during the Fear task, a stressful task in which a robot enters the room and walks to the child while the child sits in a seat, was video-taped. Child’s physiology was recorded with the help of the Vrije Universiteit Ambulatory Monitoring System (VU-AMS). Mothers filled out the Cardiff Infant Contentiousness Scale (CICS) and The Physical Aggression Scale for Early Childhood (PASEC) for measuring the degree of aggressive behavior. A significant positive correlation between heart rate and behavior response was found. No significant correlation was found between pre-ejection period and behavioral response, nor between physiology, behavioral response and self-regulation. Aggressive behavior couldn’t be forecasted by physiology, behavioral response and self-regulation. These results are discussed en recommendations are done in context of further research on stress reactivity, development of self-regulation and aggression.Show less