Impulsive aggression (IA) refers to a behavioural response that inflicts physical or emotional damage to the self, other individuals, or objects. Control of IA is often attributed to response inhibition (RI), which refers to the ability to suppress inappropriate actions. RI deficits have been linked with various psychopathological disorders and behavioral problems, including IA. Furthermore, IA is influenced by early-life (pre- and post-natal) environment, and it has been said that RI mediates this link. Yet, most studies focusing on RI and IA are correlational, so it remains to be determined whether RI deficits lead to IA or whether both RI and AI are merely influenced by a common underlying factor. Additionally, few studies have established a causal effect of early-life environmental factors on RI and IA. In this project, I will use the Japanese quail, an animal model widely used in neurobiology and behavioural ecology. I will first establish the relationship between an individual’s RI and AI, and second, determine how 1) early-life social and physical environment and 2) prenatal stress influence the development of IA, with the prediction that RI will mediate this link. Overall, this project will use an innovative approach to address gaps in the RI and IA literatures and provide new insights on why individuals differ in their ability to control their behaviour.