the Amgydala is the structure in the limbic system that is most closely associated with aggression and attack behavior.
As the main part in our body that control our fear, Amygdala also the control our 'fight or flight' response.
When we see a threat, our brain will quickly assess the situation to decide whether we should face the threat head on ( which led to aggression and attack behavior.) or we should just run away because it is too dangerous.
