Is aggression learned or innate?
Aggression is an innate instinct. It is part of the "Fight or Flight" response to an external threat.
Specific aggressive behaviors may be learned, and even reinforced. But the aggressive tendency in humans is an innate characteristic. Constructive methods of dealing with threats and stresses need to be taught to people from an early (childhood) age to avoid later, deeper patterns of aggression in adulthood.