Two different schools of thought exist among those who view aggression as instinct. One
group holds the view that aggression can build up spontaneously, with or without outside
provocation, and violent behavior will thus result, perhaps as a result of little or no provocation.
Another suggests that aggression is indeed an instinctive response but that, rather than
occurring spontaneously and without provocation, it is a direct response to provocation from an
outside source.
instinct common to humans.