One of them being that he completely ignored the influences of learning and cultural factors that can affect aggression and instead focused only on biological factors. Cultural differences have been shown to play a very important role in determining the acceptability of the degree and types of aggression. Siann (1985) also criticized Lorenze's theory because he believed that humans are naturally "hunter-gatherers" who rarely come into contact with others rather than "warriors" as suggested. Lea (1984) also refuted Lorenze's claim that nonhuman aggression ends before an animal of the same species is killed, pointing to cases such as where a lion takes control of a new troop and kills the young males. Another theory surrounding aggression is social learning theory, which proposes that "aggressive behavior is learned through reinforcement and imitation of aggressive models." (Bandura, 1965, P.501) Social learning theorists do not view aggression as innate, but rather believe that it is solely a learned behavior. Humans learn aggressive behaviors by observing others behave aggressively. They observe in which situations aggressive behavior is rewarded (vicarious reinforcement) and when it is punished and thus learn which aggressive behaviors they can imitate to be rewarded and which not to repeat so as not to be