Berkowitz, L. (1970). The contagion of violence: An S-R mediational analysis of some effects of observed aggression. Nebraska Symposium on Motivation, 18, 95-135.

Abstract:  Aggressive crimes (mass murders, urban riots, bombings, etc.) across the country show an impressive rise following publication by the mass media of a violent crime. Tv has come in for a great share of the blame, however, epidemics of crime are cited as having followed “the line of the telegraph” since the time of jack the ripper. Impulsive, violent, and injurious actions are automatic reactions preceded by a minimum of thought making “man more like the lower animals than he is otherwise.” contact sports, identification with movie characters, and the reinforcing qualities (pleasantness felt) of aggression are also discussed. (45 ref.) (PsycINFO Database Record (c) 2004 APA, all rights reserved)