Leyens, J-P., & Parke, R. D. (1975). Aggressive slides can induce a weapons effect. European Journal of Social Psychology, 5 (2), 229-236.

Abstract:  Tested the relationship between the aggressive meaning of slides and the viewers’ behavior. Three sets of slides varying in their perceived aggressive content were shown to 53 undergraduates who had to choose the intensity of electric shocks they wanted to administer to a partner. Viewing a highly aggressive slide increased the aggressive behavior of the Ss who had been insulted. (French & German summaries) (PsycINFO Database Record (c) 2004 APA, all rights reserved)