Geen, R. G., & Stonner, D. (1973). Context effects in observed violence. Journal of Personality and Social Psychology, 25 (1), 145-150.

Abstract:  After 1st being attacked or treated in a neutral way by a confederate, 60 male undergraduates completed mood-rating scales and watched a movie of a prizefight. Ss were (a) told that the fight was motivated by a quest for vengeance, (b) told that the fighters were boxing for money as professionals, or (c) shown the film without comment. Ss were then given the opportunity to administer “shock” of varying intensities to the confederate for wrong responses on a learning task and were retested on the mood scale. Results show previously-attacked Ss tended to be more aggressive and express lower restraints against violence after witnessing vengeful aggression than after seeing identical violence described as professional. Nonattacked Ss were more aggressive and less restrained after observing professional violence than after seeing revenge. Results indicate that interpretations placed on observed violence affect aggressive behavior in the O by raising and lowering inhibitions against aggression. (PsycINFO Database Record (c) 2004 APA, all rights reserved)