Geen, R. G. (1975). The meaning of observed violence: Real vs. fictional violence and consequent effects on aggression and emotional arousal. Journal of Research in Personality, 9 (4), 270-281.

Abstract:  Sixty male undergraduates were either attacked or treated neutrally by a confederate, after which each saw a videotape of 2 men fighting. Ss were informed that the fight was either real or fictitious or were given no explanation of it. Ss who had previously been attacked and had observed the fight under a set to perceive it as real were subsequently more punitive in their treatment of the confederate than Ss in all other conditions. The combination of prior attack and observation of real violence also sustained blood pressure (BP) at near the level produced by the attack, whereas BP of attacked Ss in the other conditions declined during the time the fight was observed. Palmar sweat measures revealed that observation of real violence was more arousing than observation of fictitious fighting. Results are discussed in terms of the effects that the reality of observed violence has on emotional arousal. (29 ref) (PsycINFO Database Record (c) 2004 APA, all rights reserved)