Knapp, H. (2002). Desensitization aftereffects of playing violent videogames. (Doctoral dissertation, University of California at Los Angeles, 2002). Dissertation Abstracts International, 63 (5-A), 1997.

Abstract:  Purpose. The goal of this investigation was to measure the extent to which playing a violent videogame affects the way that adults perceive real-life aggression. Hypotheses. It was hypothesized that participants who were initially exposed to a violent videogame would be desensitized to aggressive behavior and hence might hesitate longer before intervening in (what appears to be) a real-life escalating physical confrontation, than participants who played a nonviolent videogame, and (presumably) experienced no such desensitization. Methods. Forty adult males (18 years or older) were recruited and tested individually. Each participant was randomly assigned to play either a violent or a nonviolent videogame for 15 minutes followed by observing what appeared to be a live video feed of an escalating physical confrontation between two young boys. Participants were instructed to push an intercom button to have an adult intervene should the children start to “get into it” with each other. Findings. Overall, participants pressed the intercom button within a 90 second window. An analysis of variance (ANOVA) computation revealed a statistically significant difference (p = .006) between the two groups response times: participants who played the violent videogame responded (on the average) 18 seconds later than those who were exposed to the nonviolent videogame. Implications. These findings suggest that playing a violent videogame alters the way that adults perceive real-life violence. This may serve as a disinhibitory factor, thereby propagating an elevated potential for (real-life) aggressive behavior in such individuals. (PsycINFO Database Record (c) 2004 APA, all rights reserved)