Research conducted at the Iowa State University has concluded that violent games can desensitize players to real-life violence. According to Nicholas Carnagey, an ISU psychology instructor who served as a research assistant on the study, "it appears that individuals who play violent video games habituate or 'get used to' all the violence and eventually become physiologically numb to it."
The results, although discouraging, are rather obvious. Violent movies and television have been known to desensitize people to actual violence, and now we know video games to be no different. What must be differentiated, however, is one's desensitization to violence and one's ability to cause violence. This study in no way correlates to the causality of violence.