These results shouldn't be dissmissed so readily. One of the studies was scientific in nature with control groups, random assignment, the whole schebang. I don't know what they did as far as statistical analysis, but it is possible to control for a lot of things (although its also possible to get stats to say a lot of different things depending on what is controlled for).
Its important to note what these studies are and are not saying. No one is saying that if you play violent video games you are going to go out and kill people. What they are saying is that playing such games will likely make you more aggressive than you otherwise would be. There are clearly numerous other factors that also affect one's level of aggressiveness, and video games are probably not one of the larger ones.
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