Another study of violence and gaming details the importance of the case subjects

Although even the bivariate correlations between media violence and violent acts in our samples were very small, our results suggest that such small correlations can be understood through underlying personality variables such as trait aggressiveness, neuroticism and Agreeableness. As such, assuming a clear linear relationship, particularly of a causal nature, between media violence and violent acts may be mistaken. Unfortunately most prior research on media violence has failed to adequately consider intervening personality variables. - Study findings

If you don’t really know the people that are included in the study, it’s hard to say how their impacted by media in certain situations. Doing a 2 week study and then producing definitive results just isn’t fair to either side of the argument.

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