Personally I think computer games and violent behaviour/cognitive thought processes could perhaps show a correlation but I don't believe there is evidence of a causal link. It's important to stress how different correlation and causation are. I'll be surprised if people could execute the experimental design this question demands. Way too time consuming for too trivial a question in my opinion o:

I'll edit my post with more appropriate answers later, gotta go now. Good topic.

edit: lol hrae