I don't think they make you more violent, but I do think they condition you to expect a certain reward for a certain input. In that sense what they're priming your brain for is an exploitable addiction cycle. I used to play online first person shooting games all the time, but lately I've noticed that I'm playing them just for the sake of playing them. I'm no longer deriving any enjoyment from the activity; in a sense I feel like a conditioned rat inside a maze. The final sensation isn't one of fulfillment but rather one of helpless attachment.

Contrast that with another game I played recently, God of War. That game ended after about 30-40 hours. I completed the story, and I never returned to it. When I think back on it, I have a lot of satisfaction attached to it. It was a wonderfully told story that eventually ended, whereas Call of Duty is designed to be an infinite time sink, both for your attention and for your wallet. The difference, for me, is playing basketball with your friends versus going to a slot machine.