So they picked people with little to no experience playing "violent video games" for this study. Had they had extensive exposure to other types of video games, just CHOSE not to play FPS titles? Choosing a bunch of non-gamers, and having them play video games 2-3 hours a day when they previously didn't play games will likely result in SOME kind of change in their brain activity. Whether that activity is positive or negative is a completely different question. Repeat this study with a random sample of gamers and non-gamers included, and see if the effects are the same on people who had done extensive game playing previously would be a good place to start.