Recently in class we have discussed the impact of violent television shows and violent video games on young developing minds.
This link will bring you to an article discussing the topic of violent video games and their effect on adolescents. The article says that repeated violent actions on the game acts as a reinforcer, causing the adolescent to be more prone to be aggressive. The article also discusses that by playing "first-person" games, the adolescent begins to think like the character they are controlling and therefore they become more aggressive.
The article makes valid points. A child playing a first person shooter gets to feel like they are character. Whatever decisions they make cause the player either harm or reward. Because of this, if in the game the child causes harm to someone, but is rewarded because of it, if he/she is faced with a similar situation in real life, they may decide to cause harm again because they believe it will bring reward.
Although there are many studies showing that aggression and time spent playing video games go hand in hand, these results are merely correlational. The correlation vs causation scientific principle tells us that although these two things are correlated, it does not mean that video games cause aggression.