You have a 15-year-old son who likes to play video games. He’s a high achiever in school who appears socially well adjusted. He doesn’t wear Goth clothing or otherwise act in ways that might alert you to a behavioral problem, so you haven’t paid much attention to his gaming because it seems like a harmless diversion.

One Saturday afternoon, you’re in his room and notice he left a game running on his computer. You’re curious, so you pick up the controls, hit the start button and sit down to see what all this is about. The game is called Postal II, and here’s what happens when you begin to play: The central character has “gone postal” and decided to kill everyone he encounters. This includes armed opponents, such as police, and unarmed people, such as schoolgirls. Girls attacked with a shovel will beg for mercy; the player can be merciless and decapitate them. People shot in the leg will fall down and crawl; the player can then pour gasoline over them, set them on fire, and urinate on them. You quickly get the picture.