In the last week I've been drunk in a strip club, got shot at by gangsters and driven a sports car into the ocean — where, regretfully, my partner drowned. But that's nothing compared to a friend of mine who has robbed a convenience store at gunpoint and broken into a military air base — then stolen a jet aircraft.

I am of course speaking of the megahit video game "Grand Theft Auto V" ("GTAV"), whose British designers, Rockstar, have created the biggest interactive environment — the largest "open world," in the jargon — ever seen in a video game. It's a compelling, beautifully rendered — and addictive — experience. But has the act of playing it changed my brain? Am I already more violent and evil than I was before? That's what I want to explore this month.

As I write, "GTAV" has just been released in Japan, more than a month later than in most of the rest of the world. The venerable Japanese video-game magazine, Famitsu, has awarded "GTAV" a perfect 40/40 score in its review — only the second game from overseas accorded that honor. That's quite a big deal in Japan, where fantasy and role- play adventures tend to dominate the market, and foreign games, even big-budget ones, make little impact.