How Video Games are Good for the Brain, on the Boston Globe site
"Video games are hard,'' said Eric Klopfer, the director of MIT's Education Arcade, which studies and develops educational video games. "People don't like to play easy games, and games have figured out a way to encourage players to persist at solving challenging problems.''
The games aren't just hard - they're adaptively hard. They tend to challenge people right at the edge of their abilities; as players get better and score more points, they move up to more demanding levels of play. This adaptive challenge is "stunningly powerful'' for learning, said John Gabrieli, a neuroscientist at MIT.