The Indiana University School of Medicine in Indianapolis study compared Need for Speed: Underground and Medal of Honor: Frontline. Kids played the games, then, using a fancy MRI machine, blood-flow was measured to parts of their brains while they performed simple tasks. The study tested only 44 subjects, so it may point to significant results, but it also needs to be repeated with bigger groups.
While we might have picked a different non-violent game -- we always crash our NFS cars, and that seems pretty violent -- we hope that this sort of research is also applied to other media before drawing conclusions. If violent games cause kids to go into fight-or-flight mode as the study suggests, can this be linked to real-world reactions or long-term changes? How do kids' responses to movies compare to games?
[Thanks to everyone who sent this in.]