My daughter linked this finding to me last night: World of Warcraft Improves Cognitive Ability for Older Adults.  I couldn’t reconstruct the original link, but google pulled up an aggregated feed of a lot of places reporting on this result:

http://newsfeedresearcher.com/data/articles_m9/game-study-cognitive.html

The source lab looks to be doing some interesting stuff: http://www.gainsthroughgaming.org/index.html

The published report isn’t quite officially out yet (I think this link goes to a corrected proof): http://www.sciencedirect.com/science/article/pii/S0747563212000143

Some things to note — participants were 60-77 years old, played 14 hours of game play and only the lowest scoring participants exhibited reliable gains.  (Bonus statistical question — why would this raise some concerns about the reliability of the result?).  Looks like you can get a lot of media attention even for not quite totally awesome data in this area.  It’s probably deserved since it’s probably a real effect.  I suspect you’d want a bit more time in-game to see something more robust and I don’t see a real measure of “processing speed” in their assessments.

One additional thing to note — this is actually a hard study to pull off.  Getting ~40 adults in this age range to play WoW for a decent chunk of hours reflects a significant amount of work just in logistics and recruiting.  I think these gaming studies look easy from the outside, but when you try to run a training study of course you realize it’s not.