But from what I can tell, you can't say much more about this study than that people aren't as excited before and after playing WoW as they are while playing it. And it doesn't really take you a behavioral scientist to figure that out -- there's no way that taking a quiz given by some scientist is as exciting as, say, traversing the wastelands of the Barrens, or flying around Netherstorm.
Some people have taken this as a sign that the game somehow lets you chill out or makes you less angry than other gamers or people, which may be true, but that's not what's being said here. As far as I can tell, they're just saying that you're not as excited after playing the game as you are during. Maybe this will lead to something else, but as a finding, that's not exactly a groundshaker.