How exactly that tells you how to "quantify the social interactions of participants in the game so that future online games can build better environments," we have no idea, but we'll leave that to the experts. Basically, McCreery and his team are examining how people use and interact with others in the game to see how we project ourselves and our characters.
Eventually, he wants to do something "education or therapeutic" with the information, though that too is left pretty open. Virtual environments like World of Warcraft do definitely engender ties between players -- is it possible that those ties can be used in an academic or therapeutical setting? Definitely an interesting line of research.