Is there any evidence that adding real names to a previously anonymous service substantially increases level of civility?

Note that I'm specifically excluding sites like Facebook and LinkedIn that required real names from the start. I suspect it's a matter of whether users think of the site as being relevant to their personal identity. I'd even be willing to hypothesize that a random sample of Hacker News users considers HN more "real life" than a random sample of YouTube commenters who had g+ accounts crammed down their throats.