Average, who can say. Modal, by number of contributions/edits, they absolutely are more motivated than a PhD. They may have spent their life studying a topic but Wikipedia isn't where they're generally going to put it.
If your counting by number of edits that's basically a tautology:
People who edit wikipedia make more edits than people who don't edit Wikipedia. Well no shit.
If you want to do an apples to apples comparison, compare how many hours people edit wikipedia vs how many hours PhD candidates spend writing their dissertation. i think on average traditional accademia rewards obsessiveness much more than wikipedia does.
