We haven't really run into as many "smart ones" as say Skittles have. I think a trip to a hospital or library is in order to fully investigate that side of the zombies. Riley mentions they were being surrounded on their last trip to a hospital, I believe. Maybe the "smart ones" out there each have there own "troop" of followers and they evolve differently. Or maybe there are other zombies like the one with the markings, that are on the same level, strength and intelligence wise.

Another theory I had was maybe people who where in a hospital setting react to the virus differently, ie...cancer patients with radiation treatments turned into something else.... just a though. And yes these thoughts will continue to get crazier till a new episode comes out.