I dont look at it as if the zombie is thinking. If they can "smell humans" and can hide there smell by rubbing zombie goo all over them. Maybe the zombie walked past RV and smelled human and looked for a lunch.
As for running and thinking I just thought it was reacting. Food took off and it chased it. It does seem that the fresher zombies are faster then the others which would kinda make sense.
I dont over think The Walking Dead much. Its a badass series and there are a ton of directions the series can take. I like the direction they are heading. The Farm and The Prison look like they may be in this season which could be a whole bunch of damn good shows.