There is a real answer to this? I think that if a person were in that situation, they would hardly have the time, or the steady mind to truly analyze it and make the "right" choice. However, there are many things that could come into play. Some would say to stay with door 2 because that’s the first one you picked; therefore, subconsciously you’ve made the right choice. But what if the producers of the show had arranged the prizes in ascending order? That would mean that the donkey would be 2, and the car 3. Also, statistically speaking, don’t most people choose the middle of most things automatically? Having something to do with our brains attraction to proportionate things? That might also make the shows producers put the "joke" prize behind the most likely to be picked doors.
Probably wrong, but it feels ooohhhh so right.