Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
I think the kid learned the reverse bike faster because it has little experience on using the normal bike, unlike adults who have been biking all their lives the normal way. Just like the saying goes "you can't teach an old dog new tricks", because it is so used to do one thing on a certain way, it will have a hard time adjusting.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.