Riddle 6 - Numbers numbers...

And here we go again - another riddle.

But first - what's the solution to the last riddle http://omer-behindthelines.blogspot.com/2008/08/riddle-5-doorway-to-heaven.html? The answer is that you should always pick the door that was left behind and not the door you originally picked. This is because there was a 33% chance for you to be right in the first place, meaning that there was a 66% that the right door is one of the other two doors. Since the gnome has helped you to throw away one of these two doors, all the 66% chance went to the door he left behind. So there is a bigger chance that that door is the correct one.

Riddle 6 - what is the next number?
Look carefully at the following list of numbers and please write down the next one to follow:
1
1 1
2 1
1 2 1 1
3 1 1 2
1 3 2 1 1 2
3 1 1 3 2 2
2 3 2 1 2 2
4 2 1 3 1 1
1 4 1 2 3 1 1 3
???

One small hint - no need for mathematics at all, a 8 year old kid can solve this...