DD1 at the age of 3/4 fine no problems.
DD1 now 14 almost 15 does listen and will take punishment but will challenge us every step of the way! but then thats teenagers I guess!
On the other hand DD3 fantastically easy baby (well and truly) Ok as a toddler too, but she has turned into at times a right little madame! We often have to remind her that she is not the only child in family etc! She is 8!
We have not brought them up any differently!