When puppies are little, everything is pretty cute and small and easy; walks, retrieves and a few manners.  As they begin to grow up, they aren't old enough for formal training, but they are beginning to know what they are doing, like running puppy marks and hunting live birds.  It is at this stage we often jump ahead before the pup is really ready, with whoa, electric collar, force fetch, etc.  Instead, teaching the growing dogs to learn to take responsibility for doing the work you are teaching them, to take the work seriously and to focus on it, allows for the upcoming formal training to be much easier and more clearly understood.