I have a 9 month old lab that I am casually training. She is more of a companion but has a strong desire to retrieve and learn. I am using Dokken's book but haven't been religious in following it step-by-step (clearly creating learning gaps).
She marks and casts just fine as long as the dummy is in sight. However if it's blind she will only go a short distance before she begins to hunt. What training exercises can I do to get her to continue on a line even when she doesn't see the dummy?