Judi, you got it! (per usual

) Dogs must be started from Day 1 to understand that they initiate the game. Our helper does not use whips until MUCH later in training, a new dog won't see one for years. The dog must bring the fight to the game, not sit around and wait to be antagonized by the whip. Bark = mvmt = bite is basically what it comes down to, and yes, the helper IS motionless in the blind during training. None of that making prey attraction with the sleeve while the handler holds the dog back.
Also, it is not any movement that = bite, it is threatening movement. We used to do an exercise where Kenny would work outside the blind, but back up, or basically wander around backwards with the dog in a B/H. There was no threat presented, no bite allowed. The dog would just maintain that tight B/H in the pocket. Another exercise we worked on to improve obedience was free heeling with the helper on the field and walking back and forth past him. Again, the helper is moving around, but no bites are allowed.
As to barking without a sleeve, it's all what's in your dog's heart. Some are very convincing at it because they truly want the fight, (the man) and could care less about the sleeve, others........well, they like the sleeve game. Interesting test: put the dog on a long line, helper is out of reach working the dog like a young dog: building attraction. Then have the helper suddenly toss the sleeve away. Where does the dog's focus go? Most will look to the sleeve, some will return from it, others will just focus their attention/barking on the sleeve. A very few will not even blink and never waver focus from the helper. Tells you a lot about what's in a dog's heart and what their focus in training is.
Froli barking at the cheese as a young puppy was not prey drive. What prey attraction does a lump of cheese present? Going back to Bernhard's question, what function would barking at prey serve? "I'm going to bark at this rabbit and it will come to me!"

Doubt it. Barking is not a prey drive action. It comes from either frustration or aggression. Most dogs, it is frustration. I have a dog who does not bark out of frustration. She is one of the most confident dogs many have ever met and seems to have endlessly long nerve. When her B/H is taught (if my helper is ever available on a regular basis again

), it will have to be done out of active aggression. It's a very serious undertaking, a rare one and something that has to be done right the first time, or someone's gonna get bit (not me!). This is not the same as doing civil work, but it is teaching her to basically show aggression to a passive subject and that MUST be done correctly. I will not even get into it here, it's not an internet subject.
Another way to really blow a sleeve-dog's mind is to present a helper with two sleeves. HOLY COW! Some don't know what to do with it, others will work through it fine. The dog who truly wants the fight simply barks up over both of them.
Remember this above all else in SchH training: you can teach many behaviours, but under stress (read: trial conditions), the dog will revert back to what it truly is and you may see behaviours that aren't as common in training (when things are more calm, including the handler's nerves).
Froli was a girl who loved the fight. I took her to Philly for her SchH2 and we took the field without ever having warmed up on the field or the helper having worked her. I warned the helper (Mark Stathopolus, used to handle Natl level dog Ecks) that she would come right in his face. Mark is 6'3" and probably had heard that one before. Her first two barks (before I was called into the blind by the judge) were literally bark/clack an inch from his nose.

That's just who she was, always wanting to bully new helpers and see if she could make 'em flinch. I miss that girlie!