BAT is a systematic desensitization protocol that reinforces behavior as well. The core idea of BAT is to empower dogs to make better choices. This works for all sorts of reactivity issues, but let's look at BAT for a dog whose behavior indicates fear. For this dog, we would set up multiple situations where the dog can calmly look at the 'scary monster' (trigger) and decide that it is not a threat. We let the dog walk toward the trigger and then stop him just at the point where he begins to focus on it. Then we watch for behavior like turning the head away, turning the body, shaking off, etc.
It's not quite just that, however. There are head turns and there are head turns. There is a small head turn (head only) that seems to be a sort of way to assess the situation, "if I turn my head, what do you do?" and then there is the sort where the dog's body curves and the head turns, and you can tell that the dog is really 'done' looking and gathering information. Usually there is a big blink before this sort of turn.
One primary reinforcer in BAT is the confidence boost and relief that comes in the moment where the dog makes the choice to disengage with the trigger. At this point, the dog goes from "hey, dad, I want to check this out, I'm not sure about it" to "I've checked it out and it's not a threat, we can walk away." Because it is relief, this is a negative reinforcement.
Note: If "negative reinforcement" just gave you an ethical jolt, please really pay attention here...the simple fact that this is in a quadrant you avoid does not make this an inhumane process. It's time to think outside of the box and focus on empowerment. Allowing the dog to check something out and move away whenever he wants is NOT the same as an artificial, trainer-applied aversive like yelling at the dog, shock collars, choke chains, etc. We ask force-based trainers to reassess their ethics and have an open mind to consider adding new tools to their toolbox, so we should be ready to do the same.
Another primary reinforcer for the dog's behavior is the internal locus of control inherent in the process: "when I moved forward, dad let me check it out from a distance" (but darn, he stopped me before I got all the way to the point where I freak out) and "when I said we could/should go, I got to move away." Getting control is probably a positive reinforcement. (Behaviors reinforced: calmly checking out the trigger and also disengagement). At the moment the dog chooses to disengage, we mark. The marker, "Yes," is a conditioned reinforcer (aka secondary reinforcer) that indicates you'll be walking/jogging the dog away and praising. This is both positive and negative reinforcement and one of those consequences may be a more powerful reinforcer than the other. There are variations (mostly for walks) where you use treats after you walk away, so that adds some more positive reinforcement. It is also a chance for the dog to choose to check out the trigger again, following the natural approach/retreat cycle of a dog checking out something they are not sure about.
Throughout the process, it should feel like the dog is leading the dance, possibly with you asking from time to time, "do you want to try again?" and also saying "ok, that's close enough, please check it out from here." Sometimes the dog wants to go away, sometimes they want to go to the left or right. As long as he's not going to a place where he'd be over threshold, let him go there to reinforce the disengagement from the trigger. Of course none of the things that the dog or you says are in words, they are in body language. Your communication with your dog should be gentle and clear. For example, if you stop the dog, let the leash slide through your fingers a bit so that the stop is slow. Then release the leash pressure slowly so that the dog can stand on his own on a loose leash to assess the trigger.
The disengagement in the engage/disengage pattern is not necessarily a sign of stress, although it can be. It's possible that the dog is thinking, "I can't take it any more, I have to go away." But then you are probably too close. If you are working at the right distance, there is not avoidance in turning away, it's just that the dog is done checking out the trigger. In that case, being able to turn away after looking at the trigger is a sign of confidence: "I don't need to assess that trigger any more, I can turn my back on it and walk away." I think leaving any meeting with a new dog has some inherent stress in it, which means there is probably a feeling of relief in walking away. So yes, this has negative reinforcement. But that doesn't make it less humane than if we were to feed treats just after the dog sees the trigger. (It's the same trigger, you'd just be adding food and potentially giving the dog a reason to stay too close, creating internal conflict, plus taking away the chance to check out the trigger thoroughly.) With BAT, as you walk/jog away and praise the dog, there seems to be a feeling of joy, though it is not the type that you see when you play tug or feed treats. It's more of a quiet confidence, "I did it! Plus Dad's really happy, which is a nice bonus."
If we do see stress signs in BAT (yawn, tongue flick, avoidance etc.), we should honor those by encouraging the dog to walk away, taking a little break, and next time, not allowing the dog to get that close to the trigger. However, it's important to not interrupt the dog's process, so if you think the dog can self-soothe and get herself out of the situation without having a meltdown, then that's the better choice, because it's more empowering.
That's the key...the dog should feel empowered through this process, not repeatedly forced to face the scary monster. Allow the dog to learn, don't force anything.
* Note: I'm writing "dog" here, but this applies no matter what the species is - dogs, cats, pandas, horses, etc.