The methodology Gray Area
People get awfully hung up on the learning quadrants like they are a good and evil, like it's black and white. They lose sight of the gray area. R+ trainers work hard to be choice focused, consent based, ethical and progressive, we try to avoid intentionally using aversives as a tool in our training. But life isn't all sparkles and rainbows as much as we would like it.
Let's look into those times that are more of a gray area...
The "cookie on top" method. When a trainer uses an aversive to stimulate behavior, to ask a horse to DO a behavior. The trainer doesn't escalate the aversive but maintaining it has an inherent escalation as the horse sorts out the puzzle. The aversive causes the behavior and when the horse does the desired behavior the aversive is relieved (this is R-!!!) Even if you add a treat after. Adding food to an R- trained behavior can sweeten the deal and help condition it as a more enjoyable experience, especially if the aversive is light and not too stressful. But we know that the aversive stimulated the behavior and it's removal reinforced it, thus it's R- with a cookie on top. This is some most carefully R+ trainers try to avoid doing because it runs the risk of poisoning the cue/behavior. When aversives mix into the equation, poisoning can happen. It can also reduce the value of the behavior for the learner, reducing choice and can easily overshadow emotions. This method is not wrong, evil, cruel, abusive, or anything like that, but it comes with risks that R+ without intentional aversives wouldn't have.
Then there is the "uncomfortable skill" which is the R+ shaping, targeting, capturing, method of training, but the horse has a natural aversion to the behavior being asked. Like a horse who finds movement difficult or standing still hard. We can break this skill into small approximations and build up the horse's comfort and confidence with a task they might find aversive. This is going to happen with every horse, there are going to be easy skills and hard skills. I always say "put your money on the hard stuff", reinforce the skills the horse dislikes more, while the skills they naturally enjoy need less external reinforcement.
Then there is counter conditioning and CC with a behavioral component. Counter conditioning has to Start with an aversive, though we try to be careful to stay as mild as possible and build in gentle approximations. This is where we introduce an aversive as mild as we can, then pair it with an appetitive. We do this repeatedly to change the conditioning of the stimulus, to swing it from aversive to appetitive by reconditioning it. Pairing repeatedly as we steadily increase the strength of the thing that was aversive. We will also take frequent breaks and removal of the aversive to allow the horse time to process and let down their stress hormones from the experience. If we kept increasing without pause or relief it would tip the scale to being too aversive and counter condition in the wrong direction, poisoning the appetitive.
We can add a behavioral component at times with counter conditioning too. Where we may ask the horse to target the stimulus, engage with it, or stand facing forward while the scary stimulus moves around the horse (clippers for example). In this case we are both counter conditioning by pairing, but also reinforcing a known behavior positively and negatively by also removing the scary stimulus periodically to allow them time to relax. Even if we stayed at very low levels of aversion and highly appetitive we will have to pause or stop to give the horse a break to process what they learned. Removal is present, aversives are present, but we are staying more firmly in the realm of counter conditioning with a slight behavioral component. We are also using the behavioral component as information. If we ask for a touch and they are slow or reluctant or don't touch it all the way, or if we cue stand but they still turn to face the scary thing, we see that conflict is still rather high, even if the horse appears happy and well involved in the training.
Life is not black and white. All quadrants are happening at all times, classical conditioning is happening at all times, whether we intend for it or not. We can stay firmly in the R+ side of training and still have times and places where aversives are part of the picture or slide in unintentionally.
Let's also not forget Tactile Cues. This is where we simply train a behavior with R+ shaping methods, capturing, targeting or shaping, then we add a non-aversive tactile cue. We dont use the tactile stimulus to elicit behavior (otherwise we'd know it was aversive). We add a non-aversive tactile as a cue to a finished behavior.