My dogs are pretty much the epitome of self-confident, yet I still don't use corrections (save a verbal "uh-uh" or "no" for redirection). I think it might be a *bit* over the line to make a blanket statement that corrections will only improve the performance of a high-confidence dog. I haven't found this to be true with my dogs, and they lack nothing in the confidence department.
I wouldn't even THINK of using a Shiba in a breeding program that didn't believe the world revolved around it. At 6 months of age Kimi had adult Golden Retrievers and Malamutes alike rolling over on to their backs in submission to her, LOL. By 6 and a half months she had confronted her first adult male pig, and was already displaying the "spirited boldness" the breed standard demands. She hit the end of her lead, stood "like a little Mt. Fuji," and stared him right in the eye. She didn't move until I picked her up. It was quite a sight indeed- this tiny little puppy, ready to take on a pig weighing at least 400 lbs! She is an alpha bitch in every sense of the word.
In all honesty, most people in Shibas will tell you that they wish their dogs had a little *less* self confidence. I know quite a few breeders who owned both Shibas and Akitas, who have switched to one breed or the other after losing an over-confident Shiba to an Akita in a fight.
Shibas tend to be clever to an absolutely wicked degree. Many people will tell you that they border on cunning. But in the same turn, they won't stand for any sort of traditional correction- you immediately lose all respect in their eyes, and they shut down. (I experienced this first-hand with my first Shiba, and we changed methods FAST).
Thus, I don't bother with traditional corrections, but perhaps this has a lot to do with *breed* characterstics. Since my first experience with Tai, I haven't been to another class that uses correction-based training, so I honestly wouldn't be too qualified in giving an opinion on its effectiveness in agility. I have personally liked what I've seen come out of the positive-reinforcement classes though.
At any rate (and all semantics aside), the most important thing is to find a method that works for you and your dog, and having fun while doing it! Not every method works for everyone, and this of course is something that I (and probably a great deal of us at Chaz!
) could stand to remember!