Great thread! I don't have really anything new to add to it, but I do have a question. Both my dogs are what I would term "reactive" while on lead and behind a barrier, though they go about it different ways.
Sawyer, my Aussie (around 4 years old and neutered), is quite "reactive" around small-dogs on lead. After a careful thinking over and observation, it is my belief that his reactiveness is borne out of prior experience--he's got a decent dominent streak to him and since stupid people love Flexi-leads around here, he's gotten many small dogs come flying/jumping into his face. That's his biggest pet peeve. So now when we see a small dog on a lead (esp. a Flexi), he will start to growl/bark/posture and attempt to charge. If he does charge, he does not bite but he will back the dog up and make it quite clear what his feelings are, then walk away. I obviously try to not allow this, but he's got a vendetta against a beagle that lives here and occassionally that beagle will be at the bottom of the stairs outside while I'm coming out. Between my two dogs and downward gravity, unless I want to severly face-plant, I just kind of have to go with it until my feet can hit level ground and get them back under control. This beagle also has zero leash manners and can usually be found straining on his back legs at the end of it, which I have found is a trigger to Sawyer's "Mr. Manners' OCD". With the exception of this beagle and a certain JRT that also lives around here, Sawyer is completely calm when off-leash and will approach with proper greeting habits, which usually ends in a sniffing and walking off (unless the dog is very submissive, then he delights in barking and watching them hit the deck. Jerk.
) However, he is completely calm when walking around Petsmart and generally just gives off "leave me alone, I'm not looking at you" signals to the other dogs we encounter. As an aside, I love watching his calming signals, they're subtle but incredibly effective--he does not want confrontation for the most part.
His barrier issues are traced back to a dachshund we used to share a fenceline with...evil EVIL dog that would come charging full-bore out of his house, trash talking at the top of his lungs. We're making progess in getting Sawyer to quit being such a jerk behind a fence, but it's slow going, mainly because most people dont' want to let their dogs get anywhere near the "vicious" dog. If it's a dog he knows well, there's no issue. It's only strange dogs.
Virgo...is a Lab. A pretty dominent Lab (I hesitate to use this label b/c of it's overuse, but I truely think it applies)...anyway her greeting is to approach a dog head-on until the last second and then present her side or veer for the "half-circle sniff-fest". If we're on lead, she raises Cain with barking and half-howls and attempts to drag me over to the other dog so she can sniff noses and walk off like the other dog doesn't exist. Off-lead, same behavior, only totally silent (and no jumping around like a spaz). I dislike taking her to Petsmart at the moment because she does get very loud and looks out of control, which is not something I like to see and I know it presents the both of us in a bad light (and I"m sure we've been forum fodder somewhere...). Her barrier reactions aren't near as active as Sawyer's, though if he's there, she feeds off of him and will raise a fuss as well. Usually though, she limits herself to barking a couple times in an "Hey, I see you!" way and following the other dog along the fence line, sniffing along the way.
Sorry for the novel and I know that none of you have seen my dogs before, but do these sound like "reactiveness"?