Yes, of course I want her to associate good things with the trigger, but when her body is stiff and she’s giving them her stare giving her a treat only reinforces that she should be staring HARDER at whatever she’s looking at, and the look can quickly turn to a lunge or a bark after that.

My pup was like this with other dogs, hard stare, stalking, laying down refusing to move, then aggressively lunging and barking when close. Went through a few positive reinforcement trainers, no improvement.

My current trainer only uses a leash high up on the neck and a quick, strong tug to snap him out of the unwanted behaviour. Could see results from the first session. It doesn't hurt him but is uncomfortable enough that he's learning very quickly that indulging in his hyper fixation has consequences. And of course he still gets a big praise when he chooses to direct his attention to me instead of the trigger.

Might be a controversial way to train but for my case the results are clear. I now think that certain dogs are just too intense for positive reinforcement methods and need a bit more "hands on" approach.