Here's the deal with motion fixation. Herding dogs have been bred for generations to watch movement of whatever they are herding, they have to be able to pinpoint that rogue sheep who is about to dart away from the mob and they have to be constantly aware of the direction/speed/body language of the stock. Not only that, but they have a very specialized version of prey drive that makes them chase automatically. For some dogs this isn't a big deal, working with their handler automatically outweighs the reward of watching movement. However, for a lot of dogs, that drive to herd is far more rewarding than anything else in the world.
Instinct really is a big part of this, however it's hardly the only thing. A dog with instinct to herd but no chance to practice it will most likely not develop as much of an obsession as a dog that is allowed to practice the behavior repeatedly. Think reinforcement history here. The more times we reward the dog for coming when called, the more enthusiastic their recall will be. The more times a dog is allowed to fixate on other dogs (whether or not they are allowed to actually chase), they more times they are being rewarded (it's FUN to fixate!) and the more enthusiastic their fixation will become. By putting the dog in a situation where they are allowed to fixate, all you are doing is building drive for that behavior. Lesson here: Set the dog up for success.
The other part of this is the handler/dog relationship and the drive/desire to preform the task being asked of them in place of fixating. This is a pretty educated forum, everyone pretty much knows (if they are reading this thread anyways) that in order to stop a dog from doing an unwanted behavior, you should give them something else to do. That something else needs to be rewarding in itself for the dog. Build drive for your replacement behavior before trying it around a moving dog.
Impulse control is another factor in this. A dog with little impulse control will have a difficult time staying engaged with their handler when another dog is running. Susan Garrett's Crate Games is a great way to improve impulse control and is honestly one of the first things I do with a new dog. I work on this independently at first but as quickly as I can, I incorporate it into training sessions with all of the dogs. What I mean is, I have one dog stay in their crate with the door open while I'm working another dog. This teaches them that even though I am playing with another dog, they need to stay focused on their task.
Here's a video of what I mean:
[YOUTUBE]mqZ_Wt6ZcR8[/YOUTUBE]
If at any time Zuma leaves the crate, Crate Games rules are in effect. The door gets shut to reset her and then opened again. I like this more than "spot" training for new dogs/puppies because it has the consequence of the door shutting if they make an error, it's black and white versus the abstract boundaries of a spot. However, I do work "spots" (exercise ball, on top of the crate, cat tree, perch, etc) once they have this concept.
At this same time, I'm building tug drive and handler focus. We do mini-play sessions inside where my main focus is on the puppy but I slowly increase other dog play as well. Eventually working up to what Linds' is doing with Didgie right now.
Here is a video of one of our beginning play sessions inside. I am mostly tugging with Zinga and throwing for Zuma at the same time. I'm setting her up for success, it's hard to focus on Zuma while she's tugging. I also have a rule that each dog can only play with their toy. If at any point they steal the other dog's toy, play stops until we get it situated out again.
[YOUTUBE]4ybD7ekB0xU[/YOUTUBE]
At this point, Zinga has very little dog focus when she's working. She will still stalk/chase Zuma in the backyard when they are playing but it is not an obsessive thing and very much a relaxed play. I can play disc with both dogs at the same time and not have to worry about potential injuries because they each go for their own discs. I'll try to get an updated video sometime of a two dog disc session.
So really, it's a very avoidable problem if you watch for it early. The above things are what I do normally for new dogs, so it just never developed into a problem even though Zinga was very much interested in motion as a puppy.
ETA: apparently I need to not wear scrubs so much. :rofl1: