As this discussion shows dog training is pretty easy to understand but at times is very difficult to put into practice.
Fact
Positive reinforcement works
Aversive training works
Aversive training will have more fallout and will effect the relationship between dog and trainer/owner
Rewards are not reinforcement. They may be in some cases for some dogs but not all dogs.
People rely too much on operant conditioning than classical conditioning.
Operant will always give a dog a choice and the reinforcement has to be high
Classiscal conditioning with gun dogs if the breeder blows the whistle from week 3 or as soon as the puppies can hear when the puppies are suckling on the bitch and do so at every meal time you will have a dog classical conditioned to a whistle and will very very rarely have recall issues.
If the breeder from about 5 weeks when the puppies are moving lures a sit everytime the dog hears a bird (can move it onto scent very quickly after this) the gundog will sit and wait for a command when seeing or smelling a bird. Most good breeders should be doing this.
Also re toilet training all puppies will move to a specific spot to wee when they are very little - as soon as they are moving. If a breeder encourages this and keeps the area clean the puppies will be pretty much toilet trained eg no there is a specific area to toilet by the time they leave the breeders.
If you have a gundog from 8 weeks and always cue the sit when they see movement your prey dog will sit before chasing.
If you work on operant conditioning then the reinforcement for chasing will have to be good. The dog wants to chase so if you just recall, offer food, no way will they see that as reinforcing. However If you recall and run in the opposite direction with a tug toy the dog will find this more reinforcing and will feed into the predatory motor pattern and you will have more success.
Timing reinforcement rate, value is extremely important. This is why many people resort to aversives as they are not able to correctly offer positive reinforcement on all dogs.
Re interrupting a dog as they are about to do somthing. A positive interrupter is really powerful. Have a sound I make a kissy noise everytime I do it the dogs get a treat or something fun happens. if they are about to do something I do not want them to do the positive interrupter will move them on from what they were about to do. No shouting, no aversives but success if preventing the behaviour.
I dont teach a leave it. I have good recall, a good stop command, a wait command a solid down positive interrupter so all behaviours that will prevent the dog doing what I want them to leave without yelling leave it at the dog.