Kristen,
The subject of dog aggression comes up regularly on almost all boards concerning dogs! It's a common problem and has a genetic component, so it's not something you're going to just correct out of the dog. The best you can do is to train your dog (through obedience) to ignore another dog.
The info was posted first elsewhere; hope it will be helpful to you...
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A dominant dog will use dog aggression to show his rank to other dogs.
A fearful dog will use dog aggression to warn off other dogs.
In either case it's a headache for the owner.
However, be aware that corrections or jerking the dog away generally are counter productive.
1) a dominant dog will simply load up more (my leader is getting excited too, so I better crank it up a notch!)
2) a fearful dog will become more fearful (my leader is not helping me scare them off...I better crank it up a notch!)
A really strong correction may immediately stop the aggression for that moment in time but it can also teach the dog to “mask” his pre-aggressing signs so that afer a couple of times, he will cover up ALL of the humanly readable precursors to his inappropriate aggression.
When that happens you will have a bigger problem on hand because you will not be able to react proactively to prevent such aggression.
FYI: the canine precursors to dog aggression are:
1) stillness,
2) ears forward,
3) closing of the mouth,
4) staring (locking on!)
5) barking/lunging.
These can all happen very quickly, and a handler must start taking action no later than number 3...which requires keeping an eye on the dog at all times during a relearning session, rather then socializing with other humans....
There are Operant Conditioning solutions to dog aggression, based on the same principals as developed for training marine mammals:
1) Ignore the bad behavior (DO NOT reinforce it with ANY action) and
2) Elicit and reward "other" behaviors that are more appropriate at that moment.
(Based on learning principals that behavior reinforced will continue, behavior ignored will diminish.)
The key to teaching a new learned behavior to dog aggression is in "catching" your dog early in the pre-cursor signs: when Fido goes still, closes his mouth while staring at another dog...you react!! Get a different behavior that you can reward: heel away, a down command, or "look at me"...anything that you can reward right then with treats or praise.
This is not a fun routine. It's much more pleasurable to teach a dog a new trick, or some obed command...but without this new learned behavior, any new exercise will be hard to teach around other dogs.
This type of training will not "guarantee" that the dog will always show desired behavior and not aggression...but neither will any methods which use aversive control, ie, physical punishment. You have a better chance with O.C. And you, the owner, will be much better able to "read" your dog after this type of training has been successful, especially since the dog will not learn to mask any of the pre-cursors which lead up to the aggression.
And btw, this is not just theory...this training DOES work: our male dog is dominant, sharp, and very dog aggressive. He will never be an off-leash park dog, but he is trained enough now that he remains under control when we meet another on-leash male dog.