Chip,
Check your Private Messages.

Maggie,
This pup is out of West German and Belgium lines. He has not been exposed to any defensive training in the bitework. I started developing his prey drive from the day I got him at 7 weeks, and he has very good prey drive, counters well and has a good grip. His drive in the obedience for the ball or tug is great. I worked him myself for a good while tying him out and working him on the tug. He'd come into drive very well, bit well, carried the prey, etc. It was when I began to introduce him to a helper that I saw tentativeness and a clue that this pup was not a prey happy dog and that he had some distrust of strangers.
Renee,
The decoy does not throw my pup into defense at all. He is working in prey and is becoming more comfortable each time he works, showing more confidence and commitment in the prey biting. There are situations that throw him into defense. Sometimes people approaching the vehicle when he's in it. He is at the fence aggressively when people walk by. Otherwise, his nerves seem good. I have not seen any overt nervousness, no raised hackles, noise sensitivity or problems with different surfaces, and his defensiveness has always been forward with no avoidance. What I meant by managing this aggression is not to directly set up scenarios such as the one where he is on the field and have someone pet him to see if he bites and then correct him. I think for now it's better to avoid those scenarios and see what happens with maturity and keeping the bitework in prey. Also, I need to be aware that having strangers approach this dog as I did in his early socialization is no longer going to be feasible.

Your dog may well BE a prey monster, but fear is blocking the expression of the prey drive. Since he shows excellent prey drive with YOU, and is tentative with a helper, you can safely assume that he does have strong prey, but that his fear overrides the prey (survival mechanism at work).

The only solution is to expose him to as many different people as possible, not to limit his exposure. He has to learn to play with LOTS of people, not just your one helper, unless you intend to only work and trial your dog at your own club. And every time you work him with a new person, you will see a decrement in the quality of work, but that's to be expected. It WILL get better if you continue to expose him to new people and set him up for success by always informing the helper of his issues and making sure the helper is the type that will react appropriately and find a way to make the dog feel strong and successful.

Lee,
Sounds like a good suggestion. I am having limited success finding access to skilled helpers, but will continue to explore my options. I suppose it's no different than putting the effort into tracking and doing obedience in a variety of locations.

Renee,
My concept of social aggression is a dog that expresses himself in a very dominant manner. While my pup isn't submissive and has challenged me some, I don't see him as a dominant dog. I would think the socially aggressive dog would try to establish his dominance over his own pack as well as outsiders. I am tending to see this behavior more as reactive aggression/defense/sharpness because the dog seems to be perceiving a threat and it is expressed more as fight as opposed to flight in the situations he has been exposed to. The behavior also seems to be linked to territoriality to some degree.
There are so many variables to consider in an individual dog's situation, and aggression seems very complex.
I will get feedback from the breeder. I wouldn't have expected this behavior from the breeding even though Crok is there 3 generations back. Neither of the parents had these aggression issues or are defensive dogs. My pup is bred 5-4 on Falko vom haus Sindern.