A dog has a psyche just like a person and it is everything. You can look at any sport today and see someone who was at the pinnacle of their career and they lost it. Not because of anything physically but because of everything mentally. For example, Miguel Cotto losing his psyche Vs. Margarito previously being an undefeated fighter, he was never the same after that night. I doubt Justin Verlander will ever be the same after game 1 of this past world series. It is all in the mind. IMO this can be a determining factor between a good dog and bad dog. You have a model line bred litter, the pups probably will be very genetically similar. Its not like there is one gene for gameness and some of the pups got it and some don't. Its more than likely the combination of many genes that help mold and develop the animals mind. It doesn't have to people Nature Vs. Nurture. A better solution would be Nature + Nurture for the better results.