Aggression, for example, is very highly heritable in Golden Retrievers, with a heritability for aggression by dogs towards strangers of 0.9. This heritability score of 0.9 indicates that 90% of any observed difference between Golden Retrievers in the aggression they show towards strangers has been inherited from their parents, and just 10% can be attributed to other factors such as experience and environment.
And studies that span several breeds (Liinamo et al. 2007) show that aggression is largely determined by genes in most dogs. An interesting finding that is important to our quest of choosing a dog to be your Perfect Match Puppy is that aggression towards people is a distinctly separate genetic trait that bears little correlation to canine aggression towards other dogs. The heritability score for aggression directed to humans is pretty high, at 0.77 and that for dog-directed aggression is even higher at 0.81.
This means that a dog that is highly hostile towards other dogs might be quite safe when it comes to people. On the other hand it also means that you can’t do much to steer a puppy away from developing into an aggressive dog if it has been genetically coded to develop this trait.
Liinamo and his collegues found high heritability estimates on several aspects of aggression such as strange dog approaching leashed dog (0.85), family member grooming dog (0.83), family member approaching eating dog (0.94), family member removing food (0.95), stranger trying to touch dog (0.99). Simply put, dominance behavior and aggression appear to be quite firmly under genetic control.