MarnaLou,
I would find a chat place for St. Bernards on the web. I think that I recall that as a behavior issue for this breed. I had a very agressive little terrier as well as an Alpha Lhasa Apso and was doing research on agression several years ago. The breed discussions were very helpful to me. The little terrier turned out to have seizures and the Lhasa also had an organic issue from taking Prednisalone for Crohn's disease.
