No more or less temeramental than any other dog! It doesn't tell you much, but the fact is that dogs are individuals, and no species is necessarily more passive, or more aggressive, than any other. The factor to take into account is potential damage. If a fox terrier decides to have a bit of a bad day, it may be no big deal, but if a doberman decides to show its nasty side, you have problems, because they are big strong animals, with jaws that lock together, and a tendency not to unlock them until they feel like it, which they don't until unconciousness or death intervenes! Dogs are pack animals, so if you train your pup to learn its place in the pack, you are OK, but never forget, the most passive of dogs can turn one day, and in the case of the larger species like dobermans, you have to be ready to deal with it. That said, they make excellent companions and serioulsy good guard dogs - when they protect you, you stay protected! If you are planing to get a pup, train it well, and you'll enjoy a good relatiopnship.