In addition to the studies of canine personality, there has been some research to determine whether there are breed differences in aggression. In a study published in 2008, aggression was divided into four categories: aggression directed at strangers, owner, strange dogs, and rivalry with other household dogs. This study found that the Doberman Pinscher ranked relatively high on stranger-directed aggression, but extremely low on owner-directed aggression. The Doberman Pinscher ranked as average on dog-directed aggression and dog rivalry. Looking only at bites and attempted bites, Doberman Pinschers rank as far less aggressive towards humans and show less aggression than many breeds without a reputation (e.g., Cocker Spaniel, Dalmatian, and Great Dane). This study concluded that aggression has a genetic basis, that the Dobermann shows a distinctive pattern of aggression depending on the situation and that contemporary Doberman Pinschers are not an aggressive breed overall. In regards to Dobermanns attacking owners, it is rare and usually in the case of overdiscipline. Dobermanns accept physical punishment to an extent. However, when they consider it to no longer be punishment, but an attack on themselves, they will defend themselves.