Several dog breeds have a reputation for being dangerous, like American pit bulls, Rottweilers or Doberman Pinschers. Many landlords prohibit tenants from owning such "junk-yard dogs" because, according to popular belief anyway, these dogs have a propensity to be aggressive.
However, according to the ASPCA, there is "no credible evidence that breed determines or predicts dangerousness." Instead, aggression in dogs is most often linked to a lack of proper training and socialization, animal cruelty or encouragement on the part of their owners to act aggressively. Any dog of any size can attack someone, especially if it is provoked or feels threatened. As pack animals, dogs may also react negatively to someone they feel threatens their owner, or "pack leader."