"Reactivity to Stimuli’ ’ Is a Temperamental Factor Contributing to Canine Aggression

Canine aggression is one of the most frequent problems in veterinary behavioral medicine, which in severe cases may result in relinquishment or euthanasia. As it is important to reveal underlying factors of aggression for both treatment and prevention, we recently developed a questionnaire on aggression and temperamental traits and found that ‘‘reactivity to stimuli’ ’ was associated with aggression toward owners, children, strangers, and other dogs of the Shiba Inu breed. In order to examine whether these associations were consistent in other breeds, we asked the owners of insured dogs of Anicom Insurance Inc. to complete our questionnaire. The top 17 contracted breeds were included. The questionnaire consisted of dogs ’ general information, four items related to aggression toward owners, children, strangers, and other dogs, and 20 other behavioral items. Aggression-related and behavioral items were rated on a five-point frequency scale. Valid responses (n = 5610) from owners of dogs aged 1 through 10 years were collected. Factor analyses on 18 behavioral items (response rate over 95%) extracted five largely consistent factors in 14 breeds: ‘‘sociability with humans,’ ’ ‘‘fear of sounds,’ ’ ‘‘chase proneness,’ ’ ‘‘reactivity to stimuli,’ ’ and ‘‘avoidance of aversive events.’ ’ By stepwise multiple regression analyses, using the Schwartz’s Bayesian information criterion (BIC) method with aggression points as objective variables and general information and temperamental factor points as explanatory variables, ‘‘reactivity to stimuli,’ ’ i.e., physical reactivity to sudden movement or sound at home, was shown to be significantly associated with owner-directed aggression in 1