A Quick Assessment Tool for Human-Directed Aggression in Pet Dogs

Article Summary: Klausz, B., Kis, A., Persa, E., Miklosi, A., & Gacsi, M. (2014). A Quick Assessment Tool for Human-Directed Aggression in Pet Dogs. Aggressive Behavior, 40, 178-188.

Stranger-directed aggression is among the most common behavior problems exhibited by pet dogs. Although several assessment protocols have been designed to assess canine aggression, many involve multiple testing scenarios presented sequentially to the dog. Lengthy and repeated exposure to provocative testing stimuli might reasonably be expected to be stressful for dogs and is also time-consuming for testers. Furthermore, order effects might be expected to develop over repeated testing, and may influence dogs' responses either in the direction of increasing aggression across tests (through processes of sensitization or negative reinforcement) or decreasing aggression across tests (through processes of habituation or extinction). In a recent study published in the journal Aggressive Behavior, Klausz et al. (2014) set out to develop a brief set of test conditions for stranger-directed aggression that might be relatively quick and easy to implement while also accurately identifying aggression in those dogs with a known aggression history.

Klausz et al. assessed 73 pet dogs' aggression toward an unknown experimenter during a series of 5 brief tests. Dogs were selected for study based in part on their bite history (as reported by owners) and were divided into three groups – those with one bite in their history, those with multiple bites, and those with no bites. The groups were similar in age, sex, and breed representation. For Tests 1 through 4, the dog was tethered between two trees with room to move forward and backward (so avoidance of the experimenter was always an option). The owner stood 1 meter from the dog with no interaction with the dog.

Test 1 was a Friendly Greeting test that involved the experimenter approaching the dog at a normal pace while talking in a friendly way and maintaining eye contact. At 1 meter,  she stopped and called the dog to her. If the dog approached without aggression, she moved closer and petted the dog's head with an artificial plaster testing hand. If the dog exhibited aggression, the experimenter remained outside of tether range and simply repeated the dog's name for 30 seconds. Dogs with no bite history showed no aggression in this test. Two dogs with a one-bite history and one dog with a multiple-bite history growled in this test, and two others with a multiple-bite history attacked the experimenter in this test (see p. 181 of the original paper for response definitions). Those dogs who exhibited aggression in this test also exhibited aggression in most subsequent tests. 

Test 2 was a Take Away Bone test, in which the experimenter first petted the dog's head after 5 seconds of its chewing the bone, then she reached toward the bone, put her hand on it while saying “Give it to me!” and slid it away (using the artificial test hand). Dogs with a multiple-bite history were significantly more likely to exhibit aggression in this test than were dogs with a one-bite or no-bite history.

Test 3 was a Threatening Approach test in which the experimenter approached slowly while leaning forward and staring directly at the dog. Dogs with both a one-bite or a multiple-bite history were significantly more likely to exhibit aggression in this test than dogs with no bite history.

Test 4 was a Tug of War test in which the dog was given a rag which was then tugged (when the dog engaged in tugging) and then taken away by pulling. Very few dogs showed aggression during this test, and there was no difference between groups.

Test 5 was a Roll Over test in which the dog was gently made to roll onto its back by its owner, who then tried to hold the dog in place for 1 minute. Only four dogs showed any aggression toward their owner during this test, and there was no difference between groups in the latency with which owners were able to get their dogs onto their backs.

The authors conclude that the Friendly Greeting test, although it produced little to no aggression across all dogs, was a good predictor of aggression in subsequent tests and could thus be used as an initial indicator, revealing consistency in aggression or more easily provoked aggression. The Take Away Bone test might serve well to reveal those dogs with a history of repeated aggression. We might suppose some dogs with a multiple bite history have rehearsed this type of aggression (and received reinforcement for it) in the past. A tendency to guard valuable resources is exhibited by a variety of social species. In many households, a pet dog's aggression over a food resource is negatively reinforced when it chases away or prevents further approach by a conspecific or human family member. The Threatening Approach test similarly evoked aggression in those dogs with a bite history and might serve as a reliable indicator of a dog's tendency toward aggression in more provocative, ambiguous situations (i.e., the experimenter had approached before and had been friendly, but was now approaching with threatening body posture and no verbal greeting). Here as well, a dog's learning history is likely to play a significant role in determining its behavior. Specifically, dogs whose aggressive responses have resulted in the freezing or the retreat of an approaching stranger are often more likely to use aggression in other similar situations across time.

The Tug of War test was not helpful in distinguishing between dogs with and without a bite history, supporting previous research that has demonstrated no link between competitive games of tug of war and aggression or dominance behavior. It was hypothesized that the Roll Over test might reveal aggression toward owners in those dogs with a bite history because it is a potentially stressful maneuver, yet only four dogs exhibited any aggression during this test and results were not correlated with a dog's bite history.       

Although they acknowledge that there are other situations in which stranger-directed aggression could or should be addressed (e.g., on the dog's home territory), Klausz et al. suggest that the first three tests assessed here (Friendly Greeting, Take Away Bone, and Threatening Approach) could be useful in revealing dogs with a history of stranger-directed aggression. Importantly for both practical and animal welfare purposes, these three tests can be conducted in just a few minutes. When combined with a thorough physical examination and a behavioral history interview that includes a complete analysis of past and present antecedents and consequences for aggression, assessment tests such as these might provide the animal behaviorist or veterinary behaviorist with an efficient and systematic way to gather information about the likelihood of aggression under approach and resource conflict conditions. 

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