It is hard to love a dog who has bitten you, or your child, or a visiting friend. A number of studies have shown that aggression in a pet dog is one of the top three reasons for getting rid of it. Aggressive dogs are difficult to rehabilitate and dangerous to keep around so they are often relinquished to a shelter or euthanized. The levels of aggression seen in dogs can be shown to be related to genetic factors such as the dog's breed (for example several studies have shown that Golden Retrievers are remarkably low in aggression) or the dog's sex (male dogs have been consistently shown to be more aggressive than female dogs). However, recently researchers have started to look for things associated with the dog's environment, or factors associated with the way in which the dog's owners treat or interact with the dog that might increase or decrease aggression. From such research we have already learned that certain methods of obedience training, namely those based on force and punishment, can trigger aggressive responses in dogs (click here for an example).
I recently came across a report published in the journal Applied Animal Behaviour Science* which provides some interesting insight into why some dogs become aggressive. The study was conducted by Yuying Hsu and Liching Sun at the Department of Life Science at the National Taiwan Normal University. These researchers were motivated to study dog aggression because in Taiwan dog bites have become a major public health issue. There are many concerns and much discussion about aggressive household dogs who have attacked owners, visitors, and other dogs. Because much of the Taiwanese population does not approve of euthanizing unwanted dogs, many of them are released onto the streets thus exposing pedestrians to the danger of being harassed or attacked. In fact in one large telephone survey 17% of the population of Taiwan indicated that they or their family members had been bitten by a dog at least once within the last 12 months. So the researchers were motivated to identify aspects of the dog's environment, or the way in which their owners interacted with them, which might lead to recommendations on how to reduce the amount of aggression seen in pet dogs in their country.
To measure aggression in dogs these investigators chose to use the Canine Behavioral Assessment and Research Questionnaire (C-BARQ) which is a long (103 question) survey instrument that gets dog owners to rate various aspects of their dog's behavior. This questionnaire was developed in the laboratory of James Serpell at the University of Pennsylvania and has been shown to be a reliable way of measuring the temperament of dogs, including levels of aggression. For the current study the questionnaire was translated into Chinese and additional items were added to determine the dog's living conditions and the nature of interactions between the dog and its owner. Dog owners were recruited in animal clinics, parks, dog shows and even in the street in areas all over Taiwan. In the end data was obtained for 852 dogs and their owners.
This is another one of those scientific reports that involves a lot of complex statistical computations (including logistic and regression analyses), which makes it difficult for people without scientific and statistical training to interpret. So for that reason I will simplify our discussion and stick with the main findings that that address the issue of aggression shown by pet dogs. One important result was that as in previous research, this data confirmed that canine aggression is not a single unified characteristic. We can break it up into three different types of aggression, namely aggression directed toward strangers, aggression directed at the dog's owner (or family), and aggression directed toward other dogs. This study showed, like others before it, that individual dogs can be high on one of these forms of aggression, but not necessarily on the others.
While some of the findings in this study confirm results from other research (for example the finding that male dogs are more likely to be aggressive than female dogs) the most powerful and important finding to come out of this new array of analyses has to do with punishment. What happens when a dog is physically punished for misbehaviors? Here the results are impressive and unambiguous, specifically, the more frequently a dog is punished the higher the likelihood that the dog will be aggressive. Furthermore, the increased aggression that the dog shows spans the full range of aggressive responses, making it more likely that the dog will aggressive against strangers, its owner or family, and other dogs. The interesting thing here is that we are dealing with punishment being applied for simple everyday forms of misbehavior. Thus if our pet dog comes too close to something which we are eating and looks like he might try to snatch a piece of it, we might choose to correct this intrusive behavior by giving him a slap with our hand. These current finding suggest that by using this physical intervention we have now increased the likelihood that in some future confrontation our dog will respond to us by trying to bite our hand, or our child, or a friend that we have invited into our home, or a dog that he meets on the street.
To someone who is aware of the research done on humans concerning the effects of punishment these results will not be surprising. In 2008 a report was published by the American Psychological Association's Task Force on Physical Punishment of Children. As part of this report Elizabeth Gershoff at the University of Texas at Austin, presented an analysis of 27 different studies that looked at the effect of physical punishment on the later behavior of children. The results were astonishing in their uniformity — every single one of these research reports found that physical punishment was associated with increased aggressive behaviors by the punished children. Combine these findings with the fact that a number of researchers believe that the mind of the dog works in a manner which is very similar to the mind of a 2 to 3-year-old human child, this would clearly lead us to suspect that similar results would be found in dogs, and that has been confirmed by this research from Taiwan.
The obvious conclusion to draw from looking at this research on dogs and the research on humans is that if we want an easy way of reducing the likelihood of aggression in our pet dogs, we should reduce the amount of physical punishment that we apply to them in our daily interactions.
Stanley Coren is the author of many books including: The Wisdom of Dogs; Do Dogs Dream? Born to Bark; The Modern Dog; Why Do Dogs Have Wet Noses? The Pawprints of History; How Dogs Think; How To Speak Dog; Why We Love the Dogs We Do; What Do Dogs Know? The Intelligence of Dogs; Why Does My Dog Act That Way? Understanding Dogs for Dummies; Sleep Thieves; The Left-hander Syndrome
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Data from: Yuying Hsu and Liching Sun (2010). Factors associated with aggressive responses in pet dogs. Applied Animal Behaviour Science 123, 108–123