If Pit Bulls have been bred for generations not to bite people, why is it that we seem to hear so many gruesome accounts of Pit Bull attacks? One reason is that stories about aggressive Pit Bulls are more sensational than stories about equally aggressive dogs from a breed with a more benign reputation. The media is far more likely to report on a problem Pit Bull than a problem Golden Retriever. Also, greater public awareness of Pit Bulls has increased the likelihood that any muscular, short-coated dog with a large head will be identified as a Pit Bull, particularly if it has been involved in an attack.
But claims of media bias cannot be used to explain away the times when Pit Bulls have truly bitten, sometimes with tragic consequences. The fact that dogs described as Pit Bulls are responsible for more than their fair share of human bites (particularly those that result in the worst injuries) can’t be ignored.1,2,3 What has gone wrong in these instances?
In some cases, breeders need to take responsibility for producing vicious dogs. Conscientious breeders carefully select only the best individuals for use in their programs and routinely produce wonderful animals. But, if someone instead seeks out Pit Bulls that act aggressively towards people and mates them to each other or to any other aggressive dog, years of proper breeding can be undone in just a generation or two.
Many times, owners are to blame. Pit Bulls are extremely trainable and want nothing more than to please their owners. Unfortunately, if an immoral person wants their Pit Bull to be aggressive towards people and he or she rewards this behavior, the dog is likely to act in the way that his owner has intended. Also, dogs that have been neglected, abused or poorly socialized are more likely to be aggressive. If a Pit Bull has had only unpleasant dealings with people or has no experience with strangers, it should not come as too great of a surprise when he lashes out.
Studies published in 2009 and 2012 confirm that owners of dog breeds known for being “vicious” (including Pit Bulls) have higher incidences of criminal thinking and behavior, primary psychopathy, and antisocial tendencies in comparison to other dog owners.4,5 It seems obvious that certain breeds of dogs attract certain types of people, and if those owners act in aggressive ways it shouldn’t be too surprising that they train their dogs to behave in a similar manner.
Finally, sometimes the process of reproduction, development, and aging goes astray. In a particular dog, genes may combine in just the wrong way producing an individual that is very different from what is normal. Although the majority of Pit Bulls are born gentle and trustworthy, a specific individual may not be. Diseases or injuries that cause pain or adversely affect brain function may also be responsible for turning a good dog, regardless of its breed, into a potential threat.
http://www.petmd.com/blogs/fullyvetted/2013/june/truth-about-pit-bulls-part-three-30423