I am surprised at how many responses are given here that are based on nothing more than misinformation and personal opinions rather than fact, given that this is a forum dedicated to science.
First off, I would like to say that I have been in contact with more pit bulls than I can ever count. Literally, it is probably over a couple of hundred. I have never been bitten. Coincidence? I think not.
To start off, I would like to speak of the reliabilty of the ATTS regarding temperment testing. Have any of you ever heard of getting your dog temperment tested and certified for the testing? It is a common practice among reputable breeders and responsible owners. The ATTS is THE place to get this done. If you hear of someone whom is taking their dog to get temperement tested, it was done by the ATTS. If you look at the http://www.atts.org website, you will see that several thousand dogs have been tested by this organization. This is obviously a large organization that is respected in this field. As you can see, the APBT ranks higher than many of your favorite breeds including the Border Collie, Cocker Spaniel, German Shepherd, and the Golden Retriever.
As mentioned before and as proven by the poll, most people have not been in contact with an APBT and most people do not know what they look like. Do me a favor and picture in your head, how much do you perceive these dogs as weighing? What do you think they look like? I'll give you a second.
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Now look at this site:
http://www.pitbullsontheweb.com/petbull/findpit.html
and this one:
http://www.coldsteelpits.com/coldsteelfindthepitbull.htm
How did you do?
The fact is, they are relatively small to medium sized dogs. They are not big or overly muscled. The average size for a male is around 40-55 lbs for a purebred male APBT. These are dogs that are within standard and stand the best chance of winning at a conformation show that adheres to the original standard.
However, this is not how the public perceives these dogs. Any dog that is short-haired and muscular can become a pit bull. Fueled by media hysteria, any person that is bitten by any short-haired muscular dog will automatically assume and call the dog a "pit bull". It can be mixed with any range of breeds but it can be lumped into this category.
For those that mention documents or so-called reliable news articles that say that the dog was full-blooded, how can you be sure? Even with papers, the dog can be mixed.
The Pit Bull is extremely popular and unfortunately it is increasingly popular with the wrong crowds thanks to antics from those such as Michael Vick. This increases the population of the breed within the country and also increases the potential of the breeding of dangerous dogs. These dogs are not a true representation of the breed but rather a by-product of appeal to unsavorable owners which breed these dogs for the wrong reasons and then turn around and sell them to other people with less-than-honest motives.
There is also the fact that there is an absolute hysteria regarding these dogs. People automatically assume that any short-haired muscular dog is automatically a "Pit Bull" when it could be any range of mixes.
I have personally owned a Labrador and Pit Bull mix and he looked pure-bred to every person I have met. A Presa Canerio, which is also growing in popularity for the wrong reasons can easily be confused with an APBT. Virtually, any short-haired breed including American Bulldogs (which are also very popular) can be confused with this breed. If someone is attacked by one of these short-haired muscular dogs or a mix of the such, guess what? They won't be calling the dog by the actual breed, they will say the breed that the media has taught them to associate this behavior with.
Unfortunately, this has caused me to fear for my dog's life. I can't leave my dog outside without supervision for fear of being poisoned. I can't own a treadmill like hundreds of people who own dogs other than Pit Bulls for fear that I will be arrested for training a dog to fight. I have to fear the fact that the breed I have always owned and loved will be banned and forced into euthanasia because of misinformation.
Please, don't believe all of the things you hear. Don't believe that every dog that is associated with these attacks are indeed pure bred APBTs or APBTs at all. There is a lot of misinformation regarding this breed and I would hope that a science-dedicated forum would rely more on fact and reason.