There are risk factors that can help predict whether a dog will be dangerous and that has nothing to do with what breed the dog looks like. This is important information for us in crafting laws to protect us from dangerous dogs.
One of the biggest factors that Karen Delise outlines in her book is whether of not the dog is a "resident" dog or "family" dog. "Resident" dogs are usually acquired for breeding or security purposes. They are not part of a family, are kept isolated from others, and do not learn how to bond with people. Usually these dogs are kept outside in a small enclosure or on a chain.
Here is a listing of the risk factors:
Dogs kept on chains (illegal in Austin)
Loose roaming dogs (especially in packs)
Dogs around unsupervised children
At the No More Homeless Pets conference this year, I heard from Bill Bruce, the head of animal control in Calgary, who is leading the way in pet welfare and no kill programs.
They have been gathering detailed data on dog bites and will be publishing their results around summer 2010. While the report is not ready, he told us that the data clearly shows that breed (or what the dogs looks like) plays no part in the chances of aggression. Instead, they're finding that how early and often the dog has been subjected to violence (including corporal punishment) is a strong predictor of aggression. I look forward to seeing the whole report and will include a link to it when it's published.
As a footnote, I want to take this opportunity to report what the chances are of being killed or seriously injured by a dog bite. In Texas, 2 people per year are killed by a dog on average. In 2005:
3 people were killed by dogs
5 people were killed by lightning
12 people were killed after contact with bees, hornets, or wasps
61 people were killed on their bikes
3,536 were killed in automobiles
In 2006, statistics were kept on causes for hospitalization of children at Texas Children's Hospital in Houston. Here's how dog bites compared to spider and snake bites: