Common sense says pit bulls are aggressive by nature. Pit bull attacks against humans make the news for their often tragic results.
A 2008 study conducted at the University of Pennsylvania analyzing thousands of dogs from 33 breeds found that pit bulls were easily topped by none other than wiener dogs -- er, dachshunds -- in terms of bite attacks against people. Of the dachshunds in the study, 20 percent had bitten or attempted to bite strangers, and 6 percent had bitten or attempted to bite their owners, compared to 7 percent and 2 percent, respectively, of the pit bulls. Chihuahuas, Jack Russells and beagles also beat out pit bulls for aggression toward people [source: Duffy, Hsu and Serpell].
Pit bulls did score high in aggressiveness toward other dogs; dachshunds did, too. But combined aggression toward humans and dogs earned wiener dogs the top spot for overall aggression [source: Dobson].