"Vicious" is one of the first misconceptions that comes to mind when people think "pit bull." Consequently, this label has made it infinitely more difficult for some dogs to find a home. What's worse is shelter workers often mistakenly identify dogs as pit bulls, further reducing their chances of being adopted.

New research from Arizona State University revealed that dogs labeled as "pit bulls" wait three times as long to be adopted from shelters than differently labeled look-alikes. Although studies in the past have found that certain types of dogs take longer to be adopted from shelters, it was not until recently that scientists looked into how much breed identification really influences adoption decisions.

"We were surprised how very similar looking dogs sometimes get labeled 'pit bull' and other times as something completely different. These dogs may look and act the same, but the pit bull label damns them to a much longer wait to adoption," explained Lisa Gunter, lead author of the study.

"Pit bull" is not actually a breed, but rather a term applied to dogs derived from the heritage breeds American Staffordshire terrier or Staffordshire bull terrier. The purebred American pit bull terrier is also derived from these breeds and is often included in the loose definition of "pit bull."

For the most part, pit bulls are just mutts that happen to have an intimidating, blocky-shaped head. And there is no evidence that they are any more dangerous than other dog breeds. Nonetheless, pit bulls are often negatively perceived. In fact, it is believed that only one in 600 dogs labeled as being a pit bull are adopted. In the U.S. alone, approximately 800,000 of the dogs are euthanized each year.

Gunter and colleagues Rebecca Barber and Clive Wynne conducted four studies in which they investigated the powerful impact labeling has on people, even if the labels are incorrect. For the first test they examined how test subjects recruited from psychology classes at Foothill College perceived the attractiveness of three dog breeds: Labrador retriever, pit bull and Border collie. Overall, researchers found that pit bulls received the lowest ratings in perceived approachability, intelligence, friendliness and adoptability, and the highest in aggressiveness and "difficulty to train."

Researchers then examined the influence of breed labeling on length of a dog's stay in a shelter. To do this, they compared the fates of dogs labeled "pit bulls" versus those that were look-alikes, but carried another type of label, such as "boxer."

For the third study, potential adopters viewed pit bull-type dogs and look-alikes in videos with and without breed labels to assess the effect those labels had on perceived attractiveness. Then, in the fourth and final experiment, scientists collected data from a shelter both before and after breed assignments were noted on kennel cards and online adoption profiles.

Researchers found that pit bulls were perceived as less adoptable than other breeds, such as labradors, and considered less friendly and more aggressive overall. Compared to look-alikes unlabeled or labeled as other breeds, pit bulls were again seen as less 'attractive' and waited more than three times as long to be adopted.

Therefore, researchers suggest that removing breed labels could be an easy way to improve the experience of pit bull type dogs in animal shelters.

The study was recently published in the journal PLOS ONE.