Those are PIT bull terrier, Not a bull terrier. The target dog is a bull terrier.
I know the difference.
"Early in the mid-19th century the "
Bull and Terrier" breeds were developed to satisfy the needs for
vermin control and animal-based
blood sports. The "Bull and Terriers" were based on the
Old English Bulldog and one or more of
Old English Terrier (now extinct) and "Black and tan terrier", now known as
Manchester Terrier. This new breed combined the speed and dexterity of lightly built terriers with the dour tenacity of the Bulldog, which was a poor performer in most combat situations, having been bred almost exclusively for fighting bulls and bears tied to a post. Many breeders began to breed bulldogs with terriers, arguing that such a mixture enhances the quality of fighting." -https://en.wikipedia.org/wiki/Bull_Terrier
http://www.bulldoginformation.com/bull-terrier.html
Vermin and fighting. Not saying they are bad dogs, Pitbulls are great dogs and were bred for questionable reasons over the years. English bulldogs, too were initially bred to battle bulls. My point is if we all understand the history and purpose of the breeds initially, we can understand their behavior.
For instance, my breed, Shetland Sheepdogs are yappy and run in circles a lot. My dogs are not yappy because I do not allow it, but this is because as smaller herding dogs, they are excitable and use barking to command respect from the livestock, let their owners know where they are when out of sight, etc. They run in circles and get in to mischief a lot if not exercised or challenged because they were bred to herd animals (herding is a big circle) and they have very strong instincts to do this.
This does not mean that they MUST ALL be yappy or spin a lot, but it is a natural tendency. Terriers destroy vermin, that is what they were bred to do. Labs love to swim, because they're retrievers of waterfowl.
