When a dog misbehaves, we commonly blame the dog. However, most unwanted dog behaviors come from us, rather than from our dogs.
Dogs are not born mean. In fact, bad dog behaviors usually occur when we mis-communicate with our dogs and unknowingly reward bad behaviors. If a dog consistently gets bad results for a given behavior, he will stop that behavior. However if a dog consistently gets positive reinforcement for a given behavior, they will increase the frequency of that behavior.