According to veterinary behavior specialists Ilana Reisner, DVM, PhD, DACVB and Stephanie Schwartz, MS, DVM, DACVB, contributing authors of the book "Decoding Your Dog," fear-related aggression is used as self-defense and may be the last resort for dogs who can't escape or used when they anticipate a threat. If they can't escape some dogs may display appeasing body language signals to diffuse threats like lip licking, not making eye contact, turning the head, rolling over onto the back and even urinating on themselves. If the threat is still present a dog's body stiffens, growling occurs, teeth are bared or biting may take place. When people routinely use their hands to hit dogs, they may cause them to become "hand shy." These dogs may eventually generalize that whenever any human hand reaches out to touch them, they may try to avoid it or resort to self-protection by biting. Human hands should be associated with pleasant dog-human interaction like petting, cuddling and dispensing treats.