Aggression can show itself in several ways. The most common things I hear from my clients are that their dog lunges at people and other dogs when they are walking on leash. And their dog growls or barks incessantly at people that come to their home. Both issues are usually fear based and can be resolved by the human learning to be a better pack leader. These type behaviors are caused when a dog is uncertain, anxious and doesn’t know what is expected from him. He therefore acts aggressively toward others as a self- protection mode based out of fear.